Evolution

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Contents
Articles
Overview 1
Introduction to evolution 1
Evolution 16
Evolution as theory and fact 47
Evolutionary history of life 53
Timeline of evolution 83

History 92
History of evolutionary thought 92
Lamarckism 114
Saltationism 121
Orthogenesis 122
On the Origin of Species 126
Darwinism 154
The Genetical Theory of Natural Selection 158
Neo-Darwinism 160
Modern evolutionary synthesis 162

Base concepts 172

Heredity 172
Fitness 176
Common descent 179
Evidence of common descent 183

Mechanisms 212
Adaptation 212
Genetic drift 223
Gene flow 233
Mutation 236
Natural selection 246
Speciation 260

Phylogenetics 268
Phylogenetics 268
 Cladistics 274
Cladogram 284
Molecular phylogenetics 287

Fields 290
Evolutionary developmental biology 290
Molecular evolution 296
Human evolution 299
Evolutionary psychology 316

Controversy and social impacts 332

Creation–evolution controversy 332
Objections to evolution 359
Creationism 384
Intelligent design 406
Social effect of evolutionary theory 436

References
Article Sources and Contributors 444
Image Sources, Licenses and Contributors 454

Article Licenses
License 458
 1

Overview

Introduction to evolution

Artist's depiction of a T. rex.

Natural selection does not lead to perfection; dramatic changes in the environment often lead to mass extinctions, as in the case of the dinosaurs
nearly 65 million years ago.
Overview

Life forms reproduce to make offspring.

The offspring differs from the parent in minor random ways.

If the differences are helpful, the offspring is more likely to survive and reproduce.

This means that more offspring in the next generation will have the helpful difference.

These differences accumulate resulting in changes within the population.

Over time, populations branch off to become new species as they become geographically separated and genetically isolated.

This process is responsible for the many diverse life forms in the world today.

Haeckel's Paleontological Tree of Vertebrates (c. 1879).

The evolutionary history of species has been described as a "tree", with many branches arising from a single trunk. While Haeckel's tree is
somewhat outdated, it illustrates clearly the principles that more complex modern reconstructions can obscure.

Evolution is the process of change in all forms of life over generations, and evolutionary biology is the study of how
evolution occurs.
The biodiversity of life evolves by means of natural selection, mutations and genetic drift. The process of natural
selection is based on three conditions. First, every individual is supplied with hereditary material in the form of
genes that are received from their parents; then, passed on to their offspring. Second, organisms tend to produce
more offspring than the environment can support. Third, there are variations among offspring as a consequence of
either the random introduction of new genes via mutations or reshuffling of existing genes during sexual
reproduction.[1] [2] [3]
Natural selection will occur when these facts of nature (heredity, overproduction of offspring, and variation) hold
true. Natural selection means individuals do not have equal chances of reproductive success. As a consequence,
some individuals produce more offspring and thus have a higher degree of fitness. Traits that ensure organisms are
Introduction to evolution 2

better adapted to their living conditions become more common in descendant populations.[2] [3] For this reason,
populations will never remain exactly the same over successive generations. The forces of evolution are most evident
when populations become isolated, either through geographic distance or by mechanisms that prevent genetic
exchange. Over time, isolated populations can branch off into new species.[4] [5]
Random genetic drift describes another natural process that regulates the evolution of minor mutations in the genes,
leading to changes in allele frequencies over time. These smaller mutations occur with regular frequency in and
among populations. The vast majority of genetic mutations neither assist, change the appearance of, nor bring harm
to individuals. These mutated genes are neutrally sorted among populations and survive across generations by
chance alone. When species migrate they carry different genetic varieties to different places. When organisms mate
they exchange genetic material and new individuals are born.
The outward expression of each unique genetic mixture in different environments, the phenotype, comprises a
diversity of traits that can be measured and observed as individuals grow and develop. In contrast to genetic drift,
natural selection is not a random process because it acts on traits that become adaptive for their functional utilities
that are necessary for survival.[6] Natural selection and random genetic drift are forever constant and dynamic parts
of life. More than 99.9% of all species have become extinct since life began over 3.5 billion years ago. Evolution is
more death than survival and over time this has shaped the branching structure in the tree of life.[7]
The modern understanding of evolution began with the 1859 publication of Charles Darwin's On the Origin of
Species. In addition, Gregor Mendel's work with plants helped to explain the hereditary patterns of genetics.[8] Fossil
discoveries in paleontology, advances in population genetics and a global network of scientific research have
provided further details into the mechanisms of evolution. Scientists now have a good understanding of the origin of
new species (speciation) and have observed the speciation process in the laboratory and in the wild. Evolution is the
principal theory that biologists use to understand life and is used in many disciplines, including medicine,
psychology, conservation biology, anthropology, forensics, agriculture and other social-cultural applications.

Darwin's idea: evolution by natural selection

In the 19th century, natural history collections and museums were a popular pastime. The European expansion and
naval expeditions employed naturalists and curators of grand museums showcasing preserved and live specimens of
the varieties of life. Charles Darwin was an English graduate who was educated and trained in the disciplines of
natural history science. Such natural historians would collect, catalogue, describe and study the vast collections of
specimens stored and managed by curators at these museums. Charles Darwin served as a ship's naturalist on board
the HMS Beagle, assigned to a five-year research expedition around the world. During his voyage, Darwin observed
and collected an abundance of organisms, being very interested in the diverse forms of life along the coasts of South
America and the neighboring Galapagos Islands.[9] [10]
Charles Darwin gained extensive experience as he collected and studied the natural history of life forms from distant
places. Through his studies, Darwin formulated the idea that each species had developed from ancestors with similar
features. In 1838, he described how a process he called natural selection would make this happen.[11]
Darwin's idea of how evolution works relied on the following observations:[12]
• If all the individuals of a species reproduced successfully, the population of that species would increase
uncontrollably.
• Populations tend to remain about the same size from year to year.
• Environmental resources are limited.
• No two individuals in a given species are exactly alike.
• Much of this variation in a population can be passed on to offspring.
Introduction to evolution 3

Charles Darwin proposed the theory of evolution by natural selection.

Darwin noted that orchids exhibited a variety of complex adaptations to ensure pollination; all derived from basic
floral parts.
Darwin deduced that since organisms produce more offspring than their environment could possibly support, there
must be a competitive struggle for survival—only a few individuals can survive out of each generation. Darwin
realized that it was not chance alone that determined survival. Instead, survival depends on the traits of each
individual and if these traits aid or hinder survival and reproduction. Well-adapted, or "fit", individuals are likely to
leave more offspring than their less well-adapted competitors. Darwin realized that the unequal ability of individuals
to survive and reproduce could cause gradual changes in the population. Traits that help an organism survive and
reproduce would accumulate over generations. On the other hand, traits that hinder survival and reproduction would
disappear. Darwin used the term natural selection to describe this process.[13]
Natural selection is commonly equated with survival of the fittest, but this expression originated in Herbert Spencer's
Principles of Biology in 1864, after Charles Darwin published his original works. Survival of the fittest describes the
process of natural selection incorrectly, because natural selection is not only about survival and it is not always the
fittest that survives.[14]
Observations of variations in animals and plants formed the basis of the theory of natural selection. For example,
Darwin observed that orchids and insects have a close relationship that allows the pollination of the plants. He noted
that orchids have a variety of structures that attract insects, so that pollen from the flowers gets stuck to the insects’
bodies. In this way, insects transport the pollen from a male to a female orchid. In spite of the elaborate appearance
of orchids, these specialized parts are made from the same basic structures that make up other flowers. In
Fertilisation of Orchids Darwin proposed that the orchid flowers did not represent the work of an ideal engineer, but
were adapted from pre-existing parts, through natural selection.[15]
Darwin was still researching and experimenting with his ideas on natural selection when he received a letter from
Alfred Wallace describing a theory very similar to his own. This led to an immediate joint publication of both
theories. Both Wallace and Darwin saw the history of life like a family tree, with each fork in the tree’s limbs being a
common ancestor. The tips of the limbs represented modern species and the branches represented the common
ancestors that are shared amongst many different species. To explain these relationships, Darwin said that all living
things were related, and this meant that all life must be descended from a few forms, or even from a single common
Introduction to evolution 4

ancestor. He called this process descent with modification.[12]

Darwin published his theory of evolution by natural selection in On the Origin of Species in 1859. His theory means
that all life, including humanity, is a product of continuing natural processes. The implication that all life on Earth
has a common ancestor has met with objections from some religious groups who believe even today that the
different types of life are due to special creation.[16] Their objections are in contrast to the level of support for the
theory by more than 99 percent of those within the scientific community today.[17]

Source of variation
Darwin’s theory of natural selection laid the groundwork for modern evolutionary theory, and his experiments and
observations showed that the organisms in populations varied from each other, that some of these variations were
inherited, and that these differences could be acted on by natural selection. However, he could not explain the source
of these variations. Like many of his predecessors, Darwin mistakenly thought that heritable traits were a product of
use and disuse, and that features acquired during an organism's lifetime could be passed on to its offspring. He
looked for examples, such as large ground feeding birds getting stronger legs through exercise, and weaker wings
from not flying until, like the ostrich, they could not fly at all.[18] This misunderstanding was called the inheritance
of acquired characters and was part of the theory of transmutation of species put forward in 1809 by Jean-Baptiste
Lamarck. In the late 19th century this theory became known as Lamarckism. Darwin produced an unsuccessful
theory he called pangenesis to try to explain how acquired characteristics could be inherited. In the 1880s August
Weismann's experiments indicated that changes from use and disuse could not be inherited, and Lamarckism
gradually fell from favor.[19]
The missing information needed to help explain how new features could pass from a parent to its offspring was
provided by the pioneering genetics work of Gregor Mendel. Mendel’s experiments with several generations of pea
plants demonstrated that inheritance works by separating and reshuffling hereditary information during the formation
of sex cells and recombining that information during fertilization. This is like mixing different hands of cards, with
an organism getting a random mix of half of the cards from one parent, and half of the cards from the other. Mendel
called the information factors; however, they later became known as genes. Genes are the basic units of heredity in
living organisms. They contain the information that directs the physical development and behavior of organisms.
Genes are made of DNA, a long molecule that carries information. This information is encoded in the sequence of
nucleotides in the DNA, just as the sequence of the letters in words carries information on a page. The genes are like
short instructions built up of the "letters" of the DNA alphabet. Put together, the entire set of these genes gives
enough information to serve as an "instruction manual" of how to build and run an organism. The instructions
spelled out by this DNA alphabet can be changed, however, by mutations, and this may alter the instructions carried
within the genes. Within the cell, the genes are carried in chromosomes, which are packages for carrying the DNA,
with the genes arranged along them like beads on a string. It is the reshuffling of the chromosomes that results in
unique combinations of genes in offspring.
Although such mutations in DNA are random, natural selection is not a process of chance: the environment
determines the probability of reproductive success. The end products of natural selection are organisms that are
adapted to their present environments. Natural selection does not involve progress towards an ultimate goal.
Evolution does not necessarily strive for more advanced, more intelligent, or more sophisticated life forms.[20] For
example, fleas (wingless parasites) are descended from a winged, ancestral scorpionfly, and snakes are lizards that
no longer require limbs - although pythons still grow tiny structures that are the remains of their ancestor's hind
legs.[21] [22] Organisms are merely the outcome of variations that succeed or fail, dependent upon the environmental
conditions at the time.
Rapid environmental changes typically cause extinctions.[23] Of all species that have existed on Earth, 99.9 percent
are now extinct.[24] Since life began on Earth, five major mass extinctions have led to large and sudden drops in the
variety of species. The most recent, the Cretaceous–Tertiary extinction event, occurred 65 million years ago, and has
Introduction to evolution 5

attracted more attention than all others because it killed the dinosaurs.[25]

Modern synthesis
The modern evolutionary synthesis was the outcome of a merger of several different scientific fields into a cohesive
understanding of evolutionary theory. In the 1930s and 1940s, efforts were made to merge Darwin's theory of natural
selection, research in heredity, and understandings of the fossil records into a unified explanatory model.[26] The
application of the principles of genetics to naturally occurring populations, by scientists such as Theodosius
Dobzhansky and Ernst Mayr, advanced understanding of the processes of evolution. Dobzhansky's 1937 work
Genetics and the Origin of Species was an important step in bridging the gap between genetics and field biology.
Mayr, on the basis of an understanding of genes and direct observations of evolutionary processes from field
research, introduced the biological species concept, which defined a species as a group of interbreeding or
potentially interbreeding populations that are reproductively isolated from all other populations. The paleontologist
George Gaylord Simpson helped to incorporate fossil research, which showed a pattern consistent with the branching
and non-directional pathway of evolution of organisms predicted by the modern synthesis.
The modern synthesis emphasizes the importance of populations as the unit of evolution, the central role of natural
selection as the most important mechanism of evolution, and the idea of gradualism to explain how large changes
evolve as an accumulation of small changes over long periods of time.

Evidence for evolution

Scientific evidence for evolution comes from many aspects of
biology, and includes fossils, homologous structures, and
molecular similarities between species' DNA.

Fossil record
Research in the field of paleontology, the study of fossils, supports
the idea that all living organisms are related. Fossils provide
evidence that accumulated changes in organisms over long periods
of time have led to the diverse forms of life we see today. A fossil
itself reveals the organism's structure and the relationships
between present and extinct species, allowing paleontologists to
construct a family tree for all of the life forms on Earth.[27]

Modern paleontology began with the work of Georges Cuvier

(1769–1832). Cuvier noted that, in sedimentary rock, each layer
contained a specific group of fossils. The deeper layers, which he
proposed to be older, contained simpler life forms. He noted that
many forms of life from the past are no longer present today. One During the voyage of the Beagle, naturalist Charles
of Cuvier’s successful contributions to the understanding of the Darwin collected fossils in South America, and found
fragments of armor which he thought were like giant
fossil record was establishing extinction as a fact. In an attempt to
versions of the scales on the modern armadillos living
explain extinction, Cuvier proposed the idea of “revolutions” or nearby. On his return, the anatomist Richard Owen
catastrophism in which he speculated that geological catastrophes showed him that the fragments were from gigantic
had occurred throughout the Earth’s history, wiping out large extinct glyptodons, related to the armadillos. This was
one of the patterns of distribution that helped Darwin to
numbers of species.[28] Cuvier's theory of revolutions was later [11]
develop his theory.
replaced by uniformitarian theories, notably those of James Hutton
Introduction to evolution 6

and Charles Lyell who proposed that the Earth’s geological changes were gradual and consistent.[29] However,
current evidence in the fossil record supports the concept of mass extinctions. As a result, the general idea of
catastrophism has re-emerged as a valid hypothesis for at least some of the rapid changes in life forms that appear in
the fossil records.
A very large number of fossils have now been discovered and identified. These fossils serve as a chronological
record of evolution. The fossil record provides examples of transitional species that demonstrate ancestral links
between past and present life forms.[30] One such transitional fossil is Archaeopteryx, an ancient organism that had
the distinct characteristics of a reptile (such as a long, bony tail and conical teeth) yet also had characteristics of birds
(such as feathers and a wishbone). The implication from such a find is that modern reptiles and birds arose from a
common ancestor.[31]

Comparative anatomy
The comparison of similarities between organisms of their form or appearance of parts, called their morphology, has
long been a way to classify life into closely related groups. This can be done by comparing the structure of adult
organisms in different species or by comparing the patterns of how cells grow, divide and even migrate during an
organism's development.

Taxonomy
Taxonomy is the branch of biology that names and classifies all living things. Scientists use morphological and
genetic similarities to assist them in categorizing life forms based on ancestral relationships. For example,
orangutans, gorillas, chimpanzees, and humans all belong to the same taxonomic grouping referred to as a family –
in this case the family called Hominidae. These animals are grouped together because of similarities in morphology
that come from common ancestry (called homology).[32]
Strong evidence for evolution comes from the analysis of homologous structures: structures in different species that
no longer perform the same task but which share a similar structure.[33] Such is the case of the forelimbs of
mammals. The forelimbs of a human, cat, whale, and bat all have strikingly similar bone structures. However, each
of these four species' forelimbs performs a different task. The same bones that construct a bat's wings, which are
used for flight, also construct a whale's flippers, which are used for swimming. Such a "design" makes little sense if
they are unrelated and uniquely constructed for their particular tasks. The theory of evolution explains these
homologous structures: all four animals shared a common ancestor, and each has undergone change over many
generations. These changes in structure have produced forelimbs adapted for different tasks.[34]

Embryology
In some cases, anatomical comparison of structures in the embryos of two or more species provides evidence for a
shared ancestor that may not be obvious in the adult forms. As the embryo develops, these homologies can be lost to
view, and the structures can take on different functions. Part of the basis of classifying the vertebrate group (which
includes humans), is the presence of a tail (extending beyond the anus) and pharyngeal slits. Both structures appear
during some stage of embryonic development but are not always obvious in the adult form.[35]
Because of the morphological similarities present in embryos of different species during development, it was once
assumed that organisms re-enact their evolutionary history as an embryo. It was thought that human embryos passed
through an amphibian then a reptilian stage before completing their development as mammals. Such a re-enactment,
(often called Recapitulation theory), is not supported by scientific evidence. What does occur, however, is that the
first stages of development are similar in broad groups of organisms.[36] At very early stages, for instance, all
vertebrates appear extremely similar, but do not exactly resemble any ancestral species. As development continues,
specific features emerge from this basic pattern.
Introduction to evolution 7

Vestigial structures
Homology includes a unique group of shared structures referred to as vestigial structures. Vestigial refers to
anatomical parts that are of minimal, if any, value to the organism that possesses them. These apparently illogical
structures are remnants of organs that played an important role in ancestral forms. Such is the case in whales, which
have small vestigial bones that appear to be remnants of the leg bones of their ancestors which walked on land.[37]
Humans also have vestigial structures, including the ear muscles, the wisdom teeth, the appendix, the tail bone, body
hair (including goose bumps), and the semilunar fold in the corner of the eye.[38]

Convergent evolution

Anatomical comparisons can be misleading, as not all anatomical

similarities indicate a close relationship. Organisms that share
similar environments will often develop similar physical features,
a process known as convergent evolution. Both sharks and
dolphins have similar body forms, yet are only distantly related –
sharks are fish and dolphins are mammals. Such similarities are a
result of both populations being exposed to the same selective
The bird and the bat wing are examples of convergent
pressures. Within both groups, changes that aid swimming have
evolution. been favored. Thus, over time, they developed similar appearances
(morphology), even though they are not closely related.[39]

A bat is a mammal and its forearm bones

have been adapted for flight.
Introduction to evolution 8

Molecular biology
Every living organism (with the possible exception of RNA viruses) contains
molecules of DNA, which carries genetic information. Genes are the pieces of
DNA that carry this information, and they influence the properties of an
organism. Genes determine an individual's general appearance and to some
extent their behavior. If two organisms are closely related, their DNA will be
very similar.[40] On the other hand, the more distantly related two organisms
are, the more differences they will have. For example, brothers are closely
related and have very similar DNA, while cousins share a more distant
relationship and have far more differences in their DNA. Similarities in DNA
are used to determine the relationships between species in much the same
manner as they are used to show relationships between individuals. For
example, comparing chimpanzees with gorillas and humans shows that there is
as much as a 96 percent similarity between the DNA of humans and chimps.
Comparisons of DNA indicate that humans and chimpanzees are more closely
related to each other than either species is to gorillas.[41] [42]

The field of molecular systematics focuses on measuring the similarities in

these molecules and using this information to work out how different types of
organisms are related through evolution. These comparisons have allowed
biologists to build a relationship tree of the evolution of life on Earth.[43] They
have even allowed scientists to unravel the relationships between organisms
whose common ancestors lived such a long time ago that no real similarities
remain in the appearance of the organisms.
A section of DNA

Co-evolution
Co-evolution is a process in which two or more species influence the evolution of each other. All organisms are
influenced by life around them; however, in co-evolution there is evidence that genetically determined traits in each
species directly resulted from the interaction between the two organisms.[40]
An extensively documented case of co-evolution is the relationship between Pseudomyrmex, a type of ant, and the
acacia, a plant that the ant uses for food and shelter. The relationship between the two is so intimate that it has led to
the evolution of special structures and behaviors in both organisms. The ant defends the acacia against herbivores
and clears the forest floor of the seeds from competing plants. In response, the plant has evolved swollen thorns that
the ants use as shelter and special flower parts that the ants eat.[44] Such co-evolution does not imply that the ants
and the tree choose to behave in an altruistic manner. Rather, across a population small genetic changes in both ant
and tree benefited each. The benefit gave a slightly higher chance of the characteristic being passed on to the next
generation. Over time, successive mutations created the relationship we observe today.
Introduction to evolution 9

Artificial selection
Artificial selection is the controlled breeding of domestic plants
and animals. Humans determine which animal or plant will
reproduce and which of the offspring will survive; thus, they
determine which genes will be passed on to future generations.
The process of artificial selection has had a significant impact on
the evolution of domestic animals. For example, people have
produced different types of dogs by controlled breeding. The
differences in size between the Chihuahua and the Great Dane are
the result of artificial selection. Despite their dramatically different
physical appearance, they and all other dogs evolved from a few
wolves domesticated by humans in what is now China less than
The results of artificial selection: a Chihuahua mix and
15,000 years ago.[45]
a Great Dane.

Artificial selection has produced a wide variety of plants. In the

case of maize (corn), recent genetic evidence suggests that domestication occurred 10,000 years ago in central
Mexico.[46] Prior to domestication, the edible portion of the wild form was small and difficult to collect. Today The
Maize Genetics Cooperation • Stock Center maintains a collection of more than 10,000 genetic variations of maize
that have arisen by random mutations and chromosomal variations from the original wild type.[47]
In artificial selection the new breed or variety that emerges is the one with random mutations attractive to humans,
while in natural selection the surviving species is the one with random mutations useful to it in its non-human
environment. In both natural and artificial selection the variations are a result of random mutations, and the
underlying genetic processes are essentially the same.[48] Darwin carefully observed the outcomes of artificial
selection in animals and plants to form many of his arguments in support of natural selection.[49] Much of his book
On the Origin of Species was based on these observations of the many varieties of domestic pigeons arising from
artificial selection. Darwin proposed that if humans could achieve dramatic changes in domestic animals in short
periods, then natural selection, given millions of years, could produce the differences seen in living things today.

Species
Given the right circumstances, and enough time, evolution leads to
the emergence of new species. Scientists have struggled to find a
precise and all-inclusive definition of species. Ernst Mayr
(1904–2005) defined a species as a population or group of
populations whose members have the potential to interbreed
naturally with one another to produce viable, fertile offspring.
(The members of a species cannot produce viable, fertile offspring
There are numerous species of cichlids that with members of other species).[50] Mayr's definition has gained
demonstrate dramatic variations in morphology. wide acceptance among biologists, but does not apply to
organisms such as bacteria, which reproduce asexually.

Speciation is the lineage-splitting event that results in two separate species forming from a single common ancestral
population.[13] A widely accepted method of speciation is called allopatric speciation. Allopatric speciation begins
when a population becomes geographically separated.[33] Geological processes, such as the emergence of mountain
ranges, the formation of canyons, or the flooding of land bridges by changes in sea level may result in separate
populations. For speciation to occur, separation must be substantial, so that genetic exchange between the two
Introduction to evolution 10

populations is completely disrupted. In their separate environments, the genetically isolated groups follow their own
unique evolutionary pathways. Each group will accumulate different mutations as well as be subjected to different
selective pressures. The accumulated genetic changes may result in separated populations that can no longer
interbreed if they are reunited.[13] Barriers that prevent interbreeding are either prezygotic (prevent mating or
fertilization) or postzygotic (barriers that occur after fertilization). If interbreeding is no longer possible, then they
will be considered different species.[51]
Usually the process of speciation is slow, occurring over very long time spans; thus direct observations within
human life-spans are rare. However speciation has been observed in present day organisms, and past speciation
events are recorded in fossils.[52] [53] [54] Scientists have documented the formation of five new species of cichlid
fishes from a single common ancestor that was isolated fewer than 5000 years ago from the parent stock in Lake
Nagubago.[55] The evidence for speciation in this case was morphology (physical appearance) and lack of natural
interbreeding. These fish have complex mating rituals and a variety of colorations; the slight modifications
introduced in the new species have changed the mate selection process and the five forms that arose could not be
convinced to interbreed.[56]

Different views on the mechanism of evolution

James Hutton

Stephen Jay Gould

Richard Dawkins

The theory of evolution is widely accepted among the scientific community, serving to link the diverse specialty
areas of biology.[17] Evolution provides the field of biology with a solid scientific base. The significance of
evolutionary theory is best described by the title of a paper by Theodosius Dobzhansky (1900–1975), published in
American Biology Teacher; "Nothing in Biology Makes Sense Except in the Light of Evolution".[57] Nevertheless,
the theory of evolution is not static. There is much discussion within the scientific community concerning the
mechanisms behind the evolutionary process. For example, the rate at which evolution occurs is still under
discussion. In addition, there are conflicting opinions as to which is the primary unit of evolutionary change – the
Introduction to evolution 11

organism or the gene.

Rate of change
Two views exist concerning the rate of evolutionary change. Darwin and his contemporaries viewed evolution as a
slow and gradual process. Evolutionary trees are based on the idea that profound differences in species are the result
of many small changes that accumulate over long periods.
The view that evolution is gradual had its basis in the works of the geologist James Hutton (1726–1797) and his
theory called "gradualism". Hutton's theory suggests that profound geological change was the cumulative product of
a relatively slow continuing operation of processes which can still be seen in operation today, as opposed to
catastrophism which promoted the idea that sudden changes had causes which can no longer be seen at work. A
uniformitarian perspective was adopted for biological changes. Such a view can seem to contradict the fossil record,
which shows evidence of new species appearing suddenly, then persisting in that form for long periods. The
paleontologist Stephen Jay Gould (1941–2002) developed a model that suggests that evolution, although a slow
process in human terms, undergoes periods of relatively rapid change over only a few thousand or million years,
alternating with long periods of relative stability, a model called "punctuated equilibrium" which explains the fossil
record without contradicting Darwin's ideas.[58]

Unit of change
A common unit of selection in evolution is the organism. Natural selection occurs when the reproductive success of
an individual is improved or reduced by an inherited characteristic, and reproductive success is measured by the
number of an individual's surviving offspring. The organism view has been challenged by a variety of biologists as
well as philosophers. Richard Dawkins (born 1941) proposes that much insight can be gained if we look at evolution
from the gene's point of view; that is, that natural selection operates as an evolutionary mechanism on genes as well
as organisms.[59] In his 1976 book The Selfish Gene, he explains:

“ Individuals are not stable things, they are fleeting. Chromosomes too are shuffled to oblivion, like hands of cards soon after they are dealt. But
the cards themselves survive the shuffling. The cards are the genes. The genes are not destroyed by crossing-over; they merely change partners
and march on. Of course they march on. That is their business. They are the replicators and we are their survival machines. When we have
served our purpose we are cast aside. But genes are denizens of geological time: genes are forever.
[60]
”
Others view selection working on many levels, not just at a single level of organism or gene; for example, Stephen
Jay Gould called for a hierarchical perspective on selection.[61]

Summary
Several basic observations establish the theory of evolution, which explains the variety and relationship of all living
things. There are genetic variations within a population of individuals. Some individuals, by chance, have features
that allow them to survive and thrive better than their kind. The individuals that survive will be more likely to have
offspring of their own. The offspring might inherit the useful feature.
Evolution is not a random process. While mutations are random, natural selection is not. Evolution is an inevitable
result of imperfectly copying, self-replicating organisms reproducing over billions of years under the selective
pressure of the environment. The outcome of evolution is not a perfectly designed organism. The outcome is simply
an individual that can survive better and reproduce more successfully than its neighbors in a particular environment.
Fossils, the genetic code, and the peculiar distribution of life on Earth provide a record of evolution and demonstrate
the common ancestry of all organisms, both living and long dead. Evolution can be directly observed in artificial
selection, the selective breeding for certain traits of domestic animals and plants. The diverse breeds of cats, dogs,
horses, and agricultural plants serve as examples of evolution.
Introduction to evolution 12

Although some groups raise objections to the theory of evolution, the evidence of observation and experiments over
a hundred years by thousands of scientists supports evolution.[16] The result of four billion years of evolution is the
diversity of life around us, with an estimated 1.75 million different species in existence today.[5] [62]

See also
• Creation-evolution controversy
• Evidence of common descent
• Evolution as theory and fact
• Level of support for evolution
• Misconceptions about evolution

Notes
[1] Darwin, Charles (1859). On the Origin of Species (http:/ / darwin-online. org. uk/ content/ frameset?itemID=F373& viewtype=text&
pageseq=16) (1st ed.). London: John Murray. p. 1. .. Related earlier ideas were acknowledged in Darwin, Charles (1861). On the Origin of
Species (http:/ / darwin-online. org. uk/ content/ frameset?itemID=F381& viewtype=text& pageseq=20) (3rd ed.). London: John Murray. xiii. .
[2] Gould, Stephen J. (2002). The Structure of Evolutionary Theory. Harvard University Press. pp. 1433. ISBN 0674006135, 9780674006133.
[3] Gregory, T. R. (2009). "Understanding Natural Selection: Essential Concepts and Common Misconceptions" (http:/ / www. springerlink.
com/ content/ 2331741806807x22/ ). Evolution: Education and Outreach 2 (2): 156–175. doi:10.1007/s12052-009-0128-1. .
[4] "An introduction to evolution" (http:/ / evolution. berkeley. edu/ evolibrary/ article/ 0_0_0/ evo_02) (web resource). Understanding
Evolution: your one-stop source for information on evolution (http:/ / evolution. berkeley. edu/ evolibrary/ article/ 0_0_0/ evo_01). The
University of California Museum of Paleontology, Berkeley. 2008. . Retrieved 2008-01-23
[5] Cavalier-Smith T (2006). "Cell evolution and Earth history: stasis and revolution" (http:/ / www. ncbi. nlm. nih. gov/ pubmed/ 16754610).
Philos Trans R Soc Lond B Biol Sci 361 (1470): 969–1006. doi:10.1098/rstb.2006.1842. PMID 16754610. PMC 1578732. . Retrieved
2008-01-24.
[6] Garvin-Doxas, K.; Klymkowsky, M. W. (2008). "Understanding Randomness and its Impact on Student Learning: Lessons Learned from
Building the Biology Concept Inventory (BCI)" (http:/ / www. ncbi. nlm. nih. gov/ pmc/ articles/ PMC2424310/ ). CBE Life Sci Educ. 7 (2):
227–233. doi:10.1187/cbe.07-08-0063. PMID 18519614. PMC 2424310. .
[7] Raup, D. M. (1992). Extinction: bad genes or bad luck. (http:/ / books. google. com/ ?id=8klou91MwJoC& printsec=frontcover&
dq=Extinction:+ bad+ genes+ or+ bad+ luck& cd=1#v=onepage& q=). New York, W. W.: Norton and Co.. pp. 210. ISBN 978-0393309270. .
[8] Rhee, Sue Yon (1999). "Gregor Mendel" (http:/ / www. accessexcellence. org/ RC/ AB/ BC/ Gregor_Mendel. html). Access Excellence.
National Health Museum. . Retrieved 2008-01-05.
[9] Farber, P. L. (2000). Finding Order in Nature: The Natualist Tradition from Linnaeus to E. O. Wilson (http:/ / books. google. com/
?id=tyG4pfKJ8WEC& printsec=frontcover& dq=Finding+ Order+ in+ Nature:+ The+ Natualist+ Tradition+ from+ Linnaeus+ to+ E. + O. +
Wilson& cd=1#v=onepage& q=). Baltimore and London: The Johns Hopkins University Press. pp. 136. ISBN 0-8018-6389-9. .
[10] Watson, J. D. (2005). Darwin, The Indelible Stamp: The Evolution of an Idea (http:/ / books. google. com/ ?id=LEWfWf0mUJIC&
printsec=frontcover& dq=Darwin:+ The+ Indelible+ Stamp:+ The+ Evolution+ of+ an+ Idea& cd=1#v=onepage& q=). Philadelphia and
London: Running Press. pp. 1257. ISBN 13-978-0-7624-2136-7. .
[11] Eldredge, Niles (Spring 2006). "Confessions of a Darwinist" (http:/ / www. vqronline. org/ articles/ 2006/ spring/
eldredge-confessions-darwinist/ ). The Virginia Quarterly Review: 32–53. . Retrieved 2008-01-23.
[12] Wyhe, John van (2002). "Charles Darwin: gentleman naturalist" (http:/ / darwin-online. org. uk/ darwin. html). The Complete Work of
Charles Darwin Online. University of Cambridge. . Retrieved 2008-01-16.
[13] Quammen, David (2004). "Was Darwin Wrong?" (http:/ / ngm. nationalgeographic. com/ ngm/ 0411/ feature1/ fulltext. html#top). National
Geographic Magazine. National Geographic. . Retrieved 2007-12-23.
[14] Futuyma, D. J. (2005). The Nature of Natural Selection. Ch. 8, pages 93-98 in Cracraft, J. and Bybee R. W. (Eds.) Evolutionary Science and
Society: Educating a New Generation. American Institute of Biological Sciences.
[15] Wyhe, John van (2002). "Fertilisation of Orchids" (http:/ / darwin-online. org. uk/ EditorialIntroductions/ Freeman_FertilisationofOrchids.
html). The Complete Works of Charles Darwin. University of Cambridge. . Retrieved 2008-01-07.
[16] DeVries A (2004). "The enigma of Darwin". Clio Med 19 (2): 136–55. PMID 6085987.
[17] Delgado, Cynthia (2006). "Finding the Evolution in Medicine" (http:/ / nihrecord. od. nih. gov/ newsletters/ 2006/ 07_28_2006/ story03.
htm). NIH Record (National Institutes of Health). . Retrieved 2007-12-21.
[18] (Darwin 1872, p.  108 (http:/ / darwin-online. org. uk/ content/ frameset?itemID=F391& viewtype=text& pageseq=136).) Effects of the
increased Use and Disuse of Parts, as controlled by Natural Selection
[19] Ghiselin, Michael T. (September/October 1994). "Nonsense in schoolbooks: 'The Imaginary Lamarck'" (http:/ / www. textbookleague. org/
54marck. htm). The Textbook Letter (http:/ / www. textbookleague. org/ ). The Textbook League. . Retrieved 2008-01-23
[20] (Gould (a) 1981, p. 24)
Introduction to evolution 13

[21] Bejder L, Hall BK (2002). "Limbs in whales and limblessness in other vertebrates: mechanisms of evolutionary and developmental
transformation and loss". Evol. Dev. 4 (6): 445–58. doi:10.1046/j.1525-142X.2002.02033.x. PMID 12492145.
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[23] Drummond, A; Strimmer, K (Jul 2001). Frequently Asked Questions About Evolution (http:/ / www. pbs. org/ wgbh/ evolution/ library/ faq/
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[25] Bambach, R.K.; Knoll, A.H.; Wang, S.C. (December 2004). "Origination, extinction, and mass depletions of marine diversity" (http:/ /
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[27] "The Fossil Record - Life's Epic" (http:/ / www. fossilmuseum. net/ fossilrecord. htm). The Virtual Fossil Museum. . Retrieved 2007-08-31.
[28] (Tattersall 1995, pp. 5–6)
[29] (Lyell 1830, p. 76)
[30] Committee on Revising Science and Creationism: A View from the National Academy of Sciences, National Academy of Sciences and
Institute of Medicine of the National Academies (2008). "Science, Evolution, and Creationism" (http:/ / books. nap. edu/ openbook.
php?record_id=11876& page=22). National Academy of Sciences. . Retrieved 2008-01-06.
[31] (Gould (b) 1995, p. 360)
[32] (Diamond 1992, p. 16)
[33] Drummond, A; Strimmer, K (Jul 2001). Glossary (http:/ / www. pbs. org/ wgbh/ evolution/ library/ glossary/ index. html). "Evolution
Library" (http:/ / www. pbs. org/ wgbh/ evolution/ library/ faq/ cat03. html) (web resource). Bioinformatics (Oxford, England) (WGBH
Educational Foundation) 17 (7): 662–3. ISSN 1367-4803. PMID 11448888. . Retrieved 2008-01-23.
[34] (Mayr 2001, pp. 25–27)
[35] (Weichert & Presch 1975, p. 8)
[36] Miller, Kenneth (1997). "Haeckel and his Embryos" (http:/ / www. millerandlevine. com/ km/ evol/ embryos/ Haeckel. html). Evolution
Resources. . Retrieved 2007-09-02.
[37] Theobald, Douglas (2004). "29+ Evidences for Macroevolution Part 2: Past History" (http:/ / www. talkorigins. org/ pdf/ comdesc. pdf)
(pdf). TalkOrigins Archive. The TalkOrigins Foundation. . Retrieved 2008-01-27.
[38] Johnson, George (2002). "Vestigial Structures" (http:/ / www. txtwriter. com/ backgrounders/ Evolution/ EVpage12. html) (web resource).
The Evidence for Evolution (http:/ / www. txtwriter. com/ backgrounders/ index. html). 'On Science' column in St. Louis Post Dispatch. .
Retrieved 2008-01-23.
[39] Johnson, George (2002). "Convergent and Divergent Evolution" (http:/ / www. txtwriter. com/ backgrounders/ Evolution/ EVpage14. html)
(web resource). The Evidence for Evolution (http:/ / www. txtwriter. com/ backgrounders/ index. html). 'On Science' column in St. Louis Post
Dispatch. . Retrieved 2008-01-23.
[40] Kennedy, Donald; (Working group on teaching evolution) (1998). "Teaching about evolution and the nature of science" (http:/ / www. nap.
edu/ readingroom/ books/ evolution98/ evol3. html). Evolution and the nature of science. The National Academy of Science. . Retrieved
2007-12-30.
[41] Lovgren, Stefan (2005-08-31). "Chimps, Humans 96 Percent the Same, Gene Study Finds" (http:/ / news. nationalgeographic. com/ news/
2005/ 08/ 0831_050831_chimp_genes. html). National Geographic News. National Geographic. . Retrieved 2007-12-23.
[42] (Carroll, Grenier & Weatherbee 2000)
[43] Ciccarelli FD, Doerks T, von Mering C, Creevey CJ, Snel B, Bork P (2006). "Toward automatic reconstruction of a highly resolved tree of
life". Science 311 (5765): 1283–87. doi:10.1126/science.1123061. PMID 16513982.
[44] Janzen, Daniel (1974). "Swollen-Thorn Acacias of Central America" (http:/ / www. sil. si. edu/ smithsoniancontributions/ Botany/ pdf_hi/
sctb-0013. pdf) (pdf). Smithsonian Contributions to Biology. Smithsonian Institution. . Retrieved 2007-08-31.
[45] McGourty, Christine (2002-11-22). "Origin of dogs traced" (http:/ / news. bbc. co. uk/ 2/ hi/ science/ nature/ 2498669. stm). BBC News. .
Retrieved 2007-12-14.
[46] Hall, Hardy. "Transgene Escape: Are Traditioanl Corn Varieties In Mexico Threatened by Transgenic Corn Crops" (http:/ / www. scq. ubc.
ca/ transgene-escape-are-traditional-corn-varieties-in-mexico-threatened-by-transgenic-corn-crops/ ?). Scientific Creative Quarterly. .
Retrieved 2007-12-14.
[47] "The Maize Genetics Cooperation • Stock Center" (http:/ / maizecoop. cropsci. uiuc. edu/ mgc-info. php). National Plant Germplasm. U.S.
Department of Agriculture. 2006-06-21. . Retrieved 2007-12-19.
[48] Silverman, E. David (2002). "Better Books by Trial and Error." (http:/ / home. comcast. net/ ~lifebook/ evolve. html). . Retrieved
2008-04-04.
Introduction to evolution 14

[49] Wilner A. (2006). "Darwin's artificial selection as an experiment". Stud Hist Philos Biol Biomed Sci. 37 (1): 26–40.
doi:10.1016/j.shpsc.2005.12.002. PMID 16473266.
[50] (Mayr 2001, pp. 165–69)
[51] Sulloway, Frank J (December 2005). "The Evolution of Charles Darwin" (http:/ / www. smithsonianmagazine. com/ issues/ 2005/ december/
darwin. php?page=2). Smithsonian Magazine. Smithsonian Institution. . Retrieved 2007-08-31.
[52] Jiggins CD, Bridle JR (2004). "Speciation in the apple maggot fly: a blend of vintages?". Trends Ecol. Evol. (Amst.) 19 (3): 111–14.
doi:10.1016/j.tree.2003.12.008. PMID 16701238.
[53] Boxhorn, John (1995). "Observed Instances of Speciation" (http:/ / www. talkorigins. org/ faqs/ faq-speciation. html). TalkOrigins Archive. .
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[54] Weinberg JR, Starczak VR, Jorg, D (1992). "Evidence for Rapid Speciation Following a Founder Event in the Laboratory" (http:/ / jstor.
org/ stable/ 2409766). Evolution (Evolution, Vol. 46, No. 4) 46 (4): 1214–20. doi:10.2307/2409766. . Retrieved 2008-01-24.
[55] (Mayr 1970, p. 348)
[56] (Mayr 1970)
[57] "NCSE Resource" (http:/ / ncseweb. org/ evolution/ education/ cans-cants-teaching-evolution). Cans and Can`ts of Teaching Evolution.
National Center for Science Education. 2001-02-13. . Retrieved 2008-01-01.
[58] Gould, Stephen Jay (1991). "Opus 200" (http:/ / www. stephenjaygould. org/ library/ gould_opus200. html). Stephen Jay Gould Archive.
Natural History. . Retrieved 2007-08-31.
[59] Wright, Sewall (September 1980). "Genic and Organismic Selection" (http:/ / links. jstor. org/
sici?sici=0014-3820(198009)34:5<825:GAOS>2. 0. CO;2-Z& size=LARGE& origin=JSTOR-enlargePage). Evolution (Evolution, Vol. 34,
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Darwinism?" (http:/ / www. pnas. org/ cgi/ pmidlookup?view=long& pmid=10518549). Proc. Natl. Acad. Sci. U.S.A. 96 (21): 11904–9.
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Council. . Retrieved 2008-01-05.

References
• Carroll, SB; Grenier, J; Weatherbee, SD (2000). From DNA to Diversity: Molecular Genetics and the Evolution
of Animal Design (2nd ed.). Oxford: Blackwell Publishing. ISBN 1-4051-1950-0
• Darwin, Charles (1872). [[On the Origin of Species|The Origin of Species (http://darwin-online.org.uk/content/
frameset?itemID=F391&viewtype=text&pageseq=1)]] (6th ed.). London: John Murray
• Dawkins, Richard (1976). The Selfish Gene (http://www.scribd.com/doc/104123/
Richard-Dawkins-The-Selfish-Gene-Original-Ed) (1st ed.). Oxford University Press. pp. 33. ISBN 0192860925
• Diamond, Jared (1992). The Third Chimpanzee: the evolution and future of the human animal. New York:
HarperCollins. ISBN 0060183071
• Gould (a), Stephen Jay (1981). The Panda's Thumb: More Reflections in Natural History. New York: W.W,
Norton & Company. ISBN 0393308197
• Gould (b), Stephen Jay (1995). Dinosaur in a Haystack. New York: Harmony Books. ISBN 0517703939
• Lyell, Charles (1830). Principles of geology (http://www.esp.org/books/lyell/principles/facsimile/). New
York: Penguin Books. ISBN 014043528X
• Mayr, Ernst (1970). Populations, Species, and Evolution. Cambridge, MA: Belknap Press of Harvard University
Press. ISBN 0674690109
• Mayr, Ernst (2001). What evolution is. New York: Basic Books. ISBN 0-465-04425-5
• Tattersall, Ian (1995). The Fossil Trail: How We Know What We Think We Know About Human Evolution. New
York: Oxford University Press. ISBN 0195061012
• Weichert, Charles; Presch, William (1975). Elements of Chordate Anatomy. New York: McGraw-Hill.
ISBN 0070690081
Introduction to evolution 15

Further reading
• Liam Neeson (narrator). (2001-11-20) (web resource). Evolution: a journey into where we're from and where
we're going (http://www.pbs.org/wgbh/evolution/index.html). [DVD]. South Burlington, VT: WGBH Boston
/ PBS television series Nova. ASIN: B00005RG6J. Retrieved 2008-01-24. - Age level: Grade 7+
• Horvitz, Leslie Alan (2002). The complete idiot's guide to evolution. Indianapolis: Alpha Books.
ISBN 0028642260.
• Charlesworth, Deborah; Charlesworth, Brian (2003). Evolution: a very short introduction. Oxford: Oxford
University Press. ISBN 0192802518.
• Sis, Peter (2003). The tree of life: a book depicting the life of Charles Darwin, naturalist, geologist & thinker.
New York: Farrar Straus Giroux. ISBN 0-374-45628-3.
• Thomson, Keith Stewart (2005). Fossils: a very short introduction. Oxford: Oxford University Press.
ISBN 0192805045.
• Greg Krukonis (2008). Evolution For Dummies (For Dummies (Math & Science)). For Dummies.
ISBN 0-470-11773-7.
• Darwin, Charles (2008). Quammen, David. ed. On the Origin of Species: The Illustrated Edition. Sterling.
ISBN 1402756399
• Pallan, Mark (2009). The Rough Guide to Evolution. Rough Guides. ISBN 1858289467
• Zimmer, Carl (2009). The Tangled Bank: An Introduction to Evolution. Roberts and Company Publishers.
ISBN 0981519474
• Ellis, R. John (2010). How Science Works: Evolution. Springer. ISBN 9048131820

External links
• Brain, Marshall. "How Stuff Works: Evolution Library" (http://science.howstuffworks.com/evolution-channel.
htm) (web resource). Howstuffworks.com. Retrieved 2008-01-24
• Carl Sagan. (2006-07-06) (Google video). Carl Sagan on evolution (http://video.google.com/
videoplay?docid=-522726029201501667&q=carl+sagan). [streaming video]. Google. Retrieved 2008-01-24.
• Carl Sagan. (2006-10-21) (Youtube video). Theory of Evolution Explained (http://www.youtube.com/
watch?v=E1Y5zMo74cY). [streaming video]. Youtube. Retrieved 2008-01-24.
• "Evolution Education Wiki: EvoWiki" (http://wiki.cotch.net/) (web resource). Retrieved 2008-01-24
• "The Big Picture on Evolution (PDF)" (http://www.wellcome.ac.uk/stellent/groups/corporatesite/
@msh_publishing_group/documents/web_document/wtd026042.pdf). The Big Picture Series (http://www.
wellcome.ac.uk/Professional-resources/Education-resources/Big-Picture/Evolution/). Wellcome Trust.
January 2007. Retrieved 2008-01-23
• "The Talk Origins Archive: Exploring the Creation/Evolution Controversy" (http://www.talkorigins.org/) (web
resource). Retrieved 2008-01-24
• (web resource) Understanding Evolution: your one-stop source for information on evolution (http://evolution.
berkeley.edu/evolibrary/article/0_0_0/evo_01). The University of California Museum of Paleontology,
Berkeley. Retrieved 2008-01-24
• "University of Utah Genetics Learning Center animated tour of the basics of genetics" (http://learn.genetics.
utah.edu/units/basics/tour) (web resource). Howstuffworks.com. Retrieved 2008-01-24
• "Introduction To Evolution" (http://www.vectorsite.net/taevo.html) (web resource). vectorsite.net. Retrieved
2010-06-01
Evolution 16

Evolution
Evolution (also known as biological, genetic or organic evolution) is the change in the inherited traits of a
population of organisms through successive generations.[1] This change results from interactions between processes
that introduce variation into a population, and other processes that remove it. As a result, variants with particular
traits become more, or less, common. A trait is a particular characteristic—anatomical, biochemical or
behavioural—that is the result of gene–environment interaction.
The main source of variation is mutation, which introduces genetic changes. These changes are heritable (can be
passed on through reproduction), and may give rise to alternative traits in organisms. Another source of variation is
genetic recombination, which shuffles the genes into new combinations which can result in organisms exhibiting
different traits. Under certain circumstances, variation can also be increased by the transfer of genes between
species,[2] [3] and by the extremely rare, but significant, wholesale incorporation of genomes through
endosymbiosis.[4] [5]
Two main processes cause variants to become more common or rarer in a population. One is natural selection,
through which traits that aid survival and reproduction become more common, while traits that hinder survival and
reproduction become rarer. Natural selection occurs because only a small proportion of individuals in each
generation will survive and reproduce, since resources are limited and organisms produce many more offspring than
their environment can support. Over many generations, heritable variation in traits is filtered by natural selection and
the beneficial changes are successively retained through differential survival and reproduction. This iterative process
adjusts traits so they become better suited to an organism's environment: these adjustments are called adaptations.[6]
However, not all change is adaptive. Another cause of evolution is genetic drift, which leads to random changes in
how common traits are in a population. Genetic drift is most important when traits do not strongly influence
survival—particularly so in small populations, in which chance plays a disproportionate role in the frequency of
traits passed on to the next generation.[7] [8] Genetic drift is important in the neutral theory of molecular evolution,
and plays a role in the molecular clocks that are used in phylogenetic studies.
A key process in evolution is speciation, in which a single ancestral species splits and diversifies into multiple new
species. There are several modes through which this occurs. Ultimately, all living (and extinct) species are descended
from a common ancestor via a long series of speciation events. These events stretch back in a diverse "tree of life"
which has grown over the 3.5 billion years during which life has existed on Earth.[9] [10] [11] [12] This is visible in
anatomical, genetic and other similarities between groups of organisms, geographical distribution of related species,
the fossil record and the recorded genetic changes in living organisms over many generations.
Evolutionary biologists document the fact that evolution occurs, and also develop and test theories which explain its
causes. The study of evolutionary biology began in the mid-nineteenth century, when research into the fossil record
and the diversity of living organisms convinced most scientists that species changed over time.[13] The mechanism
driving these changes remained unclear until the theory of natural selection was independently proposed by Charles
Darwin and Alfred Wallace. In 1859, Darwin's seminal work On the Origin of Species brought the new theory of
evolution by natural selection to a wide audience,[14] leading to the overwhelming acceptance of evolution among
scientists.[15] [16] [17] [18] In the 1930s, Darwinian natural selection became understood in combination with
Mendelian inheritance, forming the modern evolutionary synthesis,[19] which connected the substrate of evolution
(inherited genetics) and the mechanism of evolution (natural selection). This powerful explanatory and predictive
theory has become the central organizing principle of modern biology, directing research and providing a unifying
explanation for the history and diversity of life on Earth.[16] [17] [20] Evolution is applied and studied in fields as
diverse as agriculture, anthropology, conservation biology, ecology, medicine, paleontology, philosophy, and
psychology along with other specific topics in the previous listed fields.
Evolution 17

History of evolutionary thought

The roots of naturalistic thinking on biology can be dated to at least the 6th
century BCE, with the Greek philosopher Anaximander.[21] However, the
growth of modern biology out of natural history is fairly recent. The word
evolution (from the Latin evolutio, meaning "to unroll like a scroll") appeared
in English in the 17th century. As biological knowledge grew in the 18th
century, proto-evolutionary ideas were set out by a few natural philosophers
such as Pierre Maupertuis in 1745 and Erasmus Darwin in 1796.[22] The ideas
of the biologist Jean-Baptiste Lamarck about transmutation of species
influenced radicals, but were rejected by mainstream scientists. Charles
Darwin formulated his idea of natural selection in 1838 and was still
developing his theory in 1858 when Alfred Russel Wallace sent him a similar
Around 1854 Charles Darwin began
theory, and both were presented to the Linnean Society of London in separate
writing out what became On the Origin
papers.[23] At the end of 1859, Darwin's publication of On the Origin of of Species.
Species explained natural selection in detail and presented evidence leading to
increasingly wide acceptance of the occurrence of evolution.

Debate about the mechanisms of evolution continued, and Darwin could not explain the source of the heritable
variations which would be acted on by natural selection.[24] Like Lamarck, he still thought that parents passed on
adaptations acquired during their lifetimes,[25] a theory which was subsequently dubbed Lamarckism.[26] In the
1880s, August Weismann's experiments indicated that changes from use and disuse were not heritable, and
Lamarckism gradually fell from favour.[27] [28] More significantly, Darwin could not account for how traits were
passed down from generation to generation. In 1865 Gregor Mendel found that traits were inherited in a predictable
manner.[29] When Mendel's work was rediscovered in 1900s, disagreements over the rate of evolution predicted by
early geneticists and biometricians led to a rift between the Mendelian and Darwinian models of evolution.

Yet it was the rediscovery of Gregor Mendel's pioneering work on the fundamentals of genetics (of which Darwin
and Wallace were unaware) by Hugo de Vries and others in the early 1900s that provided the impetus for a better
understanding of how variation occurs in plant and animal traits. That variation is the main fuel used by natural
selection to shape the wide variety of adaptive traits observed in organic life. Even though Hugo de Vries and other
early geneticists rejected gradual natural selection, their rediscovery of and subsequent work on genetics eventually
provided a solid basis on which the theory of evolution stood even more convincingly than when it was originally
proposed.[30]
The apparent contradiction between Darwin's theory of evolution by natural selection and Mendel's work was
reconciled in the 1920s and 1930s by evolutionary biologists such as J.B.S. Haldane, Sewall Wright, and particularly
Ronald Fisher, who set the foundations for the establishment of the field of population genetics. The end result was a
combination of evolution by natural selection and Mendelian inheritance, the modern evolutionary synthesis.[31] In
the 1940s, the identification of DNA as the genetic material by Oswald Avery and colleagues and the subsequent
publication of the structure of DNA by James Watson and Francis Crick in 1953, demonstrated the physical basis for
inheritance. Since then, genetics and molecular biology have become core parts of evolutionary biology and have
revolutionised the field of phylogenetics.[19]
In its early history, evolutionary biology primarily drew in scientists from traditional taxonomically oriented
disciplines, whose specialist training in particular organisms addressed general questions in evolution. As
evolutionary biology expanded as an academic discipline, particularly after the development of the modern
evolutionary synthesis, it began to draw more widely from the biological sciences.[19] Currently the study of
evolutionary biology involves scientists from fields as diverse as biochemistry, ecology, genetics and physiology,
and evolutionary concepts are used in even more distant disciplines such as psychology, medicine, philosophy and
Evolution 18

computer science. In the 21st century, current research in evolutionary biology deals with several areas where the
modern evolutionary synthesis may need modification or extension, such as assessing the relative importance of
various ideas on the unit of selection and evolvability and how to fully incorporate the findings of evolutionary
developmental biology.[32] [33]

Heredity
Evolution in organisms occurs through changes in heritable traits –
particular characteristics of an organism. In humans, for example, eye
colour is an inherited characteristic and an individual might inherit the
"brown-eye trait" from one of their parents.[34] Inherited traits are
controlled by genes and the complete set of genes within an organism's
genome is called its genotype.[35]

The complete set of observable traits that make up the structure and
behavior of an organism is called its phenotype. These traits come from the
interaction of its genotype with the environment.[36] As a result, many
aspects of an organism's phenotype are not inherited. For example,
suntanned skin comes from the interaction between a person's genotype and
sunlight; thus, suntans are not passed on to people's children. However,
some people tan more easily than others, due to differences in their
genotype; a striking example are people with the inherited trait of albinism,
who do not tan at all and are very sensitive to sunburn.[37]

Heritable traits are passed from one generation to the next via DNA, a
molecule that encodes genetic information.[35] DNA is a long polymer
composed of four types of bases. The sequence of bases along a particular
DNA molecule specify the genetic information, in a manner similar to a DNA structure. Bases are in the center,
sequence of letters spelling out a sentence. Before a cell divides, the DNA surrounded by phosphate–sugar chains in a
double helix.
is copied, so that each of the resulting two cells will inherit the DNA
sequence.

Portions of a DNA molecule that specify a single functional unit are called genes; different genes have different
sequences of bases. Within cells, the long strands of DNA form condensed structures called chromosomes. The
specific location of a DNA sequence within a chromosome is known as a locus. If the DNA sequence at a locus
varies between individuals, the different forms of this sequence are called alleles. DNA sequences can change
through mutations, producing new alleles. If a mutation occurs within a gene, the new allele may affect the trait that
the gene controls, altering the phenotype of the organism.

However, while this simple correspondence between an allele and a trait works in some cases, most traits are more
complex and are controlled by multiple interacting genes.[38] [39] The study of such complex traits is a major area of
current genetic research. Another unsolved question in genetics is whether or not epigenetics is important in
evolution. Epigenetics is when a trait is inherited without there being any change in gene sequences.[40]
Evolution 19

Variation
An individual organism's phenotype results from both its genotype and the influence from the environment it has
lived in. A substantial part of the variation in phenotypes in a population is caused by the differences between their
genotypes.[39] The modern evolutionary synthesis defines evolution as the change over time in this genetic variation.
The frequency of one particular allele will fluctuate, becoming more or less prevalent relative to other forms of that
gene. Evolutionary forces act by driving these changes in allele frequency in one direction or another. Variation
disappears when a new allele reaches the point of fixation — when it either disappears from the population or
replaces the ancestral allele entirely.[41]
Variation comes from mutations in genetic material, migration between populations (gene flow), and the reshuffling
of genes through sexual reproduction. Variation also comes from exchanges of genes between different species; for
example, through horizontal gene transfer in bacteria, and hybridization in plants.[42] Despite the constant
introduction of variation through these processes, most of the genome of a species is identical in all individuals of
that species.[43] However, even relatively small changes in genotype can lead to dramatic changes in phenotype: for
example, chimpanzees and humans differ in only about 5% of their genomes.[44]

Mutation
Random mutations constantly occur in the genomes of organisms; these mutations create
genetic variation. Mutations are changes in the DNA sequence of a cell's genome and are
caused by radiation, viruses, transposons and mutagenic chemicals, as well as errors that
occur during meiosis or DNA replication.[45] [46] [47] These mutations involve several
different types of change in DNA sequences; these can either have no effect, alter the
product of a gene, or prevent the gene from functioning. Studies in the fly Drosophila
melanogaster suggest that if a mutation changes a protein produced by a gene, this will
probably be harmful, with about 70 percent of these mutations having damaging effects,
and the remainder being either neutral or weakly beneficial.[48] Due to the damaging
effects that mutations can have on cells, organisms have evolved mechanisms such as
DNA repair to remove mutations.[45] Therefore, the optimal mutation rate for a species is
a trade-off between costs of a high mutation rate, such as deleterious mutations, and the
metabolic costs of maintaining systems to reduce the mutation rate, such as DNA repair
enzymes.[49] Viruses that use RNA as their genetic material have rapid mutation
rates,[50] which can be an advantage since these viruses will evolve constantly and
rapidly, and thus evade the defensive responses of e.g. the human immune system.[51]

Duplication of part of a Mutations can involve large sections of a chromosome becoming duplicated (usually by
chromosome genetic recombination), which can introduce extra copies of a gene into a genome.[52]
Extra copies of genes are a major source of the raw material needed for new genes to
[53]
evolve. This is important because most new genes evolve within gene families from pre-existing genes that share
common ancestors.[54] For example, the human eye uses four genes to make structures that sense light: three for
colour vision and one for night vision; all four are descended from a single ancestral gene.[55] New genes can be
created from an ancestral gene when a duplicate copy mutates and acquires a new function. This process is easier
once a gene has been duplicated because it increases the redundancy of the system; one gene in the pair can acquire a
new function while the other copy continues to perform its original function.[56] [57] Other types of mutation can
even create entirely new genes from previously noncoding DNA.[58] [59] The creation of new genes can also involve
small parts of several genes being duplicated, with these fragments then recombining to form new combinations with
new functions.[60] [61] When new genes are assembled from shuffling pre-existing parts, domains act as modules
Evolution 20

with simple independent functions, which can be mixed together creating new combinations with new and complex
functions.[62] For example, polyketide synthases are large enzymes that make antibiotics; they contain up to one
hundred independent domains that each catalyze one step in the overall process, like a step in an assembly line.[63]
Changes in chromosome number may involve even larger mutations, where segments of the DNA within
chromosomes break and then rearrange. For example, two chromosomes in the Homo genus fused to produce human
chromosome 2; this fusion did not occur in the lineage of the other apes, and they retain these separate
chromosomes.[64] In evolution, the most important role of such chromosomal rearrangements may be to accelerate
the divergence of a population into new species by making populations less likely to interbreed, and thereby
preserving genetic differences between these populations.[65]
Sequences of DNA that can move about the genome, such as transposons, make up a major fraction of the genetic
material of plants and animals, and may have been important in the evolution of genomes.[66] For example, more
than a million copies of the Alu sequence are present in the human genome, and these sequences have now been
recruited to perform functions such as regulating gene expression.[67] Another effect of these mobile DNA sequences
is that when they move within a genome, they can mutate or delete existing genes and thereby produce genetic
diversity.[46]

Sex and recombination

In asexual organisms, genes are inherited together, or linked, as they cannot mix with genes of other organisms
during reproduction. In contrast, the offspring of sexual organisms contain random mixtures of their parents'
chromosomes that are produced through independent assortment. In a related process called homologous
recombination, sexual organisms exchange DNA between two matching chromosomes.[68] Recombination and
reassortment do not alter allele frequencies, but instead change which alleles are associated with each other,
producing offspring with new combinations of alleles.[69] Sex usually increases genetic variation and may increase
the rate of evolution.[70] [71] However, asexuality is advantageous in some environments as it can evolve in
previously sexual animals.[72] Here, asexuality might allow the two sets of alleles in their genome to diverge and
gain different functions.[73]
Recombination allows even alleles that are close together in a strand of DNA to be inherited independently.
However, the rate of recombination is low (approximately two events per chromosome per generation). As a result,
genes close together on a chromosome may not always be shuffled away from each other, and genes that are close
together tend to be inherited together, a phenomenon known as linkage.[74] This tendency is measured by finding
how often two alleles occur together on a single chromosome, which is called their linkage disequilibrium. A set of
alleles that is usually inherited in a group is called a haplotype. This can be important when one allele in a particular
haplotype is strongly beneficial: natural selection can drive a selective sweep that will also cause the other alleles in
the haplotype to become more common in the population; this effect is called genetic hitchhiking.[75]
When alleles cannot be separated by recombination – such as in mammalian Y chromosomes, which pass intact from
fathers to sons – harmful mutations accumulate.[76] [77] By breaking up allele combinations, sexual reproduction
allows the removal of harmful mutations and the retention of beneficial mutations.[78] In addition, recombination and
reassortment can produce individuals with new and advantageous gene combinations. These positive effects are
balanced by the fact that sex reduces an organism's reproductive rate, can cause mutations and may separate
beneficial combinations of genes.[78] The reasons for the evolution of sexual reproduction are therefore unclear and
this question is still an active area of research in evolutionary biology,[79] [80] that has prompted ideas such as the
Red Queen hypothesis.[81]
Evolution 21

Population genetics

White peppered moth

Black morph in peppered moth evolution

From a genetic viewpoint, evolution is a generation-to-generation change in the frequencies of alleles within a
population that shares a common gene pool.[82] A population is a localised group of individuals belonging to the
same species. For example, all of the moths of the same species living in an isolated forest represent a population. A
single gene in this population may have several alternate forms, which account for variations between the
phenotypes of the organisms. An example might be a gene for colouration in moths that has two alleles: black and
white. A gene pool is the complete set of alleles for a gene in a single population; the allele frequency measures the
fraction of the gene pool composed of a single allele (for example, what fraction of moth colouration genes are the
black allele). Evolution occurs when there are changes in the frequencies of alleles within a population of
interbreeding organisms; for example, the allele for black colour in a population of moths becoming more common.
To understand the mechanisms that cause a population to evolve, it is useful to consider what conditions are required
for a population not to evolve. The Hardy-Weinberg principle states that the frequencies of alleles (variations in a
gene) in a sufficiently large population will remain constant if the only forces acting on that population are the
random reshuffling of alleles during the formation of the sperm or egg, and the random combination of the alleles in
these sex cells during fertilization.[83] Such a population is said to be in Hardy-Weinberg equilibrium; it is not
evolving.[84]
Evolution 22

Gene flow
Gene flow is the exchange of genes between
populations, which are usually of the same species.[86]
Examples of gene flow within a species include the
migration and then breeding of organisms, or the
exchange of pollen. Gene transfer between species
includes the formation of hybrid organisms and
horizontal gene transfer.

Migration into or out of a population can change allele

frequencies, as well as introducing genetic variation
into a population. Immigration may add new genetic
material to the established gene pool of a population.
Conversely, emigration may remove genetic material.
When they mature, male lions leave the pride where they were born
and take over a new pride to mate, causing gene flow between As barriers to reproduction between two diverging
[85]
prides. populations are required for the populations to become
new species, gene flow may slow this process by
spreading genetic differences between the populations. Gene flow is hindered by mountain ranges, oceans and
deserts or even man-made structures such as the Great Wall of China, which has hindered the flow of plant genes.[87]

Depending on how far two species have diverged since their most recent common ancestor, it may still be possible
for them to produce offspring, as with horses and donkeys mating to produce mules.[88] Such hybrids are generally
infertile, due to the two different sets of chromosomes being unable to pair up during meiosis. In this case, closely
related species may regularly interbreed, but hybrids will be selected against and the species will remain distinct.
However, viable hybrids are occasionally formed and these new species can either have properties intermediate
between their parent species, or possess a totally new phenotype.[89] The importance of hybridization in creating new
species of animals is unclear, although cases have been seen in many types of animals,[90] with the gray tree frog
being a particularly well-studied example.[91]

Hybridization is, however, an important means of speciation in plants, since polyploidy (having more than two
copies of each chromosome) is tolerated in plants more readily than in animals.[92] [93] Polyploidy is important in
hybrids as it allows reproduction, with the two different sets of chromosomes each being able to pair with an
identical partner during meiosis.[94] Polyploids also have more genetic diversity, which allows them to avoid
inbreeding depression in small populations.[95]
Horizontal gene transfer is the transfer of genetic material from one organism to another organism that is not its
offspring; this is most common among bacteria.[96] In medicine, this contributes to the spread of antibiotic resistance,
as when one bacteria acquires resistance genes it can rapidly transfer them to other species.[97] Horizontal transfer of
genes from bacteria to eukaryotes such as the yeast Saccharomyces cerevisiae and the adzuki bean beetle
Callosobruchus chinensis may also have occurred.[98] [99] An example of larger-scale transfers are the eukaryotic
bdelloid rotifers, which appear to have received a range of genes from bacteria, fungi, and plants.[100] Viruses can
also carry DNA between organisms, allowing transfer of genes even across biological domains.[101] Large-scale gene
transfer has also occurred between the ancestors of eukaryotic cells and prokaryotes, during the acquisition of
chloroplasts and mitochondria.[102]
Evolution 23

Mechanisms
The two main mechanisms that produce evolution are natural selection and genetic drift. Natural selection is the
process which favors genes that aid survival and reproduction. Genetic drift is the random change in the frequency of
alleles, caused by the random sampling of a generation's genes during reproduction. The relative importance of
natural selection and genetic drift in a population varies depending on the strength of the selection and the effective
population size, which is the number of individuals capable of breeding.[103] Natural selection usually predominates
in large populations, whereas genetic drift dominates in small populations. The dominance of genetic drift in small
populations can even lead to the fixation of slightly deleterious mutations.[104] As a result, changing population size
can dramatically influence the course of evolution. Population bottlenecks, where the population shrinks temporarily
and therefore loses genetic variation, result in a more uniform population.[41]

Natural selection
Natural selection is the process by which
genetic mutations that enhance reproduction
become, and remain, more common in
successive generations of a population. It
has often been called a "self-evident"
mechanism because it necessarily follows
from three simple facts:

• Heritable variation exists within

populations of organisms.
• Organisms produce more offspring than
can survive.
• These offspring vary in their ability to
survive and reproduce.
These conditions produce competition
between organisms for survival and
reproduction. Consequently, organisms with
traits that give them an advantage over their Natural selection of a population for dark colouration.
competitors pass these advantageous traits
on, while traits that do not confer an advantage are not passed on to the next generation.[105]

The central concept of natural selection is the evolutionary fitness of an organism.[106] Fitness is measured by an
organism's ability to survive and reproduce, which determines the size of its genetic contribution to the next
generation.[106] However, fitness is not the same as the total number of offspring: instead fitness is indicated by the
proportion of subsequent generations that carry an organism's genes.[107] For example, if an organism could survive
well and reproduce rapidly, but its offspring were all too small and weak to survive, this organism would make little
genetic contribution to future generations and would thus have low fitness.[106]
If an allele increases fitness more than the other alleles of that gene, then with each generation this allele will become
more common within the population. These traits are said to be "selected for". Examples of traits that can increase
fitness are enhanced survival, and increased fecundity. Conversely, the lower fitness caused by having a less
beneficial or deleterious allele results in this allele becoming rarer — they are "selected against".[108] Importantly,
the fitness of an allele is not a fixed characteristic; if the environment changes, previously neutral or harmful traits
may become beneficial and previously beneficial traits become harmful.[1] However, even if the direction of
selection does reverse in this way, traits that were lost in the past may not re-evolve in an identical form (see Dollo's
law).[109] [110]
Evolution 24

Natural selection within a population for a trait that can

vary across a range of values, such as height, can be
categorised into three different types. The first is
directional selection, which is a shift in the average
value of a trait over time — for example, organisms
slowly getting taller.[111] Secondly, disruptive selection
is selection for extreme trait values and often results in
two different values becoming most common, with
selection against the average value. This would be
when either short or tall organisms had an advantage,
but not those of medium height. Finally, in stabilizing
selection there is selection against extreme trait values
on both ends, which causes a decrease in variance
around the average value and less diversity.[105] [112]
This would, for example, cause organisms to slowly
become all the same height.

A special case of natural selection is sexual selection,

which is selection for any trait that increases mating
success by increasing the attractiveness of an organism
to potential mates.[113] Traits that evolved through
sexual selection are particularly prominent in males of
A chart showing three types of selection. 1.Disruptive selection
some animal species, despite traits such as cumbersome
2.Stabilizing selection 3.Directional selection
antlers, mating calls or bright colours that attract
predators, decreasing the survival of individual
males.[114] This survival disadvantage is balanced by higher reproductive success in males that show these hard to
fake, sexually selected traits.[115]

Natural selection most generally makes nature the measure against which individuals, and individual traits, are more
or less likely to survive. "Nature" in this sense refers to an ecosystem, that is, a system in which organisms interact
with every other element, physical as well as biological, in their local environment. Eugene Odum, a founder of
ecology, defined an ecosystem as: "Any unit that includes all of the organisms...in a given area interacting with the
physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material
cycles (ie: exchange of materials between living and nonliving parts) within the system."[116] Each population within
an ecosystem occupies a distinct niche, or position, with distinct relationships to other parts of the system. These
relationships involve the life history of the organism, its position in the food chain, and its geographic range. This
broad understanding of nature enables scientists to delineate specific forces which, together, comprise natural
selection.

An active area of research is the unit of selection, with natural selection being proposed to work at the level of genes,
cells, individual organisms, groups of organisms and species.[117] [118] None of these are mutually exclusive and
selection can act on multiple levels simultaneously.[119] An example of selection occurring below the level of the
individual organism are genes called transposons, which can replicate and spread throughout a genome.[120]
Selection at a level above the individual, such as group selection, may allow the evolution of co-operation, as
discussed below.[121]
Evolution 25

Genetic drift
Genetic drift is the change in allele frequency from one
generation to the next that occurs because alleles in
offspring are a random sample of those in the parents,
as well as from the role that chance plays in
determining whether a given individual will survive
and reproduce. In mathematical terms, alleles are
subject to sampling error. As a result, when selective
forces are absent or relatively weak, allele frequencies
tend to "drift" upward or downward randomly (in a
random walk). This drift halts when an allele
eventually becomes fixed, either by disappearing from
the population, or replacing the other alleles entirely.
Genetic drift may therefore eliminate some alleles from
a population due to chance alone. Even in the absence
of selective forces, genetic drift can cause two separate
populations that began with the same genetic structure
to drift apart into two divergent populations with
different sets of alleles.[122] Simulation of genetic drift of 20 unlinked alleles in populations of 10
(top) and 100 (bottom). Drift to fixation is more rapid in the smaller
population.
The time for an allele to become fixed by genetic drift
depends on population size, with fixation occurring
more rapidly in smaller populations.[123] The precise measure of population that is important is called the effective
population size. The effective population is always smaller than the total population since it takes into account
factors such as the level of inbreeding, the number of animals that are too old or young to breed, and the lower
probability of animals that live far apart managing to mate with each other.[124]

An example when genetic drift is probably of central importance in determining a trait is the loss of pigments from
animals that live in caves, a change that produces no obvious advantage or disadvantage in complete darkness.[125]
However, it is usually difficult to measure the relative importance of selection and drift,[126] so the comparative
importance of these two forces in driving evolutionary change is an area of current research.[127] These
investigations were prompted by the neutral theory of molecular evolution, which proposed that most evolutionary
changes are the result of the fixation of neutral mutations that do not have any immediate effects on the fitness of an
organism.[128] Hence, in this model, most genetic changes in a population are the result of constant mutation
pressure and genetic drift.[129] This form of the neutral theory is now largely abandoned, since it does not seem to fit
the genetic variation seen in nature.[130] [131] However, a more recent and better-supported version of this model is
the nearly neutral theory, where most mutations only have small effects on fitness.[105]

Outcomes
Evolution influences every aspect of the form and behavior of organisms. Most prominent are the specific behavioral
and physical adaptations that are the outcome of natural selection. These adaptations increase fitness by aiding
activities such as finding food, avoiding predators or attracting mates. Organisms can also respond to selection by
co-operating with each other, usually by aiding their relatives or engaging in mutually beneficial symbiosis. In the
longer term, evolution produces new species through splitting ancestral populations of organisms into new groups
that cannot or will not interbreed.
These outcomes of evolution are sometimes divided into macroevolution, which is evolution that occurs at or above
the level of species, such as extinction and speciation, and microevolution, which is smaller evolutionary changes,
Evolution 26

such as adaptations, within a species or population.[132] In general, macroevolution is regarded as the outcome of
long periods of microevolution.[133] Thus, the distinction between micro- and macroevolution is not a fundamental
one – the difference is simply the time involved.[134] However, in macroevolution, the traits of the entire species may
be important. For instance, a large amount of variation among individuals allows a species to rapidly adapt to new
habitats, lessening the chance of it going extinct, while a wide geographic range increases the chance of speciation,
by making it more likely that part of the population will become isolated. In this sense, microevolution and
macroevolution might involve selection at different levels – with microevolution acting on genes and organisms,
versus macroevolutionary processes such as species selection acting on entire species and affecting their rates of
speciation and extinction.[135] [136] [137]
A common misconception is that evolution has goals or long-term plans; realistically however, evolution has no
long-term goal and does not necessarily produce greater complexity.[138] [139] Although complex species have
evolved, they occur as a side effect of the overall number of organisms increasing, and simple forms of life still
remain more common in the biosphere.[140] For example, the overwhelming majority of species are microscopic
prokaryotes, which form about half the world's biomass despite their small size,[141] and constitute the vast majority
of Earth's biodiversity.[142] Simple organisms have therefore been the dominant form of life on Earth throughout its
history and continue to be the main form of life up to the present day, with complex life only appearing more diverse
because it is more noticeable.[143] Indeed, the evolution of microorganisms is particularly important to modern
evolutionary research, since their rapid reproduction allows the study of experimental evolution and the observation
of evolution and adaptation in real time.[144] [145]

Adaptation
Adaptation is one of the basic phenomena of biology,[146] and is the process whereby an organism becomes better
suited to its habitat.[147] [148] Also, the term adaptation may refer to a trait that is important for an organism's
survival. For example, the adaptation of horses' teeth to the grinding of grass, or the ability of horses to run fast and
escape predators. By using the term adaptation for the evolutionary process, and adaptive trait for the product (the
bodily part or function), the two senses of the word may be distinguished. Adaptations are produced by natural
selection.[149] The following definitions are due to Theodosius Dobzhansky.
1. Adaptation is the evolutionary process whereby an organism becomes better able to live in its habitat or
habitats.[150]
2. Adaptedness is the state of being adapted: the degree to which an organism is able to live and reproduce in a
given set of habitats.[151]
3. An adaptive trait is an aspect of the developmental pattern of the organism which enables or enhances the
probability of that organism surviving and reproducing.[152]
Adaptation may cause either the gain of a new feature, or the loss of an ancestral feature. An example that shows
both types of change is bacterial adaptation to antibiotic selection, with genetic changes causing antibiotic resistance
by both modifying the target of the drug, or increasing the activity of transporters that pump the drug out of the
cell.[153] Other striking examples are the bacteria Escherichia coli evolving the ability to use citric acid as a nutrient
in a long-term laboratory experiment,[154] Flavobacterium evolving a novel enzyme that allows these bacteria to
grow on the by-products of nylon manufacturing,[155] [156] and the soil bacterium Sphingobium evolving an entirely
new metabolic pathway that degrades the synthetic pesticide pentachlorophenol.[157] [158] An interesting but still
controversial idea is that some adaptations might increase the ability of organisms to generate genetic diversity and
adapt by natural selection (increasing organisms' evolvability).[159] [160]
Evolution 27

Adaptation occurs through the gradual

modification of existing structures.
Consequently, structures with similar
internal organization may have
different functions in related
organisms. This is the result of a single
ancestral structure being adapted to A baleen whale skeleton, a and b label flipper bones, which were adapted from front leg
function in different ways. The bones bones: while c indicates vestigial leg bones, suggesting an adaptation from land to
[161]
within bat wings, for example, are very sea.

similar to those in mice feet and

primate hands, due to the descent of all these structures from a common mammalian ancestor.[162] However, since all
living organisms are related to some extent,[163] even organs that appear to have little or no structural similarity, such
as arthropod, squid and vertebrate eyes, or the limbs and wings of arthropods and vertebrates, can depend on a
common set of homologous genes that control their assembly and function; this is called deep homology.[164] [165]

During adaptation, some structures may lose their original function and become vestigial structures.[166] Such
structures may have little or no function in a current species, yet have a clear function in ancestral species, or other
closely related species. Examples include pseudogenes,[167] the non-functional remains of eyes in blind
cave-dwelling fish,[168] wings in flightless birds,[169] and the presence of hip bones in whales and snakes.[161]
Examples of vestigial structures in humans include wisdom teeth,[170] the coccyx,[166] the vermiform appendix,[166]
and other behavioral vestiges such as goose bumps,[171] and primitive reflexes.[172] [173] [174] [175]
However, many traits that appear to be simple adaptations are in fact exaptations: structures originally adapted for
one function, but which coincidentally became somewhat useful for some other function in the process.[176] One
example is the African lizard Holaspis guentheri, which developed an extremely flat head for hiding in crevices, as
can be seen by looking at its near relatives. However, in this species, the head has become so flattened that it assists
in gliding from tree to tree—an exaptation.[176] Within cells, molecular machines such as the bacterial flagella[177]
and protein sorting machinery[178] evolved by the recruitment of several pre-existing proteins that previously had
different functions.[132] Another example is the recruitment of enzymes from glycolysis and xenobiotic metabolism
to serve as structural proteins called crystallins within the lenses of organisms' eyes.[179] [180]
A critical principle of ecology is that of competitive exclusion: no two species can occupy the same niche in the
same environment for a long time.[181] Consequently, natural selection will tend to force species to adapt to different
ecological niches. This may mean that, for example, two species of cichlid fish adapt to live in different habitats,
which will minimise the competition between them for food.[182]
An area of current investigation in evolutionary developmental biology is the developmental basis of adaptations and
exaptations.[183] This research addresses the origin and evolution of embryonic development and how modifications
of development and developmental processes produce novel features.[184] These studies have shown that evolution
can alter development to create new structures, such as embryonic bone structures that develop into the jaw in other
animals instead forming part of the middle ear in mammals.[185] It is also possible for structures that have been lost
in evolution to reappear due to changes in developmental genes, such as a mutation in chickens causing embryos to
grow teeth similar to those of crocodiles.[186] It is now becoming clear that most alterations in the form of organisms
are due to changes in a small set of conserved genes.[187]
Evolution 28

Co-evolution
Interactions between organisms can produce both conflict and
co-operation. When the interaction is between pairs of species, such as
a pathogen and a host, or a predator and its prey, these species can
develop matched sets of adaptations. Here, the evolution of one species
causes adaptations in a second species. These changes in the second
species then, in turn, cause new adaptations in the first species. This
cycle of selection and response is called co-evolution.[188] An example
is the production of tetrodotoxin in the rough-skinned newt and the
evolution of tetrodotoxin resistance in its predator, the common garter
snake. In this predator-prey pair, an evolutionary arms race has
Common garter snake (Thamnophis sirtalis
produced high levels of toxin in the newt and correspondingly high sirtalis) which has evolved resistance to
levels of toxin resistance in the snake.[189] tetrodotoxin in its amphibian prey.

Co-operation
However, not all interactions between species involve conflict.[190] Many cases of mutually beneficial interactions
have evolved. For instance, an extreme cooperation exists between plants and the mycorrhizal fungi that grow on
their roots and aid the plant in absorbing nutrients from the soil.[191] This is a reciprocal relationship as the plants
provide the fungi with sugars from photosynthesis. Here, the fungi actually grow inside plant cells, allowing them to
exchange nutrients with their hosts, while sending signals that suppress the plant immune system.[192]
Coalitions between organisms of the same species have also evolved. An extreme case is the eusociality found in
social insects, such as bees, termites and ants, where sterile insects feed and guard the small number of organisms in
a colony that are able to reproduce. On an even smaller scale, the somatic cells that make up the body of an animal
limit their reproduction so they can maintain a stable organism, which then supports a small number of the animal's
germ cells to produce offspring. Here, somatic cells respond to specific signals that instruct them whether to grow,
remain as they are, or die. If cells ignore these signals and multiply inappropriately, their uncontrolled growth causes
cancer.[45]
Such cooperation within species may have evolved through the process of kin selection, which is where one
organism acts to help raise a relative's offspring.[193] This activity is selected for because if the helping individual
contains alleles which promote the helping activity, it is likely that its kin will also contain these alleles and thus
those alleles will be passed on.[194] Other processes that may promote cooperation include group selection, where
cooperation provides benefits to a group of organisms.[195]
Evolution 29

Speciation
Speciation is the process where a
species diverges into two or more
descendant species.[196] Evolutionary
biologists view species as statistical
phenomena and not categories or
types. This view is counterintuitive
since the classical idea of species is
still widely held, with a species seen as
a class of organisms exemplified by a
"type specimen" that bears all the traits
common to this species. Instead, a
species is now defined as a separately
evolving lineage that forms a single
gene pool. Although properties such as
genetics and morphology are used to
help separate closely related lineages,
this definition has fuzzy
[197]
boundaries. Indeed, the exact
The four mechanisms of speciation. definition of the term "species" is still
controversial, particularly in
[198] [199]
prokaryotes, and this is called the species problem. Biologists have proposed a range of more precise
definitions, but the definition used is a pragmatic choice that depends on the particularities of the species
concerned.[199] Typically the actual focus on biological study is the population, an observable interacting group of
organisms, rather than a species, an observable similar group of individuals.

Speciation has been observed multiple times under both controlled laboratory conditions and in nature.[200] In
sexually reproducing organisms, speciation results from reproductive isolation followed by genealogical divergence.
There are four mechanisms for speciation. The most common in animals is allopatric speciation, which occurs in
populations initially isolated geographically, such as by habitat fragmentation or migration. Selection under these
conditions can produce very rapid changes in the appearance and behaviour of organisms.[201] [202] As selection and
drift act independently on populations isolated from the rest of their species, separation may eventually produce
organisms that cannot interbreed.[203]
The second mechanism of speciation is peripatric speciation, which occurs when small populations of organisms
become isolated in a new environment. This differs from allopatric speciation in that the isolated populations are
numerically much smaller than the parental population. Here, the founder effect causes rapid speciation through both
rapid genetic drift and selection on a small gene pool.[204]
The third mechanism of speciation is parapatric speciation. This is similar to peripatric speciation in that a small
population enters a new habitat, but differs in that there is no physical separation between these two populations.
Instead, speciation results from the evolution of mechanisms that reduce gene flow between the two populations.[196]
Generally this occurs when there has been a drastic change in the environment within the parental species' habitat.
One example is the grass Anthoxanthum odoratum, which can undergo parapatric speciation in response to localised
metal pollution from mines.[205] Here, plants evolve that have resistance to high levels of metals in the soil. Selection
against interbreeding with the metal-sensitive parental population produced a gradual change in the flowering time of
the metal-resistant plants, which eventually produced complete reproductive isolation. Selection against hybrids
between the two populations may cause reinforcement, which is the evolution of traits that promote mating within a
species, as well as character displacement, which is when two species become more distinct in appearance.[206]
Evolution 30

Finally, in sympatric speciation species diverge without geographic

isolation or changes in habitat. This form is rare since even a small
amount of gene flow may remove genetic differences between parts of
a population.[207] Generally, sympatric speciation in animals requires
the evolution of both genetic differences and non-random mating, to
allow reproductive isolation to evolve.[208]

One type of sympatric speciation involves cross-breeding of two

related species to produce a new hybrid species. This is not common in
animals as animal hybrids are usually sterile. This is because during
meiosis the homologous chromosomes from each parent are from
different species and cannot successfully pair. However, it is more
Geographical isolation of finches on the
common in plants because plants often double their number of Galápagos Islands produced over a dozen new
chromosomes, to form polyploids.[209] This allows the chromosomes species.
from each parental species to form matching pairs during meiosis,
since each parent's chromosomes are represented by a pair already.[210] An example of such a speciation event is
when the plant species Arabidopsis thaliana and Arabidopsis arenosa cross-bred to give the new species Arabidopsis
suecica.[211] This happened about 20,000 years ago,[212] and the speciation process has been repeated in the
laboratory, which allows the study of the genetic mechanisms involved in this process.[213] Indeed, chromosome
doubling within a species may be a common cause of reproductive isolation, as half the doubled chromosomes will
be unmatched when breeding with undoubled organisms.[93]

Speciation events are important in the theory of punctuated equilibrium, which accounts for the pattern in the fossil
record of short "bursts" of evolution interspersed with relatively long periods of stasis, where species remain
relatively unchanged.[214] In this theory, speciation and rapid evolution are linked, with natural selection and genetic
drift acting most strongly on organisms undergoing speciation in novel habitats or small populations. As a result, the
periods of stasis in the fossil record correspond to the parental population, and the organisms undergoing speciation
and rapid evolution are found in small populations or geographically restricted habitats, and therefore rarely being
preserved as fossils.[215]

Extinction
Extinction is the disappearance of an entire species.
Extinction is not an unusual event, as species regularly
appear through speciation, and disappear through
extinction.[216] Nearly all animal and plant species that have
lived on Earth are now extinct,[217] and extinction appears
to be the ultimate fate of all species.[218] These extinctions
have happened continuously throughout the history of life,
although the rate of extinction spikes in occasional mass
extinction events.[219] The Cretaceous–Tertiary extinction
event, during which the non-avian dinosaurs went extinct, is
Tyrannosaurus rex. Non-avian dinosaurs died out in the
Cretaceous–Tertiary extinction event at the end of the the most well-known, but the earlier Permian–Triassic
Cretaceous period. extinction event was even more severe, with approximately
96 percent of species driven to extinction.[219] The
Holocene extinction event is an ongoing mass extinction associated with humanity's expansion across the globe over
the past few thousand years. Present-day extinction rates are 100–1000 times greater than the background rate, and
Evolution 31

up to 30 percent of species may be extinct by the mid 21st century.[220] Human activities are now the primary cause
of the ongoing extinction event;[221] global warming may further accelerate it in the future.[222]
The role of extinction in evolution is not very well understood and may depend on which type of extinction is
considered.[219] The causes of the continuous "low-level" extinction events, which form the majority of extinctions,
may be the result of competition between species for limited resources (competitive exclusion).[19] If one species can
out-compete another, this could produce species selection, with the fitter species surviving and the other species
being driven to extinction.[117] The intermittent mass extinctions are also important, but instead of acting as a
selective force, they drastically reduce diversity in a nonspecific manner and promote bursts of rapid evolution and
speciation in survivors.[223]

Evolutionary history of life

Origin of life
The origin of life is a necessary precursor for biological evolution, but understanding that evolution occurred once
organisms appeared and investigating how this happens does not depend on understanding exactly how life
began.[224] The current scientific consensus is that the complex biochemistry that makes up life came from simpler
chemical reactions, but it is unclear how this occurred.[225] Not much is certain about the earliest developments in
life, the structure of the first living things, or the identity and nature of any last universal common ancestor or
ancestral gene pool.[226] [227] Consequently, there is no scientific consensus on how life began, but proposals include
self-replicating molecules such as RNA,[228] and the assembly of simple cells.[229]

Common descent
All organisms on Earth are descended
from a common ancestor or ancestral
gene pool.[163] [230] Current species are
a stage in the process of evolution, with
their diversity the product of a long
series of speciation and extinction
events.[231] The common descent of
organisms was first deduced from four
simple facts about organisms: First,
they have geographic distributions that
cannot be explained by local adaptation.
Second, the diversity of life is not a set The hominoids are descendants of a common ancestor.
of completely unique organisms, but
organisms that share morphological similarities. Third, vestigial traits with no clear purpose resemble functional
ancestral traits, and finally, that organisms can be classified using these similarities into a hierarchy of nested
groups – similar to a family tree.[14] However, modern research has suggested that, due to horizontal gene transfer,
this "tree of life" may be more complicated than a simple branching tree since some genes have spread independently
between distantly related species.[232] [233]

Past species have also left records of their evolutionary history. Fossils, along with the comparative anatomy of
present-day organisms, constitute the morphological, or anatomical, record.[234] By comparing the anatomies of both
modern and extinct species, paleontologists can infer the lineages of those species. However, this approach is most
successful for organisms that had hard body parts, such as shells, bones or teeth. Further, as prokaryotes such as
bacteria and archaea share a limited set of common morphologies, their fossils do not provide information on their
ancestry.
Evolution 32

More recently, evidence for common descent has come from the study of biochemical similarities between
organisms. For example, all living cells use the same basic set of nucleotides and amino acids.[235] The development
of molecular genetics has revealed the record of evolution left in organisms' genomes: dating when species diverged
through the molecular clock produced by mutations.[236] For example, these DNA sequence comparisons have
revealed that humans and chimpanzees share 96% of their genomes and analyzing the few areas where they differ
helps shed light on when the common ancestor of these species existed.[237]

Evolution of life
Despite the uncertainty on how life
began, it is generally accepted that
prokaryotes inhabited the Earth from
approximately 3–4 billion years
ago.[238] [239] No obvious changes in
morphology or cellular organization
occurred in these organisms over the
next few billion years.[240]

The eukaryotes were the next major

change in cell structure. These came
from ancient bacteria being engulfed
by the ancestors of eukaryotic cells, in
a cooperative association called
Evolutionary tree showing the divergence of modern species from their common ancestor endosymbiosis.[102] [241] The engulfed
in the center.Ciccarelli FD, Doerks T, von Mering C, Creevey CJ, Snel B, Bork P (2006).
bacteria and the host cell then
"Toward automatic reconstruction of a highly resolved tree of life". Science 311 (5765):
1283–87. doi:10.1126/science.1123061. PMID 16513982.  The three domains are
underwent co-evolution, with the
coloured, with bacteria blue, archaea green, and eukaryotes red. bacteria evolving into either
mitochondria or hydrogenosomes.[242]
An independent second engulfment of cyanobacterial-like organisms led to the formation of chloroplasts in algae and
plants.[243] It is unknown when the first eukaryotic cells appeared though they first emerged between 1.6 – 2.7
billion years ago.

The history of life was that of the unicellular eukaryotes, prokaryotes, and archaea until about 610 million years ago
when multicellular organisms began to appear in the oceans in the Ediacaran period.[238] [244] The evolution of
multicellularity occurred in multiple independent events, in organisms as diverse as sponges, brown algae,
cyanobacteria, slime moulds and myxobacteria.[245]
Soon after the emergence of these first multicellular organisms, a remarkable amount of biological diversity
appeared over approximately 10 million years, in an event called the Cambrian explosion. Here, the majority of
types of modern animals appeared in the fossil record, as well as unique lineages that subsequently became
extinct.[246] Various triggers for the Cambrian explosion have been proposed, including the accumulation of oxygen
in the atmosphere from photosynthesis.[247] About 500 million years ago, plants and fungi colonised the land, and
were soon followed by arthropods and other animals.[248] Insects were particularly successful and even today make
up the majority of animal species.[249] Amphibians first appeared around 300 million years ago, followed by early
amniotes, then mammals around 200 million years ago and birds around 100 million years ago (both from
"reptile"-like lineages). However, despite the evolution of these large animals, smaller organisms similar to the types
that evolved early in this process continue to be highly successful and dominate the Earth, with the majority of both
biomass and species being prokaryotes.[142]
Evolution 33

Applications
Evolutionary biology, and in particular the understanding of how organisms evolve through natural selection, is an
area of science with many practical applications.[250] A major technological application of evolution is artificial
selection, which is the intentional selection of certain traits in a population of organisms. Humans have used artificial
selection for thousands of years in the domestication of plants and animals.[251] More recently, such selection has
become a vital part of genetic engineering, with selectable markers such as antibiotic resistance genes being used to
manipulate DNA in molecular biology. It is also possible to use repeated rounds of mutation and selection to evolve
proteins with particular properties, such as modified enzymes or new antibodies, in a process called directed
evolution.[252]
Understanding the changes that have occurred during organism's evolution can reveal the genes needed to construct
parts of the body, genes which may be involved in human genetic disorders.[253] For example, the Mexican tetra is
an albino cavefish that lost its eyesight during evolution. Breeding together different populations of this blind fish
produced some offspring with functional eyes, since different mutations had occurred in the isolated populations that
had evolved in different caves.[254] This helped identify genes required for vision and pigmentation, such as
crystallins and the melanocortin 1 receptor.[255] Similarly, comparing the genome of the Antarctic icefish, which
lacks red blood cells, to close relatives such as the Antarctic rockcod revealed genes needed to make these blood
cells.[256]
As evolution can produce highly optimised processes and networks, it has many applications in computer science.
Here, simulations of evolution using evolutionary algorithms and artificial life started with the work of Nils Aall
Barricelli in the 1960s, and was extended by Alex Fraser, who published a series of papers on simulation of artificial
selection.[257] Artificial evolution became a widely recognised optimization method as a result of the work of Ingo
Rechenberg in the 1960s and early 1970s, who used evolution strategies to solve complex engineering problems.[258]
Genetic algorithms in particular became popular through the writing of John Holland.[259] As academic interest
grew, dramatic increases in the power of computers allowed practical applications, including the automatic evolution
of computer programs.[260] Evolutionary algorithms are now used to solve multi-dimensional problems more
efficiently than software produced by human designers, and also to optimise the design of systems.[261]

Social and cultural responses

In the 19th century, particularly after the publication of On the Origin of
Species in 1859, the idea that life had evolved was an active source of
academic debate centered on the philosophical, social and religious
implications of evolution. Nowadays, the fact that organisms evolve is
uncontested in the scientific literature and the modern evolutionary synthesis
is widely accepted by scientists.[19] However, evolution remains a contentious
concept for some theists.[263]

While various religions and denominations have reconciled their beliefs with
evolution through concepts such as theistic evolution, there are creationists
who believe that evolution is contradicted by the creation myths found in their
respective religions and who raise various objections to evolution.[132] [264]
[265]
As had been demonstrated by responses to the publication of Vestiges of
the Natural History of Creation in 1844, the most controversial aspect of As evolution became widely accepted in
evolutionary biology is the implication of human evolution that human mental the 1870s, caricatures of Charles Darwin
and moral faculties, which had been thought purely spiritual, are not distinctly with an ape or monkey body symbolised
[262]
evolution.
Evolution 34

separated from those of other animals.[13] In some countries—notably the United States—these tensions between
science and religion have fueled the current creation-evolution controversy, a religious conflict focusing on politics
and public education.[266] While other scientific fields such as cosmology[267] and Earth science[268] also conflict
with literal interpretations of many religious texts, evolutionary biology experiences significantly more opposition
from religious literalists.
The teaching of evolution in American secondary school biology classes was uncommon in most of the first half of
the 20th century. The Scopes Trial decision of 1925 caused the subject to become very rare in American secondary
biology textbooks for a generation, but it was gradually re-introduced about a generation later and legally protected
with the 1968 Epperson v. Arkansas decision. Since then, the competing religious belief of creationism was legally
disallowed in secondary school curricula in various decisions in the 1970s and 1980s, but it returned in the form of
intelligent design, to be excluded once again in the 2005 Kitzmiller v. Dover Area School District case.[269]
Another example somewhat associated with evolutionary theory that is now widely regarded as unwarranted is
"Social Darwinism", a derogatory term associated with the 19th century Malthusian theory developed by Whig
philosopher Herbert Spencer. It was later expanded by others into ideas about "survival of the fittest" in commerce
and human societies as a whole, and led to claims that social inequality, sexism, racism, and imperialism were
justified.[270] However, these ideas contradict Darwin's own views, and contemporary scientists and philosophers
consider these ideas to be neither mandated by evolutionary theory nor supported by data.[271] [272] [273]

See also
• Current research in evolutionary biology

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Evolution and the Meanings of Life. Simon & Schuster. ISBN 978-0684824710.
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[265] Hameed, Salman (2008-12-12). "Science and Religion: Bracing for Islamic Creationism" (http:/ / helios. hampshire. edu/ ~sahCS/
Hameed-Science-Creationism. pdf). Science 322 (5908): 1637–1638. doi:10.1126/science.1163672. PMID 19074331. . Retrieved 2009.
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[267] Spergel, D. N.; Verde, L.; Peiris, H. V.; Komatsu, E.; Nolta, M. R.; Bennett, C. L.; Halpern, M.; Hinshaw, G. et al. (2003). "First-Year
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Harvard University Press. ISBN 978-0674445574.
[271] Darwin strongly disagreed with attempts by Herbert Spencer and others to extrapolate evolutionary ideas to all possible subjects; see
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[273] Gowaty, Patricia Adair (1997). Feminism and evolutionary biology: boundaries, intersections, and frontiers. London: Chapman & Hall.
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Evolution 45

Further reading
Introductory reading
• Carroll, S. (2005). Endless Forms Most Beautiful. New York: W.W. Norton. ISBN 0-393-06016-0.
• Charlesworth, C.B. and Charlesworth, D. (2003). Evolution. Oxfordshire: Oxford University Press.
ISBN 0-192-80251-8.
• Dawkins, R. (2006). The Selfish Gene: 30th Anniversary Edition. Oxford University Press. ISBN 0199291152.
• Gould, S.J. (1989). Wonderful Life: The Burgess Shale and the Nature of History. New York: W.W. Norton.
ISBN 0-393-30700-X.
• Jones, S. (2001). Almost Like a Whale: The Origin of Species Updated. (American title: Darwin's Ghost). New
York: Ballantine Books. ISBN 0-345-42277-5.
• Mader, Sylvia S. (2007). Biology. Murray P. Pendarvis (9th ed.). McGraw Hill. ISBN 9780073258393.
• Maynard Smith, J. (1993). The Theory of Evolution: Canto Edition. Cambridge University Press.
ISBN 0-521-45128-0.
• Pallen, M.J. (2009). The Rough Guide to Evolution. Rough Guides. ISBN 978-1-85828-946-5.
• Smith, C.B. and Sullivan, C. (2007). The Top 10 Myths about Evolution. Prometheus Books.
ISBN 978-1-59102-479-8.
History of evolutionary thought
• Darwin, Charles (1859). On the Origin of Species (http://darwin-online.org.uk/content/
frameset?itemID=F373&viewtype=text&pageseq=1) (1st ed.). London: John Murray. ISBN 0801413192.
• Larson, E.J. (2004). Evolution: The Remarkable History of a Scientific Theory. New York: Modern Library.
ISBN 0-679-64288-9.
• Zimmer, C. (2001). Evolution: The Triumph of an Idea. London: HarperCollins. ISBN 0-060-19906-7.
Advanced reading
• Barton, N.H., Briggs, D.E.G., Eisen, J.A., Goldstein, D.B. and Patel, N.H. (2007). Evolution. Cold Spring Harbor
Laboratory Press. ISBN 0-879-69684-2.
• Coyne, J.A. and Orr, H.A. (2004). Speciation. Sunderland: Sinauer Associates. ISBN 0-878-93089-2.
• Futuyma, D.J. (2005). Evolution. Sunderland: Sinauer Associates. ISBN 0-878-93187-2.
• Gould, S.J. (2002). The Structure of Evolutionary Theory. Cambridge: Belknap Press (Harvard University Press).
ISBN 0-674-00613-5.
• Maynard Smith, J. and Szathmáry, E. (1997). The Major Transitions in Evolution. Oxfordshire: Oxford
University Press. ISBN 0-198-50294-X.
• Mayr, E. (2001). What Evolution Is. New York: Basic Books. ISBN 0-465-04426-3.
• Olson, Wendy; Hall, Brian Keith (2003). Keywords and concepts in evolutionary developmental biology.
Cambridge: Harvard University Press. ISBN 0-674-02240-8.
Evolution 46

External links
General information
• Evolution (http://www.bbc.co.uk/programmes/p00545gl) on In Our Time at the BBC. ( listen now (http://
www.bbc.co.uk/iplayer/console/p00545gl/In_Our_Time_Evolution))
• Everything you wanted to know about evolution by New Scientist (http://www.newscientist.com/topic/
evolution)
• Howstuffworks.com — How Evolution Works (http://science.howstuffworks.com/evolution/evolution.htm)
• National Academies Evolution Resources (http://nationalacademies.org/evolution/)
• Synthetic Theory Of Evolution: An Introduction to Modern Evolutionary Concepts and Theories (http://anthro.
palomar.edu/synthetic/)
• Understanding Evolution from University of California, Berkeley (http://evolution.berkeley.edu/)
• Evolution of Evolution - 150 Years of Darwin's "On the Origin of Species" (http://www.nsf.gov/news/
special_reports/darwin/textonly/index.jsp)
History of evolutionary thought
• The Complete Work of Charles Darwin Online (http://darwin-online.org.uk/)
• Understanding Evolution: History, Theory, Evidence, and Implications (http://www.rationalrevolution.net/
articles/understanding_evolution.htm)
On-line lectures
• What Genomes Can Tell Us About the Past (http://ascb.org/ibioseminars/brenner/brenner1.cfm) – lecture by
Sydney Brenner
• The Origin of Vertebrates (http://ascb.org/ibioseminars/kirschner/kirschner1.cfm) – lecture by Marc
Kirschner
• The Making of the Fittest (http://www.molbio.wisc.edu/carroll/Fittest.html) – lecture by Sean B. Carroll
Evolution as theory and fact 47

Evolution as theory and fact

The statement "evolution is both a theory and a fact" is often seen in biological literature.[1] [2] [3] [4] [5] [6] [7]
Evolution is a "theory" in the scientific sense of the term "theory"; it is an established scientific model that explains
observations and makes predictions through mechanisms such as natural selection.
When scientists say "evolution is a fact", they are using one of two meanings of the word "fact". One meaning is
empirical: evolution can be observed through changes in allele frequencies or traits of a population over successive
generations.
Another way "fact" is used is to refer to a certain kind of theory, one that has been so powerful and productive for
such a long time that it is universally accepted by scientists. When scientists say evolution is a fact in this sense, they
mean it is a fact that all living organisms have descended from a common ancestor (or ancestral gene pool) [8] even
though this cannot be directly observed. This implies more tangibly that it is a fact that humans share a common
ancestor with other primates.

Evolution, fact and theory

Evolution has been described as "fact and theory", "fact not theory", and "only a theory, not a fact". This illustrates a
confusion in terminology that hampers discussion.[9] [10] The meanings of the terms "evolution", "fact", and "theory"
are described below.

Evolution
Evolution is usually defined simply as changes in trait or gene frequency in a population of organisms from one
generation to the next. However, "evolution" is often used to include the following additional claims:
1. Differences in trait composition between isolated populations over many generations may result in the origin of
new species.
2. All living organisms alive today have descended from a common ancestor (or ancestral gene pool).
According to Douglas Futuyma:
Biological evolution may be slight or substantial; it embraces everything from slight changes in the proportion
of different alleles within a population (such as those determining blood types) to the successive alterations
that led from the earliest proto-organism to snails, bees, giraffes, and dandelions.[11]
The term "evolution", especially when referred to as a "theory", is also used more broadly to incorporate processes
such as natural selection and genetic drift.

Fact
Fact is often used by scientists to refer to experimental or empirical data or objective verifiable observations.[12] [13]
[14] [15]
"Fact" is also used in a wider sense to mean any theory for which there is overwhelming evidence.
A fact is a hypothesis that is so firmly supported by evidence that we assume it is true, and act as if it were
true. —Douglas Futyuma[16]
Evolution is a fact in the sense that it is overwhelmingly validated by the evidence. Frequently, evolution is said to
be a fact in the same way as the Earth revolving around the Sun is a fact.[16] [17] The following quotation from H. J.
Muller, "One Hundred Years Without Darwin Are Enough" explains the point.
There is no sharp line between speculation, hypothesis, theory, principle, and fact, but only a difference along
a sliding scale, in the degree of probability of the idea. When we say a thing is a fact, then, we only mean that
its probability is an extremely high one: so high that we are not bothered by doubt about it and are ready to
act accordingly. Now in this use of the term fact, the only proper one, evolution is a fact.[3]
Evolution as theory and fact 48

The National Academy of Science (U.S.) makes a similar point:

Scientists most often use the word "fact" to describe an observation. But scientists can also use fact to mean
something that has been tested or observed so many times that there is no longer a compelling reason to keep
testing or looking for examples. The occurrence of evolution in this sense is fact. Scientists no longer question
whether descent with modification occurred because the evidence is so strong.[18]
Philosophers of science argue that we do not know anything with absolute certainty: even direct observations may be
"theory laden" and depend on assumptions about our senses and the measuring instruments used. In this sense all
facts are provisional.[1] [19]

Theory
A scientific theory is a well-supported body of interconnected statements that explains observations and can be used
to make testable predictions. Scientific theories describe the coherent framework into which observable data fit. The
"theory of evolution" is the framework that best explains observed changes of species over time and best predicts the
new observations that continue to be made in evolutionary biology and related sciences.
The scientific definition of the word "theory" is different from the colloquial sense of the word. Colloquially,
"theory" can mean a conjecture, an opinion, or a speculation that does not have to be based on facts or make testable
predictions. In science, the meaning of theory is more rigorous: a theory must be based on observed facts and make
testable predictions. In science, a current theory is a theory that has no equally acceptable or more acceptable
alternative theory.

Evolution compared with gravity

The application of the terms "fact" and "theory" to evolution is similar to their use in describing gravity.[20]
The most obvious fact of gravity is that objects in our everyday experience tend to fall downwards when not
otherwise prevented from doing so. People throughout history have wondered what causes this effect. Many
explanations have been proposed over the centuries. Aristotle, Galileo, Newton, and Einstein have all developed
useful models of gravity, each of which constitutes a theory of gravity. (Newton, for example, realized that the fact
of gravity can be extended to the tendency of any two masses to attract one another.) The word "gravity", therefore,
can be used to refer to the observed facts (i.e., that masses attract one another) and the theory used to explain the
facts (the reason why masses attract one another). In this way, gravity is both a theory and a fact.
In the study of biological species, the facts include the existence of many different species in existence today, some
very similar to each other and some very dissimilar, the remains of extinct species in the fossil record, and so forth.
In species that rapidly reproduce, for example fruit flies, the process of change from generation to generation — that
is, evolutionary change — has been observed in the laboratory.[21] The observation of fruit fly populations changing
over time is also an example of a fact. So evolution is a fact just as the observations of gravity are a fact.
There have been many attempts to explain these biological observations over the years. Lamarckism,
transmutationism and orthogenesis were all non-Darwinian theories that attempted to explain the observations of
species and fossils, as well as other evidence. However, the modern theory of evolution is the explanation for all
relevant observations regarding the development of life, based on a model that explains all the available data and
observations (and provides testable predictions). Thus, evolution is not only a fact but also a theory, just as gravity is
both a fact and a theory.
Evolution as theory and fact 49

Evolution as theory and fact in the literature

The confusion over the word evolution and the distinction between "fact" and "theory" is largely due to authors using
evolution to refer to three related yet distinct ideas: first, the changes that occur within species over generations;
second, the mechanism thought to drive change; and third, the concept of common descent. However, among
biologists there is a consensus that evolution is a fact:
• American zoologist and paleontologist George Simpson stated that "Darwin... finally and definitely established
evolution as a fact."[22]
• H. J. Muller wrote, "If you like, then, I will grant you that in an absolute sense evolution is not a fact, or rather,
that it is no more a fact than that you are hearing or reading these words."[3]
• Kenneth R. Miller writes, "evolution is as much a fact as anything we know in science."[23]
• Ernst Mayr observed, "The basic theory of evolution has been confirmed so completely that most modern
biologists consider evolution simply a fact. How else except by the word evolution can we designate the sequence
of faunas and floras in precisely dated geological strata? And evolutionary change is also simply a fact owing to
the changes in the content of gene pools from generation to generation."[7]

Evolution as fact and theory

Commonly "fact" is used to refer to the observable changes in organisms' traits over generations while the word
"theory" is reserved for the mechanisms that cause these changes:
• Paleontologist Stephen Jay Gould writes, "Evolution is a theory. It is also a fact. And facts and theories are
different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are
structures of ideas that explain and interpret facts. Facts do not go away when scientists debate rival theories to
explain them. Einstein's theory of gravitation replaced Newton's, but apples did not suspend themselves in
mid-air, pending the outcome. And humans evolved from ape-like ancestors whether they did so by Darwin's
proposed mechanism or by some other yet to be discovered."[2]
• Similarly, biologist Richard Lenski says, "Scientific understanding requires both facts and theories that can
explain those facts in a coherent manner. Evolution, in this context, is both a fact and a theory. It is an
incontrovertible fact that organisms have changed, or evolved, during the history of life on Earth. And biologists
have identified and investigated mechanisms that can explain the major patterns of change."[6]
• Biologist T. Ryan Gregory says, "biologists rarely make reference to 'the theory of evolution,' referring instead
simply to 'evolution' (i.e., the fact of descent with modification) or 'evolutionary theory' (i.e., the increasingly
sophisticated body of explanations for the fact of evolution). That evolution is a theory in the proper scientific
sense means that there is both a fact of evolution to be explained and a well-supported mechanistic framework to
account for it."[20]

Evolution as fact not theory

Other commentators, focusing on the changes in species over generations and in some cases common ancestry have
stressed that evolution is a fact to emphasize the weight of supporting evidence while denying it is helpful to use the
term "theory":
• R. C. Lewontin wrote, "It is time for students of the evolutionary process, especially those who have been
misquoted and used by the creationists, to state clearly that evolution is a fact, not theory."[24]
• Douglas Futuyma writes in his Evolutionary Biology book, "The statement that organisms have descended with
modifications from common ancestors—the historical reality of evolution—is not a theory. It is a fact, as fully as
the fact of the earth's revolution about the sun."[11]
• Richard Dawkins says, "One thing all real scientists agree upon is the fact of evolution itself. It is a fact that we
are cousins of gorillas, kangaroos, starfish, and bacteria. Evolution is as much a fact as the heat of the sun. It is
not a theory, and for pity's sake, let's stop confusing the philosophically naive by calling it so. Evolution is a
Evolution as theory and fact 50

fact."[25]
• Neil Campbell wrote in his 1990 biology textbook, "Today, nearly all biologists acknowledge that evolution is a
fact. The term theory is no longer appropriate except when referring to the various models that attempt to explain
how life evolves... it is important to understand that the current questions about how life evolves in no way implies
any disagreement over the fact of evolution."[4]

Predictive power
A central tenet in science is that a scientific theory is supposed to have predictive power, and verification of
predictions are seen as an important and necessary support for the theory. The theory of evolution has provided such
predictions. Four examples are:
• Genetic information must be transmitted in a molecular way that will be almost exact but permit slight changes.
Since this prediction was made, biologists have discovered the existence of DNA, which has a mutation rate of
roughly 10−9 per nucleotide per cell division; this provides just such a mechanism.[26]
• Some DNA sequences are shared by very different organisms. It has been predicted by the theory of evolution
that the differences in such DNA sequences between two organisms should roughly resemble both the biological
difference between them according to their anatomy and the time that had passed since these two organisms have
separated in the course of evolution, as seen in fossil evidence. The rate of accumulating such changes should be
low for some sequences, namely those that code for critical RNA or proteins, and high for others that code for less
critical RNA or proteins; but for every specific sequence, the rate of change should be roughly constant over time.
These results have been experimentally confirmed. Two examples are DNA sequences coding for rRNA, which is
highly conserved, and DNA sequences coding for fibrinopeptides (amino acid chains that are discarded during the
formation of fibrin), which are highly non-conserved.[26]
• Prior to 2004, paleontologists had found fossils of amphibians with necks, ears, and four legs, in rock no older
than 365 million years old. In rocks more than 385 million years old they could only find fish, without these
amphibian characteristics. Evolutionary theory predicted that since amphibians evolved from fish, an intermediate
form should be found in rock dated between 365 and 385 million years ago. Such an intermediate form should
have many fish-like characteristics, conserved from 385 million years ago or more, but also have many amphibian
characteristics as well. In 2004, an expedition to islands in the Canadian arctic searching specifically for this
fossil form in rocks that were 375 million years old discovered fossils of Tiktaalik.[27]
• Evolutionary theory predicts that novel inventions can arise, while creationists predict that new "information"
cannot arise, and that the Second Law of Thermodynamics only allows for "information" to be lost.[28] In an
ongoing experiment, Richard Lenski observed that E. coli evolved the ability to metabolize citrate, which
constitutes a novel invention, and an increase in the information of the DNA of the E. coli.[29]

Related concepts and terminology

• Speculative or conjectural explanations are called hypotheses. Well-tested explanations are called theories.
• "Fact" does not mean "absolute certainty". In the words of Stephen J. Gould: In science, "fact" can only mean
"confirmed to such a degree that it would be perverse to withhold provisional assent."[2]
• "Proof" of a theory does not exist in natural sciences. Proof only exists in formal sciences, such as mathematics.
Experimental observation of the predictions made by a hypothesis or theory is called validation.
• A scientific law is a concept related to a scientific theory. Very well-established "theories" that rely on a simple
principle are often called scientific "laws". For example, it is common to encounter reference to "the law of
gravity", "the law of natural selection", or the "laws of evolution."
Evolution as theory and fact 51

See also
• Epistemology
• Evidence of common descent
• Evolution is just a theory, not a fact (in objections to evolution)
• Misconceptions about evolution (in List of misconceptions)
• Theory vs. Fact (in Creation-evolution controversy)

Notes
[1] Moran, Laurence (1993-01-22). "Evolution is a Fact and a Theory" (http:/ / www. talkorigins. org/ faqs/ evolution-fact. html). Talk.origins. .
Retrieved 2007-10-18.
[2] Gould, Stephen Jay (1981-05-01). "Evolution as Fact and Theory" (http:/ / www. stephenjaygould. org/ library/ gould_fact-and-theory. html).
Discover 2 (5): 34–37. . Reprinted in:
• Vetter, Herbert F. (ed.) (1982). Speak Out Against The New Right. Beacon Press. ISBN 0807004863.
• Gould, Stephen Jay (1994-04-01). Hen's Teeth and Horse's Toes. New York: Norton. ISBN 0393017168.
[3] Muller, H. J. (1959). "One hundred years without Darwin are enough" (http:/ / www. skepticfiles. org/ evolut/ 100pcnts. htm). School Science
and Mathematics 59: 304–305. doi:10.1111/j.1949-8594.1959.tb08235.x. . Reprinted in:
• Zetterberg, Peter (ed.) (1983-05-01). Evolution Versus Creationism: The Public Education Controversy. Phoenix AZ: ORYX Press.
ISBN 0897740610.
[4] Campbell, Neil A.; Reece, Jane B. (2002-02-05). Biology 6th ed.. Benjamin Cummings. p. 1175. ISBN 0805366245.
[5] Dobzhansky, Theodosius (1973-03-01). "Nothing in biology makes sense except in the light of evolution" (http:/ / people. delphiforums. com/
lordorman/ light. htm). American Biology Teacher 35. .

Reprinted in:
• Zetterberg, Peter (ed.) (1983-05-01). Evolution Versus Creationism: The Public Education Controversy. Phoenix AZ: ORYX Press.
ISBN 0897740610.
[6] Lenski, Richard E. (2000). "Evolution: Fact and Theory" (http:/ / www. actionbioscience. org/ evolution/ lenski. html). American Institute of
Biological Sciences. . Retrieved 2007-10-18.
[7] Mayr, Ernst (1988). Toward a New Philosophy of Biology: Observations of an Evolutionist. Cambridge: Harvard University Press.
ISBN 0-674-89666-1.
[8] Cavalier-Smith T (2006). "Cell evolution and Earth history: stasis and revolution" (http:/ / www. pubmedcentral. nih. gov/ articlerender.
fcgi?tool=pmcentrez& artid=1578732). Philos Trans R Soc Lond B Biol Sci 361 (1470): 969–1006. doi:10.1098/rstb.2006.1842.
PMID 16754610. PMC 1578732.
[9] Is "Evolution" a "Theory" or "Fact" or Is This Just a Trivial Game of Semantics? (http:/ / www. discovery. org/ a/ 6401) by Casey Luskin
[10] Committee for Skeptical Inquiry — Evolution & Creationism: Terminology in Conflict (http:/ / www. csicop. org/ specialarticles/ show/
evolution_amp_creationism_terminology_in_conflict/ ) by Richard Joltes
[11] Futuyma, Douglas J. (1997). , Evolutionary Biology, 3rd ed.. Sinauer Associates. p. 751. ISBN 0878931899.
[12] Wordnet entry for phrase "scientific fact" (http:/ / wordnet. princeton. edu/ perl/ webwn?s=scientific fact)
[13] United States National Park Service Glossary (http:/ / www2. nature. nps. gov/ views/ System/ Glossary. htm#F)
[14] Webster's New Millennium Dictionary of English, Preview Edition (v 0.9.6), Copyright © 2003–2006 Lexico Publishing Group, LLC (http:/
/ dictionary. reference. com/ search?q=scientific+ fact& r=66)
[15] Webster's Encyclopedic Unabridged Dictionary of the English Language (1996) gives a third meaning of the word "fact" as (3) A truth
known by actual experience or observation; something known to be true: 'Scientists gather facts about plant growth.'
[16] Hypotheses, Facts, and the Nature of Science, —Douglas Futyuma (http:/ / www. stephenjaygould. org/ library/ futuyma_theory. html)
[17] Guardian article by Richard Dawkins, Jerry Coyne (http:/ / www. guardian. co. uk/ science/ 2005/ sep/ 01/ schools. research)
[18] Science and Creationism: A View from the National Academy of Sciences, Second Edition (1999), National Academy of Sciences (NAS),
National Academy Press, Washington DC, 2006. (http:/ / books. nap. edu/ openbook. php?record_id=6024& page=28)
[19] Wilkins, JS (1997). "Evolution and Philosophy:Is Evolution Science, and What Does 'Science' Mean?" (http:/ / www. talkorigins. org/ faqs/
evolphil/ falsify. html). The TalkOrigins Archive (http:/ / www. talkorigins. org). . Retrieved 2009-08-17.
[20] Gregory, T. Ryan (2007). "Evolution as Fact, Theory, and Path". Evolution: Education and Outreach 1 (1): 46–52.
doi:10.1007/s12052-007-0001-z.
[21] Dobzhansky T, Pavlovsky O (1971). "Experimentally created incipient species of Drosophila". Nature 230 (5292): 289–92.
doi:10.1038/230289a0. PMID 5549403.
[22] Robinson, B.A. (2005-08-30). "Is the theory of evolution merely a "theory"?" (http:/ / www. religioustolerance. org/ ev_stat. htm). .
Retrieved 2007-10-18.
[23] "Miller, Kenneth S. (2007). Finding Darwin's God: A Scientist's Search for Common Ground Between God and Evolution (P.S.). New York,
N.Y: Harper Perennial. ISBN 0061233501.
Evolution as theory and fact 52

[24] Lewontin, R. C. (1981). "Evolution/Creation Debate: a time for truth". Bioscience 31: 559. Reprinted in:
• Zetterberg, Peter, ed. (1983-05-01). Evolution Versus Creationism: the public education controversy. Phoenix AZ: Oryx Press.
ISBN 0897740610.
[25] Natural History article : The Illusion of Design (http:/ / www. naturalhistorymag. com/ features/ 101500/ the-illusion-of-design) by Richard
Dawkins
[26] Bruce Alberts; Alexander Johnson; Julian Lewis; Martin Raff; Keith Roberts; Peter Walter (March, 2002). Molecular Biology of the Cell
(4th ed.). Routledge. ISBN 0-8153-3218-1.
[27] "Shubin, Neil. (2008). Your Inner Fish. Pantheon. ISBN 9780375424472.
[28] TalkOrigins.org (http:/ / www. talkorigins. org/ faqs/ thermo/ probability. html)
[29] NS:bacteria make major evolutionary shift in the lab (http:/ / www. newscientist. com/ channel/ life/
dn14094-bacteria-make-major-evolutionary-shift-in-the-lab. htm)

References
• J.P. Franck, et al., "Evolution of a satellite DNA family in tilapia." Annual Meeting Canadian Federation of
Biological Societies. Halifax, (1990).
• M. Losseau-Hoebeke, "The biology of four haplochromine species of Lake Kivu (Zaire) with evolutionary
implications." Thesis, Dept. Ichthyology, Rhodes University, Grahamstown, (1992).

External links
• Not Just a Theory (http://www.notjustatheory.com) Discredits the assertion that evolution is "just a theory",
with an explanation of the meaning of the word 'theory' in a scientific context.
• Talk Origins (http://www.talkorigins.org/indexcc/CB/CB910.html) Response to the claim that no examples
of speciation have been observed.
• Glenn Branch; Louise S. Mead (2008-06-06). "“Theory” in Theory and Practice" (http://www.springerlink.com/
content/fr258627q2x3t378/fulltext.pdf) (pdf). Evo Edu Outreach (2008) 1:287–289. Springer Science +
Business Media. Retrieved 2008-07-21.
Evolutionary history of life 53

Evolutionary history of life

The evolutionary history of life on Earth traces the processes by which living and fossil organisms evolved. It
stretches from the origin of life on Earth, thought to be over 3500 [1] million years ago, to the present day. The
similarities between all present day organisms indicate the presence of a common ancestor from which all known
species have diverged through the process of evolution.[2]
Microbial mats of coexisting bacteria and archaea were the dominant form of life in the early Archean and many of
the major steps in early evolution are thought to have taken place within them.[3] The evolution of oxygenic
photosynthesis, around 3500 [1] million years ago, eventually led to the oxygenation of the atmosphere, beginning
around 2400 [4] million years ago.[5] The earliest evidence of eukaryotes (complex cells with organelles), dates from
1850.0 [6] million years ago,[7] [8] and while they may have been present earlier, their diversification accelerated
when they started using oxygen in their metabolism. Later, around 1700 [9] million years ago, multicellular
organisms began to appear, with differentiated cells performing specialised functions.[10]
The earliest land plants date back to around 450.0 [11] million years ago,[12] though evidence suggests that algal scum
formed on the land as early as 1200 [13] million years ago. Land plants were so successful that they are thought to
have contributed to the late Devonian extinction event.[14] Invertebrate animals appear during the Vendian period,[15]
while vertebrates originated about 525 [16] million years ago during the Cambrian explosion.[17]
During the Permian period, synapsids, including the ancestors of mammals, dominated the land,[18] but the
Permian–Triassic extinction event 251.0 [19] million years ago came close to wiping out all complex life.[20] During
the recovery from this catastrophe, archosaurs became the most abundant land vertebrates, displacing therapsids in
the mid-Triassic.[21] One archosaur group, the dinosaurs, dominated the Jurassic and Cretaceous periods,[22] with the
ancestors of mammals surviving only as small insectivores.[23] After the Cretaceous–Tertiary extinction event 65 [24]
million years ago killed off the non-avian dinosaurs[25] mammals increased rapidly in size and diversity.[26] Such
mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to
diversify.[27]
Fossil evidence indicates that flowering plants appeared and rapidly diversified in the Early Cretaceous, between 130
[28]
million years ago and 90 [29] million years ago, probably helped by coevolution with pollinating insects.
Flowering plants and marine phytoplankton are still the dominant producers of organic matter. Social insects
appeared around the same time as flowering plants. Although they occupy only small parts of the insect "family
tree", they now form over half the total mass of insects. Humans evolved from a lineage of upright-walking apes
whose earliest fossils date from over 6 [30] million years ago. Although early members of this lineage had
chimp-sized brains, there are signs of a steady increase in brain size after about 3 [31] million years ago.

Earliest history of Earth

History of Earth and its life
Evolutionary history of life 54

Hadean
Archean
Protero
-zoic
Phanero
-zoic
Eo
Paleo
Meso
Neo
Paleo
Meso
Neo
Paleo
Meso
Ceno
Scale:
Millions of years
The oldest meteorite fragments found on Earth are about 4540 [32] million years old, this, coupled primarily with the
dating of ancient lead deposits, has put the estimated age of Earth at around that time.[33] About 40 million years
later a planetoid struck the Earth, throwing into orbit the material that formed the Moon.[34]
Evolutionary history of life 55

Until recently the oldest rocks found on Earth were about 3800 [35] million years old,[33] leading scientists to believe
for decades that Earth's surface had been molten until then. Accordingly, they named this part of Earth's history the
Hadean eon, whose name means "hellish".[36] However analysis of zircons formed 4400 to 4000 [37] million years
ago indicates that Earth's crust solidified about 100 million years after the planet's formation and that the planet
quickly acquired oceans and an atmosphere, which may have been capable of supporting life.[38]
Evidence from the Moon indicates that from 4000 to 3800 [39] million years ago it suffered a Late Heavy
Bombardment by debris that was left over from the formation of the Solar system, and the Earth should have
experienced an even heavier bombardment due to its stronger gravity.[36] [40] While there is no direct evidence of
conditions on Earth 4000 to 3800 [39] million years ago, there is no reason to think that the Earth was not also
affected by this late heavy bombardment.[41] This event may well have stripped away any previous atmosphere and
oceans; in this case gases and water from comet impacts may have contributed to their replacement, although
volcanic outgassing on Earth would have contributed at least half.[42]

Earliest evidence for life on Earth

The earliest identified organisms were minute and relatively featureless, their fossils look like small rods, which are
very difficult to tell apart from structures that arise through abiotic physical processes. The oldest undisputed
evidence of life on Earth, interpreted as fossilized bacteria, dates to 3000 [43] million years ago.[44] Other finds in
rocks dated to about 3500 [1] million years ago have been interpreted as bacteria,[45] with geochemical evidence also
seeming to show the presence of life 3800 [35] million years ago.[46] However these analyses were closely
scrutinized, and non-biological processes were found which could produce all of the "signatures of life" that had
been reported.[47] [48] While this does not prove that the structures found had a non-biological origin, they cannot be
taken as clear evidence for the presence of life. Currently, the oldest unchallenged evidence for life is geochemical
signatures from rocks deposited 3400 [49] million years ago,[44] [50] although these statements have not been
thoroughly examined by critics.

Origins of life on Earth

Biologists reason that all living
organisms on Earth must share a single
last universal ancestor, because it
would be virtually impossible that two
or more separate lineages could have
independently developed the many
complex biochemical mechanisms
common to all living organisms.[51] [52]
As previously mentioned the earliest
organisms for which fossil evidence is
available are bacteria, cells far too
complex to have arisen directly from
non-living materials.[53] The lack of
fossil or geochemical evidence for Evolutionary tree showing the divergence of modern species from their common ancestor
earlier organisms has left plenty of in the center.Ciccarelli, F.D., Doerks, T., von Mering, C., Creevey, C.J., et al (2006).
scope for hypotheses, which fall into "Toward automatic reconstruction of a highly resolved tree of life". Science 311 (5765):
1283–7. doi:10.1126/science.1123061. PMID 16513982.  The three domains are colored,
two main groups: 1) that life arose
with bacteria blue, archaea green, and eukaryotes red.
spontaneously on Earth or 2) that it

was "seeded" from elsewhere in the universe.

Evolutionary history of life 56

Life "seeded" from elsewhere

The idea that life on Earth was "seeded" from elsewhere in the universe dates back at least to the fifth century
BCE.[54] In the twentieth century it was proposed by the physical chemist Svante Arrhenius,[55] by the astronomers
Fred Hoyle and Chandra Wickramasinghe,[56] and by molecular biologist Francis Crick and chemist Leslie Orgel.[57]
There are three main versions of the "seeded from elsewhere" hypothesis: from elsewhere in our Solar system via
fragments knocked into space by a large meteor impact, in which case the only credible source is Mars;[58] by alien
visitors, possibly as a result of accidental contamination by micro-organisms that they brought with them;[57] and
from outside the Solar system but by natural means.[55] [58] Experiments suggest that some micro-organisms can
survive the shock of being catapulted into space and some can survive exposure to radiation for several days, but
there is no proof that they can survive in space for much longer periods.[58] Scientists are divided over the likelihood
of life arising independently on Mars,[59] or on other planets in our galaxy.[58]

Independent emergence on Earth

Life on earth is based on carbon and water. Carbon provides stable frameworks for complex chemicals and can be
easily extracted from the environment, especially from carbon dioxide. The only other element with similar chemical
properties, silicon, forms much less stable structures and, because most of its compounds are solids, would be more
difficult for organisms to extract. Water is an excellent solvent and has two other useful properties: the fact that ice
floats enables aquatic organisms to survive beneath it in winter; and its molecules have electrically negative and
positive ends, which enables it to form a wider range of compounds than other solvents can. Other good solvents,
such as ammonia, are liquid only at such low temperatures that chemical reactions may be too slow to sustain life,
and lack water's other advantages.[60] Organisms based on alternative biochemistry may however be possible on
other planets.[61]
Research on how life might have emerged unaided from non-living chemicals focuses on three possible starting
points: self-replication, an organism's ability to produce offspring that are very similar to itself; metabolism, its
ability to feed and repair itself; and external cell membranes, which allow food to enter and waste products to leave,
but exclude unwanted substances.[62] Research on abiogenesis still has a long way to go, since theoretical and
empirical approaches are only beginning to make contact with each other.[63] [64]

Replication first: RNA world

The replicator in virtually all known life is deoxyribonucleic acid. DNA's structure and replication systems are far more complex
[53]
than those of the original replicator.

Even the simplest members of the three modern domains of life use DNA to record their "recipes" and a complex
array of RNA and protein molecules to "read" these instructions and use them for growth, maintenance and
self-replication. This system is far too complex to have emerged directly from non-living materials.[53] The
discovery that some RNA molecules can catalyze both their own replication and the construction of proteins led to
the hypothesis of earlier life-forms based entirely on RNA.[65] These ribozymes could have formed an RNA world in
which there were individuals but no species, as mutations and horizontal gene transfers would have meant that the
offspring in each generation were quite likely to have different genomes from those that their parents started with.[66]
RNA would later have been replaced by DNA, which is more stable and therefore can build longer genomes,
expanding the range of capabilities a single organism can have.[66] [67] [68] Ribozymes remain as the main
components of ribosomes, modern cells' "protein factories".[69]
Although short self-replicating RNA molecules have been artificially produced in laboratories,[70] doubts have been
raised about where natural non-biological synthesis of RNA is possible.[71] The earliest "ribozymes" may have been
formed of simpler nucleic acids such as PNA, TNA or GNA, which would have been replaced later by RNA.[72] [73]
In 2003 it was proposed that porous metal sulfide precipitates would assist RNA synthesis at about 100 °C (212 °F)
and ocean-bottom pressures near hydrothermal vents. In this hypothesis lipid membranes would be the last major cell
Evolutionary history of life 57

components to appear and until then the proto-cells would be confined to the pores.[74]

Metabolism first: Iron-sulfur world

A series of experiments starting in 1997 showed that early stages in the formation of proteins from inorganic
materials including carbon monoxide and hydrogen sulfide could be achieved by using iron sulfide and nickel sulfide
as catalysts. Most of the steps required temperatures of about 100 °C (212 °F) and moderate pressures, although one
stage required 250 °C (482 °F) and a pressure equivalent to that found under 7 kilometres (4.3 mi) of rock. Hence it
was suggested that self-sustaining synthesis of proteins could have occurred near hydrothermal vents.[75]

Membranes first: Lipid world

= water-attracting heads of lipid molecules

= water-repellent tails
Cross-section through a liposome.

It has been suggested that double-walled "bubbles" of lipids like those that form the external membranes of cells may
have been an essential first step.[76] Experiments that simulated the conditions of the early Earth have reported the
formation of lipids, and these can spontaneously form liposomes, double-walled "bubbles", and then reproduce
themselves. Although they are not intrinsically information-carriers as nucleic acids are, they would be subject to
natural selection for longevity and reproduction. Nucleic acids such as RNA might then have formed more easily
within the liposomes than they would have outside.[77]

The clay theory

RNA is complex and there are doubts about whether it can be produced non-biologically in the wild.[71] Some clays,
notably montmorillonite, have properties that make them plausible accelerators for the emergence of an RNA world:
they grow by self-replication of their crystalline pattern; they are subject to an analog of natural selection, as the clay
"species" that grows fastest in a particular environment rapidly becomes dominant; and they can catalyze the
formation of RNA molecules.[78] Although this idea has not become the scientific consensus, it still has active
supporters.[79]
Research in 2003 reported that montmorillonite could also accelerate the conversion of fatty acids into "bubbles",
and that the "bubbles" could encapsulate RNA attached to the clay. These "bubbles" can then grow by absorbing
additional lipids and then divide. The formation of the earliest cells may have been aided by similar processes.[80]
A similar hypothesis presents self-replicating iron-rich clays as the progenitors of nucleotides, lipids and amino
acids.[81]
Evolutionary history of life 58

Environmental and evolutionary impact of microbial mats

Microbial mats are multi-layered, multi-species colonies of
bacteria and other organisms that are generally only a few
millimeters thick, but still contain a wide range of chemical
environments, each of which favors a different set of
micro-organisms.[82] To some extent each mat forms its own food
chain, as the by-products of each group of micro-organisms
generally serve as "food" for adjacent groups.[83]

Stromatolites are stubby pillars built as microbes in mats slowly

migrate upwards to avoid being smothered by sediment deposited
on them by water.[82] There has been vigorous debate about the Modern stromatolites in Shark Bay, Western Australia.
validity of alleged fossils from before 3000 [43] million years
ago,[84] with critics arguing that so-called stromatolites could have been formed by non-biological processes.[47] In
2006 another find of stromatolites was reported from the same part of Australia as previous ones, in rocks dated to
3500 [1] million years ago.[85]

In modern underwater mats the top layer often consists of photosynthesizing cyanobacteria which create an
oxygen-rich environment, while the bottom layer is oxygen-free and often dominated by hydrogen sulfide emitted by
the organisms living there.[83] It is estimated that the appearance of oxygenic photosynthesis by bacteria in mats
increased biological productivity by a factor of between 100 and 1,000. The reducing agent used by oxygenic
photosynthesis is water, which is much more plentiful than the geologically-produced reducing agents required by
the earlier non-oxygenic photosynthesis.[86] From this point onwards life itself produced significantly more of the
resources it needed than did geochemical processes.[87] Oxygen is toxic to organisms that are not adapted to it, but
greatly increases the metabolic efficiency of oxygen-adapted organisms.[88] [89] Oxygen became a significant
component of Earth's atmosphere about 2400 [4] million years ago.[90] Although eukaryotes may have been present
much earlier,[91] [92] the oxygenation of the atmosphere was a prerequisite for the evolution of the most complex
eukaryotic cells, from which all multicellular organisms are built.[93] The boundary between oxygen-rich and
oxygen-free layers in microbial mats would have moved upwards when photosynthesis shut down overnight, and
then downwards as it resumed on the next day. This would have created selection pressure for organisms in this
intermediate zone to acquire the ability to tolerate and then to use oxygen, possibly via endosymbiosis, where one
organism lives inside another and both of them benefit from their association.[3]
Cyanobacteria have the most complete biochemical "toolkits" of all the mat-forming organisms. Hence they are the
most self-sufficient of the mat organisms and were well-adapted to strike out on their own both as floating mats and
as the first of the phytoplankton, providing the basis of most marine food chains.[3]
Evolutionary history of life 59

Diversification of eukaryotes

Apusozoa

Archaeplastida (Land plants, green algae, red algae, and glaucophytes)

Bikonta Chromalveolata

Rhizaria

Excavata

Eukaryotes

Amoebozoa

Metazoa (Animals)
Unikonta
Opisthokonta Choanozoa

Eumycota (Fungi)

One possible family tree of eukaryotes[94] [95]

Eukaryotes may have been present long before the oxygenation of the atmosphere,[91] but most modern eukaryotes
require oxygen, which their mitochondria use to fuel the production of ATP, the internal energy supply of all known
cells.[93] In the 1970s it was proposed and, after much debate, widely accepted that eukaryotes emerged as a result of
a sequence of endosymbioses between "procaryotes". For example: a predatory micro-organism invaded a large
procaryote, probably an archaean, but the attack was neutralized, and the attacker took up residence and evolved into
the first of the mitochondria; one of these chimeras later tried to swallow a photosynthesizing cyanobacterium, but
the victim survived inside the attacker and the new combination became the ancestor of plants; and so on. After each
endosymbiosis began, the partners would have eliminated unproductive duplication of genetic functions by
re-arranging their genomes, a process which sometimes involved transfer of genes between them.[96] [97] [98] Another
hypothesis proposes that mitochondria were originally sulfur- or hydrogen-metabolising endosymbionts, and became
oxygen-consumers later.[99] On the other hand mitochondria might have been part of eukaryotes' original
equipment.[100]
There is a debate about when eukaryotes first appeared: the presence of steranes in Australian shales may indicate
that eukaryotes were present 2700 [101] million years ago;[92] however an analysis in 2008 concluded that these
chemicals infiltrated the rocks less than 2200 [102] million years ago and prove nothing about the origins of
eukaryotes.[103] Fossils of the alga Grypania have been reported in 1850.0 [6] million-year-old rocks (originally
dated to 2100 [104] million years ago but later revised[8] ), and indicates that eukaryotes with organelles had already
evolved.[105] A diverse collection of fossil algae were found in rocks dated between 1500 [106] million years ago and
1400 [107] million years ago.[108] The earliest known fossils of fungi date from 1430 [109] million years ago.[110]
Evolutionary history of life 60

Multicellular organisms and sexual reproduction

Multicellularity
The simplest definitions of "multicellular", for example "having
multiple cells", could include colonial cyanobacteria like Nostoc.
Even a professional biologist's definition such as "having the same
genome but different types of cell" would still include some
genera of the green alga Volvox, which have cells that specialize
in reproduction.[112] Multicellularity evolved independently in
organisms as diverse as sponges and other animals, fungi, plants, A slime mold solves a maze. The mold (yellow)
brown algae, cyanobacteria, slime moulds and myxobacteria.[8] explored and filled the maze (left). When the
[113] researchers placed sugar (red) at two separate points,
For the sake of brevity this article focuses on the organisms
the mold concentrated most of its mass there and left
that show the greatest specialization of cells and variety of cell
only the most efficient connection between the two
types, although this approach to the evolution of complexity could [111]
points (right).
be regarded as "rather anthropocentric".[114]

The initial advantages of multicellularity may have included: increased resistance to predators, many of which
attacked by engulfing; the ability to resist currents by attaching to a firm surface; the ability to reach upwards to
filter-feed or to obtain sunlight for photosynthesis;[115] the ability to create an internal environment that gives
protection against the external one;[114] and even the opportunity for a group of cells to behave "intelligently" by
sharing information.[111] These features would also have provided opportunities for other organisms to diversify, by
creating more varied environments than flat microbial mats could.[115]

Multicellularity with differentiated cells is beneficial to the organism as a whole but disadvantageous from the point
of view of individual cells, most of which lose the opportunity to reproduce themselves. In an asexual multicellular
organism, rogue cells which retain the ability to reproduce may take over and reduce the organism to a mass of
undifferentiated cells. Sexual reproduction eliminates such rogue cells from the next generation and therefore
appears to be a prerequisite for complex multicellularity.[115]
The available evidence indicates that eukaryotes evolved much earlier but remained inconspicuous until a rapid
diversification around 1000 [116] million years ago. The only respect in which eukaryotes clearly surpass bacteria and
archaea is their capacity for variety of forms, and sexual reproduction enabled eukaryotes to exploit that advantage
by producing organisms with multiple cells that differed in form and function.[115]

Evolution of sexual reproduction

The defining characteristic of sexual reproduction is recombination, in which each of the offspring receives 50% of
its genetic inheritance from each of the parents.[117] Bacteria also exchange DNA by bacterial conjugation, the
benefits of which include resistance to antibiotics and other toxins, and the ability to utilize new metabolites.[118]
However conjugation is not a means of reproduction, and is not limited to members of the same species – there are
cases where bacteria transfer DNA to plants and animals.[119]
The disadvantages of sexual reproduction are well-known: the genetic reshuffle of recombination may break up
favorable combinations of genes; and since males do not directly increase the number of offspring in the next
generation, an asexual population can out-breed and displace in as little as 50 generations a sexual population that is
equal in every other respect.[117] Nevertheless the great majority of animals, plants, fungi and protists reproduce
sexually. There is strong evidence that sexual reproduction arose early in the history of eukaryotes and that the genes
controlling it have changed very little since then.[120] How sexual reproduction evolved and survived is an unsolved
puzzle.[121]
Evolutionary history of life 61

The Red Queen Hypothesis suggests that sexual reproduction provides protection against parasites, because it is
easier for parasites to evolve means of overcoming the defenses of genetically identical clones than those of sexual
species that present moving targets, and there is some experimental evidence for this. However there is still doubt
about whether it would explain the survival of sexual species if multiple similar clone species were present, as one of
the clones may survive the attacks of parasites for long enough to out-breed the sexual species.[117]
The Mutation Deterministic Hypothesis assumes that each organism has more than one harmful mutation and the
combined effects of these mutations are more harmful than the sum of the harm done by each individual mutation. If
so, sexual recombination of genes will reduce the harm that bad mutations do to offspring and at the same time
eliminate some bad mutations from the gene pool by isolating them in individuals that perish quickly because they
have an above-average number of bad mutations. However the evidence suggests that the MDH's assumptions are
shaky, because many species have on average less than one harmful mutation per individual and no species that has
been investigated shows evidence of synergy between harmful mutations.[117]
The random nature of recombination causes the relative abundance of
alternative traits to vary from one generation to another. This genetic
drift is insufficient on its own to make sexual reproduction
advantageous, but a combination of genetic drift and natural selection
may be sufficient. When chance produces combinations of good traits,
natural selection gives a large advantage to lineages in which these
traits become genetically linked. On the other hand the benefits of good
traits are neutralized if they appear along with bad traits. Sexual
recombination gives good traits the opportunities to become linked
with other good traits, and mathematical models suggest this may be
more than enough to offset the disadvantages of sexual
Horodyskia apparently re-arranged itself into
reproduction.[121] Other combinations of hypotheses that are fewer but larger main masses as the sediment
inadequate on their own are also being examined.[117] grew deeper round its base.
[8]

The following hypotheses attempt to explain how and why sex

evolved:
• It may have enabled organisms to repair genetic damage.[122] The most primitive form of sex may have been one
organism repairing damaged DNA by replicating an undamaged strand from a similar organism.[123]
• Sexual reproduction may have originated from selfish parasitic genetic elements propagating themselves by
transfer to new hosts.[124]
• It may have evolved from cannibalism, where some of the victim's DNA was incorporated into the cannibal
organism.[123]
• Sexual reproduction may have evolved from ancient haloarchaea through a combination of jumping genes, and
swapping plasmids.[125]
• Or it may have evolved as a form of vaccination in which infected hosts exchanged weakened symbiotic copies of
parasitic DNA as protection against more virulent versions. The meiosis stage of sexual reproduction may then
have evolved as a way of removing the symbiotes.[126]
Bacteria also exchange DNA by bacterial conjugation, the benefits of which include resistance to antibiotics and
other toxins, and the ability to utilize new metabolites.[118] However conjugation is not a means of reproduction and
is not limited to members of the same species, and there are cases where bacteria transfer DNA to plants and
animals.[119] Nevertheless it may be an example of the "selfish genetic element" hypothesis, as it transfers DNA by
means of such a "selfish gene", the F-plasmid.[123]
Evolutionary history of life 62

Fossil evidence for multicellularity and sexual reproduction

[8] [127]
Horodyskia may have been an early metazoan, or a colonial foraminiferan

The Francevillian Group Fossil, dated to 2100 [104] million years ago, is the earliest known fossil organism that is
clearly multicellular.[] They may have had differentiated cells.[128] Another early multicellular fossil,
Qingshania,[129] dated to 1700 [9] million years ago, appears to consist of virtually identical cells. The red alga called
Bangiomorpha, dated at 1200 [13] million years ago, is the earliest known organism which certainly has
differentiated, specialized cells, and is also the oldest known sexually-reproducing organism.[115] The 1430 [109]
million-year-old fossils interpreted as fungi appear to have been multicellular with differentiated cells.[110] The
"string of beads" organism Horodyskia, found in rocks dated from 1500 [106] million years ago to 900.0 [130] million
years ago, may have been an early metazoan;[8] however it has also been interpreted as a colonial foraminiferan.[127]

Emergence of animals

Deuterostomes (chordates, hemichordates, echinoderms)

Ecdysozoa (arthropods, nematodes, tardigrades, etc.)

Bilaterians Protostomes
Lophotrochozoa (molluscs, annelids, brachiopods, etc.)

Acoelomorpha

Cnidaria (jellyfish, sea anemones, hydras)

Ctenophora (comb jellies)

Placozoa

Porifera (sponges): Calcarea

Porifera: Hexactinellida & Demospongiae

Choanoflagellata

Mesomycetozoea

A family tree of the animals.[131]

Animals are multicellular eukaryotes,[132] and are distinguished from plants, algae, and fungi by lacking cell
walls.[133] All animals are motile,[134] if only at certain life stages. All animals except sponges have bodies
differentiated into separate tissues, including muscles, which move parts of the animal by contracting, and nerve
tissue, which transmits and processes signals.[135]
The earliest widely-accepted animal fossils are rather modern-looking cnidarians (the group that includes jellyfish,
sea anemones and hydras), possibly from around 580 [136] million years ago, although fossils from the Doushantuo
Formation can only be dated approximately. Their presence implies that the cnidarian and bilaterian lineages had
already diverged.[137]
Evolutionary history of life 63

The Ediacara biota, which flourished for the last 40 million years before the start of the Cambrian,[138] were the first
animals more than a very few centimeters long. Many were flat and had a "quilted" appearance, and seemed so
strange that there was a proposal to classify them as a separate kingdom, Vendozoa.[139] Others, however, been
interpreted as early molluscs (Kimberella[140] [141] ), echinoderms (Arkarua[142] ), and arthropods (Spriggina,[143]
Parvancorina[144] ). There is still debate about the classification of these specimens, mainly because the diagnostic
features which allow taxonomists to classify more recent organisms, such as similarities to living organisms, are
generally absent in the Ediacarans. However there seems little doubt that Kimberella was at least a triploblastic
bilaterian animal, in other words significantly more complex than cnidarians.[145]
The small shelly fauna are a very mixed collection of fossils found between the Late Ediacaran and Mid Cambrian
periods. The earliest, Cloudina, shows signs of successful defense against predation and may indicate the start of an
evolutionary arms race. Some tiny Early Cambrian shells almost certainly belonged to molluscs, while the owners of
some "armor plates", Halkieria and Microdictyon, were eventually identified when more complete specimens were
found in Cambrian lagerstätten that preserved soft-bodied animals.[146]
In the 1970s there was already a debate about whether the emergence of the
modern phyla was "explosive" or gradual but hidden by the shortage of
Pre-Cambrian animal fossils.[146] A re-analysis of fossils from the Burgess
Shale lagerstätte increased interest in the issue when it revealed animals, such
as Opabinia, which did not fit into any known phylum. At the time these were
interpreted as evidence that the modern phyla had evolved very rapidly in the
"Cambrian explosion" and that the Burgess Shale's "weird wonders" showed
Opabinia made the largest single
that the Early Cambrian was a uniquely experimental period of animal
contribution to modern interest in the evolution.[148] Later discoveries of similar animals and the development of
[147]
Cambrian explosion. new theoretical approaches led to the conclusion that many of the "weird
wonders" were evolutionary "aunts" or "cousins" of modern groups[149] – for
example that Opabinia was a member of the lobopods, a group which includes the ancestors of the arthropods, and
that it may have been closely related to the modern tardigrades.[150] Nevertheless there is still much debate about
whether the Cambrian explosion was really explosive and, if so, how and why it happened and why it appears unique
in the history of animals.[151]

Most of the animals at the heart of the Cambrian explosion debate

are protostomes, one of the two main groups of complex animals.
One deuterostome group, the echinoderms, many of which have
hard calcite "shells", are fairly common from the Early Cambrian
small shelly fauna onwards.[146] Other deuterostome groups are
soft-bodied, and most of the significant Cambrian deuterostome Acanthodians were among the earliest vertebrates with
[152]
fossils come from the Chengjiang fauna, a lagerstätte in jaws

China.[153] The Chengjiang fossils Haikouichthys and

Myllokunmingia appear to be true vertebrates,[154] and Haikouichthys had distinct vertebrae, which may have been
slightly mineralized.[155] Vertebrates with jaws, such as the Acanthodians, first appeared in the Late Ordovician.[156]

Colonization of land
Adaptation to life on land is a major challenge: all land organisms need to avoid drying-out and all those above
microscopic size have to resist gravity; respiration and gas exchange systems have to change; reproductive systems
cannot depend on water to carry eggs and sperm towards each other.[157] [158] Although the earliest good evidence of
land plants and animals dates back to the Ordovician period (488 to 444 [159] million years ago), modern land
ecosystems only appeared in the late Devonian, about 385 to 359 [160] million years ago.[161]
Evolutionary history of life 64

Evolution of soil
Before the colonization of land, soil, a combination of mineral particles and decomposed organic matter, did not
exist. Land surfaces would have been either bare rock or unstable sand produced by weathering. Water and any
nutrients in it would have drained away very quickly.[161]
Films of cyanobacteria, which are not plants but use the same
photosynthesis mechanisms, have been found in modern deserts,
and only in areas that are unsuitable for vascular plants. This
suggests that microbial mats may have been the first organisms to
colonize dry land, possibly in the Precambrian. Mat-forming
cyanobacteria could have gradually evolved resistance to
desiccation as they spread from the seas to tidal zones and then to
land.[161] Lichens, which are symbiotic combinations of a fungus
(almost always an ascomycete) and one or more photosynthesizers Lichens growing on concrete
(green algae or cyanobacteria),[162] are also important colonizers
of lifeless environments,[161] and their ability to break down rocks contributes to soil formation in situations where
plants cannot survive.[162] The earliest known ascomycete fossils date from 423 to 419 [163] million years ago in the
Silurian.[161]

Soil formation would have been very slow until the appearance of burrowing animals, which mix the mineral and
organic components of soil and whose feces are a major source of the organic components.[161] Burrows have been
found in Ordovician sediments, and are attributed to annelids ("worms") or arthropods.[161] [164]

Plants and the Late Devonian wood crisis

In aquatic algae, almost all cells are capable of photosynthesies
and are nearly independent. Life on land required plants to become
internally more complex and specialized: photosynthesis was most
efficient at the top; roots were required in order to extract water
from the ground; the parts in between became supports and
transport systems for water and nutrients.[157] [165]

Spores of land plants, possibly rather like liverworts, have been

found in Mid Ordovician rocks dated to about 476 [166] million
years ago. In Mid Silurian rocks 430 [167] million years ago there
are fossils of actual plants including clubmosses such as
Baragwanathia; most were under 10 centimetres (3.9 in) high, and
some appear closely related to vascular plants, the group that
includes trees.[165] Reconstruction of Cooksonia, a vascular plant from the
Silurian.
By the Late Devonian 370 [168] million years ago, trees such as
Archaeopteris were so abundant that they changed river systems
from mostly braided to mostly meandering, because their roots bound the soil firmly.[169] In fact they caused a "Late
Devonian wood crisis",[170] because:
• They removed more carbon dioxide from the atmosphere, reducing the greenhouse effect and thus causing an ice
age in the Carboniferous period.[171] In later ecosystems the carbon
Evolutionary history of life 65

dioxide "locked up" in wood is returned to the atmosphere by

decomposition of dead wood. However the earliest fossil
evidence of fungi that can decompose wood also comes from
the Late Devonian.[172]
• The increasing depth of plants' roots led to more washing of
nutrients into rivers and seas by rain. This caused algal blooms
whose high consumption of oxygen caused anoxic events in
deeper waters, increasing the extinction rate among deep-water
animals.[171]
Fossilized trees from the Mid-Devonian Gilboa fossil
forest.
Land invertebrates
Animals had to change their feeding and excretory systems, and most land animals developed internal fertilization of
their eggs. The difference in refractive index between water and air required changes in their eyes. On the other hand
in some ways movement and breathing became easier, and the better transmission of high-frequency sounds in air
encouraged the development of hearing.[158]
Some trace fossils from the Cambrian-Ordovician boundary about 490.0 [173] million years ago are interpreted as the
tracks of large amphibious arthropods on coastal sand dunes, and may have been made by euthycarcinoids,[174]
which are thought to be evolutionary "aunts" of myriapods.[175] Other trace fossils from the Late Ordovician a little
over 445 [176] million years ago probably represent land invertebrates, and there is clear evidence of numerous
arthropods on coasts and alluvial plains shortly before the Silurian-Devonian boundary, about 415 [177] million years
ago, including signs that some arthropods ate plants.[178] Arthropods were well pre-adapted to colonise land, because
their existing jointed exoskeletons provided protection against desiccation, support against gravity and a means of
locomotion that was not dependent on water.[179]
The fossil record of other major invertebrate groups on land is poor: none at all for non-parasitic flatworms,
nematodes or nemerteans; some parasitic nematodes have been fossilized in amber; annelid worm fossils are known
from the Carboniferous, but they may still have been aquatic animals; the earliest fossils of gastropods on land date
from the Late Carboniferous, and this group may have had to wait until leaf litter became abundant enough to
provide the moist conditions they need.[158]
The earliest confirmed fossils of flying insects date from the Late Carboniferous, but it is thought that insects
developed the ability to fly in the Early Carboniferous or even Late Devonian. This gave them a wider range of
ecological niches for feeding and breeding, and a means of escape from predators and from unfavorable changes in
the environment.[180] About 99% of modern insect species fly or are descendants of flying species.[181]

Land vertebrates

Acanthostega changed views about the early evolution

[182]
of tetrapods
Evolutionary history of life 66

Osteolepiformes ("fish")

Panderichthyidae

Obruchevichthidae

Acanthostega

Ichthyostega

"Fish" Tulerpeton

Early amphibians

Anthracosauria

Amniotes

Family tree of tetrapods[183]

Tetrapods, vertebrates with four limbs, evolved from other rhipidistians over a relatively short timespan during the
Late Devonian, between 370 [168] million years ago and 360 [184] million years ago.[185] From the 1950s to the early
1980s it was thought that tetrapods evolved from fish that had already acquired the ability to crawl on land, possibly
in order to go from a pool that was drying out to one that was deeper. However in 1987 nearly-complete fossils of
Acanthostega from about 363 [186] million years ago showed that this Late Devonian transitional animal had legs and
both lungs and gills, but could never have survived on land: its limbs and its wrist and ankle joints were too weak to
bear its weight; its ribs were too short to prevent its lungs from being squeezed flat by its weight; its fish-like tail fin
would have been damaged by dragging on the ground. The current hypothesis is that Acanthostega, which was about
1 metre (3.3 ft) long, was a wholly aquatic predator that hunted in shallow water. Its skeleton differed from that of
most fish, in ways that enabled it to raise its head to breathe air while its body remained submerged, including: its
jaws show modifications that would have enabled it to gulp air; the bones at the back of its skull are locked together,
providing strong attachment points for muscles that raised its head; the head is not joined to the shoulder girdle and it
has a distinct neck.[182]
The Devonian proliferation of land plants may help to explain why air-breathing would have been an advantage:
leaves falling into streams and rivers would have encouraged the growth of aquatic vegetation; this would have
attracted grazing invertebrates and small fish that preyed on them; they would have been attractive prey but the
environment was unsuitable for the big marine predatory fish; air-breathing would have been necessary because
these waters would have been short of oxygen, since warm water holds less dissolved oxygen than cooler marine
water and since the decomposition of vegetation would have used some of the oxygen.[182]
Later discoveries revealed earlier transitional forms between Acanthostega and completely fish-like animals.[187]
Unfortunately there is then a gap of about 30 million years between the fossils of ancestral tetrapods and Mid
Carboniferous fossils of vertebrates that look well-adapted for life on land. Some of these look like early relatives of
modern amphibians, most of which need to keep their skins moist and to lay their eggs in water, while others are
Evolutionary history of life 67

accepted as early relatives of the amniotes, whose water-proof skins and eggs enable them to live and breed far from
water.[183]

Dinosaurs, birds and mammals

Early synapsids (extinct)

Extinct pelycosaurs

Extinct therapsids
Synapsids
Pelycosaurs
Therapsids Extinct mammaliformes
Mammaliformes
Mammals

[188]
Anapsids; whether turtles belong here is debated

Captorhinidae and Protorothyrididae

Araeoscelidia (extinct)

Squamata (lizards and snakes)

Amniotes

Extinct archosaurs

Crocodilians

Pterosaurs (extinct)

Sauropsids

Diapsids
Extinct
Archosaurs Theropods theropods

Birds
Dinosaurs

Sauropods
(extinct)

Ornithischians (extinct)
Evolutionary history of life 68

Possible family tree of dinosaurs, birds and mammals[189] [190]

Amniotes, whose eggs can survive in dry environments, probably evolved in the Late Carboniferous period, between
330 [191] million years ago and 314 [192] million years ago. The earliest fossils of the two surviving amniote groups,
synapsids and sauropsids, date from around 313 [193] million years ago.[189] [190] The synapsid pelycosaurs and their
descendants the therapsids are the most common land vertebrates in the best-known Permian fossil beds, between
229.0 [194] million years ago and 251.0 [19] million years ago. However at the time these were all in temperate zones
at middle latitudes, and there is evidence that hotter, drier environments nearer the Equator were dominated by
sauropsids and amphibians.[195]
The Permian-Triassic extinction wiped out almost all land vertebrates,[196] as well as the great majority of other
life.[197] During the slow recovery from this catastrophe, estimated to be 30M years,[198] a previously obscure
sauropsid group became the most abundant and diverse terrestrial vertebrates: a few fossils of archosauriformes
("shaped like archosaurs") have been found in Late Permian rocks,[199] but by the Mid Triassic archosaurs were the
dominant land vertebrates. Dinosaurs distinguished themselves from other archosaurs in the Late Triassic, and
became the dominant land vertebrates of the Jurassic and Cretaceous periods, between 199 [200] million years ago
and 65 [24] million years ago.[201]
During the Late Jurassic, birds evolved from small, predatory theropod dinosaurs.[202] The first birds inherited teeth
and long, bony tails from their dinosaur ancestors,[202] but some developed horny, toothless beaks by the very Late
Jurassic[203] and short pygostyle tails by the Early Cretaceous.[204]
While the archosaurs and dinosaurs were becoming more dominant in the Triassic, the mammaliform successors of
the therapsids could only survive as small, mainly nocturnal insectivores. This apparent set-back may actually have
promoted the evolution of mammals, for example nocturnal life may have accelerated the development of
endothermy ("warm-bloodedness") and hair or fur.[205] By 195 [206] million years ago in the Early Jurassic there
were animals that were very nearly mammals.[207] Unfortunately there is a gap in the fossil record throughout the
Mid Jurassic.[208] However fossil teeth discovered in Madagascar indicate that true mammals existed at least 167
[209]
million years ago.[210] After dominating land vertebrate niches for about 150 million years, the dinosaurs
perished 65 [24] million years ago in the Cretaceous–Tertiary extinction along with many other groups of
organisms.[211] Mammals throughout the time of the dinosaurs had been restricted to a narrow range of taxa, sizes
and shapes, but increased rapidly in size and diversity after the extinction,[212] [213] with bats taking to the air within
13 million years,[214] and cetaceans to the sea within 15 million years.[215]
Evolutionary history of life 69

Flowering plants

Angiosperms
(flowering plants)

Gnetales
(gymnosperm)

Welwitschia Cycads
(gymnosperm) (gymnosperm)
Gymnosperms Bennettitales
Ephedra
Gymnosperms
(gymnosperm)
Gingko

Bennettitales

Angiosperms Gnetales
(flowering plants) (gymnosperm)

Conifers
(gymnosperm)

One possible family tree of flowering

[216]
plants.

[217]
Another possible family tree.

The 250,000 to 400,000 species of flowering plants outnumber all other ground plants combined, and are the
dominant vegetation in most terrestrial ecosystems. There is fossil evidence that flowering plants diversified rapidly
in the Early Cretaceous, between 130 [28] million years ago and 90 [29] million years ago,[216] [217] and that their rise
was associated with that of pollinating insects.[217] Among modern flowering plants Magnolias are thought to be
close to the common ancestor of the group.[216] However paleontologists have not succeeded in identifying the
earliest stages in the evolution of flowering plants.[216] [217]

Social insects
The social insects are remarkable because the great majority of individuals in each colony are sterile. This appears
contrary to basic concepts of evolution such as natural selection and the selfish gene. In fact there are very few
eusocial insect species: only 15 out of approximately 2,600 living families of insects contain eusocial species, and it
seems that eusociality has evolved independently only 12 times among arthropods, although some eusocial lineages
have diversified into several families. Nevertheless social insects have been spectacularly successful; for example
although ants and termites account for only about 2% of known insect species, they form over 50% of the total mass
of insects. Their ability to control a territory appears to be the foundation of their success.[218]
Evolutionary history of life 70

The sacrifice of breeding opportunities by most individuals has

long been explained as a consequence of these species' unusual
haplodiploid method of sex determination, which has the
paradoxical consequence that two sterile worker daughters of the
same queen share more genes with each other than they would
with their offspring if they could breed.[219] However Wilson and
Hölldobler argue that this explanation is faulty: for example, it is
based on kin selection, but there is no evidence of nepotism in
colonies that have multiple queens. Instead, they write, eusociality
evolves only in species that are under strong pressure from
predators and competitors, but in environments where it is possible
to build "fortresses"; after colonies have established this security,
they gain other advantages though co-operative foraging. In
support of this explanation they cite the appearance of eusociality
in bathyergid mole rats,[218] which are not haplodiploid.[220]

The earliest fossils of insects have been found in Early Devonian

rocks from about 400 [221] million years ago, which preserve only
a few varieties of flightless insect. The Mazon Creek lagerstätten
These termite mounds have survived a bush fire.
from the Late Carboniferous, about 300 [222] million years ago,
include about 200 species, some gigantic by modern standards,
and indicate that insects had occupied their main modern ecological niches as herbivores, detritivores and
insectivores. Social termites and ants first appear in the Early Cretaceous, and advanced social bees have been found
in Late Cretaceous rocks but did not become abundant until the Mid Cenozoic.[223]

Humans
Modern humans evolved from a lineage of upright-walking apes that has been traced back over 6 [30] million years
ago to Sahelanthropus.[224] The first known stone tools were made about 2.5 [225] million years ago, apparently by
Australopithecus garhi, and were found near animal bones that bear scratches made by these tools.[226] The earliest
hominines had chimp-sized brains, but there has been a fourfold increase in the last 3 million years; a statistical
analysis suggests that hominine brain sizes depend almost completely on the date of the fossils, while the species to
which they are assigned has only slight influence.[227] There is a long-running debate about whether modern humans
evolved all over the world simultaneously from existing advanced hominines or are descendants of a single small
population in Africa, which then migrated all over the world less than 200,000 years ago and replaced previous
hominine species.[228] There is also debate about whether anatomically-modern humans had an intellectual, cultural
and technological "Great Leap Forward" under 100,000 years ago and, if so, whether this was due to neurological
changes that are not visible in fossils.[229]
Evolutionary history of life 71

Mass extinctions

K–T
Tr–J
P–Tr
Late D
O–S
Millions of years ago
Apparent extinction intensity, i.e. the fraction of genera going extinct at any given time, as reconstructed from the fossil record.
(Graph not meant to include recent epoch of Holocene extinction event)

Life on earth has suffered occasional mass extinctions at least since 542 [230] million years ago. Although they are
disasters at the time, mass extinctions have sometimes accelerated the evolution of life on earth. When dominance of
particular ecological niches passes from one group of organisms to another, it is rarely because the new dominant
group is "superior" to the old and usually because an extinction event eliminates the old dominant group and makes
way for the new one.[231] [232]
The fossil record appears to show that the gaps between mass extinctions are becoming longer and the average and
background rates of extinction are decreasing. Both of these phenomena could be explained in one or more
ways:[233]
• The oceans may have become more hospitable to life over the last 500 million years and less vulnerable to mass
extinctions: dissolved oxygen became more widespread and penetrated to greater depths; the development of life
on land reduced the run-off of nutrients and hence the risk of eutrophication and anoxic events; and marine
ecosystems became more diversified so that food chains were less likely to be disrupted.[234] [235]
• Reasonably complete fossils are very rare, most extinct organisms are represented only by partial fossils, and
complete fossils are rarest in the oldest rocks. So paleontologists have mistakenly assigned parts of the same
organism to different genera which were often defined solely to accommodate these finds – the story of
Anomalocaris is an example of this. The risk of this mistake is higher for older fossils because these are often
unlike parts of any living organism. Many of the "superfluous" genera are represented by fragments which are not
found again and the "superfluous" genera appear to become extinct very quickly.[233]
Evolutionary history of life 72

All genera
"Well-defined" genera
Trend line
"Big Five" mass extinctions
Other mass extinctions
Million years ago
Thousands of genera
Phanerozoic biodiversity as shown by the fossil record

Biodiversity in the fossil record, which is

"the number of distinct genera alive at any given time; that is, those whose first occurrence predates and
whose last occurrence postdates that time"[236]
shows a different trend: a fairly swift rise from 542 to 400 [237] million years ago; a slight decline from 400 to 200
[238]
million years ago, in which the devastating Permian–Triassic extinction event is an important factor; and a swift
rise from 200 [239] million years ago to the present.[236]

The present
Oxygenic photosynthesis accounts for virtually all of the production of organic matter from non-organic ingredients.
Production is split about evenly between land and marine plants, and phytoplankton are the dominant marine
producers.[240]
The processes that drive evolution are still operating. Well-known examples include the changes in coloration of the
peppered moth over the last 200 years and the more recent appearance of pathogens that are resistant to
antibiotics.[241] [242] There is even evidence that humans are still evolving, and possibly at an accelerating rate over
the last 40,000 years.[243]
Evolutionary history of life 73

See also
• Evolution
• Evolutionary history of plants
• Timeline of evolution
• History of evolutionary thought

Footnotes
[1] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=3500
[2] Futuyma, Douglas J. (2005). Evolution. Sunderland, Massachusetts: Sinuer Associates, Inc. ISBN 0-87893-187-2.
[3] Nisbet, E.G., and Fowler, C.M.R. (December 7, 1999). "Archaean metabolic evolution of microbial mats" (http:/ / www. pubmedcentral. nih.
gov/ articlerender. fcgi?tool=pmcentrez& artid=1690475). Proceedings of the Royal Society: Biology 266 (1436): 2375.
doi:10.1098/rspb.1999.0934. PMC 1690475. - abstract with link to free full content (PDF)
[4] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=2400
[5] Anbar, A.; Duan, Y.; Lyons, T.; Arnold, G.; Kendall, B.; Creaser, R.; Kaufman, A.; Gordon, G. et al. (2007). "A whiff of oxygen before the
great oxidation event?". Science (New York, N.Y.) 317 (5846): 1903–1906. doi:10.1126/science.1140325. PMID 17901330.
[6] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=1850
[7] Knoll, Andrew H.; Javaux, E.J, Hewitt, D. and Cohen, P. (2006). "Eukaryotic organisms in Proterozoic oceans" (http:/ / www.
pubmedcentral. nih. gov/ articlerender. fcgi?tool=pmcentrez& artid=1578724). Philosophical Transactions of the Royal Society of London,
Part B 361 (1470): 1023–38. doi:10.1098/rstb.2006.1843. PMID 16754612. PMC 1578724.
[8] Fedonkin, M. A. (March 2003). "The origin of the Metazoa in the light of the Proterozoic fossil record" (http:/ / www. vend. paleo. ru/ pub/
Fedonkin_2003. pdf) (PDF). Paleontological Research 7 (1): 9–41. doi:10.2517/prpsj.7.9. . Retrieved 2008-09-02.
[9] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=1700
[10] Bonner, J.T. (1998) The origins of multicellularity. Integr. Biol. 1, 27–36
[11] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=450
[12] "The oldest fossils reveal evolution of non-vascular plants by the middle to late Ordovician Period (~450-440 m.y.a.) on the basis of fossil
spores" Transition of plants to land (http:/ / www. clas. ufl. edu/ users/ pciesiel/ gly3150/ plant. html)
[13] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=1200
[14] Algeo, T.J.; Scheckler, S. E. (1998). "Terrestrial-marine teleconnections in the Devonian: links between the evolution of land plants,
weathering processes, and marine anoxic events". Philosophical Transactions of the Royal Society B: Biological Sciences 353 (1365):
113–130. doi:10.1098/rstb.1998.0195.
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References

Further reading
• Cowen, R. (2004). History of Life (4th ed.). Blackwell Publishing Limited. ISBN 978-1405117562.
• The Ancestor's Tale, A Pilgrimage to the Dawn of Life. Boston: Houghton Mifflin Company. 2004.
ISBN 0-618-00583-8.
• Richard Dawkins. (1990). The Selfish Gene. Oxford University Press. ISBN 0192860925.
• Smith, John Maynard; Eörs Szathmáry (1997). The Major Transitions in Evolution. Oxfordshire: Oxford
University Press. ISBN 0-198-50294-X.

External links
General information
• General information on evolution- Fossil Museum nav. (http://www.fossilmuseum.net/Evolution.htm)
• Understanding Evolution from University of California, Berkeley (http://evolution.berkeley.edu/)
• National Academies Evolution Resources (http://nationalacademies.org/evolution/)
• Evolution poster- PDF format "tree of life" (http://tellapallet.com/tree_of_life.htm)
• Everything you wanted to know about evolution by New Scientist (http://www.newscientist.com/channel/life/
evolution)
• Howstuffworks.com — How Evolution Works (http://science.howstuffworks.com/evolution.htm/printable)
• Synthetic Theory Of Evolution: An Introduction to Modern Evolutionary Concepts and Theories (http://anthro.
palomar.edu/synthetic/)
History of evolutionary thought
• The Complete Work of Charles Darwin Online (http://darwin-online.org.uk)
• Understanding Evolution: History, Theory, Evidence, and Implications (http://www.rationalrevolution.net/
articles/understanding_evolution.htm)
Timeline of evolution 83

Timeline of evolution
This timeline of the evolution of life outlines the major events in the development of life on the planet Earth (See
Organism). For a thorough explanatory context, see the history of Earth, and geologic time scale. The dates given in
this article are estimates based on scientific evidence.
In biology, evolution is the process by which populations of organisms acquire and pass on novel traits from
generation to generation. Its occurrence over large stretches of time explains the origin of new species and ultimately
the vast diversity of the biological world. Contemporary species are related to each other through common descent,
products of evolution and speciation over billions of years.

Basic timeline
The basic timeline is a 4.5 billion year old Earth, with (very approximate) dates:
• 3.8 billion years of simple cells (prokaryotes),
• 3 billion years of photosynthesis,
• 2 billion years of complex cells (eukaryotes),
• 1 billion years of multicellular life,
• 600 million years of simple animals,
• 570 million years of arthropods (ancestors of insects, arachnids and crustaceans),
• 550 million years of complex animals,
• 500 million years of fish and proto-amphibians,
• 475 million years of land plants,
• 400 million years of insects and seeds,
• 360 million years of amphibians,
• 300 million years of reptiles,
• 200 million years of mammals,
• 150 million years of birds,
• 130 million years of flowers,
• 65 million years since the non-avian dinosaurs died out,
• 2.5 million years since the appearance of the genus Homo,
• 200,000 years since humans started looking like they do today,
• 25,000 years since Neanderthals died out.

Detailed timeline
Ma, ("megaannum") means "million years ago". ka means "thousand years ago" and ya means "years ago"

Hadean Eon
3800 Ma and earlier.
Timeline of evolution 84

Date Event

4600 Ma The planet Earth forms from the accretion disc revolving around the young Sun.

4500 Ma According to one plausible theory, the planet Earth and the planet Theia collide, sending a very large number of moonlets into
[1]
orbit around the young Earth. These moonlets eventually coalesce to form the Moon. The gravitational pull of the new Moon
[2]
stabilises the Earth's fluctuating axis of rotation and sets up the conditions in which life formed.

4100 Ma The surface of the Earth cools enough for the crust to solidify. The atmosphere and the oceans form.[3] PAH infall,[4] and iron

sulfide synthesis along deep ocean platelet boundaries, may have led to the RNA world of competing organic compounds.

Between 4500 The earliest life appears, possibly derived from self-reproducing RNA molecules.[5] [6] The replication of these organisms
and 3500 Ma requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition, with

natural selection favouring those molecules which are more efficient at replication. DNA molecules then take over as the main
replicators and these archaic genomes soon develop inside enclosing membranes which provide a stable physical and chemical
[7] [8] [9]
environment conducive to their replication: proto-cells.

3900 Ma Late Heavy Bombardment: peak rate of impact events upon the inner planets by meteors. This constant disturbance may have

obliterated any life that had evolved to that point, or possibly not, as some early microbes could have survived in hydrothermal
[10] [11]
vents below the Earth's surface; or life might have been transported to Earth by a meteor.

Somewhere Cells resembling prokaryotes appear.[12] These first organisms are chemoautotrophs: they use carbon dioxide as a carbon source
between 3900 - and oxidize inorganic materials to extract energy. Later, prokaryotes evolve glycolysis, a set of chemical reactions that free the
2500 Ma energy of organic molecules such as glucose and store it in the chemical bonds of ATP. Glycolysis (and ATP) continue to be
[13] [14]
used in almost all organisms, unchanged, to this day.

Archean Eon
3800 Ma – 2500 Ma

Date Event

3500 Lifetime of the last universal ancestor;[15] [16] the split between bacteria and archaea occurs.[17]
Ma [18]
Bacteria develop primitive forms of photosynthesis which at first do not produce oxygen. These organisms generate ATP by exploiting
a proton gradient, a mechanism still used in virtually all organisms.

3000 Photosynthesizing cyanobacteria evolve; they use water as a reducing agent, thereby producing oxygen as waste product.[19] More recent
Ma research, however, suggests a later time of 2700 Ma. The oxygen initially oxidizes dissolved iron in the oceans, creating iron ore. The

oxygen concentration in the atmosphere subsequently rises, acting as a poison for many bacteria. The moon is still very close to the earth
and causes tides 1000 feet (305 m) high. The earth is continually wracked by hurricane force winds. These extreme mixing influences are
thought to stimulate evolutionary processes. (See Oxygen catastrophe)

2700 Timeframe of cyanobacteria evolution suggested by more recent research.

Ma

Proterozoic Eon
2500 Ma – 542 Ma
Timeline of evolution 85

Date Event

By 1850 Eukaryotic cells appear.[20] [21] Eukaryotes contain membrane-bound organelles with diverse functions, probably derived from
Ma prokaryotes engulfing each other via phagocytosis. (See Endosymbiosis)

By 1200 Sexual reproduction first appears, increasing the rate of evolution.[22]

Ma

1200 Ma Simple multicellular organisms evolve, mostly consisting of cell colonies of limited complexity.

850–630 A global glaciation may have occurred.[23] [24] Opinion is divided on whether it increased or decreased biodiversity or the rate of
Ma evolution.[25] [26] [27]

580–542 The Ediacaran biota represent the first large, complex multicellular organisms - although their affinities remain a subject of debate.[28]
Ma

580–500 Most modern phyla of animals begin to appear in the fossil record during the Cambrian explosion.[29] [30]
Ma

580–540 The accumulation of atmospheric oxygen allows the formation of an ozone layer.[31] This blocks ultraviolet radiation, permitting the
Ma colonisation of the land.[31]

560 Ma Earliest fungi

Phanerozoic Eon
542 Ma – present
The Phanerozoic Eon, literally the "period of well-displayed life", marks the appearance in the fossil record of
abundant, shell-forming and/or trace-making organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and
Cenozoic, which are divided by major mass extinctions.

Paleozoic Era
542 Ma – 251.0 Ma

Date Event

535 Major diversification of living things in the oceans: chordates, arthropods (e.g. trilobites, crustaceans), echinoderms, mollusks,
Ma brachiopods, foraminifers and radiolarians, etc.

530 The first known footprints on land date to 530 Ma, indicating that early animal explorations may have predated the development of
Ma terrestrial plants.[32]

525 Earliest graptolites.

Ma

510 First cephalopods (Nautiloids) and chitons.

Ma

505 Fossilization of the Burgess Shale.

Ma

485 First vertebrates with true bones (jawless fishes).

Ma

450 Land arthropod burrows (millipedes) appear, along with the first complete conodonts and echinoids.
Ma

440 First agnathan fishes: Heterostraci, Galeaspida, and Pituriaspida.

Ma

434 The first primitive plants move onto land,[33] having evolved from green algae living along the edges of lakes.[34] They are accompanied
Ma by fungi, which may have aided the colonisation of land through symbiosis.
Timeline of evolution 86

420 Earliest ray-finned fishes, trigonotarbid arachnids, and land scorpions.

Ma

410 First signs of teeth in fish. Earliest nautiid nautiloids, lycophytes, and trimerophytes.
Ma

395 First lichens, stoneworts. Earliest harvestman, mites, hexapods (springtails), and ammonoids.
Ma

363 By the start of the Carboniferous Period, the Earth begins to be recognisable. Insects roamed the land and would soon take to the skies;
Ma sharks swam the oceans as top predators,[35] and vegetation covered the land, with seed-bearing plants and forests soon to flourish.

Four-limbed tetrapods gradually gain adaptations which will help them occupy a terrestrial life-habit.

360 First crabs and ferns. Land flora dominated by seed ferns.
Ma

350 First large sharks, ratfishes, and hagfish.

Ma

340 Diversification of amphibians.

Ma

330 First amniote vertebrates (Paleothyris).

Ma

305 Earliest diapsid reptiles (e.g. Petrolacosaurus).

Ma

280 Earliest beetles, seed plants and conifers diversify while lepidodendrids and sphenopsids decrease. Terrestrial temnospondyl amphibians
Ma and pelycosaurs (e.g. Dimetrodon) diversify in species.

251.4 The Permian-Triassic extinction event eliminates over 90-95% of marine species. Terrestrial organisms were not as seriously affected as
Ma the marine biota. This "clearing of the slate" may have led to an ensuing diversification, but life on land took 30M years to completely
[36]
recover.

Mesozoic Era

Date Event

From The Mesozoic Marine Revolution begins: increasingly well-adapted and diverse predators pressurise sessile marine groups; the "balance
251.4 of power" in the oceans shifts dramatically as some groups of prey adapt more rapidly and effectively than others.
Ma

245 Ma Earliest ichthyosaurs.

240 Ma Increase in diversity of gomphodont cynodonts and rhynchosaurs.

225 Ma Earliest dinosaurs (prosauropods), first cardiid bivalves, diversity in cycads, bennettitaleans, and conifers. First teleost fishes.

215 Ma First mammals (e.g. Eozostrodon), minor vertebrate extinctions occur

Timeline of evolution 87

220 Ma

Eoraptor, among the earliest dinosaurs, appeared in the

fossil record 230 million years ago.

Gymnosperm forests dominate the land; herbivores grow to huge sizes in order to accommodate the large guts necessary to digest the
nutrient-poor plants., first flies and turtles (Odontochelys). First Coelophysoid dinosaurs

200 Ma The first accepted evidence for viruses (at least, the group Geminiviridae) exists.[37] Viruses are still poorly understood and may have

arisen before "life" itself, or may be a more recent phenomenon. Major extinctions in terrestrial vertebrates and large amphibians. Earliest
examples of Ankylosaurian dinosaurs

195 Ma First pterosaurs with specialized feeding (Dorygnathus). First sauropod dinosaurs. Diversification in small, ornithischian dinosaurs:
heterodontosaurids, fabrosaurids, and scelidosaurids.

190 Ma Pliosaurs appear in the fossil record. First lepidopteran insects (Archaeolepis), hermit crabs, modern starfish, irregular echinoids, corbulid
bivalves, and tubulipore bryozoans. Extensive development of sponge reefs.

176 Ma First members of the Stegosauria group of dinosaurs

170 Ma Earliest salamanders, newts, cryptoclidid & elasmosaurid plesiosaurs, and cladotherian mammals. Cynodonts become extinct while
sauropod dinosaurs diversify.

165 Ma First rays and glycymeridid bivalves.

161 Ma Ceratopsian dinosaurs appear in the fossil record (Yinlong)

155 Ma First blood-sucking insects (ceratopogonids), rudist bivalves, and cheilosome bryozoans. Archaeopteryx, a possible ancestor to the birds,
appears in the fossil record, along with triconodontid and symmetrodont mammals. Diversity in stegosaurian and theropod dinosaurs.

130 Ma The rise of the Angiosperms: These flowering plants boast structures that attract insects and other animals to spread pollen. This
innovation causes a major burst of animal evolution through co-evolution. First freshwater pelomedusid turtles.

115 Ma First monotreme mammals.

110 Ma First hesperornithes, toothed diving birds. Earliest limopsid, verticordiid, and thyasirid bivalves.

106 Ma Spinosaurus, the largest theropod dinosaur, appears in the fossil record.

100 Ma Earliest bees.

90 Ma Extinction of ichthyosaurs. Earliest snakes and nuculanid bivalves. Large diversification in angiosperms: magnoliids, rosids,
hamamelidids, monocots, and ginger. Earliest examples of ticks.

80 Ma First ants and termites.

70 Ma Multituberculate mammals increase in diversity. First yoldiid bivalves.

68 Ma Tyrannosaurus, the largest terrestrial predator of North America appears in the fossil record. First species of Triceratops.
Timeline of evolution 88

Cenozoic Era
65.5 Ma – present

Date Event

65.5 The Cretaceous–Tertiary extinction event eradicates about half of all animal species, including mosasaurs, pterosaurs, plesiosaurs,
Ma ammonites, belemnites, rudist and inoceramid bivalves, most planktic foraminifers, and all of the dinosaurs excluding their descendants
[38]
the birds

From Rapid dominance of conifers and ginkgos in high latitudes, along with mammals becoming the dominant species. First psammobiid
65 Ma bivalves. Rapid diversification in ants.

63 Ma Evolution of the creodonts, an important group of carnivorous mammals.

60 Ma Diversification of large, flightless birds. Earliest true primates, along with the first semelid bivalves, edentates, carnivorous and
lipotyphlan mammals, and owls. The ancestors of the carnivorous mammals (miacids) were alive.

56 Ma Gastornis, a large, flightless bird appears in the fossil record, becoming an apex predator at the time.

55 Ma Modern bird groups diversify (first song birds, parrots, loons, swifts, woodpeckers), first whale (Himalayacetus), earliest rodents,
lagomorphs, armadillos, appearance of sirenians, proboscideans, perissodactyl and artiodactyl mammals in the fossil record. Angiosperms
diversify. The ancestor (according to theory) of the species in Carcharodon, the early mako shark Isurus hastalis, is alive.

52 Ma First bats appear (Onychonycteris).

50 Ma Peak diversity of dinoflagellates and nanofossils, increase in diversity of anomalodesmatan and heteroconch bivalves, brontotheres, tapirs,
rhinoceroses, and camels appear in the fossil record, diversification of primates.

40 Ma Modern type butterflies and moths appear. Extinction of Gastornis. Basilosaurus, one of the first of the giant whales, appeared in the fossil
record.

37 Ma First Nimravid carnivores ("False Saber-toothed Cats") - these species are unrelated to modern-type felines

35 Ma Grasses evolve from among the angiosperms; grasslands begin to expand. Slight increase in diversity of cold-tolerant ostracods and
foraminifers, along with major extinctions of gastropods, reptiles, and amphibians. Many modern mammal groups begin to appear: first
glyptodonts, ground sloths, dogs, peccaries, and the first eagles and hawks. Diversity in toothed and baleen whales.

33 Ma Evolution of the thylacinid marsupials (Badjcinus).

30 Ma First balanids and eucalypts, extinction of embrithopod and brontothere mammals, earliest pigs and cats.

28 Ma Paraceratherium appears in the fossil record, the largest terrestrial mammal that ever lived.

25 Ma First deer.

20 Ma First giraffes and giant anteaters, increase in bird diversity.

15 Ma Mammut appears in the fossil record, first bovids and kangaroos, diversity in Australian megafauna.

10 Ma Grasslands and savannas are established, diversity in insects, especially ants and termites, horses increase in body size and develop
high-crowned teeth, major diversification in grassland mammals and snakes.

6.5 Ma First hominin (Sahelanthropus).

6 Ma Australopithecines diversify (Orrorin, Ardipithecus)

5 Ma First tree sloths and hippopotami, diversification of grazing herbivores, large carnivorous mammals, burrowing rodents, kangaroos, birds,
and small carnivores, vultures increase in size, decrease in the number of perissodactyl mammals. Extinction of Nimravid carnivores

4.8 Ma Mammoths appear in the fossil record.

4 Ma Evolution of Australopithecus, Stupendemys appears in the fossil record as the largest freshwater turtle.

3 Ma The Great American Interchange, where various land and freshwater faunas migrated between North and South America. Armadillos,
opossums, hummingbirds, and vampire bats traveled to North America while horses, tapirs, saber-toothed cats, and deer entered South
America. The first short-faced bears (Arctodus) appear.

2.7 Ma Evolution of Paranthropus

2.5 Ma The earliest species of Smilodon evolve

Timeline of evolution 89

2 Ma First members of the genus Homo appear in the fossil record. Diversification of conifers in high latitudes. The eventual ancestor of cattle,
Bos primigenius evolves in India

1.7 Ma Extinction of australopithecines.

1.2 Ma Evolution of Homo antecessor. The last members of Paranthropus die out.

600 ka Evolution of Homo heidelbergensis

350 ka Evolution of Neanderthals

300 ka Gigantopithecus, a giant relative of the orangutan dies out from Asia

200 ka Anatomically modern humans appear in Africa.[39] [40] [41] Around 50,000 years before present they start colonising the other

continents, replacing the Neanderthals in Europe and other hominins in Asia.

40 ka The last of the giant monitor lizards (Megalania) die out

30 ka Extinction of Neanderthals

15 ka The last Woolly rhinoceros (Coelodonta) are believed to have gone extinct

11 ka The giant short-faced bears (Arctodus) vanish from North America, with the last Giant Ground Sloths dying out. All Equidae become
extinct in North America

10 ka The Holocene Epoch starts 10,000[42] years ago after the Late Glacial Maximum. The last mainland species of Woolly mammoth

(Mammuthus primigenius) die out, as does the last Smilodon species

6 ka Small populations of American Mastodon die off in places like Utah and Michigan

4500 The last members of a dwarf race of Woolly Mammoths vanish from Wrangel Island near Alaska
ya

383 ya The last wild Aurochs die out

37 ya The Thylacine goes extinct in a Tasmanian zoo, the last member of the family Thylacinidae

See also
• Evolutionary history of life
• Evolutionary history of plants
• Extinction events
• Geologic time scale
• History of Earth
• Natural history
• Sociocultural evolution
• Timeline of human evolution
• Timeline of plant evolution

Further reading
• The Ancestor's Tale by Richard Dawkins, for a list of ancestors common to humans and other living species

References
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Mesoproterozoic/Neoproterozoic radiation of eukaryotes" (http:/ / paleobiol. geoscienceworld. org/ cgi/ content/ abstract/ 26/ 3/ 386)
[23] Hoffman, P.F.; Kaufman, A.J., Halverson, G.P., Schrag, D.P. (1998-08-28). "A Neoproterozoic Snowball Earth" (http:/ / www. sciencemag.
org/ cgi/ content/ full/ 281/ 5381/ 1342?ijkey=48d78da67bab492803c333f50c0dd84fbbef109c). Science 281 (5381): 1342.
doi:10.1126/science.281.5381.1342. PMID 9721097. . Retrieved 2007-05-04. Full online article (pdf 260 Kb) (http:/ / www. snowballearth.
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[24] Kirschvink, J.L. (1992). "Late Proterozoic low-latitude global glaciation: The snowball Earth" (http:/ / www. gps. caltech. edu/ ~jkirschvink/
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[26] Corsetti, F.A.; Awramik, S.M.; Pierce, D. (2003-04-15). "A complex microbiota from snowball Earth times: Microfossils from the
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[29] The Cambrian Period (http:/ / www. ucmp. berkeley. edu/ cambrian/ camb. html)
Timeline of evolution 91

[30] The Cambrian Explosion – Timing (http:/ / palaeo. gly. bris. ac. uk/ Palaeofiles/ Cambrian/ timing/ timing. html)
[31] Formation of the Ozone Layer (http:/ / jcbmac. chem. brown. edu/ myl/ ct7/ ozone/ ozone_formation. html)
[32] "The oldest fossils of footprints ever found on land hint that animals may have beaten plants out of the primordial seas. Lobster-sized,
centipede-like or slug like animals such as Protichnites and Climactichnites made the prints wading out of the ocean and scuttling over sand
dunes about 530 million years ago. Previous fossils indicated that animals didn't take this step until 40 million years later." Oldest fossil
footprints on land (http:/ / www. innovations-report. com/ html/ reports/ earth_sciences/ report-9641. html)
[33] "The oldest fossils reveal evolution of non-vascular plants by the middle to late Ordovician Period (~450–440 Ma) on the basis of fossil
spores" Transition of plants to land (http:/ / www. clas. ufl. edu/ users/ pciesiel/ gly3150/ plant. html)
[34] "The land plants evolved from the algae, more specifically green algae, as suggested by certain common biochemical traits" The first land
plants (http:/ / scitec. uwichill. edu. bb/ bcs/ bl14apl/ conq. htm)
[35] "The ancestry of sharks dates back more than 200 million years before the earliest known dinosaur. Introduction to shark evolution, geologic
time and age determination (http:/ / www. elasmo-research. org/ education/ evolution/ evol_s_predator. htm)
[36] Sahney, S. and Benton, M.J. (2008). "Recovery from the most profound mass extinction of all time" (http:/ / journals. royalsociety. org/
content/ qq5un1810k7605h5/ fulltext. pdf) (PDF). Proceedings of the Royal Society: Biological 275 (1636): 759. doi:10.1098/rspb.2007.1370.
PMID 18198148. PMC 2596898. .
[37] "Viruses of nearly all the major classes of organisms—animals, plants, fungi and bacteria/archaea—probably evolved with their hosts in the
seas, given that most of the evolution of life on this planet has occurred there. This means that viruses also probably emerged from the waters
with their different hosts, during the successive waves of colonisation of the terrestrial environment." Origins of Viruses (http:/ / www. mcb.
uct. ac. za/ tutorial/ virorig. html) (URL accessed on January 9, 2005)
[38] Chiappe, Luis M., & Dyke, Gareth J. (2002). "The Mesozoic Radiation of Birds". Annual Review of Ecology & Systematics 33: 91–124.
doi:10.1146/annurev.ecolsys.33.010802.150517.
[39] The Oldest Homo Sapiens: (http:/ / www. sciencedaily. com/ releases/ 2005/ 02/ 050223122209. htm) - URL retrieved May 15, 2009
[40] Alemseged, Z., Coppens, Y., Geraads, D. (2002). "Hominid cranium from Homo: Description and taxonomy of Homo-323-1976-896". Am J
Phys Anthropol 117 (2): 103–12. doi:10.1002/ajpa.10032. PMID 11815945.
[41] Stoneking, Mark; Soodyall, Himla (1996). "Human evolution and the mitochondrial genome". Current Opinion in Genetics & Development
6 (6): 731–6. doi:10.1016/S0959-437X(96)80028-1.
[42] "International Stratigraphic Chart" (http:/ / www. stratigraphy. org/ cheu. pdf). International Commission on Stratigraphy. . Retrieved
2009-02-03.

External links
• Berkeley Evolution (http://www.ucmp.berkeley.edu)
• Tree of Life Web Project (http://tolweb.org/Life_on_Earth/1) - explore complete phylogenetic tree
interactively
• A more compact timeline (http://www.talkorigins.org/origins/geo_timeline.html) at the TalkOrigins Archive
• Palaeos - The Trace of Life on Earth (http://www.palaeos.com)
• University of Waikato - Sequence of Plant Evolution (http://sci.waikato.ac.nz/evolution/plantEvolution.
shtml)
• University of Waikato - Sequence of Animal Evolution (http://sci.waikato.ac.nz/evolution/AnimalEvolution.
shtml)
• Graphical Timeline of evolution (http://www.wikitimescale.org/en/wiki/Evolution_on_Earth)
• History of Life on Earth (http://members.iinet.com.au/~drage/)
• Exploring Time (http://exploringtime.org/?page=segments) from Planck Time to the lifespan of the universe
• Interactive Plant Evolution Timeline (http://www.ensemble.ac.uk/projects/plantsci/timeline) - from the
University of Cambridge Ensemble Project
 92

History

History of evolutionary thought

Evolutionary thought, the conception that species change
over time, has roots in antiquity, in the ideas of the ancient
Greeks, Romans, and Chinese as well as in medieval
Islamic science. However, until the 18th century, Western
biological thinking was dominated by essentialism, the
belief that every species has essential characteristics that
are unalterable. This began to change during the
Enlightenment when evolutionary cosmology and the
mechanical philosophy spread from the physical sciences to
natural history. Naturalists began to focus on the variability
of species; the emergence of paleontology with the concept
of extinction further undermined the static view of nature.
In the early 19th century, Jean-Baptiste Lamarck proposed
his theory of the transmutation of species, the first fully
formed scientific theory of evolution.

In 1858, Charles Darwin and Alfred Russel Wallace

published a new evolutionary theory that was explained in
detail in Darwin's On the Origin of Species (1859). Unlike
Lamarck, Darwin proposed common descent and a
branching tree of life. The theory was based on the idea of
natural selection, and it synthesized a broad range of
evidence from animal husbandry, biogeography, geology,
morphology, and embryology. The Tree of Life as depicted by Ernst Haeckel in The Evolution
of Man (1879) illustrates the 19th-century view that evolution
The debate over Darwin's work led to the rapid acceptance was a progressive process leading towards man.
of the general concept of evolution, but the specific
mechanism he proposed, natural selection, was not widely accepted until it was revived by developments in biology
that occurred during 1920s through the 1940s. Before that time most biologists argued that other factors were
responsible for evolution. Alternatives to natural selection suggested during the eclipse of Darwinism included
inheritance of acquired characteristics (neo-Lamarckism), an innate drive for change (orthogenesis), and sudden
large mutations (saltationism). The synthesis of natural selection with Mendelian genetics during the 1920s and
1930s founded the new discipline of population genetics. Throughout the 1930s and 1940s, population genetics
became integrated with other biological fields, resulting in a widely applicable theory of evolution that encompassed
much of biology—the modern evolutionary synthesis.

Following the establishment of evolutionary biology, studies of mutation and variation in natural populations,
combined with biogeography and systematics, led to sophisticated mathematical and causal models of evolution.
Paleontology and comparative anatomy allowed more detailed reconstructions of the history of life. After the rise of
molecular genetics in the 1950s, the field of molecular evolution developed, based on protein sequences and
immunological tests, and later incorporating RNA and DNA studies. The gene-centered view of evolution rose to
History of evolutionary thought 93

prominence in the 1960s, followed by the neutral theory of molecular evolution, sparking debates over
adaptationism, the units of selection, and the relative importance of genetic drift versus natural selection. In the late
20th century, DNA sequencing led to molecular phylogenetics and the reorganization of the tree of life into the
three-domain system. In addition, the newly recognized factors of symbiogenesis and horizontal gene transfer
introduced yet more complexity into evolutionary history.

Antiquity

Greeks
Several ancient Greek philosophers discussed ideas that involved change in living organisms over time.
Anaximander (c.610–546 BC) proposed that the first animals lived in water and animals that live on land were
generated from them.[1] Empedocles (c. 490–430 BC) wrote of a non-supernatural origin for living things,[2]
suggesting that adaptation did not require an organizer or final cause. Aristotle summarized his idea: "Wherever then
all the parts came about just what they would have been if they had come to be for an end, such things survived,
being organized spontaneously in a fitting way; whereas those which grew otherwise perished and continue to
perish ..." although Aristotle himself rejected this view.[3]
Plato (c. 428–348 BC) was, in the words of biologist and historian Ernst Mayr,
"the great antihero of evolutionism",[4] as he established the philosophy of
essentialism, which he called the Theory of Forms. This theory holds that objects
observed in the real world are only reflections of a limited number of essences
(eide). Variation merely results from an imperfect reflection of these constant
essences. In his Timaeus, Plato set forth the idea that the Demiurge had created
the cosmos and everything in it because, being good, and hence, "... free from
jealousy, He desired that all things should be as like Himself as they could be".
The creator created all conceivable forms of life, since "... without them the
universe will be incomplete, for it will not contain every kind of animal which it
ought to contain, if it is to be perfect". This "plenitude principle"—the idea that
all potential forms of life are essential to a perfect creation—greatly influenced Plato (left) and Aristotle (right), a
Christian thought.[5] detail of The School of Athens

Aristotle (384–322 BC), one of the most influential of the Greek philosophers, is
the earliest natural historian whose work has been preserved in any real detail. His writings on biology resulted from
his research into natural history on and around the isle of Lesbos, and have survived in the form of four books,
usually known by their Latin names, De anima (on the essence of life), Historia animalium (inquiries about
animals), De generatione animalium (reproduction), and De partibus animalium (anatomy). Aristotle's works contain
some remarkably astute observations and interpretations—along with sundry myths and mistakes—reflecting the
uneven state of knowledge during his time.[6] However, for Charles Singer, "Nothing is more remarkable than
[Aristotle's] efforts to [exhibit] the relationships of living things as a scala naturæ."[6] This scala naturæ, described
in Historia animalium, classified organisms in relation to a hierarchical "Ladder of Life" or "Chain of Being",
placing them according to their complexity of structure and function, with organisms that showed greater vitality and
ability to move described as "higher organisms".[5]
History of evolutionary thought 94

Chinese
Ideas on changing biologic species were expressed by ancient Chinese thinkers such as Zhuangzi (Chuang Tzu), a
Taoist philosopher who lived around the 4th century BC. According to Joseph Needham, Taoism explicitly denies
the fixity of biological species and Taoist philosophers speculated that species had developed differing attributes in
response to differing environments.[7] Humans, nature and the heavens are seen as existing in a state of "constant
transformation" known as the Tao, in contrast with the more static view of nature typical of Western thought.[8]

Romans
Titus Lucretius Carus (d. 50 BC), the Roman philosopher and atomist, wrote the poem On the Nature of Things (De
rerum natura), which provides the best surviving explanation of the ideas of the Greek Epicurean philosophers. It
describes the development of the cosmos, the Earth, living things, and human society through purely naturalistic
mechanisms, without any reference to supernatural involvement. On the Nature of things would influence the
cosmological and evolutionary speculations of philosophers and scientists during and after the Renaissance.[9] [10]

Augustine of Hippo
In line with earlier Greek thought, the 4th century bishop and theologian, St. Augustine of Hippo, wrote that the
creation story in Genesis should not be read too literally. In his book De Genesi ad litteram ("On The Literal
Interpretation of Genesis"), he stated that in some cases new creatures may have come about through the
"decomposition" of earlier forms of life.[11] For Augustine, "plant, fowl and animal life are not perfect ... but created
in a state of potentiality", unlike what he considered the theologically perfect forms of angels, the firmament and the
human soul.[12] Augustine's idea 'that forms of life had been transformed "slowly over time"' prompted Father
Giuseppe Tanzella-Nitti, Professor of Theology at the Pontifical Santa Croce University in Rome, to claim that
Augustine had suggested a form of evolution.[13] [14]

Middle Ages

Islamic philosophy and the struggle for existence

Although Greek and Roman evolutionary ideas died out in Europe after the fall of the Roman Empire, they were not
lost to Islamic philosophers and scientists. In the Islamic Golden Age of the 8th to the 13th centuries, philosophers
explored ideas about natural history. These ideas included transmutation from non-living to living: "from mineral to
plant, from plant to animal, and from animal to man".[15]
The first Muslim biologist and philosopher to publish detailed speculations about natural history, the Afro-Arab
writer al-Jahiz, wrote in the 9th century. In the Book of Animals, he considered the effects of the environment on an
animal's chances for survival, and described the struggle for existence.[16] Al-Jahiz also wrote descriptions of food
chains.[17] Al-Jahiz speculated on the influence of the environment on animals and considered the effects of the
environment on the likelihood of an animal to survive. For example, Al-Jahiz's wrote in his Book of Animals: "All
animals, in short, can not exist without food, neither can the hunting animal escape being hunted in his turn. Every
weak animal devours those weaker than itself. Strong animals cannot escape being devoured by other animals
stronger than they."[16]
History of evolutionary thought 95

Christian philosophy and the great chain of being

During the Early Middle Ages, Greek classical learning was all but lost
to the West. However, contact with the Islamic world, where Greek
manuscripts were preserved and expanded, soon led to a massive spate
of Latin translations in the 12th century. Europeans were re-introduced
to the works of Plato and Aristotle, as well as to Islamic thought.
Christian thinkers of the scholastic school, in particular Abelard and
Thomas Aquinas, combined Aristotelian classification with Plato's
ideas of the goodness of God, and of all potential life forms being
present in a perfect creation, to organize all inanimate, animate, and
spiritual beings into a huge interconnected system: the scala naturæ, or
great chain of being.[5] [18]

Within this system, everything that existed could be placed in order,

from "lowest" to "highest", with Hell at the bottom and God at the
top—below God, an angelic hierarchy marked by the orbits of the
planets, mankind in an intermediate position, and worms the lowest of
the animals. As the universe was ultimately perfect, the great chain was
Drawing of the great chain of being from also perfect. There were no empty links in the chain, and no link was
Rhetorica Christiana (1579) by Diego Valades
represented by more than one species. Therefore no species could ever
move from one position to another. Thus, in this Christianized version
of Plato's perfect universe, species could never change, but remained forever fixed, in accordance with the text of
Genesis. For humans to forget their position was seen as sinful, whether they behaved like lower animals or aspired
to a higher station than was given them by their Creator.[5]

Creatures on adjacent steps were expected to closely resemble each other, an idea expressed in the saying: natura
non facit saltum ("nature does not make leaps").[5] This basic concept of the great chain of being greatly influenced
the thinking of Western civilization for centuries (and still has an influence today). It formed a part of the argument
from design presented by natural theology. As a classification system, it became the major organizing principle and
foundation of the emerging science of biology in the 17th and 18th centuries.[5]

Thomas Aquinas on creation and natural processes

While the development of the great chain of being and the argument from design by Christian theologians
contributed to the view that the natural world fit into an unchanging designed hierarchy, some theologians were more
open to the possibility that the world might have developed through natural processes. Thomas Aquinas went even
farther than Augustine of Hippo in arguing that scriptural texts like Genesis should not be interpreted in a literal way
that conflicted with or constrained what natural philosophers learned about the workings of the natural world. He felt
that the autonomy of nature was a sign of God's goodness and that there was no conflict between the concept of a
divinely created universe, and the idea that the universe may have evolved over time through natural mechanisms.[19]
However, Aquinas disputed the views of those like the ancient Greek philosopher Empodocles who held that such
natural processes showed that the universe could have developed without an underlying purpose. Rather holding
that: "Hence, it is clear that nature is nothing but a certain kind of art, i.e., the divine art, impressed upon things, by
which these things are moved to a determinate end. It is as if the shipbuilder were able to give to timbers that by
which they would move themselves to take the form of a ship."[20]
History of evolutionary thought 96

Renaissance and Enlightenment

In the first half of the 17th century, René Descartes's mechanical
philosophy encouraged the use of the metaphor of the universe as a
machine, a concept that would come to characterise the scientific
revolution.[21] Between 1650 and 1800, some evolutionist theories
supported the view that the universe, including life on Earth, had
developed mechanically, entirely without divine guidance. In contrast,
most contemporary theories of evolution, such of those of Gottfried
Leibniz and J. G. Herder, held that evolution was a fundamentally
spiritual process.[22] In 1751, Pierre Louis Maupertuis veered toward
more materialist ground. He wrote of natural modifications occurring Pierre Belon compared the skeletons of birds and
during reproduction and accumulating over the course of many humans in his Book of Birds (1555).

generations, producing races and even new species, a description that

anticipated in general terms the concept of natural selection.[23]

Later in the 18th century, the French philosopher G. L. L. Buffon, one of the leading 18th century naturalists,
suggested that what most people referred to as species were really just well-marked varieties, modified from an
original form by environmental factors. For example, he believed that lions, tigers, leopards and house cats might all
have a common ancestor. He further speculated that the 200 or so species of mammals then known might have
descended from as few as 38 original animal forms. Buffon's evolutionary ideas were limited; he believed each of the
original forms had arisen through spontaneous generation and that each was shaped by "internal moulds" that limited
the amount of change. Buffon's works, Natural History and The Epochs of Nature, containing well developed
theories about a completely materialistic origin for the Earth and his ideas questioning the fixity of species, were
extremely influential.[24] [25] Between 1767 and 1792, James Burnett, Lord Monboddo included in his writings not
only the concept that man had descended from primates, but also that, in response to the environment, creatures had
found methods of transforming their characteristics over long time intervals.[26] Charles Darwin's grandfather,
Erasmus Darwin, published Zoönomia in 1796, which suggested that "all warm-blooded animals have arisen from
one living filament".[27] In his 1802 poem Temple of Nature, he described the rise of life from minute organisms
living in mud to all of its modern diversity.[28]
History of evolutionary thought 97

Early 19th century

Paleontology and geology

In 1796, Georges Cuvier published his findings on the differences
between living elephants and those found in the fossil record. His
analysis demonstrated that mammoths and mastodons were distinct
species, different from any living animal, effectively ending a
long-running debate over whether the extinction of a species was
possible.[29] In 1788, James Hutton described gradual geological
processes operating continuously over deep time.[30] In the 1790s
William Smith began the process of ordering rock strata by examining
fossils in the layers while he worked on his geologic map of England.
Independently, in 1811, Georges Cuvier and Alexandre Brongniart
published an influential study of the geologic history of the region
around Paris, based on the stratigraphic succession of rock layers.
These works helped establish the antiquity of the Earth.[31] Cuvier
advocated catastrophism to explain the patterns of extinction and
faunal succession revealed by the fossil record.

Knowledge of the fossil record continued to advance rapidly during the

Diagram of the geologic timescale from an 1861 first few decades of the 19th century. By the 1840s, the outlines of the
book by Richard Owen showing the appearance geologic timescale were becoming clear, and in 1841 John Phillips
of major animal types
named three major eras, based on the predominant fauna of each: the
Paleozoic, dominated by marine invertebrates and fish, the Mesozoic,
the age of reptiles, and the current Cenozoic age of mammals. This progressive picture of the history of life was
accepted even by conservative English geologists like Adam Sedgwick and William Buckland; however, like Cuvier,
they attributed the progression to repeated catastrophic episodes of extinction followed by new episodes of
creation.[32] Unlike Cuvier, Buckland and some other advocates of natural theology among British geologists made
efforts to explicitly link the last catastrophic episode proposed by Cuvier to the biblical flood.[33] [34]

From 1830 to 1833, Charles Lyell published his multi-volume work Principles of Geology, which, building on
Hutton's ideas, advocated a uniformitarian alternative to the catastrophic theory of geology. Lyell claimed that, rather
than being the products of cataclysmic (and possibly supernatural) events, the geologic features of the Earth are
better explained as the result of the same gradual geologic forces observable in the present day—but acting over
immensely long periods of time. Although Lyell opposed evolutionary ideas (even questioning the consensus that the
fossil record demonstrates a true progression), his concept that the Earth was shaped by forces working gradually
over an extended period, and the immense age of the Earth assumed by his theories, would strongly influence future
evolutionary thinkers such as Charles Darwin.[35]
History of evolutionary thought 98

Transmutation of species
Jean-Baptiste Lamarck proposed, in his Philosophie Zoologique of
1809, a theory of the transmutation of species. Lamarck did not believe
that all living things shared a common ancestor but rather that simple
forms of life were created continuously by spontaneous generation. He
also believed that an innate life force drove species to become more
complex over time, advancing up a linear ladder of complexity that
was related to the great chain of being. Lamarck recognized that
species were adapted to their environment. He explained this by saying
that the same innate force driving increasing complexity caused the
organs of an animal (or a plant) to change based on the use or disuse of
those organs, just as muscles are affected by exercise. He argued that
these changes would be inherited by the next generation and produce
slow adaptation to the environment. It was this secondary mechanism
of adaptation through the inheritance of acquired characteristics that
would become known as Lamarckism and would influence discussions
of evolution into the 20th century.[36] [37]

A radical British school of comparative anatomy that included the

anatomist Robert Grant was closely in touch with Lamarck's French
school of Transformationism. One of the French scientists who
Diagram from Vestiges of the Natural History of
influenced Grant was the anatomist Étienne Geoffroy Saint-Hilaire, Creation (1844) by Robert Chambers shows a
whose ideas on the unity of various animal body plans and the model of development where fish (F), reptiles
homology of certain anatomical structures would be widely influential (R), and birds (B) represent branches from a path
leading to mammals (M).
and lead to intense debate with his colleague Georges Cuvier. Grant
became an authority on the anatomy and reproduction of marine
invertebrates. He developed Lamarck's and Erasmus Darwin's ideas of transmutation and evolutionism, and
investigated homology, even proposing that plants and animals had a common evolutionary starting point. As a
young student Charles Darwin joined Grant in investigations of the life cycle of marine animals. In 1826 an
anonymous paper, probably written by Robert Jameson, praised Lamarck for explaining how higher animals had
"evolved" from the simplest worms; this was the first use of the word "evolved" in a modern sense.[38] [39]

In 1844, the Scottish publisher Robert Chambers anonymously published an extremely controversial but widely read
book entitled Vestiges of the Natural History of Creation. This book proposed an evolutionary scenario for the
origins of the Solar System and life on Earth. It claimed that the fossil record showed a progressive ascent of animals
with current animals being branches off a main line that leads progressively to humanity. It implied that the
transmutations lead to the unfolding of a preordained plan that had been woven into the laws that governed the
universe. In this sense it was less completely materialistic than the ideas of radicals like Robert Grant, but its
implication that humans were only the last step in the ascent of animal life incensed many conservative thinkers. The
high profile of the public debate over Vestiges, with its depiction of evolution as a progressive process, would greatly
influence the perception of Darwin's theory a decade later.[40] [41]

Ideas about the transmutation of species were associated with the radical materialism of the Enlightenment and were
attacked by more conservative thinkers. Georges Cuvier attacked the ideas of Lamarck and Geoffroy Saint-Hilaire,
agreeing with Aristotle that species were immutable. Cuvier believed that the individual parts of an animal were too
closely correlated with one another to allow for one part of the anatomy to change in isolation from the others, and
argued that the fossil record showed patterns of catastrophic extinctions followed by re-population, rather than
gradual change over time. He also noted that drawings of animals and animal mummies from Egypt, which were
History of evolutionary thought 99

thousands of years old, showed no signs of change when compared with modern animals. The strength of Cuvier's
arguments and his scientific reputation helped keep transmutational ideas out of the mainstream for decades.[42]
In Britain the philosophy of natural theology remained influential.
William Paley's 1802 book Natural Theology with its famous
watchmaker analogy had been written at least in part as a response to
the transmutational ideas of Erasmus Darwin.[43] Geologists influenced
by natural theology, such as Buckland and Sedgwick, made a regular
practice of attacking the evolutionary ideas of Lamarck, Grant, and The
This 1847 diagram by Richard Owen shows his Vestiges of the Natural History of Creation.[44] [45] Although the
conceptual archetype for all vertebrates.
geologist Charles Lyell opposed scriptural geology, he also believed in
the immutability of species, and in his Principles of Geology
(1830–1833), he criticized Lamarck's theories of development.[35] Idealists such as Louis Agassiz and Richard Owen
believed that each species was fixed and unchangeable because it represented an idea in the mind of the creator.
They believed that relationships between species could be discerned from developmental patterns in embryology, as
well as in the fossil record, but that these relationships represented an underlying pattern of divine thought, with
progressive creation leading to increasing complexity and culminating in humanity. Owen developed the idea of
"archetypes" in the Divine mind that would produce a sequence of species related by anatomical homologies, such as
vertebrate limbs. Owen led a public campaign that successfully marginalized Robert Grant in the scientific
community. Darwin would make good use of the homologies analyzed by Owen in his own theory, but the harsh
treatment of Grant, and the controversy surrounding Vestiges, showed him the need to ensure that his own ideas were
scientifically sound.[39] [46] [47]

Anticipations of natural selection

Several writers anticipated aspects of Darwin's theory, and in the third edition of On the Origin of Species published
in 1861 Darwin named those he knew about in an introductory appendix, An Historical Sketch of the Recent
Progress of Opinion on the Origin of Species, which he expanded in later editions.[48]
In 1813, William Charles Wells read before the Royal Society essays assuming that there had been evolution of
humans, and recognising the principle of natural selection. Charles Darwin and Alfred Russel Wallace were unaware
of this work when they jointly published the theory in 1858, but Darwin later acknowledged that Wells had
recognised the principle before them, writing that the paper "An Account of a White Female, part of whose Skin
resembles that of a Negro" was published in 1818, and "he distinctly recognises the principle of natural selection,
and this is the first recognition which has been indicated; but he applies it only to the races of man, and to certain
characters alone."[49] When Darwin was developing his theory, he was influenced by Augustin de Candolle's natural
system of classification, which laid emphasis on the war between competing species.[50] [51]
Patrick Matthew wrote in the obscure book Naval Timber & Arboriculture (1831) of "continual balancing of life to
circumstance. ... [The] progeny of the same parents, under great differences of circumstance, might, in several
generations, even become distinct species, incapable of co-reproduction."[52] Charles Darwin discovered this work
after the initial publication of the Origin. In the brief historical sketch that Darwin included in the 3rd edition he says
"Unfortunately the view was given by Mr. Matthew very briefly in an Appendix to a work on a different subject ...
He clearly saw, however, the full force of the principle of natural selection."[53]
It is possible to look through the history of biology from the ancient Greeks onwards and discover anticipations of
almost all of Darwin's key ideas. However, as historian of science Peter J. Bowler says, "Through a combination of
bold theorizing and comprehensive evaluation, Darwin came up with a concept of evolution that was unique for the
time." Bowler goes on to say that simple priority alone is not enough to secure a place in the history of science;
someone has to develop an idea and convince others of its importance to have a real impact.[54]
T. H. Huxley said in his essay on the reception of the Origin of Species:
History of evolutionary thought 100

The suggestion that new species may result from the selective action of external conditions upon the
variations from their specific type which individuals present and which we call spontaneous because we
are ignorant of their causation is as wholly unknown to the historian of scientific ideas as it was to
biological specialists before 1858. But that suggestion is the central idea of the Origin of Species, and
contains the quintessence of Darwinism.[55]

Natural selection
The biogeographical patterns Charles Darwin observed
in places such as the Galapagos islands during the
voyage of the Beagle caused him to doubt the fixity of
species, and in 1837 Darwin started the first of a series
of secret notebooks on transmutation. Darwin's
observations led him to view transmutation as a process
of divergence and branching, rather than the ladder-like
progression envisioned by Lamarck and others. In 1838
he read the new 6th edition of An Essay on the
Principle of Population, written in the late 18th century
by Thomas Malthus. Malthus' idea of population
growth leading to a struggle for survival combined with
Darwin's knowledge on how breeders selected traits,
led to the inception of Darwin's theory of natural
selection. Darwin did not publish his ideas on evolution Darwin's first sketch of an evolutionary tree from his First Notebook
for 20 years. However he did share them with certain on Transmutation of Species (1837)

other naturalists and friends, starting with Joseph

Hooker, with whom he discussed his unpublished 1844 essay on natural selection. During this period he used the
time he could spare from his other scientific work to slowly refine his ideas and, aware of the intense controversy
around transmutation, amass evidence to support them. In September 1854 he began full time work on writing his
book on natural selection.[47] [56] [57]

Unlike Darwin, Alfred Russel Wallace, influenced by the book Vestiges of the Natural History of Creation, already
suspected that transmutation of species occurred when he began his career as a naturalist. By 1855 his
biogeographical observations during his field work in South America and the Malay Archipelago made him
confident enough in a branching pattern of evolution to publish a paper stating that every species originated in close
proximity to an already existing closely allied species. Like Darwin, it was Wallace's consideration of how the ideas
of Malthus might apply to animal populations that led him to conclusions very similar to those reached by Darwin
about the role of natural selection. In February 1858 Wallace, unaware of Darwin's unpublished ideas, composed his
thoughts into an essay and mailed them to Darwin, asking for his opinion. The result was the joint publication in July
of an extract from Darwin's 1844 essay along with Wallace's letter. Darwin also began work on a short abstract
summarising his theory, which he would publish in 1859 as On the Origin of Species.[58]
History of evolutionary thought 101

1859–1930s: Darwin and his legacy

By the 1850s whether or not species evolved was a subject of
intense debate, with prominent scientists arguing both sides of the
issue.[59] However, it was the publication of Charles Darwin's On
the Origin of Species (1859) that fundamentally transformed the
discussion over biological origins.[60] Darwin argued that his
branching version of evolution explained a wealth of facts in
biogeography, anatomy, embryology, and other fields of biology.
He also provided the first cogent mechanism by which
evolutionary change could persist: his theory of natural
selection.[61]

One of the first and most important naturalists to be convinced by

Origin of the reality of evolution was the British anatomist
Thomas Henry Huxley. Huxley recognized that unlike the earlier
transmutational ideas of Lamarck and Vestiges, Darwin's theory
provided a mechanism for evolution without supernatural
involvement, even if Huxley himself was not completely
convinced that natural selection was the key evolutionary
mechanism. Huxley would make advocacy of evolution a
Diagram by O.C. Marsh of the evolution of horse feet
and teeth over time as reproduced in T.H Huxley's cornerstone of the program of the X Club to reform and
1876 book Professor Huxley in America professionalise science by displacing natural theology with
naturalism and to end the domination of British natural science by
the clergy. By the early 1870s in English-speaking countries, thanks partly to these efforts, evolution had become the
mainstream scientific explanation for the origin of species.[61] In his campaign for public and scientific acceptance of
Darwin's theory, Huxley made extensive use of new evidence for evolution from paleontology. This included
evidence that birds had evolved from reptiles, including the discovery of Archaeopteryx in Europe, and a number of
fossils of primitive birds with teeth found in North America. Another important line of evidence was the finding of
fossils that helped trace the evolution of the horse from its small five-toed ancestors.[62] However, acceptance of
evolution among scientists in non-English speaking nations such as France, and the countries of southern Europe and
Latin America was slower. An exception to this was Germany, where both August Weismann and Ernst Haeckel
championed this idea: Haeckel used evolution to challenge the established tradition of metaphysical idealism in
German biology, much as Huxley used it to challenge natural theology in Britain.[63] Haeckel and other German
scientists would take the lead in launching an ambitious programme to reconstruct the evolutionary history of life
based on morphology and embryology.[64]

Darwin's theory succeeded in profoundly altering scientific opinion regarding the development of life and in
producing a small philosophical revolution.[65] However, this theory could not explain several critical components of
the evolutionary process. Specifically, Darwin was unable to explain the source of variation in traits within a species,
and could not identify a mechanism that could pass traits faithfully from one generation to the next. Darwin's
hypothesis of pangenesis, while relying in part on the inheritance of acquired characteristics, proved to be useful for
statistical models of evolution that were developed by his cousin Francis Galton and the "biometric" school of
evolutionary thought. However, this idea proved to be of little use to other biologists.[66]
History of evolutionary thought 102

Application to humans
Charles Darwin was aware of the severe reaction in
some parts of the scientific community against the
suggestion made in Vestiges of the Natural History of
Creation that humans had arisen from animals by a
process of transmutation. Therefore he almost
completely ignored the topic of human evolution in The
Origin of Species. Despite this precaution, the issue
featured prominently in the debate that followed the
book's publication. For most of the first half of the 19th
century, the scientific community believed that,
This illustration was the frontispiece of Thomas Henry Huxley's
although geology had shown that the Earth and life book Evidence as to Man's Place in Nature (1863).
were very old, human beings had appeared suddenly
just a few thousand years before the present. However, a series of archaeological discoveries in the 1840s and 1850s
showed stone tools associated with the remains of extinct animals. By the early 1860s, as summarized in Charles
Lyell's 1863 book Geological Evidences of the Antiquity of Man, it had become widely accepted that humans had
existed during a prehistoric period – which stretched many thousands of years before the start of written history.
This view of human history was more compatible with an evolutionary origin for humanity than was the older view.
On the other hand, at that time there was no fossil evidence to demonstrate human evolution. The only human fossils
found before the discovery of Java man in the 1890s were either of anatomically modern humans or of Neanderthals
that were too close, especially in the critical characteristic of cranial capacity, to modern humans for them to be
convincing intermediates between humans and other primates.[67]

Therefore the debate that immediately followed the publication of The Origin of Species centered on the similarities
and differences between humans and modern apes. Carolus Linnaeus had been criticised in the 18th century for
grouping humans and apes together as primates in his ground breaking classification system.[68] Richard Owen
vigorously defended the classification suggested by Cuvier and Johann Friedrich Blumenbach that placed humans in
a separate order from any of the other mammals, which by the early 19th century had become the orthodox view. On
the other hand, Thomas Henry Huxley sought to demonstrate a close anatomical relationship between humans and
apes. In one famous incident, Huxley showed that Owen was mistaken in claiming that the brains of gorillas lacked a
structure present in human brains. Huxley summarized his argument in his highly influential 1863 book Evidence as
to Man's Place in Nature. Another viewpoint was advocated by Charles Lyell and Alfred Russel Wallace. They
agreed that humans shared a common ancestor with apes, but questioned whether any purely materialistic
mechanism could account for all the differences between humans and apes, especially some aspects of the human
mind.[67]
In 1871, Darwin published The Descent of Man, and Selection in Relation to Sex, which contained his views on
human evolution. Darwin argued that the differences between the human mind and the minds of the higher animals
were a matter of degree rather than of kind. For example, he viewed morality as a natural outgrowth of instincts that
were beneficial to animals living in social groups. He argued that all the differences between humans and apes were
explained by a combination of the selective pressures that came from our ancestors moving from the trees to the
plains, and sexual selection. The debate over human origins, and over the degree of human uniqueness continued
well into the 20th century.[67]
History of evolutionary thought 103

Alternatives to natural selection

The concept of evolution was widely accepted in scientific circles
within a few years of the publication of Origin, but the acceptance
of natural selection as its driving mechanism was much less
widespread. The four major alternatives to natural selection in the
late 19th century were theistic evolution, neo-Lamarckism,
orthogenesis, and saltationism. Theistic evolution (a term
promoted by Darwin's greatest American advocate Asa Gray) was
the idea that God intervened in the process of evolution to guide it
in such a way that the living world could still be considered to be
designed. However, this idea gradually fell out of favor among
scientists, as they became more and more committed to the idea of
methodological naturalism and came to believe that direct appeals
to supernatural involvement were scientifically unproductive. By
1900, theistic evolution had largely disappeared from professional
scientific discussions, although it retained a strong popular
This photo from Henry Fairfield Osborn's 1918 book
following.[69] [70]
Origin and Evolution of Life shows models depicting
In the late 19th century, the term neo-Lamarckism came to be
the evolution of Titanothere horns over time, which
associated with the position of naturalists who viewed the
Osborn claimed was an example of an orthogenic trend
in evolution. inheritance of acquired characteristics as the most important
evolutionary mechanism. Advocates of this position included the
British writer and Darwin critic Samuel Butler, the German biologist Ernst Haeckel, and the American paleontologist
Edward Drinker Cope. They considered Lamarckism to be philosophically superior to Darwin's idea of selection
acting on random variation. Cope looked for, and thought he found, patterns of linear progression in the fossil
record. Inheritance of acquired characteristics was part of Haeckel's recapitulation theory of evolution, which held
that the embryological development of an organism repeats its evolutionary history.[69] [70] Critics of
neo-Lamarckism, such as the German biologist August Weismann and Alfred Russel Wallace, pointed out that no
one had ever produced solid evidence for the inheritance of acquired characteristics. Despite these criticisms,
neo-Lamarckism remained the most popular alternative to natural selection at the end of the 19th century, and would
remain the position of some naturalists well into the 20th century.[69] [70]

Orthogenesis was the hypothesis that life has an innate tendency to change, in a unilinear fashion, towards
ever-greater perfection. It had a significant following in the 19th century, and its proponents included the Russian
biologist Leo Berg and the American paleontologist Henry Fairfield Osborn. Orthogenesis was popular among some
paleontologists, who believed that the fossil record showed a gradual and constant unidirectional change.
Saltationism was the idea that new species arise as a result of large mutations. It was seen as a much faster
alternative to the Darwinian concept of a gradual process of small random variations being acted on by natural
selection, and was popular with early geneticists such as Hugo de Vries, William Bateson, and early in his career, T.
H. Morgan. It became the basis of the mutation theory of evolution.[69] [70]
History of evolutionary thought 104

Mendelian genetics, biometrics, and mutation

The so-called rediscovery of Gregor Mendel's laws of inheritance
in 1900 ignited a fierce debate between two camps of biologists. In
one camp were the Mendelians, who were focused on discrete
variations and the laws of inheritance. They were led by William
Bateson (who coined the word genetics) and Hugo de Vries (who
coined the word mutation). Their opponents were the
biometricians, who were interested in the continuous variation of
characteristics within populations. Their leaders, Karl Pearson and
Walter Frank Raphael Weldon, followed in the tradition of Francis
Galton, who had focused on measurement and statistical analysis
of variation within a population. The biometricians rejected Diagram from T.H. Morgan's 1919 book The Physical
Basis of Heredity, showing the sex-linked inheritance
Mendelian genetics on the basis that discrete units of heredity,
of the white-eyed mutation in Drosophila
such as genes, could not explain the continuous range of variation melanogaster
seen in real populations. Weldon's work with crabs and snails
provided evidence that selection pressure from the environment
could shift the range of variation in wild populations, but the Mendelians maintained that the variations measured by
biometricians were too insignificant to account for the evolution of new species.[71] [72]

When T. H. Morgan began experimenting with breeding the fruit fly Drosophila melanogaster, he was a saltationist
who hoped to demonstrate that a new species could be created in the lab by mutation alone. Instead, the work at his
lab between 1910 and 1915 reconfirmed Mendelian genetics and provided solid experimental evidence linking it to
chromosomal inheritance. His work also demonstrated that most mutations had relatively small effects, such as a
change in eye color, and that rather than creating a new species in a single step, mutations served to increase
variation within the existing population.[71] [72]

1920s–1940s

Biston betularia f. typica is the white-bodied form of the peppered moth.

Biston betularia f. carbonaria is the black-bodied form of the peppered moth.

History of evolutionary thought 105

Population genetics
The Mendelian and biometrician models were eventually reconciled with the development of population genetics. A
key step was the work of the British biologist and statistician R.A. Fisher. In a series of papers starting in 1918 and
culminating in his 1930 book The Genetical Theory of Natural Selection, Fisher showed that the continuous variation
measured by the biometricians could be produced by the combined action of many discrete genes, and that natural
selection could change gene frequencies in a population, resulting in evolution. In a series of papers beginning in
1924, another British geneticist, J.B.S. Haldane, applied statistical analysis to real-world examples of natural
selection, such as the evolution of industrial melanism in peppered moths, and showed that natural selection worked
at an even faster rate than Fisher assumed.[73] [74]
The American biologist Sewall Wright, who had a background in animal breeding experiments, focused on
combinations of interacting genes, and the effects of inbreeding on small, relatively isolated populations that
exhibited genetic drift. In 1932, Wright introduced the concept of an adaptive landscape and argued that genetic drift
and inbreeding could drive a small, isolated sub-population away from an adaptive peak, allowing natural selection
to drive it towards different adaptive peaks. The work of Fisher, Haldane and Wright founded the discipline of
population genetics. This integrated natural selection with Mendelian genetics, which was the critical first step in
developing a unified theory of how evolution worked.[73] [74]

Modern evolutionary synthesis

In the first few decades of the 20th century, most field naturalists continued to believe that Lamarckian and
orthogenic mechanisms of evolution provided the best explanation for the complexity they observed in the living
world. But as the field of genetics continued to develop, those views became less tenable.[75] Theodosius
Dobzhansky, a postdoctoral worker in T. H. Morgan's lab, had been influenced by the work on genetic diversity by
Russian geneticists such as Sergei Chetverikov. He helped to bridge the divide between the foundations of
microevolution developed by the population geneticists and the patterns of macroevolution observed by field
biologists, with his 1937 book Genetics and the Origin of Species. Dobzhansky examined the genetic diversity of
wild populations and showed that, contrary to the assumptions of the population geneticists, these populations had
large amounts of genetic diversity, with marked differences between sub-populations. The book also took the highly
mathematical work of the population geneticists and put it into a more accessible form. In Great Britain E.B. Ford,
the pioneer of ecological genetics, continued throughout the 1930s and 1940s to demonstrate the power of selection
due to ecological factors including the ability to maintain genetic diversity through genetic polymorphisms such as
human blood types. Ford's work would contribute to a shift in emphasis during the course of the modern synthesis
towards natural selection over genetic drift.[73] [74] [76] [77]
Evolutionary biologist Ernst Mayr was influenced by the work of the German biologist Bernhard Rensch showing
the influence of local environmental factors on the geographic distribution of sub-species and closely related species.
Mayr followed up on Dobzhansky's work with the 1942 book Systematics and the Origin of Species, which
emphasized the importance of allopatric speciation in the formation of new species. This form of speciation occurs
when the geographical isolation of a sub-population is followed by the development of mechanisms for reproductive
isolation. Mayr also formulated the biological species concept that defined a species as a group of interbreeding or
potentially interbreeding populations that were reproductively isolated from all other populations.[73] [74] [78]
In the 1944 book Tempo and Mode in Evolution, George Gaylord Simpson showed that the fossil record was
consistent with the irregular non-directional pattern predicted by the developing evolutionary synthesis, and that the
linear trends that earlier paleontologists had claimed supported orthogenesis and neo-Lamarckism did not hold up to
closer examination. In 1950, G. Ledyard Stebbins published Variation and Evolution in Plants, which helped to
integrate botany into the synthesis. The emerging cross-disciplinary consensus on the workings of evolution would
be known as the modern evolutionary synthesis. It received its name from the book Evolution: The Modern Synthesis
by Julian Huxley.[73] [74]
History of evolutionary thought 106

The evolutionary synthesis provided a conceptual core—in particular, natural selection and Mendelian population
genetics—that tied together many, but not all, biological disciplines. It helped establish the legitimacy of
evolutionary biology, a primarily historical science, in a scientific climate that favored experimental methods over
historical ones.[79] The synthesis also resulted in a considerable narrowing of the range of mainstream evolutionary
thought (what Stephen Jay Gould called the "hardening of the synthesis"): by the 1950s, natural selection acting on
genetic variation was virtually the only acceptable mechanism of evolutionary change (panselectionism), and
macroevolution was simply considered the result of extensive microevolution.[80] [81]

1940s–1960s: Molecular biology and evolution

The middle decades of the 20th century saw the rise of molecular biology, and with it an understanding of the
chemical nature of genes as sequences of DNA and their relationship, through the genetic code, to protein sequences.
At the same time, increasingly powerful techniques for analyzing proteins, such as protein electrophoresis and
sequencing, brought biochemical phenomena into realm of the synthetic theory of evolution. In the early 1960s,
biochemists Linus Pauling and Emile Zuckerkandl proposed the molecular clock hypothesis: that sequence
differences between homologous proteins could be used to calculate the time since two species diverged. By 1969,
Motoo Kimura and others provided a theoretical basis for the molecular clock, arguing that—at the molecular level
at least—most genetic mutations are neither harmful nor helpful and that genetic drift, rather than natural selection,
is responsible for a large portion of genetic change: the neutral theory of molecular evolution.[82] Studies of protein
differences within species also brought molecular data to bear on population genetics by providing estimates of the
level of heterozygosity in natural populations.[83]
From the early 1960s, molecular biology was increasingly seen as a threat to the traditional core of evolutionary
biology. Established evolutionary biologists—particularly Ernst Mayr, Theodosius Dobzhansky and G. G. Simpson,
three of the architects of the modern synthesis—were extremely skeptical of molecular approaches, especially when
it came to the connection (or lack thereof) to natural selection. The molecular clock hypothesis and the neutral theory
were particularly controversial, spawning the neutralist-selectionist debate over the relative importance of drift and
selection, which continued into the 1980s without a clear resolution.[84] [85]

Late 20th century

Gene-centered view
In the mid-1960s, George C. Williams strongly critiqued explanations of adaptations worded in terms of "survival of
the species" (group selection arguments). Such explanations were largely replaced by a gene-centered view of
evolution, epitomized by the kin selection arguments of W. D. Hamilton, George R. Price and John Maynard
Smith.[86] This viewpoint would be summarized and popularized in the influential 1976 book The Selfish Gene by
Richard Dawkins.[87] Models of the period showed that group selection was severely limited in its strength; though
newer models do admit the possibility of significant multi-level selection.[88]
In 1973, Leigh Van Valen proposed the term "Red Queen", which he took from Through the Looking-Glass by
Lewis Carroll, to describe a scenario where a species involved in one or more evolutionary arms races would have to
constantly change just to keep pace with the species with which it was co-evolving. Hamilton, Williams and others
suggested that this idea might explain the evolution of sexual reproduction: the increased genetic diversity caused by
sexual reproduction would help maintain resistance against rapidly evolving parasites, thus making sexual
reproduction common, despite the tremendous cost from the gene-centric point of view of a system where only half
of an organism's genome is passed on during reproduction.[89] [90] The gene-centric view has also led to an increased
interest in Darwin's old idea of sexual selection,[91] and more recently in topics such as sexual conflict and
intragenomic conflict.
History of evolutionary thought 107

Sociobiology
W. D. Hamilton's work on kin selection contributed to the emergence of the discipline of sociobiology. The
existence of altruistic behaviors has been a difficult problem for evolutionary theorists from the beginning.[92]
Significant progress was made in 1964 when Hamilton formulated the inequality in kin selection known as
Hamilton's rule, which showed how eusociality in insects (the existence of sterile worker classes) and many other
examples of altruistic behavior could have evolved through kin selection. Other theories followed, some derived
from game theory, such as reciprocal altruism.[93] In 1975, E.O. Wilson published the influential and highly
controversial book Sociobiology: The New Synthesis which claimed evolutionary theory could help explain many
aspects of animal, including human, behavior. Critics of sociobiology, including Stephen Jay Gould and Richard
Lewontin, claimed that sociobiology greatly overstated the degree to which complex human behaviors could be
determined by genetic factors. They also claimed that the theories of sociobiologists often reflected their own
ideological biases. Despite these criticisms, work has continued in sociobiology and the related discipline of
evolutionary psychology, including work on other aspects of the altruism problem.[94] [95]

Evolutionary paths and processes

One of the most prominent debates arising during the
1970s was over the theory of punctuated equilibrium.
Niles Eldredge and Stephen Jay Gould proposed that
there was a pattern of fossil species that remained
largely unchanged for long periods (what they termed
stasis), interspersed with relatively brief periods of
rapid change during speciation.[96] [97] Improvements
in sequencing methods resulted in a large increase of
sequenced genomes, allowing the testing and refining
of evolutionary theories using this huge amount of A phylogenetic tree showing the three-domain system. Eukaryotes
[98] are colored red, Archaea green, and Bacteria blue.
genome data. Comparisons between these genomes
provide insights into the molecular mechanisms of
speciation and adaptation.[99] [100] These genomic analyses have produced fundamental changes in the understanding
of the evolutionary history of life, such as the proposal of the three-domain system by Carl Woese.[101] Advances in
computational hardware and software allow the testing and extrapolation of increasingly advanced evolutionary
models and the development of the field of systems biology.[102] One of the results has been an exchange of ideas
between theories of biological evolution and the field of computer science known as evolutionary computation,
which attempts to mimic biological evolution for the purpose of developing new computer algorithms. Discoveries
in biotechnology now allow the modification of entire genomes, advancing evolutionary studies to the level where
future experiments may involve the creation of entirely synthetic organisms.[103]

Microbiology, horizontal gene transfer, and endosymbiosis

Microbiology was largely ignored by early evolutionary theory. This was due to the paucity of morphological traits
and the lack of a species concept in microbiology, particularly amongst prokaryotes.[104] Now, evolutionary
researchers are taking advantage of their improved understanding of microbial physiology and ecology, produced by
the comparative ease of microbial genomics, to explore the taxonomy and evolution of these organisms.[105] These
studies are revealing unanticipated levels of diversity amongst microbes.[106] [107]
One particularly important outcome from studies on microbial evolution was the discovery in Japan of horizontal
gene transfer in 1959.[108] This transfer of genetic material between different species of bacteria was first recognized
because it played a major role in the spread of antibiotic resistance.[109] More recently, as knowledge of genomes has
History of evolutionary thought 108

continued to expand, it has been suggested that lateral transfer of genetic material has played an important role in the
evolution of all organisms.[110] These high levels of horizontal gene transfer have led to suggestions that the family
tree of today's organisms, the so-called "tree of life", is more similar to an interconnected web or net.[111] [112]
Indeed, as part of the endosymbiotic theory for the origin of organelles, a form of horizontal gene transfer has been a
critical step in the evolution of eukaryotes such as fungi, plants, and animals.[113] [114] The endosymbiotic theory
holds that organelles within the cells of eukorytes such as mitochondria and chloroplasts, had descended from
independent bacteria that came to live symbiotically within other cells. It had been suggested in the late 19th century
when similarities between mitochondria and bacteria were noted, but largely dismissed until it was revived and
championed by Lynn Margulis in the 1960s and 70s; Margulis was able to make use of new evidence that such
organelles had their own DNA that was inherited independently from that in the cell's nucleus.[115]

Evolutionary developmental biology

In the 1980s and 1990s the tenets of the modern evolutionary synthesis came under increasing scrutiny. There was a
renewal of structuralist themes in evolutionary biology in the work of biologists such as Brian Goodwin and Stuart
Kauffman, which incorporated ideas from cybernetics and systems theory, and emphasized the self-organizing
processes of development as factors directing the course of evolution. The evolutionary biologist Stephen Jay Gould
revived earlier ideas of heterochrony, alterations in the relative rates of developmental processes over the course of
evolution, to account for the generation of novel forms, and, with the evolutionary biologist Richard Lewontin, wrote
an influential paper in 1979 suggesting that a change in one biological structure, or even a structural novelty, could
arise incidentally as an accidental result of selection on another structure, rather than through direct selection for that
particular adaptation. They called such incidental structural changes "spandrels" after an architectural feature.[116]
Later, Gould and Vrba discussed the acquisition of new functions by novel structures arising in this fashion, calling
them "exaptations".[117]
Molecular data regarding the mechanisms underlying development accumulated rapidly during the 1980s and '90s. It
became clear that the diversity of animal morphology was not the result of different sets of proteins regulating the
development of different animals, but from changes in the deployment of a small set of proteins that were common
to all animals.[118] These proteins became known as the "developmental toolkit".[119] Such perspectives influenced
the disciplines of phylogenetics, paleontology and comparative developmental biology, and spawned the new
discipline of evolutionary developmental biology.[120]
More recent work in this field by Mary Jane West-Eberhard has emphasized phenotypic and developmental
plasticity.[121] It has been suggested, for example, that the rapid emergence of basic animal body plans in the
Cambrian explosion was due in part to changes in the environment acting on inherent material properties of cell
aggregates, such as differential cell adhesion and biochemical oscillation. The resulting forms were later stabilized
by natural selection.[122] Experimental and theoretical research on these and related ideas have been presented in the
multi-authored volume Origination of Organismal Form.

21st century

Epigenetic inheritance
Yet another area where developmental biology has led to the questioning of some tenets of the modern evolutionary
synthesis is in the field of epigenetics, the study of how environmental factors affect the way genes express
themselves during development. By the first decade of the 21st century it had become accepted that in some cases
such environmental factors could affect the expression of genes in subsequent generations even though the offspring
were not exposed to the same environmental factors, and there had been no genetic changes. This shows that in some
cases non genetic changes to an organism can be inherited and it has been suggested that such inheritance can help
with adaptation to local conditions and affect evolution.[123] [124] Some have suggested that in some cases a form of
History of evolutionary thought 109

Lamarckian evolution may occur.[125]

Unconventional evolutionary theory

Omega Point
Pierre Teilhard de Chardin's metaphysical Omega Point Theory describes the gradual development of the universe
from subatomic particles to human society, which he viewed as its final stage and goal.

Gaia hypothesis
Teilhard de Chardin's ideas have been seen as being connected to the more specific Gaia theory by James Lovelock,
who proposed that the living and nonliving parts of Earth can be viewed as a complex interacting system with
similarities to a single organism.[126] The Gaia hypothesis has also been viewed by Lynn Margulis[127] and others as
an extension of endosymbiosis and exosymbiosis.[128] This modified hypothesis postulates that all living things have
a regulatory effect on the Earth's environment that promotes life overall.

Transhumanism
Futurists have often viewed scientific and technological progress as a continuation of biological evolution. Among
these, transhumanists often view such technological evolution itself as a goal in their philosophy, possibly in the
form of a technological singularity.

See also
• Faith and rationality
• Galápagos Islands
• The Voyage of the Beagle

Notes
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[2] Campbell, Gordon. "Empedocles" (http:/ / www. iep. utm. edu/ e/ empedocl. htm#H4). Internet Encyclopedia of Philosophy. . Retrieved
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[3] Hardie, R.P.; R. K. Gaye. "Physics by Aristotle" (http:/ / classics. mit. edu/ Aristotle/ physics. 2. ii. html). . Retrieved 2008-07-15.
[4] Mayr 1982, p. 304
[5] Johnston, Ian (1999). "Section Three: The Origins of Evolutionary Theory" (http:/ / records. viu. ca/ ~johnstoi/ darwin/ sect3. htm). ... And
Still We Evolve: A Handbook on the History of Modern Science. Liberal Studies Department, Malaspina University College. . Retrieved
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[6] Singer 1931
[7] Needham & Ronan 1995, p. 101
[8] Miller, James (January 8, 2008). "Daoism and Nature" (http:/ / www. jamesmiller. ca/ RAS lecture on daoism and nature. pdf) (PDF). Royal
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[9] Sedley, David (August 4, 2004). "Lucretius" (http:/ / plato. stanford. edu/ entries/ lucretius/ ). Stanford Encyclopedia of Philosophy. .
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[10] Simpson, David (2006). "Lucretius" (http:/ / www. iep. utm. edu/ l/ lucretiu. htm). The Internet Encyclopedia of Philosophy. . Retrieved
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[11] Augustine 1982, pp. 89–90
[12] Gill 2005, p. 251
[13] Owen, Richard (2009-02-11). "Vatican buries the hatchet with Charles Darwin" (http:/ / www. timesonline. co. uk/ tol/ comment/ faith/
article5705331. ece). London: Times Online. . Retrieved 2009-02-12.
[14] Irvine, Chris (2009-02-12). "The Vatican claims Darwin's theory of evolution is compatible with Christianity" (http:/ / www. telegraph. co.
uk/ news/ newstopics/ religion/ 4588289/ The-Vatican-claims-Darwins-theory-of-evolution-is-compatible-with-Christianity. html). London:
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[15] "Medieval and Renaissance Concepts of Evolution and Paleontology" (http:/ / www. ucmp. berkeley. edu/ history/ medieval. html).
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[17] Frank N. Egerton, "A History of the Ecological Sciences, Part 6: Arabic Language Science – Origins and Zoological", Bulletin of the
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[24] Bowler 2003, pp. 75–80
[25] Larson 2004, pp. 14–15
[26] Henderson 2000
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[41] Bowler & Morus 2005, pp. 142–143
[42] Larson 2004, pp. 5–24
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www. genome. org/ cgi/ pmidlookup?view=long& pmid=15965028). Genome Res. 15 (7): 954–9. doi:10.1101/gr.3666505. PMID 15965028.
PMC 1172039. .
[112] Doolittle WF, Bapteste E (February 2007). "Pattern pluralism and the Tree of Life hypothesis" (http:/ / www. pnas. org/ cgi/
pmidlookup?view=long& pmid=17261804). Proc. Natl. Acad. Sci. U.S.A. 104 (7): 2043–9. doi:10.1073/pnas.0610699104. PMID 17261804.
PMC 1892968. .
[113] Poole A, Penny D (2007). "Evaluating hypotheses for the origin of eukaryotes". Bioessays 29 (1): 74–84. doi:10.1002/bies.20516.
PMID 17187354.
[114] Dyall S, Brown M, Johnson P (2004). "Ancient invasions: from endosymbionts to organelles". Science 304 (5668): 253–7.
doi:10.1126/science.1094884. PMID 15073369.
[115] "Endosymbiosis: Lynn Margulis" (http:/ / evolution. berkeley. edu/ evolibrary/ article/ _0_0/ history_24). University of California Berkely.
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[116] Gould SJ (1997). "The exaptive excellence of spandrels as a term and prototype" (http:/ / www. pubmedcentral. nih. gov/ articlerender.
fcgi?tool=pubmed& pubmedid=11038582). Proc. Natl. Acad. Sci. U.S.A. 94 (20): 10750–5. doi:10.1073/pnas.94.20.10750. PMID 11038582.
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[117] Gould SJ and Vrba ES (1982). "Exaptation—a missing term in the science of form". Paleobiology 8 (1): 4–15.
[118] True JR, Carroll SB (2002). "Gene co-option in physiological and morphological evolution". Annu. Rev. Cell Dev. Biol. 18: 53–80.
doi:10.1146/annurev.cellbio.18.020402.140619. PMID 12142278.
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doi:10.1038/nrg2226. PMID 18007650.
[120] Baguñà J, Garcia-Fernàndez J (2003). "Evo-Devo: the long and winding road" (http:/ / www. ijdb. ehu. es/ web/ paper.
php?doi=14756346). Int. J. Dev. Biol. 47 (7–8): 705–13. PMID 14756346. .
*Gilbert SF (2003). "The morphogenesis of evolutionary developmental biology". Int. J. Dev. Biol. 47 (7–8): 467–77. PMID 14756322.
[121] West-Eberhard, M-J (2003). Developmental Plasticity and Evolution. Oxford University Press.
[122] Newman SA, Müller GB (2000). "Epigenetic mechanisms of character origination". J. Exp. Zool. B Mol. Develop. Evol. 288 (4): 304–17.
doi:10.1002/1097-010X(20001215)288:4<304::AID-JEZ3>3.0.CO;2-G. PMID 11144279.
[123] Roberts, Christina. "Epigenetics and Evolution" (http:/ / web. me. com/ christinalrichards/ Portfolio/ Epigenetics. html). South Florida
University. . Retrieved 2010-02-21.
[124] Rapp, Ryan; Wendell, Jonathan. "Epigenetics and Plant Evolution" (http:/ / www3. interscience. wiley. com/ journal/ 118647390/ abstract).
New Phytologist. . Retrieved 2010-02-21.
[125] Singer, Emily (2009). "A Comeback for Lamarckian Evolution?" (http:/ / www. technologyreview. com/ biomedicine/ 22061/ ). MIT
Technology Review. . Retrieved 2010-02-21.
[126] Lovelock J (2003). "Gaia: the living Earth". Nature 426 (6968): 769–70. doi:10.1038/426769a. PMID 14685210.
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History of evolutionary thought 113

References
• Augustine (1982). The Literal Meaning of Genesis (http://books.google.com/?id=_s0kIgD0nCcC). trans. John
Hammond Taylor. The Newman Press. ISBN 0809103265, 9780809103263.
• Bowler, Peter J. (2003). Evolution: The History of an Idea (3rd ed.). University of California Press.
ISBN 0-52023693-9.
• Bowler, Peter J.; Morus, Iwan Rhys (2005). Making Modern Science. The University of Chicago Press.
ISBN 0-226-06861-7.
• Darlington, Cyril (1959). Darwin's place in history. Blackwell, Oxford, p85.
• Darwin, Charles (1859). On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured
Races in the Struggle for Life (1st ed.). John Murray, London.
• Darwin, Charles (1861). On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured
Races in the Struggle for Life (3rd ed.). John Murray, London.
• Darwin, Charles (1866). On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured
Races in the Struggle for Life (4th ed.). John Murray, London.
• Darwin, Charles (1872). On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured
Races in the Struggle for Life (6th ed.). John Murray, London.
• Darwin, Erasmus (1825). The Temple of Nature, or The Origin of Society (http://books.google.com/
?id=oAl9y-0FSJQC&dq=Erasmus+Darwin+Temple). Jones & Company.
• Darwin, Erasmus (1818). Zoonomia (http://www.gutenberg.org/files/15707/15707-h/15707-h.htm).
• Desmond, Adrian; Moore, James (1994). Darwin: The Life of a Tormented Evolutionist. W. W. Norton &
Company. ISBN 0393311503.
• Gill, Meredith Jane (2005). Augustine in the Italian Renaissance: Art and Philosophy from Petrarch to
Michelangelo (http://books.google.com/?id=AksE4jKI8yQC). Cambridge University Press.
ISBN 0521832144, ISBN 9780521832144.
• Gould, Stephen Jay (2002). The Structure of Evolutionary Theory. Belknap Press of Harvard University Press.
ISBN 0-674-00613-5.
• Henderson, Jan-Andrew (2000). The Emperor's Kilt: The Two Secret Histories of Scotland. Mainstream
Publishing.
• Larson, Edward J. (2004). Evolution: The Remarkable History of a Scientific Theory. Modern Library.
ISBN 0-679-64288-9.
• Lovejoy, Arthur (1936). The Great Chain of Being: A Study of the History of an Idea. Harvard University Press.
ISBN 0-674-36153-9.
• Mayr, Ernst (1982). The Growth of Biological Thought: Diversity, Evolution, and Inheritance. The Belknap Press
of Harvard University Press. ISBN 0-674-36445-7.
• Mayr, Ernst; Provine, W. B., eds (1998). The Evolutionary Synthesis: Perspectives on the Unification of Biology.
Harvard University Press. ISBN 0-674-27225-0.
• Needham, Joseph; Ronan, Colin Alistair (1995). The Shorter Science and Civilisation in China: An Abridgement
of Joseph Needham's Original Text, Vol. 1. Cambridge University Press. ISBN 0521292867.
• Sapp, Jan (2003). Genesis: The Evolution of Biology. Oxford University Press. ISBN 0-19-515618-8.
• Secord, James A. (2000). Victorian Sensation: The Extraordinary Publication, Reception, and Secret Authorship
of Vestiges of the Natural History of Creation. University of Chicago Press. ISBN 0-226-74410-8.
• Singer, Charles (1931). A Short History of Biology. Clarendon Press.
• Smocovitis, Vassiliki Betty (1996). Unifying Biology: The Evolutionary Synthesis and Evolutionary Biology.
Princeton University Press. ISBN 0-691-03343-9.
History of evolutionary thought 114

External links
• UC Berkeley's History of Evolutionary Thought (http://evolution.berkeley.edu/evolibrary/article/history_01)
• Darwin's precursors and influences by John Wilkins (http://www.talkorigins.org/faqs/darwin-precursors.
html). Part of the Talk.Origins Archive.
• The Alfred Russel Wallace Page (http://www.wku.edu/~smithch/index1.htm)

Lamarckism
Lamarckism (or Lamarckian inheritance) is the idea that an organism can pass on characteristics that it acquired
during its lifetime to its offspring (also known as heritability of acquired characteristics or soft inheritance). It is
named after the French biologist Jean-Baptiste Lamarck (1744–1829), who incorporated the action of soft
inheritance into his evolutionary theories. He is often incorrectly cited as the founder of soft inheritance, which
proposes that individual efforts during the lifetime of the organisms were the main mechanism driving species to
adaptation, as they supposedly would acquire adaptive changes and pass them on to offspring. After publication of
Charles Darwin's theory of natural selection, the importance of individual efforts in the generation of adaptation was
considerably diminished. Later, Mendelian genetics supplanted the notion of inheritance of acquired traits,
eventually leading to the development of the modern evolutionary synthesis, and the general abandonment of the
Lamarckian theory of evolution in biology. In a wider context, soft inheritance is of use when examining the
evolution of cultures and ideas, and is related to the theory of Memetics.

History
Between 1794 and 1796 Erasmus Darwin wrote Zoönomia suggesting
"that all warm-blooded animals have arisen from one living filament...
with the power of acquiring new parts" in response to stimuli, with
each round of "improvements" being inherited by successive
generations. Subsequently Jean-Baptiste Lamarck repeated in his
Philosophie Zoologique of 1809 the folk wisdom that characteristics
which were "needed" were acquired (or diminished) during the lifetime
of an organism then passed on to the offspring. He incorporated this
mechanism into his thoughts on evolution, seeing it as resulting in the
adaptation of life to local environments.

Lamarck founded a school of French Transformationism which

Jean-Baptiste Lamarck
included Étienne Geoffroy Saint-Hilaire, and which corresponded with
a radical British school of anatomy based in the extramural anatomy
schools in Edinburgh which included the surgeon Robert Knox and the comparative anatomist Robert Edmund
Grant. In addition, the Regius Professor of Natural History, Robert Jameson, was the probable author of an
anonymous paper in 1826 praising "Mr. Lamarck" for explaining how the higher animals had "evolved" from the
"simplest worms" – this was the first use of the word "evolved" in a modern sense. As a young student, Charles
Darwin was tutored by Grant, and worked with him on marine creatures.

The Vestiges of the Natural History of Creation, authored by Robert Chambers in St Andrews and published
anonymously in England in 1844, proposed a theory which combined radical phrenology with Lamarckism, causing
political controversy for its radicalism and unorthodoxy, but exciting popular interest and preparing a huge and
prosperous audience for Darwin.
Lamarckism 115

Darwin's Origin of Species proposed natural selection as the main mechanism for development of species, but did
not rule out a variant of Lamarckism as a supplementary mechanism.[1] Darwin called his Lamarckian hypothesis
Pangenesis, and explained it in the final chapter of his book Variation in Plants and Animals under Domestication,
after describing numerous examples to demonstrate what he considered to be the inheritance of acquired
characteristics. Pangenesis, which he emphasised was a hypothesis, was based on the idea that somatic cells would,
in response to environmental stimulation (use and disuse), throw off 'gemmules' or 'pangenes' which travelled around
the body (though not necessarily in the bloodstream). These pangenes were microscopic particles that supposedly
contained information about the characteristics of their parent cell, and Darwin believed that they eventually
accumulated in the germ cells where they could pass on to the next generation the newly acquired characteristics of
the parents. Darwin's half-cousin, Francis Galton carried out experiments on rabbits, with Darwin's cooperation, in
which he transfused the blood of one variety of rabbit into another variety in the expectation that its offspring would
show some characteristics of the first. They did not, and Galton declared that he had disproved Darwin's hypothesis
of Pangenesis, but Darwin objected, in a letter to Nature, that he had done nothing of the sort, since he had never
mentioned blood in his writings. He pointed out that he regarded Pangenesis as occurring in Protozoa and plants,
which have no blood.[2] With the development of the modern synthesis of the theory of evolution and a lack of
evidence for either a mechanism or even the heritability of acquired characteristics, Lamarckism largely fell from
favor.
In the 1920s, experiments by Paul Kammerer on amphibians, particularly the midwife toad, appeared to find
evidence supporting Lamarckism, but his specimens with supposedly-acquired black foot-pads were found to have
been tampered with. In The Case of the Midwife Toad Arthur Koestler surmised that the specimens had been faked
by a Nazi sympathiser to discredit Kammerer for his political views.
A form of Lamarckism was revived in the Soviet Union of the 1930s when Trofim Lysenko promoted Lysenkoism
which suited the ideological opposition of Joseph Stalin to Genetics. This ideologically driven research influenced
Soviet agricultural policy which in turn was later blamed for crop failures.
Since 1988 certain scientists have produced work proposing that Lamarckism could apply to single celled organisms.
A version of Lamarckian acquisition in higher order animals is still posited in certain branches of psychology, as, for
example, in the Jungian racial memory.
Neo-Lamarckism is a theory of inheritance based on a modification and extension of Lamarckism, essentially
maintaining the principle that genetic changes can be influenced and directed by environmental factors.

Lamarck's theory
The identification of Lamarckism with the inheritance of acquired
characteristics is regarded by some as an artifact of the subsequent
history of evolutionary thought, repeated in textbooks without analysis.
Stephen Jay Gould wrote that late 19th century evolutionists "re-read
Lamarck, cast aside the guts of it ... and elevated one aspect of the
mechanics - inheritance of acquired characters - to a central focus it
never had for Lamarck himself."[3] He argued that "the restriction of
"Lamarckism" to this relatively small and non-distinctive corner of
Lamarck's thought must be labelled as more than a misnomer, and
truly a discredit to the memory of a man and his much more The evolution of necks is often used as the
example in explanations of Lamarckism.
comprehensive system"[4] . Gould advocated defining "Lamarckism"
more broadly, in line with Lamarck's overall evolutionary theory.

Lamarck incorporated two ideas into his theory of evolution, in his day considered to be generally true:
Lamarckism 116

1. Use and disuse – Individuals lose characteristics they do not require (or use) and develop characteristics that are
useful.
2. Inheritance of acquired traits – Individuals inherit the traits of their ancestors.
Examples of what is traditionally called "Lamarckism" would include:
• Giraffes stretching their necks to reach leaves high in trees (especially Acacias), strengthen and gradually
lengthen their necks. These giraffes have offspring with slightly longer necks (also known as "soft inheritance").
• A blacksmith, through his work, strengthens the muscles in his arms. His sons will have similar muscular
development when they mature.
With this in mind, Lamarck has been credited in some textbooks and popular culture with developing two laws:
1. In every animal which has not passed the limit of its development, a more frequent and continuous use of any
organ gradually strengthens, develops and enlarges that organ, and gives it a power proportional to the length of
time it has been so used; while the permanent disuse of any organ imperceptibly weakens and deteriorates it, and
progressively diminishes its functional capacity, until it finally disappears.
2. All the acquisitions or losses wrought by nature on individuals, through the influence of the environment in which
their race has long been placed, and hence through the influence of the predominant use or permanent disuse of
any organ; all these are preserved by reproduction to the new individuals which arise, provided that the acquired
modifications are common to both sexes, or at least to the individuals which produce the young.[5]
In essence, a change in the environment brings about change in "needs" (besoins), resulting in change in behavior,
bringing change in organ usage and development, bringing change in form over time — and thus the gradual
transmutation of the species.
However, as historians of science such as Michael Ghiselin and Stephen Jay Gould have pointed out, none of these
views were original to Lamarck.[6] [7] On the contrary, Lamarck's contribution was a systematic theoretical
framework for understanding evolution. He saw evolution as comprising two processes;
1. Le pouvoir de la vie (a complexifying force) - in which the natural, alchemical movements of fluids would etch
out organs from tissues, leading to ever more complex construction regardless of the organ's use or disuse. This
would drive organisms from simple to complex forms.
2. L'influence des circonstances (an adaptive force) - in which the use and disuse of characters led organisms to
become more adapted to their environment. This would take organisms sideways off the path from simple to
complex, specialising them for their environment.

Current views on "Lamarckism"

Interest in Lamarckism has recently increased, as several studies in the field of epigenetics have highlighted the
possible inheritance of behavioral traits acquired by the previous generation. Some recent notable studies include
those made by the University of Linköping, Sweden, which have looked at foraging behavior in chickens as well as
stress factors[8] . The conclusion of the referenced study is as follows:
Our findings suggest that unpredictable food access caused seemingly adaptive responses in feeding
behavior, which may have been transmitted to the offspring by means of epigenetic mechanisms,
including regulation of immune genes. This may have prepared the offspring for coping with an
unpredictable environment.... Transmissions of information across generations which does not involve
traditional inheritance of DNA-sequence alleles is often referred to as soft inheritance [9] or 'Lamarckian
inheritance'.[8]
On a much smaller scale, genetic exchange without reproduction between single-celled organisms has been
well-researched and is termed horizontal gene transfer.
The group of researchers at The University of Linköping again highlighted the apparent link between food intake and
cross-generational inheritance of acquired traits. This link has been shown before in studies of human populations
Lamarckism 117

who have experienced starvation, where epigenetic factors have altered the functioning of genes[10] . These changed
epigenetic factors appear to show traits in the next generation such as an increased occurrence of diabetes. The
process of methylation is thought to be behind such changes.
In October 2010, further evidence linking food intake to traits inherited by the offspring were shown in a study of
rats conducted by several Australian universities[11] . The study strongly suggested that fathers can transfer a
propensity for obesity to their daughters as a result of the fathers' food intake, and not their genetics (or specific
genes), prior to the conception of the daughter. A "paternal high-fat diet" was shown to cause cell dysfunction in the
daughter, which in turn led to obesity for the daughter.
Several historians have argued that Lamarck's name is linked somewhat unfairly to the theory that has come to bear
his name, and that Lamarck deserves credit for being an influential early proponent of the concept of biological
evolution, far more than for the mechanism of evolution, in which he simply followed the accepted wisdom of his
time. Lamarck died 30 years before the first publication of Charles Darwin's Origin of Species. According to Stephen
Jay Gould, if Lamarck had been aware of Darwin's proposed mechanism of natural selection, there is no reason to
assume he would not have accepted it as a more likely alternative to his own mechanism. Note also that Darwin, like
Lamarck, lacked a plausible alternative mechanism of inheritance - the particulate nature of inheritance was only
observed by Gregor Mendel somewhat later, and published in 1866. Its full significance was not appreciated until the
Modern evolutionary synthesis in the early 1920s. An important point in its favour at the time was that Lamarck's
theory contained a mechanism describing how variation is maintained, which Darwin’s own theory lacked.
Several recent studies, one conducted by researchers at MIT and another by researchers at the Tufts University
School of Medicine, have rekindled the debate once again. As reported [12] in MIT's Technology Review in February
2009, "The effects of an animal's environment during adolescence can be passed down to future offspring ... The
findings provide support for a 200-year-old theory of evolution that has been largely dismissed: Lamarckian
evolution, which states that acquired characteristics can be passed on to offspring."

Neo-Lamarckism
Unlike neo-Darwinism, the term neo-Lamarckism refers more to a loose grouping of largely heterodox theories and
mechanisms that emerged after Lamarck's time, than to any coherent body of theoretical work.
In the 1920s, Harvard University researcher William McDougall studied the abilities of rats to correctly solve mazes.
He found that children of rats that had learned the maze were able to run it faster. The first rats would get it wrong
165 times before being able to run it perfectly each time, but after a few generations it was down to 20. McDougall
attributed this to some sort of Lamarckian evolutionary process.[13] Oscar Werner Tiegs and Wilfred Eade Agar later
showed McDougall's results to be incorrect, caused by poor experimental controls.[14] [15] [16] [17] [18]
At around the same time, Ivan Pavlov, who was also a Lamarckist, claimed to have observed a similar phenomenon
in animals being subject to conditioned reflex experiments. He claimed that with each generation, the animals
became easier to condition. However, Pavlov never suggested a mechanism to explain these observations.
Soma to germ-line feedback
In the 1970s the immunologist Ted Steele, formerly of the University of Wollongong, and colleagues, proposed a
neo-Lamarckian mechanism to try to explain why homologous DNA sequences from the VDJ gene regions of parent
mice were found in their germ cells and seemed to persist in the offspring for a few generations. The mechanism
involved the somatic selection and clonal amplification of newly acquired antibody gene sequences that were
generated via somatic hyper-mutation in B-cells. The mRNA products of these somatically novel genes were
captured by retroviruses endogenous to the B-cells and were then transported through the blood stream where they
could breach the soma-germ barrier and retrofect (reverse transcribe) the newly acquired genes into the cells of the
germ line. Although Steele was advocating this theory for the better part of two decades, little more than indirect
evidence was ever acquired to support it. An interesting attribute of this idea is that it strongly resembles Darwin's
Lamarckism 118

own theory of pangenesis, except in the soma to germ line feedback theory, pangenes are replaced with realistic
retroviruses.[19]
Epigenetic inheritance
Forms of 'soft' or epigenetic inheritance within organisms have been suggested as neo-Lamarckian in nature by such
scientists as Eva Jablonka and Marion J. Lamb. In addition to 'hard' or genetic inheritance, involving the duplication
of genetic material and its segregation during meiosis, there are other hereditary elements that pass into the germ
cells also. These include things like methylation patterns in DNA and chromatin marks, both of which regulate the
activity of genes. These are considered "Lamarckian" in the sense that they are responsive to environmental stimuli
and can differentially affect gene expression adaptively, with phenotypic results that can persist for many
generations in certain organisms. Although the reality of epigenetic inheritance is not doubted (as countless
experiments have validated it), its significance to the evolutionary process is uncertain. Most neo-Darwinians
consider epigenetic inheritance mechanisms to be little more than a specialized form of phenotypic plasticity, with
no potential to introduce evolutionary novelty into a species lineage.[20]

Lamarckism and single-celled organisms

While Lamarckism has been discredited as an evolutionary influence for larger lifeforms, some scientists
controversially argue that it can be observed among microorganisms.[21] Whether such mutations are directed or not
also remains in contention. (see Horizontal Gene Transfer)
In 1988, John Cairns at the Radcliffe Infirmary in Oxford, England, and a group of other scientists renewed the
Lamarckian controversy (which at that point had been a dead debate for many years).[22] The group took a mutated
strain of E. coli that was unable to consume the sugar lactose and placed it in an environment where lactose was the
only food source. They observed over time that mutations occurred within the colony at a rate that suggested the
bacteria were overcoming their handicap by altering their own genes. Cairns, among others, dubbed the process
adaptive mutation.
If bacteria that had overcome their own inability to consume lactose passed on this "learned" trait to future
generations, it could be argued as a form of Lamarckism; though Cairns later chose to distance himself from such a
position.[23] More typically, it might be viewed as a form of ontogenic evolution.
There has been some research into Lamarckism and prions. A group of researchers, for example, discovered that in
yeast cells containing a specific prion protein Sup35, the yeast were able to gain new genetic material, some of
which gave them new abilities such as resistance to a particular herbicide. When the researchers mated the yeast cells
with cells not containing the prion, the trait reappeared in some of the resulting offspring, indicating that some
information indeed was passed down, though whether or not the information is genetic is debatable: trace prion
amounts in the cells may be passed to their offspring, giving the appearance of a new genetic trait where there is
none.[24]
Finally, there is growing evidence that cells can activate low-fidelity DNA polymerases in times of stress to induce
mutations. While this does not directly confer advantage to the organism on the organismal level, it makes sense at
the gene-evolution level. While the acquisition of new genetic traits is random, and selection remains Darwinian, the
active process of identifying the necessity to mutate is considered to be Lamarckian.

Lamarckism and societal change

Jean Molino (2000) has proposed that Lamarckian evolution may be accurately applied to cultural evolution. This
was also previously suggested by Peter Medawar (1959) and Conrad Waddington (1961). K. N. Laland and
colleagues have recently suggested that human culture can be looked upon as an ecological niche like phenomena,
where the effects of cultural niche construction are transmissible from one generation to the next. One interpretation
of the Meme theory is that memes are both Darwinian and Lamarckian in nature, as in addition to being subject to
Lamarckism 119

selection pressures based on their ability to differentially influence Human minds, memes can be modified and the
effects of that modification passed on. Richard Dawkins notes (in Blackmore 2000: The Meme machine, page 13),
that Memes can be copied in a Lamarckian way (copying of the product) or in a Weismann-type evolutionary way
(copying of the instruction) which is much more resistant against changes.

See also
• Jean-Baptiste Lamarck
• Baldwinian evolution
• Darwinism
• Epigenetic inheritance
• Epigenetics
• Evolution
• Inheritance of acquired characters
• Lysenkoism
• Memetics
• Obsolete scientific theories
• Orthogenesis
• Marcus Pembrey
• Racial memory
• Ted Steele
• History of evolutionary thought
• Eclipse of Darwinism

Notes
[1] Desmond, A. & Moore, J. (1991) Darwin Penguin Books p.617 "Darwin was loathe to let go of the notion that a well-used and strengthened
organ could be inherited"
[2] Charles Darwin (27 April 1871). "Pangenesis" (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F1751&
pageseq=1). Nature. A Weekly Illustrated Journal of Science. pp. 502–503. . Retrieved 2007-11-08.
[3] Gould, Stephen J. "Shades of Lamarck", reprinted in The Panda's Thumb (1980) pp.65-71. Quote from page 66.
[4] Gould, Stephen J. (2002). The Structure of Evolutionary Theory. Harvard: Belknap Harvard. pp. 177–178. ISBN 0-674-00613-5.
[5] Jean-Baptiste Lamarck Zoological Philosophy trans. Hugh Elliot, U. Chicago Press, 1984, p.113
[6] The Imaginary Lamarck: a look at bogus "history" in schoolbooks (http:/ / www. textbookleague. org/ 54marck. htm) by Michael Ghiselin
[7] Gould, S.J. (2002) The Structure of Evolutionary Theory
[8] http:/ / www. plosone. org/ article/ info:doi/ 10. 1371/ journal. pone. 0006405
[9] Richards EJ (2006) Inherited epigenetic variation–revisiting soft inheritance. Nat Rev Genet 7(5): 395–401.
[10] http:/ / cat. inist. fr/ ?aModele=afficheN& cpsidt=3596539
[11] http:/ / www. nature. com/ nature/ journal/ v467/ n7318/ full/ nature09491. html
[12] http:/ / www. technologyreview. com/ biomedicine/ 22061
[13] McDougall, 1938. British Journal of Psychology 28:321-345
[14] Pantin, C F A (November 1957). "Oscar Werner Tiegs". Biographical Memiors of Fellows of the Royal Society (The Royal Society) 3: 247.
[15] W E Agar, F H Drummond (1935). "First report on a test of McDougall's Lamarckian experiment on the training of rats". Journal of
Experimental Biology 12: 191.
[16] W E Agar, F H Drummond (1942). "Second report on a test of McDougall's Lamarckian experiment on the training of rats". Journal of
Experimental Biology 19: 158.
[17] W E Agar, F H Drummond (1948). "Third report on a test of McDougall's Lamarckian experiment on the training of rats". Journal of
Experimental Biology 25: 103.
[18] W E Agar, F H Drummond, M M Gunson (1954). "Fourth (final) report on a test of McDougall's Lamarckian experiment on the training of
rats". Journal of Experimental Biology 31: 308.
[19] Lamarck's Signature: how retrogenes are changing Darwin's natural selection paradigm. Edward J. Steele, Robyn A. Lindley, Robert V.
Blanden. Perseus Books, 1998
[20] Epigenetic Inheritance and Evolution: The Lamarckian Dimension. Eva Jablonka, Marion J. Lamb. Oxford University Press, 1995
[21] Adaptive mutation Genetics, Vol. 148, April 1998
Lamarckism 120

[22] http:/ / www. mun. ca/ biochem/ courses/ 4103/ topics/ adaptive_mutation. html Adaptive mutation in bacteria
[23] Adaptive mutation in E. coli, Journal of Bacteriology, August 2004, Vol. 186, No. 15
[24] Lamarckism and prions, New Scientist, 21 August 2004, Issue #2461

Further references
• Burkeman, Oliver. Why everything you've been told about evolution is wrong (http://www.guardian.co.uk/
science/2010/mar/19/evolution-darwin-natural-selection-genes-wrong), The Guardian, March 19, 2010.
• Desmond, Adrian (1989). The Politics of Evolution: Morphology, Medicine, and Reform in Radical London.
Chicago: University of Chicago Press. ISBN 0-226-14374-0.
• Gould, Stephen J. (2002). The Structure of Evolutionary Theory. Harvard: Belknap Harvard. pp. 170–197 on
Lamarck. ISBN 0-674-00613-5.
• Medawar, Peter (1959). "The threat and the glory". BBC Reith Lectures No. 6.
• Molino, Jean (2000). "Toward an Evolutionary Theory of Music and Language". In Brown, Merker & Wallin
(Eds.), The Origins of Music, ISBN 0-262-23206-5.
• Waddington, Conrad (1961). "The human evolutionary system". In: Michael Banton (Ed.), Darwinism and the
Study of Society. London: Tavistock.
• Cairns, J., J. Overbaugh, and S. Miller. 1988. Nature 335: 142-145
• Culotta, Elizabeth; "A Boost for 'Adaptive' Mutation", Science, 265:318, 1994.
• Vetsigian K, Woese C, Goldenfeld N. 2006. "Collective Evolution and the Genetic Code." PNAS 103:
10696-10701.
• Hall Barry G., Adaptive Evolution That Requires Multiple Spontaneous Mutations. I. Mutations Involving an
Insertion Sequence (http://www.genetics.org/cgi/reprint/120/4/887.pdf)

External links
• Nonsense in Schoolbooks - The Imaginary Lamarck (http://www.textbookleague.org/54marck.htm):Michael
T. Ghiselin recounts Lamarck's times and writings.
• Jean-Baptiste Lamarck : works and heritage (http://www.lamarck.cnrs.fr/?lang=en): an English/French web
site edited by Pietro Corsi (Oxford Univ.) and realised by CNRS (France - IT team of CRHST). This web site
contents all books, texts, manuscripts and the lamarck's herbarium.
• Guralnick, Rob, et. al (2006). "Jean-Baptiste Lamarck (1744-1829)" (http://www.ucmp.berkeley.edu/history/
lamarck.html). A History of Evolutionary Thought. University of California Museum of Paleontology. Retrieved
3 July 2010.
• The Sins of the Fathers, Take 2 (http://www.newsweek.com/id/180103/output/print): "At tributes to Darwin,
Lamarckism — inheritance of acquired traits — will be the skunk at the party." By Sharon Begley, Newsweek.
From the magazine issue dated January 26, 2009.
Saltationism 121

Saltationism
In biology, saltation (from Latin, saltus, "leap") is a sudden change from one generation to the next, that is large, or
very large, in comparison with the usual variation of an organism. The term is used for occasionally hypothesized,
nongradual changes (especially single-step speciation) that are atypical of, or violate, standard concepts - gradualism
- involved in neo-Darwinian evolution.
Saltation does not fit into contemporary evolutionary theory, but there are some prominent proponents, including
Carl Woese. Woese, and colleagues, suggested that the absence of RNA signature continuum between domains of
bacteria, archaea, and eukarya constitutes a primary indication that the three primary organismal lineages
materialized via one or more major evolutionary saltations from some universal ancestral state involving dramatic
change in cellular organization that was significant early in the evolution of life, but in complex organisms gave way
to the generally accepted Darwinian mechanisms.[1]
Polyploidy (most common in plants but not unknown in animals) is considered a type of saltation [2] , even though
most polyploid individuals are sterile. Polyploidy meets the basic criteria of saltation in that a significant change (in
gene numbers) results in speciation in just one generation. Mammalian liver cells are typically polyploidal, but they
are not part of the germ line.

Punctuated Equilibrium
It is a popular misconception that punctuated equilibrium is a saltationist theory, often mistaken for Richard
Goldschmidt's hypothesis of "Hopeful Monsters."[3] However, punctuated equilibrium refers instead to a pattern of
evolution where most speciation occurs relatively rapidly from a geological perspective (tens of thousands of years
instead of millions of years), but through neo-Darwinian evolution, not by saltations.

Pop culture
In popular culture, a form of saltation appears to have emerged from misconceptions over currently accepted theories
of evolution (the X-men and its various spin-offs being the most egregious examples). It was also fictionalized in
Greg Bear's novel, Darwin's Radio.
The Teenage Mutant Ninja Turtles ( and many other, similar science-fiction pieces ) are not examples of
saltationism, however. A saltation would be a substantial change that takes place during reproduction; a case when a
child belongs to a different species than its parents - between generations, not during a generation.

See also
• Catastrophism
• Phyletic gradualism
• Rapid modes of evolution
• The Blind Watchmaker
• History of evolutionary thought
• Eclipse of Darwinism
Saltationism 122

Notes and references

[1] Elijah Roberts, Anurag Sethi†, Jonathan Montoya, Carl R. Woese, and Zaida Luthey-Schulten (May 19, 2008). "Molecular signatures of
ribosomal evolution" (http:/ / www. pnas. org/ content/ 105/ 37/ 13953. full?sid=f3651397-00e9-4a57-802b-f41c6ef6cf5a). Proceedings of the
National Academy of Sciences. .
[2] France Dufresne, Paul D. N. Herbert (1994). "Hybridization and origins of polyploidy" (http:/ / www. jstor. org/ pss/ 49988). Proceedings of
the Royal Society. . Retrieved 2010-05-06.
[3] Gould, Stephen Jay. "Punctuated Equilibrium's Threefold History" (http:/ / www. stephenjaygould. org/ library/ gould_structure. html). The
Structure of Evolutionary Theory. Harvard University Press. pp. 1006–1021. . Retrieved 2008-05-05. "[T]he urban legend rests on the false
belief that ... punctuated equilibrium became a saltational theory wedded to Goldschmidt's hopeful monsters as a mechanism. I have labored to
refute this nonsensical charge from the day I first heard it."

Orthogenesis
Orthogenesis, orthogenetic evolution, progressive evolution or autogenesis, is the hypothesis that life has an
innate tendency to move in an unilinear fashion due to some internal or external "driving force". The hypothesis is
based on essentialism and cosmic teleology and proposes an intrinsic drive which slowly transforms species. George
Gaylord Simpson (1953) in an attack on orthogenesis called this mechanism "the mysterious inner force".[1] Classic
proponents of orthogenesis have rejected the theory of natural selection as the organising mechanism in evolution,
and theories of speciation for a rectilinear model of guided evolution acting on discrete species with "essences". The
term orthogenesis was popularised by Theodor Eimer, though many of the ideas are much older (Bateson 1909).[2]

No Goal
Orthogenesis does not postulate a "goal" for evolution. Though it proceeds in a linear fashion driven by some
internal mechanism, it does not have a goal.
Many sources mix this heterodox view of evolution with another—- that evolution is proceeding to some long term
or ultimate goal; the result are definitions that state "orthogenesis proposes that evolution moves in a unilinear
fashion towards a perfect goal". While it is true that early and famous examples of orthogenesis often conflated these
two ideas (e.g. Jean-Baptiste Lamarck's theory of evolution), it is important to recognize that these are in fact two
separate ideas that are rejected by mainstream science; the latter idea of goal-oriented evolution is better understood
as a form of teleology.
The distinction can be seen when we recognize that orthogenesis is inherent in the theories of German biologist Ernst
Haeckel and American paleontologist Richard Swann Lull. Both scientists proposed mechanisms whereby evolution
proceeded in unilinear fashion, but neither saw goals (instead they made pseudo-scientific appeals to unknown
genetic driving processes).
This is important because similar flaws occur recurrently at the fringes of science, typically taking the form of
mysterious molecular drives that supposedly are pushing phenotypic evolution in certain directions or forcing the
formation of new species.

Origins
The orthogenesis hypothesis had a significant following in the 19th century when a number of evolutionary
mechanisms, such as Lamarckism, were being proposed. Jean-Baptiste Lamarck himself accepted the idea, and it had
a central role in his theory of inheritance of acquired characteristics, the hypothesised mechanism of which
resembled the "mysterious inner force" of orthogenesis. Other proponents of orthogenesis included Leo Berg,
philosopher Henri Bergson and, for a time, the paleontologist Henry Fairfield Osborn. Orthogenesis was particularly
accepted by paleontologists who saw in their fossils a directional change, and in invertebrate paleontology thought
there was a gradual and constant directional change. Those who accepted orthogenesis in this way, however, did not
Orthogenesis 123

necessarily accept that the mechanism that drove orthogenesis was teleological. In fact, Darwin himself rarely used
the term "evolution" now so commonly used to describe his theory, because in Darwin's time, evolution usually was
associated with some sort of progressive process like orthogenesis, and this had been common usage since at least
1647.[3]

Comparison of Theories

Comparison of different theories of evolution

Darwinism Orthogenesis Lamarckism

Mechanism Short-sighted Natural Selection sorting Intrinsic drive towards perfection; Intrinsic drive towards perfection and
random genetic variation, no other natural selection unimportant. inheritance of acquired characteristics (both
guidance or aim. Selected traits are Characters produced may be totally are Lamarckian principles); natural selection
adaptive, i.e. have some survival value. non-adaptive, i.e. have no survival adopted by some in latter years.
value.

Common Yes, new species coming into existence No, speciation rejected or considered Depends upon source quoted. Signs that
descent by speciation events. unimportant in long term trends; species shared a common ancestor were
spontaneous generation of new species detected before Darwin, but in absence of a
resulting in parallel evolution. mechanism some still rejected the idea.

Status Prevailing in modified form as modern Refuted by Charles Darwin's Origin of Declined after the Origin, though the
evolutionary synthesis. Species and the modern evolutionary mechanism was not refuted until the modern
synthesis. evolutionary synthesis in which it was
established that the mechanism does not exist.

Collapse of the hypothesis

The orthogenesis hypothesis began to collapse when it became clear that it could not explain the patterns found by
paleontologists in the fossil record, which was non-linear with many complications. The hypothesis was generally
abandoned when no mechanism could be found that would account for the process, and the theory of evolution by
natural selection became the prevailing theory of evolution. The modern evolutionary synthesis, in which the genetic
mechanisms of evolution were discovered, refuted the hypothesis for good. As more was understood about these
mechanisms it became obvious that there was no possible naturalistic way in which the newly discovered mechanism
of heredity could be far-sighted or have a memory of past trends.
The orthogenetic hypothesis, however, died hard. Even Darwin was at first not opposed to orthogenic thinking, as
this quote from the 1911 Encyclopedia Britannica demonstrates:
Darwin and his generation were deeply imbued with the Butlerian tradition, and regarded the organic world as
almost a miracle of adaptation, of the minute dovetailing of structure, function and environment. Darwin
certainly was impressed with the view that natural selection and variation together formed a mechanism, the
central product of which was adaptation. From the Butlerian side, too, came the most urgent opposition to
Darwinism. How is it possible, it was said, that fortuitous variations can furnish the material for the precise
and balanced adaptations that all nature reveals? Selection cannot create the materials on which it is supposed
to operate; the beginnings of new organs, the initial stages of new functions cannot be supposed to have been
useful. Moreover, many naturalists, especially those concerned with palaeontology, pointed to the existence of
orthogenetic series, of long lines of ancestry, which displayed not a sporadic differentiation. in every direction,
but apparently a steady and progressive march in one direction.[4]
Edward Drinker Cope put such a line of argument in the most cogent fashion; the course of evolution,
both in the production of variations and their selection, seemed to him to imply the existence of an
originative, conscious and directive force, for which he invented the term bathmism (Gr. βαθμ, a step or
Orthogenesis 124

beginning). On the other hand, dislike of mystical interpretations of natural facts has driven many
capable naturalists to another extreme and has led them to insist on the all-powerfulness of natural
selection and on the complete indefiniteness of variation. The apparent opposition between the
conflicting schools is more acute than the facts justify.... there is no connection between the appearance
of the variation and the use to which it may be put... in one sense it is a mere coincidence if a particular
variation turn out to be useful. But there are several directions in which the field of variation appears to
be not only limited but defined in a certain direction. Obviously variations depend on the constitution of
the varying organism; a modification, whether it be large or small, is a modification of an already
definite and limited structure.... A continuous environment both from the point of view of production of
variation and selection of variation would appear necessarily to result in a series with the appearance of
orthogenesis. The past history of the organic world displays many successful series and these, as they
have survived, must inevitably display orthogenesis to some extent; but it also displays many failures
which indeed may be regarded as showing that the limitation of variation has been such that the
organisms have lost the possibility of successful response to a new environment.[4]
A few hung on to the orthogenesis hypothesis as late as the 1950s by claiming that the processes of
macroevolution, the long term trends in evolution, were distinct from the processes of microevolution (genetic
variation and natural selection) which were by then well understood and it was known they could not behave
in an orthogenetic manner. Teilhard de Chardin, a Jesuit paleontologist, in The Phenomenon of Man (a book
influential among non-scientists that was published four years after his death in 1959) argued for evolution
aiming for the "Omega Point", while putting man at the center of the universe and accounting for original sin
(Dennett 1995, von Kitzing 1998). The term Chardin used for this was "directed additivity". This form of
orthogenesis has now also been abandoned as more about evolutionary processes has been discovered
(Wilkins 1997). The refutation of orthogenesis had some ramifications in the field of philosophy, as it refuted
the idea of teleology as first postulated by Aristotle and accepted by Immanuel Kant, who had greatly
influenced many scientists. Before the scientific and philosophical revolution that began with Charles Darwin's
ideas, the prevailing philosophy was that the world was teleological and purposeful, and that science was the
study of God's creation. The refutation of these concepts have led to a shift in what science and scientists are
perceived to be.

Modern co-opted usage

Though linear teleological evolution has been refuted, it is not true that evolution never proceeds in a linear way,
reinforcing characteristics, in certain lineages at times, for example, during a period of slow, sustained environmental
change, but such examples are entirely consistent with the modern neo-Darwinian theory of evolution. These
examples have sometimes been referred to as orthogenetic (e.g. by Jacobs et al. 1995 & Woodley 2006) but are not
strictly orthogenetic, and simply appear as linear and constant changes because of environmental and molecular
constraints on the direction of change.
Orthogenesis 125

See also
• Facilitated variation
• Evolution of complexity
• Eclipse of Darwinism
• History of evolutionary thought
• Law of Complexity/Consciousness

References
[1] George Gaylord Simpson, Life of the Past: An Introduction to Paleontology, Yale University Press, New Haven, 1953, p. 125.
[2] The evolutionary future of man: A biological view of progress (http:/ / www. simonyi. ox. ac. uk/ dawkins/ WorldOfDawkins-archive/
Dawkins/ Work/ Articles/ 1993-09-11future. shtml)
[3] Darwin's Dilemma: The Odyssey of Evolution (http:/ / web. archive. org/ web/ 20051216025526/ http:/ / wordorigins. org/ wordore.
htm#evolution), Stephen Jay Gould, an essay in Ever Since Darwin: Reflections in Natural History, W. W. Norton, 1977, ISBN
0-393-06425-5
[4] The Encyclopaedia Britannica: A Dictionary of Arts, Sciences, Literature and General Information, Eleventh Edition, Copyright in all
countries subscribing the Berne Convention by the Chancellor, Masters and Scholars of the University of Cambridge, Copyright in the United
States of America by the Encyclopaedia Britannica Company, London, May 31, 1911.

Sources
1. Bateson, William, 1909. Heredity and variation in modern lights, in Darwin and Modern Science (A.C. Seward
ed.). Cambridge University Press. Chapter V. E-book (http://www.gutenberg.net/etext/1909).
2. Dennett, Daniel, 1995. Darwin's Dangerous Idea. Simon & Schuster.
3. Huxley, Julian, 1942. The Modern Evolutionary Synthesis, London: George Allen and Unwin.
4. Jacobs, Susan C., Allan Larson & James M. Cheverud, 1995. Phylogenetic Relationships and Orthogenetic
Evolution of Coat Color Among Tamarins (Genus Saguinus). Syst. Biol. 44(4):515—532, Abstract (http://
hydrodictyon.eeb.uconn.edu/systbiol/issues/44_4/44_4abstracts.html#Jacobs).
5. Mayr, Ernst, 2002. What Evolution Is, London: Weidenfeld and Nicolson.
6. Simpson, George G., 1957. Life Of The Past: Introduction to Paleontology. Yale University Press, p.119.
7. Wilkins, John, 1997. What is macroevolution?. TalkOrigins Archive (http://www.talkorigins.org/faqs/
macroevolution.html) (14:08 UTC, Oct 13 2004)
8. Woodley, Michael A., 2006. The Limits of Ecology: New Perspectives from a Theoretical Borderland. Abramis
Academic Press.
''On the Origin of Species'' 126

On the Origin of Species

On the Origin of Species

The title page of the 1859 edition

[1]
of On the Origin of Species
Author Charles Darwin

Country United Kingdom

Language English

Subject(s) Natural selection

Evolutionary biology

Genre(s) science, biology

Publisher John Murray

Publication [2]
24 November 1859
date

Media type Print (Hardback)

Pages 502

ISBN N/A

Preceded by On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means
of Selection

Followed by Fertilisation of Orchids

Charles Darwin's On the Origin of Species, published on 24 November 1859, is a work of scientific literature which
is considered to be the foundation of evolutionary biology. Its full title was On the Origin of Species by Means of
Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. For the sixth edition of 1872,
the short title was changed to The Origin of Species. Darwin's book introduced the scientific theory that populations
evolve over the course of generations through a process of natural selection. It presented a body of evidence that the
diversity of life arose by common descent through a branching pattern of evolution. Darwin included evidence that
he had gathered on the Beagle expedition in the 1830s and his subsequent findings from research, correspondence,
and experimentation.
Various evolutionary ideas had already been proposed to explain new findings in biology. There was growing
support for such ideas among dissident anatomists and the general public, but during the first half of the 19th century
the English scientific establishment was closely tied to the Church of England, while science was part of natural
theology. Ideas about the transmutation of species were controversial as they conflicted with the beliefs that species
were unchanging parts of a designed hierarchy and that humans were unique, unrelated to animals. The political and
theological implications were intensely debated, but transmutation was not accepted by the scientific mainstream.
''On the Origin of Species'' 127

The book was written for non-specialist readers and attracted widespread interest upon its publication. As Darwin
was an eminent scientist, his findings were taken seriously and the evidence he presented generated scientific,
philosophical, and religious discussion. The debate over the book contributed to the campaign by T.H. Huxley and
his fellow members of the X Club to secularise science by promoting scientific naturalism. Within two decades there
was widespread scientific agreement that evolution, with a branching pattern of common descent, had occurred, but
scientists were slow to give natural selection the significance that Darwin thought appropriate. During the "eclipse of
Darwinism" from the 1880s to the 1930s, various other mechanisms of evolution were given more credit. With the
development of the modern evolutionary synthesis in the 1930s and 1940s, Darwin's concept of evolutionary
adaptation through natural selection became central to modern evolutionary theory, now the unifying concept of the
life sciences.

Summary of Darwin's theory

Darwin's theory of evolution is based on key facts and the inferences
drawn from them, which biologist Ernst Mayr summarised as
follows:[3]
• Every species is fertile enough that if all offspring survived to
reproduce the population would grow (fact).
• Despite periodic fluctuations, populations remain roughly the same
size (fact).
• Resources such as food are limited and are relatively stable over
time (fact).
• A struggle for survival ensues (inference).
• Individuals in a population vary significantly from one another
(fact).
• Much of this variation is inheritable (fact).
• Individuals less suited to the environment are less likely to survive
and less likely to reproduce; individuals more suited to the
environment are more likely to survive and more likely to reproduce Darwin pictured shortly before publication
and leave their inheritable traits to future generations, which
produces the process of natural selection (inference).
• This slowly effected process results in populations changing to adapt to their environments, and ultimately, these
variations accumulate over time to form new species (inference).

Background

Developments before Darwin's theory

In later editions of the book, Darwin traced evolutionary ideas as far back as Aristotle;[4] the text he cites is a
summary by Aristotle of the ideas of the earlier Greek philosopher Empedocles.[5] Early Christian Church Fathers
and Medieval European scholars interpreted the Genesis creation myth allegorically rather than as a literal historical
account;[6] organisms were described by their mythological and heraldic significance as well as by their physical
form. Nature was widely believed to be unstable and capricious, with monstrous births from union between species,
and spontaneous generation of life.[7]
''On the Origin of Species'' 128

The Protestant Reformation inspired a literal interpretation of the

Bible, with concepts of creation that conflicted with the findings of an
emerging science seeking explanations congruent with the mechanical
philosophy of René Descartes and the empiricism of the Baconian
method. After the turmoil of the English Civil War, the Royal Society
wanted to show that science did not threaten religious and political
stability. John Ray developed an influential natural theology of rational
order; in his taxonomy, species were static and fixed, their adaptation
and complexity designed by God, and varieties showed minor
differences caused by local conditions. In God's benevolent design,
carnivores caused mercifully swift death, but the suffering caused by
parasitism was a puzzling problem. The biological classification
introduced by Carolus Linnaeus in 1735 also viewed species as fixed
according to the divine plan. In 1766, Georges Buffon suggested that
some similar species, such as horses and asses, or lions, tigers, and
leopards, might be varieties descended from a common ancestor. The
Ussher chronology of the 1650s had calculated creation at 4004 BC,
but by the 1780s geologists assumed a much older world. Wernerians
thought strata were deposits from shrinking seas, but James Hutton
proposed a self-maintaining infinite cycle, anticipating
Cuvier's 1799 paper on living and fossil elephants [8]
helped establish the reality of extinction.
uniformitarianism.

Charles Darwin's grandfather Erasmus Darwin outlined a hypothesis of

transmutation of species in the 1790s, and Jean-Baptiste Lamarck published a more developed theory in 1809. Both
envisaged that spontaneous generation produced simple forms of life that progressively developed greater
complexity, adapting to the environment by inheriting changes in adults caused by use or disuse. This process was
later called Lamarckism. Lamarck thought there was an inherent progressive tendency driving organisms
continuously towards greater complexity, in parallel but separate lineages with no extinction.[9] Geoffroy contended
that embryonic development recapitulated transformations of organisms in past eras when the environment acted on
embryos, and that animal structures were determined by a constant plan as demonstrated by homologies. Georges
Cuvier strongly disputed such ideas, holding that unrelated, fixed species showed similarities that reflected a design
for functional needs.[10] His paleontological work in the 1790s had established the reality of extinction, which he
explained by local catastrophes, followed by repopulation of the affected areas by other species.[11]

In Britain, William Paley's Natural Theology saw adaptation as evidence of beneficial "design" by the Creator acting
through natural laws. All naturalists in English universities were Church of England clergymen, and science became
a search for these laws.[12] Geologists adapted catastrophism to show repeated worldwide annihilation and creation
of new fixed species adapted to a changed environment, initially identifying the most recent catastrophe as the
biblical flood.[13] Some anatomists such as Robert Grant were influenced by Lamarck and Geoffroy, but most
naturalists regarded their ideas of transmutation as a threat to divinely appointed social order.[14]

Inception of Darwin's theory

Darwin went to Edinburgh University in 1825 to study medicine. In his second year he neglected his medical studies
for natural history and spent four months assisting Robert Grant's research into marine invertebrates. Grant revealed
his enthusiasm for the transmutation of species, but Darwin rejected it.[15] At Cambridge University starting in 1827,
Darwin learnt science as natural theology from botanist John Stevens Henslow, and read Paley, John Herschel and
Alexander von Humboldt. Filled with zeal for science, he studied catastrophist geology with Adam Sedgwick.[16] [17]
''On the Origin of Species'' 129

In December 1831, he joined the Beagle expedition as a geologist and

naturalist. He read Charles Lyell's Principles of Geology and from the
first stop ashore, at St. Jago, found Lyell's uniformitarianism a key to
the geological history of landscapes. Darwin discovered fossils
resembling huge armadillos, and noted the geographical distribution of
modern species in hope of finding their "centre of creation".[18] The
three Fuegian missionaries the expedition returned to Tierra del Fuego
were friendly and civilised, yet to Darwin their relatives on the island
seemed "miserable, degraded savages",[19] and he no longer saw an
unbridgeable gap between humans and animals.[20] As the Beagle
neared England in 1836, he noted that species might not be fixed.[21]

Richard Owen showed that fossils of extinct species Darwin found in

South America were allied to living species on the same continent. In
March 1837, ornithologist John Gould announced that Darwin's Rhea
was a separate species from the previously described rhea (though their
territories overlapped), that mockingbirds collected on the Galápagos
Islands represented three separate species each unique to a particular
island, and that several distinct birds from those islands were all
classified as finches.[22] Darwin began speculating, in a series of In mid-July 1837 Darwin started his "B"
notebooks, on the possibility that "one species does change into notebook on Transmutation of Species, and on
another" to explain these findings, and around July sketched a page 36 wrote "I think" above his first
evolutionary tree.
genealogical branching of a single evolutionary tree, discarding
Lamarck's independent lineages progressing to higher forms.[23]
Unconventionally, Darwin asked questions of fancy pigeon and animal breeders as well as established scientists. At
the zoo he had his first sight of an ape, and was profoundly impressed by how human the orangutan seemed.[24]

In late September 1838, he started reading Thomas Malthus's An Essay on the Principle of Population with its
statistical proof that human populations breed beyond their means and struggle to survive. Darwin related this to the
struggle for existence among wildlife and botanist de Candolle's "warring of the species" in plants; he immediately
envisioned "a force like a hundred thousand wedges" pushing well-adapted variations into "gaps in the economy of
nature", so that the survivors would pass on their form and abilities, and unfavourable variations would be
destroyed.[25] [26] By December 1838, he had noted a similarity between the act of breeders selecting traits and a
Malthusian Nature selecting among variants thrown up by "chance" so that "every part of newly acquired structure is
fully practical and perfected".[27]
Darwin now had the framework of his theory of natural selection "by which to work",[28] but he was fully occupied
with his career as a geologist and held off writing a sketch of his theory until his book on The Structure and
Distribution of Coral Reefs was completed in May 1842.[29] [30]

Further development
Darwin continued to research and extensively revise his theory while focusing on his main work of publishing the
scientific results of the Beagle voyage.[29] He tentatively wrote of his ideas to Lyell in January 1842;[31] then in June
he roughed out a 35-page "Pencil Sketch" of his theory.[32] Darwin began correspondence about his theorising with
the botanist Joseph Dalton Hooker in January 1844, and by July had rounded out his "sketch" into a 230-page
"Essay", to be expanded with his research results and published if he died prematurely.[33]
''On the Origin of Species'' 130

In November 1844, the anonymously published popular science book

Vestiges of the Natural History of Creation, written by Scottish
journalist Robert Chambers, widened public interest in the concept of
transmutation of species. Vestiges used evidence from the fossil record
and embryology to support the claim that living things had progressed
from the simple to the more complex over time. But it proposed a
linear progression rather than the branching common descent theory
behind Darwin's work in progress, and it ignored adaptation. Darwin
read it soon after publication, and scorned its amateurish geology and
zoology,[34] but he carefully reviewed his own arguments after leading
Darwin researched how the skulls of different scientists, including Adam Sedgwick, attacked its morality and
pigeon breeds varied, as shown in his Variation scientific errors.[35] Vestiges had significant influence on public
of Plants and Animals Under Domestication of
opinion, and the intense debate helped to pave the way for the
1868.
acceptance of the more scientifically sophisticated Origin by moving
evolutionary speculation into the mainstream. While few naturalists
were willing to consider transmutation, Herbert Spencer became an active proponent of Lamarckism and progressive
development in the 1850s.[36]

Hooker was persuaded to take away a copy of the "Essay" in January 1847, and eventually sent a page of notes
giving Darwin much needed feedback. Reminded of his lack of expertise in taxonomy, Darwin began an eight year
study of barnacles, becoming the leading expert on their classification. Using his theory, he discovered homologies
showing that slightly changed body parts served different functions to meet new conditions, and he found an
intermediate stage in the evolution of distinct sexes.[37]
Darwin's barnacle studies convinced him that variation arose constantly and not just in response to changed
circumstances. In 1854, he completed the last part of his Beagle-related writing and began working full-time on
evolution. His thinking changed from the view that species formed in isolated populations only, as on islands, to an
emphasis on speciation without isolation; that is, he saw increasing specialisation within large stable populations as
continuously exploiting new ecological niches. He conducted empirical research focusing on difficulties with his
theory. He studied the developmental and anatomical differences between different breeds of many domestic
animals, became actively involved in fancy pigeon breeding, and experimented (with the help of his son Francis) on
ways that plant seeds and animals might disperse across oceans to colonise distant islands. By 1856, his theory was
much more sophisticated, with a mass of supporting evidence.[37] [38]
''On the Origin of Species'' 131

Publication

Events leading to publication

An 1855 paper on the "introduction" of species, written by Alfred Russel
Wallace, claimed that patterns in the geographical distribution of species and
fossils could be explained if every new species always came into existence near
an already existing, closely related species.[39] Charles Lyell recognised the
implications of Wallace's paper and its possible connection to Darwin's work,
although Darwin did not, and in the spring of 1856 Lyell urged Darwin to
publish his theory to establish priority. Darwin was torn between the desire to set
out a full and convincing account and the pressure to quickly produce a short
paper. He decided he did not want to expose his ideas to review by an editor as
would have been required to publish in an academic journal. On 14 May 1856, he
began a "sketch" account, and by July had decided to produce a full technical
treatise on species.[40]

Darwin was hard at work on his "big book" on Natural Selection, when on
18 June 1858 he received a parcel from Wallace, who was working in Borneo. It
enclosed twenty pages describing an evolutionary mechanism, a response to
Darwin's recent encouragement, with a request to send it on to Lyell if Darwin
A photograph of Alfred Russel
thought it worthwhile. The mechanism was similar to Darwin's own theory.[40] Wallace (1823–1913) taken in
Darwin wrote to Lyell that "your words have come true with a vengeance, ... Singapore in 1862
forestalled" and he would "of course, at once write and offer to send [it] to any
journal" that Wallace chose, adding that "all my originality, whatever it may amount to, will be smashed".[41] Lyell
and Hooker agreed that a joint paper should be presented at the Linnean Society, and on 1 July 1858, the papers
entitled On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural
Means of Selection, by Wallace and Darwin respectively, were read out but drew little reaction. While Darwin
considered Wallace's idea to be identical to his concept of natural selection, historians have pointed out differences.
Darwin described natural selection as being analogous to the artificial selection practised by animal breeders, and
emphasised competition between individuals; Wallace drew no comparison to selective breeding, and focused on
ecological pressures that kept different varieties adapted to local conditions.[42] [43] [44]

After the meeting, Darwin decided to write "an abstract of my whole work".[45] He started work on 20 July 1858,
while on holiday at Sandown,[46] and wrote parts of it from memory.[47] Lyell discussed arrangements with publisher
John Murray III, of the publishing house John Murray,[48] who responded immediately to Darwin's letter of 31
March 1859[49] with an agreement to publish the book without even seeing the manuscript, and an offer to Darwin of
2
⁄3 of the profits.[50] (eventually Murray paid £180 to Darwin for the 1st edition and by Darwin's death in 1882 the
book was in its 6th edition, earning Darwin nearly £3000.[51] ) Darwin had initially decided to call it An abstract of
an Essay on the Origin of Species and Varieties Through natural selection, but with Murray's persuasion it was
eventually changed to the snappier title: On the Origin of Species, with the title page adding by Means of Natural
Selection, or the Preservation of Favoured Races in the Struggle for Life.[2] Here the term "races" is used as an
alternative for "varieties" and does not carry the modern connotation of human races—the first use in the book refers
to "the several races, for instance, of the cabbage" and proceeds to a discussion of "the hereditary varieties or races of
our domestic animals and plants".[52]
''On the Origin of Species'' 132

Time taken to publish

Darwin had his basic theory of natural selection "by which to work" by December 1838, yet almost twenty years
later, when Wallace's letter arrived on 18 June 1858, Darwin was still not ready to publish his theory. It was long
thought that Darwin avoided or delayed making his ideas public for personal reasons. Reasons suggested have
included fear of religious persecution or social disgrace if his views were revealed, and concern about upsetting his
clergymen naturalist friends or his pious wife Emma. Charles Darwin's illness caused repeated delays. His paper on
Glen Roy had proved embarrassingly wrong, and he may have wanted to be sure he was correct. David Quammen
has suggested all these factors may have contributed, and notes Darwin's large output of books and busy family life
during that time.[53]
A more recent study by science historian John van Wyhe has determined that the idea that Darwin delayed
publication only dates back to the 1940s, and Darwin's contemporaries thought the time he took was reasonable.
Darwin always finished one book before starting another. While he was researching, he told many people about his
interest in transmutation without causing outrage. He firmly intended to publish, but it was not until September 1854
that he could work on it full time. His estimate that writing his "big book" would take five years was optimistic.[54]

Publication and subsequent editions

On the Origin of Species was first published on Thursday 24 November 1859, priced at fifteen shillings. The book
had been offered to booksellers at Murray's autumn sale on Tuesday 22 November, and all available copies had been
taken up immediately. In total, 1,250 copies were printed but after deducting presentation and review copies, and
five for Stationers' Hall copyright, around 1,170 copies were available for sale.[2] The second edition of 3,000 copies
was quickly brought out on 7 January 1860,[55] and incorporated numerous corrections as well as a response to
religious objections by the addition of a new epigraph on page ii, a quotation from Charles Kingsley, and the phrase
"by the Creator" amended to the closing sentence.[56] During Darwin's lifetime the book went through six editions,
with cumulative changes and revisions to deal with counter-arguments raised. The third edition came out in 1861,
with a number of sentences rewritten or added and an introductory appendix, An Historical Sketch of the Recent
Progress of Opinion on the Origin of Species,[57] while the fourth in 1866 had further revisions. The fifth edition,
published on 10 February 1869, incorporated more changes and for the first time included the phrase "survival of the
fittest", which had been coined by the philosopher Herbert Spencer in his Principles of Biology (1864).[58]
In January 1871, George Jackson Mivart's On the Genesis of Species listed detailed arguments against natural
selection, and claimed it included false metaphysics.[59] Darwin made revisions to the sixth edition of the Origin,
using the word "evolution" for the first time,[60] and added a new chapter VII, Miscellaneous objections, to address
Mivart's arguments.[61] The sixth edition was published by Murray on 19 February 1872 with "On" dropped from the
title. Darwin had told Murray of working men in Lancashire clubbing together to buy the 5th edition at fifteen
shillings and wanted it made more widely available; the price was halved to 7s 6d by printing in a smaller font. It
includes a glossary compiled by W.S. Dallas. Book sales increased from 60 to 250 per month.[61]
''On the Origin of Species'' 133

Publication outside Great Britain

In the United States, Asa Gray negotiated with a Boston publisher for
publication of an authorised American version, but learnt that two New
York publishing firms were already planning to exploit the absence of
international copyright to print Origin.[62] Darwin was delighted by the
popularity of the book, and asked Gray to keep any profits.[63] Gray
managed to negotiate a 5% royalty with Appleton's of New York,[64]
who got their edition out in mid January 1860, and the other two
withdrew. In a May letter, Darwin mentioned a print run of 2,500
copies, but it is not clear if this referred to the first printing only as
there were four that year.[2] [65]

The book was widely translated in Darwin's life time, but problems
arose with translating concepts and metaphors, and some translations
American botanist Asa Gray (1810–1888) were biased by the translator's own agenda.[66] Darwin distributed
presentation copies in France and Germany, hoping that suitable
applicants would come forward, as translators were expected to make their own arrangements with a local publisher.
He welcomed the distinguished elderly naturalist and geologist Heinrich Georg Bronn, but the German translation
published in 1860 imposed Bronn's own ideas, adding controversial themes that Darwin had deliberately omitted.
Bronn translated "favoured races" as "perfected races", and added essays on issues including the origin of life, as
well as a final chapter on religious implications partly inspired by Bronn's adherence to Naturphilosophie.[67] In
1862, Bronn produced a second edition based on the third English edition and Darwin's suggested additions, but then
died of a heart attack.[68] Darwin corresponded closely with Julius Victor Carus, who published an improved
translation in 1867.[69] Darwin's attempts to find a translator in France fell through, and the translation by Clémence
Royer published in 1862 added an introduction praising Darwin's ideas as an alternative to religious revelation and
promoting ideas anticipating social Darwinism and eugenics, as well as numerous explanatory notes giving her own
answers to doubts that Darwin expressed. Darwin corresponded with Royer about a second edition published in 1866
and a third in 1870, but he had difficulty getting her to remove her notes and was troubled by these editions.[68] [70]
He remained unsatisfied until a translation by Edmond Barbier was published in 1876.[2] A Dutch translation was
published in 1860.[71] By 1864, additional translations had appeared in Italian and Russian.[66] In Darwin's lifetime,
Origin was published in Swedish in 1869, Danish in 1872, Polish in 1873, Hungarian in 1873–1874, Spanish in 1877
and Serbian in 1878. By 1977, it had appeared in an additional 18 languages.[72]
''On the Origin of Species'' 134

Content

Title pages and introduction

Page ii contains quotations by William Whewell and Francis Bacon on
the theology of natural laws,[73] harmonising science and religion in
accordance with Isaac Newton's belief in a rational God who
established a law-abiding cosmos.[74] In the second edition, Darwin
added an epigraph from Joseph Butler affirming that God could work
through scientific laws as much as through miracles, in a nod to the
religious concerns of his oldest friends.[56] The Introduction establishes
Darwin's credentials as a naturalist and author,[75] then refers to John
Herschel's letter suggesting that the origin of species "would be found
to be a natural in contradistinction to a miraculous process":[76]

WHEN on board H.M.S. 'Beagle,' as naturalist, I was

much struck with certain facts in the distribution of the
inhabitants of South America, and in the geological
relations of the present to the past inhabitants of that
continent. These facts seemed to me to throw some light John Gould's illustration of Darwin's Rhea was
published in 1841. The existence of two rhea
on the origin of species—that mystery of mysteries, as it
species with overlapping ranges influenced
has been called by one of our greatest philosophers.[77] Darwin.

Darwin refers specifically to the distribution of the species rheas, and

to that of the Galápagos tortoises and mockingbirds. He mentions his years of work on his theory, and the arrival of
Wallace at the same conclusion, which led him to "publish this Abstract" of his incomplete work. He outlines his
ideas, and sets out the essence of his theory:
As many more individuals of each species are born than can possibly survive; and as, consequently,
there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly
in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have
a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any
selected variety will tend to propagate its new and modified form.[78]
Starting with the third edition, Darwin prefaced the introduction with a historical sketch that traced the development
of evolutionary ideas.[79] In that sketch he acknowledged that Patrick Matthew had, unknown to Wallace or himself,
anticipated the concept of natural selection in an appendix to a book published in 1831;[80] in the fourth edition he
mentioned that William Charles Wells had done so as early as 1813.[81]

Variation under domestication and under nature

Chapter I covers animal husbandry and plant breeding, going back to ancient Egypt. Darwin discusses contemporary
opinions on the origins of different breeds under cultivation to argue that many have been produced from common
ancestors by selective breeding.[82] As an illustration of artificial selection, he describes fancy pigeon breeding,[83]
noting that "[t]he diversity of the breeds is something astonishing", yet all were descended from one species of rock
pigeon.[84] Darwin saw two distinct kinds of variation: (1) rare abrupt changes he called "sports" or "monstrosities"
(example: ancon sheep with short legs), and (2) ubiquitous small differences (example: slightly shorter or longer bill
of pigeons).[85] Both types of hereditary changes can be used by breeders. However, for Darwin the small changes
were most important in evolution.
In Chapter II, Darwin specifies that the distinction between species and varieties is arbitrary, with experts
disagreeing and changing their decisions when new forms were found. He concludes that "a well-marked variety
''On the Origin of Species'' 135

may be justly called an incipient species" and that "species are only strongly marked and permanent varieties".[86] He
argues for the ubiquity of variation in nature.[87] Historians have noted that naturalists had long been aware that the
individuals of a species differed from one another, but had generally considered such variations to be limited and
unimportant deviations from the archetype of each species, that archetype being a fixed ideal in the mind of God.
Darwin and Wallace made variation among individuals of the same species central to understanding the natural
world.[83]

Struggle for existence, natural selection, and divergence

In Chapter III, Darwin asks how varieties "which I have called incipient species" become distinct species, and in
answer introduces the key concept he calls "natural selection";[88] in the fifth edition he adds, "But the expression
often used by Mr. Herbert Spencer, of the Survival of the Fittest, is more accurate, and is sometimes equally
convenient."[89]
Owing to this struggle for life, any variation, however slight and from whatever cause proceeding, if it
be in any degree profitable to an individual of any species, in its infinitely complex relations to other
organic beings and to external nature, will tend to the preservation of that individual, and will generally
be inherited by its offspring ... I have called this principle, by which each slight variation, if useful, is
preserved, by the term of Natural Selection, in order to mark its relation to man's power of selection.[88]
He notes that both A. P. de Candolle and Charles Lyell had stated that all organisms are exposed to severe
competition. Darwin emphasises that he used the phrase "struggle for existence" in "a large and metaphorical sense,
including dependence of one being on another"; he gives examples ranging from plants struggling against drought to
plants competing for birds to eat their fruit and disseminate their seeds. He describes the struggle resulting from
population growth: "It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable
kingdoms." He discusses checks to such increase including complex ecological interdependencies, and notes that
competition is most severe between closely related forms "which fill nearly the same place in the economy of
nature".[90]
Chapter IV details natural selection under the "infinitely complex and close-fitting ... mutual relations of all organic
beings to each other and to their physical conditions of life".[91] Darwin takes as an example a country where a
change in conditions led to extinction of some species, immigration of others and, where suitable variations
occurred, descendants of some species became adapted to new conditions. He remarks that the artificial selection
practised by animal breeders frequently produced sharp divergence in character between breeds, and suggests that
natural selection might do the same, saying:
But how, it may be asked, can any analogous principle apply in nature? I believe it can and does apply
most efficiently, from the simple circumstance that the more diversified the descendants from any one
species become in structure, constitution, and habits, by so much will they be better enabled to seize on
many and widely diversified places in the polity of nature, and so be enabled to increase in numbers.[92]
Historians have remarked that here Darwin anticipated the modern concept of an ecological niche.[93] He did not
suggest that every favourable variation must be selected, nor that the favoured animals were better or higher, but
merely more adapted to their surroundings.
''On the Origin of Species'' 136

Darwin proposes sexual selection,

driven by competition between males
for mates, to explain sexually
dimorphic features such as lion manes,
deer antlers, peacock tails, bird songs,
and the bright plumage of some male
birds.[94] He analysed sexual selection
more fully in The Descent of Man, and
Selection in Relation to Sex (1871).
Natural selection was expected to work
very slowly in forming new species,
but given the effectiveness of artificial
selection, he could "see no limit to the
amount of change, to the beauty and
infinite complexity of the
This tree diagram, used to show the divergence of species, is the only illustration in the
coadaptations between all organic Origin of Species.
beings, one with another and with their
physical conditions of life, which may be effected in the long course of time by nature's power of selection". Using a
tree diagram and calculations, he indicates the "divergence of character" from original species into new species and
genera. He describes branches falling off as extinction occurred, while new branches formed in "the great Tree of
life ... with its ever branching and beautiful ramifications".[95]

Variation and heredity

In Darwin's time there was no agreed-upon model of heredity;[96] in Chapter I Darwin admitted, "The laws
governing inheritance are quite unknown."[97] He accepted a version of the inheritance of acquired characteristics
(which after Darwin's death came to be called Lamarckism), and Chapter V discusses what he called the effects of
use and disuse; he wrote that he thought "there can be little doubt that use in our domestic animals strengthens and
enlarges certain parts, and disuse diminishes them; and that such modifications are inherited", and that this also
applied in nature.[98] Darwin stated that some changes that were commonly attributed to use and disuse, such as the
loss of functional wings in some island dwelling insects, might be produced by natural selection. In later additions of
Origin, Darwin expanded the role attributed to the inheritance of acquired characteristics. Darwin also admitted
ignorance of the source of inheritable variations, but speculated they might be produced by environmental factors.[99]
[100]
However, one thing was clear: whatever the exact nature and causes of new variations, Darwin knew from
observation and experiment that breeders were able to select such variations and produce huge differences in many
generations of selection.[85] The observation that selection works in domestic animals is not destroyed by lack of
understanding of the underlying hereditary mechanism.
Breeding of animals and plants showed related varieties varying in similar ways, or tending to revert to an ancestral
form, and similar patterns of variation in distinct species were explained by Darwin as demonstrating common
descent. He recounted how Lord Morton's mare apparently demonstrated telegony, offspring inheriting
characteristics of a previous mate of the female parent, and accepted this process as increasing the variation available
for natural selection.[101]
More detail was given in Darwin's 1868 book on The Variation of Animals and Plants under Domestication, which
tried to explain heredity through his hypothesis of pangenesis. Although Darwin had privately questioned blending
inheritance, he struggled with the theoretical difficulty that novel individual variations would tend to blend into a
populationa. However, inherited variation could be seen,[102] and Darwin's concept of selection working on a
population with a range of small variations was workable.[103] It was not until the modern evolutionary synthesis in
''On the Origin of Species'' 137

the 1930s and 1940s that a model of heredity became completely integrated with a model of variation.[104]

Difficulties for the theory

Chapter VI begins by saying the next three chapters will address possible objections to the theory, the first being that
often no intermediate forms between closely related species are found, though the theory implies such forms must
have existed. Darwin attributed this to the competition between different forms, combined with the small number of
individuals of intermediate forms, often leading to extinction of such forms.[105] The rest of the chapter deals with
whether natural selection could produce complex specialised structures, and the behaviours to use them, when it
would be difficult to imagine how intermediate forms could be functional. Darwin said:
Secondly, is it possible that an animal having, for instance, the structure and habits of a bat, could have
been formed by the modification of some animal with wholly different habits? Can we believe that
natural selection could produce, on the one hand, organs of trifling importance, such as the tail of a
giraffe, which serves as a fly-flapper, and, on the other hand, organs of such wonderful structure, as the
eye, of which we hardly as yet fully understand the inimitable perfection?[106]
His answer was that in many cases animals exist with intermediate structures that are functional. He presented flying
squirrels, and flying lemurs as examples of how bats might have evolved from non-flying ancestors.[107] He
discussed various simple eyes found in invertebrates, starting with nothing more than an optic nerve coated with
pigment, as examples of how the vertebrate eye could have evolved. Darwin concludes: "If it could be demonstrated
that any complex organ existed, which could not possibly have been formed by numerous, successive, slight
modifications, my theory would absolutely break down. But I can find out no such case."[108]
Chapter VII (of the first edition) addresses the evolution of instincts. His examples included two he had investigated
experimentally: slave-making ants and the construction of hexagonal cells by honey bees. Darwin noted that some
species of slave-making ants were more dependent on slaves than others, and he observed that many ant species will
collect and store the pupae of other species as food. He thought it reasonable that species with an extreme
dependency on slave workers had evolved in incremental steps. He suggested that bees that make hexagonal cells
evolved in steps from bees that made round cells, under pressure from natural selection to economise wax. Darwin
concluded:
Finally, it may not be a logical deduction, but to my imagination it is far more satisfactory to look at
such instincts as the young cuckoo ejecting its foster-brothers, —ants making slaves, —the larvæ of
ichneumonidæ feeding within the live bodies of caterpillars, —not as specially endowed or created
instincts, but as small consequences of one general law, leading to the advancement of all organic
beings, namely, multiply, vary, let the strongest live and the weakest die.[109]
Chapter VIII addresses the idea that species had special characteristics that prevented hybrids from being fertile in
order to preserve separately created species. Darwin said that, far from being constant, the difficulty in producing
hybrids of related species, and the viability and fertility of the hybrids, varied greatly, especially among plants.
Sometimes what were widely considered to be separate species produced fertile hybrid offspring freely, and in other
cases what were considered to be mere varieties of the same species could only be crossed with difficulty. Darwin
concluded: "Finally, then, the facts briefly given in this chapter do not seem to me opposed to, but even rather to
support the view, that there is no fundamental distinction between species and varieties."[110]
In the sixth edition Darwin inserted a new chapter VII (renumbering the subsequent chapters) to respond to
criticisms of earlier editions, including the objection that many features of organisms were not adaptive and could
not have been produced by natural selection. He said some such features could have been by-products of adaptive
changes to other features, and that often features seemed non-adaptive because their function was unknown, as
shown by his book on Fertilisation of Orchids that explained how their elaborate structures facilitated pollination by
insects. Much of the chapter responds to George Jackson Mivart's criticisms, including his claim that features such as
baleen filters in whales, flatfish with both eyes on one side and the camouflage of stick insects could not have
''On the Origin of Species'' 138

evolved through natural selection because intermediate stages would not have been adaptive. Darwin proposed
scenarios for the incremental evolution of each feature.[111]

Geologic record
Chapter IX deals with the fact that the geologic record appears to show forms of life suddenly arising, without the
innumerable transitional fossils expected from gradual changes. Darwin borrowed Charles Lyell's argument in
Principles of Geology that the record is extremely imperfect as fossilisation is a very rare occurrence, spread over
vast periods of time; since few areas had been geologically explored, there could only be fragmentary knowledge of
geological formations, and fossil collections were very poor. Evolved local varieties which migrated into a wider
area would seem to be the sudden appearance of a new species. Darwin did not expect to be able to reconstruct
evolutionary history, but continuing discoveries gave him well founded hope that new finds would occasionally
reveal transitional forms.[112] [113] To show that there had been enough time for natural selection to work slowly, he
again cited Principles of Geology and other observations based on sedimentation and erosion, including an estimate
that erosion of The Weald had taken 300 million years.[114] The initial appearance of entire groups of well developed
organisms in the oldest fossil-bearing layers, now known as the Cambrian explosion, posed a problem. Darwin had
no doubt that earlier seas had swarmed with living creatures, but stated that he had no satisfactory explanation for the
lack of fossils.[115] Fossil evidence of pre-Cambrian life has since been found, extending the history of life back for
billions of years.[116]
Chapter X examines whether patterns in the fossil record are better explained by common descent and branching
evolution through natural selection than by the individual creation of fixed species. Darwin expected species to
change slowly, but not at the same rate – some organisms such as Lingula were unchanged since the earliest fossils.
The pace of natural selection would depend on variability and change in the environment.[117] This distanced his
theory from Lamarckian laws of inevitable progress.[112] It has been argued that this anticipated the punctuated
equilibrium hypothesis,[113] [118] but other scholars have preferred to emphasise Darwin's commitment to
gradualism.[119] He cited Richard Owen's findings that the earliest members of a class were a few simple and
generalised species with characteristics intermediate between modern forms, and were followed by increasingly
diverse and specialised forms, matching the branching of common descent from an ancestor.[112] Patterns of
extinction matched his theory, with related groups of species having a continued existence until extinction, then not
reappearing. Recently extinct species were more similar to living species than those from earlier eras, and as he had
seen in South America, and William Clift had shown in Australia, fossils from recent geological periods resembled
species still living in the same area.[117]

Geographic distribution
Chapter XI deals with evidence from biogeography, starting with the observation that differences in flora and fauna
from separate regions cannot be explained by environmental differences alone; South America, Africa, and Australia
all have regions with similar climates at similar latitudes, but those regions have very different plants and animals.
The species found in one area of a continent are more closely allied with species found in other regions of that same
continent than to species found on other continents. Darwin noted that barriers to migration played an important role
in the differences between the species of different regions. The coastal sea life of the Atlantic and Pacific sides of
Central America had almost no species in common even though the Isthmus of Panama was only a few miles wide.
His explanation was a combination of migration and descent with modification. He went on to say: "On this principle
of inheritance with modification, we can understand how it is that sections of genera, whole genera, and even
families are confined to the same areas, as is so commonly and notoriously the case."[120] Darwin explained how a
volcanic island formed a few hundred miles from a continent might be colonised by a few species from that
continent. These species would become modified over time, but would still be related to species found on the
continent, and Darwin observed that this was a common pattern. Darwin discussed ways that species could be
dispersed across oceans to colonise islands, many of which he had investigated experimentally.[121]
''On the Origin of Species'' 139

Chapter XII continues the discussion of biogeography. After a brief discussion of freshwater species, it returns to
oceanic islands and their peculiarities; for example on some islands roles played by mammals on continents were
played by other animals such as flightless birds or reptiles. The summary of both chapters says:
... I think all the grand leading facts of geographical distribution are explicable on the theory of
migration (generally of the more dominant forms of life), together with subsequent modification and the
multiplication of new forms. We can thus understand the high importance of barriers, whether of land or
water, which separate our several zoological and botanical provinces. We can thus understand the
localisation of sub-genera, genera, and families; and how it is that under different latitudes, for instance
in South America, the inhabitants of the plains and mountains, of the forests, marshes, and deserts, are in
so mysterious a manner linked together by affinity, and are likewise linked to the extinct beings which
formerly inhabited the same continent ... On these same principles, we can understand, as I have
endeavoured to show, why oceanic islands should have few inhabitants, but of these a great number
should be endemic or peculiar; ...[122]

Classification, morphology, embryology, rudimentary organs

Chapter XIII starts by observing that classification depends on species being grouped together in a multilevel system
of groups and sub groups based on varying degrees of resemblance. After discussing classification issues, Darwin
concludes:
All the foregoing rules and aids and difficulties in classification are explained, if I do not greatly deceive
myself, on the view that the natural system is founded on descent with modification; that the characters
which naturalists consider as showing true affinity between any two or more species, are those which
have been inherited from a common parent, and, in so far, all true classification is genealogical; that
community of descent is the hidden bond which naturalists have been unconsciously seeking, ...[123]
Darwin discusses morphology, including the importance of homologous structures. He says, "What can be more
curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle
of the porpoise, and the wing of the bat, should all be constructed on the same pattern, and should include the same
bones, in the same relative positions?"[124] He notes that animals of the same class often have extremely similar
embryos. Darwin discusses rudimentary organs, such as the wings of flightless birds and the rudiments of pelvis and
leg bones found in some snakes. He remarks that some rudimentary organs, such as teeth in baleen whales, are found
only in embryonic stages.

Concluding remarks
The final chapter reviews points from earlier chapters, and Darwin concludes by hoping that his theory might
produce revolutionary changes in many fields of natural history. Although he avoids the controversial topic of
human origins in the rest of the book so as not to prejudice readers against his theory, here he ventures a cautious
hint that psychology would be put on a new foundation and that "Light will be thrown on the origin of man".[125]
Darwin ends with a passage that became well known and much quoted:
It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds
singing on the bushes, with various insects flitting about, and with worms crawling through the damp
earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent
on each other in so complex a manner, have all been produced by laws acting around us ... Thus, from
the war of nature, from famine and death, the most exalted object which we are capable of conceiving,
namely, the production of the higher animals, directly follows. There is grandeur in this view of life,
with its several powers, having been originally breathed into a few forms or into one; and that, whilst
this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless
forms most beautiful and most wonderful have been, and are being, evolved.[126]
''On the Origin of Species'' 140

Structure and style

Nature and structure of Darwin's argument

Darwin's aims were twofold: to show that species had not been separately created, and to show that natural selection
had been the chief agent of change.[127] He knew that his readers were already familiar with the concept of
transmutation of species from Vestiges, and his introduction ridicules that work as failing to provide a viable
mechanism.[128] Therefore the first four chapters lay out his case that selection in nature, caused by the struggle for
existence, is analogous to the selection of variations under domestication, and that the accumulation of adaptive
variations provides a scientifically testable mechanism for evolutionary speciation.[129] [130]
Later chapters provide evidence that evolution has occurred, supporting the idea of branching, adaptive evolution
without directly proving that selection is the mechanism. Darwin presents supporting facts drawn from many
disciplines, showing that his theory could explain a myriad of observations from many fields of natural history that
were inexplicable under the alternate concept that species had been individually created.[130] [131] [132] The structure
of Darwin's argument showed the influence of John Herschel, whose philosophy of science maintained that a
mechanism could be called a vera causa (true cause) if three things could be demonstrated: its existence in nature, its
ability to produce the effects of interest, and its ability to explain a wide range of observations.[133]

Literary style
The Examiner review of 3 December 1859 commented, "Much of Mr. Darwin's volume is what ordinary readers
would call 'tough reading;' that is, writing which to comprehend requires concentrated attention and some
preparation for the task. All, however, is by no means of this description, and many parts of the book abound in
information, easy to comprehend and both instructive and entertaining."[128] [134]
While the book was readable enough to sell, its dryness ensured that it was seen as aimed at specialist scientists and
could not be dismissed as mere journalism or imaginative fiction. Unlike the still-popular Vestiges, it avoided the
narrative style of the historical novel and cosmological speculation, though the closing sentence clearly hinted at
cosmic progression. Darwin had long been immersed in the literary forms and practices of specialist science, and
made effective use of his skills in structuring arguments.[128] David Quammen has described the book as written in
everyday language for a wide audience, but noted that Darwin's literary style was uneven: in some places he used
convoluted sentences that are difficult to read; in other places his writing was beautiful. Quammen advised that later
editions were weakened by Darwin making concessions and adding details to address his critics, and recommended
the first edition.[135] James T. Costa said that because the book was an abstract produced in haste in response to
Wallace's essay, it was more approachable than the big book on natural selection Darwin had been working on,
which would have been encumbered by scholarly footnotes and much more technical detail. He added that parts of
Origin are dense, but parts are almost lyrical, and the case studies and observations are presented in a narrative style
unusual in serious scientific books, which broadened its audience.[136]
''On the Origin of Species'' 141

Reception
The book aroused international interest[138] and a widespread debate,
with no sharp line between scientific issues and ideological, social and
religious implications.[139] Much of the initial reaction was hostile, but
Darwin had to be taken seriously as a prominent and respected name in
science. There was much less controversy than had greeted the 1844
publication Vestiges of Creation, which had been rejected by
scientists,[138] but had influenced a wide public readership into
believing that nature and human society were governed by natural
laws.[25] The Origin of Species as a book of wide general interest
became associated with ideas of social reform. Its proponents made full
use of a surge in the publication of review journals, and it was given
more popular attention than almost any other scientific work, though it
failed to match the continuing sales of Vestiges.[140] Darwin's book
legitimised scientific discussion of evolutionary mechanisms, and the
newly coined term Darwinism was used to cover the whole range of
evolutionism, not just his own ideas. By the mid 1870s, evolutionism British cartoonists presented Darwin's theory in
was triumphant.[139] an unthreatening way. In the 1870s iconic
caricatures of Darwin with an ape or monkey
With the exception of a brief hint in the final chapter, Darwin had body emphasised his significance in transforming
ideas, and contributed to widespread
avoided the subject of human evolution. Despite this, the first review
identification of evolutionism with
claimed it made a creed of the "men from monkeys" idea from [137]
Darwinism.
Vestiges.[141] Human evolution became central to the debate and was
strongly argued by Huxley who featured it in his popular "working-men's lectures". Darwin did not publish his own
views on this until 1871.[142] The naturalism of natural selection conflicted with presumptions of purpose in nature
and while this could be reconciled by theistic evolution, other mechanisms implying more progress or purpose were
more acceptable. Herbert Spencer had already incorporated Lamarckism into his popular philosophy of progressive
free market human society. He popularised the terms evolution and survival of the fittest, and many thought Spencer
was central to evolutionary thinking.[143]

Impact on the scientific community

Scientific readers were already aware of arguments that species changed through processes that were subject to laws
of nature, but the transmutational ideas of Lamarck and the vague "law of development" of Vestiges had not found
scientific favour. Darwin presented natural selection as a scientifically testable mechanism while accepting that other
mechanisms such as inheritance of acquired characters were possible. His strategy established that evolution through
natural laws was worthy of scientific study, and by 1875, most scientists accepted that evolution occurred but few
thought natural selection was significant. Darwin's scientific method was also disputed, with his proponents
favouring the empiricism of John Stuart Mill's A System of Logic, while opponents held to the idealist school of
William Whewell's Philosophy of the Inductive Sciences, in which investigation could begin with the intuitive truth
that species were fixed objects created by design.[144] Early support for Darwin's ideas came from the findings of
field naturalists studying biogeography and ecology, including Joseph Dalton Hooker in 1860, and Asa Gray in
1862. Henry Walter Bates presented research in 1861 that explained insect mimicry using natural selection. Alfred
Russel Wallace discussed evidence from his Malay archipelago research, including an 1864 paper with an
evolutionary explanation for the Wallace line.[145]
''On the Origin of Species'' 142

Evolution had less obvious applications to

anatomy and morphology, and at first had
little impact on the research of the anatomist
Thomas Henry Huxley.[147] Despite this,
Huxley strongly supported Darwin on
evolution; though he called for experiments
to show whether natural selection could
form new species, and questioned if
Darwin's gradualism was sufficient without
sudden leaps to cause speciation. Huxley
wanted science to be secular, without
Huxley used illustrations to show that humans and apes had the same basic skeletal
religious interference, and his article in the
[146] April 1860 Westminster Review promoted
structure.
scientific naturalism over natural
theology,[148] [149] praising Darwin for "extending the domination of Science over regions of thought into which she
has, as yet, hardly penetrated" and coining the term "Darwinism" as part of his efforts to secularise and
professionalise science.[150] Huxley gained influence, and initiated the X Club, which used the journal Nature to
promote evolution and naturalism, shaping much of late Victorian science. Later, the German morphologist Ernst
Haeckel would convince Huxley that comparative anatomy and palaeontology could be used to reconstruct
evolutionary genealogies.[147] [151]

The leading naturalist in Britain was the anatomist Richard Owen, an idealist who had shifted to the view in the
1850s that the history of life was the gradual unfolding of a divine plan.[152] Owen's review of the Origin in the April
1860 Edinburgh Review bitterly attacked Huxley, Hooker and Darwin, but also signalled acceptance of a kind of
evolution as a teleological plan in a continuous "ordained becoming", with new species appearing by natural birth.
Others that rejected natural selection, but supported "creation by birth", included the Duke of Argyll who explained
beauty in plumage by design.[153] Since 1858, Huxley had emphasised anatomical similarities between apes and
humans, contesting Owen's view that humans were a separate sub-class. Their disagreement over human origins
came to the fore at the British Association for the Advancement of Science meeting featuring the legendary 1860
Oxford evolution debate.[154] In two years of acrimonious public dispute that Charles Kingsley satirised as the
"Great Hippocampus Question" and parodied in The Water-Babies as the "great hippopotamus test", Huxley showed
that Owen was incorrect in asserting that ape brains lacked a structure present in human brains.[155] Others, including
Charles Lyell and Alfred Russel Wallace, thought that humans shared a common ancestor with apes, but higher
mental faculties could not have evolved through a purely material process. Darwin published his own explanation in
the Descent of Man (1871).[156]
''On the Origin of Species'' 143

Impact outside Great Britain

Evolutionary ideas, although not natural selection, were accepted by

German biologists accustomed to ideas of homology in morphology
from Goethe's Metamorphosis of Plants and from their long tradition
of comparative anatomy. Bronn's alterations in his German translation
added to the misgivings of conservatives, but enthused political
radicals. Ernst Haeckel was particularly ardent, aiming to synthesise
Darwin's ideas with those of Lamarck and Goethe while still reflecting
the spirit of Naturphilosophie.[67] [158] Their ambitious programme to
reconstruct the evolutionary history of life was joined by Huxley and
supported by discoveries in palaeontology. Haeckel used embryology
extensively in his recapitulation theory, which embodied a progressive,
almost linear model of evolution. Darwin was cautious about such
histories, and had already noted that von Baer's laws of embryology
supported his idea of complex branching.[157]

Asa Gray promoted and defended Origin against those American

naturalists with an idealist approach, notably Louis Agassiz who
viewed every species as a distinct fixed unit in the mind of the Creator,
classifying as species what others considered merely varieties. Edward
Drinker Cope and Alpheus Hyatt reconciled this view with
Haeckel showed a main trunk leading to mankind
evolutionism in a form of neo-Lamarckism involving recapitulation
with minor branches to various animals, unlike
theory.[158] Darwin's branching evolutionary tree.
[157]

French speaking naturalists in several countries showed appreciation of

the much modified French translation by Clémence Royer, but Darwin's ideas had little impact in France, where any
scientists supporting evolutionary ideas opted for a form of Lamarckism.[70] The intelligentsia in Russia had
accepted the general phenomenon of evolution for several years before Darwin had published his theory, and
scientists were quick to take it into account, although the Malthusian aspects were felt to be relatively unimportant.
The political economy of struggle was criticised as a British stereotype by Karl Marx and by Leo Tolstoy, who had
the character Levin in his novel Anna Karenina voice sharp criticism of the morality of Darwin's views.[66]

Challenges to natural selection

There were serious scientific objections to the process of natural selection as the key mechanism of evolution,
including Karl von Nägeli's insistence that a trivial characteristic with no adaptive advantage could not be developed
by selection. Darwin conceded that these could be linked to adaptive characteristics. His estimate that the age of the
Earth allowed gradual evolution was disputed by William Thomson (later awarded the title Lord Kelvin), who
calculated that it had cooled in less than 100 million years. Darwin accepted blending inheritance, but Fleeming
Jenkin calculated that as it mixed traits, natural selection could not accumulate useful traits. Darwin tried to meet
these objections in the 5th edition. Mivart supported directed evolution, and compiled scientific and religious
objections to natural selection. In response, Darwin made considerable changes to the sixth edition. The problems of
the age of the Earth and heredity were only resolved in the 20th century.[59] [159]
By the mid 1870s, most scientists accepted evolution, but relegated natural selection to a minor role as they believed
evolution was purposeful and progressive. The range of evolutionary theories during "the eclipse of Darwinism"
included forms of "saltationism" in which new species were thought to arise through "jumps" rather than gradual
adaptation, forms of orthogenesis claiming that species had an inherent tendency to change in a particular direction,
and forms of neo-Lamarckism in which inheritance of acquired characteristics led to progress. The minority view of
August Weismann, that natural selection was the only mechanism, was called neo-Darwinism. It was thought that the
''On the Origin of Species'' 144

rediscovery of Mendelian inheritance invalidated Darwin's views.[160] [161]

Religious attitudes
The book produced a wide range of religious responses at a time of changing ideas and increasing secularisation. The
issues raised were complex and there was a large middle ground. Developments in geology meant that there was
little opposition based on a literal reading of Genesis,[162] but defence of the argument from design and natural
theology was central to debates over the book in the English speaking world.[163] [164]
Natural theology was not a unified doctrine, and while some such as
Louis Agassiz were strongly opposed to the ideas in the book, others
sought a reconciliation in which evolution was seen as purposeful.[162]
In the Church of England, some liberal clergymen interpreted natural
selection as an instrument of God's design, with the cleric Charles
Kingsley seeing it as "just as noble a conception of Deity".[166] [167] In
the second edition of January 1860, Darwin quoted Kingsley as "a
celebrated cleric", and added the phrase "by the Creator" to the closing
sentence, which from then on read "life, with its several powers,
having been originally breathed by the Creator into a few forms or into
one".[168] While some commentators have taken this as a concession to
religion that Darwin later regretted,[56] Darwin's view at the time was
of God creating life through the laws of nature,[169] [170] and even in
the first edition there are several references to "creation".[171]
The liberal theologian Baden Powell defended
Baden Powell praised "Mr Darwin's masterly volume [supporting] the
evolutionary ideas by arguing that the
grand principle of the self-evolving powers of nature".[172] In America,
introduction of new species should be considered
[165]
Asa Gray argued that evolution is the secondary effect, or modus
a natural rather than a miraculous process.
operandi, of the first cause, design,[173] and published a pamphlet
defending the book in terms of theistic evolution, Natural Selection is not inconsistent with Natural Theology.[166]
[174] [175]
Theistic evolution became a popular compromise, and St. George Jackson Mivart was among those
accepting evolution but attacking Darwin's naturalistic mechanism. Eventually it was realised that supernatural
intervention could not be a scientific explanation, and naturalistic mechanisms such as neo-Lamarckism were
favoured over natural selection as being more compatible with purpose.[162]

Even though the book had barely hinted at human evolution, it quickly became central to the debate as mental and
moral qualities were seen as spiritual aspects of the immaterial soul, and it was believed that animals did not have
spiritual qualities. This conflict could be reconciled by supposing there was some supernatural intervention on the
path leading to humans, or viewing evolution as a purposeful and progressive ascent to mankind's position at the
head of nature.[162] While many conservative theologians accepted evolution, Charles Hodge argued in his 1874
critique "What is Darwinism?" that "Darwinism", defined narrowly as including rejection of design, was atheism
though he accepted that Asa Gray did not reject design.[176] [177] Asa Gray responded that this charge misrepresented
Darwin's text.[178] By the early 20th century, four noted authors of The Fundamentals were explicitly open to the
possibility that God created through evolution,[179] but fundamentalism inspired the American creation–evolution
controversy that began in the 1920s. Some conservative Roman Catholic writers and influential Jesuits opposed
evolution in the late 19th and early 20th century, but other Catholic writers, starting with Mivart, pointed out that
early Church Fathers had not interpreted Genesis literally in this area.[180] The Vatican stated its official position in a
1950 papal encyclical, which stated that evolution was not inconsistent with Catholic teaching.[181] [182]
''On the Origin of Species'' 145

Modern influence
Various alternative evolutionary
mechanisms favoured during "the eclipse of
Darwinism" became untenable as more was
learned about inheritance and mutation. The
full significance of natural selection was at
last accepted in the 1930s and 1940s as part
of the modern evolutionary synthesis.
During that synthesis biologists and
statisticians, including R. A. Fisher, Sewall
Wright and J.B.S. Haldane, merged
Darwinian selection with a statistical
understanding of Mendelian genetics.[161]

Modern evolutionary theory continues to A modern phylogenetic tree based on genome analysis shows the three-domain
system.
develop. Darwin's theory of evolution by
natural selection, with its tree like model of
branching common descent, has become the unifying theory of the life sciences. The theory explains the diversity of
living organisms and their adaptation to the environment. It makes sense of the geologic record, biogeography,
parallels in embryonic development, biological homologies, vestigiality, cladistics, phylogenetics and other fields,
with unrivalled explanatory power; it has also become essential to applied sciences such as medicine and
agriculture.[183] [184] Despite the scientific consensus, a religion-based political controversy has developed over how
evolution is taught in schools, especially in the United States.[185]

Interest in Darwin's writings continues, and scholars have generated an extensive literature, the Darwin Industry,
about his life and work. The text of Origin itself has been subject to much analysis including a variorum, detailing
the changes made in every edition, first published in 1959,[186] and a concordance, an exhaustive external index
published in 1981.[187] Worldwide commemorations of the 150th anniversary of the publication of On the Origin of
Species and the bicentenary of Darwin's birth were scheduled for 2009[188] . They celebrate the ideas which "over the
last 150 years have revolutionised our understanding of nature and our place within it".[189]

See also
• Charles Darwin bibliography
• The Complete Works of Charles Darwin Online
• The Descent of Man, and Selection in Relation to Sex, published in 1871 and his second great book on
evolutionary theory.
• Transmutation of species
• Modern evolutionary synthesis
• History of evolutionary thought
• History of biology
''On the Origin of Species'' 146

Notes
[1] Darwin 1859, p.  iii (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=side& itemID=F373& pageseq=8)
[2] Freeman 1977
[3] Mayr 1982, pp. 479–480
[4] Darwin 1872, p.  xiii (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F391& pageseq=18)
[5] Aristotle, Physics (http:/ / classics. mit. edu/ Aristotle/ physics. 2. ii. html), translated by Hardie, R. P. and Gayle, R. K. and hosted by MIT's
Internet Classics Archive, , retrieved 2009-04-23
[6] Forster & Marston 1999, pp. 26–27
[7] Bowler 2003, pp. 27, 43, 45
[8] Bowler 2003, pp. 27–36, 39–42, 57–62, 67, 70, 77–80
[9] Bowler 2003, pp. 84–90
[10] Desmond 1989, pp. 47–54
[11] Bowler 2003, pp. 111–114
[12] Browne 1995, pp. 91, 129
[13] Bowler 2003, pp. 115–117
[14] Desmond & Moore 1991, pp. 34–35
[15] Browne 1995, pp. 80–88
[16] Bowler 2003, pp. 148–149
[17] Browne 1995, pp. 133–140
[18] Larson 2004, pp. 59–62
[19] Darwin 1845, pp.  205–208 (http:/ / darwin-online. org. uk/ content/ frameset?itemID=F14& viewtype=text& pageseq=218)
[20] Browne 1995, pp. 244–250
[21] Keynes 2000, pp.  xix–xx (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F1840& pageseq=22); Eldredge 2006
[22] Quammen 2006, pp. 24–25
[23] Herbert 1980, pp.  7–10 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F1583e& pageseq=9). van Wyhe 2008,
p. 44; Darwin's Notebook B: Transmutation of species. pp. 1–13, 26, 36, 74 (http:/ / darwin-online. org. uk/ content/
frameset?viewtype=side& itemID=CUL-DAR121. -& pageseq=1), , retrieved 2009-03-16
[24] Desmond & Moore 1991, pp. 240–244
[25] van Wyhe 2009
[26] Larson 2004, pp. 66–70; Darwin's Notebook D: Transmutation of species. pp. 134–135 (http:/ / darwin-online. org. uk/ content/
frameset?viewtype=text& itemID=CUL-DAR123. -& pageseq=112), , retrieved 2009-04-08
[27] Darwin's Notebook E: Transmutation of species. p. 75 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text&
itemID=CUL-DAR124. -& pageseq=63), , retrieved 2009-03-14
[28] Darwin 1958, p.  120 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F1497& pageseq=124)
[29] van Wyhe 2007, pp.  186–187 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=A544& pageseq=10)
[30] Browne 1995, p. 436
[31] Desmond & Moore 1991, p. 292
[32] Browne 1995, pp. 436–437
[33] van Wyhe 2007, p. 188
[34] Darwin Correspondence Project – Letter 814—Darwin, C. R. to Hooker, J. D., (7 Jan 1845) (http:/ / www. darwinproject. ac. uk/
darwinletters/ calendar/ entry-814. html#back-mark-814. f5), , retrieved 2008-11-24
[35] Browne 1995, pp. 461–465
[36] Bowler 2003, pp. 135–140
[37] Bowler 2003, pp. 169–173
Darwin 1958, pp.  117–121 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F1497& pageseq=121)
[38] Quammen 2006, pp. 138–142
[39] Wallace, Alfred R. (1855), "On the law which has regulated the introduction of new species" (http:/ / darwin-online. org. uk/ content/
frameset?viewtype=text& itemID=A11& pageseq=1), Annals and Magazine of Natural History, including Zoology, Botany, and Geology 16:
184–196,
[40] Quammen 2006, pp. 135–158
[41] Darwin Correspondence Project – Letter 2285—Darwin to Lyell (June 1858) (http:/ / www. darwinproject. ac. uk/ darwinletters/ calendar/
entry-2285. html), , retrieved 2008-03-15
[42] Larson 2004, pp. 74–75
[43] Quammen 2006, pp. 162–163
[44] Bowler 2003, pp. 175–176
[45] "Letter 2303 — Darwin, C. R. to Hooker, J. D., 5 July (1858)" (http:/ / www. darwinproject. ac. uk/ entry-2303). Darwin Correspondence
Project. . Retrieved 2010-09-07.
[46] Darwin 2006, p.  36 verso (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=side& itemID=CUL-DAR158. 1-76& pageseq=70)
''On the Origin of Species'' 147

[47] "Letter 2432 — Darwin, C. R. to Hooker, J. D., 15 Mar (1859)" (http:/ / www. darwinproject. ac. uk/ entry-2432). Darwin Correspondence
Project. . Retrieved 2010-09-07.
[48] "Letter 2437 — Darwin, C. R. to Lyell, Charles, 28 Mar (1859)" (http:/ / www. darwinproject. ac. uk/ entry-2437). Darwin Correspondence
Project. . Retrieved 2010-09-07.
[49] "Letter 2441 — Darwin, C. R. to Murray, John (b), 31 Mar (1859)" (http:/ / www. darwinproject. ac. uk/ entry-2441). Darwin
Correspondence Project. . Retrieved 2010-09-07.
[50] "Letter 2443 — Murray, John (b) to Darwin, C. R., 1 Apr 1859" (http:/ / www. darwinproject. ac. uk/ entry-2443). Darwin Correspondence
Project. . Retrieved 2010-09-07.
[51] "Charles Darwin and his publisher" (http:/ / www. darwinproject. ac. uk/ charles-darwin-and-john-murray). Darwin Correspondence Project.
2010. . Retrieved 2010-09-07.
[52] Darwin 1859, p.  15 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F373& pageseq=30)
[53] Quammen 2006, pp. 84–92
[54] van Wyhe 2007
[55] Darwin 1958, p.  122 (http:/ / darwin-online. org. uk/ content/ frameset?itemID=F1497& viewtype=text& pageseq=126)
[56] Browne 2002, pp. 95–96
[57] Darwin 1861, p.  xiii (http:/ / darwin-online. org. uk/ content/ frameset?itemID=F381& viewtype=text& pageseq=20)
[58] "This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called 'natural selection',
or the preservation of favoured races in the struggle for life." Spencer 1864, pp.  444–445 (http:/ / books. google. co. uk/
books?id=SRkRAAAAYAAJ& pg=PA444& ci=84,1345,817,57& source=bookclip)
[59] Mivart 1871
[60] Used in the transformist sense by Charles Lyell in 1832, Principles of Geology vol 2, p. 11; and previously by Darwin in The Descent of
Man in 1871.
[61] Desmond & Moore 1991, pp. 577, 582, 590, 592–593; Freeman 1977
[62] Darwin Correspondence Project – Letter 2592—Darwin, C. R. to Gray, Asa, 21 Dec (1859) (http:/ / www. darwinproject. ac. uk/
darwinletters/ calendar/ entry-2592. html#mark-2592. f3), , retrieved 2008-12-06
[63] Darwin Correspondence Project – Letter 2665—Darwin, C. R. to Gray, Asa, 28 Jan (1860) (http:/ / www. darwinproject. ac. uk/
darwinletters/ calendar/ entry-2665. html#back-mark-2665. f9), , retrieved 2008-12-06
[64] Darwin Correspondence Project – Letter 2706—Gray, Asa to Darwin, C. R., 20 Feb 1860 (http:/ / www. darwinproject. ac. uk/
darwinletters/ calendar/ entry-2706. html), , retrieved 2008-12-06
[65] Desmond & Moore 1991, p. 492
[66] Browne 2002, pp. 256–259
[67] Browne 2002, pp. 140–142
[68] Darwin Correspondence Project – The correspondence of Charles Darwin, volume 10: 1862 (http:/ / www. darwinproject. ac. uk/ content/
view/ 28/ 38/ ), , retrieved 2009-03-06
[69] Darwin Correspondence Project – The correspondence of Charles Darwin, volume 14: 1866 (http:/ / www. darwinproject. ac. uk/ content/
view/ 32/ 38/ ), , retrieved 2009-03-06
[70] Browne 2002, pp. 142–144
[71] Ch. Darwin, Het ontstaan der soorten van dieren en planten door middel van de natuurkeus of het bewaard blijven van bevoorregte rassen
in de strijd des levens, transl. by T.C. Winkler (Haarlem 1860) Source: Teyler, Winkler, Darwin (http:/ / api. ning. com/ files/
aT0Fpi7QEAJXZty6RRr0*ayjT5aN-CLIR1HAnom7DRBt*Z64Ko2B*I88LPx*h2otwLvz5Vp*IKVqHQunTD*sItKN3P7MUMve/
TeylerWinklerDarwin. doc) Lecture by Marijn van Hoorn (http:/ / teylersmuseum. ning. com/ profiles/ blogs/ 142-teyler-winkler-darwin) MA
at the Congress of the European Botanical and Horticultural Libraries Group, Prague, 23 April 2009
[72] Freeman 1977, pp.  101–111 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=A1& pageseq=102)
[73] Darwin 1859, p.  ii (http:/ / darwin-online. org. uk/ content/ frameset?itemID=F373& viewtype=side& pageseq=7).
[74] Phipps 1983
[75] Secord 2000, p. 510
[76] van Wyhe 2007, p. 197
[77] Darwin 1859, p.  1 (http:/ / darwin-online. org. uk/ content/ frameset?itemID=F373& viewtype=text& pageseq=16).
[78] Darwin 1859, p.  5 (http:/ / darwin-online. org. uk/ content/ frameset?itemID=F373& viewtype=text& pageseq=20).
[79] Darwin & Costa 2009, p. 1
[80] Darwin 1861, p.  xiii (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F381& pageseq=20).
[81] Darwin 1866, p.  xiv-xv (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F385& pageseq=21).
[82] Darwin & Costa 2009, p. 7
[83] Quammen 2006, pp. 184–186
[84] Darwin 1859, pp.  20–28 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F373& pageseq=35)
[85] David Reznick (2009) The Origin Then and Now, Princeton University Press, p.49.
[86] Darwin 1859, pp.  44–59 Chap. II (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F373& pageseq=59).
[87] Darwin & Costa 2009, p. 44
[88] Darwin 1859, pp.  60–61 Chap. III (http:/ / darwin-online. org. uk/ content/ frameset?itemID=F373& viewtype=text& pageseq=75)
''On the Origin of Species'' 148

[89] Darwin 1869, pp.  72 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F387& pageseq=101)
[90] Darwin 1859, pp.  62–76 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F373& pageseq=77)
[91] Darwin 1859, p.  80 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F373& pageseq=95)
[92] Darwin 1859, p.  112 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F373& pageseq=127)
[93] Quammen 2006, p. 189
[94] Darwin 1859, pp.  87–101 (http:/ / darwin-online. org. uk/ content/ frameset?itemID=F373& viewtype=text& pageseq=102)
[95] Darwin 1859, pp.  117–130 (http:/ / darwin-online. org. uk/ content/ frameset?itemID=F373& viewtype=text& pageseq=133).
[96] Larson 2004, p. 85
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[133] Darwin & Costa 2009, p. xvii
[134] Crawford 1859
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[137] Browne 2002, pp. 376–379
[138] van Wyhe 2008, pp. 48–49
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[140] Browne 2002, pp. 102–103
''On the Origin of Species'' 149

[141] Browne 2002, p. 87

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[154] Lucas 1979
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[185] Darwin & Costa 2009, p. x
[186] Peckham 1959, recently reprinted.
[187] Quammen 2006, pp. 179, 271–283
[188] The ISTC of On the Origin of Species is A02-2009-00000001-4. As a tribute to its influence, this work has been the first one to be
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''On the Origin of Species'' 150

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Further reading
• Janet Browne (2007). Darwin's Origin of Species: A Biography. ISBN 978-0871139535
• David N. Reznick (2009) The Origin Then and Now: An Interpretive Guide to the Origin of Species ISBN
978-0-691-12978-5.

Contemporary reviews
• Carpenter, William Benjamin (1859), "Darwin on the Origin of Species" (http://darwin-online.org.uk/content/
frameset?itemID=A17&viewtype=text&pageseq=1), National Review 10 (December 1859): 188–214. Published
anonymously.
''On the Origin of Species'' 153

• Gray, Asa (1860), "(Review of) The Origin of Species" (http://darwin-online.org.uk/content/

frameset?itemID=A213&viewtype=text&pageseq=1), Athenaeum (1710: 4 August 1860): 161. Extract from
Proceedings of the American Academy of Arts and Sciences 4 (1860): 411–415.
• Huxley, Thomas Henry (1859), "Time and Life: Mr Darwin's "Origin of Species"" (http://darwin-online.org.uk/
content/frameset?itemID=A43&viewtype=image&pageseq=1), Macmillan's Magazine 1: 142–148.
• Huxley, Thomas Henry (1859), "Darwin on the Origin of Species" (http://darwin-online.org.uk/content/
frameset?itemID=A166&viewtype=text&pageseq=1), The Times (26 December 1859): 8–9. Published
anonymously.
• Jenkin, Fleeming (1867), "(Review of) The Origin of Species" (http://darwin-online.org.uk/content/
frameset?itemID=A24&viewtype=text&pageseq=1), North British Review 46 (June 1867): 277–318. Published
anonymously.
• Murray, Andrew (1860), "On Mr Darwin's Theory of the Origin of Species" (http://darwin-online.org.uk/
content/frameset?itemID=A14&viewtype=text&pageseq=1), Proceedings of the Royal Society of Edinburgh 4:
274–291.
• Owen, Richard (1860), "Review of Darwin's Origin of Species" (http://darwin-online.org.uk/content/
frameset?itemID=A30&viewtype=text&pageseq=1), Edinburgh Review 3 (April 1860): 487–532. Published
anonymously.
• Wilberforce, Samuel (1860), "(Review of) On the Origin of Species, by means of Natural Selection; or the
Preservation of Favoured Races in the Struggle for Life" (http://darwin-online.org.uk/content/
frameset?itemID=A19&viewtype=text&pageseq=1), Quarterly Review 108 (215: July 1860): 225–264.
Published anonymously.
• For further reviews, see Darwin Online: Reviews & Responses to Darwin (http://darwin-online.org.uk/reviews.
html), Darwin Online, 10 March 2009, retrieved 2009-06-18

External links
• The Complete Works of Charles Darwin Online:
• Table of contents (http://darwin-online.org.uk/contents.html), bibliography of On the Origin of Species
(http://darwin-online.org.uk/EditorialIntroductions/Freeman_OntheOriginofSpecies.html) – links to text
and images of all six British editions of The Origin of Species, the 6th edition with additions and corrections
(final text), the first American edition, and translations into Danish, Dutch, French, German, Polish, Russian
and Spanish.
• Online Variorum (http://darwin-online.org.uk/Variorum/index.html), showing every change between the
six British editions.
• The Origin of Species: An Outline (http://www.vectorsite.net/taorgin.html), A short, accessible outline of the
book.
• Origin of Species (http://publicliterature.org/books/origin_of_species/xaa.php), full text with embedded
audio.
• Victorian Science Texts (http://www.victorianweb.org/science/texts.html)
• Darwin Correspondence Project Home Page (http://www.darwinproject.ac.uk), University Library,
Cambridge.
• PDF scans at Archive.org (http://www.archive.org/search.php?query=(origin species) AND creator:(darwin))
Darwinism 154

Darwinism
Darwinism is a set of movements and concepts related to ideas of
transmutation of species or evolution, including ideas with no
connection to the work of Charles Darwin.[1] [2] [3] The meaning of
Darwinism has changed over time, and varies depending on who is
using the term.[4] In the United States, Darwinism is often used by
creationists as a pejorative term but in the United Kingdom the term
has no negative connotations, being freely used as a short hand for
evolutionary theory.[5]

The term was coined by Thomas Henry Huxley in April 1860,[6] and
was used to describe evolutionary concepts, including earlier concepts
such as Malthusianism and Spencerism. In the late 19th century it
came to mean the concept that natural selection was the sole
mechanism of evolution, in contrast to Lamarckism, then around 1900
it was eclipsed by Mendelism until the modern evolutionary synthesis
Charles Darwin in 1868
unified Darwin's and Gregor Mendel's ideas. As modern evolutionary
theory has developed, the term has been associated at times with
specific ideas.[4]

While the term has remained in use amongst scientific authors, it is increasingly regarded as an inappropriate
description of modern evolutionary theory.[7] [8] [9] For example, Darwin was unfamiliar with the work of Gregor
Mendel,[10] having as a result only a vague and inaccurate understanding of heredity, and knew nothing of genetic
drift.[11]

Conceptions of Darwinism
While the term Darwinism had been used previously to refer to the
work of Erasmus Darwin in the late 18th century, the term as
understood today was introduced when Charles Darwin's 1859 book
On the Origin of Species was reviewed by Thomas Henry Huxley in
the April 1860 issue of the Westminster Review.[13] Having hailed the
book as, "a veritable Whitworth gun in the armoury of liberalism"
promoting scientific naturalism over theology, and praising the
usefulness of Darwin's ideas while expressing professional reservations
about Darwin's gradualism and doubting if it could be proved that
natural selection could form new species,[14] Huxley compared
Darwin's achievement to that of Copernicus in explaining planetary
motion:

What if the orbit of Darwinism should be a little too circular?

What if species should offer residual phenomena, here and there,
not explicable by natural selection? Twenty years hence
As "Darwinism" became widely accepted in the
naturalists may be in a position to say whether this is, or is not, 1870s, caricatures of Charles Darwin with an ape
the case; but in either event they will owe the author of "The [12]
or monkey body symbolised evolution.
Darwinism 155

Origin of Species" an immense debt of gratitude...... And viewed as a whole, we do not believe that, since the
publication of Von Baer's "Researches on Development," thirty years ago, any work has appeared calculated to
exert so large an influence, not only on the future of Biology, but in extending the domination of Science over
regions of thought into which she has, as yet, hardly penetrated.[6]
Another important evolutionariy theorist of the same period was Peter Kropotkin who, in his book Mutual Aid: A
Factor of Evolution, advocated a conception of Darwinism counter to that of Huxley. His conception was centred
around what he saw as the widespread use of cooperation as a survival mechanism in human societies and animals.
He used biological and sociological arguments in an attempt to show that the main factor in facilitating evolution is
cooperation between individuals in free-associated societies and groups. This was in order to counteract the
conception of fierce competition as the core of evolution, which provided a rationalisation for the dominant political,
economic and social theories of the time; and the prevalent interpretations of Darwinism, such as those by Huxley,
who is targeted as an opponent by Kropotkin. Kropotkin's conception of Darwinism could be summed up by the
following quote:
In the animal world we have seen that the vast majority of species live in societies, and that they find in
association the best arms for the struggle for life: understood, of course, in its wide Darwinian sense – not as a
struggle for the sheer means of existence, but as a struggle against all natural conditions unfavourable to the
species. The animal species, in which individual struggle has been reduced to its narrowest limits, and the
practice of mutual aid has attained the greatest development, are invariably the most numerous, the most
prosperous, and the most open to further progress. The mutual protection which is obtained in this case, the
possibility of attaining old age and of accumulating experience, the higher intellectual development, and the
further growth of sociable habits, secure the maintenance of the species, its extension, and its further
progressive evolution. The unsociable species, on the contrary, are doomed to decay.
– Peter Kropotkin, Mutual Aid: A Factor of Evolution (1902), Conclusion.

19th Century usage

"Darwinism" soon came to stand for an entire range of evolutionary (and often revolutionary) philosophies about
both biology and society. One of the more prominent approaches was that summed in the phrase "survival of the
fittest" by the philosopher Herbert Spencer, which was later taken to be emblematic of Darwinism even though
Spencer's own understanding of evolution was more similar to that of Jean-Baptiste Lamarck than to that of Darwin,
and predated the publication of Darwin's theory. What is now called "Social Darwinism" was, in its day,
synonymous with "Darwinism" — the application of Darwinian principles of "struggle" to society, usually in support
of anti-philanthropic political agendas. Another interpretation, one notably favoured by Darwin's half-cousin Francis
Galton, was that Darwinism implied that because natural selection was apparently no longer working on "civilised"
people it was possible for "inferior" strains of people (who would normally be filtered out of the gene pool) to
overwhelm the "superior" strains, and voluntary corrective measures would be desirable—the foundation of
eugenics.

“ [Both] a Darwinian 'left' and a Darwinian 'right' were in place before most people had grasped the Darwinian middle, which was where the
maker was.
[15]
”
In Darwin's day there was no rigid definition of the term "Darwinism", and it was used by opponents and proponents
of Darwin's biological theory alike to mean whatever they wanted it to in a larger context. The ideas had
international influence, and Ernst Haeckel developed what was known as Darwinismus in Germany, although, like
Spencer Haeckel's "Darwinism" had only a rough resemblance to the theory of Charles Darwin, and was not centred
on natural selection at all.
Darwinism 156

While the reaction against Darwin's ideas is nowadays often thought to have been widespread immediately, in 1886
Alfred Russel Wallace went on a lecture tour across the United States, starting in New York and going via Boston,
Washington, Kansas, Iowa and Nebraska to California, lecturing on what he called Darwinism without any
problems.[16]

Other uses
The term Darwinism is often used in the United States by promoters of creationism, notably by leading members of
the intelligent design movement, as an epithet to attack evolution as though it were an ideology (an "ism") of
philosophical naturalism, or atheism.[17] For example, Phillip E. Johnson makes this accusation of atheism with
reference to Charles Hodge's book What Is Darwinism?.[18] However, unlike Johnson, Hodge confined the term to
exclude those like Asa Gray who combined Christian faith with support for Darwin's natural selection theory, before
answering the question posed in the book's title by concluding: "It is Atheism."[19] [20] [21] Creationists use the term
Darwinism, often pejoratively, to imply that the theory has been held as true only by Darwin and a core group of his
followers, whom they cast as dogmatic and inflexible in their belief.[22] Casting evolution as a doctrine or belief, as
well as a pseudo-religious ideology like Marxism,[23] bolsters religiously motivated political arguments to mandate
equal time for the teaching of creationism in public schools.
However, Darwinism is also used neutrally within the scientific community to distinguish modern evolutionary
theories from those first proposed by Darwin, as well as by historians to differentiate it from other evolutionary
theories from around the same period. For example, Darwinism may be used to refer to Darwin's proposed
mechanism of natural selection, in comparison to more recent mechanisms such as genetic drift and gene flow. It
may also refer specifically to the role of Charles Darwin as opposed to others in the history of evolutionary thought
— particularly contrasting Darwin's results with those of earlier theories such as Lamarckism or later ones such as
the modern synthesis.
In the United Kingdom the term retains its positive sense as a reference to natural selection, and for example Richard
Dawkins wrote in his collection of essays A Devil's Chaplain, published in 2003, that as a scientist he is a
Darwinist.[24]

See also
• Darwinism (book)
• Modern evolutionary synthesis
• Neo-Darwinism
• Neural Darwinism
• Social Darwinism
• Darwin Awards
• Pangenesis - Charles Darwin's hypothetical mechanism for heredity
• Universal Darwinism
Darwinism 157

Notes
[1] John Wilkins (1998). "How to be Anti-Darwinian" (http:/ / www. talkorigins. org/ faqs/ anti-darwin. html). TalkOrigins Archive. . Retrieved
19 June 2008.
[2] "Expelled Exposed: Why Expelled Flunks » …on what evolution explains" (http:/ / www. expelledexposed. com/ index. php/ contest/
on-what-evolution-explains). National Center for Science Education. . Retrieved 22 December 2008.
[3] based on an European Southern Observatory release (9 December 2006). "Galactic Darwinism :: Astrobiology Magazine - earth science -
evolution distribution Origin of life universe - life beyond :: Astrobiology is study of earth science evolution distribution Origin of life in
universe terrestrial" (http:/ / www. astrobio. net/ news/ index. php?name=News& file=article& sid=2169& theme=Printer). . Retrieved 22
December 2008.
[4] Joel Hanes. "What is Darwinism?" (http:/ / www. talkorigins. org/ faqs/ darwinism. html). TalkOrigins Archive. . Retrieved 19 June 2008.
[5] Scott, Eugenie C.; Branch, Glenn (16 January 2009). "Don’t Call it “Darwinism”" (http:/ / www. springerlink. com/ content/
n47h34357743w4p0/ ?p=e3b030036a4d442a8ce393291fe0688f& pi=9). Evolution: Education and Outreach (New York: Springer) 2 (1): 90.
doi:10.1007/s12052-008-0111-2. ISSN 1936-6434. . Retrieved 17 November 2009.
[6] Huxley, T.H. (April 1860). "ART. VIII.- Darwin on the origin of Species" (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=side&
itemID=A32& pageseq=29). Westminster Review. pp. 541–70. . Retrieved 19 June 2008. "What if the orbit of Darwinism should be a little
too circular?"
[7] John Wilkins (1998). "How to be Anti-Darwinian" (http:/ / www. talkorigins. org/ faqs/ anti-darwin. html). TalkOrigins Archive. . Retrieved
27 June 2008.
[8] Ruse, Michael (2003). Darwin and Design: Does Evolution Have a Purpose? (http:/ / books. google. com/ ?id=SHWaeRiRD-cC&
printsec=frontcover& dq="michael+ ruse"+ darwinism). Cambridge, MA: Harvard University Press. pp. 293. ISBN 0674016319. . Retrieved
18 July 2008.
[9] Olivia Judson (15 July 2008). "Let’s Get Rid of Darwinism" (http:/ / judson. blogs. nytimes. com/ 2008/ 07/ 15/ lets-get-rid-of-darwinism/ ).
New York Times. .
[10] Sclater, Andrew (June 2006). "The extent of Charles Darwin’s knowledge of Mendel" (http:/ / www. springerlink. com/ content/
w112307246x77t37/ ). Journal of Biosciences (Bangalore, India: Springer India / Indian Academy of Sciences) 31 (2): 191–193.
doi:10.1007/BF02703910. PMID 16809850. . Retrieved 3 January 2009.
[11] Laurence Moran (1993). "Random Genetic Drift" (http:/ / www. talkorigins. org/ faqs/ genetic-drift. html). TalkOrigins Archive. . Retrieved
27 June 2008.
[12] Browne 2002, pp. 376–379
[13] "The Huxley File § 4 Darwin's Bulldog" (http:/ / aleph0. clarku. edu/ huxley/ guide4. html). . Retrieved 29 June 2008.
[14] Browne 2002, pp. 105–106
[15] Gopnik 2009, p. 152.
[16] "Evolution and Wonder - Understanding Charles Darwin - Speaking of Faith from American Public Media" (http:/ / speakingoffaith.
publicradio. org/ programs/ darwin/ transcript. shtml). . Retrieved 27 July 2007.
[17] Scott, Eugenie C. (2008). "Creation Science Lite: "Intelligent Design" as the New Anti-Evolutionism" (http:/ / biology. ucf. edu/ ~clp/
Courses/ seminar/ papers/ 07-Scott-scientists_confront-cs_lite. pdf). In Godfrey, Laurie R.; Petto, Andrew J.. Scientists Confront Creationism:
Intelligent Design and Beyond. New York: W. W. Norton. pp. 72. ISBN 0-393-33073-7.
[18] Johnson, Phillip E.. "What is Darwinism?" (http:/ / www. arn. org/ docs/ johnson/ wid. htm). . Retrieved 4 January 2007.
[19] Matthew, Ropp. "Charles Hodge and His Objection to Darwinism" (http:/ / www. theropps. com/ papers/ Winter1997/ CharlesHodge. htm). .
Retrieved 4 January 2007.
[20] Hodge, Charles. "What is Darwinism?" (http:/ / www. gutenberg. org/ files/ 19192/ 19192-8. txt). . Retrieved 4 January 2007.
[21] Hodge, Charles (1874). What is Darwinism?. Scribner, Armstrong, and Company. OCLC 11489956.
[22] Sullivan, M (2005). "From the Beagle to the School Board: God Goes Back to School" (http:/ / www. impactpress. com/ articles/ spring05/
sullivanspring05. html). Impact Press. . Retrieved 18 September 2008.
[23] "Darwinism should be allowed to collapse and end up on the ash heap of history" (http:/ / www. docstoc. com/ docs/ 20835072/
Darwinism-should-be-allowed-to-collapse-and-end-up-on-the-ash-heap-of-history). .
[24] Sheahen, Laura. Religion: For Dummies (http:/ / www. beliefnet. com/ story/ 136/ story_13688_1. html). BeliefNet.com, interview about
2003 book.
Darwinism 158

References
• Browne, E. Janet (2002). Charles Darwin: Vol. 2 The Power of Place. London: Jonathan Cape.
ISBN 0712668373.
• Gopnik, Adam (2009). Angels and Ages: A Short Book About Darwin, Lincoln, and Modern Life. London:
Quercus. ISBN 9781847249296.

External links
• Universal Darwinism (http://www.universaldarwinism.com)
• (Russian) Nikolai Danilevsky. 1885-1889 Darwinism. A Critical Study (http://new.runivers.ru/lib/book3542/)
(Дарвинизм. Критическое исследование) at Runivers.ru in DjVu format
• Stanford Encyclopedia of Philosophy entry (http://plato.stanford.edu/entries/darwinism/)
• What is Darwinism (http://www.talkorigins.org/faqs/darwinism.html)
• The Darwinian Revolution (http://www.evolution-of-man.info/history.htm)

The Genetical Theory of Natural Selection

The Genetical Theory of Natural Selection is a book by R.A. Fisher first published in 1930 by Clarendon. It is one
of the most important books of the modern evolutionary synthesis[1] and is commonly cited in biology books.

Editions
A second, slightly revised edition was republished in 1958. In 1999, a third variorum edition (ISBN 0-19-850440-3),
with the original 1930 text, annotated with the 1958 alterations, notes and alterations accidentally omitted from the
second edition was published, edited by Henry Bennett.

Chapters
It contains the following chapters:
1. The Nature of Inheritance [2]
2. The Fundamental Theorem of Natural Selection
3. The Evolution of Dominance
4. Variation as determined by Mutation and Selection
5. Variation etc
6. Sexual Reproduction and Sexual Selection [3]
7. Mimicry
8. Man and Society
9. The Inheritance of Human Fertility
10. Reproduction in Relation to Social Class
11. Social Selection of Fertility
12. Conditions of Permanent Civilization
''The Genetical Theory of Natural Selection'' 159

Contents
In the preface, Fisher considers some general points, including that there must be an understanding of natural
selection distinct from that of evolution, and that the then-recent advances in the field of genetics (see history of
genetics) now allowed this. In the first chapter, Fisher considers the nature of inheritance, rejecting blending
inheritance in favour of particulate inheritance. The second chapter introduces Fisher's fundamental theorem of
natural selection. The third considers the evolution of dominance, which Fisher believed was strongly influenced by
modifiers. The last five chapters (8-12) include Fisher's more idiosyncratic views on eugenics.

Dedication
The book is dedicated to Major Leonard Darwin, Fisher's friend, correspondent and son of Charles Darwin, "In
gratitude for the encouragement, given to the author, during the last fifteen years, by discussing many of the
problems dealt with in this book".

Reviews
Henry Bennett gave an account of the writing and reception of Fisher's Genetical Theory.[4]
Sewall Wright, who had many disagreements with Fisher, reviewed the book and wrote that it was "certain to take
rank as one of the major contributions to the theory of evolution".[5] J.B.S. Haldane described it as "brilliant".[6]
Reginald Punnett was negative, however.[7] '
The Genetical Theory was largely overlooked for 40 years, and in particular the fundamental theorem was
misunderstood. The work had a great effect on W.D. Hamilton, who discovered it as an undergraduate at Oxford[8]
and noted on the rear cover of the 1999 variorum edition:
This is a book which, as a student, I weighed as of equal importance to the entire rest of my undergraduate
Cambridge BA course and, through the time I spent on it, I think it notched down my degree. Most chapters
took me weeks, some months.
...And little modified even by molecular genetics, Fisher's logic and ideas still underpin most of the ever
broadening paths by which Darwinism continues its invasion of human thought.
Unlike in 1958, natural selection has become part of the syllabus of our intellectual life and the topic is
certainly included in every decent course in biology.
For a book that I rate only second in importance in evolution theory to Darwin's Origin (this as joined with its
supplement Of Man), and also rate as undoubtedly one of the greatest books of the twentieth century the
appearance of a variorum edition is a major event...
By the time of my ultimate graduation, will I have understood all that is true in this book and will I get a First?
I doubt it. In some ways some of us have overtaken Fisher; in many, however, this brilliant, daring man is still
far in front.
The publication of the variorum edition in 1999 led to renewed interest in the work and reviews by Laurence Cook
("This is perhaps the most important book on evolutionary genetics ever written"),[9] Brian Charlesworth,[10] Jim
Crow[11] and A.W.F. Edwards[12]
''The Genetical Theory of Natural Selection'' 160

References
[1] Grafen, Alan; Ridley, Mark (2006). Richard Dawkins: How A Scientist Changed the Way We Think. New York, New York: Oxford
University Press. p. 69. ISBN 0199291160.
[2] http:/ / www. blackwellpublishing. com/ ridley/ classictexts/ fisher1. pdf
[3] http:/ / www. blackwellpublishing. com/ ridley/ classictexts/ fisher2. pdf
[4] http:/ / digital. library. adelaide. edu. au/ coll/ special/ fisher/ natsel/ tp_intro. pdf
[5] Wright, S., 1930 The Genetical Theory of Natural Selection: a review (http:/ / jhered. oxfordjournals. org/ cgi/ reprint/ 21/ 8/ 349). J. Hered.
21:340-356.
[6] Haldane, J.B.S., 1932 The Causes of Evolution. Longman Green, London.
[7] Punnett, R.C. 1930, A review of The Genetical Theory of Natural Selection, Nature 126: 595-7
[8] Grafen, A. 2004. 'William Donald Hamilton’ (http:/ / users. ox. ac. uk/ ~grafen/ cv/ WDH_memoir. pdf). Biographical Memoirs of Fellows of
the Royal Society, 50, 109-132
[9] Cook, L. 2000 Book reviews. The Genetical Theory of Natural Selection — A Complete Variorum Edition. R. A. Fisher (edited by Henry
Bennett) (http:/ / www. nature. com/ hdy/ journal/ v84/ n3/ full/ 6887132a. html). Heredity 84 (3) , 390–39
[10] Charlesworth, B. 2000 The Genetical Theory of Natural Selection. A Complete Variorum Edition. By R. A. Fisher (edited with foreword
and notes by J. H. Bennett). Oxford University Press. 1999. ISBN 0-19-850440-3. xxi+318 pages. (http:/ / journals. cambridge. org/ action/
displayAbstract?fromPage=online& aid=52675) Genetics Research 75: 369-373
[11] Crow, J.F. 2000 Second only to Darwin - The Genetical Theory of Natural Selection. A Complete Variorum Edition by R.A. Fisher (http:/ /
www. sciencedirect. com/ science?_ob=ArticleURL& _udi=B6VJ1-405BR68-M& _user=10& _rdoc=1& _fmt=& _orig=search& _sort=d&
view=c& _acct=C000050221& _version=1& _urlVersion=0& _userid=10& md5=3a8c3a64ce75187ab109f4b0b9d18ba9) Trends in Ecology
and Evolution, Volume 15, Number 5, 1 May 2000 , pp. 213-214(2)
[12] Edwards, A.W.F. 2000 The Genetical Theory of Natural Selection (http:/ / www. genetics. org/ cgi/ content/ full/ 154/ 4/ 1419) Genetics,
Vol. 154, 1419-1426, April 2000

External links
• Full text of 1930 edition (http://www.openlibrary.org/details/geneticaltheoryo031631mbp), Open Library

Neo-Darwinism
Neo-Darwinism is a term used to describe the 'modern synthesis' of Darwinian evolution through natural selection
with Mendelian genetics, the latter being a set of primary tenets specifying that evolution involves the transmission
of characteristics from parent to child through the mechanism of genetic transfer, rather than the 'blending process' of
pre-Mendelian evolutionary science. Neo-Darwinism also separates Darwin's ideas of natural selection from his
hypothesis of Pangenesis as a Lamarckian source of variation involving blending inheritance.[1]
As part of the disagreement about whether natural selection alone was sufficient to explain speciation, George
Romanes coined the term neo-Darwinism to refer to the version of evolution advocated by Alfred Russel Wallace
and August Weismann with its heavy dependence on natural selection.[2] Weismann and Wallace rejected the
Lamarckian idea of inheritance of acquired characteristics, something that Darwin had not ruled out.[3] The term was
first used in 1895 to explain that evolution occurs solely through natural selection, in other words, without any
mechanism involving the inheritance of acquired characteristics resulting from use or disuse.[4] These two scientists'
complete rejection of Lamarckism came from Weismann's germ plasm theory. Weismann realised that the cells that
produce the germ plasm, or gametes (such as sperm and egg in animals), separate from the somatic cells that go on to
make other body tissues at an early stage in development. Since he could see no obvious means of communication
between the two he asserted that the inheritance of acquired characteristics was therefore impossible; a conclusion
now known as Weismann's barrier.[5]
From the 1880s to the 1930s the term continued to be applied to the panselectionist school of thought, which argued
that natural selection was the main and perhaps sole cause of all evolution.[6] From then until around 1947 the term
was used for the panselectionist followers of R. A. Fisher.
Neo-Darwinism 161

Modern evolutionary synthesis

Following the development, from about 1937 to 1950, of the modern evolutionary synthesis, now generally referred
to as the synthetic view of evolution or the modern synthesis, the term neo-Darwinian is often used to refer to
contemporary evolutionary theory.[7] However, such usage has been described by some as incorrect;[8] [1] [4] with
Ernst Mayr writing in 1984:
"...the term neo-Darwinism for the synthetic theory is wrong, because the term neo-Darwinism was coined by
Romanes in 1895 as a designation of Weismann's theory."'[9]
Despite this, publications such as the Encyclopaedia Britannica,[10] [11] use this term to refer to current evolutionary
theory. This term is also used in the scientific literature, with the academic publishers Blackwell Publishing referring
to "neo-Darwinism as practised today",[12] and some figures in the study of evolution like Richard Dawkins[13] and
Stephen Jay Gould,[14] using the term in their writings and lectures.

See also
• Modern evolutionary synthesis
• The Origin of Species
• Developmental systems theory
• Evolutionary developmental biology
• Neo-Lamarckism

References
[1] Kutschera U, Niklas KJ (2004). "The modern theory of biological evolution: an expanded synthesis". Naturwissenschaften 91 (6): 255–76.
doi:10.1007/s00114-004-0515-y. PMID 15241603.
[2] Gould The Structure of Evolutionary Theory p. 216
[3] Kutschera U. 2003. A comparative analysis of the Darwin-Wallace papers and the development of the concept of natural selection. Theory in
Biosciences 122, 343-359 (http:/ / www. springerlink. com/ content/ f6131358k265g3u4/ )
[4] Reif W-E. Junker T. Hoßfeld U. (2000). "The synthetic theory of evolution: general problems and the German contribution to the synthesis".
Theory in Biosciences 119 (1): 41–91(51). doi:10.1078/1431-7613-00004.
[5] Barbieri FD (1989). "The origin of Metazoa and Weismann's germ line theory". Riv. Biol. 82 (1): 61–74. PMID 2665023.
[6] "How to be Anti-Darwinian" (http:/ / www. talkorigins. org/ faqs/ anti-darwin. html). . Retrieved 2007-09-19.
[7] "The Modern Synthesis of Genetics and Evolution" (http:/ / www. talkorigins. org/ faqs/ modern-synthesis. html). . Retrieved 2007-09-19.
[8] Pigliucci, M. (2007). "Do We Need An Extended Evolutionary Synthesis?" (http:/ / www. bioone. org/ perlserv/ ?request=get-abstract).
Evolution 61 (12): 2743–2749. doi:10.1111/j.1558-5646.2007.00246.x. PMID 17924956. .
[9] Mayr E. (1984). "What is Darwinism Today?" (http:/ / links. jstor. org/ sici?sici=0270-8647(1984)1984<145:WIDT>2. 0. CO;2-5).
Proceedings of the Biennial Meeting of the Philosophy of Science Association 2: 145–156. .
[10] "neo-Darwinism" (http:/ / www. britannica. com/ eb/ article-9373225/ neo-Darwinism). Britannica.com. . Retrieved 2007-09-19.
[11] "neo-Darwinism" (http:/ / encyclopedia. farlex. com/ neo-Darwinism). Hutchinson Encyclopedia. . Retrieved 2007-09-19.
[12] "A-Z Browser of Evolution" (http:/ / www. blackwellpublishing. com/ ridley/ a-z/ Neo-Darwinism. asp). Blackwell Publishing. . Retrieved
2007-09-19.
[13] "Lecture on Neo-Darwinism" (http:/ / richarddawkins. net/ article,1345,Lecture-on-Neo-Darwinism,Richard-Dawkins). RichardDawkins.net
: The Official Richard Dawkins Website. . Retrieved 2007-09-19.
[14] "Challenges to Neo-Darwinism and Their Meaning for a Revised View of Human Consciousness" (http:/ / www. tannerlectures. utah. edu/
lectures/ documents/ gould85. pdf). Cambridge University: The Tanner Lectures on Human Values. . Retrieved 2009-03-05.
Neo-Darwinism 162

External links
• The Variation of Animals and Plants Under Domestication (http://www.esp.org/books/darwin/variation/
facsimile/title3.html)
• Challenges to neo-Darwinism - Stephen Jay Gould (http://web.archive.org/web/20060924065722/http://
www.tannerlectures.utah.edu/lectures/gould85.pdf) at the Wayback Machine (archived September 24, 2006).
• Neodarwinism - Richard Dawkins (http://video.google.com/videoplay?docid=4633079169415752395)

Modern evolutionary synthesis

The modern evolutionary synthesis is also referred to as the new synthesis, the modern synthesis, the
evolutionary synthesis and the neo-darwinian synthesis. It is a union of ideas from several biological specialties
which provides a widely accepted account of evolution. The synthesis reflects the current overwhelming
consensus.[1] The synthesis was produced over a decade (1936–1947). The previous development of population
genetics (1918–1932) was a stimulus, as it showed that Mendelian genetics was consistent with natural selection and
gradual evolution. The synthesis is still, to a large extent, the current paradigm in evolutionary biology.[2]
Julian Huxley invented the term, when he produced his book, Evolution: The Modern Synthesis (1942). Other major
figures in the modern synthesis include R. A. Fisher, Theodosius Dobzhansky, J.B.S. Haldane, Sewall Wright, E.B.
Ford, Ernst Mayr, Bernhard Rensch, Sergei Chetverikov, George Gaylord Simpson, and G. Ledyard Stebbins.
The modern synthesis solved difficulties and confusions caused by the specialisation and poor communication
between biologists in the early years of the 20th century. Discoveries of early geneticists were difficult to reconcile
with gradual evolution and the mechanism of natural selection. The synthesis reconciled the two schools of thought,
while providing evidence that studies of populations in the field were crucial to evolutionary theory. It drew together
ideas from several branches of biology that had become separated, particularly genetics, cytology, systematics,
botany, morphology, ecology and paleontology.

Summary of the modern synthesis

The modern synthesis bridged the gap between experimental geneticists and naturalists, and between both and
palaeontologists. It states that:[3] [4] [5]
1. All evolutionary phenomena can be explained in a way consistent with known genetic mechanisms and the
observational evidence of naturalists.
2. Evolution is gradual: small genetic changes, recombination ordered by natural selection. Discontinuities amongst
species (or other taxa) are explained as originating gradually through geographical separation and extinction (not
saltation).
3. Natural selection is by far the main mechanism of change; even slight advantages are important when continued.
The object of selection is the phenotype in its surrounding environment.
4. The role of genetic drift is equivocal. Though strongly supported initially by Dobzhansky, it was downgraded
later as results from ecological genetics were obtained.
5. Thinking in terms of populations, rather than individuals, is primary: the genetic diversity existing in natural
populations is a key factor in evolution. The strength of natural selection in the wild is greater than previously
expected; the effect of ecological factors such as niche occupation and the significance of barriers to gene flow
are all important.
6. In palaeontology, the ability to explain historical observations by extrapolation from microevolution to
macroevolution is proposed. Historical contingency means explanations at different levels may exist. Gradualism
does not mean constant rate of change.
Modern evolutionary synthesis 163

The idea that speciation occurs after populations are reproductively isolated has been much debated. In plants,
polyploidy must be included in any view of speciation. Formulations such as 'evolution consists primarily of changes
in the frequencies of alleles between one generation and another' were proposed rather later. The traditional view is
that developmental biology ('evo-devo') played little part in the synthesis,[6] but an account of Gavin de Beer's work
by Stephen J. Gould suggests he may be an exception.[7]

Developments leading up to the synthesis

1859–1899
Charles Darwin's The Origin of Species was successful in convincing most biologists that evolution had occurred,
but was less successful in convincing them that natural selection was its primary mechanism. In the 19th and early
20th centuries, variations of Lamarckism, orthogenesis ('progressive' evolution), and saltationism (evolution by
jumps) were discussed as alternatives.[8] Also, Darwin did not offer a precise explanation of how new species arise.
As part of the disagreement about whether natural selection alone was sufficient to explain speciation, George
Romanes coined the term neo-Darwinism to refer to the version of evolution advocated by Alfred Russel Wallace
and August Weismann with its heavy dependence on natural selection.[9] Weismann and Wallace rejected the
Lamarckian idea of inheritance of acquired characteristics, something that Darwin had not ruled out.[10]
Weismann's idea was that the relationship between the hereditary material, which he called the germ plasm (de:
Keimplasma), and the rest of the body (the soma) was a one-way relationship: the germ-plasm formed the body, but
the body did not influence the germ-plasm, except indirectly in its participation in a population subject to natural
selection. Weismann was translated into English, and though he was influential, it took many years for the full
significance of his work to be appreciated.[11] Later, after the completion of the modern synthesis, the term
neo-Darwinism came to be associated with its core concept: evolution, driven by natural selection acting on variation
produced by genetic mutation, and genetic recombination (chromosomal crossovers).[9]

1900–1915
Gregor Mendel's work was re-discovered by Hugo de Vries and Carl Correns in 1900. News of this reached William
Bateson in England, who reported on the paper during a presentation to the Royal Horticultural Society in May
1900.[12] It showed that the contributions of each parent retained their integrity rather than blending with the
contribution of the other parent. This reinforced a division of thought, which was already present in the 1890s.[13]
The two schools were:
• Saltationism (large mutations or jumps), favored by early Mendelians who viewed hard inheritance as
incompatible with natural selection[14]
• Biometric school: led by Karl Pearson and Walter Weldon, argued vigorously against it, saying that empirical
evidence indicated that variation was continuous in most organisms, not discrete as Mendelism predicted.
The relevance of Mendelism to evolution was unclear and hotly debated, especially by Bateson, who opposed the
biometric ideas of his former teacher Weldon. Many scientists believed the two theories substantially contradicted
each other.[15] This debate between the biometricians and the Mendelians continued for some 20 years and was only
solved by the development of population genetics.
T. H. Morgan began his career in genetics as a saltationist, and started out trying to demonstrate that mutations could
produce new species in fruit flies. However, the experimental work at his lab with Drosophila melanogaster, which
helped establish the link between Mendelian genetics and the chromosomal theory of inheritance, demonstrated that
rather than creating new species in a single step, mutations increased the genetic variation in the population.[16]
Modern evolutionary synthesis 164

The foundation of population genetics

The first step towards the synthesis was the development of population genetics. R.A. Fisher, J.B.S. Haldane, and
Sewall Wright provided critical contributions. In 1918, Fisher produced the paper "The Correlation Between
Relatives on the Supposition of Mendelian Inheritance",[17] which showed how the continuous variation measured
by the biometricians could be the result of the action of many discrete genetic loci. In this and subsequent papers
culminating in his 1930 book The Genetical Theory of Natural Selection, Fisher was able to show how Mendelian
genetics was, contrary to the thinking of many early geneticists, completely consistent with the idea of evolution
driven by natural selection.[18] During the 1920s, a series of papers by J.B.S. Haldane applied mathematical analysis
to real world examples of natural selection such as the evolution of industrial melanism in peppered moths.[] Haldane
established that natural selection could work in the real world at a faster rate than even Fisher had assumed.[19]
Sewall Wright focused on combinations of genes that interacted as complexes, and the effects of inbreeding on small
relatively isolated populations, which could exhibit genetic drift. In a 1932 paper he introduced the concept of an
adaptive landscape in which phenomena such as cross breeding and genetic drift in small populations could push
them away from adaptive peaks, which would in turn allow natural selection to push them towards new adaptive
peaks.[] Wright's model would appeal to field naturalists such as Theodosius Dobzhansky and Ernst Mayr who were
becoming aware of the importance of geographical isolation in real world populations.[19] The work of Fisher,
Haldane and Wright founded the discipline of population genetics. This is the precursor of the modern synthesis,
which is an even broader coalition of ideas.[] [19] [20]

The modern synthesis

Theodosius Dobzhansky, a Ukrainian emigrant, who had been a postdoctoral worker in Morgan's fruit fly lab, was
one of the first to apply genetics to natural populations. He worked mostly with Drosophila pseudoobscura. He says
pointedly: "Russia has a variety of climates from the Arctic to sub-tropical... Exclusively laboratory workers who
neither possess nor wish to have any knowledge of living beings in nature were and are in a minority".[21] Not
surprisingly, there were other Russian geneticists with similar ideas, though for some time their work was known to
only a few in the West. His 1937 work Genetics and the Origin of Species was a key step in bridging the gap
between population geneticists and field naturalists. It presented the conclusions reached by Fisher, Haldane, and
especially Wright in their highly mathematical papers in a form that was easily accessible to others. It also
emphasized that real world populations had far more genetic variability than the early population geneticists had
assumed in their models, and that genetically distinct sub-populations were important. Dobzhansky argued that
natural selection worked to maintain genetic diversity as well as driving change. Dobzhansky had been influenced by
his exposure in the 1920s to the work of a Russian geneticist named Sergei Chetverikov who had looked at the role
of recessive genes in maintaining a reservoir of genetic variability in a population before his work was shut down by
the rise of Lysenkoism in the Soviet Union.[] [19]
Edmund Brisco Ford's work complemented that of Dobzhansky. It was as a result of Ford's work, as well as his own,
that Dobzhansky changed the emphasis in the third edition of his famous text from drift to selection.[22] Ford was an
experimental naturalist who wanted to test natural selection in nature. He virtually invented the field of research
known as ecological genetics. His work on natural selection in wild populations of butterflies and moths was the first
to show that predictions made by R.A. Fisher were correct. He was the first to describe and define genetic
polymorphism, and to predict that human blood group polymorphisms might be maintained in the population by
providing some protection against disease.[23]
Ernst Mayr's key contribution to the synthesis was Systematics and the Origin of Species, published in 1942. Mayr
emphasized the importance of allopatric speciation, where geographically isolated sub-populations diverge so far
that reproductive isolation occurs. He was sceptical of the reality of sympatric speciation believing that geographical
isolation was a prerequisite for building up intrinsic (reproductive) isolating mechanisms. Mayr also introduced the
biological species concept that defined a species as a group of interbreeding or potentially interbreeding populations
Modern evolutionary synthesis 165

that were reproductively isolated from all other populations.[] [19] [24] Before he left Germany for the United States in
1930, Mayr had been influenced by the work of German biologist Bernhard Rensch. In the 1920s Rensch, who like
Mayr did field work in Indonesia, analyzed the geographic distribution of polytypic species and complexes of closely
related species paying particular attention to how variations between different populations correlated with local
environmental factors such as differences in climate. In 1947, Rensch published Neuere Probleme der
Abstammungslehre: die Transspezifische Evolution (English translation 1959: Evolution above the Species level).
This looked at how the same evolutionary mechanisms involved in speciation might be extended to explain the
origins of the differences between the higher level taxa. His writings contributed to the rapid acceptance of the
synthesis in Germany.[25] [26]
George Gaylord Simpson was responsible for showing that the modern synthesis was compatible with paleontology
in his book Tempo and Mode in Evolution published in 1944. Simpson's work was crucial because so many
paleontologists had disagreed, in some cases vigorously, with the idea that natural selection was the main mechanism
of evolution. It showed that the trends of linear progression (in for example the evolution of the horse) that earlier
paleontologists had used as support for neo-Lamarckism and orthogenesis did not hold up under careful examination.
Instead the fossil record was consistent with the irregular, branching, and non-directional pattern predicted by the
modern synthesis.[] [19]
The botanist G. Ledyard Stebbins was another major contributor to the synthesis. His major work, Variation and
Evolution in Plants, was published in 1950. It extended the synthesis to encompass botany including the important
effects of hybridization and polyploidy in some kinds of plants.[]

Further advances
The modern evolutionary synthesis continued to be developed and refined after the initial establishment in the 1930s
and 1940s. The work of W. D. Hamilton, George C. Williams, John Maynard Smith and others led to the
development of a gene-centric view of evolution in the 1960s. The synthesis as it exists now has extended the scope
of the Darwinian idea of natural selection to include subsequent scientific discoveries and concepts unknown to
Darwin, such as DNA and genetics, which allow rigorous, in many cases mathematical, analyses of phenomena such
as kin selection, altruism, and speciation.
A particular interpretation most commonly associated with Richard Dawkins, author of The Selfish Gene, asserts that
the gene is the only true unit of selection.[27] Dawkins further extended the Darwinian idea to include non-biological
systems exhibiting the same type of selective behavior of the 'fittest' such as memes in culture. The synthesis
continues to undergo regular review.[28] (See also Current research in evolutionary biology).
Modern evolutionary synthesis 166

After the synthesis

There are a number of discoveries in earth sciences and
biology which have arisen since the synthesis. Listed
here are some of those topics which are relevant to the
evolutionary synthesis, and which seem soundly based.

Understanding of Earth history

The Earth is the stage on which the evolutionary play is
performed. Darwin studied evolution in the context of
Charles Lyell's geology, but our present understanding
of Earth history includes some critical advances made
during the last half-century.
• The age of the Earth has been revised upwards. It is
now estimated at 4.56 billion years, about one-third
of the age of the universe. It is worth noting that the
Phanerozoic only occupies the last 1/9th of this
The structure of evolutionary biology.
period of time.[29]
The history and causes of evolution (center) are subject to various
• The triumph of Alfred Wegener's idea of continental subdisciplines of evolutionary biology. The areas of segments give
drift came around 1960. The key principle of plate an impression of the contributions of subdisciplines to the literature
of evolutionary biology.
tectonics is that the lithosphere exists as separate
and distinct tectonic plates, which ride on the
fluid-like (visco-elastic solid) asthenosphere. This discovery provides a unifying theory for geology, linking
phenomena such as volcanos, earthquakes, orogeny, and providing data for many paleogeographical questions.[30]
One major question is still unclear: when did plate tectonics begin?[31]

• Our understanding of the evolution of the Earth's atmosphere has progressed. The substitution of oxygen for
carbon dioxide in the atmosphere, which occurred in the Proterozoic, caused probably by cyanobacteria in the
form of stromatolites, caused changes leading to the evolution of aerobic organisms.[32] [33]
• The identification of the first generally accepted fossils of microbial life was made by geologists. These rocks
have been dated as about 3.465 billion years ago.[34] Walcott was the first geologist to identify pre-Cambrian
fossil bacteria from microscopic examination of thin rock slices. He also thought stromatolites were organic in
origin. His ideas were not accepted at the time, but may now be appreciated as great discoveries.[35]
• Information about paleoclimates is increasingly available, and being used in paleontology. One example: the
discovery of massive ice ages in the Proterozoic, following the great reduction of CO2 in the atmosphere. These
ice ages were immensely long, and led to a crash in microflora.[36] See also Cryogenian period and Snowball
Earth.
• Catastrophism and mass extinctions. A partial reintegration of catastrophism has occurred,[37] and the importance
of mass extinctions in large-scale evolution is now apparent. Extinction events disturb relationships between
many forms of life and may remove dominant forms and release a flow of adaptive radiation amongst groups that
remain. Causes include meteorite strikes (K–T junction; Upper Devonian); flood basalt provinces (Deccan traps
at K/T junction; Siberian traps at P–T junction); and other less dramatic processes.[38] [39]
Conclusion: Our present knowledge of earth history strongly suggests that large-scale geophysical events influenced
macroevolution and megaevolution. These terms refer to evolution above the species level, including such events as
mass extinctions, adaptive radiation, and the major transitions in evolution.[40] [41]
Modern evolutionary synthesis 167

Symbiotic origin of eukaryotic cell structures

Once symbiosis was discovered in lichen and in plant roots (rhizobia in root nodules) in the 19th century, the idea
arose that the process might have occurred more widely, and might be important in evolution. Anton de Bary
invented the concept of symbiosis;[42] several Russian biologists promoted the idea;[43] Edwin Wilson mentioned it
in his epic text The Cell;[44] a book was published in the U.S.A. in 1927 with the title Symbionticism and the origin
of species;[45] and there was a brief mention by Julian Huxley in 1930;[46] all in vain because sufficient evidence was
lacking. Symbiosis as a major evolutionary force was not discussed at all in the evolutionary synthesis.[47]
The role of symbiosis in cell evolution was revived partly by Joshua Lederberg,[48] and finally brought to light by
Lynn Margulis in a series of papers and books.[49] [50] It turns out that some cell organelles are of microbial origin:
mitochondria and chloroplasts definitely, cilia, flagella and centrioles possibly, and perhaps the nuclear membrane
and much of the chromosome structure as well. What is now clear is that the evolution of eukaryote cells is either
caused by, or at least profoundly influenced by, symbiosis with bacterial and archaean cells in the Proterozoic.
The origin of the eukaryote cell by symbiosis in several stages was not part of the evolutionary synthesis. It is, at
least on first sight, an example of megaevolution by big jumps. However, what symbiosis provided was a copious
supply of heritable variation from microorganisms, which was fine-tuned over a long period to produce the cell
structure we see today. This part of the process is consistent with evolution by natural selection.[51]

Trees of life
The ability to analyse sequence in macromolecules (protein, DNA, RNA) provides evidence of descent, and permits
us to work out genealogical trees covering the whole of life, since now there are data on every major group of living
organisms. This project, begun in a tentative way in the 1960s, has become a search for the universal tree or the
universal ancestor, a phrase of Carl Woese.[52] [53] The tree that results has some unusual features, especially in its
roots. There are two kingdoms of prokaryotes: bacteria and archaea, both of which contributed genetic material to
the eukaryotes, mainly by means of symbiosis. Also, since bacteria can pass genetic material to other bacteria, their
relationships look more like a web than a tree. Once eukaryotes were established, their sexual reproduction produced
the traditional branching tree-like pattern, the only diagram Darwin put in the Origin. The last universal ancestor
(LUA) would be a prokaryotic cell before the split between the bacteria and archaea. LUA is defined as most recent
organism from which all organisms now living on Earth descend (some 3.5 to 3.8 billion years ago, in the Archean
era).[54]
This technique may be used to clarify relationships within any group of related organisms. It is now a standard
procedure, and examples are published regularly. April 2009 sees the publication of a tree covering all the animal
phyla, derived from sequences from 150 genes in 77 taxa.[55]
Early attempts to identify relationships between major groups were made in the 19th century by Ernst Haeckel, and
by comparative anatomists such as Thomas Henry Huxley and E. Ray Lankester. Enthusiasm waned: it was often
difficult to find evidence to adjudicate between different opinions. Perhaps for that reason, the evolutionary synthesis
paid surprisingly little attention to this activity. It is certainly a lively field of research today.

Evo-devo
What once was called embryology played a modest role in the evolutionary synthesis,[56] mostly about evolution by
changes in developmental timing (allometry and heterochrony).[57] Man himself was, according to Bolk, a typical
case of evolution by retention of juvenile characteristics (neoteny). He listed many characters where "Man, in his
bodily development, is a primate foetus that has become sexually mature".[58] Unfortunately, his interpretation of
these ideas was non-Darwinian, but his list of characters is both interesting and convincing.[59]
Modern interest in Evo-devo springs from clear proof that development is closely controlled by special genetic
systems, and the hope that comparison of these systems will tell us much about the evolutionary history of different
groups.[60] [61] In a series of experiments with the fruit-fly Drosophila, Edward B. Lewis was able to identify a
Modern evolutionary synthesis 168

complex of genes whose proteins bind to the cis-regulatory regions of target genes. The latter then activate or repress
systems of cellular processes that accomplish the final development of the organism.[62] [63] Furthermore, the
sequence of these control genes show co-linearity: the order of the loci in the chromosome parallels the order in
which the loci are expressed along the anterior-posterior axis of the body. Not only that, but this cluster of master
control genes programs the development of all higher organisms.[64] [65] Each of the genes contains a homeobox, a
remarkably conserved DNA sequence. This suggests the complex itself arose by gene duplication.[66] [67] [68] In his
Nobel lecture, Lewis said "Ultimately, comparisons of the [control complexes] throughout the animal kingdom
should provide a picture of how the organisms, as well as the [control genes] have evolved".
The term deep homology was coined to describe the common origin of genetic regulatory apparatus used to build
morphologically and phylogenetically disparate animal features.[69] It applies when a complex genetic regulatory
system is inherited from a common ancestor, as it is in the evolution of vertebrate and invertebrate eyes. The
phenomenon is implicated in many cases of parallel evolution.[70]
A great deal of evolution may take place by changes in the control of development. This may be relevant to
punctuated equilibrium theory, for in development a few changes to the control system could make a significant
difference to the adult organism. An example is the giant panda, whose place in the Carnivora was long uncertain.[71]
Apparently, the giant panda's evolution required the change of only a few genetic messages (5 or 6 perhaps), yet the
phenotypic and lifestyle change from a standard bear is considerable.[72] [73] The transition could therefore be
effected relatively swiftly.

Fossil discoveries
In the past thirty or so years there have been excavations in parts of the world which had scarcely been investigated
before. Also, there is fresh appreciation of fossils discovered in the 19th century, but then denied or deprecated: the
classic example is the Ediacaran biota from the immediate pre-Cambrian, after the Cryogenian period. These
soft-bodied fossils are the first record of multicellular life. The interpretation of this fauna is still in flux.
Many outstanding discoveries have been made, and some of these have implications for evolutionary theory. The
discovery of feathered dinosaurs and early birds from the Lower Cretaceous of Liaoning, N.E. China have convinced
most students that birds did evolve from coelurosaurian theropod dinosaurs. Less well known, but perhaps of equal
evolutionary significance, are the studies on early insect flight, on stem tetrapods from the Upper Devonian,[74] [75]
and the early stages of whale evolution.[76]
A shaft of light has been thrown on the evolution of flatfish (pleuronectiformes), such as plaice, sole, turbot and
halibut, by recent work. Flatfish are interesting because they are one of the few vertebrate groups with external
asymmetry. Their young are perfectly symmetrical, but the head is remodelled during a metamorphosis, which
entails the migration of one eye to the other side, close to the other eye. Some species have both eyes on the left
(turbot), some on the right (halibut, sole); all living and fossil flatfish to date show an 'eyed' side and a 'blind' side.[77]
The lack of an intermediate condition in living and fossil flatfish species had led to debate about the origin of such a
striking adaptation. The case was considered by Lamark,[78] who thought flatfish precursors would have lived in
shallow water for a long period, and by Darwin, who predicted a gradual migration of the eye, mirroring the
metamorphosis of the living forms. Darwin's long-time critic St. George Mivart thought that the intermediate stages
could have no selective value,[79] and in the 6th edition of the Origin, Darwin made a concession to the possibility of
acquired traits.[80] Many years later the geneticist Richard Goldschmidt put the case forward as an example of
evolution by saltation, bypassing intermediate forms.[81] [82]
A recent examination of two fossil species from the Eocene has provided the first clear picture of flatfish evolution.
The discovery of stem flatfish with incomplete orbital migration refutes Goldschmidt's ideas, and demonstrates that
"the assembly of the flatfish bodyplan occurred in a gradual, stepwise fashion".[83] There are no grounds for thinking
that incomplete orbital migration was maladaptive, because stem forms with this condition ranged over two
geological stages, and are found in localities which also yield flatfish with the full cranial asymmetry. The evolution
Modern evolutionary synthesis 169

of flatfish falls squarely within the evolutionary synthesis.[77]

See also
• Developmental systems theory
• Evolution
• Gene-centered view of evolution
• History of evolutionary thought
• Particulate inheritance theory
• Polymorphism (biology)
• Population genetics
• The Origin of Species

Footnotes
[1] "The scientific consensus around evolution is overwhelming". "Appendix: Frequently Asked Questions" (http:/ / www. nap. edu/ openbook.
php?record_id=6024& page=27#p200064869970027001) (php). Science and Creationism: A View from the National Academy of Sciences
(http:/ / books. nap. edu/ openbook. php?record_id=6024& page=28) (Second ed.). Washington, DC: The National Academy of Sciences.
1999. p. 28. ISBN ISBN-0-309-06406-6. . Retrieved September 24, 2009.
[2] Mayr, Ernst 2002. What evolution is. Weidenfeld & Nicolson, London. p270
[3] Huxley J.S. 1942. Evolution: the modern synthesis. Allen & Unwin, London. 2nd ed 1963; 3rd ed 1974.
[4] Mayr & Provine 1998
[5] Mayr E. 1982. The growth of biological thought: diversity, evolution & inheritance. Harvard, Cambs. p567 et seq.
[6] Smocovitis, V. Betty. 1996. Unifying Biology: the evolutionary synthesis and evolutionary biology. Princeton University Press. p192
[7] Gould S.J. Ontogeny and phylogeny. Harvard 1977. p221-2
[8] Bowler P.J. 2003. Evolution: the history of an idea. pp236–256
[9] Gould The Structure of Evolutionary Theory p. 216
[10] Kutschera U. 2003. A comparative analysis of the Darwin-Wallace papers and the development of the concept of natural selection. Theory in
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[11] Bowler pp. 253–256
[12] Mike Ambrose. "Mendel's Peas" (http:/ / www. jic. ac. uk/ germplas/ pisum/ zgs4f. htm). Genetic Resources Unit, John Innes Centre,
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[13] Bateson, William 1894. Materials for the study of variation, treated with special regard to discontinuity in the origin of species. The
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[14] Larson pp. 157–166
[15] Grafen, Alan; Ridley, Mark (2006). Richard Dawkins: How A Scientist Changed the Way We Think. New York, New York: Oxford
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[16] Bowler pp. 271–272
[17] Transactions of the Royal Society of Edinburgh, 52:399–433
[18] Larson Evolution: The Remarkable History of a Scientific Theory pp. 221–243
[19] Bowler Evolution: The history of an Idea pp. 325–339
[20] Gould The Structure of Evolutionary Theory pp. 503–518
[21] Mayr & Provine 1998 p. 231
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[77] Janvier, Philip 2008. Squint of the fossil flatfish. Nature 454, 169
[78] Lamark J.B. 1809. Philosophie zoologique. Paris.
[79] Mivart St G. 1871. The genesis of species. Macmillan, London.
[80] Darwin, Charles 1872. The origin of species. 6th ed, Murray, London. p186–188. The whole of Chapter 7 in this edition is taken up with
answering critics of natural selection.
Modern evolutionary synthesis 171

[81] Goldschmidt R. Some aspects of evolution. Science 78, 539–547.

[82] Goldschmidt R. 1940. The material basis of evolution. Yale.
[83] Friedman, Matt 2008. The evolutionary origin of flatfish asymmetry. Nature 454, 209–212.

References
• Allen, Garland. Thomas Hunt Morgan: The Man and His Science, Princeton University Press, 1978 ISBN
0-691-08200-6
• Bowler, Peter J. (2003). Evolution:The History of an Idea. University of California Press. ISBN 0-52023693-9.
• Dawkins, Richard. The Blind Watchmaker, W.W. Norton and Company, Reissue Edition 1996 ISBN
0-393-31570-3
• Dobzhansky, T. Genetics and the Origin of Species, Columbia University Press, 1937 ISBN 0-231-05475-0
• Fisher, R. A. The Genetical Theory of Natural Selection, Clarendon Press, 1930 ISBN 0-19-850440-3
• Futuyma, D.J. Evolutionary Biology, Sinauer Associates, 1986, p. 12 0-87-893189-9
• Gould, Stephen Jay (2002). The Structure of Evolutionary Theory. Belknap Press of Harvard University Press.
ISBN 0-674-00613-5.
• Haldane, J. B. S. The Causes of Evolution, Longman, Green and Co., 1932; Princeton University Press reprint,
ISBN 0-691-02442-1
• Huxley, J. S., ed. The New Systematics, Oxford University Press, 1940 ISBN 0-403-01786-6
• Huxley, J. S. Evolution: The Modern Synthesis, Allen and Unwin, 1942 ISBN 0-02-846800-7
• Larson, Edward J. (2004). Evolution:The Remarkable History of a Scientific Theory. Modern Library.
ISBN 0-679-64288-9.
• Margulis, Lynn and Dorion Sagan. "Acquiring Genomes: A Theory of the Origins of Species", Perseus Books
Group, 2002 ISBN 0-465-04391-7
• Mayr, E. Systematics and the Origin of Species, Columbia University Press, 1942; Harvard University Press
reprint ISBN 0-674-86250-3
• Mayr, E. and W. B. Provine, eds. The Evolutionary Synthesis: Perspectives on the Unification of Biology, Harvard
University Press, 1998 ISBN 0-674-27225-0
• Simpson, G. G. Tempo and Mode in Evolution, Columbia University Press, 1944 ISBN 0-231-05847-0
• Smocovitis, V. Betty. Unifying Biology: The Evolutionary Synthesis and Evolutionary Biology, Princeton
University Press, 1996 ISBN 0-691-27226-9
• Wright, S. 1931. "Evolution in Mendelian populations". Genetics 16: 97–159.

External links
• Rose MR, Oakley TH, The new biology: beyond the Modern Synthesis (http://www.biology-direct.com/
content/pdf/1745-6150-2-30.pdf). Biology Direct 2007, 2:30. A review of biology in light of recent innovations
since the initiation of modern synthesis.
 172

Base concepts

Heredity
Heredity is the passing of traits to offspring (from its parent or ancestors). This is the process by which an offspring
cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism. Through
heredity, variations exhibited by individuals can accumulate and cause a species to evolve. The study of heredity in
biology is called genetics, which includes the field of epigenetics.

History
The ancients had a variety of ideas about heredity: Theophrastus proposed that male flowers caused female flowers
to ripen; Hippocrates speculated that "seeds" were produced by various body parts and transmitted to offspring at the
time of conception, and Aristotle thought that male and female semen mixed at conception. Aeschylus, in 458 BC,
proposed the male as the parent, with the female as a "nurse for the young life sown within her."
Various hereditary mechanisms were envisaged without being properly tested or quantified. These included blending
inheritance and the inheritance of acquired traits. Nevertheless, people were able to develop domestic breeds of
animals as well as crops through artificial selection. The inheritance of acquired traits also formed a part of early
Lamarckian ideas on evolution.
In the 9th century AD, the Afro-Arab writer Al-Jahiz considered the effects of the environment on the likelihood of
an animal to survive, and first described the struggle for existence.[1] [2] His ideas on the struggle for existence in the
Book of Animals have been summarized as follows:
"Animals engage in a struggle for existence; for resources, to avoid being eaten and to breed. Environmental
factors influence organisms to develop new characteristics to ensure survival, thus transforming into new
species. Animals that survive to breed can pass on their successful characteristics to offspring."[3]
In 1000 AD, the Arab physician, Abu al-Qasim al-Zahrawi (known as Albucasis in the West), wrote the first clear
description of haemophilia, a hereditary genetic disorder, in his Al-Tasrif. In this work, he wrote of an Andalusian
family whose males died of bleeding after minor injuries.[4]
During the 18th century, Dutch microscopist Antonie van Leeuwenhoek (1632–1723) discovered "animalcules" in
the sperm of humans and other animals. Some scientists speculated they saw a "little man" (homunculus) inside each
sperm. These scientists formed a school of thought known as the "spermists." They contended the only contributions
of the female to the next generation were the womb in which the homunculus grew, and prenatal influences of the
womb. An opposing school of thought, the ovists, believed that the future human was in the egg, and that sperm
merely stimulated the growth of the egg. Ovists thought women carried eggs containing boy and girl children, and
that the gender of the offspring was determined well before conception.
Pangenesis was an idea that males and females formed "pangenes" in every organ. These pangenes subsequently
moved through their blood to the genitals and then to the children. The concept originated with the ancient Greeks,
and influenced biology until as recently as a century ago. The terms "blood relative," "bloodline," "full-blooded,"
and "royal blood" are relics of pangenesis. Francis Galton, Charles Darwin's cousin, experimentally tested and
disproved pangenesis during the 1870s.
Heredity 173

Types of heredity
Dominant and recessive
An allele is said to be dominant if it is always expressed in the appearance of an organism (phenotype). For example,
in peas the allele for green pods, G, is dominant to that for yellow pods, g. Since the allele for green pods is
dominant, pea plants with the pair of alleles GG (homozygote) or Gg (heterozygote) will have green pods. The allele
for yellow pods is recessive. The effects of this allele are only seen when it is present in both chromosomes, gg
(homozygote).
The description of a mode of biological inheritance consists of three main categories:
1. Number of involved loci
• Monogenetic (also called "simple") – one locus
• Oligogenetic – few loci
• Polygenetic – many loci
2. Involved chromosomes
• Autosomal – loci are not situated on a sex chromosome
• Gonosomal – loci are situated on a sex chromosome
• X-chromosomal – loci are situated on the X chromosome (the more common case)
• Y-chromosomal – loci are situated on the Y chromosome
• Mitochondrial – loci are situated on the mitochondrial DNA
3. Correlation genotype–phenotype
• Dominant
• Intermediate (also called "codominant")
• Recessive
These three categories are part of every exact description of a mode of inheritance in the above order. Additionally,
more specifications may be added as follows:
4. Coincidental and environmental interactions
• Penetrance
• Complete
• Incomplete (percentual number)
• Expressivity
• Invariable
• Variable
• Heritability (in polygenetic and sometimes also in oligogenetic modes of inheritance)
• Maternal or paternal imprinting phenomena (also see epigenetics)
5. Sex-linked interactions
• Sex-linked inheritance (gonosomal loci)
• Sex-limited phenotype expression (e.g., cryptorchism)
• Inheritance through the maternal line (in case of mitochondrial DNA loci)
• Inheritance through the paternal line (in case of Y-chromosomal loci)
6. Locus–locus interactions
• Epistasis with other loci (e.g., overdominance)
• Gene coupling with other loci (also see crossing over)
• Homozygotous lethal factors
• Semi-lethal factors
Heredity 174

Determination and description of a mode of inheritance is primarily achieved through statistical analysis of pedigree
data. In case the involved loci are known, methods of molecular genetics can also be employed.

Charles Darwin: theory of evolution

When Charles Darwin proposed his theory of evolution in 1859, one of its major problems was the lack of an
underlying mechanism for heredity. Darwin believed in a mix of blending inheritance and the inheritance of acquired
traits (pangenesis). Blending inheritance would lead to uniformity across populations in only a few generations and
thus would remove variation from a population on which natural selection could act. This led to Darwin adopting
some Lamarckian ideas in later editions of On the Origin of Species and his later biological works. Darwin's primary
approach to heredity was to outline how it appeared to work (noticing that traits could be inherited which were not
expressed explicitly in the parent at the time of reproduction, that certain traits could be sex-linked, etc.) rather than
suggesting mechanisms.
Darwin's initial model of heredity was adopted by, and then heavily modified by, his cousin Francis Galton, who laid
the framework for the biometric school of heredity. Galton rejected the aspects of Darwin's pangenesis model which
relied on acquired traits.
The inheritance of acquired traits was shown to have little basis in the 1880s when August Weismann cut the tails off
many generations of mice and found that their offspring continued to develop tails.

Gregor Mendel: father of modern genetics

The idea of particulate inheritance of genes can be attributed to the Moravian[5] monk Gregor Mendel who published
his work on pea plants in 1865. However, his work was not widely known and was rediscovered in 1901. It was
initially assumed the Mendelian inheritance only accounted for large (qualitative) differences, such as those seen by
Mendel in his pea plants—and the idea of additive effect of (quantitative) genes was not realised until R.A. Fisher's
(1918) paper, "The Correlation Between Relatives on the Supposition of Mendelian Inheritance."

Modern development of genetics and heredity

In the 1930s, work by Fisher and others resulted in a combination of Mendelian and biometric schools into the
modern evolutionary synthesis. The modern synthesis bridged the gap between experimental geneticists and
naturalists; and between both and palaeontologists, stating that:[6] [7]
1. All evolutionary phenomena can be explained in a way consistent with known genetic mechanisms and the
observational evidence of naturalists.
2. Evolution is gradual: small genetic changes, recombination ordered by natural selection. Discontinuities amongst
species (or other taxa) are explained as originating gradually through geographical separation and extinction (not
saltation).
3. Selection is overwhelmingly the main mechanism of change; even slight advantages are important when
continued. The object of selection is the phenotype in its surrounding environment. The role of genetic drift is
equivocal; though strongly supported initially by Dobzhansky, it was downgraded later as results from ecological
genetics were obtained.
4. The primacy of population thinking: the genetic diversity carried in natural populations is a key factor in
evolution. The strength of natural selection in the wild was greater than expected; the effect of ecological factors
such as niche occupation and the significance of barriers to gene flow are all important.
5. In palaeontology, the ability to explain historical observations by extrapolation from micro to macro-evolution is
proposed. Historical contingency means explanations at different levels may exist. Gradualism does not mean
constant rate of change.
Heredity 175

The idea that speciation occurs after populations are reproductively isolated has been much debated. In plants,
polyploidy must be included in any view of speciation. Formulations such as 'evolution consists primarily of changes
in the frequencies of alleles between one generation and another' were proposed rather later. The traditional view is
that developmental biology ('evo-devo') played little part in the synthesis, but an account of Gavin de Beer's work by
Stephen Jay Gould suggests he may be an exception.[8]
Almost all aspects of the synthesis have been challenged at times, with varying degrees of success. There is no
doubt, however, that the synthesis was a great landmark in evolutionary biology. It cleared up many confusions, and
was directly responsible for stimulating a great deal of research in the post-World War II era.
Trofim Lysenko however caused a backlash of what is now called Lysenkoism in the Soviet Union when he
emphasised Lamarckian ideas on the inheritance of acquired traits. This movement affected agricultural research and
led to food shortages in the 1960s and seriously affected the USSR.

See also
• Genetics
• Hard inheritance
• Heritability

Notes and references

[1] Conway Zirkle (1941). Natural Selection before the "Origin of Species", Proceedings of the American Philosophical Society 84 (1), p.
71-123.
[2] Mehmet Bayrakdar (Third Quarter, 1983). "Al-Jahiz And the Rise of Biological Evolutionism", The Islamic Quarterly. London. (http:/ /
www. salaam. co. uk/ knowledge/ al-jahiz. php)
[3] Gary Dargan, Intelligent Design (http:/ / www. abc. net. au/ rn/ encounter/ stories/ 2006/ 1656361. htm), Encounter, ABC.
[4] Patricia Skinner (2001), Unani-tibbi (http:/ / findarticles. com/ p/ articles/ mi_g2603/ is_0007/ ai_2603000716), Encyclopedia of Alternative
Medicine
[5] Henig, Robin Marantz (2000). The Monk in the Garden : The Lost and Found Genius of Gregor Mendel, the Father of Genetics. Houghton
Mifflin. ISBN 0-395-97765-7. "The article, written by an obscure Moravian monk named Gregor Mendel"
[6] Mayr & Provine 1998
[7] Mayr E. 1982. The growth of biological thought: diversity, evolution & inheritance. Harvard, Cambs. p567 et seq.
[8] Gould S.J. Ontogeny and phylogeny. Harvard 1977. p221-2

External links
• Stanford Encyclopedia of Philosophy entry on Heredity and Heritability (http://plato.stanford.edu/entries/
heredity/)
Fitness 176

Fitness
Fitness (often denoted in population genetics models) is a central idea in evolutionary theory. It can be defined
either with respect to a genotype or to a phenotype. In either case, it is equal to the average contribution to the gene
pool of the next generation that is made by an average individual of the specified genotype or phenotype. If
differences between alleles at a given gene affect fitness, then the frequencies of the alleles will change over
generations; the alleles with higher fitness become more common. This process is called natural selection.
An individual's fitness is manifested through its phenotype. As phenotype is affected by both genes and environment,
the fitnesses of different individuals with the same genotype are not necessarily equal, but depend on the
environment in which the individuals live. However, since the fitness of the genotype is an averaged quantity, it will
reflect the reproductive outcomes of all individuals with that genotype.
Inclusive fitness differs from individual fitness by including the ability of an allele in one individual to promote the
survival and/or reproduction of other individuals that share that allele, in preference to individuals with a different
allele. One mechanism of inclusive fitness is kin selection.

Measures of fitness
There are two commonly used measures of fitness; absolute fitness and relative fitness.

Absolute fitness
Absolute fitness ( ) of a genotype is defined as the ratio between the number of individuals with that genotype
after selection to those before selection. It is calculated for a single generation and may be calculated from absolute
numbers or from frequencies. When the fitness is larger than 1.0, the genotype increases in frequency; a ratio smaller
than 1.0 indicates a decrease in frequency.

Absolute fitness for a genotype can also be calculated as the product of the proportion survival times the average
fecundity.

Relative fitness
Relative fitness is quantified as the average number of surviving progeny of a particular genotype compared with
average number of surviving progeny of competing genotypes after a single generation, i.e. one genotype is
normalized at and the fitnesses of other genotypes are measured with respect to that genotype. Relative
fitness can therefore take any nonnegative value, including 0.
While researchers can usually measure relative fitness, absolute fitness is more difficult. It is often difficult to
determine how many individuals of a genotype there were immediately after reproduction.
The two concepts are related, and both of them are equivalent when they are divided by the mean fitness, which is
weighted by genotype frequencies.

Because fitness is a coefficient, and a variable may be multiplied by it several times, biologists may work with "log
fitness" (particularly so before the advent of computers). By taking the logarithm of fitness each term may be added
rather than multiplied.
Fitness 177

Maynard-Smith's Definition
As another example we may mention the definition of fitness given by Maynard Smith in the following way:
"Fitness is a property, not of an individual, but of a class of individuals – for example homozygous for allele A at a
particular locus. Thus the phrase ’expected number of offspring’ means the average number, not the number
produced by some one individual. If the first human infant with a gene for levitation were struck by lightning in its
pram, this would not prove the new genotype to have low fitness, but only that the particular child was unlucky." [1]

Hartl's Definition
Yet another possible measure has been formulated: "The fitness of the individual - having an array x of phenotypes
- is the probability, s(x), that the individual will be included among the group selected as parents of the next
generation." Then, the mean fitness may be determined as a mean over the set of individuals in a large population.
[2]

where N is the probability distribution function of phenotypes in the population, and m is its centre of gravity. This
measure is a suitable basis of a model of an evolution selecting individuals. It may in principle take even the stroke
of the lightning into consideration. In the case N is a Gaussian it is fairly easily proved that the average information
(information entropy, disorder, diversity) of a large population may be maximized by Gaussian adaptation - keeping
the mean fitness constant - in accordance with recapitulation, the central limit theorem, the Hardy-Weinberg law and
the second law of thermodynamics. This is in contrast to Fisher's fundamental theorem of natural selection.

History
The British sociologist Herbert Spencer coined the phrase "survival of the fittest" (though originally, and perhaps
more accurately, "survival of the best fitted") in his 1851 work Social Statics and later used it to characterise what
Charles Darwin had called natural selection.
The British biologist J.B.S. Haldane was the first to quantify fitness, in terms of the modern evolutionary synthesis
of Darwinism and Mendelian genetics starting with his 1924 paper A Mathematical Theory of Natural and Artificial
Selection. The next further advance was the introduction of the concept of inclusive fitness by the British biologist
W.D. Hamilton in 1964 in his paper on The Evolution of Social Behavior.

Fitness landscape
A fitness landscape, first conceptualized by Sewall Wright, is a way of visualising fitness in terms of a
high-dimensional surface, in which height indicates fitness, and each of the other dimensions represents allele
identity for a different gene. Peaks correspond to local fitness maxima; it is often said that natural selection always
progresses uphill but can only do so locally. This can result in suboptimal local maxima becoming stable, because
natural selection cannot return to the less-fit "valleys" of the landscape on the way to reach higher peaks.
Fitness 178

Genetic load
Genetic load measures the average fitness of a population of individuals, relative to a hypothetical population in
which the most fit genotype has become fixed.

See also
• Gene-centered view of evolution
• Inclusive fitness
• Natural selection
• Reproductive success
• Selection coefficient

Notes
[1] Maynard-Smith, J. (1989) Evolutionary Genetics ISBN 0198542151
[2] Hartl, D. L. (1981) A Primer of Population Genetics ISBN 0878932712

Further reading
• Sober, E. (2001). The Two Faces of Fitness. In R. Singh, D. Paul, C. Krimbas, and J. Beatty (Eds.), Thinking
about Evolution: Historical, Philosophical, and Political Perspectives. Cambridge University Press, pp.309-321.
Full text (http://philosophy.wisc.edu/sober/tff.pdf)
• Orr HA (August 2009). "Fitness and its role in evolutionary genetics" (http://www.pubmedcentral.nih.gov/
articlerender.fcgi?tool=pmcentrez&artid=2753274). Nat. Rev. Genet. 10 (8): 531–9. doi:10.1038/nrg2603.
PMID 19546856. PMC 2753274.

External links
• Evolution A-Z: Fitness (http://www.blackwellpublishing.com/ridley/a-z/Fitness.asp)
• Stanford Encyclopedia of Philosophy entry (http://plato.stanford.edu/entries/fitness/)
Common descent 179

Common descent
In evolutionary biology, a group of organisms have common descent if they have a common ancestor. "There is
strong quantitative support, by a formal test"[1] for the theory that all living organisms on Earth are descended from a
common ancestor.[2]
Charles Darwin proposed the theory of universal common descent through an evolutionary process in On the Origin
of Species, saying, "There is a grandeur in this view of life, with its several powers, having been originally breathed
into a few forms or into one".[3]
The last universal ancestor (LUA) (or last universal common ancestor, LUCA), that is, the most recent common
ancestor of all currently living organisms,[1] is believed to have appeared about 3.9 billion years ago.[4] [5]
In The Ancestor's Tale, Richard Dawkins coined the word concestor, as a substitute for common ancestor or most
recent common ancestor. This new word is very gradually entering scientific parlance.[6]

History
In the 1740s, Pierre-Louis Moreau de Maupertuis made the first known suggestion in a series of essays that all
organisms may have had a common ancestor, and that they had diverged through random variation and natural
selection.[7] [8] In Essai de Cosmologie, Maupertuis noted:
Could one not say that, in the fortuitous combinations of the productions of nature, as there must be
some characterized by a certain relation of fitness which are able to subsist, it is not to be wondered at
that this fitness is present in all the species that are currently in existence? Chance, one would say,
produced an innumerable multitude of individuals; a small number found themselves constructed in such
a manner that the parts of the animal were able to satisfy its needs; in another infinitely greater number,
there was neither fitness nor order: all of these latter have perished. Animals lacking a mouth could not
live; others lacking reproductive organs could not perpetuate themselves ... The species we see today are
but the smallest part of what blind destiny has produced ...[9]
In 1790, Immanuel Kant wrote in Kritik der Urtheilskraft (Critique of Judgement) that the analogy of animal forms
implies a common original type, and thus a common parent.[10]
In 1795, Charles Darwin's grandfather, Erasmus Darwin, asked:
[W]ould it be too bold to imagine, that in the great length of time, since the earth began to exist, perhaps
millions of ages before the commencement of the history of mankind, would it be too bold to imagine,
that all warm-blooded animals have arisen from one living filament, which the great First Cause endued
with animality, with the power of acquiring new parts attended with new propensities, directed by
irritations, sensations, volitions, and associations; and thus possessing the faculty of continuing to
improve by its own inherent activity, and of delivering down those improvements by generation to its
posterity, world without end?[11]
In 1859, Charles Darwin's The Origin of Species was published. The views about common descent expressed therein
were that it was possible that there was only one progenitor for all life forms.
"Therefore I should infer from analogy that probably all the organic beings which have ever lived on this
earth have descended from some one primordial form, into which life was first breathed." [3] (p 484)
Darwin's famous closing sentence describes the "grandeur in this view of life, with its several powers, having been
originally breathed into a few forms or into one."[3] (p 490)
Common descent 180

Evidence of universal common descent

Common biochemistry and genetic code

All known forms of life are based on the same fundamental biochemical organisation: genetic information encoded
in DNA, transcribed into RNA, through the effect of protein- and RNA-enzymes, then translated into proteins by
(highly similar) ribosomes, with ATP, NADH and others as energy sources, etc. Furthermore, the genetic code (the
"translation table" according to which DNA information is translated into proteins) is nearly identical for all known
lifeforms, from bacteria to humans. The universality of this code is generally regarded by biologists as definitive
evidence in favor of the theory of universal common descent. Analysis of the small differences in the genetic code
has also provided support for universal common descent.[12] A statistical comparison of various alternative
hypotheses has shown that universal common ancestry is significantly more probable than models involving multiple
origins.[13]

Selectively neutral similarities

Similarities which have no adaptive relevance cannot be explained by convergent evolution, and therefore they
provide compelling support for the theory of universal common descent.
Such evidence has come from two areas: amino acid sequences and DNA sequences. Proteins with the same
three-dimensional structure need not have identical amino acid sequences; any irrelevant similarity between the
sequences is evidence for common descent. In certain cases, there are several codons (DNA triplets) that code for the
same amino acid. Thus, if two species use the same codon at the same place to specify an amino acid that can be
represented by more than one codon, that is evidence for a recent common ancestor.

Other similarities
The universality of many aspects of cellular life is often pointed to as supportive evidence to the more compelling
evidence listed above. These similarities include the energy carrier adenosine triphosphate (ATP), and the fact that
all amino acids found in proteins are left-handed. It is possible that these similarities resulted because of the laws of
physics and chemistry, rather than universal common descent and therefore resulted in convergent evolution.

Phylogenetic trees
Another important piece of evidence is
that it is possible to construct detailed
phylogenetic trees (that is, "genealogic
trees" of species) mapping out the
proposed divisions and common
ancestors of all living species. In 2010
an analysis of available genetic data,
mapping them to phylogenetic trees,
gave "firm quantitative support for the
unity of life. ...there is now strong
quantitative support, by a formal
test,[1] for the unity of life.[2]

Traditionally, these trees have been

built using morphological methods, A phylogenetic tree based on rRNA genes.
such as appearance, embryology, etc.
Common descent 181

Recently, it has been possible to construct these trees using molecular data, based on similarities and differences
between genetic and protein sequences. All these methods produce essentially similar results, even though that most
genetic variation has no influence over external morphology. That phylogenetic trees based on different types of
information agree with each other is strong evidence of a real underlying common descent.[14]

Illustrations of common descent

Artificial selection
Artificial selection demonstrates the diversity that can exist among organisms that share a relatively recent common
ancestor. In artificial selection, one species is bred selectively at each generation, allowing only those organisms that
exhibit desired characteristics to reproduce. These characteristics become increasingly well-developed in successive
generations. Artificial selection was successful long before science discovered the genetic basis.

Dog breeding

The diversity of domesticated dogs is an example of the power of

artificial selection. All breeds share common ancestry, having
descended from wolves. Humans selectively bred them to enhance
specific characteristics, such as color and length or body size. This
created a range of breeds that include the Chihuahua, Great Dane,
Basset Hound, Pug, and Poodle. Wild wolves, which did not undergo
artificial selection, are relatively uniform in comparison.

The Chihuahua mix and Great Dane illustrate the

range of sizes among dog breeds.

Wild cabbage

Early farmers cultivated many popular vegetables from the Brassica

oleracea (wild cabbage) by artificially selecting for certain attributes.
Common vegetables such as cabbage, kale, broccoli, cauliflower,
kohlrabi and Brussels sprouts are all descendants of the wild cabbage
plant.[15] Brussels sprouts were created by artificially selecting for
large bud size. Broccoli was bred by selecting for large flower stalks.
Cabbage was created by selecting for short petioles. Kale was bred by
selecting for large leaves.

Wild Cabbage plant

Common descent 182

Natural selection
Natural selection is the evolutionary process by which heritable traits
that increase an individual's fitness become more common, and
heritable traits that decrease an individual's fitness become less
common.

Darwin's finches

During Charles Darwin's studies on the Galápagos Islands, Darwin

observed 13 species of finches that are closely related and differ most
markedly in the shape of their beaks. The beak of each species is suited
to the food available in its particular environment, suggesting that beak
shapes evolved by natural selection. Large beaks were found on the
Darwin's finches
islands where the primary source of food for the finches is nuts and
therefore the large beaks allowed the birds to be better equipped for
opening the nuts and staying well nourished. Slender beaks were found on the finches which found insects to be the
best source of food on the island they inhabited; their slender beaks allowed the birds to be better equipped for
pulling out the insects from their tiny hiding places. The finch is also found on the main land and it is thought that
they migrated to the islands and began adapting to their environment through natural selection.

References
[1] Theobald, D.L., Nature 465, 219-222, (2010)
[2] Steel, M. & Penny, D., Nature 465,168 (2010)
[3] Darwin, C., "The Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle For Life", London,
John Murrary, (1859) p. 490
[4] Doolittle, W. Ford (February, 2000). Uprooting the tree of life (http:/ / shiva. msu. montana. edu/ courses/ mb437_537_2004_fall/ docs/
uprooting. pdf). Scientific American 282 (6): 90–95.
[5] Nicolas Glansdorff, Ying Xu & Bernard Labedan: The Last Universal Common Ancestor : emergence, constitution and genetic legacy of an
elusive forerunner. Biology Direct 2008, 3:29.
[6] Singham, Mano (October 13, 2006). "Looking for Deep Ancestors" (http:/ / machineslikeus. com/ articles/ LookingForDeep. html). Machines
Like Us. . Retrieved November 19, 2009.
[7] J. S. Bromley, The new Cambridge modern history: The rise of Great Britain and Russia, 1688-1715/25 (http:/ / books. google. com/
books?id=OOgzAAAAIAAJ& pg=PA62& dq=Maupertuis+ "for+ the+ first+ time"& cd=1#v=onepage& q=Maupertuis "for the first time"&
f=false), CUP Archive, 1970, ISBN 9780521075244, pgs. 62-63.
[8] Geoffrey Russell Richards Treasure, The making of modern Europe, 1648-1780 (http:/ / books. google. com/ books?id=C94OAAAAQAAJ&
pg=PA142& dq="blind+ destiny+ has+ produced"& cd=6#v=onepage& q="blind destiny has produced"& f=false), Taylor & Francis, 1985,
ISBN 9780416723700, pg. 142
[9] C. Leon Harris, Evolution, genesis and revelations, with readings from Empedocles to Wilson (http:/ / books. google. com/
books?id=Fkqg3TIkBJwC& pg=PA107& dq=Essai+ de+ Cosmologie+ "blind+ destiny"& cd=1#v=onepage& q=Essai de Cosmologie "blind
destiny"& f=false), SUNY Press, 1981, ISBN 9780873954877, pg. 107
[10] Immanuel Kant and Werner S. Pluhar, Critique of Judgment (http:/ / books. google. com/ books?id=y5wQD-ioaUUC& pg=PA304&
dq=Critique+ of+ Judgment+ "original+ mother"& cd=1#v=onepage& q=& f=false), Hackett Publishing, 1987, ISBN 9780872200258, p. 304:
"Despite all the variety among these forms, they seem to have been produced according to a common archetype, and this analogy among them
reinforces our suspicion that they are actually akin, produced by a common original mother."
[11] Darwin, Erasmus (1818) [1795]. "Generation" (http:/ / books. google. com/ ?id=XRUaAAAAMAAJ& printsec=frontcover& q=).
Zoonomia; or the Laws of Organic Life. 1 (4th American ed.). Philadelphia: Edward Earle. p. 397 [§ 39.4.8]. . Retrieved November 20, 2009.
[12] Knight, Robin, et al. (January 2001). "Rewiring the Keyboard: Evolvability of the Genetic Code". Nature Reviews Genetics 2 (1): 49–58.
doi:10.1038/35047500. PMID 11253070.
[13] Theobald, Douglas L. (13 May 2010). "A formal test of the theory of universal common ancestry.". Nature 465 (7295): 219–222.
doi:10.1038/nature09014. PMID 20463738.
[14] Theobald, Douglas (2004). "Prediction 1.3: Consilience of Independent Phylogenies" (http:/ / www. talkorigins. org/ faqs/ comdesc/
section1. html#independent_convergence). 29+ Evidences for Macroevolution. TalkOrigins Foundation. . Retrieved November 20, 2009.
Common descent 183

[15] Raven, Peter H., et al. (2005). Biology of Plants (7th rev. ed.). New York: W.H. Freeman. ISBN 0716762846. OCLC 183148564. "[These
vegetables were] all produced from a single species of plant (Brassica oleraca), a member of the mustard family."

External links
• 29+ Evidences for Macroevolution: the Scientific Case for Common Descent (http://www.talkorigins.org/faqs/
comdesc/). From the TalkOrigins Archive
• The Tree of Life Web Project (http://tolweb.org/tree/phylogeny.html)

Evidence of common descent

A large body of evidence of common descent of living things has been discovered by scientists working in a variety
of fields over many years. This evidence has demonstrated and verified the occurrence of evolution and provided a
wealth of information on the natural processes by which the variety and diversity of life on Earth developed. This
evidence supports the modern evolutionary synthesis, the current scientific theory that explains how and why life
changes over time. Evolutionary biologists document the fact of common descent: making testable predictions,
testing hypotheses, and developing theories that illustrate and describe its causes.
Comparison of the genetic sequence of organisms has revealed that organisms that are phylogenetically close have a
higher degree of sequence similarity than organisms that are phylogenetically distant. Further evidence for common
descent comes from genetic detritus such as pseudogenes, regions of DNA that are orthologous to a gene in a related
organism, but are no longer active and appear to be undergoing a steady process of degeneration.
Fossils are important for estimating when various lineages developed in geologic time. As fossilization is an
uncommon occurrence, usually requiring hard body parts and death near a site where sediments are being deposited,
the fossil record only provides sparse and intermittent information about the evolution of life. Evidence of organisms
prior to the development of hard body parts such as shells, bones and teeth is especially scarce, but exists in the form
of ancient microfossils, as well as impressions of various soft-bodied organisms. The comparative study of the
anatomy of groups of animals reveals structural features that are fundamentally similar or homologous, clearly
demonstrating phylogenetic and ancestral relationships with other organism, most especially when compared with
fossils of ancient extinct organisms. Vestigial structures and comparisons in embryonic development are largely a
contributing factor in anatomical resemblance in concordance with common descent. Since metabolic processes do
not leave fossils, research into the evolution of the basic cellular processes is done largely by comparison of existing
organisms’ physiology and biochemistry. Many lineages diverged at different stages of development, so it is possible
to determine when certain metabolic processes appeared by comparing the traits of the descendants of a common
ancestor. Universal biochemical organization and molecular variance patterns in all organisms also show a direct
correlation with common descent.
Further evidence comes from the field of biogeography because evolution with common descent provides the best
and most thorough explanation for a variety of facts concerning the geographical distribution of plants and animals
across the world. This is especially obvious in the field of island biogeography. Combined with the theory of plate
tectonics common descent provides a way to combine facts about the current distribution of species with evidence
from the fossil record to provide a logically consistent explanation of how the distribution of living organisms has
changed over time.
The development and spread of antibiotic resistant bacteria, like the spread of pesticide resistant forms of plants and
insects provides evidence that evolution due to natural selection is an ongoing process in the natural world.
Alongside this, are observed instances of the separation of populations of species into sets of new species
(speciation). Speciation has been observed directly and indirectly in the lab and in nature. Multiple forms of such
have been described and documented as examples for individual modes of speciation. Furthermore, evidence of
Evidence of common descent 184

common descent extends from direct laboratory and experimentation with the artificial selection of
organisms—historically and currently—and other controlled experiments involving many of the topics in the article.
This article explains the different types of evidence for evolution with common descent along with many specialized
examples of each.

Evidence from comparative physiology and biochemistry

Genetics
Although it has only recently become available, one of
the strongest evidences for common descent comes
from the study of gene sequences. Comparative
sequence analysis examines the relationship between
the DNA sequences of different species,[1] producing
several lines of evidence that confirm Darwin's original
hypothesis of common descent. If the hypothesis of
common descent is true, then species that share a
common ancestor will have inherited that ancestor's
DNA sequence. Notably they will have inherited
mutations unique to that ancestor. More closely-related
While on board HMS Beagle, Charles Darwin collected numerous
species will have a greater fraction of identical specimens, many new to science, which supported his later theory of
sequence and will have shared substitutions when evolution by natural selection.
compared to more distantly-related species.

The simplest and most powerful evidence is provided by phylogenetic reconstruction. Such reconstructions,
especially when done using slowly-evolving protein sequences, are often quite robust and can be used to reconstruct
a great deal of the evolutionary history of modern organisms (and even in some instances such as the recovered gene
sequences of mammoths, Neanderthals or T. rex, the evolutionary history of extinct organisms). These reconstructed
phylogenies recapitulate the relationships established through morphological and biochemical studies. The most
detailed reconstructions have been performed on the basis of the mitochondrial genomes shared by all eukaryotic
organisms, which are short and easy to sequence; the broadest reconstructions have been performed either using the
sequences of a few very ancient proteins or by using ribosomal RNA sequence.

This evidence does not support the rival hypothesis that genetic similarity of two species is the product of common
functional or structural requirements, and not common descent (for example, if there is one best way to produce a
hoof, all hoofed creatures will share a genetic basis even if they are not related). However, phylogenetic relationships
also extend to a wide variety of nonfunctional sequence elements, including repeats, transposons, pseudogenes, and
mutations in protein-coding sequences that do not result in changes in amino-acid sequence. While a minority of
these elements might later be found to harbor function, in aggregate they demonstrate that identity must be the
product of common descent rather than common function.

Universal biochemical organisation and molecular variance patterns

All known extant organisms are based on the same fundamental biochemical organisation: genetic information
encoded as nucleic acid (DNA, or RNA for viruses), transcribed into RNA, then translated into proteins (that is,
polymers of amino acids) by highly conserved ribosomes. Perhaps most tellingly, the Genetic Code (the "translation
table" between DNA and amino acids) is the same for almost every organism, meaning that a piece of DNA in a
bacterium codes for the same amino acid as in a human cell. ATP is used as energy currency by all extant life. A
deeper understanding of developmental biology shows that common morphology is, in fact, the product of shared
genetic elements. For example, although camera-like eyes are believed to have evolved independently on many
Evidence of common descent 185

separate occasions, they share a common set of light-sensing proteins (opsins), suggesting a common point of origin
for all sighted creatures.[2] Another noteworthy example is the familiar vertebrate body plan, whose structure is
controlled by the homeobox (Hox) family of genes.

DNA sequencing
Comparison of the DNA sequences allows organisms to be grouped by sequence similarity, and the resulting
phylogenetic trees are typically congruent with traditional taxonomy, and are often used to strengthen or correct
taxonomic classifications. Sequence comparison is considered a measure robust enough to be used to correct
erroneous assumptions in the phylogenetic tree in instances where other evidence is scarce. For example, neutral
human DNA sequences are approximately 1.2% divergent (based on substitutions) from those of their nearest
genetic relative, the chimpanzee, 1.6% from gorillas, and 6.6% from baboons.[3] Genetic sequence evidence thus
allows inference and quantification of genetic relatedness between humans and other apes.[4] [5] The sequence of the
16S ribosomal RNA gene, a vital gene encoding a part of the ribosome, was used to find the broad phylogenetic
relationships between all extant life. The analysis, originally done by Carl Woese, resulted in the three-domain
system, arguing for two major splits in the early evolution of life. The first split led to modern Bacteria and the
subsequent split led to modern Archaea and Eukaryotes.

Proteins
The proteomic evidence also supports the universal ancestry of life. Vital proteins, such as the ribosome, DNA
polymerase, and RNA polymerase, are found in everything from the most primitive bacteria to the most complex
mammals. The core part of the protein is conserved across all lineages of life, serving similar functions. Higher
organisms have evolved additional protein subunits, largely affecting the regulation and protein-protein interaction
of the core. Other overarching similarities between all lineages of extant organisms, such as DNA, RNA, amino
acids, and the lipid bilayer, give support to the theory of common descent. The chirality of DNA, RNA, and amino
acids is conserved across all known life. As there is no functional advantage to right- or left-handed molecular
chirality, the simplest hypothesis is that the choice was made randomly by early organisms and passed on to all
extant life through common descent. Further evidence for reconstructing ancestral lineages comes from junk DNA
such as pseudogenes, "dead" genes which steadily accumulate mutations.[6]

Pseudogenes
Pseudogenes also known, as Junk DNA, or dead DNA is the extra DNA that is in our genome but does not get
transcribed into RNA to produce protein. This is an example of a vestige since reproducing these genes uses energy
and is a waste, yet 99% of our genome is these (1% working DNA).[7] The way a pseudogene is produced is a gene
that is no longer used will accumulate mutations that make it non-functional but since it is not used; when it
disappears, it does not affect fitness.

Other mechanisms
There is also a large body of molecular evidence for a number of different mechanisms for large evolutionary
changes, among them: genome and gene duplication, which facilitates rapid evolution by providing substantial
quantities of genetic material under weak or no selective constraints; horizontal gene transfer, the process of
transferring genetic material to another cell that is not an organism's offspring, allowing for species to acquire
beneficial genes from each other; and recombination, capable of reassorting large numbers of different alleles and of
establishing reproductive isolation. The Endosymbiotic theory explains the origin of mitochondria and plastids (e.g.
chloroplasts), which are organelles of eukaryotic cells, as the incorporation of an ancient prokaryotic cell into ancient
eukaryotic cell. Rather than evolving eukaryotic organelles slowly, this theory offers a mechanism for a sudden
evolutionary leap by incorporating the genetic material and biochemical composition of a separate species. Evidence
supporting this mechanism has recently been found in the protist Hatena: as a predator it engulfs a green algae cell,
Evidence of common descent 186

which subsequently behaves as an endosymbiont, nourishing Hatena, which in turn loses its feeding apparatus and
behaves as an autotroph.[8] [9]
Since metabolic processes do not leave fossils, research into the evolution of the basic cellular processes is done
largely by comparison of existing organisms. Many lineages diverged when new metabolic processes appeared, and
it is theoretically possible to determine when certain metabolic processes appeared by comparing the traits of the
descendants of a common ancestor or by detecting their physical manifestations. As an example, the appearance of
oxygen in the earth's atmosphere is linked to the evolution of photosynthesis.

Specific examples

Chromosome 2 in humans

Clear evidence for the evolution of Homo sapiens from a

common ancestor with chimpanzees is the number of
chromosomes in human as compared to all other members of
Hominidae. All Hominidae with the exception of humans
have 24 pairs of chromosomes. Humans have only 23 pairs.
Human chromosome 2 is widely accepted to be a result of an
end-to-end fusion of two ancestral chromosomes.[10] [11]

The evidence for this includes:

• The correspondence of chromosome 2 to two ape
chromosomes. The closest human relative, the common Fusion of ancestral chromosomes left distinctive remnants of
telomeres, and a vestigial centromere
chimpanzee, has near-identical DNA sequences to human
chromosome 2, but they are found in two separate
chromosomes. The same is true of the more distant gorilla and orangutan.[12] [13]
• The presence of a vestigial centromere. Normally a chromosome has just one centromere, but in chromosome 2
there are remnants of a second centromere.[14]
• The presence of vestigial telomeres. These are normally found only at the ends of a chromosome, but in
chromosome 2 there are additional telomere sequences in the middle.[15]
Chromosome 2 thus presents very strong evidence in favour of the common descent of humans and other apes.
According to researcher J. W. IJdo, "We conclude that the locus cloned in cosmids c8.1 and c29B is the relic of an
ancient telomere-telomere fusion and marks the point at which two ancestral ape chromosomes fused to give rise to
human chromosome 2."[15]

Cytochrome c
A classic example of biochemical evidence for evolution is the variance of the ubiquitous (i.e. all living organisms
have it, because it performs very basic life functions) protein Cytochrome c in living cells. The variance of
cytochrome c of different organisms is measured in the number of differing amino acids, each differing amino acid
being a result of a base pair substitution, a mutation. If each differing amino acid is assumed to be the result of one
base pair substitution, it can be calculated how long ago the two species diverged by multiplying the number of base
pair substitutions by the estimated time it takes for a substituted base pair of the cytochrome c gene to be
successfully passed on. For example, if the average time it takes for a base pair of the cytochrome c gene to mutate is
N years, the number of amino acids making up the cytochrome c protein in monkeys differ by one from that of
humans, this leads to the conclusion that the two species diverged N years ago.
The primary structure of cytochrome c consists of a chain of about 100 amino acids. Many higher order organisms
possess a chain of 104 amino acids.[16]
Evidence of common descent 187

The cytochrome c molecule has been extensively studied for the glimpse it gives into evolutionary biology. Both
chicken and turkeys have identical sequence homology (amino acid for amino acid), as do pigs, cows and sheep.
Both humans and chimpanzees share the identical molecule, while rhesus monkeys share all but one of the amino
acids:[17] the 66th amino acid is isoleucine in the former and threonine in the latter.[16]
What makes these homologous similarities particularly suggestive of common ancestry in the case of cytochrome C,
in addition to the fact that the phylogenies derived from them match other phylogenies very well, is the high degree
of functional redundancy of the cytochrome C molecule. The different existing configurations of amino acids do not
significantly affect the functionality of the protein, which indicates that the base pair substitutions are not part of a
directed design, but the result of random mutations that aren't subject to selection.[18]

Out of Africa hypothesis of human evolution

Mathematical models of evolution, pioneered by the likes of Sewall Wright, Ronald Fisher and J. B. S. Haldane and
extended via diffusion theory by Motoo Kimura, allow predictions about the genetic structure of evolving
populations. Direct examination of the genetic structure of modern populations via DNA sequencing has recently
allowed verification of many of these predictions. For example, the Out of Africa theory of human origins, which
states that modern humans developed in Africa and a small sub-population migrated out (undergoing a population
bottleneck), implies that modern populations should show the signatures of this migration pattern. Specifically,
post-bottleneck populations (Europeans and Asians) should show lower overall genetic diversity and a more uniform
distribution of allele frequencies compared to the African population. Both of these predictions are borne out by
actual data from a number of studies.[19]

Evidence from comparative anatomy

Comparative study of the anatomy of groups of animals or plants reveals that certain structural features are basically
similar. For example, the basic structure of all flowers consists of sepals, petals, stigma, style and ovary; yet the size,
colour, number of parts and specific structure are different for each individual species.

Nested hierarchies and classification

Taxonomy is based on the fact that all organisms are related to each other in nested hierarchies based on shared
characteristics. Most existing species can be organized rather easily in a nested hierarchical classification. This is
evident from the Linnaean classification scheme. Based on shared derived characters, closely related organisms can
be placed in one group (such as a genus), several genera can be grouped together into one family, several families
can be grouped together into an order, etc.[20] The existence of these nested hierarchies was recognized by many
biologists before Darwin, but he showed that his theory of evolution with its branching pattern of common descent
could explain them.[20] [21] Darwin described how common descent could provide a logical basis for
classification:[22]

“
All the foregoing rules and aids and difficulties in classification are explained, if I do not greatly deceive myself, on the view that the natural
system is founded on descent with modification; that the characters which naturalists consider as showing true affinity between any two or

”
more species, are those which have been inherited from a common parent, and, in so far, all true classification is genealogical; that community
of descent is the hidden bond which naturalists have been unconsciously seeking, ...

—Charles Darwin, On the Origin of Species, page 577

Evidence of common descent 188

Homologous structures and divergent (adaptive) evolution

If widely separated groups of organisms are originated from a common ancestry, they are expected to have certain
basic features in common. The degree of resemblance between two organisms should indicate how closely related
they are in evolution:
• Groups with little in common are assumed to have diverged from a common ancestor much earlier in geological
history than groups which have a lot in common;
• In deciding how closely related two animals are, a comparative anatomist looks for structures that are
fundamentally similar, even though they may serve different functions in the adult. Such structures are described
as homologous and suggest a common origin.
• In cases where the similar structures serve different functions in adults, it may be necessary to trace their origin
and embryonic development. A similar developmental origin suggests they are the same structure, and thus likely
to be derived from a common ancestor.
When a group of organisms share a homologous structure which is specialized to perform a variety of functions in
order to adapt different environmental conditions and modes of life are called adaptive radiation. The gradual
spreading of organisms with adaptive radiation is known as divergent evolution.

Vestigial structures
A strong and direct evidence for common descent comes from vestigial structures.[23] Rudimentary body parts, those
that are smaller and simpler in structure than corresponding parts in the ancestral species, are called vestigial organs.
They are usually degenerated or underdeveloped. The existence of vestigial organs can be explained in terms of
changes in the environment or modes of life of the species. Those organs are thought to be functional in the ancestral
species but are now either nonfunctional or repurposed. Examples are the pelvic girdles of whales, haltere (hind
wings) of flies and mosquitos, wings of flightless birds such as ostriches, and the leaves of some xerophytes (e.g.
cactus) and parasitic plants (e.g. dodder). It must be noted, however, that vestigial structures may have had their
original function replaced with another. For example the halteres in dipterists help balance the insect while in flight
and the wings of ostriches are used in mating rituals.

“
The most reasonable conclusion to draw is that these creatures descended from creatures in which these parts were functional, which in turn
indicates that most (or indeed all) creatures descended from common ancenstors.

”
—Natan Slifkin, The Challenge of Creation, page 262

Evolutionary developmental biology and embryonic development

Evolutionary developmental biology is the biological field that compares the developmental process of different
organisms to determine ancestral relationships between species. A large variety of organism’s genomes contain a
small fraction of genes that control the organisms development. Hox genes are an example of these types of nearly
universal genes in organisms pointing to an origin of common ancestry. Embryological evidence stems from the
development of organisms at the embryological level with the comparison of different organisms embryos similarity.
Remains of ancestral traits often appear and disappear in different stages of the embryological development process.
Examples such as hair growth and loss (lanugo) during human development;[24] the appearance of transitions from
fish to amphibians to reptiles and then to mammals in all mammal embryos; development and degeneration of a yolk
sac; terrestrial frogs and salamanders passing through the larval stage within the egg—with features of typically
aquatic larvae—but hatch ready for life on land;[25] and the appearance of gill-like structures (pharyngeal arch) in
vertebrate embryo development including. Note that in fish the arches become gills while in humans for example,
become the pharynx.
Evidence of common descent 189

Atavisms
An atavism is an evolutionary throwback, such as traits reappearing which had disappeared generations ago.[26]
Atavisms occur because genes for previously existing phenotypical features are often preserved in DNA, even
though the genes are not expressed in some or most of the organisms possessing them.[27] Some examples of this are
hind-legged snakes or whales;[26] [28] [29] the extra toes of ungulates that do not even reach the ground,[30] chicken's
teeth,[31] reemergence of sexual reproduction in Hieracium pilosella and Crotoniidae;[32] and humans with tails,[26]
extra nipples,[28] and large canine teeth.[28]

Specific examples

Figure 5a: The principle of homology illustrated by the adaptive radiation of the forelimb of mammals. All conform
to the basic pentadactyl pattern but are modified for different usages. The third metacarpal is shaded throughout; the
shoulder is crossed-hatched.
Evidence of common descent 190

Figure 5b: Illustration of the Eoraptor lunensis pelvis of the saurischian order and the Lesothosaurus diagnosticus
pelvis of the ornithischian order in the Dinosauria superorder. The parts of the pelvis show modification over time.
The cladogram is shown to illustrate the distance of divergence between the two species.

Figure 5c: Adaptation of insect mouthparts: a, antennae; c, compound eye; lb, labrium; lr, labrum; md, mandibles;
mx, maxillae.

Pentadactyl limb
The pattern of limb bones called pentadactyl limb is an example of homologous structures (Fig. 5a). It is found in all
classes of tetrapods (i.e. from amphibians to mammals). It can even be traced back to the fins of certain fossil fishes
from which the first amphibians are thought to have evolved such as tiktaalik. The limb has a single proximal bone
(humerus), two distal bones (radius and ulna), a series of carpals (wrist bones), followed by five series of
metacarpals (palm bones) and phalanges (digits). Throughout the tetrapods, the fundamental structures of
pentadactyl limbs are the same, indicating that they originated from a common ancestor. But in the course of
evolution, these fundamental structures have been modified. They have become superficially different and unrelated
structures to serve different functions in adaptation to different environments and modes of life. This phenomenon is
clearly shown in the forelimbs of mammals. For example:
• In the monkey, the forelimbs are much elongated to form a grasping hand for climbing and swinging among trees.
• In the pig, the first digit is lost, and the second and fifth digits are reduced. The remaining two digits are longer
and stouter than the rest and bear a hoof for supporting the body.
• In the horse, the forelimbs are adapted for support and running by great elongation of the third digit bearing a
hoof.
• The mole has a pair of short, spade-like forelimbs for burrowing.
• The anteater uses its enlarged third digit for tearing down ant hills and termite nests.
• In the whale, the forelimbs become flippers for steering and maintaining equilibrium during swimming.
• In the bat, the forelimbs have turned into wings for flying by great elongation of four digits, while the hook-like
first digit remains free for hanging from trees.
Evidence of common descent 191

Pelvic structure of dinosaurs

Similar to the pentadactyl limb in mammals, the earliest dinosaurs split into two distinct orders—the saurischia and
ornithischia. They are classified as one or the other in accordance with what the fossils show. In Figure 5b, it is clear
that early saurischians resembled early ornithischians. The pattern of the pelvis in all species of dinosaurs is an
example of homologous structures. Each order of dinosaur has slightly differing pelvis bones providing evidence of
common descent. Additionally, modern birds show a similarity to ancient saurischian pelvic structures therefore
indicating the evolution of birds from dinosaurs.

Insect mouthparts
The basic structures are the same, including a labrum (upper lip), a pair of mandibles, a hypopharynx (floor of
mouth), a pair of maxillae, and a labium. These structures are enlarged and modified; others are reduced and lost.
The modifications enable the insects to exploit a variety of food materials (Fig. 5c):
(A) Primitive state — biting and chewing: e.g. grasshopper. Strong mandibles and maxillae for manipulating food.
(B) Ticking and biting: e.g. honey bee. Labium long to lap up nectar; mandibles chew pollen and mould wax. (C)
Sucking: e.g. butterfly. Labrum reduced; mandibles lost; maxillae long forming sucking tube. (D) Piercing and
sucking, e.g.. female mosquito. Labrum and maxillae form tube; mandibles form piercing stylets; labrum grooved to
hold other parts.

Other arthropod appendages

Insect mouthparts and antennae are considered homologues of insect legs. Parallel developments are seen in some
arachnids: The anterior pair of legs may be modified as analogues of antennae, particularly in whip scorpions, which
walk on six legs. These developments provide support for the theory that complex modifications often arise by
duplication of components, with the duplicates modified in different directions.

Recurrent laryngeal nerve in giraffes

The recurrent laryngeal nerve is a

fourth branch of the vagus nerve,
which is a cranial nerve. In mammals
its path is extraordinary: as a part of
the vagus nerve, it comes from the
brain, passes through the neck down to
heart, rounds the dorsal aorta and
returns up to the larynx, again through
the neck.

This path looks not too optimal even

for human, but for giraffes it becomes
quite suboptimal. Due to the lengths of
their necks, the recurrent laryngeal
The path of the recurrent laryngeal nerve in giraffes. The laryngeal nerve is compensated nerve may be up to 4m long (13 ft),
for by subsequent tinkering from natural selection. despite its optimal route being a
distance of just several inches.
Its route is explained by the evolution of mammals from fishes, which had no neck. Therefore the nerve's route was
quite reasonable: it was a relatively short nerve that innervated one gill slit, and passed near the gill arch. Since then
gills have evolved and the gill arch has become a dorsal aorta.[33] [34]
Evidence of common descent 192

Route of the vas deferens

Similar to the laryngeal nerve in giraffes, the vas deferens is part

of the male anatomy of many vertebrates; it transports sperm from
the epididymis in anticipation of ejaculation. In humans, the vas
deferens routes up from the testicle, looping over the ureter, and
back down to the urethra and penis. It has been suggested that this
is due to the descent of the testicles during the course of human
evolution—likely associated with temperature. As the testicles
descended, the vas deferens lengthened to accommodate the
accidental “hook” over the ureter.[34] [35]

Route of the vas deferens from the testis to the penis

Evidence from paleontology

When organisms die, they often decompose rapidly or are consumed by
scavengers, leaving no permanent evidences of their existence.
However, occasionally, some organisms are preserved. The remains or
traces of organisms from a past geologic age embedded in rocks by
natural processes are called fossils. They are extremely important for
understanding the evolutionary history of life on Earth, as they provide
direct evidence of evolution and detailed information on the ancestry of
organisms. Paleontology is the study of past life based on fossil records
and their relations to different geologic time periods.

For fossilization to take place, the traces and remains of organisms must
be quickly buried so that weathering and decomposition do not occur.
Skeletal structures or other hard parts of the organisms are the most
commonly occurring form of fossilized remains (Paul, 1998),
(Behrensmeyer, 1980) and (Martin, 1999). There are also some trace
"fossils" showing moulds, cast or imprints of some previous organisms.
An insect trapped in amber.
As an animal dies, the organic materials gradually decay, such that the
bones become porous. If the animal is subsequently buried in mud, mineral salts will infiltrate into the bones and
gradually fill up the pores. The bones will harden into stones and be preserved as fossils. This process is known as
petrification. If dead animals are covered by wind-blown sand, and if the sand is subsequently turned into mud by
heavy rain or floods, the same process of mineral infiltration may occur. Apart from petrification, the dead bodies of
organisms may be well preserved in ice, in hardened resin of coniferous trees (amber), in tar, or in anaerobic, acidic
peat. Fossilization can sometimes be a trace, an impression of a form. Examples include leaves and footprints, the
Evidence of common descent 193

fossils of which are made in layers that then harden.

Fossil record
It is possible to find out how a particular group of organisms evolved by
arranging its fossil records in a chronological sequence. Such a
sequence can be determined because fossils are mainly found in
sedimentary rock. Sedimentary rock is formed by layers of silt or mud
on top of each other; thus, the resulting rock contains a series of
horizontal layers, or strata. Each layer contains fossils which are typical
for a specific time period during which they were made. The lowest
strata contain the oldest rock and the earliest fossils, while the highest
strata contain the youngest rock and more recent fossils.

A succession of animals and plants can also be seen from fossil records.
By studying the number and complexity of different fossils at different
stratigraphic levels, it has been shown that older fossil-bearing rocks
contain fewer types of fossilized organisms, and they all have a simpler
Fossil trilobite. Trilobites were hard-shelled
arthropods, related to living horseshoe crabs and
structure, whereas younger rocks contain a greater variety of fossils,
spiders, that first appeared in significant often with increasingly complex structures.
numbers around 540 mya, dying out 250 mya.
In the past, geologists could only roughly estimate the ages of various
strata and the fossils found. They did so, for instance, by estimating the
time for the formation of sedimentary rock layer by layer. Today, by measuring the proportions of radioactive and
stable elements in a given rock, the ages of fossils can be more precisely dated by scientists. This technique is known
as radiometric dating.
Throughout the fossil record, many species that appear at an early stratigraphic level disappear at a later level. This is
interpreted in evolutionary terms as indicating the times at which species originated and became extinct.
Geographical regions and climatic conditions have varied throughout the Earth's history. Since organisms are
adapted to particular environments, the constantly changing conditions favoured species which adapted to new
environments through the mechanism of natural selection.

Extent of the fossil record

Charles Darwin collected fossils in South America, and found fragments of armor which he thought were like giant
versions of the scales on the modern armadillos living nearby. The anatomist Richard Owen showed him that the
fragments were from gigantic extinct glyptodons, related to the armadillos. This was one of the patterns of
distribution that helped Darwin to develop his theory.[36]
Evidence of common descent 194

Despite the relative rarity of suitable conditions for fossilization,

approximately 250,000 fossil species are known.[37] The number
of individual fossils this represents varies greatly from species to
species, but many millions of fossils have been recovered: for
instance, more than three million fossils from the last Ice Age have
been recovered from the La Brea Tar Pits in Los Angeles.[38]
Many more fossils are still in the ground, in various geological Cynognathus, a Eucynodont, one of a grouping of
formations known to contain a high fossil density, allowing Therapsids ("mammal-like reptiles") that is ancestral to
estimates of the total fossil content of the formation to be made. all modern mammals.

An example of this occurs in South Africa's Beaufort Formation

(part of the Karoo Supergroup, which covers most of South Africa), which is rich in vertebrate fossils, including
therapsids (reptile/mammal transitional forms).[39] It has been estimated that this formation contains 800 billion
vertebrate fossils.[40]

Limitations
The fossil record is an important source for scientists when tracing the evolutionary history of organisms. However,
because of limitations inherent in the record, there are not fine scales of intermediate forms between related groups
of species. This lack of continuous fossils in the record is a major limitation in tracing the descent of biological
groups. Furthermore, there are also much larger gaps between major evolutionary lineages. When transitional fossils
are found that show intermediate forms in what had previously been a gap in knowledge, they are often popularly
referred to as "missing links".
There is a gap of about 100 million years between the beginning of the Cambrian period and the end of the
Ordovician period. The early Cambrian period was the period from which numerous fossils of sponges, cnidarians
(e.g., jellyfish), echinoderms (e.g., eocrinoids), molluscs (e.g., snails) and arthropods (e.g., trilobites) are found. The
first animal that possessed the typical features of vertebrates, the Arandaspis, was dated to have existed in the later
Ordovician period. Thus few, if any, fossils of an intermediate type between invertebrates and vertebrates have been
found, although likely candidates include the Burgess Shale animal, Pikaia gracilens, and its Maotianshan shales
relatives, Myllokunmingia, Yunnanozoon, Haikouella lanceolata, and Haikouichthys.
Some of the reasons for the incompleteness of fossil records are:
• In general, the probability that an organism becomes fossilized is very low;
• Some species or groups are less likely to become fossils because they are soft-bodied;
• Some species or groups are less likely to become fossils because they live (and die) in conditions that are not
favourable for fossilization;
• Many fossils have been destroyed through erosion and tectonic movements;
• Most fossils are fragmentary;
• Some evolutionary change occurs in populations at the limits of a species' ecological range, and as these
populations are likely to be small, the probability of fossilization is lower (see punctuated equilibrium);
• Similarly, when environmental conditions change, the population of a species is likely to be greatly reduced, such
that any evolutionary change induced by these new conditions is less likely to be fossilized;
• Most fossils convey information about external form, but little about how the organism functioned;
• Using present-day biodiversity as a guide, this suggests that the fossils unearthed represent only a small fraction
of the large number of species of organisms that lived in the past.
Evidence of common descent 195

Specific examples

Evolution of the horse

Due to an almost-complete fossil record

found in North American sedimentary
deposits from the early Eocene to the
present, the horse provides one of the best
examples of evolutionary history
(phylogeny).

This evolutionary sequence starts with a

small animal called Hyracotherium
(commonly referred to as Eohippus) which
lived in North America about 54 million
years ago, then spread across to Europe and
Asia. Fossil remains of Hyracotherium
show it to have differed from the modern
horse in three important respects: it was a
small animal (the size of a fox), lightly built
and adapted for running; the limbs were
short and slender, and the feet elongated so
that the digits were almost vertical, with
four digits in the forelimbs and three digits
in the hindlimbs; and the incisors were
small, the molars having low crowns with
rounded cusps covered in enamel.
Evolution of the horse showing reconstruction of the fossil species obtained from
The probable course of development of successive rock strata. The foot diagrams are all front views of the left forefoot. The
horses from Hyracotherium to Equus (the third metacarpal is shaded throughout. The teeth are shown in longitudinal section.
modern horse) involved at least 12 genera
and several hundred species. The major trends seen in the development of the horse to changing environmental
conditions may be summarized as follows:
• Increase in size (from 0.4 m to 1.5 m — from 15in to 60in);
• Lengthening of limbs and feet;
• Reduction of lateral digits;
• Increase in length and thickness of the third digit;
• Increase in width of incisors;
• Replacement of premolars by molars; and
• Increases in tooth length, crown height of molars.
Fossilized plants found in different strata show that the marshy, wooded country in which Hyracotherium lived
became gradually drier. Survival now depended on the head being in an elevated position for gaining a good view of
the surrounding countryside, and on a high turn of speed for escape from predators, hence the increase in size and the
replacement of the splayed-out foot by the hoofed foot. The drier, harder ground would make the original
splayed-out foot unnecessary for support. The changes in the teeth can be explained by assuming that the diet
changed from soft vegetation to grass. A dominant genus from each geological period has been selected to show the
slow alteration of the horse lineage from its ancestral to its modern form.
Evidence of common descent 196

Evidence from geographical distribution

Data about the presence or absence of species on various continents and islands (biogeography) can provide evidence
of common descent and shed light on patterns of speciation.

Continental distribution
All organisms are adapted to their environment to a greater or lesser extent. If the abiotic and biotic factors within a
habitat are capable of supporting a particular species in one geographic area, then one might assume that the same
species would be found in a similar habitat in a similar geographic area, e.g. in Africa and South America. This is not
the case. Plant and animal species are discontinuously distributed throughout the world:
• Africa has Old World monkeys, apes, elephants, leopards, giraffes, and hornbills.
• South America has New World monkeys, cougars, jaguars, sloths, llamas, and toucans.
• Deserts in North and South America have native cacti, but deserts in Africa, Asia, and Australia have succulent
native euphorbs that resemble cacti but are very different, even though in some cases cacti have done very well
(for example in Australian deserts) when introduced by humans.[41]
Even greater differences can be found if Australia is taken into consideration, though it occupies the same latitude as
much of South America and Africa. Marsupials like kangaroos, bandicoots, and quolls make up about half of
Australia's indigenous mammal species.[42] By contrast, marsupials are today totally absent from Africa and form a
smaller portion of the mammalian fauna of South America, where opossums, shrew opossums, and the monito del
monte occur. The echidnas and platypus, the only living representatives of primitive egg-laying mammals
(monotremes), can be found only in Australia and are totally absent in the rest of the world. On the other hand,
Australia is missing many groups of placental mammals that are common on other continents (carnivorans,
artiodactyls, shrews, squirrels, lagomorphs), although it does have indigenous bats and murine rodents; many other
placentals, such as rabbits and foxes, have been introduced there by humans.
Other animal distribution examples include bears, located on all continents excluding Africa and Australia, and the
polar bear only located nearest to the North Pole. Penguins are located only around the South Pole despite similar
weather conditions at the North Pole. Families of sirenians are distributed exclusively around the earth’s waters,
where manatees are located in western Africa waters, northern South American waters, and West Indian waters only
while the related family, the Dugongs, are located only in Oceanic waters north of Australia, and the coasts
surrounding the Indian Ocean.
The same kinds of fossils are found from areas known to be adjacent to one another in the past but which, through
the process of continental drift, are now in widely divergent geographic locations. For example, fossils of the same
types of ancient amphibians, arthropods and ferns are found in South America, Africa, India, Australia and
Antarctica, which can be dated to the Paleozoic Era, at which time these regions were united as a single landmass
called Gondwana.[43] Sometimes the descendants of these organisms can be identified and show unmistakable
similarity to each other, even though they now inhabit very different regions and climates.
Evidence of common descent 197

Island biogeography

Types of species found on islands

Evidence from island biogeography has played an important and

historic role in the development of evolutionary biology. For
purposes of biogeography, islands are divided into two classes.
Continental islands are islands like Great Britain, and Japan that
have at one time or another been part of a continent. Oceanic
islands, like the Hawaiian islands, the Galapagos islands and St.
Helena, on the other hand are islands that have formed in the
ocean and never been part of any continent. Oceanic islands have
distributions of native plants and animals that are unbalanced in
ways that make them distinct from the biotas found on continents
or continental islands. Oceanic islands do not have native
Four of the 13 finch species found on the Galápagos
terrestrial mammals (they do sometimes have bats and seals), Archipelago, are thought to have evolved by an
amphibians, or fresh water fish. In some cases they have terrestrial adaptive radiation that diversified their beak shapes to
reptiles (such as the iguanas and giant tortoises of the Galapagos adapt them to different food sources.

islands) but often (for example Hawaii) they do not. This despite
the fact that when species such as rats, goats, pigs, cats, mice, and cane toads, are introduced to such islands by
humans they often thrive. Starting with Charles Darwin, many scientists have conducted experiments and made
observations that have shown that the types of animals and plants found, and not found, on such islands are
consistent with the theory that these islands were colonized accidentally by plants and animals that were able to
reach them. Such accidental colonization could occur by air, such as plant seeds carried by migratory birds, or bats
and insects being blown out over the sea by the wind, or by floating from a continent or other island by sea, as for
example by some kinds of plant seeds like coconuts that can survive immersion in salt water, and reptiles that can
survive for extended periods on rafts of vegetation carried to sea by storms.[]

Endemism
Many of the species found on remote islands are endemic to a particular island or group of islands, meaning they are
found nowhere else on earth. Examples of species endemic to islands include many flightless birds of New Zealand,
lemurs of Madagascar, the Komodo dragon of Komodo ,[44] the Dragon’s blood tree of Socotra ,[45] Tuatara of New
Zealand,[46] [47] and others. However many such endemic species are related to species found on other nearby islands
or continents; the relationship of the animals found on the Galapagos Islands to those found in South America is a
well-known example.[] All of these facts, the types of plants and animals found on oceanic islands, the large number
of endemic species found on oceanic islands, and the relationship of such species to those living on the nearest
continents, are most easily explained if the islands were colonized by species from nearby continents that evolved
into the endemic species now found there.[48]
Other types of endemism do not have to include, in the strict sense, islands. Islands can mean isolated lakes or
remote and isolated areas. Examples of these would include the highlands of Ethiopia, Lake Baikal, Fynbos of South
Africa, forests of New Caledonia, and others. Examples of endemic organisms living in isolated areas include the
Kagu of New Caledonia,[49] cloud rats of the Luzon tropical pine forests of the Philippines,[50] [51] the boojum tree
(Fouquieria columnaris) of the Baja California peninsula,[52] the Baikal Seal[53] and the omul of Lake Baikal.
Evidence of common descent 198

Adaptive radiations
Oceanic islands are frequently inhabited by clusters of closely related species that fill a variety of ecological niches,
often niches that are filled by very different species on continents. Such clusters, like the Finches of the Galapagos,
Hawaiian honeycreepers, members of the sunflower family on the Juan Fernandez Archipelago and wood weevils on
St. Helena are called adaptive radiations because they are best explained by a single species colonizing an island (or
group of islands) and then diversifying to fill available ecological niches. Such radiations can be spectacular; 800
species of the fruit fly family Drosophila, nearly half the world's total, are endemic to the Hawaiian islands. Another
illustrative example from Hawaii is the Silversword alliance, which is a group of thirty species found only on those
islands. Members range from the Silverswords that flower spectacularly on high volcanic slopes to trees, shrubs,
vines and mats that occur at various elevations from mountain top to sea level, and in Hawaiian habitats that vary
from deserts to rainforests. Their closest relatives outside Hawaii, based on molecular studies, are tarweeds found on
the west coast of North America. Interestingly, these tarweeds have sticky seeds that facilitate distribution by
migrant birds. Continental islands have less distinct biota, but those that have been long separated from any continent
also have endemic species and adaptive radiations, such as the 75 lemur species of Madagascar, and the eleven
extinct moa species of New Zealand.[] [54]

Ring Species
In biology, a ring species is a connected series of neighboring populations that can interbreed with relatively closely
related populations, but for which there exist at least two "end" populations in the series that are too distantly related
to interbreed. Often such non-breeding-though-genetically-connected populations co-exist in the same region thus
creating a "ring". Ring species provide important evidence of evolution in that they illustrate what happens over time
as populations genetically diverge, and are special because they represent in living populations what normally
happens over time between long deceased ancestor populations and living populations. If any of the populations
intermediate between the two ends of the ring were gone they would not be a continuous line of reproduction and
each side would be a different species.[55] [56]

Specific examples

Figure 6a: A dymaxion map of the world showing the distribution of present species of camelid. The solid black
lines indicate migration routes and the blue represents current camel locations.
Evidence of common descent 199

Figure 6b: Current distribution of Glossopteris placed on a Permian map showing the connection of the continents.
(1, South America; 2, Africa; 3, Madagascar; 4, India; 5, Antarctica; and 6, Australia)

Figure 6c: Present day distribution of marsupials. (Distribution shown in blue. Introduced areas shown in green.)

Migration, isolation, and distribution of the Camel

The history of the camel provides an example of how fossil evidence can be used to reconstruct migration and
subsequent evolution. The fossil record indicates that the evolution of camelids started in North America (see figure
6a), from which 6 million years ago they migrated across the Bering Strait into Asia and then to Africa, and 3.5
million years ago through the Isthmus of Panama into South America. Once isolated, they evolved along their own
lines, giving rise to the Bactrian camel and Dromedary in Asia and Africa and the llama and its relatives in South
America. Camelids then went extinct in North America at the end of the last ice age.[57]

Distribution of Glossopteris
The combination of continental drift and evolution can sometimes be used to make predictions about what will be
found in the fossil record. Glossopteris is an extinct species of seed fern plants from the Permian. Glossopteris
appears in the fossil record around the beginning of the Permian on the ancient continent of Gondwana. Continental
drift explains the current biogeography of the tree. Present day Glossopteris fossils are found in Permian strata in
southeast South America, southeast Africa, all of Madagascar, northern India, all of Australia, all of New Zealand,
and scattered on the southern and northern edges of Antarctica. During the Permian, these continents were connected
as Gondwana (see figure 6b) in agreement with magnetic striping, other fossil distributions, and glacial scratches
pointing away from the temperate climate of the South Pole during the Permian.[48]
Evidence of common descent 200

Distribution of marsupials
The history of marsupials also provides an example of how the theories of evolution and continental drift can be
combined to make predictions about what will be found in the fossil record. The earliest marsupial fossils are about
80 million years old and found in North America; by 40 million years ago fossils show that they could be found
throughout South America, but there is no evidence of them in Australia, where they now predominate, until about
30 million years ago. The theory of evolution predicts that the Australian marsupials must be descended from the
older ones found in the Americas. The theory of continental drift says that between 30 and 40 million years ago
South America and Australia were still part of the Southern hemisphere super continent of Gondwana and that they
were connected by land that is now part of Antarctica. Therefore combining the two theories scientists predicted that
marsupials migrated from what is now South America across what is now Antarctica to what is now Australia
between 40 and 30 million years ago. This hypothesis led paleontologists to Antarctica to look for marsupial fossils
of the appropriate age. After years of searching they found, starting in 1982, fossils on Seymour Island off the coast
of the Antarctic Peninsula of more than a dozen marsupial species that lived 35-40 million years ago.[41]

Evidence from observed natural selection

Examples for the evidence for evolution often stems from direct observation of natural selection in the field and the
laboratory. Scientists have observed and documented a multitude of events where natural selection is in action. The
most well known examples are antibiotic resistance in the medical field along with better-known laboratory
experiments documenting evolution's occurrence. Natural selection is tantamount to common descent in the fact that
long-term occurrence and selection pressures can lead to the diversity of life on earth as found today. All
adaptations—documented and undocumented changes concerned—are caused by natural selection and genetic drift.
The examples below are only a small fraction of the actual experiments and observations.

Specific examples of natural selection in the lab and in the field

Antibiotic and pesticide resistance

The development and spread of antibiotic resistant bacteria, like the spread of pesticide resistant forms of plants and
insects is evidence for evolution of species, and of change within species. Thus the appearance of vancomycin
resistant Staphylococcus aureus, and the danger it poses to hospital patients is a direct result of evolution through
natural selection. The rise of Shigella strains resistant to the synthetic antibiotic class of sulfonamides also
demonstrates the generation of new information as an evolutionary process.[58] Similarly, the appearance of DDT
resistance in various forms of Anopheles mosquitoes, and the appearance of myxomatosis resistance in breeding
rabbit populations in Australia, are all evidence of the existence of evolution in situations of evolutionary selection
pressure in species in which generations occur rapidly.

E. coli long-term evolution experiment

Experimental evolution uses controlled experiments to test hypotheses and theories of evolution. In one early
example, William Dallinger set up an experiment shortly before 1880, subjecting microbes to heat with the aim of
forcing adaptive changes. His experiment ran for around seven years, and his published results were acclaimed, but
he did not resume the experiment after the apparatus failed.[59]
The E. coli long-term evolution experiment begun in 1988 under the leadership of Richard Lenski is still in progress,
and has shown adaptations including the evolution of a strain of E. coli that was able to grow on citric acid in the
growth media.
Evidence of common descent 201

Humans
Natural selection is being observed in contemporary human populations, with recent findings demonstrating the
population which is at risk of the severe debilitating disease kuru has significant over-representation of an immune
variant of the prion protein gene G127V versus non-immune alleles. Scientists postulate one of the reasons for the
rapid selection of this genetic variant is the lethality of the disease in non-immune persons.[60] [61] Other reported
evolutionary trends in other populations include a lengthening of the reproductive period, reduction in cholesterol
levels, blood glucose and blood pressure.[62]

Lactose intolerance in humans

Lactose intolerance is the inability to metabolize lactose, because of a lack of the required enzyme lactase in the
digestive system. The normal mammalian condition is for the young of a species to experience reduced lactase
production at the end of the weaning period (a species-specific length of time). In humans, in non-dairy consuming
societies, lactase production usually drops about 90% during the first four years of life, although the exact drop over
time varies widely.[63] However, certain human populations have a mutation on chromosome 2 which eliminates the
shutdown in lactase production, making it possible for members of these populations to continue consumption of
fresh milk and other dairy products throughout their lives without difficulty. This appears to be an evolutionarily
recent adaptation to dairy consumption, and has occurred independently in both northern Europe and east Africa in
populations with a historically pastoral lifestyle.[64]

Nylon-eating bacteria
Nylon-eating bacteria are a strain of Flavobacterium that is capable of digesting certain byproducts of nylon 6
manufacture. There is scientific consensus that the capacity to synthesize nylonase most probably developed as a
single-step mutation that survived because it improved the fitness of the bacteria possessing the mutation. This is
seen as a good example of evolution through mutation and natural selection that has been observed as it occurs.[65]
[66] [67] [68]

Peppered moth
One classic example of adaptation in response to selection pressure is the case of the peppered moth. The color of the
moth has gone from light to dark to light again over the course of a few hundred years due to the appearance and
later disappearance of pollution from the Industrial Revolution in England.

Radiotrophic fungus
Recently evolved Radiotrophic fungi are fungi which appear to use the pigment melanin to convert gamma radiation
into chemical energy for growth[69] [70] and were first discovered in 2007 as black molds growing inside and around
the Chernobyl Nuclear Power Plant.[69] Research at the Albert Einstein College of Medicine showed that three
melanin-containing fungi, Cladosporium sphaerospermum, Wangiella dermatitidis, and Cryptococcus neoformans,
increased in biomass and accumulated acetate faster in an environment in which the radiation level was 500 times
higher than in the normal environment.

Urban wildlife
Urban wildlife is wildlife that is able to live or thrive in urban environments. These types of environments can exert
selection pressures on organism, often leading to new adaptations. For example, the weed Crepis sancta, found in
France, has two types of seed, heavy and fluffy. The heavy ones land nearby to the parent plant, whereas the fluffy
seeds float further away on the wind. In urban environments, seeds that float far will often land on infertile concrete.
Within about 5-12 generations, the weed has been found to evolve to produce significantly more heavy seeds than its
rural relatives do.[71] [72] Other examples of urban wildlife are rock pigeons and species of crows adapting to city
environments around the world; African penguins in Simons Town; baboons in South Africa; and a variety of insects
Evidence of common descent 202

living in human habitations.

Evidence from observed speciation

Speciation is the evolutionary process by which new biological species arise. Speciation can occur from a variety of
different causes and are classified in various forms (e.g. allopatric, sympatric, polyploidization, etc). Scientists have
observed numerous examples of speciation in the laboratory and in nature, however, evolution has produced far
more species than an observer would consider necessary. For example, there are well over 350,000 described species
of beetles.[73] Great examples of observed speciation come from the observations of island biogeography and the
process of adaptive radiation, both explained in an earlier section. The examples shown below provide strong
evidence for common descent and are only a small fraction of the instances observed.

Specific examples

Blackcap
The bird species, Sylvia atricapillab, commonly referred to as Blackcaps, lives in Germany and flies southwest to
Spain while a smaller group flies northwest to Great Britain during the winter. The smaller blackcap population only
recently rerouted to Spain. Gregor Rolshausen from the University of Freiburg found that the genetic separation of
the two populations is already in progress. The differences found have arisen in about 30 generations. With DNA
sequencing, the individuals can be assigned to a correct group with an 85% accuracy. Stuart Bearhop from the
University of Exeter reported that birds wintering in England tend to mate only among themselves, and not usually
with those wintering in the Mediterranean. (Bearhop et al. 2005) It is still inference to say that the populations will
become two different species, but experts deduce that it is expected due to the continued genetic and geographic
separation.[74]

Drosophila melanogaster

William R. Rice and George W. Salt found experimental evidence of

sympatric speciation in the common fruit fly. They collected a
population of Drosophila melanogaster from Davis, California and
placed the pupae into a habitat maze. Newborn flies had to investigate
the maze to find food. The flies had three choices to take in finding
food. Light and dark (phototaxis), up and down (geotaxis), and the scent
of acetaldehyde and the scent of ethanol (chemotaxis) were the three
options. This eventually divided the flies into 42 spatio-temporal
habitats.
A common fruit fly (Drosophila melanogaster).
They then cultured two strains that chose opposite habitats. One of the
strains emerged early, immediately flying upward in the dark attracted to the acetaldehyde. The other strain emerged
late and immediately flew downward, attracted to light and ethanol. Pupae from the two strains were then placed
together in the maze and allowed to mate at the food site. They then were collected. A selective penalty was imposed
on the female flies that switched habitats. This entailed that none of their gametes would pass on to the next
generation. After 25 generations of this mating test, it showed reproductive isolation between the two strains. They
repeated the experiment again without creating the penalty against habitat switching and the result was the same;
reproductive isolation was produced.[75] [76] [77]
Evidence of common descent 203

Hawthorn fly
One example of evolution at work is the case of the hawthorn fly, Rhagoletis pomonella, also known as the apple
maggot fly, which appears to be undergoing sympatric speciation.[78] Different populations of hawthorn fly feed on
different fruits. A distinct population emerged in North America in the 19th century some time after apples, a
non-native species, were introduced. This apple-feeding population normally feeds only on apples and not on the
historically preferred fruit of hawthorns. The current hawthorn feeding population does not normally feed on apples.
Some evidence, such as the fact that six out of thirteen allozyme loci are different, that hawthorn flies mature later in
the season and take longer to mature than apple flies; and that there is little evidence of interbreeding (researchers
have documented a 4-6% hybridization rate) suggests that this is occurring.[79]

London Underground mosquito

The London Underground mosquito is a species of mosquito in the genus Culex found in the London Underground.
It is thought to have evolved from the overground species Culex pipiens recently.
This mosquito, although first discovered in the London Underground system, has been found in underground
systems around the world. It is suggested that it may have adapted to human-made underground systems since the
last century from local above-ground Culex pipiens,[80] although more recent evidence suggests that it is a southern
mosquito variety related to Culex pipiens that has adapted to the warm underground spaces of northern cities.[81]
The evidence for this mosquito being a different species from Culex pipiens comes from research by Kate Byne and
Richard Nichols. The species have very different behaviours,[82] are extremely difficult to mate,[80] and with
different allele frequency, consistent with genetic drift during a founder event.[83] More specifically, this mosquito,
Culex pipiens molestus, breeds all-year round, is cold intolerant, and bites rats, mice, and humans, in contrast to the
above ground species Culex pipiens that is cold tolerant, hibernates in the winter, and bites only birds. When the two
varieties were cross-bred the eggs were infertile suggesting reproductive isolation.[80] [82]
The fundamental results still stands: the genetic data indicate that the molestus form in the London Underground
mosquito appeared to have a common ancestry, rather than the population at each station being related to the nearest
above-ground population (i.e. the pipiens form). Byrne and Nichols' working hypothesis was that adaptation to the
underground environment had occurred locally in London once only.
These widely separated populations are distinguished by very minor genetic differences, which suggest that the
molestus form developed recently: a single mtDNA difference shared among the underground populations of ten
Russian cities;[84] a single fixed microsatellite difference in populations spanning Europe, Japan, Australia, the
middle East and Atlantic islands.[81]

Madeira House Mouse

The Madeira House mouse is a new species of mouse descended from the house mouse (Mus Musculus) that went
through a recent speciation event.[85]

Mollies
The Shortfin Molly—Poecilia Mexicana—is a small fish that lives in the Sulfur Caves of Mexico. Michael Tobler
from the Texas A&M University has studied the fish for years and found that two distinct populations of
mollies—the dark interior fish and the bright surface water fish—are becoming more genetically divergent. (Tobler
et al. 2009) The populations have no obvious barrier separating the two; however, it was found that the mollies are
hunted by a large water bug (Belostoma spp). Tobler collected the bug and both types of mollies, placed them in
large plastic bottles, and put them back in the cave. After a day, it was found that, in the light, the cave-adapted fish
endured the most damage, with four out of every five stab-wounds from the water bugs sharp mouthparts. In the
dark, the situation was the opposite. The mollies’ senses can detect a predator’s threat in their own habitats, but not in
the other ones. Moving from one habitat to the other significantly increases the risk of dying. Tobler plans on further
Evidence of common descent 204

experiments, but it is believed that it is a good example of the rise of a new species.[86]

Thale cress

Kirsten Bomblies et al. from the Max Planck Institute for Developmental
Biology discovered that two genes passed down by each parent of the thale
cress plant, Arabidopsis thaliana. When the genes are passed down, it ignites
a reaction in the hybrid plant that turns its own immune system against it. In
the parents, the genes were not detrimental, but they evolved separately to
react defectively when combined. (Bomlies et al. 2007)

To test this, Bomblies crossed 280 genetically different strains of Arabidopsis

in 861 distinct ways and found that 2 per cent of the resulting hybrids were
necrotic. Along with allocating the same indicators, the 20 plants also shared
a comparable collection of genetic activity in a group of 1,080 genes. In
almost all of the cases, Bomblies discovered that only two genes were
required to cause the autoimmune response. Bomblies looked at one hybrid in
detail and found that one of the two genes belonged to the NB-LRR class, a
Arabidopsis thaliana (colloquially
common group of disease resistance genes involved in recognizing new
known as thale cress, mouse-ear cress or
infections. When Bomblies removed the problematic gene, the hybrids Arabidopsis).
developed normally. (Bomlies et al. 2007)

Over successive generations, these incompatibilities could create divisions between different plant strains, reducing
their chances of successful mating and turning distinct strains into separate species.[87]

Interspecies fertility or hybridization

Understood from laboratory studies and observed instances of speciation in nature, finding species that are able
reproduce successfully or create hybrids between two different species infers that their relationship is close. In
conjunction with this, hybridization has been found to be a precursor to the creation of new species by being a source
of new genes for a species. The examples provided are only a small fraction of the observed instances of speciation
through hybridization. It is worth noting that plants are often subject to the creation of a new species though
hybridization.

Polar bear
A specific example of large-scale evolution is the polar bear (Ursus maritimus), which though clearly related to the
brown bear (Ursus arctos) by virtue of the fact that though separate species they can still interbreed and produce
fertile offspring[88] it has also obviously acquired significant physiological differences from the brown bear. These
differences allow the polar bear to comfortably survive in conditions that the brown could not including the ability to
swim sixty miles or more at a time in freezing waters, blend in—the change in fur color—and to stay warm in the
arctic environment. Additionally, the elongation of the neck makes it easier to keep their heads above water while
swimming and the oversized webbed feet that act as paddles when swimming. The polar bear has also evolved small
papillae and vacuole-like suction cups on the soles to make them less likely to slip on the ice, feet covered with
heavy matting to protect the bottoms from intense cold and provide traction, smaller ears to reduce the loss of heat,
eyelids that act like sunglasses, to accommodate their all-meat diet, a large stomach capacity to enable opportunistic
feeding, and the ability to fast for up to nine months while recycling their urea.[89] [90]
Evidence of common descent 205

Raphanobrassica
Raphanobrassica includes all intergeneric hybrids between the genera Raphanus (radish) and Brassica (cabbages,
etc).[91] [92]
The Raphanobrassica is an allopolyploid cross between the radish (Raphanus sativus) and cabbage (Brassica
oleracea). Plants of this parentage are now known as radicole. Two other fertile forms of Raphanobrassica are
known. Raparadish, an allopolyploid hybrid between Raphanus sativus and Brassica rapa is grown as a fodder crop.
"Raphanofortii" is the allopolyploid hybrid between Brassica tournefortii and Raphanus caudatus.
The Raphanobrassica is a fascinating plant, because—in spite of its hybrid nature—it is not sterile. This has led
some botanists to propose that the accidental hybridization of a flower by pollen of another species in nature could
be a mechanism of speciation common in higher plants.

Salsify

Salsifies are one example where hybrid speciation has been observed. In the
early 20th century, humans introduced three species of goatsbeard into North
America. These species, the western salsify (T. dubius), the meadow salsify
(T. pratensis), and the oyster plant (T. porrifolius), are now common weeds in
urban wastelands. In the 1950s, botanists found two new species in the
regions of Idaho and Washington, where the three already known species
overlapped. One new species, Tragopogon miscellus, is a tetraploid hybrid of
T. dubius and T. pratensis. The other species, Tragopogon mirus, is also an
allopolyploid, but its ancestors were T. dubius and T. porrifolius. These new
species are usually referred to as "the Ownbey hybrids" after the botanist who
first described them. The T. mirus population grows mainly by reproduction
of its own members, but additional episodes of hybridization continue to add
to the T. mirus population.

Welsh groundsel Purple Salsify, Tragopogon porrifolius

Welsh groundsel is an allopolyploid, a plant which contains sets of

chromosomes originating from two different species. Its ancestor was Senecio × baxteri, an infertile hybrid which
can arise spontaneously when the closely-related groundsel (Senecio vulgaris) and Oxford ragwort (Senecio
squalidus) grow alongside each other. Sometime in the early 20th century, an accidental doubling of the number of
chromosomes in an S. × baxteri plant led to the formation of a new fertile species.[93] [94]

York groundsel
The York groundsel (Senecio eboracensis) is a hybrid species of the self-incompatible Senecio squalidus (also
known as Oxford ragwort) and the self-compatible Senecio vulgaris (also known as Common groundsel). Like S.
vulgaris, S. eboracensis is self-compatible, however, it shows little or no natural crossing with its parent species, and
is therefore reproductively isolated, indicating that strong breed barriers exist between this new hybrid and its
parents.
It is thought to have resulted from a backcrossing of the F1 hybrid of its parents to S. vulgaris. S. vulgaris is native to
Britain, while S. squalidus was introduced from Sicily in the early 18th century; therefore, S. eboracensis has
speciated from those two species within the last 300 years.
Other hybrids descended from the same two parents are known. Some are infertile, such as S. x baxteri. Other fertile
hybrids are also known, including S. vulgaris var. hibernicus, now common in Britain, and the allohexaploid S.
cambrensis, which according to molecular evidence probably originated independently at least three times in
Evidence of common descent 206

different locations. Morphological and genetic evidence support the status of S. eboracensis as separate from other
known hybrids.[95]

Evidence from artificial selection

Artificial selection demonstrates the diversity that can exist among
organisms that share a relatively recent common ancestor. In artificial
selection, one species is bred selectively at each generation, allowing
only those organisms that exhibit desired characteristics to reproduce.
These characteristics become increasingly well-developed in successive
generations. Artificial selection was successful long before science
discovered the genetic basis. Examples of artificial selection would be
dog breeding, genetically modified food, flower breeding, cultivation of
foods such as wild cabbage,[96] and others.

The Chihuahua mix and Great Dane illustrate

the range of sizes among dog breeds.
Evidence from computation and mathematical
iteration
"It has taken more than five decades, but the electronic computer is now powerful enough to simulate evolution"[97]
assisting bioinformatics in its attempt to solve biological problems.
Computer science allows the iteration of self changing complex systems to be studied, allowing a mathematical
understanding of the nature of the processes behind evolution; providing evidence for the hidden causes of known
evolutionary events. The evolution of specific cellular mechanisms like spliceosomes that can turn the cell's genome
into a vast workshop of billions of interchangeable parts that can create tools that create tools that create tools that
create us can be studied for the first time in an exact way.
For example, Christoph Adami et al. make this point in Evolution of biological complexity:
To make a case for or against a trend in the evolution of complexity in biological evolution, complexity needs
to be both rigorously defined and measurable. A recent information-theoretic (but intuitively evident)
definition identifies genomic complexity with the amount of information a sequence stores about its
environment. We investigate the evolution of genomic complexity in populations of digital organisms and
monitor in detail the evolutionary transitions that increase complexity. We show that, because natural selection
forces genomes to behave as a natural "Maxwell Demon," within a fixed environment, genomic complexity is
forced to increase.[98]
For example, David J. Earl and Michael W. Deem make this point in Evolvability is a selectable trait:
Not only has life evolved, but life has evolved to evolve. That is, correlations within protein structure have
evolved, and mechanisms to manipulate these correlations have evolved in tandem. The rates at which the
various events within the hierarchy of evolutionary moves occur are not random or arbitrary but are selected
by Darwinian evolution. Sensibly, rapid or extreme environmental change leads to selection for greater
evolvability. This selection is not forbidden by causality and is strongest on the largest-scale moves within the
mutational hierarchy. Many observations within evolutionary biology, heretofore considered evolutionary
happenstance or accidents, are explained by selection for evolvability. For example, the vertebrate immune
system shows that the variable environment of antigens has provided selective pressure for the use of
adaptable codons and low-fidelity polymerases during somatic hypermutation. A similar driving force for
biased codon usage as a result of productively high mutation rates is observed in the hemagglutinin protein of
influenza A.[99]
Evidence of common descent 207

"Computer simulations of the evolution of linear sequences have demonstrated the importance of recombination of
blocks of sequence rather than point mutagenesis alone. Repeated cycles of point mutagenesis, recombination, and
selection should allow in vitro molecular evolution of complex sequences, such as proteins."[100] Evolutionary
molecular engineering, also called directed evolution or in vitro molecular evolution involves the iterated cycle of
mutation, multiplication with recombination, and selection of the fittest of individual molecules (proteins, DNA, and
RNA). Natural evolution can be relived showing us possible paths from catalytic cycles based on proteins to based
on RNA to based on DNA.[100] [101] [102] [103]

See also
• Nothing in Biology Makes Sense Except in the Light of Evolution

Sources
• Bearhop, Stuart; Fiedler, Wolfgang; Furness, Robert W.; Votier, Stephen C.; Waldron, Susan; Newton, Jason;
Bowen, Gabriel J.; Berthold, Peter & Farnsworth, Keith (2005): Assortative mating as a mechanism for rapid
evolution of a migratory divide. Science 310(5747): 502-504. doi:10.1126/science.1115661 (HTML abstract)
Supporting Online Material [104]
• Bomblies, Lempe, Epple, Warthmann, Lanz, Dangl & Weigel. 2007. Autoimmune response as a mechanism for a
Dobhansky-Muller-Type incompatibility syndrome in plants. PLoS Biol 5: e236
doi:10.1371/journal.pbio.0050236
• Davis, Paul and Kenrick, Paul. 2004. Fossil Plants. Smithsonian Books (in association with the Natural History
Museum of London), Washington, D.C. ISBN 1-58834-156-9
• Tobler, Micheal (2009). Does a predatory insect contribute to the divergence between cave- and surface-adapted
fish populations? Biology Letters doi:10.1098/rsbl.2009.0272

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populations". Heredity 82 (1): 7–15. doi:10.1038/sj.hdy.6884120. PMID 10200079.
[84] Vinogradova EB and Shaikevich EV Morphometric, physiological and molecular characteristics of underground populations of the urban
mosquito Culex pipiens Linnaeus f. molestus Forskål (Diptera: Culicidae) from several areas of Russia European Mosquito Bulletin, 22(2007),
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[89] Polar Bear Evolution (http:/ / www. polarbearsinternational. org/ bear-facts/ polar-bear-evolution/ )
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[102] (http:/ / bio. kaist. ac. kr/ ~jsrhee/ research03. html)
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Evidence of common descent 211

Further reading
• Biological science, Oxford, 2002.
• Clegg CJ (1998). Genetics & evolution. London: J. Murray. ISBN 0-7195-7552-4.
• Coyne, Jerry A. (2009). Why Evolution is True. New York: Oxford University Press. ISBN 978-0-19-923084-6.
• Darwin, Charles November 24, 1859. On the Origin of Species by means of Natural Selection or the Preservation
of Favoured Races in the Struggle for Life. London: John Murray, Albemarle Street. 502 pages. Reprinted:
Gramercy (May 22, 1995). ISBN 0-517-12320-7
• Dawkins, Richard (2009). The Greatest Show on Earth: The Evidence for Evolution. Bantam Press.
ISBN 978-1-4165-9478-9.
• Endler, John A. (1986). Natural selection in the wild. New Jersey: Princton University Press.
ISBN 0-691-08387-8.
• Futuyma, D.J. 1998. Evolutionary Biology. 3rd ed. Sinauer Associates, Sunderland, Massachusetts. (dated 1998,
published 1997) ISBN 0-87893-189-9
• Gigerenzer, Gerd (1989). The Empire of chance: how probability changed science and everyday life. Cambridge,
UK: Cambridge University Press. ISBN 0-521-33115-3.
• Hill A, Behrensmeyer AK (1980). Fossils in the making: vertebrate taphonomy and paleoecology. Chicago:
University of Chicago Press. ISBN 0-226-04169-7.
• Ho, YK (2004). Advanced-level Biology for Hong Kong, Manhattan Press. ISBN 962-990-635-X
• Martin RE (1999). Taphonomy: a process approach. Cambridge, UK: Cambridge University Press.
ISBN 0-521-59833-8.
• Mayr, Ernst (2001). What evolution is. New York: Basic Books. ISBN 0-465-04426-3.
• Paul CRC, Donovan SK (1998). The adequacy of the fossil record. New York: John Wiley. ISBN 0-471-96988-5.
• Sober, Elliott (2008). Evidence and Evolution: The logic behind the science. Cambridge University Press.
ISBN 978-0-521-87188-4.

External links
• National Academies Evolution Resources (http://nationalacademies.org/evolution/)
• TalkOrigins Archive - 29+ Evidences for Macroevolution: The Scientific Case for Common Descent (http://
www.talkorigins.org/faqs/comdesc/)
• TalkOrigins Archive - Transitional Vertebrate Fossils FAQ (http://www.talkorigins.org/faqs/faq-transitional.
html)
• Understanding Evolution: Your one-stop source for information on evolution (http://evolution.berkeley.edu/
evosite/evo101/index.shtml)
• National Academy Press: Teaching About Evolution and the Nature of Science (http://www.nap.edu/books/
0309063647/html/)
• Evolution (http://www.pbs.org/wgbh/evolution/index.html) — Provided by PBS.
• Evolution News from Genome News Network (GNN) (http://www.genomenewsnetwork.org/categories/index/
genome/evolution.php)
• Evolution by Natural Selection (http://www.chainsofreason.org/wiki/Chain_3) — An introduction to the logic
of the theory of evolution by natural selection
• Howstuffworks.com — How Evolution Works (http://science.howstuffworks.com/evolution.htm/printable)
• 15 Evolutionary Gems (http://www.nature.com/nature/newspdf/evolutiongems.pdf)
 212

Mechanisms

Adaptation
Adaptation is the evolutionary process whereby a population becomes better suited to its habitat.[1] [2] This process
takes place over many generations,[3] and is one of the basic phenomena of biology.[4]
The term adaptation may also refer to a feature which is especially important for an organism's survival.[5] For
example, the adaptation of horses' teeth to the grinding of grass, or their ability to run fast and escape predators. Such
adaptations are produced in a variable population by the better suited forms reproducing more successfully, that is,
by natural selection.

General principles
The significance of an adaptation can only be understood in relation to the total biology of the species.
Julian Huxley[6]
Adaptation is, first of all, a process, rather than a physical part of a body.[7] The distinction may be seen in an
internal parasite (such as a fluke), where the bodily structure is greatly simplified, but nevertheless the organism is
highly adapted to its unusual environment. From this we see that adaptation is not just a matter of visible traits: in
such parasites critical adaptations take place in the life-cycle, which is often quite complex.[8] However, as a
practical term, adaptation is often used for the product: those features of a species which result from the process.
Many aspects of an animal or plant can be correctly called adaptations, though there are always some features whose
function is in doubt. By using the term adaptation for the evolutionary process, and adaptive trait for the bodily part
or function (the product), the two senses of the word may be distinguished.
Adaptation is one of the two main processes that explain the diverse species we see in biology, such as the different
species of Darwin's finches. The other is speciation (species-splitting or cladogenesis), caused by geographical
isolation or some other mechanism.[9] [10] A favourite example used today to study the interplay of adaptation and
speciation is the evolution of cichlid fish in African lakes, where the question of reproductive isolation is much more
complex.[11] [12]
Adaptation is not always a simple matter, where the ideal phenotype evolves for a given external environment. An
organism must be viable at all stages of its development and at all stages of its evolution. This places constraints on
the evolution of development, behaviour and structure of organisms. The main constraint, over which there has been
much debate, is the requirement that each genetic and phenotypic change during evolution should be relatively small,
because developmental systems are so complex and interlinked. However, it is not clear what "relatively small"
should mean, for example polyploidy in plants is a reasonably common large genetic change.[13] The origin of the
symbiosis of multiple micro-organisms to form a eukaryota is a more exotic example.[14]
All adaptations help organisms survive in their ecological niches.[15] These adaptive traits may be structural,
behavioral or physiological. Structural adaptations are physical features of an organism (shape, body covering,
armament; and also the internal organization). Behavioural adaptations are composed of inherited behaviour chains
and/or the ability to learn: behaviours may be inherited in detail (instincts), or a tendency for learning may be
inherited (see neuropsychology). Examples: searching for food, mating, vocalizations. Physiological adaptations
permit the organism to perform special functions (for instance, making venom, secreting slime, phototropism); but
also more general functions such as growth and development, temperature regulation, ionic balance and other aspects
of homeostasis. Adaptation, then, affects all aspects of the life of an organism.
Adaptation 213

Definitions
The following definitions are mainly due to Theodosius Dobzhansky.
1. Adaptation is the evolutionary process whereby an organism becomes better able to live in its habitat or
habitats.[16]
2. Adaptedness is the state of being adapted: the degree to which an organism is able to live and reproduce in a
given set of habitats.[17]
3. An adaptive trait is an aspect of the developmental pattern of the organism which enables or enhances the
probability of that organism surviving and reproducing.[18]

Adaptedness and fitness

From the above definitions, it is clear that there is a relationship between adaptedness and fitness (a key population
genetics concept). Differences in fitness between genotypes predict the rate of evolution by natural selection. Natural
selection changes the relative frequencies of alternative phenotypes, insofar as they are heritable.[19] Although the
two are connected, the one does not imply the other: a phenotype with high adaptedness may not have high fitness.
Dobzhansky mentioned the example of the Californian redwood, which is highly adapted, but a relic species in
danger of extinction.[16] Elliott Sober commented that adaptation was a retrospective concept since it implied
something about the history of a trait, whereas fitness predicts a trait's future.[20]
1. Relative fitness. The average contribution to the next generation by a phenotype or a class of phenotypes,
relative to the contributions of other phenotypes in the population. This is also known as Darwinian fitness,
selective coefficient, and other terms.
2. Absolute fitness. The absolute contribution to the next generation by a phenotype or a class of phenotypes.
Also known as the Malthusian parameter when applied to the population as a whole.[21]
3. Adaptedness. The extent to which a phenotype fits its local ecological niche. This can sometimes be tested
through a reciprocal transplant experiment.

Brief history
Adaptation as a fact of life has been accepted by all the great thinkers who have tackled the world of living
organisms. It is their explanations of how adaptation arises that separates these thinkers. A few of the most
significant ideas:[22]
• Empedocles did not believe that adaptation required a final cause (~ purpose), but "came about naturally, since
such things survived". Aristotle, however, did believe in final causes.
• In natural theology, adaptation was interpreted as the work of a deity, even as evidence for the existence of
God.[23] William Paley believed that organisms were perfectly adapted to the lives they lead, an argument that
shadowed Leibniz, who had argued that God had brought about the best of all possible worlds. Voltaire's Dr
Pangloss[24] is a parody of this optimistic idea, and Hume also argued against design.[25] The Bridgewater
Treatises are a product of natural theology, though some of the authors managed to present their work in a fairly
neutral manner. The series was lampooned by Robert Knox, who held quasi-evolutionary views, as the Bilgewater
Treatises. Darwin broke with the tradition by emphasising the flaws and limitations which occurred in the animal
and plant worlds.[26]
Adaptation 214

• Lamarck. His is a proto-evolutionary theory of the inheritance of acquired traits,

whose main purpose is to explain adaptations by natural means.[27] He proposed a
tendency for organisms to become more complex, moving up a ladder of
progress, plus "the influence of circumstances", usually expressed as use and
disuse. His evolutionary ideas, and those of Geoffroy, fail because they cannot be
reconciled with heredity. This was known even before Mendel by medical men
interested in human races (Wells, Lawrence), and especially by Weismann.

Many other students of natural history, such as Buffon, accepted adaptation, and
some also accepted evolution, without voicing their opinions as to the mechanism.
This illustrates the real merit of Darwin and Wallace, and secondary figures such as Lamarck
Bates, for putting forward a mechanism whose significance had only been glimpsed
previously. A century later, experimental field studies and breeding experiments by such as Ford and Dobzhansky
produced evidence that natural selection was not only the 'engine' behind adaptation, but was a much stronger force
than had previously been thought.[28] [29] [30]

Types of adaptation
Adaptation is the heart and soul of evolution. Niles Eldredge[31]

Changes in habitat
Before Darwin, adaptation was seen as a fixed relationship between an organism and its habitat. It was not
appreciated that as the climate changed, so did the habitat; and as the habitat changed, so did the biota. Also, habitats
are subject to changes in their biota: for example, invasions of species from other areas. The relative numbers of
species in a given habitat are always changing. Change is the rule, though much depends on the speed and degree of
the change.
When the habitat changes, three main things may happen to a resident population: habitat tracking, genetic change or
extinction. In fact, all three things may occur in sequence. Of these three effects, only genetic change brings about
adaptation.

Habitat tracking
When a habitat changes, the most common thing to happen is that the resident population moves to another locale
which suits it; this is the typical response of flying insects or oceanic organisms, who have wide (though not
unlimited) opportunity for movement.[32] This common response is called habitat tracking. It is one explanation put
forward for the periods of apparent stasis in the fossil record (the punctuated equilibrium thesis).[33]

Genetic change
Genetic change is what occurs in a population when natural selection acts on the genetic variability of the
population. By this means, the population adapts genetically to its circumstances.[34] Genetic changes may result in
visible structures, or may adjust physiological activity in a way that suits the changed habitat.
It is now clear that habitats and biota do frequently change. Therefore, it follows that the process of adaptation is
never finally complete.[35] Over time, it may happen that the environment changes little, and the species comes to fit
its surroundings better and better. On the other hand, it may happen that changes in the environment occur relatively
rapidly, and then the species becomes less and less well adapted. Seen like this, adaptation is a genetic tracking
process, which goes on all the time to some extent, but especially when the population cannot or does not move to
another, less hostile area. Also, to a greater or lesser extent, the process affects every species in a particular
ecosystem.[36] [37]
Adaptation 215

Van Valen thought that even in a stable environment, competing species had to constantly adapt to maintain their
relative standing. This became known as the Red Queen hypothesis.

Intimate relationships: co-adaptations

In co-evolution, where the existence of one species is tightly bound up with the life of another species, new or
'improved' adaptations which occur in one species are often followed by the appearance and spread of corresponding
features in the other species. There are many examples of this; the idea emphasises that the life and death of living
things is intimately connected, not just with the physical environment, but with the life of other species. These
relationships are intrinsically dynamic, and may continue on a trajectory for millions of years, as has the relationship
between flowering plants and insects (pollination).
Pollinator constancy: these honeybees selectively visit flowers from only one species, as can be seen by the colour of
the pollen in their baskets:

• Co-extinction
• Infection-resistance
• Mimicry
• Mutualism
• Parasite-host
• Pollination syndrome
• Predator-prey
• Symbiosis
The gut contents, wing structures, and mouthpart morphologies of fossilized beetles and flies suggest that they acted
as early pollinators. The association between beetles and angiosperms during the early Cretaceous period led to
parallel radiations of angiosperms and insects into the late Cretaceous. The evolution of nectaries in late Cretaceous
flowers signals the beginning of the mutualism between hymenopterans and angiosperms.[38]
Adaptation 216

Mimicry

Henry Walter Bates' work on Amazonian butterflies led him to develop

the first scientific account of mimicry, especially the kind of mimicry
which bears his name: Batesian mimicry.[39] This is the mimicry by a
palatable species of an unpalatable or noxious species. A common
example seen in temperate gardens is the hover-fly, many of which –
though bearing no sting – mimic the warning colouration of
hymenoptera (wasps and bees). Such mimicry does not need to be
perfect to improve the survival of the palatable species.[40]

Bates, Wallace and Müller believed that Batesian and Müllerian

mimicry provided evidence for the action of natural selection, a view
which is now standard amongst biologists.[41] All aspects of this
situation can be, and have been, the subject of research.[42] Field and
experimental work on these ideas continues to this day; the topic
connects strongly to speciation, genetics and development.[43]
A and B show real wasps; the rest are mimics:
• More on mimicry: Warning Colour and Mimicry [44] Lecture outline three hoverflies and one beetle.
from University College London

The basic machinery: internal adaptations

There are some important adaptations to do with the overall coordination of the systems in the body. Such
adaptations may have significant consequences. Examples, in vertebrates, would be temperature regulation, or
improvements in brain function, or an effective immune system. An example in plants would be the development of
the reproductive system in flowering plants.[45] Such adaptations may make the clade (monophyletic group) more
viable in a wide range of habitats. The acquisition of such major adaptations has often served as the spark for
adaptive radiation, and huge success for long periods of time for a whole group of animals or plants.

Compromise and conflict between adaptations

It is a profound truth that Nature does not know best; that genetical evolution... is a story of waste,
makeshift, compromise and blunder. Peter Medawar[46]
All adaptations have a downside: horse legs are great for running on grass, but they can't scratch their backs;
mammals' hair helps temperature, but offers a niche for ectoparasites; the only flying penguins do is under water.
Adaptations serving different functions may be mutually destructive. Compromise and make-shift occur widely, not
perfection. Selection pressures pull in different directions, and the adaptation that results is some kind of
compromise.[47]
Since the phenotype as a whole is the target of selection, it is impossible to improve simultaneously all aspects
of the phenotype to the same degree. Ernst Mayr.[48]
Consider the antlers of the Irish elk, (often supposed to be far too large; in deer antler size has an allometric
relationship to body size). Obviously antlers serve positively for defence against predators, and to score victories in
the annual rut. But they are costly in terms of resource. Their size during the last glacial period presumably depended
on the relative gain and loss of reproductive capacity in the population of elks during that time.[49] Another example:
camouflage to avoid detection is destroyed when vivid colors are displayed at mating time. Here the risk to life is
counterbalanced by the necessity for reproduction.
Adaptation 217

The peacock's ornamental train (grown anew in time for each

mating season) is a famous adaptation. It must reduce his
maneuverability and flight, and is hugely conspicuous; also, its
growth costs food resources. Darwin's explanation of its advantage
was in terms of sexual selection: "it depends on the advantage
which certain individuals have over other individuals of the same
sex and species, in exclusive relation to reproduction."[50] The
kind of sexual selection represented by the peacock is called 'mate
choice', with an implication that the process selects the more fit
over the less fit, and so has survival value.[51] The recognition of
An Indian Peacock's train
sexual selection was for a long time in abeyance, but has been in full display
rehabilitated.[52] In practice, the blue peafowl Pavo cristatus is a
pretty successful species, with a big natural range in India, so the
overall outcome of their mating system is quite viable.

The conflict between the size of the human foetal brain at birth, (which cannot be larger than about 400ccs, else it
will not get through the mother's pelvis) and the size needed for an adult brain (about 1400ccs), means the brain of a
newborn child is quite immature. The most vital things in human life (locomotion, speech) just have to wait while
the brain grows and matures. That is the result of the birth compromise. Much of the problem comes from our
upright bipedal stance, without which our pelvis could be shaped more suitably for birth. Neanderthals had a similar
problem.[53] [54] [55]

Shifts in function
Adaptation and function are two aspects of one problem. Julian Huxley[56]

Pre-adaptations
This occurs when a species or population has characteristics which (by chance) are suited for conditions which have
not yet arisen. For example, the polyploid rice-grass Spartina townsendii is better adapted than either of its parent
species to their own habitat of saline marsh and mud-flats.[57] White Leghorn fowl are markedly more resistant to
vitamin B deficiency than other breeds.[58] On a plentiful diet there is no difference, but on a restricted diet this
preadaptation could be decisive.
Pre-adaptation may occur because a natural population carries a huge quantity of genetic variability.[59] In diploid
eukaryotes, this is a consequence of the system of sexual reproduction, where mutant alleles get partially shielded,
for example, by the selective advantage of heterozygotes. Micro-organisms, with their huge populations, also carry a
great deal of genetic variability.
The first experimental evidence of the pre-adaptive nature of genetic variants in micro-organisms was provided by
Salvador Luria and Max Delbrück who developed fluctuation analysis, a method to show the random fluctuation of
pre-existing genetic changes that conferred resistance to phage in the bacterium Escherichia coli.

Co-option of existing traits: exaptation

The classic example is the ear ossicles of mammals, which we know from palaeontological and embrological studies
originated in the upper and lower jaws and the hyoid of their Synapsid ancestors, and further back still were part of
the gill arches of early fish.[60] [61] We owe this esoteric knowledge to the comparative anatomists, who, a century
ago, were at the cutting edge of evolutionary studies.[62] The word exaptation was coined to cover these shifts in
function, which are surprisingly common in evolutionary history.[63] The origin of wings from feathers that were
originally used for temperature regulation is a more recent discovery (see feathered dinosaurs).
Adaptation 218

Related issues

Non-adaptive traits
Some traits do not appear to be adaptive, that is, they appear to have a neutral or even deleterious effect on fitness in
the current environment. Because genes have pleiotropic effects, not all traits may be functional (i.e. spandrels).
Alternatively, a trait may have been adaptive at some point in an organism's evolutionary history, but a change in
habitats caused what used to be an adaptation to become unnecessary or even a hindrance (maladaptations). Such
adaptations are termed vestigial.

Vestigial organs
Many organisms have vestigial organs, which are the remnants of fully functional structures in their ancestors. As a
result of changes in lifestyle the organs became redundant, and are either not functional or reduced in functionality.
With the loss of function goes the loss of positive selection, and the subsequent accumulation of deleterious
mutations. Since any structure represents some kind of cost to the general economy of the body, an advantage may
accrue from their elimination once they are not functional. Examples: wisdom teeth in humans; the loss of pigment
and functional eyes in cave fauna; the loss of structure in endoparasites.[64]

Fitness landscapes
Sewall Wright proposed that populations occupy adaptive peaks on a fitness landscape. In order to evolve to another,
higher peak, a population would first have to pass through a valley of maladaptive intermediate stages.[65] A given
population might be "trapped" on a peak that is not optimally adapted.

Extinction
If a population cannot move or change sufficiently to preserve its long-term viability, then obviously, it will become
extinct, at least in that locale. The species may or may not survive in other locales. Species extinction occurs when
the death rate over the entire species (population, gene pool ...) exceeds the birth rate for a long enough period for the
species to disappear. It was an observation of Van Valen that groups of species tend to have a characteristic and
fairly regular rate of extinction.[66]

Co-extinction
Just as we have co-adaptation, there is also co-extinction. Co-extinction refers to the loss of a species due to the
extinction of another; for example, the extinction of parasitic insects following the loss of their hosts. Co-extinction
can also occur when a flowering plant loses its pollinator, or through the disruption of a food chain.[67] "Species
co-extinction is a manifestation of the interconnectedness of organisms in complex ecosystems ... While
co-extinction may not be the most important cause of species extinctions, it is certainly an insidious one".[68]

Flexibility, acclimatization, learning

Flexibility deals with the relative capacity of an organism to maintain themselves in different habitats: their degree of
specialization. Acclimatization is a term used for automatic physiological adjustments during life; learning is the
term used for improvement in behavioral performance during life. In biology these terms are preferred, not
adaptation, for changes during life which improve the performance of individuals. These adjustments are not
inherited genetically by the next generation.
Adaptation, on the other hand, occurs over many generations; it is a gradual process caused by natural selection
which changes the genetic make-up of a population so the collective performs better in its niche.
Adaptation 219

Flexibility
Populations differ in their phenotypic plasticity, which is the ability of an organism with a given genotype to change
its phenotype in response to changes in its habitat, or to its move to a different habitat.[69] [70]
To a greater or lesser extent, all living things can adjust to circumstances. The degree of flexibility is inherited, and
varies to some extent between individuals. A highly specialized animal or plant lives only in a well-defined habitat,
eats a specific type of food, and cannot survive if its needs are not met. Many herbivores are like this; extreme
examples are koalas which depend on eucalyptus, and pandas which require bamboo. A generalist, on the other hand,
eats a range of food, and can survive in many different conditions. Examples are humans, rats, crabs and many
carnivores. The tendency to behave in a specialized or exploratory manner is inherited – it is an adaptation.
Rather different is developmental flexibility: "An animal or plant is developmentally flexible if when it is raised or
transferred to new conditions it develops so that it is better fitted to survive in the new circumstances".[71] Once
again, there are huge differences between species, and the capacities to be flexible are inherited.

Acclimatization
If humans move to a higher altitude, respiration and physical exertion become a problem, but after spending time in
high altitude conditions they acclimatize to the pressure by increasing production of red blood corpuscles. The ability
to acclimatize is an adaptation, but not the acclimatization itself. Fecundity goes down, but deaths from some
tropical diseases also goes down.
Over a longer period of time, some people will reproduce better at these high altitudes than others. They will
contribute more heavily to later generations. Gradually the whole population becomes adapted to the new conditions.
This we know takes place, because the performance of long-term communities at higher altitude is significantly
better than the performance of new arrivals, even when the new arrivals have had time to make physiological
adjustments.[72]
Some kinds of acclimatization happen so rapidly that they are better called reflexes. The rapid colour changes in
some flatfish, cephalopods, chameleons are examples.[73]

Learning
Social learning is supreme for humans, and is possible for quite a few mammals and birds: of course, that does not
involve genetic transmission except to the extent that the capacities are inherited. Similarly, the capacity to learn is
an inherited adaptation, but not what is learnt; the capacity for human speech is inherited, but not the details of
language.

Function and teleonomy

Adaptation raises some issues concerning how biologists use key terms such as function.

Function
To say something has a function is to say something about what it does for the organism, obviously. It also says
something about its history: how it has come about. A heart pumps blood: that is its function. It also emits sound,
which is just an ancillary side-effect. That is not its function. The heart has a history (which may be well or poorly
understood), and that history is about how natural selection formed and maintained the heart as a pump. Every aspect
of an organism that has a function has a history. Now, an adaptation must have a functional history: therefore we
expect it must have undergone selection caused by relative survival in its habitat. It would be quite wrong to use the
word adaptation about a trait which arose as a by-product.[74] [75]
It is widely regarded as unprofessional for a biologist to say something like "A wing is for flying", although that is
their normal function. A biologist would be conscious that sometime in the remote past feathers on a small dinosaur
Adaptation 220

had the function of retaining heat, and that later many wings were not used for flying (e.g. penguins, ostriches). So,
the biologist would rather say that the wings on a bird or an insect usually had the function of aiding flight. That
would carry the connotation of being an adaptation with a history of evolution by natural selection.

Teleonomy
Teleonomy is a term invented to describe the study of goal-directed functions which are not guided by the conscious
forethought of man or any supernatural entity. It is contrasted with Aristotle's teleology, which has connotations of
intention, purpose and foresight. Evolution is teleonomic; adaptation hoards hindsight rather than foresight. The
following is a definition for its use in biology:
Teleonomy: The hypothesis that adaptations arise without the existence of a prior purpose, but by the action of
natural selection on genetic variability.[76]
The term may have been suggested by Colin Pittendrigh in 1958;[77] it grew out of cybernetics and self-organising
systems. Ernst Mayr, George C. Williams and Jacques Monod picked up the term and used it in evolutionary
biology.[78] [79] [80] [81]
Philosophers of science have also commented on the term. Ernest Nagel analysed the concept of goal-directedness in
biology;[82] and David Hull commented on the use of teleology and teleonomy by biologists:
Haldane can be found remarking, "Teleology is like a mistress to a biologist: he cannot live without her but
he’s unwilling to be seen with her in public". Today the mistress has become a lawfully wedded wife.
Biologists no longer feel obligated to apologize for their use of teleological language; they flaunt it. The only
concession which they make to its disreputable past is to rename it ‘teleonomy’.[83]

See also
• Adaptive radiation
• Co-adaptation
• Co-evolution
• Ecological trap
• Evolvability
• Exaptation
• Intragenomic conflict
• Maladaptation
• Mimicry
• Polymorphism (biology)

References
[1] The Oxford Dictionary of Science defines adaptation as "Any change in the structure or functioning of an organism that makes it better suited
to its environment".
[2] Bowler P.J. 2003. Evolution: the history of an idea. California. p10
[3] Patterson C. 1999. Evolution. Natural History Museum, London. p1
[4] Williams, George C. 1966. Adaptation and natural selection: a critique of some current evolutionary thought. Princeton. "Evolutionary
adaptation is a phenomenon of pervasive importance in biology." p5
[5] Both uses of the term 'adaptation' are recognized by King R.C. Stansfield W.D. and Mulligan P. 2006. A dictionary of genetics. Oxford, 7th
ed.
[6] Huxley, Julian 1942. Evolution the modern synthesis. Allen & Unwin, London. p449
[7] Mayr, Ernst 1982. The growth of biological thought. Harvard. p483: "Adaptation... could no longer be considered a static condition, a product
of a creative past, and became instead a continuing dynamic process."
[8] Price P.W. 1980. The evolutionary biology of parasites. Princeton.
[9] Mayr E. 1963. Animal species and evolution. Harvard.
[10] Mayr, Ernst 1982. The growth of biological thought: diversity, evolution and inheritance. Harvard. p562–566
Adaptation 221

[11] Salzburger W., Mack T., Verheyen E., Meyer A. (2005). "Out of Tanganyika: Genesis, explosive speciation, key-innovations and
phylogeography of the haplochromine cichlid fishes" (http:/ / www. biomedcentral. com/ content/ pdf/ 1471-2148-5-17. pdf) (PDF). BMC
Evolutionary Biology 5 (1): 17. doi:10.1186/1471-2148-5-17. PMID 15723698. PMC 554777. .
[12] Kornfield, Irv; Smith, Peter (November 2000). "African Cichlid Fishes: Model Systems for Evolutionary Biology" (http:/ / arjournals.
annualreviews. org/ doi/ abs/ 10. 1146/ annurev. ecolsys. 31. 1. 163). Annual Review of Ecology and Systematics 31: 163.
doi:10.1146/annurev.ecolsys.31.1.163. .
[13] Stebbins, G. Ledyard, Jr. 1950. Variation and evolution in plants. Columbia. Polyploidy, chapters 8 and 9.
[14] Margulis, Lynn (ed) 1991. Symbiosis as a source of evolutionary innovation: speciation and morphogenesis MIT. ISBN 0-262-13269-9
[15] Hutchinson G. Evelyn 1965. The ecological theatre and the evolutionary play. Yale. The niche is the central concept in evolutionary
ecology; see especially part II The niche: an abstractly inhabited hypervolume. p26–78
[16] Dobzhansky T. 1968. On some fundamental concepts of evolutionary biology. Evolutionary biology 2, 1–34.
[17] Dobzhansky T. 1970. Genetics of the evolutionary process. Columbia, N.Y. p4–6, 79–82, 84–87
[18] Dobzhansky T. 1956. Genetics of natural populations XXV. Genetic changes in populations of Drosophila pseudoobscura and Drosphila
persimilis in some locations in California. Evolution 10, 82–92.
[19] Endler, John A. 1986. Natural selection in the wild. Princeton. p33–51: 'Fitness and adaptation'.
[20] Sober, Elliott 1984. The nature of selection: a philosophical enquiry. M.I.T.
[21] following discussion in Endler, John A. 1986. Natural selection in the wild. Princeton. p33–51: 'Fitness and adaptation'.
[22] references and details in their articles
[23] Desmond, Adrian 1989. The politics of evolution. Chicago. p31/32, footnote 18.
[24] In Candide, ou l'optimisme.
[25] Sober, Elliott 1993. Philosophy of biology. Oxford. Chapter 2
[26] Darwin, Charles. 1872. The origin of species. 6th edition, p397: Rudimentary, atrophied and aborted organs.
[27] see, for example, the discussion in Bowler, Peter H. 2003. Evolution: the history of an idea. 3rd ed, California. p86–95, especially
"Whatever the true nature of Lamark's theory, it was his mechanism of adaptation that caught the attention of later naturalists". (p90)
[28] Provine, William 1986. Sewall Wright and evolutionary biology. University of Chicago Press.
[29] Ford E.B. 1975. Ecological genetics, 4th ed. Chapman and Hall, London.
[30] Orr H. 2005. The genetic theory of adaptation: a brief history. Nature Rev. Genetics 6, 2, p119–127.
[31] Eldredge, Niles 1995. Reinventing Darwin: the great evolutionary debate. Wiley N.Y. p33
[32] Eldredge, Niles 1986. Time frames: the rethinking of Darwinian evolution and the theory of punctuated equilibria. p136, Of glaciers and
beetles.
[33] Eldredge, Niles 1995. Reinventing Darwin: the great evolutionary debate. Wiley, N.Y. p64
[34] Orr H. 2005. The genetic theory of adaptation: a brief history. Nature Rev. Genetics, 6, 119–127.
[35] Mayr, Ernst 1982. The growth of biological thought: diversity, evolution and inheritance. Harvard. Harvard. p481 (and sequence) tells how
Darwin's ideas on adaptation developed as he came to appreciate it as "a continuing dynamic process" (bottom p483).
[36] Sterelny K. & Griffiths P.E. 1999. Sex and death: an introduction to philosophy of biology. University of Chicago Press. p217 ISBN
O-226-77304-3
[37] Freeman S. & Herron J.C. 2007. Evolutionary analysis. Pearson Education. p364 ISBN 0-13-227584-8
[38] Stebbins, G. Ledyard, Jr. 1974. Flowering plants: evolution above the species level. Harvard.
[39] Carpenter GDH and Ford EB 1933. Mimicry. Methuen, London.
[40] Wickler W. 1968. Mimicry in plants and animals. World University Library, London.
[41] Moon H.P. 1976. Henry Walter Bates FRS 1825-1892: explorer, scientist and darwinian. Leicestershire Museums, Leicester.
[42] Ruxton GD, Sherratt TN and Speed MP 2004. Avoiding attack: the evolutionary ecology of crypsis, warning signals and mimicry. Oxford.
[43] Mallet, James 2001. The speciation revolution. J Evolutionary Biology 14, 887-8.
[44] http:/ / www. ucl. ac. uk/ ~ucbhdjm/ courses/ b242/ Mimic/ Mimic. html
[45] Stebbins, G. Ledyard, Jr. 1974. Flowering plants: evolution above the species level. Harvard. Contains an extensive analysis of the evolution
of adaptations in the radiation of Angiosperms.
[46] Medawar, Peter 1960. The future of Man. Methuen, London.
[47] Jacob, Francois 1977. Evolution and tinkering. Science 196 1161–1166.
[48] Mayr, Ernst 1982. The growth of biological thought: diversity, evolution and inheritance. Harvard. p589
[49] It is, of course, not possible to test selective pressures on extinct populations in any direct way. Gould, Stephen J. (1974): Origin and
function of 'bizarre' structures - antler size and skull size in 'Irish Elk', Megaloceros giganteus. Evolution 28(2): 191-220.
doi:10.2307/2407322 (First page text)
[50] Darwin, Charles 1871. The Descent of Man and selection in relation to sex. Murray, London.
[51] The case was treated by Fisher R.A. 1930. Genetical theory of natural selection. Oxford. p134–139.
[52] Cronin, Helen 1991. The ant and the peacock: altruism and sexual selection from Darwin to the present day. Cambridge.
[53] Rosenberg K.R. 2005. The evolution of modern human childbirth. Am J. Physical Anthropology 35, p89–124.
[54] Friedlander, Nancy & Jordan, David K. 1995. Obstetric implications of Neanderthal robusticity and bone density. Human Evolution
(Florence) 9: 331-342.
Adaptation 222

[55] Miller, Geoffrey 2007. Brain evolution. In Gangestad S.W. and Simpson J.A. (eds) The evolution of mind: fundamental questions and
controversies. Guildford.
[56] Huxley, Julian 1942. Evolution the modern synthesis. Allen & Unwin, London. p417
[57] Huskins C.L. 1931. The origin of Spartina townsendii. Genetica 12, 531.
[58] Lamoreux W.F and Hutt F.B. 1939. Breed differences in resistance to a deficiency in vitamin B1 in the fowl. J. Agric. Res. Washington 58,
307–315.
[59] [Dobzhansky T.] 1981. Dobzhansky's genetics of natural populations. eds Lewontin RC, Moore JA, Provine WB and Wallace B. Columbia
University Press N.Y.
[60] Egdar F. Allin and James A. Hopson 1992. Evolution of the auditory system in Synapsida ("Mammal-like reptiles" and primitive mammals)
as seen in the fossil record. Section IV (Mammals), Chapter 28, pages 587-614 in The evolutionary biology of hearing edited by Douglas B.
Webster, Richard R. Fay, and Arthur N. Popper. Springer-Verlag. ISBN 0-387-97588-8.
[61] Neil Shubin 2008. Your Inner Fish: a journey into the 3.5-billion-year history of the human body Pantheon Books 2008. ISBN
978-0-375-42447-2. Chapter 10, "Ears"
[62] Panchen, Alec. 1992. Classification, evolution and the nature of biology. Cambridge. Chapter 4 Homology and the evidence for evolution.
[63] Gould, Stephen Jay and Elizabeth S. Vrba 1982. Exaptation – a missing term in the science of form. Paleobiology 8, 1, 4–15.
[64] Charles Darwin was the first to put forward such ideas: Barrett P.H. (ed) 1987. Charles Darwin's notebooks (1836–1844). Cambridge.
[65] Wright, Sewall 1932. The roles of mutation, inbreeding, crossbreeding, and selection in evolution. In Proceedings of the Sixth International
Congress on Genetics, p355–366.
[66] Van Valen L. 1973. A new evolutionary law. Evolutionary Theory 1, 1–30.
[67] Darwin in the Origin of Species tells the story of "a web of complex relations" involving heartsease (Viola tricolor), red clover (Trifolium
pratense, humble-bees (bumblebees), mice and cats. Origin, 6th edition, p57.
[68] Koh, Lian Pih. 2004. Science, 305, 5690, 1632-1634, 10 September 2004.
[69] Price TD, Qvarnström A & Irwin DE 2003. The role of phenotypic plasticity in driving genetic evolution. Proc. Biol. Sci. 270 p1433–1440.
[70] Price T.D. 2006. Phenotypic plasticity, sexual selection and the evolution of colour patterns. J Exp Biol. 209 p2368–2376
[71] Maynard Smith J. 1993. The theory of evolution. Cambridge. 3rd ed, p33.
[72] Moore Lorna G. and Regensteiner Judith G. 1983. Adaptation to high altitude. Ann. Rev. Anthropology 12, p285–304.
[73] Maynard Smith uses the term physiologically versatile for such animals. Maynard Smith J. 1993. The theory of evolution. Cambridge. 3rd
ed, p32.
[74] Sober, Elliott 1993. Philosophy of biology. Oxford. p85–86
[75] Williams, George C. 1966. Adaptation and natural selection: a critique of some current evolutionary thought. Princeton. p8–10
[76] "The hypothesis that adaptations arise without the existence of a prior purpose, but by chance may change the fitness of an organism."
Oxford Dictionary of Zoology. But one might question the word chance, since natural selection, by its operation in particular habitats, is not a
random process (it may be a stochastic or probabilistic process, however).
[77] Pittendrigh C.S. 1958. Adaptation, natural selection and behavior. In A. Roe and George Gaylord Simpson (eds) Behavior and evolution.
Yale.
[78] Mayr, Ernst 1965. Cause and effect in biology. In D. Lerner (ed) Cause and effect. Free Press, New York. p33–50.
[79] Mayr, Ernst 1988. Toward a new philosophy of biology. Chapter 3 "The multiple meanings of teleological".
[80] Williams, George C. 1966. Adaptation and natural selection; a critique of some current evolutionary thought. Chapter 9. Princeton.
[81] Monod, Jacques 1971. Chance and necessity: an essay on the natural philosophy of modern biology. Knopf, New York. ISBN
0-394-46615-2
[82] Nagel, E. 1977. Teleology revisited: goal-directed processes in biology. Journal of Philosophy 74: 261–301.
[83] Hull D. L. 1981. Philosophy and biology. In G. Fløistad (ed) Philosophy of Science Nijhoff.
Genetic drift 223

Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant (allele) in a population due to random
sampling. The alleles in the offspring are a sample of those in the parents, and chance has a role in determining
whether a given individual survives and reproduces. A population's allele frequency is the fraction of the copies of
one gene that share a particular form.[1]
Genetic drift is an important evolutionary process, which leads to changes in allele frequencies over time. It may
cause gene variants to disappear completely, and thereby reduce genetic variation. In contrast to natural selection,
which makes gene variants more common or less common depending on their reproductive success,[2] the changes
due to genetic drift are not driven by environmental or adaptive pressures, and may be beneficial, neutral, or
detrimental to reproductive success.
The effect of genetic drift is larger in small populations, and smaller in large populations. Vigorous debates wage
among scientists over the relative importance of genetic drift compared with natural selection. Ronald Fisher held the
view that genetic drift plays at the most a minor role in evolution, and this remained the dominant view for several
decades. In 1968 Motoo Kimura rekindled the debate with his neutral theory of molecular evolution which claims
that most of the changes in the genetic material (although not necessarily changes in phenotypes) are caused by
genetic drift.[3]

Analogy with marbles in a jar

The process of genetic drift can be illustrated using 20 marbles in a jar to represent 20 organisms in a population.[4]
Half of them are red and half blue, and both colors correspond to two different alleles of one gene in the population.
In each new generation the organisms reproduce at random. To represent this reproduction, randomly select a marble
from the original jar and deposit a new marble with the same color as its "parent" into a new jar. (The selected
marble remains in the original jar.) Repeat this process until there are 20 new marbles in the second jar. The second
jar will then contain a second generation of "offspring", consisting of 20 marbles of various colors. Unless the
second jar contains exactly 10 red and 10 blue marbles, there will have been a random shift in the allele frequencies.
Repeat this process a number of times, randomly reproducing each generation of marbles to form the next. The
numbers of red and blue marbles picked each generation will fluctuate: sometimes more red, sometimes more blue.
This fluctuation is genetic drift – a change in the population's allele frequency resulting from a random variation in
the distribution of alleles from one generation to the next.
It is even possible that in any one generation no marbles of a particular color will be chosen, meaning they have no
offspring. In this example, if no red marbles are selected the jar representing the new generation will contain only
blue offspring. If this happens, the red allele has been lost permanently in the population, while the remaining blue
allele has become fixed: all future generations will be entirely blue. In small populations, fixation can occur in just a
few generations.
Genetic drift 224

In this simulation, there is fixation in the blue "allele" within five generations.

Probability and allele frequency

In probability theory, the law of large numbers predicts little change taking place over time when the population is
large. When the reproductive population is small, however, the effects of sampling error can alter the allele
frequencies significantly. Genetic drift is therefore considered to be a consequential mechanism of evolutionary
change primarily within small, isolated populations.[5]
This effect can be illustrated using a simplified example. Consider a very large colony of bacteria which are isolated
within a drop of solution. The bacteria are genetically identical except for a single gene for which there are two
different alleles. The alleles are labeled A and B. Half of the bacteria have allele A and the other half have allele B.
Thus both A and B have allele frequency 1/2.
A and B are neutral alleles, meaning they do not affect the bacteria's ability to survive and reproduce. This being the
case, all bacteria in this colony are equally likely to survive and reproduce. The drop of solution then shrinks until it
has only enough food to sustain four bacteria. All the others die without reproducing. Among the four who survive,
there are sixteen possible combinations for the A and B alleles:
(A-A-A-A), (B-A-A-A), (A-B-A-A), (B-B-A-A),
(A-A-B-A), (B-A-B-A), (A-B-B-A), (B-B-B-A),
(A-A-A-B), (B-A-A-B), (A-B-A-B), (B-B-A-B),
(A-A-B-B), (B-A-B-B), (A-B-B-B), (B-B-B-B).
If each of the combinations with the same number of A and B respectively are counted, we get the following table.
The probabilities are calculated with the slightly faulty premise that the peak population size was infinite.

A B Combinations Probability

4 0 1 1/16

3 1 4 4/16

2 2 6 6/16

1 3 4 4/16

0 4 1 1/16

The probability of any one possible combination is

where 1/2 (the probability of the A or B allele for each surviving bacterium) is multiplied four times (the total
sample size, which in this example is the total number of surviving bacteria).
Genetic drift 225

As seen in the table, the total number of possible combinations to have an equal (conserved) number of A and B
alleles is six, and its probability is 6/16. The total number of possible alternative combinations is ten, and the
probability of unequal number of A and B alleles is 10/16.
The total number of possible combinations can be represented as binomial coefficients and they can be derived from
Pascal's triangle. The probability for any one of the possible combinations can be calculated with the formula

where N is the number of bacteria and k is the number of A (or B) alleles in the combination. The function '()'
signifies the binomial coefficient and can be expressed as "N choose k". Using the formula to calculate the
probability that between them the surviving four bacteria have two A alleles and two B alleles.[6]

Genetic drift occurs when a population's allele frequencies change due to random events. In this example the
population contracted to just four random survivors, a phenomenon known as population bottleneck. The original
colony began with an equal distribution of A and B alleles but chances are that the remaining population of four
members has an unequal distribution. There is a higher probability that this surviving population will undergo drift
(10/16) than the probability it will remain the same (6/16).

Wright-Fisher model
The example given uses bacteria to illustrate the effect of sampling and probability in genetic drift. Each bacterium
has a single allele, A or B. In diploid populations consisting of N individuals there are 2N copies of each gene. An
individual can have two copies of the same allele or two different alleles. We can call the frequency of one allele p
and the frequency of the other q. The Wright-Fisher model assumes that generations do not overlap. For example,
annual plants have exactly one generation per year. Each copy of the gene found in the new generation is drawn
independently at random from all copies of the gene in the old generation. The formula to calculate the probability of
obtaining k copies of an allele that had frequency p in the last generation is then[7]

where the symbol "!" signifies the factorial function. This expression can also be formulated using the binomial
coefficient,

Moran model
The Moran model assumes overlapping generations. At each time step, one individual is chosen to reproduce and
one individual is chosen to die. So in each timestep, the number of copies of a given allele can go up by one, go
down by one, or can stay the same. This means that the transition matrix is tridiagonal, which means that
mathematical solutions are easier for the Moran model than for the Wright-Fisher model. On the other hand,
computer simulations are usually easier to perform using the Wright-Fisher model, because fewer time steps need to
be calculated. In the Moran model, it takes N timesteps to get through one generation, where N is the effective
population size. In the Wright-Fisher model, it takes just one.
In practice, the Moran model and Wright-Fisher model give qualitatively similar results, but genetic drift runs twice
as fast in the Moran model.
Genetic drift 226

Random effects other than sampling error

Random changes in allele frequencies can also be caused by other effects than sampling error, for example random
changes in selection pressure.[8]
One important alternative source of stochasticity, perhaps more important than genetic drift, is genetic draft.[9]
Genetic draft describes the way the fate of a new mutation depends on the luck of which other alleles happen to be
nearby at linked loci. Genetic draft has very different mathematical properties; unlike genetic drift, the direction of
the random change in allele frequency each generation is strongly autocorrelated instead of independent over time.

Drift and fixation

The Hardy–Weinberg principle states that within sufficiently large, randomly mating populations the allele
frequencies will tend to remain constant from one generation to the next unless the equilibrium is disturbed by
migration, genetic mutation, or selection.[10] However, there is no residual influence on this probability from the
frequency distribution of alleles in the grandparent, or any earlier, population—only that of the parent population.
The predicted distribution of alleles among the offspring is a memory-less probability as described in the Markov
property. This means that the mathematical probabilities associated with the distribution of alleles in any generation
are only derived from the distribution of alleles in the generation immediately prior. Thus when random fluctuations
result in a change of the allele frequency from the parent generation to the offspring generation, that deviation
establishes new expected values for the allele distributions in the next generation to follow.[11]
Populations do not gain new alleles from the random sampling of alleles passed to the next generation, but the
sampling can cause an existing allele to disappear. Because random sampling can remove but not replace an allele,
and because random declines or increases in allele frequency will influence the expected allele distributions for the
next following generation, genetic drift drives a population towards genetic uniformity over time. When an allele
reaches a frequency of 1 (100%) it is said to be "fixed" in the population and when an allele reaches a frequency of 0
(0%) it is lost. Once an allele becomes fixed, genetic drift comes to a halt, and the allele frequency cannot change
unless a new allele is introduced in the population via mutation or gene flow. Thus even while genetic drift is a
random, directionless process, it acts to eliminate genetic variation over time.[12]
Genetic drift 227

Time to fixation or loss

Assuming genetic drift is the only evolutionary force acting
upon an allele, at any given point in time the probability that an
allele will eventually become fixed in the population is simply
its frequency in the population at that given point in time.[13]
For example, if the frequency p for allele A is 75% and the
frequency q for allele B is 25%, then given unlimited time the
probability A will ultimately become fixed in the population is
75% and the probability that B becomes fixed is 25%.

The time needed, which is measured by the number of

generations, for fixation to occur can be estimated with
probability, and is proportional to the population size, such that
fixation is predicted to occur much more rapidly in smaller
populations.[14] Normally the effective population size, which
is smaller than the total population, is used to determine these
probabilities. The effective population size (Ne) takes into
account factors such as the level of inbreeding, the number of
organisms that are too old or young to breed, and the lower
probability that two organisms that live far apart will
reproduce.[15]

One forward-looking formula used for approximating the time

needed for a neutral allele to become fixed through genetic
drift, according to the Wright-Fisher model, is
Ten simulations of random genetic drift of a single given
allele with an initial frequency distribution 0.5 measured
over the course of 50 generations, repeated in three
reproductively synchronous populations of different sizes.
In general, alleles drift to loss or fixation (frequency of 0.0
or 1.0) significantly faster in smaller populations.

where T is the number of generations, Ne is the effective population size, and p is the initial frequency for the given
allele. The result is the number of generations expected to pass before fixation occurs for a given allele in a
population with given size (Ne) and allele frequency (p).[16]
The expected time for the neutral allele to be lost through genetic drift can be calculated as[17]

These calculations are also used to understand the impact genetic drift will have on a new allele introduced through
genetic mutation. In estimating the drift of a neutral mutation in a large population, (which can be assumed to begin
as a single occurrence of the allele and thus its initial frequency will be negligible), the formulas can be simplified
to[18]

for average number of generations needed for fixation of a neutral mutation, and
Genetic drift 228

for the average number of generations needed for the loss of a neutral mutation.[19] In cases where Ne and N are
assumed to be equal, the ratio of time-to-fixation over time-to-loss is[16]

Genetic drift versus natural selection

Although both processes drive evolution, genetic drift operates randomly while natural selection functions
non-randomly. This is because natural selection emblematizes the ecological interaction of a population, whereas
drift is regarded as a sampling procedure across successive generations without regard to fitness pressures imposed
by the environment. While natural selection is directioned, guiding evolution by impelling heritable adaptations to
the environment, genetic drift has no direction and is guided only by the mathematics of chance.[20]
As a result, drift acts upon the genotypic frequencies within a population without regard their relationship to the
phenotype. Changes to the genotype caused by genetic drift may or may not result in changes to the phenotype. In
drift each allele in a population is randomly and independently affected, yet the fluctuations in their allele
frequencies are all driven in a quantitatively similar manner. Drift is blind with respect to any advantage or
disadvantage the allele may bring. Alternatively, natural selection acts directly on the phenotype and indirectly on its
underlying genotype. Selection responds specifically to the adaptive advantage or disadvantage presented by a
phenotypic trait, and thus affects genes differentially. Selection indirectly rewards the alleles that develop adaptively
advantageous phenotypes; with an increase in reproductive success for the phenotype comes an increase in allele
frequency. By the same token, selection lowers the frequencies for alleles that cause unfavorable traits, and ignores
those which are neutral.[21]
In natural populations, genetic drift and natural selection do not act in isolation; both forces are always at play.
However, the degree to which alleles are affected by drift or selection varies according to population size. The
statistical effect of sampling error during the reproduction of alleles is much greater in small populations than in
large ones. When populations are very small, drift will predominate, and may preserve unfavorable alleles and
eliminate favorable ones (this means purifying selection has a stronger effect in species with a larger effective
population[22] ). Weak selective effects may not be seen at all, as the small changes in frequency they would produce
are overshadowed by drift.[23]
In a large population, the probability of sampling error is small and little change to the allele frequencies is expected,
even over many generations. Even weak selection forces acting upon an allele will push its frequency upwards or
downwards (depending on whether the allele's influence is beneficial or harmful). However, in cases where the allele
frequency is very small, drift can also overpower selection—even in large populations. For example, while
disadvantageous mutations are usually eliminated quickly in large populations, new advantageous mutations are
almost as vulnerable to loss through genetic drift as are neutral mutations. It is not until the allele frequency for the
advantageous mutation reaches a certain threshold that genetic drift will have little effect.[21]
Most mutations have a clear negative selective effect and cause the gametes that they occur in to disappear after a
few generations. It is possible to calculate how many percent of each generation will be removed by such mutations.
The size of the remaining population, is said to be a factor f0, the equilibrium frequency of non-deleterious alleles,
times the total population (f0 is between zero and one). When a neutral mutation spreads by drift in a population,
some of the occurrencies will be removed because they are linked to such negative mutations. That is, they are
located in chromosomes that are removed because of selection against a mutation in another part of the same
chromosome. As a consequence, the effective population size is reduced by the factor f0. This means that mutation
and selection in combination, causes the drift to have more effect. Because strength of genetic linkage varies along
the chromosome, effective population size, and thereby genetic drift, also varies. With a higher recombination rate,
Genetic drift 229

linkage decreases and with it this local effect on drift.[24] [25] This effect is visible in molecular data as a correlation
between local recombination rate and genetic diversity,[26] and negative correlation between gene density and
diversity at noncoding sites.[27]

Population bottleneck
A population bottleneck is when a
population contracts to a significantly
smaller size over a short period of time
due to some random environmental
event.[28] In a true population
bottleneck, the odds for survival of any
member of the population are purely
random, and are not improved by any
particular inherent genetic advantage.
The bottleneck can result in radical
changes in allele frequencies,
completely independent of selection.
And its impact can be sustained, even
when the bottleneck is caused by a
Changes in a population's allele frequency following a population bottleneck: the rapid
one-time event such as a natural and radical decline in population size has reduced the population's genetic variation.
catastrophe. Even when the allele
frequency of the original population is carried forward in the surviving population, a radical reduction in population
size increases the likelihood of further allele fluctuation from drift in generations to come.

A population's genetic variation can be greatly reduced by a bottleneck, and even beneficial adaptations may be
permanently eliminated.[29] The loss of variation leaves the surviving population vulnerable to any new selection
pressures such as disease, climate change or shift in the available food source, because adapting in response to
environmental changes requires sufficient genetic variation in the population for natural selection to take place.[30]
[31]

There have been many known cases of population bottleneck in the recent past. Prior to the arrival of Europeans,
North American prairies were habitat for millions of greater prairie chickens. In Illinois alone, their numbers
plummeted from about 100 million birds in 1900 to about 50 birds in the 1990s. The declines in population resulted
from hunting and habitat destruction, but the random consequence has been a loss of most of the species' genetic
diversity. DNA analysis comparing birds from the mid century to birds in the 1990s documents a steep decline in the
genetic variation in just in the latter few decades. Currently the greater prairie chicken is experiencing low
reproductive success.[32]
Over-hunting also caused a severe population bottleneck in the northern elephant seal in the 19th century. Their
resulting decline in genetic variation can be deduced by comparing it to that of the southern elephant seal which were
not so aggressively hunted.[33]
Genetic drift 230

Founder effect
The founder effect is a special case of
genetic drift, occurring when a small
group in a population splinters off
from the original population and forms
a new one. The random sample of
alleles in the just formed new colony is
expected to grossly misrepresent the
original population in at least some
respects.[34] It is even possible that the
number of alleles for some genes in the
original population is larger than the
number of gene copies in the founders,
making complete representation
When very few members of a population migrate to form a separate new population, the
founder effect occurs. For a period after the foundation, the small population experiences impossible. When a newly formed
intensive drift. In the figure this results in fixation of the red allele. colony is small, its founders can
strongly affect the population's genetic
make-up far into the future.

A well documented example is found in the Amish migration to Pennsylvania in 1744. Two members of the new
colony shared the recessive allele for Ellis–van Creveld syndrome. Members of the colony and their descendants
tend to be religious isolates and remain relatively insular. As a result of many generations of inbreeding, Ellis-van
Creveld syndrome is now much more prevalent among the Amish than in the general population.[21] [35]
The difference in gene frequencies between the original population and colony may also trigger the two groups to
diverge significantly over the course of many generations. As the difference, or genetic distance, increases, the two
separated populations may become distinct, both genetically and phenetically, although not only genetic drift but
also natural selection, gene flow and mutation will all contribute to this divergence. This potential for relatively rapid
changes in the colony's gene frequency led most scientists to consider the founder effect (and by extension, genetic
drift) a significant driving force in the evolution of new species. Sewall Wright was the first to attach this
significance to random drift and small, newly isolated populations with his shifting balance theory of speciation.[36]
Following after Wright, Ernst Mayr created many persuasive models to show that the decline in genetic variation and
small population size following the founder effect were critically important for new species to develop.[37] However,
there is much less support for this view today since the hypothesis has been tested repeatedly through experimental
research and the results have been equivocal at best.[38]

History of the concept

The concept for genetic drift was first introduced by one of the founders in the field of population genetics, Sewall
Wright. His first use of the term "drift" was in 1929,[39] though at the time he was using it in the sense of a directed
process of change, or natural selection. Later that year he used it to refer to a purely random process, or change due
to the effects of sampling error. It came to be known as the "Sewall-Wright effect", though he was never entirely
comfortable to see his name given to it. He preferred "drifting at random", and "drift" came to be adopted as a
technical term in the stochastic sense exclusively.[40]
In the early days of the modern evolutionary synthesis, scientists were just beginning to blend the new science of
population genetics with Charles Darwin's theory of natural selection. Working within this new framework, Wright
focused on the effects of inbreeding on small relatively isolated populations. He introduced the concept of an
adaptive landscape in which phenomena such as cross breeding and genetic drift in small populations could push
Genetic drift 231

them away from adaptive peaks, which would in turn allow natural selection to push them towards new adaptive
peaks.[41] Wright thought smaller populations were more suited for natural selection because "inbreeding was
sufficiently intense to create new interaction systems through random drift but not intense enough to cause random
nonadaptive fixation of genes."[40]
Wright's views on the role of genetic drift in the evolutionary scheme were controversial almost from the very
beginning. One of the most vociferous and influential critics was colleague Ronald Fisher. Fisher conceded genetic
drift played some role in evolution, but an insignificant one. Fisher has been accused of misunderstanding Wright's
views because in his criticisms Fisher seemed to argue Wright had rejected selection almost entirely. To Fisher,
viewing the process of evolution as a long, steady, adaptive progression was the only way to explain the ever
increasing complexity from simpler forms. But the debates have continued between the "gradualists" and those who
lean more toward the Wright model of evolution where selection and drift together play an important role.[2]
In 1968,[42] population geneticist Motoo Kimura rekindled the debate with his neutral theory of molecular evolution,
which claims that most of the genetic changes are caused by genetic drift acting on neutral mutations.[3]

See also
• Allopatric speciation
• Antigenic drift
• Gene pool
• Small population size

Notes
[1] Futuyma, Douglas (1998). Evolutionary Biology. Sinauer Associates. p. Glossary. ISBN 0-87893-189-9.
[2] Avers, Charlotte (1989). Process and Pattern in Evolution. Oxford University Press.
[3] Futuyma, Douglas (1998). Evolutionary Biology. Sinauer Associates. p. 320. ISBN 0-87893-189-9.
[4] "Evolution 101:Sampling Error and Evolution" (http:/ / evolution. berkeley. edu/ evosite/ evo101/ IIID1Samplingerror. shtml). University of
California Berkeley. . Retrieved 2009-11-01.
[5] Zimmer, Carl (2002). Evolution : The Triumph of an Idea. New York, NY: Perennial. pp. 364. ISBN 0-06-095850-2.
[6] Walker J. "Introduction to Probability and Statistics" (http:/ / www. fourmilab. ch/ rpkp/ experiments/ statistics. html). The
RetroPsychoKinesis Project. Fourmilab. . Retrieved 2009-11-17.
[7] Hartl, Daniel (2007). Principles of Population Genetics. Sinauer Associates. p. 102. ISBN 978-0-87893-308-2.
[8] Li, Wen-Hsiung; Dan Graur (1991). Fundamentals of Molecular Evolution. Sinauer Associates. p. 28. ISBN 0-87893-452-9.
[9] Gillespie, John H. (2001). "Is the population size of a species relevant to its evolution?". Evolution 55 (11): 2161–2169. PMID 11794777.
[10] Hartwell el al, Leland (2004). Genetics: From Genes to Genomes; 2nd edition. McGraw Hill. p. 680. ISBN 0-07-246248-5.
[11] Hartl, Daniel; Andrew Clark (2007). Principles of Population Genetics. Sinauer Associates. p. 102. ISBN 978-0-87893-308-2.
[12] Li, Wen-Hsiung; Dan Graur (1991). Fundamentals of Molecular Evolution. Sinauer Associates. p. 29. ISBN 0-87893-452-9.
[13] Futuyma, Douglas (1998). Evolutionary Biology. Sinauer Associates. p. 300. ISBN 0-87893-189-9.
[14] Otto S, Whitlock M (1 June 1997). "The probability of fixation in populations of changing size" (http:/ / www. pubmedcentral. nih. gov/
articlerender. fcgi?tool=pubmed& pubmedid=9178020). Genetics 146 (2): 723–33. PMID 9178020. PMC 1208011. .
[15] Charlesworth B (March 2009). "Fundamental concepts in genetics: Effective population size and patterns of molecular evolution and
variation". Nat. Rev. Genet. 10 (3): 195–205. doi:10.1038/nrg2526. PMID 19204717.
[16] Hedrick, Philip W. (2004). Genetics of Populations. Jones and Bartlett Publishers. pp. 737. ISBN 0763747726.
[17] Daniel Hartl, Andrew Clark (2007). Principles of Population Genetics, 4th edition. Sinauer Associates. p. 112. ISBN 978-0-87893-308-2.
[18] Wen-Hsiung Li, Dan Graur (1991). Fundamentals of Molecular Evolution. Sinauer Associates. p. 33. ISBN 978-0-87893-452-9.
[19] Kimura, Motoo; Ohta, Tomoko (2001). Theoretical Aspects of Population Genetics. Princeton University Press. pp. 232. ISBN 0691080984.
[20] "Natural Selection: How Evolution Works (An interview with Douglas Futuyma, see answer to question Is natural selection the only
mechanism of evolution?)" (http:/ / www. actionbioscience. org/ evolution/ futuyma. html). ActionBioscience.org. . Retrieved 2009-11-24.
[21] Cavalli-Sforza, L. L.; Menozzi, Paolo; Piazza, Alberto (1996). The history and geography of human genes. Princeton, N.J.: Princeton
University Press. pp. 413. ISBN 0-691-02905-9.
[22] Small KS, Brudno M, Hill MM, Sidow A (March 2007). "Extreme genomic variation in a natural population" (http:/ / www. pnas. org/
content/ 104/ 13/ 5698. long). Proc. Natl. Acad. Sci. U.S.A. 104 (13): 5698–703. doi:10.1073/pnas.0700890104. PMID 17372217.
PMC 1838466. .
[23] Simpson, George Gaylord (1967). The Meaning of Evolution (Second ed.). Yale University Press.
Genetic drift 232

[24] Golding B (1994). Non-neutral evolution: theories and molecular data. Springer. pp. 46. ISBN 978-0-412-05391-7.
[25] Charlesworth B, Morgan MT, Charlesworth D (August 1993). "The effect of deleterious mutations on neutral molecular variation" (http:/ /
www. genetics. org/ cgi/ reprint/ 134/ 4/ 1289). Genetics 134 (4): 1289–303. PMID 8375663. PMC 1205596. .
[26] Presgraves DC (September 2005). "Recombination enhances protein adaptation in Drosophila melanogaster". Curr. Biol. 15 (18): 1651–6.
doi:10.1016/j.cub.2005.07.065. PMID 16169487.
[27] Nordborg M, Hu TT, Ishino Y, et al. (July 2005). "The pattern of polymorphism in Arabidopsis thaliana" (http:/ / www. pubmedcentral. nih.
gov/ articlerender. fcgi?tool=pmcentrez& artid=1135296). PLoS Biol. 3 (7): e196. doi:10.1371/journal.pbio.0030196. PMID 15907155.
PMC 1135296.
[28] Population Bottleneck | Macmillan Genetics (http:/ / www. bookrags. com/ research/ population-bottleneck-gen-03/ )
[29] Futuyma, Douglas (1998). Evolutionary Biology. Sinauer Associates. pp. 303–304. ISBN 0-87893-189-9.
[30] O'Corry-Crowe G (2008). "Climate change and the molecular ecology of arctic marine mammals" (http:/ / www. esajournals. org/ doi/ full/
10. 1890/ 06-0795. 1). Ecological Applications 18 (2 Suppl): S56–S76. doi:10.1890/06-0795.1. PMID 18494363. .
[31] Cornuet JM, Luikart G (1996). "Description and power analysis of two tests for detecting recent population bottlenecks from allele
frequency data" (http:/ / www. pubmedcentral. nih. gov/ articlerender. fcgi?tool=pmcentrez& artid=1207747). Genetics 144 (4): 2001–14.
PMID 8978083. PMC 1207747.
[32] Hillis, David M.; Sadava, David E.; Heller, Craig H.; Orians, Gordon H.; Purves, William K. (2006). "Chs. 1, 21–33, 52–57". Life: The
Science of Biology. II: Evolution, Diversity and Ecology. San Francisco: W. H. Freeman. pp. 1251. ISBN 9780716798569.
[33] "Evolution 101: Bottlenecks and Founder Effects" (http:/ / evolution. berkeley. edu/ evosite/ evo101/ IIID3Bottlenecks. shtml). University of
California, Berkeley. . Retrieved 2009-04-07.
[34] Neill, Campbell (1996). Biology; Fourth edition. The Benjamin/Cummings Publishing Company. p. 423. ISBN 0-8053-1940-9.
[35] "Genetic Drift and the Founder Effect" (http:/ / www. pbs. org/ wgbh/ evolution/ library/ 06/ 3/ l_063_03. html). Evolution. Public Broadcast
System. . Retrieved 2009-04-07.
[36] Wade, Michael S.; Wolf, Jason; Brodie, Edmund D. (2000). Epistasis and the evolutionary process. Oxford [Oxfordshire]: Oxford
University Press. p. 330. ISBN 0-19-512806-0.
[37] Mayr, Ernst, Jody Hey, Walter M. Fitch, Francisco José Ayala (2005). Systematics and the Origin of Species: on Ernst Mayr's 100th
anniversary (Illustrated ed.). National Academies Press. p. 367. ISBN 9780309095365.
[38] Howard, Daniel J.; Berlocher, Steward H. (1998). Endless Forms (Illustrated ed.). United States: Oxford University Press. p. 470.
ISBN 9780195109016.
[39] Wright S (1929). "The evolution of dominance". The American Naturalist 63 (689): 556–61. doi:10.1086/280290.
[40] Stevenson, Joan C. (1991). Dictionary of Concepts in Physical Anthropology. Westport, Conn: Greenwood Press. ISBN 0-313-24756-0.
[41] Larson, Edward J. (2004). Evolution: The Remarkable History of a Scientific Theory. Modern Library. ISBN 978-0679642886.
[42] Kimura M (1968). "Evolutionary rate at the molecular level". Nature 217 (5129): 624–26. doi:10.1038/217624a0. PMID 5637732.

External links
• The TalkOrigins Archive (http://www.talkorigins.org/faqs/genetic-drift.html)
• Genetic drift illustrations in Barton et al. (http://www.evolution-textbook.org/content/free/figures/ch15.
html)
Gene flow 233

Gene flow
In population genetics, gene flow (also known as gene migration) is the transfer of alleles of genes from one
population to another.
Migration into or out of a population may be responsible for a marked change in allele frequencies (the proportion of
members carrying a particular variant of a gene). Immigration may also result in the addition of new genetic variants
to the established gene pool of a particular species or population.
There are a number of factors that affect the rate of gene flow between different populations. One of the most
significant factors is mobility, as greater mobility of an individual tends to give it greater migratory potential.
Animals tend to be more mobile than plants, although pollen and seeds may be carried great distances by animals or
wind.
Maintained gene flow between two populations can also lead to a combination of the two gene pools, reducing the
genetic variation between the two groups. It is for this reason that gene flow strongly acts against speciation, by
recombining the gene pools of the groups, and thus, repairing the developing differences in genetic variation that
would have led to full speciation and creation of daughter species.
For example, if a species of grass grows on both sides of a highway, pollen is likely to be transported from one side
to the other and vice versa. If this pollen is able to fertilize the plant where it ends up and produce viable offspring,
then the alleles in the pollen have effectively been able to move from the population on one side of the highway to
the other.

Barriers to gene flow

Physical barriers to gene flow are usually, but not always, natural. They may include impassable mountain ranges,
oceans, or vast deserts. In some cases, they can be artificial, man-made barriers, such as the Great Wall of China,
which has hindered the gene flow of native plant populations[1] . Samples of the same species which grow on either
side have been shown to have developed genetic differences, because there is little to no gene flow to provide
recombination of the gene pools.
Barriers to gene flow need not always be physical. Species can live in the same environment, yet show very limited
gene flow due to limited hybridization or hybridization yielding unfit hybrids.

Gene flow in humans

Gene flow has been observed in humans. For example, in the United States, gene flow was observed between a white
European population and a black West African population, which were recently brought together. In West Africa,
where malaria is prevalent, the Duffy antigen provides some resistance to the disease, and this allele is thus present
in nearly all of the West African population. In contrast, Europeans have either the allele Fya or Fyb, because
malaria is almost non-existent. By measuring the frequencies of the West African and European groups, scientists
found that the allele frequencies became mixed in each population because of movement of individuals. It was also
found that this gene flow between European and West African groups is much greater in the Northern U.S. than in
the South.
Gene flow 234

Gene flow between species

Gene flow can occur between species, either through hybridization or gene transfer from bacteria or virus to new
hosts.
Gene transfer, defined as the movement of genetic material across species boundaries, which includes horizontal
gene transfer, antigenic shift, and reassortment is sometimes an important source of genetic variation. Viruses can
transfer genes between species [2]. Bacteria can incorporate genes from other dead bacteria, exchange genes with
living bacteria, and can exchange plasmids across species boundaries [3]. "Sequence comparisons suggest recent
horizontal transfer of many genes among diverse species including across the boundaries of phylogenetic "domains".
Thus determining the phylogenetic history of a species can not be done conclusively by determining evolutionary
trees for single genes." [4]
Biologist Gogarten suggests "the original metaphor of a tree no longer fits the data from recent genome research".
Biologists [should] instead use the metaphor of a mosaic to describe the different histories combined in individual
genomes and use the metaphor of an intertwined net to visualize the rich exchange and cooperative effects of
horizontal gene transfer. [5]
"Using single genes as phylogenetic markers, it is difficult to trace organismal phylogeny in the presence of HGT
[horizontal gene transfer]. Combining the simple coalescence model of cladogenesis with rare HGT [horizontal gene
transfer] events suggest there was no single last common ancestor that contained all of the genes ancestral to those
shared among the three domains of life. Each contemporary molecule has its own history and traces back to an
individual molecule cenancestor. However, these molecular ancestors were likely to be present in different
organisms at different times." [6]

Genetic pollution
Purebred, naturally-evolved, region-specific, wild species can be threatened with extinction[7] through the process of
genetic pollution, potentially causing uncontrolled hybridization, introgression and genetic swamping. These
processes can lead to homogenization or replacement of local genotypes as a result of either a numerical and/or
fitness advantage of introduced plant or animal[8] . Nonnative species can bring about a form of extinction of native
plants and animals by hybridization and introgression either through purposeful introduction by humans or through
habitat modification, bringing previously isolated species into contact. These phenomena can be especially
detrimental for rare species coming into contact with more abundant ones. Interbreeding between the species can
cause a 'swamping' of the rarer species' gene pool, creating hybrids that drive the originally purebred native stock to
complete extinction. The extent of this facet of gene flow is not always apparent from morphological (outward
appearance) observations alone. Some degree of gene flow may be due to normal, evolutionarily constructive
processes, and all constellations of genes and genotypes cannot be preserved. That being said, hybridization with or
without introgression may threaten a rare species' existence nonetheless.[9] [10] .

Models of gene flow

Models of gene flow can be derived from population genetics, e.g. Sewall Wright's neighborhood model, Wright's
island model and the stepping stone model.

Gene flow mitigation

When cultivating genetically modified (GM) plants or livestock, it becomes necessary to prevent "genetic pollution"
i.e. their genetic modification from reaching other conventionally hybridized or wild native plant and animal
populations by using gene flow mitigation usually through unintentional cross pollination and crossbreeding.
Reasons to limit gene flow may include biosafety or agricultural co-existence, in which GM and non-GM cropping
systems work side by side.
Gene flow 235

Scientists in several large research programmes are investigating methods of limiting gene flow in plants. Among
these programmes are Transcontainer, which investigates methods for biocontainment, SIGMEA, which focuses on
the biosafety of genetically modified plants, and Co-Extra, which studies the co-existence of GM and non-GM
product chains.
Generally, there are three approaches to gene flow mitigation: keeping the genetic modification out of the pollen,
preventing the formation of pollen, and keeping the pollen inside the flower.
• The first approach requires transplastomic plants. In transplastomic plants, the modified DNA is not situated in
the cell's nucleus but is present in plastids, which are cellular compartments outside the nucleus. An example for
plastids are chloroplasts, in which photosynthesis occurs. In some plants, the pollen does not contain plastids and,
consequently, any modification located in plastids cannot be transmitted by the pollen.
• The second approach relies on male sterile plants. Male sterile plants are unable to produce functioning flowers
and therefore cannot release viable pollen. Cytoplasmic male sterile plants are known to produce higher yields.
Therefore, researchers are trying to introduce this trait to genetically modified crops.
• The third approach works by preventing the flowers from opening. This trait is called cleistogamy and occurs
naturally in some plants. Cleistogamous plants produce flowers which either open only partly or not at all.
However, it remains unclear how reliable cleistogamy is for gene flow mitigation: a Co-Extra research project on
rapeseed investigating the matter has published preliminary results which cast doubt on the attainment of a high
degree of reliability.

See also
• Biological dispersal
• Genetic erosion
• Genetic admixture

External links
• Co-Extra research on gene flow mitigation [11]
• Transcontainer research on biocontainment [12]
• SIGMEA research on the biosafety of GMOs: http://sigmea.dyndns.org [13]

References
[1] http:/ / www. nature. com/ hdy/ journal/ v90/ n3/ full/ 6800237a. html
[2] http:/ / 66. 102. 7. 104/ search?q=cache:tpICVNWaTbgJ:non. fiction. org/ lj/ community/ ref_courses/ 3484/ enmicro. pdf+ sex+ evolution+
%22Horizontal+ gene+ transfer%22+ -human+ Conjugation+ RNA+ DNA& hl=en
[3] http:/ / www2. nau. edu/ ~bah/ BIO471/ Reader/ Pennisi_2003. pdf
[4] http:/ / opbs. okstate. edu/ ~melcher/ MG/ MGW3/ MG334. html
[5] http:/ / www. esalenctr. org/ display/ confpage. cfm?confid=10& pageid=105& pgtype=1
[6] http:/ / web. uconn. edu/ gogarten/ articles/ TIG2004_cladogenesis_paper. pdf
[7] Hybridization and Introgression; Extinctions; from "The evolutionary impact of invasive species; by H. A. Mooney and E. E. Cleland" Proc
Natl Acad Sci U S A. 2001 May 8; 98(10): 5446–5451. doi: 10.1073/pnas.091093398. Proc Natl Acad Sci U S A, v.98(10); May 8, 2001, The
National Academy of Sciences (http:/ / www. pubmedcentral. nih. gov/ articlerender. fcgi?artid=33232)
[8] Glossary: definitions from the following publication: Aubry, C., R. Shoal and V. Erickson. 2005. Grass cultivars: their origins, development,
and use on national forests and grasslands in the Pacific Northwest. USDA Forest Service. 44 pages, plus appendices.; Native Seed Network
(NSN), Institute for Applied Ecology, 563 SW Jefferson Ave, Corvallis, OR 97333, USA (http:/ / www. nativeseednetwork. org/
article_view?id=13)
[9] EXTINCTION BY HYBRIDIZATION AND INTROGRESSION; by Judith M. Rhymer , Department of Wildlife Ecology, University of
Maine, Orono, Maine 04469, USA; and Daniel Simberloff, Department of Biological Science, Florida State University, Tallahassee, Florida
32306, USA; Annual Review of Ecology and Systematics, November 1996, Vol. 27, Pages 83-109 (doi: 10.1146/annurev.ecolsys.27.1.83)
(http:/ / arjournals. annualreviews. org/ doi/ abs/ 10. 1146/ annurev. ecolsys. 27. 1. 83), (http:/ / links. jstor. org/
sici?sici=0066-4162(1996)27<83:EBHAI>2. 0. CO;2-A#abstract)
Gene flow 236

[10] Genetic Pollution from Farm Forestry using eucalypt species and hybrids; A report for the RIRDC/L&WA/FWPRDC; Joint Venture
Agroforestry Program; by Brad M. Potts, Robert C. Barbour, Andrew B. Hingston; September 2001; RIRDC Publication No 01/114; RIRDC
Project No CPF - 3A; ISBN 0 642 58336 6; ISSN 1440-6845; Australian Government, Rural Industrial Research and Development
Corporation (http:/ / www. rirdc. gov. au/ reports/ AFT/ 01-114. pdf)
[11] http:/ / www. coextra. eu/ research_themes/ topics188. html
[12] http:/ / www. transcontainer. org/ UK
[13] http:/ / sigmea. dyndns. org

• Su, H et al. (2003) "The Great Wall of China: a physical barrier to gene flow?." Heredity, Volume 9 Pages
212-219

Mutation
Mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence
of a virus. Mutations are caused by radiation, viruses, transposons and mutagenic chemicals, as well as errors that
occur during meiosis or DNA replication.[1] [2] [3] They can also be induced by the organism itself, by cellular
processes such as hypermutation.
Mutation can result in several different types of change in DNA sequences; these can either have no effect, alter the
product of a gene, or prevent the gene from functioning properly or completely. Studies in the fly Drosophila
melanogaster suggest that if a mutation changes a protein produced by a gene, this will probably be harmful, with
about 70 percent of these mutations having damaging effects, and the remainder being either neutral or weakly
beneficial.[4] Due to the damaging effects that mutations can have on cells, organisms have evolved mechanisms
such as DNA repair to remove mutations.[1] Therefore, the optimal mutation rate for a species is a trade-off between
costs of a high mutation rate, such as deleterious mutations, and the metabolic costs of maintaining systems to reduce
the mutation rate, such as DNA repair enzymes.[5] Viruses that use RNA as their genetic material have rapid
mutation rates,[6] which can be an advantage since these viruses will evolve constantly and rapidly, and thus evade
the defensive responses of e.g. the human immune system.[7]

Description
Mutations can involve large sections of DNA becoming duplicated, usually through genetic recombination.[8] These
duplications are a major source of raw material for evolving new genes, with tens to hundreds of genes duplicated in
animal genomes every million years.[9] Most genes belong to larger families of genes of shared ancestry.[10] Novel
genes are produced by several methods, commonly through the duplication and mutation of an ancestral gene, or by
recombining parts of different genes to form new combinations with new functions.[11] [12] Here, domains act as
modules, each with a particular and independent function, that can be mixed together to produce genes encoding new
proteins with novel properties.[13] For example, the human eye uses four genes to make structures that sense light:
three for color vision and one for night vision; all four arose from a single ancestral gene.[14] Another advantage of
duplicating a gene (or even an entire genome) is that this increases redundancy; this allows one gene in the pair to
acquire a new function while the other copy performs the original function.[15] [16] Other types of mutation
occasionally create new genes from previously noncoding DNA.[17] [18]
Changes in chromosome number may involve even larger mutations, where segments of the DNA within
chromosomes break and then rearrange. For example, two chromosomes in the Homo genus fused to produce human
chromosome 2; this fusion did not occur in the lineage of the other apes, and they retain these separate
chromosomes.[19] In evolution, the most important role of such chromosomal rearrangements may be to accelerate
the divergence of a population into new species by making populations less likely to interbreed, and thereby
preserving genetic differences between these populations.[20]
Mutation 237

Sequences of DNA that can move about the genome, such as transposons, make up a major fraction of the genetic
material of plants and animals, and may have been important in the evolution of genomes.[21] For example, more
than a million copies of the Alu sequence are present in the human genome, and these sequences have now been
recruited to perform functions such as regulating gene expression.[22] Another effect of these mobile DNA sequences
is that when they move within a genome, they can mutate or delete existing genes and thereby produce genetic
diversity.[2]
In multicellular organisms with dedicated reproductive cells, mutations
can be subdivided into germ line mutations, which can be passed on to
descendants through their reproductive cells, and somatic mutations
(also called acquired mutations)[23] , which involve cells outside the
dedicated reproductive group and which are not usually transmitted to
descendants. If the organism can reproduce asexually through
mechanisms such as cuttings or budding the distinction can become
blurred.

For example, plants can sometimes transmit somatic mutations to their

descendants asexually or sexually where flower buds develop in
somatically mutated parts of plants. A new mutation that was not
inherited from either parent is called a de novo mutation. The source of
the mutation is unrelated to the consequence, although the
A mutation has caused this garden moss rose to
consequences are related to which cells were mutated.
produce flowers of different colors. This is a
Nonlethal mutations accumulate within the gene pool and increase the somatic mutation that may also be passed on in
the germ line.
amount of genetic variation[24] . The abundance of some genetic
changes within the gene pool can be reduced by natural selection,
while other "more favorable" mutations may accumulate and result in adaptive evolutionary changes.
For example, a butterfly may produce offspring with new mutations. The majority of these mutations will have no
effect; but one might change the color of one of the butterfly's offspring, making it harder (or easier) for predators to
see. If this color change is advantageous, the chance of this butterfly surviving and producing its own offspring are a
little better, and over time the number of butterflies with this mutation may form a larger percentage of the
population.
Neutral mutations are defined as mutations whose effects do not influence the fitness of an individual. These can
accumulate over time due to genetic drift. It is believed that the overwhelming majority of mutations have no
significant effect on an organism's fitness. Also, DNA repair mechanisms are able to mend most changes before they
become permanent mutations, and many organisms have mechanisms for eliminating otherwise permanently mutated
somatic cells.
Mutation is generally accepted by biologists as the mechanism by which natural selection acts, generating
advantageous new traits that survive and multiply in offspring as well as disadvantageous traits, in less fit offspring,
that tend to die out.
Mutation 238

Causes
Two classes of mutations are spontaneous mutations (molecular decay) and induced mutations caused by mutagens.
Spontaneous mutations on the molecular level can be caused by:
• Tautomerism – A base is changed by the repositioning of a hydrogen atom, altering the hydrogen bonding pattern
of that base resulting in incorrect base pairing during replication.
• Depurination – Loss of a purine base (A or G) to form an apurinic site (AP site).
• Deamination – Hydrolysis changes a normal base to an atypical base containing a keto group in place of the
original amine group. Examples include C → U and A → HX (hypoxanthine), which can be corrected by DNA
repair mechanisms; and 5MeC (5-methylcytosine) → T, which is less likely to be detected as a mutation because
thymine is a normal DNA base.
• Slipped strand mispairing - Denaturation of the new strand from the template during replication, followed by
renaturation in a different spot ("slipping"). This can lead to insertions or deletions.
Induced mutations on the molecular level can be
caused by:
• Chemicals
• Hydroxylamine NH2OH
• Base analogs (e.g. BrdU)
• Alkylating agents (e.g. N-ethyl-N-nitrosourea)
These agents can mutate both replicating and
non-replicating DNA. In contrast, a base analog
can only mutate the DNA when the analog is
incorporated in replicating the DNA. Each of
these classes of chemical mutagens has certain
effects that then lead to transitions, transversions,
or deletions.
• Agents that form DNA adducts (e.g. ochratoxin
A metabolites)[26]
• DNA intercalating agents (e.g. ethidium bromide)
• DNA crosslinkers
• Oxidative damage
• Nitrous acid converts amine groups on A and C
to diazo groups, altering their hydrogen bonding
patterns which leads to incorrect base pairing
A covalent adduct between benzo[a]pyrene, the major mutagen in
during replication. tobacco smoke, and DNA
[25]

• Radiation
• Ultraviolet radiation (nonionizing radiation). Two nucleotide bases in DNA – cytosine and thymine – are most
vulnerable to radiation that can change their properties. UV light can induce adjacent pyrimidine bases in a
DNA strand to become covalently joined as a pyrimidine dimer. UV radiation, particularly longer-wave UVA,
can also cause oxidative damage to DNA[27] .
• Ionizing radiation
• Viral infections[28]
DNA has so-called hotspots, where mutations occur up to 100 times more frequently than the normal mutation rate.
A hotspot can be at an unusual base, e.g., 5-methylcytosine.
Mutation rates also vary across species. Evolutionary biologists have theorized that higher mutation rates are
beneficial in some situations, because they allow organisms to evolve and therefore adapt more quickly to their
Mutation 239

environments. For example, repeated exposure of bacteria to antibiotics, and selection of resistant mutants, can result
in the selection of bacteria that have a much higher mutation rate than the original population (mutator strains).

Classification of mutation types

By effect on structure
The sequence of a gene can be altered in a
number of ways. Gene mutations have
varying effects on health depending on
where they occur and whether they alter the
function of essential proteins. Mutations in
the structure of genes can be classified as:
• Small-scale mutations, such as those
affecting a small gene in one or a few
nucleotides, including:
• Point mutations, often caused by
chemicals or malfunction of DNA
replication, exchange a single
nucleotide for another[30] . These
changes are classified as transitions or
transversions[31] . Most common is
the transition that exchanges a purine
for a purine (A ↔ G) or a pyrimidine
for a pyrimidine, (C ↔ T). A
transition can be caused by nitrous
acid, base mis-pairing, or mutagenic
base analogs such as
Illustrations of five types of chromosomal
5-bromo-2-deoxyuridine (BrdU). Less mutations.
common is a transversion, which
exchanges a purine for a pyrimidine
or a pyrimidine for a purine (C/T ↔
A/G). An example of a transversion is
adenine (A) being converted into a
cytosine (C). A point mutation can be
reversed by another point mutation, in
which the nucleotide is changed back
to its original state (true reversion) or
by second-site reversion (a
complementary mutation elsewhere
that results in regained gene
functionality). Point mutations that
occur within the protein coding region Selection of disease-causing mutations, in a standard table of the genetic code of
[29]
amino acids.
of a gene may be classified into three
kinds, depending upon what the
erroneous codon codes for:
Mutation 240

• Silent mutations: which code for the same amino acid.

• Missense mutations: which code for a different amino acid.
• Nonsense mutations: which code for a stop and can truncate the protein.
• Insertions add one or more extra nucleotides into the DNA. They are usually caused by transposable elements,
or errors during replication of repeating elements (e.g. AT repeats). Insertions in the coding region of a gene
may alter splicing of the mRNA (splice site mutation), or cause a shift in the reading frame (frameshift), both
of which can significantly alter the gene product. Insertions can be reverted by excision of the transposable
element.
• Deletions remove one or more nucleotides from the DNA. Like insertions, these mutations can alter the
reading frame of the gene. They are generally irreversible: though exactly the same sequence might
theoretically be restored by an insertion, transposable elements able to revert a very short deletion (say 1–2
bases) in any location are either highly unlikely to exist or do not exist at all. Note that a deletion is not the
exact opposite of an insertion: the former is quite random while the latter consists of a specific sequence
inserting at locations that are not entirely random or even quite narrowly defined.
• Large-scale mutations in chromosomal structure, including:
• Amplifications (or gene duplications) leading to multiple copies of all chromosomal regions, increasing the
dosage of the genes located within them.
• Deletions of large chromosomal regions, leading to loss of the genes within those regions.
• Mutations whose effect is to juxtapose previously separate pieces of DNA, potentially bringing together
separate genes to form functionally distinct fusion genes (e.g. bcr-abl). These include:
• Chromosomal translocations: interchange of genetic parts from nonhomologous chromosomes.
• Interstitial deletions: an intra-chromosomal deletion that removes a segment of DNA from a single
chromosome, thereby apposing previously distant genes. For example, cells isolated from a human
astrocytoma, a type of brain tumor, were found to have a chromosomal deletion removing sequences
between the "fused in glioblastoma" (fig) gene and the receptor tyrosine kinase "ros", producing a fusion
protein (FIG-ROS). The abnormal FIG-ROS fusion protein has constitutively active kinase activity that
causes oncogenic transformation (a transformation from normal cells to cancer cells).
• Chromosomal inversions: reversing the orientation of a chromosomal segment.
• Loss of heterozygosity: loss of one allele, either by a deletion or recombination event, in an organism that
previously had two different alleles.

By effect on function
• Loss-of-function mutations are the result of gene product having less or no function. When the allele has a
complete loss of function (null allele) it is often called an amorphic mutation. Phenotypes associated with such
mutations are most often recessive. Exceptions are when the organism is haploid, or when the reduced dosage of a
normal gene product is not enough for a normal phenotype (this is called haploinsufficiency).
• Gain-of-function mutations change the gene product such that it gains a new and abnormal function. These
mutations usually have dominant phenotypes. Often called a neomorphic mutation.
• Dominant negative mutations (also called antimorphic mutations) have an altered gene product that acts
antagonistically to the wild-type allele. These mutations usually result in an altered molecular function (often
inactive) and are characterised by a dominant or semi-dominant phenotype. In humans, Marfan syndrome is an
example of a dominant negative mutation occurring in an autosomal dominant disease. In this condition, the
defective glycoprotein product of the fibrillin gene (FBN1) antagonizes the product of the normal allele.
• Lethal mutations are mutations that lead to the death of the organisms which carry the mutations.
• A back mutation or reversion is a point mutation that restores the original sequence and hence the original
phenotype.[32]
Mutation 241

By effect on fitness
In applied genetics it is usual to speak of mutations as either harmful or beneficial.
• A harmful mutation is a mutation that decreases the fitness of the organism.
• A beneficial mutation is a mutation that increases fitness of the organism, or which promotes traits that are
desirable.
In theoretical population genetics, it is more usual to speak of such mutations as deleterious or advantageous. In the
neutral theory of molecular evolution, genetic drift is the basis for most variation at the molecular level.
• A neutral mutation has no harmful or beneficial effect on the organism. Such mutations occur at a steady rate,
forming the basis for the molecular clock.
• A deleterious mutation has a negative effect on the phenotype, and thus decreases the fitness of the organism.
• An advantageous mutation has a positive effect on the phenotype, and thus increases the fitness of the organism.
• A nearly neutral mutation is a mutation that may be slightly deleterious or advantageous, although most nearly
neutral mutations are slightly deleterious.
In reality, viewing the fitness effects of mutations in these discrete categories is an oversimplification. Attempts have
been made to infer the distribution of fitness effects using mutagenesis experiments or theoretical models applied to
molecular sequence data. However, the current distribution is still uncertain, and some aspects of the distribution
likely vary between species.[33]
By inheritance
• inheritable generic in pro-generic tissue or cells on path to be changed to gametes.
• non inheritable somatic (e.g., carcinogenic mutation)
• non inheritable post mortem aDNA mutation in decaying remains.
By pattern of inheritance The human genome contains two copies of each gene – a paternal and a maternal allele.
• A heterozygous mutation is a mutation of only one allele.
• A homozygous mutation is an identical mutation of both the paternal and maternal alleles.
• Compound heterozygous mutations or a genetic compound comprises two different mutations in the paternal
and maternal alleles.[34]
• A wildtype or homozygous non-mutated organism is one in which neither allele is mutated. (Just not a
mutation)

By impact on protein sequence

• A frameshift mutation is a mutation caused by insertion or deletion of a number of nucleotides that is not evenly
divisible by three from a DNA sequence. Due to the triplet nature of gene expression by codons, the insertion or
deletion can disrupt the reading frame, or the grouping of the codons, resulting in a completely different
translation from the original. The earlier in the sequence the deletion or insertion occurs, the more altered the
protein produced is.
• A nonsense mutation is a point mutation in a sequence of DNA that results in a premature stop codon, or a
nonsense codon in the transcribed mRNA, and possibly a truncated, and often nonfunctional protein product.
• Missense mutations or nonsynonymous mutations are types of point mutations where a single nucleotide is
changed to cause substitution of a different amino acid. This in turn can render the resulting protein
nonfunctional. Such mutations are responsible for diseases such as Epidermolysis bullosa, sickle-cell disease, and
SOD1 mediated ALS (Boillée 2006, p. 39).
• A neutral mutation is a mutation that occurs in an amino acid codon which results in the use of a different, but
chemically similar, amino acid. The similarity between the two is enough that little or no change is often rendered
in the protein. For example, a change from AAA to AGA will encode lysine, a chemically similar molecule to the
Mutation 242

intended arginine.
• Silent mutations are mutations that do not result in a change to the amino acid sequence of a protein. They may
occur in a region that does not code for a protein, or they may occur within a codon in a manner that does not alter
the final amino acid sequence. The phrase silent mutation is often used interchangeably with the phrase
synonymous mutation; however, synonymous mutations are a subcategory of the former, occurring only within
exons. The name silent could be a misnomer. For example, a silent mutation in the exon/intron border may lead to
alternative splicing by changing the splice site (see Splice site mutation), thereby leading to a changed protein.

Special classes
• Conditional mutation is a mutation that has wild-type (or less severe) phenotype under certain "permissive"
environmental conditions and a mutant phenotype under certain "restrictive" conditions. For example, a
temperature-sensitive mutation can cause cell death at high temperature (restrictive condition), but might have no
deleterious consequences at a lower temperature (permissive condition).

Nomenclature
Nomenclature of mutations specify the type of mutation and base or amino acid changes.
• Nucleotide substitution (e.g. 76A>T) - The number is the position of the nucleotide from the 5' end, the first letter
represents the wild type nucleotide, and the second letter represents the nucleotide which replaced the wild type.
In the given example, the adenine at the 76th position was replaced by a thymine.
• If it becomes necessary to differentiate between mutations in genomic DNA, mitochondrial DNA, and RNA, a
simple convention is used. For example, if the 100th base of a nucleotide sequence mutated from G to C, then
it would be written as g.100G>C if the mutation occurred in genomic DNA, m.100G>C if the mutation
occurred in mitochondrial DNA, or r.100g>c if the mutation occurred in RNA. Note that for mutations in
RNA, the nucleotide code is written in lower case.
• Amino acid substitution (e.g. D111E) – The first letter is the one letter code of the wild type amino acid, the
number is the position of the amino acid from the N terminus, and the second letter is the one letter code of the
amino acid present in the mutation. Nonsense mutations are represented with an X for the second amino acid (e.g.
D111X).
• Amino acid deletion (e.g. ΔF508) – The Greek letter Δ (delta) indicates a deletion. The letter refers to the amino
acid present in the wild type and the number is the position from the N terminus of the amino acid were it to be
present as in the wild type.

Harmful mutations
Changes in DNA caused by mutation can cause errors in protein sequence, creating partially or completely
non-functional proteins. To function correctly, each cell depends on thousands of proteins to function in the right
places at the right times. When a mutation alters a protein that plays a critical role in the body, a medical condition
can result. A condition caused by mutations in one or more genes is called a genetic disorder. Some mutations alter a
gene's DNA base sequence but do not change the function of the protein made by the gene. Studies of the fly
Drosophila melanogaster suggest that if a mutation does change a protein, this will probably be harmful, with about
70 percent of these mutations having damaging effects, and the remainder being either neutral or weakly
beneficial.[35] However, studies in yeast have shown that only 7% of mutations that are not in genes are harmful.[36]
If a mutation is present in a germ cell, it can give rise to offspring that carries the mutation in all of its cells. This is
the case in hereditary diseases. On the other hand, a mutation may occur in a somatic cell of an organism. Such
mutations will be present in all descendants of this cell within the same organism, and certain mutations can cause
the cell to become malignant, and thus cause cancer[37] .
Mutation 243

Often, gene mutations that could cause a genetic disorder are repaired by the DNA repair system of the cell. Each
cell has a number of pathways through which enzymes recognize and repair mistakes in DNA. Because DNA can be
damaged or mutated in many ways, the process of DNA repair is an important way in which the body protects itself
from disease.

Beneficial mutations
Although most mutations that change protein sequences are neutral or harmful, some mutations have a positive effect
on an organism. In this case, the mutation may enable the mutant organism to withstand particular environmental
stresses better than wild-type organisms, or reproduce more quickly. In these cases a mutation will tend to become
more common in a population through natural selection.
For example, a specific 32 base pair deletion in human CCR5 (CCR5-Δ32) confers HIV resistance to homozygotes
and delays AIDS onset in heterozygotes.[38] The CCR5 mutation is more common in those of European descent. One
possible explanation of the etiology of the relatively high frequency of CCR5-Δ32 in the European population is that
it conferred resistance to the bubonic plague in mid-14th century Europe. People with this mutation were more likely
to survive infection; thus its frequency in the population increased.[39] This theory could explain why this mutation is
not found in southern Africa, where the bubonic plague never reached. A newer theory suggests that the selective
pressure on the CCR5 Delta 32 mutation was caused by smallpox instead of the bubonic plague.[40]
Another example, is Sickle cell disease which is a blood disorder in which the body produces an abnormal type of
the oxygen-carrying substance hemoglobin in the red blood cells. One-third of all indigenous inhabitants of
Sub-Saharan Africa carry the gene[41] , because in areas where malaria is common, there is a survival value in
carrying only a single sickle-cell gene (sickle cell trait).[42] Those with only one of the two alleles of the sickle-cell
disease are more resistant to malaria, since the infestation of the malaria plasmodium is halted by the sickling of the
cells which it infests.

Prion mutation
Prions are proteins and do not contain genetic material. However, prion replication has been shown to be subject to
mutation and natural selection just like other forms of replication.[43]

See also
• Aneuploidy
• Antioxidant
• Budgerigar colour genetics
• Homeobox
• Macromutation
• Muller's morphs
• Mutant
• Mutagenesis
• Polyploidy
• Robertsonian translocation
• Signature tagged mutagenesis
• Site-directed mutagenesis
• TILLING (molecular biology)
• Trinucleotide repeat expansion
Mutation 244

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[36] Doniger SW, Kim HS, Swain D, et al. (August 2008). "A catalog of neutral and deleterious polymorphism in yeast" (http:/ / www.
pubmedcentral. nih. gov/ articlerender. fcgi?tool=pmcentrez& artid=2515631). PLoS Genet. 4 (8): e1000183.
doi:10.1371/journal.pgen.1000183. PMID 18769710. PMC 2515631.
[37] Ionov Y, Peinado MA, Malkhosyan S, Shibata D, Perucho M (1993). "Ubiquitous somatic mutations in simple repeated sequences reveal a
new mechanism for colonic carcinogenesis". Nature 363 (6429): 558–61. doi:10.1038/363558a0. PMID 8505985.
[38] Sullivan, Amy D. et al. (2001). "The coreceptor mutation CCR5Δ32 influences the dynamics of HIV epidemics and is selected for by HIV"
(http:/ / www. pnas. org/ content/ 98/ 18/ 10214. full). PNAS 95 (18): 10214–10219. doi:10.1073/pnas.181325198. PMID 11517319.
PMC 56941. .
[39] "PBS:Secrets of the Dead. Case File: Mystery of the Black Death" (http:/ / www. pbs. org/ wnet/ secrets/ previous_seasons/ case_plague/
clues. html). .
[40] Galvani A, Slatkin M (2003). "Evaluating plague and smallpox as historical selective pressures for the CCR5-Δ32 HIV-resistance allele"
(http:/ / www. pubmedcentral. nih. gov/ articlerender. fcgi?tool=pmcentrez& artid=299980). Proc Natl Acad Sci USA 100 (25): 15276–9.
doi:10.1073/pnas.2435085100. PMID 14645720. PMC 299980.
[41] Sicklecell.md (http:/ / sicklecell. md)
[42] Sicklecell.md FAQ (http:/ / sicklecell. md/ faq. asp#q1): "Why is Sickle Cell Anaemia only found in Black people?
[43] 'Lifeless' prion proteins are 'capable of evolution' (http:/ / news. bbc. co. uk/ 1/ hi/ health/ 8435320. stm)

External links
• "All About Mutations" (http://hopes.stanford.edu/causes/mutation/q0.html) from the Huntington's Disease
Outreach Project for Education at Stanford
• Central Locus Specific Variation Database at the Institute of Genomics and Integrative Biology (http://miracle.
igib.res.in/variationcentral)
• The mutations chapter of the WikiBooks General Biology textbook (http://en.wikibooks.org/wiki/
General_Biology/Genetics/Mutation#Mutation)
• Examples of Beneficial Mutations (http://www.gate.net/~rwms/EvoMutations.html)
• Correcting mutation by gene therapy (http://www.genetherapynet.com)
• BBC Radio 4 In Our Time - GENETIC MUTATION - with [[Steve Jones (biologist)|Steve Jones (http://www.
bbc.co.uk/radio4/history/inourtime/rams/inourtime_20071206.ram)]] - streaming audio
Natural selection 246

Natural selection
Natural selection is the process by which traits become more or less common in a population due to consistent
effects upon the survival or reproduction of their bearers. It is a key mechanism of evolution.
The natural genetic variation within a population of organisms may cause some individuals to survive and reproduce
more successfully than others in their current environment. For example, the peppered moth exists in both light and
dark colors in the United Kingdom, but during the industrial revolution many of the trees on which the moths rested
became blackened by soot, giving the dark-colored moths an advantage in hiding from predators. This gave
dark-colored moths a better chance of surviving to produce dark-colored offspring, and in just a few generations the
majority of the moths were dark. Factors which affect reproductive success are also important, an issue which
Charles Darwin developed in his ideas on sexual selection.
Natural selection acts on the phenotype, or the observable characteristics of an organism, but the genetic (heritable)
basis of any phenotype which gives a reproductive advantage will become more common in a population (see allele
frequency). Over time, this process can result in adaptations that specialize populations for particular ecological
niches and may eventually result in the emergence of new species. In other words, natural selection is an important
process (though not the only process) by which evolution takes place within a population of organisms. As opposed
to artificial selection, in which humans favor specific traits, in natural selection the environment acts as a sieve
through which only certain variations can pass.
Natural selection is one of the cornerstones of modern biology. The term was introduced by Darwin in his influential
1859 book On the Origin of Species,[1] in which natural selection was described as analogous to artificial selection, a
process by which animals and plants with traits considered desirable by human breeders are systematically favored
for reproduction. The concept of natural selection was originally developed in the absence of a valid theory of
heredity; at the time of Darwin's writing, nothing was known of modern genetics. The union of traditional Darwinian
evolution with subsequent discoveries in classical and molecular genetics is termed the modern evolutionary
synthesis. Natural selection remains the primary explanation for adaptive evolution.

General principles
Natural variation occurs among the individuals of any population of
organisms. Many of these differences do not affect survival (such as
differences in eye color in humans), but some differences may improve
the chances of survival of a particular individual. A rabbit that runs
faster than others may be more likely to escape from predators, and
algae that are more efficient at extracting energy from sunlight will
grow faster. Individuals that have better odds for survival also have
better odds for reproduction.

If the traits that give these individuals a reproductive advantage are

also heritable, that is, passed from parent to child, then there will be a
slightly higher proportion of fast rabbits or efficient algae in the next Darwin's illustrations of beak variation in the
generation. This is known as differential reproduction. Even if the finches of the Galápagos Islands, which hold 13
reproductive advantage is very slight, over many generations any closely related species that differ most markedly
in the shape of their beaks. The beak of each
heritable advantage will become dominant in the population, due to
species is suited to its preferred food, suggesting
exponential growth. In this way the natural environment of an that beak shapes evolved by natural selection.
organism "selects" for traits that confer a reproductive advantage,
causing gradual changes or evolution of life. This effect was first described and named by Charles Darwin.
Natural selection 247

The concept of natural selection predates the understanding of genetics, which is the study of heredity. In modern
times, it is understood that selection acts on an organism's phenotype, or observable characteristics, but it is the
organism's genetic make-up or genotype that is inherited. The phenotype is the result of the genotype and the
environment in which the organism lives (see Genotype-phenotype distinction).
This is the link between natural selection and genetics, as described in the modern evolutionary synthesis. Although
a complete theory of evolution also requires an account of how genetic variation arises in the first place (such as by
mutation and sexual reproduction) and includes other evolutionary mechanisms (such as gene flow), natural selection
is still understood as a fundamental mechanism for evolution.

Nomenclature and usage

The term natural selection has slightly different definitions in different contexts. It is most often defined to operate
on heritable traits, because these are the traits that directly participate in evolution. However, natural selection is
"blind" in the sense that changes in phenotype (physical and behavioral characteristics) can give a reproductive
advantage regardless of whether or not the trait is heritable (non heritable traits can be the result of environmental
factors or the life experience of the organism).
Following Darwin's primary usage[1] the term is often used to refer to both the evolutionary consequence of blind
selection and to its mechanisms.[2] [3] It is sometimes helpful to explicitly distinguish between selection's
mechanisms and its effects; when this distinction is important, scientists define "natural selection" specifically as
"those mechanisms that contribute to the selection of individuals that reproduce", without regard to whether the basis
of the selection is heritable. This is sometimes referred to as "phenotypic natural selection".[4]
Traits that cause greater reproductive success of an organism are said to be selected for, whereas those that reduce
success are selected against. Selection for a trait may also result in the selection of other correlated traits that do not
themselves directly influence reproductive advantage. This may occur as a result of pleiotropy or gene linkage.[5]

Fitness
The concept of fitness is central to natural selection. Broadly, individuals which are more "fit" have better potential
for survival, as in the well-known phrase "survival of the fittest". However, as with natural selection above, the
precise meaning of the term is much more subtle, and Richard Dawkins manages in his later books to avoid it
entirely. (He devotes a chapter of his book, The Extended Phenotype, to discussing the various senses in which the
term is used). Modern evolutionary theory defines fitness not by how long an organism lives, but by how successful
it is at reproducing. If an organism lives half as long as others of its species, but has twice as many offspring
surviving to adulthood, its genes will become more common in the adult population of the next generation.
Though natural selection acts on individuals, the effects of chance mean that fitness can only really be defined "on
average" for the individuals within a population. The fitness of a particular genotype corresponds to the average
effect on all individuals with that genotype. Very low-fitness genotypes cause their bearers to have few or no
offspring on average; examples include many human genetic disorders like cystic fibrosis.
Since fitness is an averaged quantity, it is also possible that a favorable mutation arises in an individual that does not
survive to adulthood for unrelated reasons. Fitness also depends crucially upon the environment. Conditions like
sickle-cell anemia may have low fitness in the general human population, but because the sickle-cell trait confers
immunity from malaria, it has high fitness value in populations which have high malaria infection rates.
Natural selection 248

Types of selection
Natural selection can act on any phenotypic trait, and selective pressure can be produced by any aspect of the
environment, including sexual selection and competition with members of the same species. However, this does not
imply that natural selection is always directional and results in adaptive evolution; natural selection often results in
the maintenance of the status quo by eliminating less fit variants.
The unit of selection can be the individual or it can be another level within the hierarchy of biological organisation,
such as genes, cells, and kin groups. There is still debate about whether natural selection acts at the level of groups or
species to produce adaptations that benefit a larger, non-kin group. Selection at a different level such as the gene can
result in an increase in fitness for that gene, while at the same time reducing the fitness of the individuals carrying
that gene, in a process called intragenomic conflict. Overall, the combined effect of all selection pressures at various
levels determines the overall fitness of an individual, and hence the outcome of natural selection.
Natural selection occurs at every life stage of an individual. An
individual organism must survive until adulthood before it can
reproduce, and selection of those that reach this stage is called viability
selection. In many species, adults must compete with each other for
mates via sexual selection, and success in this competition determines
who will parent the next generation. When individuals can reproduce
more than once, a longer survival in the reproductive phase increases
the number of offspring, called survival selection.

The fecundity of both females and males (for example, giant sperm in
certain species of Drosophila)[7] can be limited via "fecundity
selection". The viability of produced gametes can differ, while The life cycle of a sexually reproducing
organism. Various components of natural
intragenomic conflicts such as meiotic drive between the haploid [6]
selection are indicated for each life stage.
gametes can result in gametic or "genic selection". Finally, the union of
some combinations of eggs and sperm might be more compatible than
others; this is termed compatibility selection.

Sexual selection
It is useful to distinguish between "ecological selection" and "sexual selection". Ecological selection covers any
mechanism of selection as a result of the environment (including relatives, e.g. kin selection, competition, and
infanticide), while "sexual selection" refers specifically to competition for mates.[8]
Sexual selection can be intrasexual, as in cases of competition among individuals of the same sex in a population, or
intersexual, as in cases where one sex controls reproductive access by choosing among a population of available
mates. Most commonly, intrasexual selection involves male–male competition and intersexual selection involves
female choice of suitable males, due to the generally greater investment of resources for a female than a male in a
single offspring. However, some species exhibit sex-role reversed behavior in which it is males that are most
selective in mate choice; the best-known examples of this pattern occur in some fishes of the family Syngnathidae,
though likely examples have also been found in amphibian and bird species.[9]
Some features that are confined to one sex only of a particular species can be explained by selection exercised by the
other sex in the choice of a mate, for example, the extravagant plumage of some male birds. Similarly, aggression
between members of the same sex is sometimes associated with very distinctive features, such as the antlers of stags,
which are used in combat with other stags. More generally, intrasexual selection is often associated with sexual
dimorphism, including differences in body size between males and females of a species.[10]
Natural selection 249

Examples of natural selection

A well-known example of natural selection in action is the development of
antibiotic resistance in microorganisms. Since the discovery of penicillin in 1928
by Alexander Fleming, antibiotics have been used to fight bacterial diseases.
Natural populations of bacteria contain, among their vast numbers of individual
members, considerable variation in their genetic material, primarily as the result
of mutations. When exposed to antibiotics, most bacteria die quickly, but some
may have mutations that make them slightly less susceptible. If the exposure to
antibiotics is short, these individuals will survive the treatment. This selective
elimination of maladapted individuals from a population is natural selection.

These surviving bacteria will then reproduce again, producing the next
generation. Due to the elimination of the maladapted individuals in the past
generation, this population contains more bacteria that have some resistance
against the antibiotic. At the same time, new mutations occur, contributing new
genetic variation to the existing genetic variation. Spontaneous mutations are
very rare, and advantageous mutations are even rarer. However, populations of
bacteria are large enough that a few individuals will have beneficial mutations. If Resistance to antibiotics is increased
though the survival of individuals
a new mutation reduces their susceptibility to an antibiotic, these individuals are
which are immune to the effects of
more likely to survive when next confronted with that antibiotic. the antibiotic, whose offspring then
Given enough time, and repeated exposure to the antibiotic, a population of inherit the resistance, creating a new
population of resistant bacteria.
antibiotic-resistant bacteria will emerge. This new changed population of
antibiotic-resistant bacteria is optimally adapted to the context it evolved in. At
the same time, it is not necessarily optimally adapted any more to the old antibiotic free environment. The end result
of natural selection is two populations that are both optimally adapted to their specific environment, while both
perform substandard in the other environment.
The widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics in clinical
use, to the point that the methicillin-resistant Staphylococcus aureus (MRSA) has been described as a "superbug"
because of the threat it poses to health and its relative invulnerability to existing drugs.[11] Response strategies
typically include the use of different, stronger antibiotics; however, new strains of MRSA have recently emerged that
are resistant even to these drugs.[12]
This is an example of what is known as an evolutionary arms race, in which bacteria continue to develop strains that
are less susceptible to antibiotics, while medical researchers continue to develop new antibiotics that can kill them. A
similar situation occurs with pesticide resistance in plants and insects. Arms races are not necessarily induced by
man; a well-documented example involves the spread of a gene in the butterfly Hypolimnas bolina suppressing
male-killing activity by Wolbachia bacteria parasites on the island of Samoa, where the spread of the gene is known
to have occurred over a period of just five years [13]

Evolution by means of natural selection

A prerequisite for natural selection to result in adaptive evolution, novel traits and speciation, is the presence of
heritable genetic variation that results in fitness differences. Genetic variation is the result of mutations,
recombinations and alterations in the karyotype (the number, shape, size and internal arrangement of the
chromosomes). Any of these changes might have an effect that is highly advantageous or highly disadvantageous,
but large effects are very rare. In the past, most changes in the genetic material were considered neutral or close to
neutral because they occurred in noncoding DNA or resulted in a synonymous substitution. However, recent research
suggests that many mutations in non-coding DNA do have slight deleterious effects.[14] [15] Although both mutation
Natural selection 250

rates and average fitness effects of mutations are dependent on the organism, estimates from data in humans have
found that a majority of mutations are slightly deleterious.[16]
By the definition of fitness, individuals with greater fitness are more
likely to contribute offspring to the next generation, while individuals
with lesser fitness are more likely to die early or fail to reproduce. As a
result, alleles which on average result in greater fitness become more
abundant in the next generation, while alleles which generally reduce
fitness become rarer. If the selection forces remain the same for many
generations, beneficial alleles become more and more abundant, until
they dominate the population, while alleles with a lesser fitness
disappear. In every generation, new mutations and re-combinations
The exuberant tail of the peacock is thought to be
arise spontaneously, producing a new spectrum of phenotypes.
the result of sexual selection by females. This
peacock is an albino; selection against albinos in Therefore, each new generation will be enriched by the increasing
nature is intense because they are easily spotted abundance of alleles that contribute to those traits that were favored by
by predators or are unsuccessful in competition selection, enhancing these traits over successive generations.
for mates.
Some mutations occur in so-called regulatory genes. Changes in these
can have large effects on the phenotype of the individual because they
regulate the function of many other genes. Most, but not all, mutations in regulatory genes result in non-viable
zygotes. Examples of nonlethal regulatory mutations occur in HOX genes in humans, which can result in a cervical
rib[17] or polydactyly, an increase in the number of fingers or toes.[18] When such mutations result in a higher fitness,
natural selection will favor these phenotypes and the novel trait will spread in the population.

Established traits are not immutable; traits that have high fitness in one
environmental context may be much less fit if environmental conditions change.
In the absence of natural selection to preserve such a trait, it will become more
variable and deteriorate over time, possibly resulting in a vestigial manifestation
of the trait, also called evolutionary baggage. In many circumstances, the
apparently vestigial structure may retain a limited functionality, or may be
co-opted for other advantageous traits in a phenomenon known as preadaptation.
A famous example of a vestigial structure, the eye of the blind mole rat, is
believed to retain function in photoperiod perception.[19]

Speciation X-ray of the left hand of a ten year

old boy with polydactyly.
Speciation requires selective mating, which result in a reduced gene flow.
Selective mating can be the result of 1. Geographic isolation, 2. Behavioral
isolation, or 3. Temporal isolation. For example, a change in the physical environment (geographic isolation by an
extrinsic barrier) would follow number 1, a change in camouflage for number 2 or a shift in mating times (i.e., one
species of deer shifts location and therefore changes its "rut") for number 3. Over time, these subgroups might
diverge radically to become different species, either because of differences in selection pressures on the different
subgroups, or because different mutations arise spontaneously in the different populations, or because of founder
effects – some potentially beneficial alleles may, by chance, be present in only one or other of two subgroups when
they first become separated. A lesser-known mechanism of speciation occurs via hybridization, well-documented in
plants and occasionally observed in species-rich groups of animals such as cichlid fishes.[20] Such mechanisms of
rapid speciation can reflect a mechanism of evolutionary change known as punctuated equilibrium, which suggests
that evolutionary change and particularly speciation typically happens quickly after interrupting long periods of
stasis.
Natural selection 251

Genetic changes within groups result in increasing incompatibility between the genomes of the two subgroups, thus
reducing gene flow between the groups. Gene flow will effectively cease when the distinctive mutations
characterizing each subgroup become fixed. As few as two mutations can result in speciation: if each mutation has a
neutral or positive effect on fitness when they occur separately, but a negative effect when they occur together, then
fixation of these genes in the respective subgroups will lead to two reproductively isolated populations. According to
the biological species concept, these will be two different species.

Historical development

Pre-Darwinian theories
Several ancient philosophers expressed the idea that nature produces a
huge variety of creatures, apparently randomly, and that only those
creatures survive that manage to provide for themselves and reproduce
successfully; well-known examples include Empedocles[21] and his
intellectual successor, Lucretius,[22] while related ideas were later
refined by Aristotle.[23] The struggle for existence was later described
by Al-Jahiz, who argued that environmental factors influence animals
to develop new characteristics to ensure survival.[24] [25] [26] Abu
Rayhan Biruni described the idea of artificial selection and argued that
nature works in much the same way.[27] Similar ideas were later
expressed by Nasir al-Din Tusi[28] and Ibn Khaldun.[29] [30] Such
classical arguments were reintroduced in the 18th century by Pierre
Louis Maupertuis[31] and others, including Charles Darwin's The modern theory of natural selection derives
grandfather Erasmus Darwin. While these forerunners had an influence from the work of Charles Darwin in the
on Darwinism, they later had little influence on the trajectory of nineteenth century.

evolutionary thought after Charles Darwin.

Until the early 19th century, the prevailing view in Western societies was that differences between individuals of a
species were uninteresting departures from their Platonic idealism (or typus) of created kinds. However, the theory
of uniformitarianism in geology promoted the idea that simple, weak forces could act continuously over long periods
of time to produce radical changes in the Earth's landscape. The success of this theory raised awareness of the vast
scale of geological time and made plausible the idea that tiny, virtually imperceptible changes in successive
generations could produce consequences on the scale of differences between species. Early 19th century
evolutionists such as Jean Baptiste Lamarck suggested the inheritance of acquired characteristics as a mechanism for
evolutionary change; adaptive traits acquired by an organism during its lifetime could be inherited by that organism's
progeny, eventually causing transmutation of species.[32] This theory has come to be known as Lamarckism and was
an influence on the anti-genetic ideas of the Stalinist Soviet biologist Trofim Lysenko.[33]

Darwin's theory
In 1859, Charles Darwin set out his theory of evolution by natural selection as an explanation for adaptation and
speciation. He defined natural selection as the "principle by which each slight variation [of a trait], if useful, is
preserved".[34] The concept was simple but powerful: individuals best adapted to their environments are more likely
to survive and reproduce. As long as there is some variation between them, there will be an inevitable selection of
individuals with the most advantageous variations. If the variations are inherited, then differential reproductive
success will lead to a progressive evolution of particular populations of a species, and populations that evolve to be
sufficiently different eventually become different species.[35]
Natural selection 252

Darwin's ideas were inspired by the observations that he had made on the Beagle voyage, and by the work of a
political economist, the Reverend Thomas Malthus, who in An Essay on the Principle of Population, noted that
population (if unchecked) increases exponentially whereas the food supply grows only arithmetically; thus inevitable
limitations of resources would have demographic implications, leading to a "struggle for existence".[36] When
Darwin read Malthus in 1838 he was already primed by his work as a naturalist to appreciate the "struggle for
existence" in nature and it struck him that as population outgrew resources, "favourable variations would tend to be
preserved, and unfavourable ones to be destroyed. The result of this would be the formation of new species."[37]
Here is Darwin's own summary of the idea, which can be found in the fourth chapter of the Origin:
If during the long course of ages and under varying conditions of life, organic beings vary at all in the several
parts of their organisation, and I think this cannot be disputed; if there be, owing to the high geometrical
powers of increase of each species, at some age, season, or year, a severe struggle for life, and this certainly
cannot be disputed; then, considering the infinite complexity of the relations of all organic beings to each other
and to their conditions of existence, causing an infinite diversity in structure, constitution, and habits, to be
advantageous to them, I think it would be a most extraordinary fact if no variation ever had occurred useful to
each being's own welfare, in the same way as so many variations have occurred useful to man. But if
variations useful to any organic being do occur, assuredly individuals thus characterised will have the best
chance of being preserved in the struggle for life; and from the strong principle of inheritance they will tend to
produce offspring similarly characterised. This principle of preservation, I have called, for the sake of brevity,
Natural Selection.
Once he had his theory "by which to work", Darwin was meticulous about gathering and refining evidence as his
"prime hobby" before making his idea public. He was in the process of writing his "big book" to present his
researches when the naturalist Alfred Russel Wallace independently conceived of the principle and described it in an
essay he sent to Darwin to forward to Charles Lyell. Lyell and Joseph Dalton Hooker decided (without Wallace's
knowledge) to present his essay together with unpublished writings which Darwin had sent to fellow naturalists, and
On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of
Selection was read to the Linnean Society announcing co-discovery of the principle in July 1858.[38] Darwin
published a detailed account of his evidence and conclusions in On the Origin of Species in 1859. In the 3rd edition
of 1861 Darwin acknowledged that others — notably William Charles Wells in 1813, and Patrick Matthew in 1831
— had proposed similar ideas, but had neither developed them nor presented them in notable scientific
publications.[39]
Darwin thought of natural selection by analogy to how farmers select crops or livestock for breeding, which he
called "artificial selection"; in his early manuscripts he referred to a 'Nature' which would do the selection. At the
time, other mechanisms of evolution such as evolution by genetic drift were not yet explicitly formulated, and
Darwin believed that selection was likely only part of the story: "I am convinced that [it] has been the main, but not
exclusive means of modification."[40] In a letter to Charles Lyell in September 1860, Darwin regretted the use of the
term "Natural Selection", preferring the term "Natural Preservation".[41] For Darwin and his contemporaries, natural
selection was essentially synonymous with evolution by natural selection. After the publication of On the Origin of
Species, educated people generally accepted that evolution had occurred in some form. However, natural selection
remained controversial as a mechanism, partly because it was perceived to be too weak to explain the range of
observed characteristics of living organisms, and partly because even supporters of evolution balked at its
"unguided" and non-progressive nature,[42] a response that has been characterized as the single most significant
impediment to the idea's acceptance.[43] However, some thinkers enthusiastically embraced natural selection; after
reading Darwin, Herbert Spencer introduced the term survival of the fittest, which became a popular summary of the
theory.[44] The fifth edition of On the Origin of Species published in 1869 included Spencer's phrase as an alternative
to natural selection, with credit given: "But the expression often used by Mr. Herbert Spencer, of the Survival of the
Fittest, is more accurate, and is sometimes equally convenient."[45] Although the phrase is still often used by
Natural selection 253

non-biologists, modern biologists avoid it because it is tautological if "fittest" is read to mean "functionally superior"
and is applied to individuals rather than considered as an averaged quantity over populations.[46]

Modern evolutionary synthesis

Natural selection relies crucially on the idea of heredity, but it was developed long before the basic concepts of
genetics. Although the Austrian monk Gregor Mendel, the father of modern genetics, was a contemporary of
Darwin's, his work would lie in obscurity until the early 20th century. Only after the integration of Darwin's theory
of evolution with a complex statistical appreciation of Gregor Mendel's 're-discovered' laws of inheritance did
natural selection become generally accepted by scientists. The work of Ronald Fisher (who developed the required
mathematical language and The Genetical Theory of Natural Selection),[2] J.B.S. Haldane (who introduced the
concept of the "cost" of natural selection),[47] Sewall Wright (who elucidated the nature of selection and
adaptation),[48] Theodosius Dobzhansky (who established the idea that mutation, by creating genetic diversity,
supplied the raw material for natural selection: see Genetics and the Origin of Species),[49] William Hamilton (who
conceived of kin selection), Ernst Mayr (who recognised the key importance of reproductive isolation for speciation:
see Systematics and the Origin of Species)[50] and many others formed the modern evolutionary synthesis. This
synthesis cemented natural selection as the foundation of evolutionary theory, where it remains today.

Impact of the idea

Darwin's ideas, along with those of Adam Smith and Karl Marx, had a profound influence on 19th century thought.
Perhaps the most radical claim of the theory of evolution through natural selection is that "elaborately constructed
forms, so different from each other, and dependent on each other in so complex a manner" evolved from the simplest
forms of life by a few simple principles. This claim inspired some of Darwin's most ardent supporters—and
provoked the most profound opposition. The radicalism of natural selection, according to Stephen Jay Gould,[51] lay
in its power to "dethrone some of the deepest and most traditional comforts of Western thought". In particular, it
challenged long-standing beliefs in such concepts as a special and exalted place for humans in the natural world and
a benevolent creator whose intentions were reflected in nature's order and design.

Cell and molecular biology

In the 19th century, Wilhelm Roux, a founder of modern embryology, wrote a book entitled « Der Kampf der Teile
im Organismus » (The struggle of parts in the organism) in which he suggested that the development of an organism
results from a Darwinian competition between the parts of the embryo, occurring at all levels, from molecules to
organs. In recent years, a modern version of this theory has been proposed by Jean-Jacques Kupiec. According to
this cellular Darwinism [52], stochasticity at the molecular level generates diversity in cell types whereas cell
interactions impose a characteristic order on the developing embryo.

Social and psychological theory

The social implications of the theory of evolution by natural selection also became the source of continuing
controversy. Friedrich Engels, a German political philosopher and co-originator of the ideology of communism,
wrote in 1872 that "Darwin did not know what a bitter satire he wrote on mankind when he showed that free
competition, the struggle for existence, which the economists celebrate as the highest historical achievement, is the
normal state of the animal kingdom".[53] Interpretation of natural selection as necessarily 'progressive', leading to
increasing 'advances' in intelligence and civilisation, was used as a justification for colonialism and policies of
eugenics, as well as broader sociopolitical positions now described as Social Darwinism. Konrad Lorenz won the
Nobel Prize in Physiology or Medicine in 1973 for his analysis of animal behavior in terms of the role of natural
selection (particularly group selection). However, in Germany in 1940, in writings that he subsequently disowned, he
used the theory as a justification for policies of the Nazi state. He wrote "... selection for toughness, heroism, and
Natural selection 254

social utility...must be accomplished by some human institution, if mankind, in default of selective factors, is not to
be ruined by domestication-induced degeneracy. The racial idea as the basis of our state has already accomplished
much in this respect."[54] Others have developed ideas that human societies and culture evolve by mechanisms that
are analogous to those that apply to evolution of species.[55]
More recently, work among anthropologists and psychologists has led to the development of sociobiology and later
evolutionary psychology, a field that attempts to explain features of human psychology in terms of adaptation to the
ancestral environment. The most prominent such example, notably advanced in the early work of Noam Chomsky
and later by Steven Pinker, is the hypothesis that the human brain is adapted to acquire the grammatical rules of
natural language.[56] Other aspects of human behavior and social structures, from specific cultural norms such as
incest avoidance to broader patterns such as gender roles, have been hypothesized to have similar origins as
adaptations to the early environment in which modern humans evolved. By analogy to the action of natural selection
on genes, the concept of memes – "units of cultural transmission", or culture's equivalents of genes undergoing
selection and recombination – has arisen, first described in this form by Richard Dawkins[57] and subsequently
expanded upon by philosophers such as Daniel Dennett as explanations for complex cultural activities, including
human consciousness.[58] Extensions of the theory of natural selection to such a wide range of cultural phenomena
have been distinctly controversial and are not widely accepted.[59]

Information and systems theory

In 1922, Alfred Lotka proposed that natural selection might be understood as a physical principle which could be
described in terms of the use of energy by a system,[60] a concept that was later developed by Howard Odum as the
maximum power principle whereby evolutionary systems with selective advantage maximise the rate of useful
energy transformation. Such concepts are sometimes relevant in the study of applied thermodynamics.
The principles of natural selection have inspired a variety of computational techniques, such as "soft" artificial life,
that simulate selective processes and can be highly efficient in 'adapting' entities to an environment defined by a
specified fitness function.[61] For example, a class of heuristic optimization algorithms known as genetic algorithms,
pioneered by John Holland in the 1970s and expanded upon by David E. Goldberg,[62] identify optimal solutions by
simulated reproduction and mutation of a population of solutions defined by an initial probability distribution.[63]
Such algorithms are particularly useful when applied to problems whose solution landscape is very rough or has
many local minima.

Genetic basis of natural selection

The idea of natural selection predates the understanding of genetics. We now have a much better idea of the biology
underlying heritability, which is the basis of natural selection.

Genotype and phenotype

See also: Genotype-phenotype distinction.
Natural selection acts on an organism's phenotype, or physical characteristics. Phenotype is determined by an
organism's genetic make-up (genotype) and the environment in which the organism lives. Often, natural selection
acts on specific traits of an individual, and the terms phenotype and genotype are used narrowly to indicate these
specific traits.
When different organisms in a population possess different versions of a gene for a certain trait, each of these
versions is known as an allele. It is this genetic variation that underlies phenotypic traits. A typical example is that
certain combinations of genes for eye color in humans which, for instance, give rise to the phenotype of blue eyes.
(On the other hand, when all the organisms in a population share the same allele for a particular trait, and this state is
stable over time, the allele is said to be fixed in that population.)
Natural selection 255

Some traits are governed by only a single gene, but most traits are influenced by the interactions of many genes. A
variation in one of the many genes that contributes to a trait may have only a small effect on the phenotype; together,
these genes can produce a continuum of possible phenotypic values.[64]

Directionality of selection
When some component of a trait is heritable, selection will alter the frequencies of the different alleles, or variants of
the gene that produces the variants of the trait. Selection can be divided into three classes, on the basis of its effect on
allele frequencies.[65]
Directional selection occurs when a certain allele has a greater fitness than others, resulting in an increase of its
frequency. This process can continue until the allele is fixed and the entire population shares the fitter phenotype. It
is directional selection that is illustrated in the antibiotic resistance example above.
Far more common is stabilizing selection (which is commonly confused with purifying selection[66] [67] ), which
lowers the frequency of alleles that have a deleterious effect on the phenotype – that is, produce organisms of lower
fitness. This process can continue until the allele is eliminated from the population. Purifying selection results in
functional genetic features, such as protein-coding genes or regulatory sequences, being conserved over time due to
selective pressure against deleterious variants.
Finally, a number of forms of balancing selection exist, which do not result in fixation, but maintain an allele at
intermediate frequencies in a population. This can occur in diploid species (that is, those that have two pairs of
chromosomes) when heterozygote individuals, who have different alleles on each chromosome at a single genetic
locus, have a higher fitness than homozygote individuals that have two of the same alleles. This is called
heterozygote advantage or overdominance, of which the best-known example is the malarial resistance observed in
heterozygous humans who carry only one copy of the gene for sickle cell anemia. Maintenance of allelic variation
can also occur through disruptive or diversifying selection, which favors genotypes that depart from the average in
either direction (that is, the opposite of overdominance), and can result in a bimodal distribution of trait values.
Finally, balancing selection can occur through frequency-dependent selection, where the fitness of one particular
phenotype depends on the distribution of other phenotypes in the population. The principles of game theory have
been applied to understand the fitness distributions in these situations, particularly in the study of kin selection and
the evolution of reciprocal altruism.[68] [69]

Selection and genetic variation

A portion of all genetic variation is functionally neutral in that it produces no phenotypic effect or significant
difference in fitness; the hypothesis that this variation accounts for a large fraction of observed genetic diversity is
known as the neutral theory of molecular evolution and was originated by Motoo Kimura. When genetic variation
does not result in differences in fitness, selection cannot directly affect the frequency of such variation. As a result,
the genetic variation at those sites will be higher than at sites where variation does influence fitness.[65] However,
after a period with no new mutation, the genetic variation at these sites will be eliminated due to genetic drift.

Mutation selection balance

Natural selection results in the reduction of genetic variation through the elimination of maladapted individuals and
consequently of the mutations that caused the maladaptation. At the same time, new mutations occur, resulting in a
mutation-selection balance. The exact outcome of the two processes depends both on the rate at which new
mutations occur and on the strength of the natural selection, which is a function of how unfavorable the mutation
proves to be. Consequently, changes in the mutation rate or the selection pressure will result in a different
mutation-selection balance.
Natural selection 256

Genetic linkage
Genetic linkage occurs when the loci of two alleles are linked, or in close proximity to each other on the
chromosome. During the formation of gametes, recombination of the genetic material results in reshuffling of the
alleles. However, the chance that such a reshuffle occurs between two alleles depends on the distance between those
alleles; the closer the alleles are to each other, the less likely it is that such a reshuffle will occur. Consequently,
when selection targets one allele, this automatically results in selection of the other allele as well; through this
mechanism, selection can have a strong influence on patterns of variation in the genome.
Selective sweeps occur when an allele becomes more common in a population as a result of positive selection. As
the prevalence of one allele increases, linked alleles can also become more common, whether they are neutral or
even slightly deleterious. This is called genetic hitchhiking. A strong selective sweep results in a region of the
genome where the positively selected haplotype (the allele and its neighbours) are essentially the only ones that exist
in the population.
Whether a selective sweep has occurred or not can be investigated by measuring linkage disequilibrium, or whether a
given haplotype is overrepresented in the population. Normally, genetic recombination results in a reshuffling of the
different alleles within a haplotype, and none of the haplotypes will dominate the population. However, during a
selective sweep, selection for a specific allele will also result in selection of neighbouring alleles. Therefore, the
presence of a block of strong linkage disequilibrium might indicate that there has been a 'recent' selective sweep near
the center of the block, and this can be used to identify sites recently under selection.
Background selection is the opposite of a selective sweep. If a specific site experiences strong and persistent
purifying selection, linked variation will tend to be weeded out along with it, producing a region in the genome of
low overall variability. Because background selection is a result of deleterious new mutations, which can occur
randomly in any haplotype, it does not produce clear blocks of linkage disequilibrium, although with low
recombination it can still lead to slightly negative linkage disequilibrium overall.[70]

See also
• Artificial selection
• Co-evolution
• Evolvability
• Gene-centered view of evolution
• Negative selection
• Unit of selection

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classictexts/ wright. asp) Proc 6th Int Cong Genet 1:356–66
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[53] Engels F (1873-86) Dialectics of Nature 3d ed. Moscow: Progress, 1964 (http:/ / www. marxists. org/ archive/ marx/ works/ 1883/ don/
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Lotka AJ (1922b) Natural selection as a physical principle (http:/ / www. pubmedcentral. nih. gov/ picrender. fcgi?artid=1085053&
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Natural selection 259

Further reading
• For technical audiences
• Gould, Stephen Jay (2002). The Structure of Evolutionary Theory. Harvard University Press.
ISBN 0-674-00613-5.
• Maynard Smith, John (1993). The Theory of Evolution: Canto Edition. Cambridge University Press.
ISBN 0-521-45128-0.
• Popper, Karl (1978) Natural selection and the emergence of mind. Dialectica 32:339-55. See (http://
mertsahinoglu.com/research/karl-popper-on-the-scientific-status-of-darwins-theory-of-evolution/)
• Sober, Elliott (1984) The Nature of Selection: Evolutionary Theory in Philosophical Focus. University of
Chicago Press.
• Williams, George C. (1966) Adaptation and Natural Selection: A Critique of Some Current Evolutionary
Thought. Oxford University Press.
• Williams George C. (1992) Natural Selection: Domains, Levels and Challenges. Oxford University Press.
• For general audiences
• Dawkins, Richard (1996) Climbing Mount Improbable. Penguin Books, ISBN 0-670-85018-7.
• Dennett, Daniel (1995) Darwin's Dangerous Idea: Evolution and the Meanings of Life. Simon & Schuster
ISBN 0-684-82471-X.
• Gould, Stephen Jay (1997) Ever Since Darwin: Reflections in Natural History. Norton, ISBN 0-393-06425-5.
• Jones, Steve (2001) Darwin's Ghost: The Origin of Species Updated. Ballantine Books ISBN 0-345-42277-5.
Also published in Britain under the title Almost like a whale: the origin of species updated. Doubleday. ISBN
1-86230-025-9.
• Lewontin, Richard (1978) Adaptation. Scientific American 239:212-30
• Weiner, Jonathan (1994) The Beak of the Finch: A Story of Evolution in Our Time. Vintage Books, ISBN
0-679-73337-X.
• Historical
• Zirkle C (1941). Natural Selection before the "Origin of Species", Proceedings of the American Philosophical
Society 84 (1), p. 71-123.
• Kohm M (2004) A Reason for Everything: Natural Selection and the English Imagination. London: Faber and
Faber. ISBN 0-571-22392-3. For review, see (http://human-nature.com/nibbs/05/wyhe.html) van Wyhe J
(2005) Human Nature Review 5:1-4

External links
• On the Origin of Species by Charles Darwin (http://www.literature.org/authors/darwin-charles/
the-origin-of-species/chapter-04.html) – Chapter 4,Natural Selection
• Natural Selection (http://www.wcer.wisc.edu/ncisla/muse/naturalselection/index.html)- Modeling for
Understanding in Science Education, University of Wisconsin
• Natural Selection (http://evolution.berkeley.edu/evolibrary/search/topicbrowse2.php?topic_id=53) from
University of Berkeley education website
• T. Ryan Gregory: Understanding Natural Selection: Essential Concepts and Common Misconceptions (http://
www.springerlink.com/content/2331741806807x22/fulltext.html) Evolution: Education and Outreach
Speciation 260

Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to
have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to
'anagenesis' or 'phyletic evolution' occurring within lineages.[1] [2] Whether genetic drift is a minor or major
contributor to speciation is the subject of much ongoing discussion. There are four geographic modes of speciation in
nature, based on the extent to which speciating populations are geographically isolated from one another: allopatric,
peripatric, parapatric, and sympatric. Speciation may also be induced artificially, through animal husbandry or
laboratory experiments. Observed examples of each kind of speciation are provided throughout.[3]

Natural speciation
All forms of natural speciation have taken place over the course of evolution; however it still remains a subject of
debate as to the relative importance of each mechanism in driving biodiversity.[4]
One example of natural speciation is the diversity of the three-spined
stickleback, a marine fish that, after the last ice age, has undergone
speciation into new freshwater colonies in isolated lakes and streams.
Over an estimated 10,000 generations, the sticklebacks show structural
differences that are greater than those seen between different genera of
fish including variations in fins, changes in the number or size of their
bony plates, variable jaw structure, and color differences.[5]

There is debate as to the rate at which speciation events occur over

The three-spined stickleback (Gasterosteus
aculeatus) geologic time. While some evolutionary biologists claim that
speciation events have remained relatively constant over time, some
palaeontologists such as Niles Eldredge and Stephen Jay Gould have argued that species usually remain unchanged
over long stretches of time, and that speciation occurs only over relatively brief intervals, a view known as
punctuated equilibrium.
Speciation 261

Allopatric
During allopatric (from the ancient Greek
allos, "other" + Greek patrā, "fatherland")
speciation, a population splits into two
geographically isolated populations (for
example, by habitat fragmentation due to
geographical change such as mountain
building or social change such as
emigration). The isolated populations then
undergo genotypic and/or phenotypic
divergence as: (a) they become subjected to
dissimilar selective pressures; (b) they
independently undergo genetic drift; (c)
different mutations arise in the two
populations. When the populations come
back into contact, they have evolved such
that they are reproductively isolated and are
no longer capable of exchanging genes.
Comparison of allopatric, peripatric, parapatric and sympatric speciation.
Observed instances
Island genetics, the tendency of small, isolated genetic pools to produce unusual traits, has been observed in many
circumstances, including insular dwarfism and the radical changes among certain famous island chains, for example
on Komodo. The Galápagos islands are particularly famous for their influence on Charles Darwin. During his five
weeks there he heard that Galápagos tortoises could be identified by island, and noticed that Mockingbirds differed
from one island to another, but it was only nine months later that he reflected that such facts could show that species
were changeable. When he returned to England, his speculation on evolution deepened after experts informed him
that these were separate species, not just varieties, and famously that other differing Galápagos birds were all species
of finches. Though the finches were less important for Darwin, more recent research has shown the birds now known
as Darwin's finches to be a classic case of adaptive evolutionary radiation.[6]

Peripatric
In peripatric speciation, a subform of allopatric speciation, new species are formed in isolated, smaller peripheral
populations that are prevented from exchanging genes with the main population. It is related to the concept of a
founder effect, since small populations often undergo bottlenecks. Genetic drift is often proposed to play a
significant role in peripatric speciation.
Observed instances
• Mayr bird fauna
• The Australian bird Petroica multicolor
• Reproductive isolation occurs in populations of Drosophila subject to population bottlenecking
The London Underground mosquito is a variant of the mosquito Culex pipiens that entered in the London
Underground in the nineteenth century. Evidence for its speciation include genetic divergence, behavioral
differences, and difficulty in mating.[7]
Speciation 262

Parapatric
In parapatric speciation, there is only partial separation of the zones of two diverging populations afforded by
geography; individuals of each species may come in contact or cross habitats from time to time, but reduced fitness
of the heterozygote leads to selection for behaviours or mechanisms that prevent their inter-breeding. Parapatric
speciation is modelled on continuous variation within a 'single', connected habitat acting as a source of natural
selection rather than the effects of isolation of habitats produced in peripatric and allopatric speciation.
Ecologists refer to parapatric and peripatric speciation in terms of ecological niches. A niche must be available in
order for a new species to be successful.
Observed instances
• Ring species
• The Larus gulls form a ring species around the North Pole.
• The Ensatina salamanders, which form a ring round the Central Valley in California.
• The Greenish Warbler (Phylloscopus trochiloides), around the Himalayas.
• the grass Anthoxanthum has been known to undergo parapatric speciation in such cases as mine contamination of
an area.

Sympatric
Sympatric speciation refers to the formation of two or more descendant species from a single ancestral species all
occupying the same geographic location.
In sympatric speciation, species diverge while inhabiting the same place. Often-cited examples of sympatric
speciation are found in insects that become dependent on different host plants in the same area.[8] [9] However, the
existence of sympatric speciation as a mechanism of speciation is still hotly contested. People have argued that the
evidences of sympatric speciation are in fact examples of micro-allopatric, or heteropatric speciation. The most
widely accepted example of sympatric speciation is that of the cichlids of Lake Nabugabo in East Africa, which is
thought to be due to sexual selection.
Until recently, there has a been a dearth of hard evidence that supports this form of speciation, with a general feeling
that interbreeding would soon eliminate any genetic differences that might appear. But there has been at least one
recent study that suggests that sympatric speciation has occurred in Tennessee cave salamanders.[10]
The three-spined sticklebacks, freshwater fishes, that have been studied by Dolph Schluter (who received his Ph.D.
for his work on Darwin's finches with Peter J. Grant) and his current colleagues in British Columbia, were once
thought to provide an intriguing example best explained by sympatric speciation. Schluter and colleagues found:
• Two different species of three-spined sticklebacks in each of five different lakes
• a large benthic species with a large mouth that feeds on large prey in the littoral zone
• a smaller limnetic species — with a smaller mouth — that feeds on the small plankton in open water
• DNA analysis indicates that each lake was colonized independently, presumably by a marine ancestor, after the
last ice age
• DNA analysis also shows that the two species in each lake are more closely related to each other than they are to
any of the species in the other lakes
• The two species in each lake are reproductively isolated; neither mates with the other.
• However, aquarium tests showed:
• the benthic species from one lake will spawn with the benthic species from the other lakes and
• likewise the limnetic species from the different lakes will spawn with each other.
• These benthic and limnetic species even display their mating preferences when presented with sticklebacks
from Japanese lakes; that is, a Canadian benthic prefers a Japanese benthic over its close limnetic cousin from
Speciation 263

its own lake.

• Their conclusion: in each lake, what began as a single population faced such competition for limited resources
that:
• disruptive selection — competition favoring fishes at either extreme of body size and mouth size over those
nearer the mean — coupled with:
• assortative mating — each size preferred mates like it — favored a divergence into two subpopulations
exploiting different food in different parts of the lake.
• The fact that this pattern of speciation occurred the same way on three separate occasions suggests strongly
that ecological factors in a sympatric population can cause speciation.
However, the DNA evidence cited above is from mitochondrial DNA (mtDNA), which can often move easily
between closely related species ("introgression") when they hybridize. A more recent study,[11] using genetic
markers from the nuclear genome, shows that limnetic forms in different lakes are more closely related to each other
(and to marine lineages) than to benthic forms in the same lake. The three-spine stickleback is now usually
considered an example of "double invasion" (a form of allopatric speciation) in which repeated invasions of marine
forms have subsequently differentiated into benthic and limnetic forms. The three-spine stickleback provides an
example of how molecular biogeographic studies that rely solely on mtDNA can be misleading, and that
consideration of the genealogical history of alleles from multiple unlinked markers (i.e. nuclear genes) is necessary
to infer speciation histories.
Sympatric speciation driven by ecological factors may also account for the extraordinary diversity of crustaceans
living in the depths of Siberia's Lake Baikal.

Speciation via polyploidization

Polyploidy is a mechanism often attributed to causing some speciation

events in sympatry. Not all polyploids are reproductively isolated from
their parental plants, so an increase in chromosome number may not
result in the complete cessation of gene flow between the incipient
polyploids and their parental diploids (see also hybrid speciation).
Polyploidy is observed in many species of both plants and animals, and
results in rapid speciation since offspring of, for example, tetraploid x
diploid matings result in triploid sterile progeny.[12] It has been Speciation via polyploidy: A diploid cell
undergoes failed meiosis, producing diploid
proposed that many of the existing plant and most animal species have gametes, which self-fertilize to produce a
undergone an event of polyploidization in their evolutionary history. tetraploid zygote.
However, reproduction is often by parthenogenesis since polyploid
animals are often sterile. [needs further editing—not true in plants]. Rare instances of polyploid mammals are
known, but most often result in prenatal death.

Hawthorn fly
One example of evolution at work is the case of the hawthorn fly, Rhagoletis pomonella, also known as the apple
maggot fly, which appears to be undergoing sympatric speciation.[13] Different populations of hawthorn fly feed on
different fruits. A distinct population emerged in North America in the 19th century some time after apples, a
non-native species, were introduced. This apple-feeding population normally feeds only on apples and not on the
historically preferred fruit of hawthorns. The current hawthorn feeding population does not normally feed on apples.
Some evidence, such as the fact that six out of thirteen allozyme loci are different, that hawthorn flies mature later in

the season and take longer to mature than apple flies; and that there is little evidence of interbreeding (researchers
have documented a 4-6% hybridization rate) suggests that sympatric speciation is occurring. The emergence of the
Speciation 264

new hawthorn fly is an example of evolution in progress.[14]

Speciation via hybrid formation

See Hybrid speciation section under the Genetics heading below.

Reinforcement (Wallace effect)

Reinforcement is the process by which natural selection increases reproductive isolation.[15] It may occur after two
populations of the same species are separated and then come back into contact. If their reproductive isolation was
complete, then they will have already developed into two separate incompatible species. If their reproductive
isolation is incomplete, then further mating between the populations will produce hybrids, which may or may not be
fertile. If the hybrids are infertile, or fertile but less fit than their ancestors, then there will be no further reproductive
isolation and speciation has essentially occurred (e.g., as in horses and donkeys.) The reasoning behind this is that if
the parents of the hybrid offspring each have naturally selected traits for their own certain environments, the hybrid
offspring will bear traits from both, therefore would not fit either ecological niche as well as either parent. The low
fitness of the hybrids would cause selection to favor assortative mating, which would control hybridization. This is
sometimes called the Wallace effect after the evolutionary biologist Alfred Russel Wallace who suggested in the late
19th century that it might be an important factor in speciation.[16] If the hybrid offspring are more fit than their
ancestors, then the populations will merge back into the same species within the area they are in contact.
Reinforcement is required for both parapatric and sympatric speciation. Without reinforcement, the geographic area
of contact between different forms of the same species, called their "hybrid zone," will not develop into a boundary
between the different species. Hybrid zones are regions where diverged populations meet and interbreed. Hybrid
offspring are very common in these regions, which are usually created by diverged species coming into secondary
contact. Without reinforcement the two species would have uncontrollable inbreeding. Reinforcement may be
induced in artificial selection experiments as described below.

Artificial speciation
New species have been created by domesticated animal husbandry, but the initial dates and methods of the initiation
of such species are not clear. For example, domestic sheep were created by hybridisation, and no longer produce
viable offspring with Ovis orientalis, one species from which they are descended.[17] Domestic cattle, on the other
hand, can be considered the same species as several varieties of wild ox, gaur, yak, etc., as they readily produce
fertile offspring with them.[18]
The best-documented creations of new species in the laboratory were performed in the late 1980s. William Rice and
G.W. Salt bred fruit flies, Drosophila melanogaster, using a maze with three different choices of habitat such as
light/dark and wet/dry. Each generation was placed into the maze, and the groups of flies that came out of two of the
eight exits were set apart to breed with each other in their respective groups. After thirty-five generations, the two
groups and their offspring were isolated reproductively because of their strong habitat preferences: they mated only
within the areas they preferred, and so did not mate with flies that preferred the other areas.[19] The history of such
attempts is described in Rice and Hostert (1993).[20]
Diane Dodd was also able to show how reproductive isolation can develop from mating preferences in Drosophila
pseudoobscura fruit flies after only eight generations using different food types, starch and maltose.[21]
Speciation 265

Dodd's experiment has been easy for many others to replicate, including with other kinds of fruit flies and foods.[22]

Genetics
Few speciation genes have been found. They usually involve the reinforcement process of late stages of speciation.
In 2008 a speciation gene causing reproductive isolation was reported.[23] It causes hybrid sterility between related
subspecies.

Hybrid speciation
Hybridization between two different species sometimes leads to a distinct phenotype. This phenotype can also be
fitter than the parental lineage and as such natural selection may then favor these individuals. Eventually, if
reproductive isolation is achieved, it may lead to a separate species. However, reproductive isolation between
hybrids and their parents is particularly difficult to achieve and thus hybrid speciation is considered an extremely
rare event. The Mariana Mallard is known to have arisen from hybrid speciation.
Hybridization without change in chromosome number is called homoploid hybrid speciation. It is considered very
rare but has been shown in Heliconius butterflies [24] and sunflowers. Polyploid speciation, which involves changes
in chromosome number, is a more common phenomenon, especially in plant species.

Gene transposition as a cause

Theodosius Dobzhansky, who studied fruit flies in the early days of genetic research in 1930s, speculated that parts
of chromosomes that switch from one location to another might cause a species to split into two different species. He
mapped out how it might be possible for sections of chromosomes to relocate themselves in a genome. Those mobile
sections can cause sterility in inter-species hybrids, which can act as a speciation pressure. In theory, his idea was
sound, but scientists long debated whether it actually happened in nature. Eventually a competing theory involving
the gradual accumulation of mutations was shown to occur in nature so often that geneticists largely dismissed the
moving gene hypothesis.[25]
However, 2006 research shows that jumping of a gene from one chromosome to another can contribute to the birth
of new species.[26] This validates the reproductive isolation mechanism, a key component of speciation.[27]
Speciation 266

Interspersed repeats
Interspersed repetitive DNA sequences function as isolating mechanisms. These repeats protect newly evolving gene
sequences from being overwritten by gene conversion, due to the creation of non-homologies between otherwise
homologous DNA sequences. The non-homologies create barriers to gene conversion. This barrier allows nascent
novel genes to evolve without being overwritten by the progenitors of these genes. This uncoupling allows the
evolution of new genes, both within gene families and also allelic forms of a gene. The importance is that this allows
the splitting of a gene pool without requiring physical isolation of the organisms harboring those gene sequences.

Human speciation
Humans have genetic similarities with chimpanzees and gorillas, suggesting common ancestors. Analysis of genetic
drift and recombination using a Markov model suggests humans and chimpanzees speciated apart 4.1 million years
ago.[28]

See also
• Extinction
• Species problem
• Heteropatry
• Chronospecies
• Koinophilia

References
[1] Cook, O. F. 1906. Factors of species-formation. Science 23:506-507.
[2] Cook, O. F. 1908. Evolution without isolation. American Naturalist 42:727-731.
[3] Observed Instances of Speciation (http:/ / www. talkorigins. org/ faqs/ faq-speciation. html) by Joseph Boxhorn. Retrieved 8 June 2009.
[4] J.M. Baker (2005). "Adaptive speciation: The role of natural selection in mechanisms of geographic and non-geographic speciation". Studies
in History and Philosophy of Biological and Biomedical Sciences 36 (2): 303–326. doi:10.1016/j.shpsc.2005.03.005. PMID 19260194.
[5] Kingsley, D.M. (January 2009) "From Atoms to Traits," Scientific American, p. 57
[6] Frank J. Sulloway (1982). "The Beagle collections of Darwin's finches (Geospizinae)". Bulletin of the British Museum (Natural History)
Zoology Series 43 (2): 49–58. available online (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=A86& pageseq=2)
[7] Katharine Byrne and Richard A Nichols (1999) "Culex pipiens in London Underground tunnels: differentiation between surface and
subterranean populations" (http:/ / www. nature. com/ hdy/ journal/ v82/ n1/ full/ 6884120a. html)
[8] Feder, J. L., X. Xie, J. Rull, S. Velez, A. Forbes, B. Leung, H. Dambroski, K. E. Filchak, and M. Aluja. 2005. Mayr, Dobzhansky, and Bush
and the complexities of sympatric speciation in Rhagoletis. Proceedings of the National Academy of Sciences, USA 1902:6573-6580
[9] Berlocher, S. H., and J. L. Feder. 2002. Sympatric speciation in phytophagous insects: moving beyond controversy? Annual Review of
Entomology 47:773-815
[10] MATTHEW L. NIEMILLER, BENJAMIN M. FITZPATRICK, BRIAN T. MILLER (2008). "Recent divergence with gene flow in
Tennessee cave salamanders (Plethodontidae: Gyrinophilus) inferred from gene genealogies". Molecular Ecology 17 (9): 2258–2275.
available online (http:/ / www. blackwell-synergy. com/ doi/ abs/ 10. 1111/ j. 1365-294X. 2008. 03750. x)
[11] E.B. TAYLOR, J.D. McPHAIL (2000). "Historical contingency and determinism interact to prime speciation in sticklebacks" (http:/ / www.
pubmedcentral. nih. gov/ articlerender. fcgi?tool=pmcentrez& artid=1690834). Proceedings of the Royal Society of London Series B 267
(1460): 2375–2384. doi:10.1098/rspb.2000.1294. PMID 11133026. PMC 1690834. (http:/ / www. jstor. org/
sici?sici=0962-8452(200012)267:1460<2375:HCAEDI>2. 0. CO;2-1& origin=ISI) available online
[12] Ramsey, J., and D. W. Schemske. 1998. Pathways, mechanisms, and rates of polyploid formation in flowering plants. Annual Review of
Ecology and Systematics 29:467-501
[13] Feder JL, Roethele JB, Filchak K, Niedbalski J, Romero-Severson J (1 March 2003). "Evidence for inversion polymorphism related to
sympatric host race formation in the apple maggot fly, Rhagoletis pomonella" (http:/ / www. genetics. org/ cgi/ pmidlookup?view=long&
pmid=12663534). Genetics 163 (3): 939–53. PMID 12663534. PMC 1462491. .
[14] Berlocher SH, Bush GL (1982). "An electrophoretic analysis of Rhagoletis (Diptera: Tephritidae) phylogeny" (http:/ / jstor. org/ stable/
2413033). Systematic Zoology 31 (2): 136–55. doi:10.2307/2413033. .
[15] Ridley, M. (2003) "Speciation — What is the role of reinforcement in speciation?" adapted from Evolution 3rd edition (Boston: Blackwell
Science) tutorial online (http:/ / www. blackwellpublishing. com/ ridley/ tutorials/ Speciation15. asp)
Speciation 267

[16] Ollerton, J. "Flowering time and the Wallace Effect" (http:/ / oldweb. northampton. ac. uk/ aps/ env/ lbrg/ journals/ papers/
OllertonHeredityCommentary2005. pdf) (PDF). Heredity, August 2005. . Retrieved 2007-05-22.
[17] Hiendleder S., et al. (2002) "Molecular analysis of wild and domestic sheep questions current nomenclature and provides evidence for
domestication from two different subspecies" Proceedings of the Royal Society B: Biological Sciences 269:893-904
[18] Nowak, R. (1999) Walker's Mammals of the World 6th ed. (Baltimore: Johns Hopkins University Press)
[19] Rice, W.R. and G.W. Salt (1988). "Speciation via disruptive selection on habitat preference: experimental evidence". The American
Naturalist 131: 911–917. doi:10.1086/284831.
[20] W.R. Rice and E.E. Hostert (1993). "Laboratory experiments on speciation: What have we learned in forty years?" (http:/ / jstor. org/ stable/
2410209). Evolution 47 (6): 1637–1653. doi:10.2307/2410209. .
[21] Dodd, D.M.B. (1989) "Reproductive isolation as a consequence of adaptive divergence in Drosophila pseudoobscura." Evolution
43:1308–1311.
[22] Kirkpatrick, M. and V. Ravigné (2002) "Speciation by Natural and Sexual Selection: Models and Experiments" The American Naturalist
159:S22–S35 DOI (http:/ / www. journals. uchicago. edu/ doi/ abs/ 10. 1086/ 338370)
[23] http:/ / www. sciencemag. org/ cgi/ content/ short/ 323/ 5912/ 376
[24] Mavarez, J.; Salazar, C.A., Bermingham, E., Salcedo, C., Jiggins, C.D. , Linares, M. (2006). "Speciation by hybridization in Heliconius
butterflies". Nature 441 (7095): 868. doi:10.1038/nature04738. PMID 16778888.
[25] University of Rochester Press Releases (http:/ / www. rochester. edu/ news/ show. php?id=2603)
[26] Masly, John P., Corbin D. Jones, Mohamed A. F. Noor, John Locke, and H. Allen Orr (September 2006). "Gene Transposition as a Cause of
Hybrid Sterility in Drosophila" (http:/ / www. sciencemag. org/ cgi/ content/ short/ 313/ 5792/ 1448). Science 313 (5792): 1448–1450.
doi:10.1126/science.1128721. PMID 16960009. . Retrieved 2007-03-18.
[27] Minkel, J.R. (September 8, 2006) "Wandering Fly Gene Supports New Model of Speciation" (http:/ / www. sciam. com/ article.
cfm?chanID=sa003& articleID=000A84DB-CA3B-1501-8A3B83414B7F0000) Science News
[28] Hobolth A, Christensen OF, Mailund T, Schierup MH (2007) "Genomic Relationships and Speciation Times of Human, Chimpanzee, and
Gorilla Inferred from a Coalescent Hidden Markov Model." (http:/ / genetics. plosjournals. org/ perlserv/ ?request=get-document& doi=10.
1371/ journal. pgen. 0030007) PLoS Genet 3(2): e7 (doi:10.1371/journal.pgen.0030007)

Further reading
• Coyne, J. A. & Orr, H. A. (2004). Speciation. Sunderlands, Massachusetts: Sinauer Associates, Inc.
ISBN 0-87893-089-2.
• Grant, V. (1981). Plant Speciation (2nd Edit. ed.). New York: Columbia University Press. ISBN 0-231-05113-1.
• Mayr, E. (1963). Animal Species and Evolution. Harvard University Press. ISBN 0-674-03750-2
• Marko, P. B. (2008). Allopatry. Oxford: Elsevier. ISBN 978-0-444-52033-3.
• White, M. J. D. (1978). Modes of Speciation. San Francisco, California: W. H. Freeman and Company.
ISBN 0-716-70284-3.
• Dedicated issue of Philosophical Transactions B on Speciation in microorganisms is freely available. (http://
publishing.royalsociety.org/microgenesis)

External links
• Observed Instances of Speciation (http://www.talkorigins.org/faqs/faq-speciation.html) from the Talk.Origins
Frequently Asked Questions (http://www.talkorigins.org/origins/faqs-qa.html)
• Speciation (http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_40), and
• Evidence for Speciation (http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_45) from Understanding
Evolution (http://evolution.berkeley.edu/evolibrary/home.php) by the University of California Museum of
Paleontology
• Speciation (http://johnhawks.net/weblog/topics/phylogeny/speciation.html) from John Hawks' Anthropology
Weblog - paleoanthropology, genetics, and evolution (http://johnhawks.net/weblog/topics/phylogeny/)
• Speciation in the context of evolution (http://evolution-of-man.info/speciation.htm)
 268

Phylogenetics

Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among various groups of organisms (for example,
species or populations), which is discovered through molecular sequencing data and morphological data matrices.
The term phylogenetics is of Greek origin from the terms phyle/phylon (φυλή/φῦλον), meaning "tribe, race," and
genetikos (γενετικός), meaning "relative to birth" from genesis (γένεσις, "birth"). Taxonomy, the classification,
identification, and naming of organisms, has been richly informed by phylogenetics but remains methodologically
and logically distinct.[1] The fields overlap however in the science of phylogenetic systematics – often called
"cladism" or "cladistics" – where only phylogenetic trees are used to delimit taxa, which represent groups of
lineage-connected individuals.[2] In biological systematics as a whole, phylogenetic analyses have become essential
in researching the evolutionary tree of life.

Construction of a phylogenetic tree

Evolution is regarded as a branching process, whereby populations are altered over time and may speciate into
separate branches, hybridize together, or terminate by extinction. This may be visualized in a phylogenetic tree.
The problem posed by phylogenetics is that genetic data are only available for living taxa, and the fossil records
(osteometric data) contains less data and more-ambiguous morphological characters.[3] A phylogenetic tree
represents a hypothesis of the order in which evolutionary events are assumed to have occurred.
Cladistics is the current method of choice to infer phylogenetic trees. The most commonly-used methods to infer
phylogenies include parsimony, maximum likelihood, and MCMC-based Bayesian inference. Phenetics, popular in
the mid-20th century but now largely obsolete, uses distance matrix-based methods to construct trees based on
overall similarity, which is often assumed to approximate phylogenetic relationships. All methods depend upon an
implicit or explicit mathematical model describing the evolution of characters observed in the species included, and
are usually used for molecular phylogeny, wherein the characters are aligned nucleotide or amino acid sequences.
Phylogenetics 269

Grouping of organisms
There are some terms that describe the
nature of a grouping in such trees. For
instance, all birds and reptiles are believed
to have descended from a single common
ancestor, so this taxonomic grouping
(yellow in the diagram below) is called
monophyletic. "Modern reptile" (cyan in the
diagram) is a grouping that contains a
common ancestor, but does not contain all
descendants of that ancestor (birds are
excluded). This is an example of a
paraphyletic group. A grouping such as
warm-blooded animals would include only
mammals and birds (red/orange in the
diagram) and is called polyphyletic because
the members of this grouping do not include
the most recent common ancestor. Phylogenetic groups, or taxa, can be monophyletic, paraphyletic, or polyphyletic.

Molecular phylogenetics
The evolutionary connections between organisms are represented graphically through phylogenetic trees. Due to the
fact that evolution takes place over long periods of time that cannot be observed directly, biologists must reconstruct
phylogenies by inferring the evolutionary relationships among present-day organisms. Fossils can aid with the
reconstruction of phylogenies; however, fossil records are often too poor to be of good help. Therefore, biologists
tend to be restricted with analysing present-day organisms to identify their evolutionary relationships. Phylogenetic
relationships in the past were reconstructed by looking at phenotypes, often anatomical characteristics. Today,
molecular data, which includes protein and DNA sequences, are used to construct phylogenetic trees.[4] The overall
goal of National Science Foundation's Assembling the Tree of Life activity (AToL) is to resolve evolutionary
relationships for large groups of organisms throughout the history of life, with the research often involving large
teams working across institutions and disciplines. Investigators are typically supported for projects in data
acquisition, analysis, algorithm development and dissemination in computational phylogenetics and
phyloinformatics. For example, RedToL aims at reconstructing the Red Algal Tree of Life.
Phylogenetics 270

Ernst Haeckel's recapitulation theory

During the late 19th century, Ernst Haeckel's
recapitulation theory, or biogenetic law, was widely
accepted. This theory was often expressed as "ontogeny
recapitulates phylogeny", i.e. the development of an
organism exactly mirrors the evolutionary development of
the species. Haeckel's early version of this hypothesis [that
the embryo mirrors adult evolutionary ancestors] has since
been rejected, and the hypothesis amended as the embryo's
development mirroring embryos of its evolutionary
ancestors. He was accused by five professors of falsifying
his images of embryos (See Ernst Haeckel). Most modern
biologists recognize numerous connections between
ontogeny and phylogeny, explain them using evolutionary
theory, or view them as supporting evidence for that
theory. Donald I. Williamson suggested that larvae and
embryos represented adults in other taxa that have been
transferred by hybridization (the larval transfer theory).[5]
[6]
However, Williamson's views do not represent
mainstream thought in molecular biology[7] , and there is a
significant body of evidence against the larval transfer
theory.[8]

Genealogical tree suggested by Haeckel (1866)

Gene transfer
In general, organisms can inherit genes in two ways: vertical gene transfer and horizontal gene transfer. Vertical
gene transfer is the passage of genes from parent to offspring, and horizontal gene transfer or lateral gene transfer
occurs when genes jump between unrelated organisms, a common phenomenon in prokaryotes.
Horizontal gene transfer has complicated the determination of phylogenies of organisms, and inconsistencies in
phylogeny have been reported among specific groups of organisms depending on the genes used to construct
evolutionary trees.
Carl Woese came up with the three-domain theory of life (eubacteria, archaea and eukaryotes) based on his
discovery that the genes encoding ribosomal RNA are ancient and distributed over all lineages of life with little or no
horizontal gene transfer. Therefore, rRNAs are commonly recommended as molecular clocks for reconstructing
phylogenies.
This has been particularly useful for the phylogeny of microorganisms, to which the species concept does not apply
and which are too morphologically simple to be classified based on phenotypic traits.

Taxon sampling and phylogenetic signal

Owing to the development of advanced sequencing techniques in molecular biology, it has become feasible to gather
large amounts of data (DNA or amino acid sequences) to infer phylogenetic hypotheses. For example, it is not rare to
find studies with character matrices based on whole mitochondrial genomes (~16,000 nucleotides, in many animals).
However, it has been proposed that it is more important to increase the number of taxa in the matrix than to increase
the number of characters, because the more taxa the more robust is the resulting phylogenetic tree [9] . This may be
partly due to the breaking up of long branches. It has been argued that this is an important reason to incorporate data
Phylogenetics 271

from fossils into phylogenies where possible. Of course, phylogenetic data that include fossil taxa are generally
based on morphology, rather than DNA data. Using simulations, Derrick Zwickl and David Hillis[10] found that
increasing taxon sampling in phylogenetic inference has a positive effect on the accuracy of phylogenetic analyses.
Another important factor that affects the accuracy of tree reconstruction is whether the data analyzed actually contain
a useful phylogenetic signal, a term that is used generally to denote whether related organisms tend to resemble each
other with respect to their genetic material or phenotypic traits.[11] Ultimately, however, there is no way to measure
whether a particular phylogenetic hypothesis is accurate or not, unless the "true" relationships among the taxa being
examined are already known. The best result an empirical systematist can hope to attain is a tree with branches
well-supported by the available evidence.

Importance of missing data

In general, the more data that is available when constructing a tree, the more accurate and reliable the resulting tree
will be. Missing data is no less detrimental than simply having less data, although its impact is greatest when most of
the missing data is in a small number of taxa. The fewer characters that have missing data, the better; concentrating
the missing data across a small number of character states produces a more robust tree.[12]

Role of fossils
Because many morphological characters involve embryological or soft-tissue characters that cannot be fossilized,
and the interpretation of fossils is more ambiguous than living taxa, it is sometimes difficult to incorporate fossil data
into phylogenies. However, despite these limitations, the inclusion of fossils is invaluable, as they can provide
information in sparse areas of trees, breaking up long branches and constraining intermediate character states; thus,
fossil taxa contribute as much to tree resolution as modern taxa.[13]

Homoplasy weighting
Certain characters are more likely to be evolved convergently than others; logically, such characters should be given
less weight in the reconstruction of a tree.[14] Unfortunately the only objective way to determine convergence is by
the construction of a tree – a somewhat circular method. Even so, weighting homoplasious characters does indeed
lead to better-supported trees.[14] Further refinement can be brought by weighting changes in one direction higher
than changes in another; for instance, the presence of thoracic wings almost guarantees placement among the
pterygote insects, although because wings are often lost secondarily, their absence does not exclude a taxon from the
group.[15]

See also
• Bauplan
• Bioinformatics
• Biomathematics
• Cladistics
• Coalescent theory
• Computational phylogenetics
• EDGE of Existence Programme
• Important publications in phylogenetics
• Language family
• Maximum parsimony
• Molecular phylogeny
• PhyloCode
Phylogenetics 272

• Joe Felsenstein
• Systematics
• Phylogenetic tree
• Phylogenetic network
• Phylogenetic nomenclature
• Phylogenetics software
• Phylogenetic tree viewers
• Phylogeography
• Phylodynamics
• Phylogenetic comparative methods
• Microbial phylogenetics

References
[1] Edwards AWF, Cavalli-Sforza LL Phylogenetics is that branch of life science,which deals with the study of evolutionary relation among
various groups of organisms,through molecular sequencing data. (1964). Systematics Assoc. Publ. No. 6: Phenetic and Phylogenetic
Classification. ed. Reconstruction of evolutionary trees. pp. 67–76.
[2] Speer, Vrian (1998). "UCMP Glossary: Phylogenetics" (http:/ / www. ucmp. berkeley. edu/ glossary/ glossary_1. html). UC Berkeley. .
Retrieved 2008-03-22.
[3] Cavalli-Sforza, L. L.; Edwards, A. W. F. (1967). "Phylogenetic Analysis: Models and Estimation Procedures" (http:/ / jstor. org/ stable/
2406616). Evolution 21 (3): 550–570. doi:10.2307/2406616. .
[4] Pierce, Benjamin A. (2007-12-17). Genetics: A conceptual Approach (3rd ed.). W. H. Freeman. ISBN 978-0716-77928-5.
[5] Williamson DI (2003-12-31). "xviii". The Origins of Larvae (2nd ed.). Springer. pp. 261. ISBN 978-1402-01514-4.
[6] Williamson DI (2006). "Hybridization in the evolution of animal form and life-cycle". Zoological Journal of the Linnean Society 148:
585–602. doi:10.1111/j.1096-3642.2006.00236.x.
[7] John Timmer, "Examining science on the fringes: vital, but generally wrong" (http:/ / arstechnica. com/ science/ news/ 2009/ 11/
examining-science-on-the-fringes-vital-but-generally-wrong. ars), ARS Technica, 9 November 2009
[8] Michael W. Hart, and Richard K. Grosberg, "Caterpillars did not evolve from onychophorans by hybridogenesis" (http:/ / www. pnas. org/
content/ early/ 2009/ 10/ 22/ 0910229106), Proceedings of the National Academy of the Sciences, 30 October 2009 (doi:
10.1073/pnas.0910229106)
[9] Wiens J (2006). "Missing data and the design of phylogenetic analyses". Journal of Biomedical Informatics 39 (1): 34–42.
doi:10.1016/j.jbi.2005.04.001. PMID 15922672.
[10] Zwickl DJ, Hillis DM (2002). "Increased taxon sampling greatly reduces phylogenetic error". Systematic Biology 51 (4): 588–598.
doi:10.1080/10635150290102339. PMID 12228001.
[11] Blomberg SP, Garland T Jr, Ives AR (2003). "Testing for phylogenetic signal in comparative data: behavioral traits are more labile".
Evolution 57 (4): 717–745. PMID 12778543. PDF (http:/ / www. biology. ucr. edu/ people/ faculty/ Garland/ BlomEA03. pdf)
[12] Prevosti, F. J.; Chemisquy, M. �A. A. (2009). "The impact of missing data on real morphological phylogenies: influence of the number and
distribution of missing entries". Cladistics 26: 326. doi:10.1111/j.1096-0031.2009.00289.x.
[13] Cobbett, A.; Wilkinson, M.; Wills, M. (2007). "Fossils impact as hard as living taxa in parsimony analyses of morphology". Systematic
biology 56 (5): 753–766. doi:10.1080/10635150701627296. PMID 17886145.
[14] Goloboff, P. A.; Carpenter, J. M.; Arias, J. S.; Esquivel, D. R. M. (2008). "Weighting against homoplasy improves phylogenetic analysis of
morphological data sets". Cladistics 24: 758. doi:10.1111/j.1096-0031.2008.00209.x.
[15] Goloboff, P. A. (1997). "Self-Weighted Optimization: Tree Searches and Character State Reconstructions under Implied Transformation
Costs". Cladistics 13: 225. doi:10.1111/j.1096-0031.1997.tb00317.x.
Phylogenetics 273

Further reading
• Schuh, R. T. and A. V. Z. Brower. 2009. Biological Systematics: principles and applications (2nd edn.) ISBN
978-0-8014-4799-0

External links
• The Tree of Life (http://tolweb.org/tree/learn/concepts/whatisphylogeny.html)
• Interactive Tree of Life (http://itol.embl.de)
• PhyloCode (http://www.ohiou.edu/phylocode/)
• ExploreTree (http://exploretree.org/)
• UCMP Exhibit Halls: Phylogeny Wing (http://www.ucmp.berkeley.edu/exhibit/phylogeny.html)
• Willi Hennig Society (http://www.cladistics.org)
• Filogenetica.org in Spanish (http://www.filogenetica.org)
• PhyloPat, Phylogenetic Patterns (http://www.cmbi.ru.nl/phylopat)
• SplitsTree (http://www.SplitsTree.org), program for computing phylogenetic trees and unrooted phylogenetic
networks
• Dendroscope (http://www.Dendroscope.org), program for drawing phylogenetic trees and rooted phylogenetic
networks
• Phylogenetic inferring on the T-REX server (http://www.trex.uqam.ca)
• Mesquite (http://mesquiteproject.org/mesquite/mesquite.html)
• Geneious Pro (http://www.geneious.com) all-in-one phylogenetics software
• NCBI – Systematics and Molecular Phylogenetics (http://www.ncbi.nlm.nih.gov/About/primer/phylo.html)
• What Genomes Can Tell Us About the Past (http://ascb.org/ibioseminars/brenner/brenner1.cfm) – lecture on
phylogenetics by Sydney Brenner
• Mikko's Phylogeny Archive (http://www.helsinki.fi/~mhaaramo/)
• Phylogenetic Reconstruction from Gene-Order Data (http://www.cs.unm.edu/~moret/poincare.pdf)
Cladistics 274

Cladistics
Cladistics[1] is a method of classifying species of organisms into groups called clades, which consist of 1) all the
descendants of an ancestral organism and 2) the ancestor itself. For example, birds, dinosaurs, crocodiles, and all
descendants (living or extinct) of their most recent common ancestor form a clade.[2] In the terms of biological
systematics, a clade is a single "branch" on the "tree of life", a monophyletic group.
Cladistics can be distinguished from other taxonomic systems, such as phenetics, by its focus on shared derived
characters (synapomorphies). Previous systems usually employed overall morphological similarity to group species
into genera, families and other higher level classification; cladistic classifications (usually trees called cladograms)
are intended to reflect the relative recency of common ancestry or the sharing of homologous features. Cladistics is
also distinguished by its emphasis on parsimony and hypothesis testing (particularly falsificationism), rather than
subjective decisions that some other taxonomic systems rely upon.[3]
Cladistics originated in the work of the German entomologist Willi Hennig, who referred to it as "phylogenetic
systematics" (also the name of his 1966 book); the use of the terms "cladistics" and "clade" was popularized by other
researchers. The technique and sometimes the name have been successfully applied in other disciplines: for example,
to determine the relationships between the surviving manuscripts of the Canterbury Tales.[4]
Cladists use cladograms, diagrams which show ancestral relations between species, to represent the monophyletic
relationships of species, termed sister-group relationships. This is interpreted as representing phylogeny, or
evolutionary relationships. Although traditionally such cladograms were generated largely on the basis of
morphological characters, genetic sequencing data and computational phylogenetics are now very commonly used in
the generation of cladograms.

History of cladistics
The term clade was introduced in 1958 by Julian Huxley, cladistic by Cain and Harrison in 1960, and cladist (for an
adherent of Hennig's school) by Mayr in 1965.[5] Hennig referred to his own approach as phylogenetic systematics.
From the time of his original formulation until the end of the 1980s cladistics remained a minority approach to
classification. However in the 1990s it rapidly became the dominant method of classification in evolutionary
biology. Computers made it possible to process large quantities of data about organisms and their characteristics. At
about the same time the development of effective polymerase chain reaction techniques made it possible to apply
cladistic methods of analysis to biochemical and molecular genetic features of organisms as well as to anatomical
ones.[6]
Cladistics 275

Cladistics as a successor to phenetics

For some decades in the mid to late twentieth century, a commonly used methodology was phenetics ("numerical
taxonomy"). This can be seen as a predecessor[7] to some methods of today's cladistics (namely distance matrix
methods such as neighbor-joining), but made no attempt to resolve phylogeny, only similarities.

Clades
A clade is a group of taxa consisting of
an ancestor taxon and all of its
descendant taxa. In the diagram
provided, it is hypothesized that the first
vertebrate species is the common
ancestor of all vertebrate species,
including fishes (Pisces). The first
tetrapod is the ancestor of all tetrapods,
including amphibians, reptiles, mammals
and birds. The tetrapod ancestor was a
descendant of the original vertebrate
ancestor, but is not an ancestor of any
fish living today. The tetrapod clade is
thus nested within the vertebrate clade.

An important caution is that any

cladogram is a provisional hypothesis. In
a hypothetical example, further genetic The yellow group (sauropsids) is monophyletic, the blue group (reptiles) is
or morphological evidence might suggest paraphyletic, and the red group (warm-blooded animals) is polyphyletic.

that fish and amphibians share a common

ancestor that was not an ancestor of the other tetrapods. The new information would cause us to define a
fish-and-amphibian clade, altering the cladogram.

Terminology
The following terms are used to identify shared or distinct characters among groups:[8] [9] [10]
• Plesiomorphy ("close form") or ancestral state, also symplesiomorphy ("shared plesiomorphy"), is a characteristic
that is present at the base of the tree. For example, in the tree shown, the presence of a backbone (shared by all
vertebrates) can be hypothesized to have existed in the common vertebrate ancestor.
• Apomorphy ("separate form") or derived state is a characteristic believed to have evolved within the tree. For
example, all tetrapods have four limbs; thus, having four limbs is an apomorphy for vertebrates but a
plesiomorphy for tetrapods.
• Synapomorphy ("shared apomorphy") is an apomorphy which is shared between taxa.
The application of the above terms to a group depends on one's perspective in the tree. They are thus relative terms.
For example, an apomorphy of one clade is the plesiomorphy of another contained within it. These terms are
equivalent to but more precise than the homology, allowing one to express the hierarchical relationships among
different homologies.
Three main types of groups can be identified by plotting their relationships in cladograms:[8] [9] [10]
• Monophyletic groups are groups containing only taxa descended from a given ancestor taxon and all those
descendants. In the diagram, all vertebrates are monophyletic, since all the taxa are descended from a single
Cladistics 276

ancestor (the common vertebrate species) and there are no others. Monophyly is diagnosed by the synapomorphy
relation.
• Paraphyletic groups are groups excluding one or more descendant taxa of the common ancestor, and thus contain
some but not all of its descendants. For instance, excluding birds from the sample cladogram would create a
paraphyletic group, reptiles. Paraphyletic groups are typically diagnosed on the basis of shared plesiomorphy and
the exclusion of groups that are diagnosable by a synapomorphy. For example, birds are warm-blooded,
excluding them from being reptiles, which because of that exclusion is a paraphyletic group, as birds are also
descended from amniotes. The plesiomorphy is the amniotic fluid and the synapomorphy is warm-bloodedness.
• Polyphyletic groups are groups containing taxa from two or more different monophyletic groups. For instance, a
grouping of birds and mammals based on their warm-bloodedness is not monophyletic. In the diagram, the Aves
ancestor came from the Archosaurs, but the Mammalian ancestor came from the Amniotes. Although there is an
ultimate common ancestor among the Tetrapods, the latest common ancestors are not the same and therefore the
group is polyphyletic. The warm-bloodedness is not a plesiomorphy but is a homoplasy, or convergence.
Polyphyletic groups are recognized by the homoplasy relation (that is, a group is polyphyletic because it is
diagnosed by a character that actually forms a homoplasy, see wastebasket taxon).
Clades relate to each other in these ways:
• A clade is basal to another clade if it contains that other clade as a subset within it. In this case, the vertebrate
clade is basal to the tetrapod and fish clades. The use of "basal" to mean a clade that is less species-rich than a
sister clade, with such a deficit being taken as an indication of primitiveness, is incorrectly applied.[11]
• A clade located within a clade is said to be nested within that clade. The bird clade is nested within the reptilian
clade.

Three definitions of clade

There are three major ways to define a clade for use in
a cladistic taxonomy.[12]
• Node-based: the last common ancestor of A and B,
and all descendants of that ancestor. Crown groups
are a type of node-based clade.
• Branch-based: the first ancestor of A which is not
also an ancestor of C, and all descendants of that
ancestor. (This type of definition was originally
called "stem-based", but this was changed to avoid
confusion with the term "stem group".) Total groups
are a type of branch-based clade.

• Apomorphy-based: the first ancestor of A to possess

derived trait M homologously (that is,
synapomorphically) with that trait in A, and all The three ways to define a clade
descendants of that ancestor. The process of
identifying and naming groups based on apomorphies is the method that most resembles classical systematics,
with the proviso that cladistic taxa always denote a clade.
Cladistics 277

Cladograms
Cladists use cladograms, diagrams which show ancestral relations between taxa, to represent the evolutionary tree of
life. Although traditionally such cladograms were generated largely on the basis of morphological characters,
molecular sequencing data and computational phylogenetics are now very commonly used in the generation of
cladograms.
The starting point of cladistic analysis is a group of species and molecular, morphological, or other data
characterizing those species. The end result is a tree-like relationship diagram called a cladogram,[13] or sometimes a
dendrogram (Greek for "tree drawing").[14] The cladogram graphically represents a hypothetical evolutionary
process. Cladograms are subject to revision as additional data become available.
The terms "evolutionary tree", and sometimes "phylogenetic tree" are often used synonymously with cladogram,[15]
but others treat phylogenetic tree as a broader term that includes trees generated with a nonevolutionary emphasis. In
cladograms, all species lie at the leaves. The two taxa on either side of a split, with a common ancestor and no
additional descendents, are called "sister taxa" or "sister groups".[16] Each subtree, whether it contains only two or a
hundred thousand items, is called a "clade". Many cladists require that all forks in a cladogram be 2-way forks. Some
cladograms include 3-way or 4-way forks when there are insufficient data to resolve the forking to a higher level of
detail (see under phylogenetic tree).
For a given set of species, the number of distinct cladograms that can be drawn (ignoring which cladogram best
matches the species characteristics) is:[17]

Number of species 2 3 4 5 6 7 8 9 10 N

Number of cladograms 1 3 15 105 945 10,395 135,135 2,027,025 34,459,425 1*3*5*7*...*(2N-3)

This superexponential growth of the number of possible cladograms explains why manual creation of cladograms
becomes very difficult when the number of species is large. If a cladogram represents N species, the number of
levels (the "depth") in the cladogram is on the order of log2(N).[18] For example, if there are 32 species of deer, a
cladogram representing deer could be around 5 levels deep (because 25 = 32), although this is really just the lower
limit. A cladogram representing the complete tree of life, with about 10 million species, could be about 23 levels
deep. This formula gives a lower limit, with the actual depth generally a larger value, because the various branches
of the cladogram will not be uniformly deep. Conversely, the depth may be shallower if forks larger than 2-way
forks are permitted.
A cladogram tree has an implicit time axis,[19] with time running forward from the base of the tree to the leaves of
the tree. If the approximate date (for example, expressed as millions of years ago) of all the evolutionary forks were
known, those dates could be captured in the cladogram. Thus, the time axis of the cladogram could be assigned a
time scale (e.g. 1 cm = 1 million years), and the forks of the tree could be graphically located along the time axis.
Such cladograms are called scaled cladograms. Many cladograms are not of this type, for a variety of reasons:
• They are built from species characteristics that cannot be readily dated (e.g. morphological data in the absence of
fossils or other dating information)
• When the characteristic data are DNA/RNA sequences, it is feasible to use sequence differences to establish the
relative ages of the forks, but converting those ages into actual years requires a significant approximation of the
rate of change[20]
• Even when the dating information is available, positioning the cladogram's forks along the time axis in proportion
to their dates may cause the cladogram to become difficult to understand or hard to fit within a human-readable
format
Cladistics makes no distinction between extinct and extant species,[21] and it is appropriate to include extinct species
in the group of organisms being analyzed. Cladograms that are based on DNA/RNA generally do not include extinct
species because DNA/RNA samples from extinct species are rare. Cladograms based on morphology, especially
Cladistics 278

morphological characteristics that are preserved in fossils, are more likely to include extinct species.

Cladistics in taxonomy

Phylogenetic nomenclature contrasted with traditional taxonomy

Most taxonomists have used the traditional
approaches of Linnaean taxonomy and later
Evolutionary taxonomy to organize life forms. These
approaches use several fixed levels of a hierarchy,
such as kingdom, phylum, class, order, and family.
Phylogenetic nomenclature does not feature those
terms, because the evolutionary tree is so deep and so
complex that it is inadvisable to set a fixed number of
levels.

Evolutionary taxonomy insists that groups reflect

phylogenies. In contrast, Linnaean taxonomy allows
both monophyletic and paraphyletic groups as taxa.
Since the early 20th century, Linnaean taxonomists
have generally attempted to make at least family- and
lower-level taxa (i.e. those regulated by the codes of
nomenclature) monophyletic. Ernst Mayr in 1985
A highly resolved, automatically generated tree of life based on
drew a distinction between the terms cladistics and [22]
completely sequenced genomes
phylogeny:[23]

"It would seem to me to be quite evident that the two concepts of phylogeny (and their role in the
construction of classifications) are sufficiently different to require terminological distinction. The term
phylogeny should be retained for the broad concept of phylogeny, promoted by Darwin and adopted by
most students of phylogeny in the ensuing 90 years. The concept of phylogeny as mere genealogy
should be terminologically distinguished as cladistics. To lump the two concepts together
terminologically could not help but produce harmful equivocation."

Willi Hennig's pioneering work provoked a spirited debate[24] about the relative merits of phylogenetic nomenclature
versus Linnaean or evolutionary taxonomy, which has continued down to the present,[25] however Hennig did not
advocate abandoning the Linnaean nomenclatural system. Some of the debates in which the cladists were engaged
had been running since the 19th century, but they were renewed fervor,[26] as can be seen from the Foreword to
Hennig (1979) by Rosen, Nelson, and Patterson:[27]
"Encumbered with vague and slippery ideas about adaptation, fitness, biological species and natural
selection, neo-Darwinism (summed up in the "evolutionary" systematics of Mayr and Simpson) not only
lacked a definable investigatory method, but came to depend, both for evolutionary interpretation and
classification, on consensus or authority."
Phylogenetic nomenclature strictly and exclusively follows phylogeny and has arbitrarily deep trees with binary
branching: each taxon corresponds to a clade. Linnaean taxonomy, while since the advent of evolutionary theory
following phylogeny, also may subjectively consider similarity and has a fixed hierarchy of taxonomic ranks, and its
taxa are not required to correspond to clades.
Cladistics 279

Paraphyletic groups discouraged

Many cladists discourage the use of paraphyletic groups in classification of organisms, because they detract from
cladistics' emphasis on clades (monophyletic groups). In contrast, proponents of the use of paraphyletic groups argue
that any dividing line in a cladogram creates both a monophyletic section above and a paraphyletic section below.
They also contend that paraphyletic taxa are necessary for classifying earlier sections of the tree – for instance, the
early vertebrates that would someday evolve into the family Hominidae cannot be placed in any other monophyletic
family. They also argue that paraphyletic taxa provide information about significant changes in organisms'
morphology, ecology, or life history – in short, that both paraphyletic groups and clades are valuable notions with
separate purposes.

Complexity of the Tree of Life

The cladistic tree of life is a fractal:[28]
"The tree of life is inherently fractal-like in its complexity, .... Look closely at the 'lineage' of a
phylogeny ... and it dissolves into many smaller lineages, and so on, down to a very fine scale."
The overall shape of a dichotomous (bifurcating) tree is recursive; as a viewpoint zooms into the tree of life, the
same type of tree appears no matter what the scale. When extinct species are considered (both known and unknown),
the complexity and depth of the tree can be very large. Moreover the tree continues to recreate itself by bifurcation, a
series of events called fractal evolution.[29] Every single speciation event, including all the species that are now
extinct, represents an additional fork on the hypothetical, complete cladogram of the tree of life.
The tree of life is a quasi-self-similar fractal; that is, the deep reconstruction is not as regular as the shallow
reconstruction.[30] By shallow Mishler means the most recent branching toward and at the tips, and by deep the more
ancient branches further back, which are harder to reconstruct and are missing unknown extinct lines. In the shallow
part of the tree, branching events are relatively regular; it is often possible to estimate the times between them. In the
deep part of the tree, "homology assessments" are "difficult" and the times vary widely.[31] At this level Eldredge's
and Gould's punctuated equilibrium applies, which hypothesizes long periods of stability followed by punctuations
of rapid speciation, based on the fossil record.

PhyloCode approach to naming species

A formal code of phylogenetic nomenclature, the PhyloCode,[32] is currently under development. It is intended for
use by both those who would like to abandon Linnaean taxonomy and those who would like to use taxa and clades
side by side. In several instances (see for example Hesperornithes) it has been employed to clarify uncertainties in
Linnaean systematics so that in combination they yield a taxonomy that unambiguously places problematic groups in
the evolutionary tree in a way that is consistent with current knowledge.

Example
For example, Linnaean taxonomy contains the taxon Tetrapoda, defined morphologically as vertebrates with four
limbs (as well as animals with four-limbed ancestors, such as snakes), which is often given the rank of superclass,
and divides into the classes Amphibia, Reptilia, Aves, Mammalia.
Phylogenetic nomenclature also contains the taxon Tetrapoda (see the diagram under Clades above), whose living
members can be classified phylogenically as "the clade defined by the common ancestor of amphibians and
mammals", or more precisely the clade defined by the common ancestor of a specific amphibian and mammal (or
bird or snake). This definition gives us the Crown group tetrapods (or Crown-Tetrapoda). A few primitive four
legged ancestors (the Ichthyostegalia) fall outside Crown-Tetrapoda.[33] An alternative is to define tetrapoda as all
animals more closely related to mammals than to lungfish (our nearest living non-tetrapod relatives). In this
definition, the ichthyostegalians are included, together with a host of fossil animals usually classed as
Cladistics 280

crossopterygian fish. This wider definition is termed Pan-Tetrapoda. A third option is to define Tetrapoda according
to their apomorphy (their unique trait, i.e. having legs rather than fins), a definition that yield the same group as the
Linnaean taxon.
Non of the phylogenetic taxa as described above have a rank, and neither do its subtaxa. All the subclades are
contained within one another. The clades are not divided into several non-overlapping taxa (as in traditional
taxonomy), rather the clade is split into two clades at the first branching, a process repeated throughout. With regards
to the traditional classes, Aves and Mammalia are subclades, contained in the subclade Amniota, while Reptilia and
Amphibia are paraphyletic taxa, not clades.[34] Instead of classifying non-mammalian, non-avian amniotes as
reptiles, Amniota is divided into the two clades Sauropsida (which contains birds and all living amniotes other than
mammals, including all living traditional reptiles) and Theropsida (mammals and the extinct mammal-like reptiles).
Similarly, Amphibia can be split into the Batrachomorpha (fossil amphibians more closely related to modern
amphibians) and Reptiliomorpha, the latter of which the amiotes is a sub-clade.[35] Ichthyostegalians and other
Stem-tetrapods represent sister groups from splits predating the Batrachomorpha/Reptilopmorpha split.[33]

Summary of advantages of phylogenetic nomenclature

Proponents of phylogenetic nomenclature enumerate key distinctions between phylogenetic nomenclature and
Linnaean taxonomy as follows:[36]

Phylogenetic Nomenclature Linnaean Taxonomy

Handles arbitrarily deep trees. Often must invent new level names (such as superorder, suborder, infraorder, parvorder,
magnorder) to accommodate new discoveries. Biased towards trees about 4 to 12 levels deep.

Discourages naming or use of groups that are Acceptable to name and use paraphyletic groups
not monophyletic

Primary goal is to reflect actual process of Primary goal is to group species based on morphological similarities
evolution

Assumes that the shape of the tree will change New discoveries often require renaming or releveling of Classes, Orders, and Kingdoms
frequently with new discoveries

Summary of criticisms of phylogenetic nomenclature

Critics of phylogenetic nomenclature include Ashlock,[37] Mayr,[38] Williams.[39] Some of their criticisms include:

Phylogenetic Nomenclature Linnaean Taxonomy

Limited to entities related by evolution or ancestry Supports groupings without reference

to evolution or ancestry

Does not include a process for naming species Includes a process for giving unique
names to species

Clade definitions emphasize ancestry at the expense of descriptive characteristics Taxa definitions based on tangible
characteristics

Ignores sensible, clearly defined paraphyletic groups such as reptiles Permits clearly defined groups such
as reptiles

Difficult to determine if a given species is in a clade or not (e.g. if clade X is defined as "most recent Straightforward process to determine
common ancestor of A and B along with its descendants", then the only way to determine if species Y is in if a given species is in a taxon or not
the clade is to perform a complex evolutionary analysis)

Limited to organisms that evolved by inherited traits; not applicable to organisms that evolved via complex Applicable to all organisms,
gene sharing or lateral transfer regardless of evolutionary
mechanism
Cladistics 281

Application to other disciplines

The comparisons used to acquire data on which cladograms can be based are not limited to the field of biology.[40]
Any group of individuals or classes, hypothesized to have a common ancestor, and to which a set of common
characteristics may or may not apply, can be compared pairwise. Cladograms can be used to depict the hypothetical
descent relationships within groups of items in many different academic realms. The only requirement is that the
items have characteristics that can be identified and measured.
Recent attempts to use cladistic methods outside of biology address the reconstruction of lineages in:
• Anthropology and archeology.[41] Compares cultures or artifacts using groups of cultural traits or artifact features.
• Linguistics.[42] Compares languages using groups of linguistic features.
• Textual criticism or Stemmatics.[43] [44] Compares manuscripts of the same work (original lost) using groups of
distinctive copying errors.
• Ethology.[45] Compares animal species using behavioral traits presumed hereditary.

See also
• Bauplan • Important publications in phylogenetics • Phylogenomics
• Bioinformatics • Language family • Phylogeography
• Biomathematics • Maximum parsimony • Phylogenetic comparative methods
• Coalescent theory • Molecular phylogeny • Scientific Classification
• Computational phylogenetics • PhyloCode • Stratocladistics
• Dendrogram • Phylogenetics • Systematics
• Evolution of Mollusca • Phylogenetic network • Tree structure
• Last common ancestor • Phylogenetics software • Three-taxon analysis

References
[1] (Ancient Greek: κλάδος, klados, "branch")
[2] Glossary entry "clade" (http:/ / evolution. berkeley. edu/ evolibrary/ glossary/ glossary_popup. php?word=clade) Understanding Evolution.
2010. University of California Museum of Paleontology.
[3] Phillips, Ben (2000). "Natural History Collections: Cladistics" (http:/ / www. nhc. ed. ac. uk/ index. php?page=236. 273. 444). University of
Edinburgh. . Retrieved 4 July 2009.
[4] "Canterbury Tales Project" (http:/ / www. canterburytalesproject. org). . Retrieved 4 July 2009.
[5] Dupuis 1984
[6] Baron, C.; Høeg, J.T. (2005). "Gould, Scharm and the paleontologocal perspective in evolutionary biology" (http:/ / books. google. com/
?id=LalmQ4346O0C& dq=Nielsen,+ C. + 2001+ "Animal+ evolution"+ Chelicerata). In Koenemann, S.; Jenner, R.A.. Crustacea and
Arthropod Relationships. CRC Press. pp. 3–14. ISBN 0849334985. . Retrieved 2008-10-15.
[7] Mayr 1982, p. 221
[8] Patterson 1982, pp. 21–74
[9] Patterson, Colin (1988). "Homology in classical and molecular biology". Molecular Biology and Evolution 5 (6): 603–625. PMID 3065587.
[10] de Pinna, M.G.G (1991). "Concepts and tests of homology in the cladistic paradigm". Cladistics 7: 367–394.
doi:10.1111/j.1096-0031.1991.tb00045.x.
[11] Krell, F.-T.; Cranston, P. (2004). "Which side of the tree is more basal?". Systematic Entomology 29 (3): 279–281.
doi:10.1111/j.0307-6970.2004.00262.x.
[12] de Queiroz, K.; Gauthier, J. (1994). "Toward a phylogenetic system of biological nomenclature". Trends in Research in Ecology and
Evolution 9 (1): 27–31. doi:10.1016/0169-5347(94)90231-3.
[13] Cracraft, Joel; Donaghue, Michael J., eds (2004). Assembling the Tree of Life. Oxford, England: Oxford University Press. pp. 45, 78, 555.
[14] Weygoldt, P. (February 1998). "Evolution and systematics of the Chelicerata". Experimental and Applied Acarology 22 (2): 63–79.
doi:10.1023/A:1006037525704.
[15] Singh, Gurcharan (2004). Plant Systematics: An Integrated Approach. Science. pp. 203–4. ISBN 1578083516.
[16] Gould, Steven Jay (1983). Hen's Teeth and Horse's Toes. New York: Norton. p. 357. ISBN 0393017168.
[17] Lowe, Andrew (2004). Ecological Genetics: Design, Analysis, and Application. Blackwell Publishing. p. 164. ISBN 1405100338.
[18] Aldous, David (1996). "Probability Distributions on Cladograms". Random Discrete Structures. Springer. pp. 13. ISBN 0387946233.
Cladistics 282

[19] Freeman, Scott (1998). Evolutionary Analysis. Prentice Hall. p. 380. ISBN 0135680239.
[20] Carroll, Robert Lynn (1997). Patterns and Processes of Vertebrate Evolution. Cambridge University Press. p. 80. ISBN 052147809X.
[21] Scott-Ram, N. R. (1990). Transformed Cladistics, Taxonomy and Evolution. Cambridge University Press. p. 83. ISBN 0521340861.
[22] Letunic, I.; Bork, P. (2007). "Interactive Tree Of Life (iTOL): an online tool for phylogenetic tree display and annotation" (Pubmed).
Bioinformatics 23 (1): 127–8. doi:10.1093/bioinformatics/btl529. PMID 17050570.
[23] Mayr, E (1985). "Darwin and the Definition of Phylogeny" (http:/ / jstor. org/ stable/ 2413350). Systematic Zoology 34 (1): 97–98.
doi:10.2307/2413350. ..
[24] Wheeler, Quentin (2000). Species Concepts and Phylogenetic Theory: A Debate. Columbia University Press. ISBN 0231101430.
[25] Benton, M. (2000). "Stems, nodes, crown clades, and rank-free lists: is Linnaeus dead?". Biological Reviews 75 (4): 633–648.
doi:10.1111/j.1469-185X.2000.tb00055.x. PMID 11117201.
[26] Hull, David (1988). Science as a Process. University of Chicago Press. pp. 232–276. ISBN 0226360512.
[27] Hennig 1979, p. ix
[28] Mishler 2005, p. 57
[29] Gordon, Richard (1999). The Hierarchical Genome and Differentiation Waves. World Scientific. p. 664. ISBN 9810222688.
[30] Mishler 2005, p. 62
[31] Mishler 2005, p. 62: "In deep reconstruction problems, the branch events at issue happened a relatively long time ago and the ... relative
lengths of ... branches are often quite different...."
[32] Pennisi, E. (2001). "Evolutionary Biology: Preparing the Ground for a Modern 'Tree of Life'". Science 293 (5537): 1979–1980.
doi:10.1126/science.293.5537.1979. PMID 11557858.
[33] Clarck, J.A. (1997): Ichthyostega (http:/ / tolweb. org/ Ichthyostega), Tree of Life website
[34] Tudge, Colin (2002). The Variety of Life: A survey and a Celebration of all the Creatures that Have Ever Lived. Oxford: Oxford University
Press. p. 83. ISBN 0-19-860426-2.
[35] Benton, M. J. (2000), Vertebrate Paleontology, 2nd Ed. Blackwell Science Ltd 3rd ed. 2004 – see also taxonomic hierarchy of the
vertebrates (http:/ / palaeo. gly. bris. ac. uk/ benton/ vertclass. html), according to Benton 2004
[36] Hennig 1975.
[37] Ashlock 1971, Ashlock 1972, Ashlock 1974, Ashlock 1979.
[38] Mayr 1974, Mayr 1978, Mayr, E; Bock, WJ (2002). "Classifications and other ordering systems". Journal of Zoological Systematics and
Evolutionary Research 40: 169–194. doi:10.1046/j.1439-0469.2002.00211.x.
[39] Williams, P.A. (1992). "Confusion in cladism". Synthese 01: 135–132.
[40] Mace, Ruth; Clare, Clare J.; Shennan, Stephen, eds (2005). The Evolution of Cultural Diversity: A Phylogenetic Approach. Cavendish
Publishing. p. 1.
[41] Lipo, Carl; O'Brien, Michael J.; Collard, Mark et al., eds (2006). Mapping Our Ancestors: Phylogenetic Approaches in Anthropology and
Prehistory. Piscataway: Transaction Publishers.
[42] Oppenheimer, Stephen (2006). The Origins of the British. London: Robinson. pp. 290–300, 340–56. ISBN 0786718900.
[43] Ehrman, Bart D. (2005). The text of the New Testament: its tranmission, corruption and restoration (4th ed.). New York: Oxford University
Press. p. 207 ff.
[44] Robinson, Peter M.W.; O’Hara, Robert J. (1996). "Cladistic analysis of an Old Norse manuscript tradition" (http:/ / rjohara. net/ cv/
1996-rhc). Research in Humanities Computing 4: 115–137. .
[45] Jerison, Harry J. (2003). "On Theory in Comparative Psychology". In Sternberg, Robert J.; Kaufman, James C.. The evolution of
intelligence. Mahwah, NJ: Lawrence Erlbaum Associates, Inc.. p. 254. ISBN 0123852501.

Bibliography
• Ashlock, Peter D. (1971). "Monophyly and associated terms" (http://jstor.org/stable/2412223). Systematic
Zoology 20 (1): 63–69. doi:10.2307/2412223.
• Ashlock, Peter D. (1972). "Monophyly again" (http://jstor.org/stable/2412435). Systematic Zoology 21 (4):
430–438. doi:10.2307/2412435.
• Ashlock, Peter D. (1974). "The uses of cladistics". Annual Review of Ecology and Systematics 5: 81–99.
doi:10.1146/annurev.es.05.110174.000501. ISSN 0066-4162.
• Ashlock, Peter D. (1979). "An evolutionary systematist’s view of classification" (http://jstor.org/stable/
2412559). Systematic Zoology 28 (4): 441–450. doi:10.2307/2412559.
• Cuénot, Lucien (1940). "Remarques sur un essai d'arbre généalogique du règne animal". Comptes Rendus de
l'Académie des Sciences de Paris 210: 23–27. Available free online at http://gallica.bnf.fr (No direct URL).
This is the paper credited by Hennig (1979) for the first use of the term 'clade'.
• Dupuis, Claude (1984). "Willi Hennig's impact on taxonomic thought". Annual Review of Ecology and
Systematics 15: 1–24. ISSN 0066-4162.
Cladistics 283

• Hennig, Willi (1975). "'Cladistic analysis or cladistic classification': a reply to Ernst Mayr" (http://jstor.org/
stable/2412765). Systematic Zoology 24 (2): 244–256. doi:10.2307/2412765. The paper to which he was
responding is reprinted in Mayr 1976.
• Hennig, Willi (1966). Phylogenetic systematics (tr. D. Dwight Davis and Rainer Zangerl). Urbana, IL: Univ. of
Illinois Press (reprinted 1979 and 1999). ISBN 0-252-06814-9.
• Hennig, Willi (1979). Phylogenetic systematics (3rd edition of 1966 book). Urbana: University of Illinois Press.
ISBN 0-252-06814-9. Translated from manuscript and so never published in German.
• Hull, David L. (1979). "The limits of cladism" (http://jstor.org/stable/2412558). Systematic Zoology 28 (4):
416–440. doi:10.2307/2412558.
• Mayr, Ernst (1974). "Cladistic analysis or cladistic classification?". Zeitschrift fűr Zoologische Systematik und
Evolutionforschung 12: 94–128.
• Mayr, Ernst (1976). Evolution and the diversity of life (Selected essays). Cambridge, MA: Harvard University
Press. ISBN 0-674-27105-X. Reissued 1997 in paperback. Includes a reprint of Mayr's 1974 anti-cladistics paper
at pp. 433–476, "Cladistic analysis or cladistic classification." This is the paper to which Hennig 1975 is a
response.
• Mayr, Ernst (1978). "Origin and history of some terms in systematic and evolutionary biology" (http://jstor.org/
stable/2412818). Systematic Zoology 27 (1): 83–88. doi:10.2307/2412818.
• Mayr, Ernst (1982). The growth of biological thought: diversity, evolution and inheritance. Cambridge, MA:
Harvard University Press. ISBN 0-674-36446-5.
• Mishler, Brent D. (2005). "The logic of the data matrix in phylogenetic analysis". In Albert, Victor. Parsimony,
Phylogeny, and Genomics. Oxford University Press. pp. 57–70. ISBN 0199297304.
• Patterson, Colin (1982). "Morphological characters and homology". In Joysey, Kenneth A; Friday, A. E..
Problems in Phylogenetic Reconstruction. Systematics Association Special Volume 21. London: Academic Press.
ISBN 0-12-391250-4.
• Schuh, Randall T. and Andrew V. Z. Brower. 2009. Biological Systematics: principles and applications (2nd
edn.) Cornell University Press, ISBN 978-0-8014-4799-0

External links
• Collins, Allen G.; Guralnick, Rob; Smith, Dave (1994-2005). "Journey into Phylogenetic Systematics" (http://
www.ucmp.berkeley.edu/clad/clad4.html). University of California Museum of Paleontology. Retrieved 21
January 2010.
• Felsenstein, Joe. "Phylogeny Programs" (http://evolution.gs.washington.edu/phylip/software.html). Seattle:
University of Washington. Retrieved 21 January 2010.
• O'Neil, Dennis (1998-2008). "Classification of Living Things" (http://anthro.palomar.edu/animal/default.
htm). San Marcos CA: Palomar College. Retrieved 21 January 2010.
• Robinson, Peter; O'Hara, Robert J. (1992). "Report on the Textual Criticism Challenge 1991" (http://rjohara.net/
darwin/files/bmcr). rjohara.net. Retrieved 21 January 2010.
• Theobald, Douglas (1999-2004). "Phylogenetics Primer" (http://www.talkorigins.org/faqs/comdesc/phylo.
html). The TalkOrigins Archive. Retrieved 21 January 2010.
• Wiley, E.O.; Siegel-Causey, D.; Brooks, D.R.; Funk, V.A. (1991). "Chapter 1: Introduction, Terms and Concepts"
(http://www.amnh.org/learn/pd/fish_2/pdf/compleat_cladist.pdf). The Compleat Cladist: A Primer of
Phylogenetic Procedures. The University of Kansas Museum of Natural History Special Publication No. 19.
American Museum of Natural History. ISBN 0893380350.
Cladogram 284

Cladogram
A cladogram is a diagram used in cladistics which
shows ancestral relations between organisms, to
represent the evolutionary tree of life. Although
traditionally such cladograms were generated largely
on the basis of morphological characters, DNA and
RNA sequencing data and computational phylogenetics
are now very commonly used in the generation of A horizontal cladogram, with the ancestor (not named) to the left
cladograms.

Generating a cladogram
A greatly simplified procedure for generating a
cladogram is:[1]
1. Gather and organize data
2. Consider possible cladograms
3. Select best cladogram

Step 1
A cladistic analysis begins with the following data:
A vertical cladogram, with the ancestor at the top
• a list of species to be organized
• a list of characteristics to be compared
• for each species, the value of each of the listed
characteristics or character states
For example, if analyzing 20 species of birds, the data
might be:
• the list of 20 species
• characteristics such as genome sequence, skeletal
anatomy, biochemical processes, and feather
coloration
• for each of the 20 species, its particular genome
sequence, skeletal anatomy, biochemical processes,
and feather coloration Two vertical cladograms, the ancestor at the bottom

Molecular versus morphological data

The characteristics used to create a cladogram can be roughly categorized as either morphological (synapsid skull,
warm blooded, notochord, unicellular, etc.) or molecular (DNA, RNA, or other genetic information).[1] Prior to the
advent of DNA sequencing, all cladistic analysis used morphological data.
As DNA sequencing has become cheaper and easier, molecular systematics has become a more and more popular
way to reconstruct phylogenies.[2] Using a parsimony criterion is only one of several methods to infer a phylogeny
from molecular data; maximum likelihood and Bayesian inference, which incorporate explicit models of sequence
evolution, are non-Hennigian ways to evaluate sequence data. Another powerful method of reconstructing
phylogenies is the use of genomic retrotransposon markers, which are thought to be less prone to the problem of
reversion that plagues sequence data. They are also generally assumed to have a low incidence of homoplasies
Cladogram 285

because it was once thought that their integration into the genome was entirely random; this seems at least
sometimes not to be the case, however.
Ideally, morphological, molecular, and possibly other phylogenies should be combined into an analysis of total
evidence: All have different intrinsic sources of error. For example, character convergence (homoplasy) is much
more common in morphological data than in molecular sequence data, but character reversions that are
unrecognizable as such are more common in the latter (see long branch attraction). Morphological homoplasies can
usually be recognized as such if character states are defined with enough attention to detail.

Plesiomorphies and synapomorphies

The researcher must decide which character states were

present before the last common ancestor of the species
group (plesiomorphies) and which were present in the
last common ancestor (synapomorphies) and does so by
comparison to one or more outgroups. The choice of an
outgroup is a crucial step in cladistic analysis because
different outgroups can produce trees with profoundly
different topologies. Note that only synapomorphies are Apomorphy in cladistics
of use in characterizing clades.

Avoid homoplasies
A homoplasy is a character that is shared by multiple species due to some cause other than common ancestry.[3]
Typically, homoplasies occur due to convergent evolution. Use of homoplasies when building a cladogram is
sometimes unavoidable but is to be avoided when possible.
A well known example of homoplasy due to convergent evolution would be the character, "presence of wings".
Though the wings of birds, bats, and insects serve the same function, each evolved independently, as can be seen by
their anatomy. If a bird, bat, and a winged insect were scored for the character, "presence of wings", a homoplasy
would be introduced into the dataset, and this would confound the analysis, possibly resulting in a false evolutionary
scenario.
Homoplasies can often be avoided outright in morphological datasets by defining characters more precisely and
increasing their number. When analyzing "supertrees" (datasets incorporating as many taxa of a suspected clade as
possible), it may become unavoidable to introduce character definitions that are imprecise, as otherwise the
characters might not apply at all to a large number of taxa; to continue with the "wings" example, the presence of
wings would hardly be a useful character if attempting a phylogeny of all Metazoa, as most of these don't have wings
at all. Cautious choice and definition of characters thus is another important element in cladistic analyses. With a
faulty outgroup or character set, no method of evaluation is likely to produce a phylogeny representing the
evolutionary reality.
Cladogram 286

Step 2
When there are just a few species being organized, it is possible to do this
step manually, but most cases require a computer program. There are scores
of computer programs available to support cladistics.[4] See phylogenetic
tree for more information about tree-generating computer programs.
Because the total number of possible cladograms grows exponentially with
the number of species, it is impractical for a computer program to evaluate
every individual cladogram. A typical cladistic program begins by using
heuristic techniques to identify a small number of candidate cladograms.
Many cladistic programs then continue the search with the following
repetitive steps:

1. Evaluate the candidate cladograms by comparing them to the

characteristic data
2. Identify the best candidates that are most consistent with the
characteristic data
3. Create additional candidates by creating several variants of each of the
best candidates from the prior step
4. Use heuristics to create several new candidate cladograms unrelated to
the prior candidates
5. Repeat these steps until the cladograms stop getting better
Computer programs that generate cladograms use algorithms that are very
computationally intensive,[5] because the cladogram problem is NP-hard.

Simple cladistics
Step 3
There are several algorithms available to identify the "best" cladogram.[6] Most algorithms use a metric to measure
how consistent a candidate cladogram is with the data. Most cladogram algorithms use the mathematical techniques
of optimization and minimization.
In general, cladogram generation algorithms must be implemented as computer programs, although some algorithms
can be performed manually when the data sets are trivial (for example, just a few species and a couple of
characteristics).
Some algorithms are useful only when the characteristic data are molecular (DNA, RNA); other algorithms are
useful only when the characteristic data are morphological. Other algorithms can be used when the characteristic
data includes both molecular and morphological data.
Algorithms for cladograms include least squares, neighbor-joining, parsimony, maximum likelihood, and Bayesian
inference.
Biologists sometimes use the term parsimony for a specific kind of cladogram generation algorithm and sometimes
as an umbrella term for all cladogram algorithms.[7]
Algorithms that perform optimization tasks (such as building cladograms) can be sensitive to the order in which the
input data (the list of species and their characteristics) is presented. Inputting the data in various orders can cause the
same algorithm to produce different "best" cladograms. In these situations, the user should input the data in various
orders and compare the results.
Using different algorithms on a single data set can sometimes yield different "best" cladograms, because each
algorithm may have a unique definition of what is "best".
Cladogram 287

Because of the astronomical number of possible cladograms, algorithms cannot guarantee that the solution is the
overall best solution. A nonoptimal cladogram will be selected if the program settles on a local minimum rather than
the desired global minimum.[8] To help solve this problem, many cladogram algorithms use a simulated annealing
approach to increase the likelihood that the selected cladogram is the optimal one.[9]

References
[1] DeSalle, Rob (2002). Techniques in Molecular Systematics and Evolution. Birkhauser. ISBN 376436257X.
[2] Hillis, David (1996). Molecular Systematics. Sinaur. ISBN 0878932828.
[3] West-Eberhard, Mary Jane (2003). Developmental Plasticity and Evolution. Oxford Univ. Press. pp. 353–376. ISBN 0195122356.
[4] "List of Cladistics Software Programs" (http:/ / evolution. genetics. washington. edu/ phylip/ software. pars. html). .
[5] Hodkinson, Trevor (2006). Reconstructing the Tree of Life: Taxonomy and Systematics of Species Rich Taxa. CRC Press. p. 61–128.
ISBN 0849395798.
[6] Kitching, Ian (1998). Cladistics: The Theory and Practice of Parsimony Analysis. Oxford University Press. ISBN 0198501382.
[7] Stewart, Caro-Beth (1993). "The Powers and Pitfalls of Parsimony". Nature 361 (6413): 603–607. doi:10.1038/361603a0. PMID 8437621.
[8] Foley, Peter (1993). Cladistics: A Practical Course in Systematics. Oxford Univ. Press. p. 66. ISBN 0198577664.
[9] Nixon K. C. (1999). "The Parsimony Ratchet: a new method for rapid parsimony analysis". Cladistics 15: 407–414.
doi:10.1111/j.1096-0031.1999.tb00277.x.

Molecular phylogenetics
Molecular phylogenetics, also known as molecular systematics, is the use of the structure of molecules to gain
information on an organism's evolutionary relationships. The result of a molecular phylogenetic analysis is expressed
in a phylogenetic tree.

History of molecular phylogenetics

The theoretical frameworks for molecular systematics were laid in the 1960s in the works of Emile Zuckerkandl,
Emanuel Margoliash, Linus Pauling and Walter M. Fitch.[1] Applications of molecular systematics were pioneered
by Charles G. Sibley (birds), Herbert C. Dessauer (herpetology), and Morris Goodman (primates), followed by Allan
C. Wilson, Robert K. Selander, and John C. Avise (who studied various groups). Work with protein electrophoresis
began around 1956. Although the results were not quantitative and did not initially improve on morphological
classification, they provided tantalizing hints that long-held notions of the classifications of birds, for example,
needed substantial revision. In the period of 1974–1986, DNA-DNA hybridization was the dominant technique.[2]

Techniques and applications

Every living organism contains DNA, RNA, and proteins. Closely related organisms generally have a high degree of
agreement in the molecular structure of these substances, while the molecules of organisms distantly related usually
show a pattern of dissimilarity. Conserved sequences, such as mitochondrial DNA, are expected to accumulate
mutations over time, and assuming a constant rate of mutation provide a molecular clock for dating divergence.
Molecular phylogeny uses such data to build a "relationship tree" that shows the probable evolution of various
organisms. Not until recent decades, however, has it been possible to isolate and identify these molecular structures.
The most common approach is the comparison of homologous sequences for genes using sequence alignment
techniques to identify similarity. Another application of molecular phylogeny is in DNA barcoding, where the
species of an individual organism is identified using small sections of mitochondrial DNA. Another application of
the techniques that make this possible can be seen in the very limited field of human genetics, such as the ever more
popular use of genetic testing to determine a child's paternity, as well as the emergence of a new branch of criminal
forensics focused on evidence known as genetic fingerprinting.
Molecular phylogenetics 288

Theoretical background
Early attempts at molecular systematics were also termed as chemotaxonomy and made use of proteins, enzymes,
carbohydrates and other molecules which were separated and characterized using techniques such as
chromatography. These have been largely replaced in recent times by DNA sequencing which produces the exact
sequences of nucleotides or bases in either DNA or RNA segments extracted using different techniques. These are
generally considered superior for evolutionary studies since the actions of evolution are ultimately reflected in the
genetic sequences. At present it is still a long and expensive process to sequence the entire DNA of an organism (its
genome), and this has been done for only a few species. However it is quite feasible to determine the sequence of a
defined area of a particular chromosome. Typical molecular systematic analyses require the sequencing of around
1000 base pairs. At any location within such a sequence, the bases found in a given position may vary between
organisms. The particular sequence found in a given organism is referred to as its haplotype. In principle, since there
are four base types, with 1000 base pairs, we could have 41000 distinct haplotypes. However, for organisms within a
particular species or in a group of related species, it has been found empirically that only a minority of sites show
any variation at all and most of the variations that are found are correlated, so that the number of distinct haplotypes
that are found is relatively small.
In a molecular systematic analysis, the haplotypes are determined for a defined area of genetic material; ideally a
substantial sample of individuals of the target species or other taxon are used however many current studies are
based on single individuals. Haplotypes of individuals of closely related, but supposedly different, taxa are also
determined. Finally, haplotypes from a smaller number of individuals from a definitely different taxon are
determined: these are referred to as an out group. The base sequences for the haplotypes are then compared. In the
simplest case, the difference between two haplotypes is assessed by counting the number of locations where they
have different bases: this is referred to as the number of substitutions (other kinds of differences between haplotypes
can also occur, for example the insertion of a section of nucleic acid in one haplotype that is not present in another).
Usually the difference between organisms is re-expressed as a percentage divergence, by dividing the number of
substitutions by the number of base pairs analysed: the hope is that this measure will be independent of the location
and length of the section of DNA that is sequenced.
An older and superseded approach was to determine the divergences between the genotypes of individuals by
DNA-DNA hybridisation. The advantage claimed for using hybridisation rather than gene sequencing was that it was
based on the entire genotype, rather than on particular sections of DNA. Modern sequence comparison techniques
overcome this objection by the use of multiple sequences.
Once the divergences between all pairs of samples have been determined, the resulting triangular matrix of
differences is submitted to some form of statistical cluster analysis, and the resulting dendrogram is examined in
order to see whether the samples cluster in the way that would be expected from current ideas about the taxonomy of
the group, or not. Any group of haplotypes that are all more similar to one another than any of them is to any other
haplotype may be said to constitute a clade. Statistical techniques such as bootstrapping and jackknifing help in
providing reliability estimates for the positions of haplotypes within the evolutionary trees.

Limitations of molecular systematics

Molecular systematics is an essentially cladistic approach: it assumes that classification must correspond to
phylogenetic descent, and that all valid taxa must be monophyletic.
Molecular systematics often uses the molecular clock assumption that quantitative similarity of genotype is a
sufficient measure of the recency of genetic divergence. Particularly in relation to speciation, this assumption could
be wrong if either some genotypic modification acted to prevent interbreeding between two groups of organisms, or
genetic modification proceeded at different rates in different subgroups of the organisms.
Molecular phylogenetics 289

In animals, it is often convenient to use mitochondrial DNA for molecular systematic analysis. However, because in
mammals mitochondria are inherited only from the mother, this is not fully satisfactory, because inheritance in the
paternal line might not be detected.

Further reading
• Felsenstein, J. 2004. Inferring phylogenies. Sinauer Associates Incorporated. ISBN 0-87893-177-5.
• Hillis, D. M. & Moritz, C. 1996. Molecular systematics. 2nd ed. Sinauer Associates Incorporated. ISBN
0-87893-282-8.
• Page, R. D. M. & Holmes, E. C. 1998. Molecular evolution: a phylogenetic approach. Blackwell Science,
Oxford. ISBN 0-86542-889-1.
• Soltis, P.S., Soltis, D.E., and Doyle, J.J. (1992) Molecular systematics of plants. Chapman & Hall, New York.
ISBN-0-41202-231-1.
• Soltis, P.S., Soltis, D.E., and Doyle, J.J. (1998) Molecular Systematics of Plants II: DNA Sequencing. Kluwer
Academic Publishers Boston, Dordrecht, London. ISBN-0-41211-131-4.

See also
• molecular evolution
• computational phylogenetics
• PhyloCode
• Microbial phylogenetics

References
[1] Edna Suárez-Díaz & Victor H. Anaya-Muñoz (2008) History, objectivity, and the construction of molecular phylogenies. Stud. Hist. Phil.
Biol. & Biomed. Sci. 39:451–468
[2] Ahlquist, Jon E., 1999: Charles G. Sibley: A commentary on 30 years of collaboration. The Auk, vol. 116, no. 3 (July 1999). A PDF or DjVu
version of this article can be downloaded from the issue's table of contents page (http:/ / elibrary. unm. edu/ sora/ Auk/ v116n03/ index. php).

External links
• NCBI - Systematics and Molecular Phylogenetics (http://www.ncbi.nlm.nih.gov/About/primer/phylo.html)
 290

Fields

Evolutionary developmental biology

Evolutionary developmental biology (evolution of development or informally, evo-devo) is a field of biology that
compares the developmental processes of different organisms to determine the ancestral relationship between them,
and to discover how developmental processes evolved. It addresses the origin and evolution of embryonic
development; how modifications of development and developmental processes lead to the production of novel
features, such as the evolution of feathers;[1] the role of developmental plasticity in evolution; how ecology impacts
in development and evolutionary change; and the developmental basis of homoplasy and homology.[2]
Although interest in the relationship between ontogeny and phylogeny extends back to the nineteenth century, the
contemporary field of evo-devo has gained impetus from the discovery of genes regulating embryonic development
in model organisms. General hypotheses remain hard to test because organisms differ so much in shape and form.[3]
Nevertheless, it now appears that just as evolution tends to create new genes from parts of old genes (molecular
economy), evo-devo demonstrates that evolution alters developmental processes (genes and gene networks) to create
new and novel structures from the old gene networks (such as bone structures of the jaw deviating to the ossicles of
the middle ear) or will conserve (molecular economy) a similar program in a host of organisms such as eye
development genes in molluscs, insects, and vertebrates.[4] [5] Initially the major interest has been in the evidence of
homology in the cellular and molecular mechanisms that regulate body plan and organ development. However more
modern approaches include developmental changes associated with speciation.[6]

Basic principles
Charles Darwin's theory of evolution is based on three principles: natural selection, heredity, and variation. At the
time that Darwin wrote, the principles underlying heredity and variation were poorly understood. In the 1940s,
however, biologists incorporated Gregor Mendel's principles of genetics to explain both, resulting in the modern
synthesis. It was not until the 1980s and 1990s, however, when more comparative molecular sequence data between
different kinds of organisms was amassed and detailed, that an understanding of the molecular basis of the
developmental mechanisms has arisen. Currently, it is well understood how genetic mutation occurs. However,
developmental mechanisms are not understood sufficiently to explain which kinds of phenotypic variation can arise
in each generation from variation at the genetic level. Evolutionary developmental biology studies how the dynamics
of development determine the phenotypic variation arising from genetic variation and how that affects phenotypic
evolution (specially its direction). At the same time evolutionary developmental biology also studies how
development itself evolves. Thus, the origins of evolutionary developmental biology come from both an
improvement in molecular biology techniques as applied to development, and the full appreciation of the limitations
of classic neo-Darwinism as applied to phenotypic evolution. Some evo-devo researchers see themselves as
extending and enhancing the modern synthesis by incorporating into it findings of molecular genetics and
developmental biology. Others, drawing on findings of discordances between genotype and phenotype and
epigenetic mechanisms of development, are mounting an explicit challenge to neo-Darwinism.
Evolutionary developmental biology is not yet a unified discipline, but can be distinguished from earlier approaches
to evolutionary theory by its focus on a few crucial ideas. One of these is modularity: as has been long recognized,
plants and animal bodies are modular: they are organized into developmentally and anatomically distinct parts. Often
these parts are repeated, such as fingers, ribs, and body segments. Evo-devo seeks the genetic and evolutionary basis
for the division of the embryo into distinct modules, and for the partly independent development of such modules.
Evolutionary developmental biology 291

Another central idea is that some gene products function as switches whereas others act as diffusible signals. Genes
specify proteins, some of which act as structural components of cells and others as enzymes that regulate various
biochemical pathways within an organism. Most biologists working within the modern synthesis assumed that an
organism is a straightforward reflection of its component genes. The modification of existing, or evolution of new,
biochemical pathways (and, ultimately, the evolution of new species of organisms) depended on specific genetic
mutations. In 1961, however, Jacques Monod, Jean-Pierre Changeux and François Jacob discovered within the
bacterium Escherichia coli a gene that functioned only when "switched on" by an environmental stimulus.[7] Later,
scientists discovered specific genes in animals, including a subgroup of the genes which contain the homeobox DNA
motif, called Hox genes, that act as switches for other genes, and could be induced by other gene products,
morphogens, that act analogously to the external stimuli in bacteria. These discoveries drew biologists' attention to
the fact that genes can be selectively turned on and off, rather than being always active, and that highly disparate
organisms (for example, fruit flies and human beings) may use the same genes for embryogenesis (e.g., the genes of
the "developmental-genetic toolkit", see below), just regulating them differently.
Similarly, organismal form can be influenced by mutations in promoter regions of genes, those DNA sequences at
which the products of some genes bind to and control the activity of the same or other genes, not only
protein-specifying sequences. In addition to providing new support for Darwin's assertion that all organisms are
descended from a common ancestor, this finding suggested that the crucial distinction between different species
(even different orders or phyla) may be due less to differences in their content of gene products than to differences in
spatial and temporal expression of conserved genes. The implication that large evolutionary changes in body
morphology are associated with changes in gene regulation, rather than the evolution of new genes, suggested that
the action of natural selection on promoters responsive to Hox and other "switch" genes may play a major role in
evolution.
Another focus of evo-devo is developmental plasticity, the basis of the recognition that organismal phenotypes are
not uniquely determined by their genotypes. If generation of phenotypes is conditional, and dependent on external or
environmental inputs, evolution can proceed by a "phenotype-first" route,[3] [8] with genetic change following, rather
than initiating, the formation of morphological and other phenotypic novelties. The case for this was argued for by
Mary Jane West-Eberhard in her 2003 book Developmental plasticity and evolution.[8]

History
An early version of recapitulation theory, also called the biogenetic law or embryological parallelism, was put
forward by Étienne Serres in 1824–26 as what became known as the "Meckel-Serres Law" which attempted to
provide a link between comparative embryology and a "pattern of unification" in the organic world. It was supported
by Étienne Geoffroy Saint-Hilaire as part of his ideas of idealism, and became a prominent part of his version of
Lamarckism leading to disagreements with Georges Cuvier. It was widely supported in the Edinburgh and London
schools of higher anatomy around 1830, notably by Robert Edmond Grant, but was opposed by Karl Ernst von
Baer's embryology of divergence in which embryonic parallels only applied to early stages where the embryo took a
general form, after which more specialised forms diverged from this shared unity in a branching pattern. The
anatomist Richard Owen used this to support his idealist concept of species as showing the unrolling of a divine plan
from an archetype, and in the 1830s attacked the transmutation of species proposed by Lamarck, Geoffroy and
Grant.[9] In the 1850s Owen began to support an evolutionary view that the history of life was the gradual unfolding
of a teleological divine plan,[10] in a continuous "ordained becoming", with new species appearing by natural
birth.[11]
In On the Origin of Species (1859), Charles Darwin proposed evolution through natural selection, a theory central to
modern biology. Darwin recognised the importance of embryonic development in the understanding of evolution,
and the way in which von Baer's branching pattern matched his own idea of descent with modification[12] :
Evolutionary developmental biology 292

“ We can see why characters derived from the embryo should be of equal importance with those derived from the adult, for a natural
classification of course includes all ages.
[13]
”
Ernst Haeckel (1866), in his endeavour to produce a synthesis of Darwin's theory with Lamarckism and
Naturphilosophie, proposed that "ontogeny recapitulates phylogeny," that is, the development of the embryo of every
species (ontogeny) fully repeats the evolutionary development of that species (phylogeny), in Geoffroy's linear
model rather than Darwin's idea of branching evolution.[12] Haeckel's concept explained, for example, why humans,
and indeed all vertebrates, have gill slits and tails early in embryonic development. His theory has since been
discredited. However, it served as a backdrop for a renewed interest in the evolution of development after the
modern evolutionary synthesis was established (roughly 1936 to 1947).
Stephen Jay Gould called this approach to explaining evolution as terminal addition; as if every evolutionary
advance was added as new stage by reducing the duration of the older stages. The idea was based on observations of
neoteny.[14] This was extended by the more general idea of heterochrony (changes in timing of development) as a
mechanism for evolutionary change.[15]
D'Arcy Thompson postulated that differential growth rates could produce variations in form in his 1917 book On
Growth and Form. He showed the underlying similarities in body plans and how geometric transformations could be
used to explain the variations.
Edward B. Lewis discovered homeotic genes, rooting the emerging discipline of evo-devo in molecular genetics. In
2000, a special section of the Proceedings of the National Academy of Sciences (PNAS) was devoted to
"evo-devo",[16] and an entire 2005 issue of the Journal of Experimental Zoology Part B: Molecular and
Developmental Evolution was devoted to the key evo-devo topics of evolutionary innovation and morphological
novelty.[17]

The developmental-genetic toolkit

The developmental-genetic toolkit consists of a small fraction of the genes in an organism's genome whose
products control its development. These genes are highly conserved among Phyla. Differences in deployment of
toolkit genes affect the body plan and the number, identity, and pattern of body parts. The majority of toolkit genes
are components of signaling pathways, and encode for the production of transcription factors, cell adhesion proteins,
cell surface receptor proteins, and secreted morphogens, all of these participate in defining the fate of
undifferentiated cells, generating spatial and temporal patterns, which in turn form the body plan of the organism.
Among the most important of the toolkit genes are those of the Hox gene cluster, or complex. Hox genes,
transcription factors containing the more broadly distributed homeobox protein-binding DNA motif, function in
patterning the body axis. Thus, by combinatorial specifying the identity of particular body regions, Hox genes
determine where limbs and other body segments will grow in a developing embryo or larva. A paragon of a toolbox
gene is Pax6/eyeless, which controls eye formation in all animals. It has been found to produce eyes in mice and
Drosophila, even if mouse Pax6/eyeless was expressed in Drosophila.[18]
This means that a big part of the morphological evolution undergone by organisms is a product of variation in the
genetic toolkit, either by the genes changing their expression pattern or acquiring new functions. A good example of
the first is the enlargement of the beak in Darwin's Large Ground-finch (Geospiza magnirostris), in which the gene
BMP is responsible for the larger beak of this bird, relative to the other finches.[19]
The loss of legs in snakes and other squamates is another good example of genes changing their expression pattern.
In this case the gene Distal-less is very under-expressed, or not expressed at all, in the regions where limbs would
form in other tetrapods.[20] This same gene determines the spot pattern in butterfly wings,[21] which shows that the
toolbox genes can change their function.
Evolutionary developmental biology 293

Toolbox genes, as well as being highly conserved, also tend to evolve the same function convergently or in parallel.
Classic examples of this are the already mentioned Distal-less gene, which is responsible for appendage formation in
both tetrapods and insects, or, at a finer scale, the generation of wing patterns in the butterflies Heliconius erato and
Heliconius melpomene. These butterflies are Müllerian mimics whose coloration pattern arose in different
evolutionary events, but is controlled by the same genes.[22] The previous supports Kirschner and Gerhardt's theory
of Facilitated Variation, which states that morphological evolutionary novelty is generated by regulatory changes in
various members of a large set of conserved mechanisms of development and physiology.[23]

Development and the origin of novelty

Among the more surprising and, perhaps, counterintuitive (from a neo-Darwinian viewpoint) results of recent
research in evolutionary developmental biology is that the diversity of body plans and morphology in organisms
across many phyla are not necessarily reflected in diversity at the level of the sequences of genes, including those of
the developmental genetic toolkit and other genes involved in development. Indeed, as Gerhart and Kirschner have
noted, there is an apparent paradox: "where we most expect to find variation, we find conservation, a lack of
change".[24]
Even within a species, the occurrence of novel forms within a population does not generally correlate with levels of
genetic variation sufficient to account for all morphological diversity. For example, there is significant variation in
limb morphologies amongst salamanders and in differences in segment number in centipedes, even when the
respective genetic variation is low.
A major question then, for evo-devo studies, is: If the morphological novelty we observe at the level of different
clades is not always reflected in the genome, where does it come from? Apart from neo-Darwinian mechanisms such
as mutation, translocation and duplication of genes, novelty may also arise by mutation-driven changes in gene
regulation. The finding that much biodiversity is not due to differences in genes, but rather to alterations in gene
regulation, has introduced an important new element into evolutionary theory.[25] Diverse organisms may have
highly conserved developmental genes, but highly divergent regulatory mechanisms for these genes. Changes in
gene regulation are "second-order" effects of genes, resulting from the interaction and timing of activity of gene
networks, as distinct from the functioning of the individual genes in the network.
The discovery of the homeotic Hox gene family in vertebrates in the 1980s allowed researchers in developmental
biology to empirically assess the relative roles of gene duplication and gene regulation with respect to their
importance in the evolution of morphological diversity. Several biologists, including Sean B. Carroll of the
University of Wisconsin–Madison suggest that "changes in the cis-regulatory systems of genes" are more significant
than "changes in gene number or protein function".[26] These researchers argue that the combinatorial nature of
transcriptional regulation allows a rich substrate for morphological diversity, since variations in the level, pattern, or
timing of gene expression may provide more variation for natural selection to act upon than changes in the gene
product alone.
Epigenetic alterations of gene regulation or phenotype generation that are subsequently consolidated by changes at
the gene level constitute another class of mechanisms for evolutionary innovation. Epigenetic changes include
modification of the genetic material due to methylation and other reversible chemical alteration [27] , as well as
nonprogrammed remolding of the organism by physical and other environmental effects due to the inherent plasticity
of developmental mechanisms.[8] The biologists Stuart A. Newman and Gerd B. Müller have suggested that
organisms early in the history of multicellular life were more susceptible to this second category of epigenetic
determination than are modern organisms, providing a basis for early macroevolutionary changes.[28]
Evolutionary developmental biology 294

See also
• Developmental biology
• Animal evolution
• Plant Evolutionary Developmental Biology
• Baldwin effect
• Developmental systems theory
• Evolution of multicellularity
• Genetic assimilation
• Ontogeny
• Ontogeny recapitulates phylogeny
• List of gene families
• Important publications in evolutionary developmental biology
• Evolution and Development Leading journal
• Body plan
• Cell signaling
• Signal transduction
• Cell signaling networks
• Transcription factor
• Enhancer
• Enhanceosome
• promoter (biology)
• Gene regulatory network

References
[1] Prum, R.O., Brush, A.H. (March 2003). "Which Came First, the Feather or the Bird?". Scientific American 288 (3): 84–93.
doi:10.1038/scientificamerican0303-84. PMID 12616863.
[2] Hall, Brian K. (2000). "Evo-devo or devo-evo—does it matter". Evolution & Development 2: 177–178.
doi:10.1046/j.1525-142x.2000.00003e.x.
[3] Palmer, RA (2004). "Symmetry breaking and the evolution of development". Science 306 (5697): 828–833. doi:10.1126/science.1103707.
PMID 15514148.
[4] Tomarev, Stanislav I.; Callaerts, Patrick; Kos, Lidia; Zinovieva, Rina; Halder, Georg; Gehring, Walter; Piatigorsky, Joram (1997). "Squid
Pax-6 and eye development" (http:/ / www. pnas. org/ content/ 94/ 6/ 2421. full). Proceedings of the National Academy of Sciences 94 (6):
2421–2426. doi:10.1073/pnas.94.6.2421. .
[5] Pichaud, Franck; Desplan, Claude (August 2002). "Pax genes and eye organogenesis". Current opinion in genetics and development 12 (4):
430–434. doi:10.1016/S0959-437X(02)00321-0. PMID 12100888.
[6] Pennisi, E (2002). "EVOLUTIONARY BIOLOGY:Evo-Devo Enthusiasts Get Down to Details". Science 298 (5595): 953–955..
doi:10.1126/science.298.5595.953. PMID 12411686.
[7] Monod, J; Changeux, JP; Jacob, F (1963). "Allosteric proteins and cellular control systems". Journal of Molecular Biology 6: 306–329.
doi:10.1016/S0022-2836(63)80091-1. PMID 13936070.
[8] West-Eberhard, M-J. (2003). Developmental plasticity and evolution. New York: Oxford University Press. ISBN 978-0-19-512235-0.
[9] Desmond 1989, pp. 53–53, 86–88, 337–340
Secord 2003, pp. 252–253
[10] Bowler 2003, pp. 120–128, 208
Secord 2003, pp. 424, 512
[11] Desmond & Moore 1991, pp. 490–491
[12] Bowler 2003, p. 170, 190-191
[13] Darwin, Charles (1859). On the Origin of Species. London: John Murray. pp.  439–430 (http:/ / darwin-online. org. uk/ content/
frameset?viewtype=text& itemID=F373& pageseq=457). ISBN 0801413192.
[14] Ridley, Mark (2003). Evolution (http:/ / www. blackwellpublishing. com/ ridley/ ). Wiley-Blackwell. ISBN 978-1-4051-0345-9. .
[15] Gould, Stephen Jay (1977). Ontogeny and Phylogeny. Cambridge, Massachusetts: Harvard University Press. ISBN 0-674-63940-5.
[16] Goodman CS and Coughlin BS (Eds). (2000). "Special feature: The evolution of evo-devo biology" (http:/ / www. pnas. org/ cgi/ content/
full/ 97/ 9/ 4424). Proceedings of the National Academy of Sciences 97 (9): 4424–4456. doi:10.1073/pnas.97.9.4424. PMID 10781035.
Evolutionary developmental biology 295

PMC 18255. .
[17] Müller GB and Newman SA (Eds.) (2005). "Special issue: Evolutionary Innovation and Morphological Novelty" (http:/ / www3.
interscience. wiley. com/ cgi-bin/ jissue/ 112149101). Journal of Exp. Zool. Part B: Molecular and Developmental Evolution 304B: 485–631.
.
[18] Xu, P.X., Woo, I., Her, H., Beier, D.R., Maas, R.L. (1997). "Mouse Eya homologues of the Drosophila eyes absent gene require Pax6 for
expression in lens and nasal placode". Development 124 (1): 219–231. PMID 9006082.
[19] Abzhanov, A.; Protas, M.; Grant, B.R.; Grant, P.R.; Tabin, C.J. (2004). "Bmp4 and Morphological Variation of Beaks in Darwin's Finches".
Science 305 (5689): 1462–1465. doi:10.1126/science.1098095. PMID 15353802.
[20] Cohn, M.J.; Tickle, C. (1999). "Developmental basis of limblessness and axial patterning in snakes.". Nature 399 (6735): 474–479.
doi:10.1038/20944. PMID 10365960.
[21] Beldade, P.; Brakefield, P.M.; Long, A.D. (2002). "Contribution of Distal-less to quantitative variation in butterfly eyespots". Nature 415
(6869): 315–318. doi:10.1038/415315a. PMID 11797007.
[22] Baxter, S.W.; Papa, R.; Chamberlain, N.; Humphray, S.J.; Joron, M.; Morrison, C.; ffrench-Constant, R.H.; McMillan, W.O.; Jiggins, C.D.
(2008). "Convergent Evolution in the Genetic Basis of Mullerian Mimicry in Heliconius Butterflies" (http:/ / www. pubmedcentral. nih. gov/
articlerender. fcgi?tool=pmcentrez& artid=2581958). Genetics 180 (3): 1567–1577. doi:10.1534/genetics.107.082982. PMID 18791259.
PMC 2581958.
[23] Gerhart, John; Kirschner, Marc (2007). "The theory of facilitated variation" (http:/ / www. pubmedcentral. nih. gov/ articlerender.
fcgi?tool=pmcentrez& artid=1876433). Proceedings of the National Academy of Sciences 104 (suppl1): 8582–8589.
doi:10.1073/pnas.0701035104. PMID 17494755. PMC 1876433.
[24] Gerhart, John; Kirschner, Marc (1997). Cells, Embryos and Evolution. Blackwell Science. ISBN 978-0865425743.
[25] Carroll, Sean B.; Grenier, Jennifer K.; Weatherbee, Scott D. (2005). From DNA to Diversity: Molecular Genetics and the Evolution of
Animal Design — Second Edition. Blackwell Publishing. ISBN 1405119500.
[26] Carroll, Sean B. (2000). "Endless forms: the evolution of gene regulation and morphological diversity". Cell 101: 577–80.
doi:10.1016/S0092-8674(00)80868-5.
[27] Jablonka, Eva; Lamb, Marion (1995). Epigenetic Inheritance and Evolution: The Lamarckian Dimension. Oxford, New York: Oxford
University Press. ISBN 978-0198540632.
[28] Müller, Gerd B. and Newman, Stuart A., ed (2003). Origination of Organismal Form: Beyond the Gene in Developmental and Evolutionary
Biology. MIT Press.

Sources
• Bowler, Peter J. (2003). Evolution: the history of an idea. Berkeley: University of California Press.
ISBN 0-520-23693-9.
• Desmond, Adrian J. (1989). The politics of evolution: morphology, medicine, and reform in radical London.
Chicago: University of Chicago Press. ISBN 0-226-14374-0.
• Desmond, Adrian J.; Moore, James William (1991). Darwin. London: Michael Joseph. ISBN 0-7181-3430-3.
• Secord, James A. (2003). Victorian sensation: the extraordinary publication, reception, and secret authorship of
Vestiges of the natural history of creation. Chicago: University of Chicago Press. ISBN 0-226-74411-6.

Further reading
• Buss, Leo W. (1987). The Evolution of Individuality. Princeton University Press. ISBN 978-0691084688.
• Carroll, Sean B. (2005). Endless Forms Most Beautiful: The New Science of Evo Devo and the Making of the
Animal Kingdom. Norton. ISBN 9780393060164.
• Goodwin, Brian (1994). How the Leopard Changed its Spots. Phoenix Giants. ISBN 9780691088099.
• Hall, Brian K. & Olsen, Wendy M., ed (2007). Keywords and Concepts in Evolutionary Developmental Biology.
New Delhi, India: Discovery Publishing House. ISBN 978-81-8356-256-0.
• Kirschner, Marc; Gerhart, John (2005). The Plausibility of Life: Resolving Darwin's Dilemma. Yale University
Press. ISBN 9780300108651.
• Laubichler, Manfred D. and Maienschein, Jane, ed (2007). From Embryology to Evo-Devo: A History of
Developmental Evolution. The MIT Press. ISBN 978-0-262-12283-2.
• Minelli, Alessandro (2003). The Development of Animal Form: Ontogeny, Morphology, and Evolution.
Cambridge University Press. ISBN 978-0521808514.
Evolutionary developmental biology 296

• Orr, H. Allen (2005-10-24). "Turned on: A revolution in the field of evolution?" (http://www.newyorker.com/
critics/books/articles/051024crbo_books1). The New Yorker. Discussion of Carroll, Endless Forms Most
Beautiful
• Raff, Rudolf A. (1996). The Shape of Life: Genes, Development, and the Evolution of Animal Form. The
University of Chicago Press. ISBN 978-0226702667.
• Sommer, Ralf J. (2009). "The future of evo–devo: model systems and evolutionary theory". Nature Reviews
Genetics 10 (6): 416–422. doi:10.1038/nrg2567. PMID 19369972.

External links
• Scott F. Gilbert, The morphogenesis of evolutionary developmental biology (http://www.ijdb.ehu.es/
fullaccess/fulltext.03078/ft467.pdf)
• Tardigrades (water bears) as evo-devo models, a short video from NPR's Science Friday (http://www.npr.org/
templates/story/story.php?storyId=99800021)

Molecular evolution
Molecular evolution is the process of evolution at the scale of DNA, RNA, and proteins. Molecular evolution
emerged as a scientific field in the 1960s as researchers from molecular biology, evolutionary biology and
population genetics sought to understand recent discoveries on the structure and function of nucleic acids and
protein. Some of the key topics that spurred development of the field have been the evolution of enzyme function,
the use of nucleic acid divergence as a "molecular clock" to study species divergence, and the origin of
non-functional or junk DNA. Recent advances in genomics, including whole-genome sequencing, high-throughput
protein characterization, and bioinformatics have led to a dramatic increase in studies on the topic. In the 2000s,
some of the active topics have been the role of gene duplication in the emergence of novel gene function, the extent
of adaptive molecular evolution versus neutral drift, and the identification of molecular changes responsible for
various human characteristics especially those pertaining to infection, disease, and cognition.

Principles of molecular evolution

Mutations
Mutations are permanent, transmissible changes to the genetic material (usually DNA or RNA) of a cell. Mutations
can be caused by copying errors in the genetic material during cell division and by exposure to radiation, chemicals,
or viruses, or can occur deliberately under cellular control during the processes such as meiosis or hypermutation.
Mutations are considered the driving force of evolution, where less favorable (or deleterious) mutations are removed
from the gene pool by natural selection, while more favorable (or beneficial) ones tend to accumulate. Neutral
mutations do not affect the organism's chances of survival in its natural environment and can accumulate over time,
which might result in what is known as punctuated equilibrium; the modern interpretation of classic evolutionary
theory.
Molecular evolution 297

Causes of change in allele frequency

There are three known processes that affect the survival of a characteristic; or, more specifically, the frequency of an
allele (variant of a gene):
• Genetic drift describes changes in gene frequency that cannot be ascribed to selective pressures, but are due
instead to events that are unrelated to inherited traits. This is especially important in small mating populations,
which simply cannot have enough offspring to maintain the same gene distribution as the parental generation.
• Gene flow or Migration: or gene admixture is the only one of the agents that makes populations closer genetically
while building larger gene pools.
• Selection, in particular natural selection produced by differential mortality and fertility. Differential mortality is
the survival rate of individuals before their reproductive age. If they survive, they are then selected further by
differential fertility – that is, their total genetic contribution to the next generation. In this way, the alleles that
these surviving individuals contribute to the gene pool will increase the frequency of those alleles. Sexual
selection, the attraction between mates that results from two genes, one for a feature and the other determining a
preference for that feature, is also very important.

Molecular study of phylogeny

Molecular systematics is a product of the traditional field of systematics and molecular genetics. It is the process of
using data on the molecular constitution of biological organisms' DNA, RNA, or both, in order to resolve questions
in systematics, i.e. about their correct scientific classification or taxonomy from the point of view of evolutionary
biology.
Molecular systematics has been made possible by the availability of techniques for DNA sequencing, which allow
the determination of the exact sequence of nucleotides or bases in either DNA or RNA. At present it is still a long
and expensive process to sequence the entire genome of an organism, and this has been done for only a few species.
However, it is quite feasible to determine the sequence of a defined area of a particular chromosome. Typical
molecular systematic analyses require the sequencing of around 1000 base pairs.

The driving forces of evolution

Depending on the relative importance assigned to the various forces of evolution, three perspectives provide
evolutionary explanations for molecular evolution.[1]
While recognizing the importance of random drift for silent mutations,[2] selectionists hypotheses argue that
balancing and positive selection are the driving forces of molecular evolution. Those hypotheses are often based on
the broader view called panselectionism, the idea that selection is the only force strong enough to explain evolution,
relaying random drift and mutations to minor roles.[1]
Neutralists hypotheses emphasize the importance of mutation, purifying selection and random genetic drift.[3] The
introduction of the neutral theory by Kimura,[4] quickly followed by King and Jukes' own findings,[5] lead to a fierce
debate about the relevance of neodarwinism at the molecular level. The Neutral theory of molecular evolution states
that most mutations are deleterious and quickly removed by natural selection, but of the remaining ones, the vast
majority are neutral with respect to fitness while the amount of advantageous mutations is vanishingly small. The
fate of neutral mutations are governed by genetic drift, and contribute to both nucleotide polymorphism and fixed
differences between species.[6] [7] [8]
Mutationists hypotheses emphasize random drift and biases in mutation patterns.[9] Sueoka was the first to propose
a modern mutationist view. He proposed that the variation in GC content was not the result of positive selection, but
a consequence of the GC mutational pressure.[10]
Molecular evolution 298

Related fields
An important area within the study of molecular evolution is the use of molecular data to determine the correct
biological classification of organisms. This is called molecular systematics or molecular phylogenetics.
Tools and concepts developed in the study of molecular evolution are now commonly used for comparative
genomics and molecular genetics, while the influx of new data from these fields has been spurring advancement in
molecular evolution.

Key researchers in molecular evolution

Some researchers who have made key contributions to the development of the field:
• Motoo Kimura — Neutral theory
• Masatoshi Nei — Adaptive evolution
• Walter M. Fitch — Phylogenetic reconstruction
• Walter Gilbert — RNA world
• Joe Felsenstein — Phylogenetic methods
• Susumu Ohno — Gene duplication
• John H. Gillespie — Mathematics of adaptation

Journals and societies

Journals dedicated to molecular evolution include Molecular Biology and Evolution, Journal of Molecular
Evolution, and Molecular Phylogenetics and Evolution. Research in molecular evolution is also published in journals
of genetics, molecular biology, genomics, systematics, or evolutionary biology. The Society for Molecular Biology
and Evolution [11] publishes the journal "Molecular Biology and Evolution" and holds an annual international
meeting.

See also
• History of molecular evolution • Genomic organization • Neutral theory of molecular evolution
• Chemical evolution • Horizontal gene transfer • Nucleotide diversity
• Evolution • Human evolution • Parsimony
• Genetic drift • Evolution of dietary antioxidants • Population genetics
• E. coli long-term evolution experiment • Molecular clock • Selection
• Evolutionary physiology • Comparative phylogenetics

References
[1] Graur, D. and Li, W.-H. (2000). Fundamentals of molecular evolution. Sinauer.
[2] Gillespie, J. H (1991). The Causes of Molecular Evolution. Oxford University Press, New York. ISBN 0-19-506883-1.
[3] Kimura, M. (1983). The Neutral Theory of Molecular Evolution. Cambridge University Press, Cambridge. ISBN 0-521-23109-4.
[4] Kimura, Motoo (1968). "Evolutionary rate at the molecular level" (http:/ / www2. hawaii. edu/ ~khayes/ Journal_Club/ fall2006/
Kimura_1968_Nature. pdf). Nature 217 (5129): 624–626. doi:10.1038/217624a0. PMID 5637732. .
[5] King, J.L. and Jukes, T.H. (1969). "Non-Darwinian Evolution" (http:/ / www. blackwellpublishing. com/ ridley/ classictexts/ king. pdf).
Science 164 (881): 788–798. doi:10.1126/science.164.3881.788. PMID 5767777. .
[6] Nachman M. (2006). "Detecting selection at the molecular level" in: Evolutionary Genetics: concepts and case studies. pp. 103–118.
[7] The nearly neutral theory expanded the neutralist perspective, suggesting that several mutations are nearly neutral, which means both random
drift and natural selection is relevant to their dynamics.
[8] Ohta, T (1992). "The nearly neutral theory of molecular evolution". Annual Review of Ecology and Systematics 23: 263–286.
doi:10.1146/annurev.es.23.110192.001403.
[9] Nei, M. (2005). "Selectionism and Neutralism in Molecular Evolution" (http:/ / www. pubmedcentral. nih. gov/ articlerender.
fcgi?tool=pmcentrez& artid=1513187). Molecular Biology and Evolution 22 (12): 2318–2342. doi:10.1093/molbev/msi242. PMID 16120807.
Molecular evolution 299

PMC 1513187.
[10] Sueoka, N. (1964). "On the evolution of informational macromolecules". In In: Bryson, V. and Vogel, H.J.. Evolving genes and proteins.
Academic Press, New-York. pp. 479–496.
[11] http:/ / www. smbe. org

Further reading
• Li, W.-H. (2006). Molecular Evolution. Sinauer. ISBN 0878934804.
• Lynch, M. (2007). The Origins of Genome Architecture. Sinauer. ISBN 0878934847.

Human evolution
Human evolution, or anthropogenesis, is the origin and evolution of Homo sapiens as a distinct species from other
hominids, great apes and placental mammals. The study of human evolution encompasses many scientific
disciplines, including physical anthropology, primatology, archaeology, linguistics and genetics.[1]
The term "human" in the context of human evolution refers to the genus Homo, but studies of human evolution
usually include other hominids, such as the Australopithecines, from which the genus Homo had diverged by about
2.3 to 2.4 million years ago in Africa.[2] [3] Scientists have estimated that humans branched off from their common
ancestor with chimpanzees about 5–7 million years ago. Several species and subspecies of Homo evolved and are
now extinct. These include Homo erectus, which inhabited Asia, and Homo sapiens neanderthalensis, which
inhabited Europe. Archaic Homo sapiens evolved between 400,000 and 250,000 years ago.
The dominant view among scientists concerning the origin of anatomically modern humans is the "Out of Africa" or
recent African origin hypothesis,[4] [5] [6] [7] which argues that Homo sapiens arose in Africa and migrated out of the
continent around 50,000 to 100,000 years ago, replacing populations of Homo erectus in Asia and Homo
neanderthalensis in Europe. Scientists supporting the alternative multiregional hypothesis argue that Homo sapiens
evolved as geographically separate but interbreeding populations stemming from a worldwide migration of Homo
erectus out of Africa nearly 2.5 million years ago.

History of ideas
The word homo, the name of the biological genus to which humans belong, is Latin for "human". It was chosen
originally by Carolus Linnaeus in his classification system. The word "human" is from the Latin humanus, the
adjectival form of homo. The Latin "homo" derives from the Indo-European root, dhghem, or "earth".[8]
Carolus Linnaeus and other scientists of his time also considered the great apes to be the closest relatives of humans
due to morphological and anatomical similarities. The possibility of linking humans with earlier apes by descent only
became clear after 1859 with the publication of Charles Darwin's On the Origin of Species. This argued for the idea
of the evolution of new species from earlier ones. Darwin's book did not address the question of human evolution,
saying only that "Light will be thrown on the origin of man and his history".
Human evolution 300

The first debates about the nature of human evolution arose

between Thomas Huxley and Richard Owen. Huxley argued
for human evolution from apes by illustrating many of the
similarities and differences between humans and apes and did
so particularly in his 1863 book Evidence as to Man's Place in
Nature. However, many of Darwin's early supporters (such as
Alfred Russel Wallace and Charles Lyell) did not agree that
the origin of the mental capacities and the moral sensibilities
of humans could be explained by natural selection. Darwin
applied the theory of evolution and sexual selection to humans
when he published The Descent of Man in 1871.[9]

A major problem was the lack of fossil intermediaries. It was

only in the 1920s that such fossils were discovered in Africa.
In 1925, Raymond Dart described Australopithecus africanus. Fossil Hominid Evolution Display at The Museum of
The type specimen was the Taung Child, an Australopithecine Osteology, Oklahoma City, USA.
infant discovered in a cave. The child's remains were a
remarkably well-preserved tiny skull and an endocranial cast of the individual's brain. Although the brain was small
(410 cm³), its shape was rounded, unlike that of chimpanzees and gorillas, and more like a modern human brain.
Also, the specimen showed short canine teeth, and the position of the foramen magnum was evidence of bipedal
locomotion. All of these traits convinced Dart that the Taung baby was a bipedal human ancestor, a transitional form
between apes and humans.

The classification of humans and their relatives has changed considerably over time. The gracile Australopithecines
are now thought to be ancestors of the genus Homo, the group to which modern humans belong. Both
Australopithecines and Homo sapiens are part of the tribe Hominini. Recent data suggests Australopithecines were a
diverse group and that A. africanus may not be a direct ancestor of modern humans. Reclassification of
Australopithecines that originally were split into either gracile or robust varieties has put the latter into a family of its
own, Paranthropus. Taxonomists place humans, Australopithecines and related species in the same family as other
great apes, in the Hominidae.

Hominin species distributed through time

Note: 1e+06 years = 1 × 106 years = 1 million years ago = 1 Ma

Human evolution 301

Before Homo

Evolution of the great apes

The evolutionary history of the primates can be traced back 65 million
years, as one of the oldest of all surviving placental mammal groups.
The oldest known primate-like mammal species, the Plesiadapis, come
from North America, but they were widespread in Eurasia and Africa
during the tropical conditions of the Paleocene and Eocene.

Plesiadapis.

With the beginning of modern climates, marked by the formation of

the first Antarctic ice in the early Oligocene around 30 million years
ago. A primate from this time was Notharctus. Fossil evidence found
in Germany in the 1980s was determined to be about 16.5 million years
old, some 1.5 million years older than similar species from East Africa
and challenging the original theory regarding human ancestry
originating on the African continent.

David Begun[10] says that these primates flourished in Eurasia and that
the lineage leading to the African apes and humans— including Notharctus.
Dryopithecus—migrated south from Europe or Western Asia into
Africa. The surviving tropical population, which is seen most completely in the upper Eocene and lowermost
Oligocene fossil beds of the Fayum depression southwest of Cairo, gave rise to all living primates—lemurs of
Madagascar, lorises of Southeast Asia, galagos or "bush babies" of Africa, and the anthropoids; platyrrhines or New
World monkeys, and catarrhines or Old World monkeys and the great apes and humans.

The earliest known catarrhine is Kamoyapithecus from uppermost Oligocene at Eragaleit in the northern Kenya Rift
Valley, dated to 24 million years ago. Its ancestry is generally thought to be species related to Aegyptopithecus,
Propliopithecus, and Parapithecus from the Fayum, at around 35 million years ago. In 2010, Saadanius was
described as a close relative of the last common ancestor of the crown catarrhines, and tentatively dated to 29–28
million years ago, helping to fill an 11-million-year gap in the fossil record.[11]
In the early Miocene, about 22 million years ago, the many kinds of
arboreally adapted primitive catarrhines from East Africa suggest a
long history of prior diversification. Fossils at 20 million years ago
include fragments attributed to Victoriapithecus, the earliest Old World
Monkey. Among the genera thought to be in the ape lineage leading up
to 13 million years ago are Proconsul, Rangwapithecus,
Dendropithecus, Limnopithecus, Nacholapithecus, Equatorius,
Nyanzapithecus, Afropithecus, Heliopithecus, and Kenyapithecus, all
from East Africa. The presence of other generalized non-cercopithecids
Reconstructed tailless Proconsul skeleton.
of middle Miocene age from sites far distant—Otavipithecus from cave
deposits in Namibia, and Pierolapithecus and Dryopithecus from
France, Spain and Austria—is evidence of a wide diversity of forms across Africa and the Mediterranean basin
during the relatively warm and equable climatic regimes of the early and middle Miocene. The youngest of the
Miocene hominoids, Oreopithecus, is from 9 million year old coal beds in Italy.
Human evolution 302

Molecular evidence indicates that the lineage of gibbons (family Hylobatidae) became distinct from Great Apes
between 18 and 12 million years ago, and that of orangutans (subfamily Ponginae) became distinct from the other
Great Apes at about 12 million years; there are no fossils that clearly document the ancestry of gibbons, which may
have originated in a so-far-unknown South East Asian hominoid population, but fossil proto-orangutans may be
represented by Ramapithecus from India and Griphopithecus from Turkey, dated to around 10 million years ago.

Divergence of the human lineage from other Great Apes

Species close to the last common ancestor of gorillas, chimpanzees and humans may be represented by
Nakalipithecus fossils found in Kenya and Ouranopithecus found in Greece. Molecular evidence suggests that
between 8 and 4 million years ago, first the gorillas, and then the chimpanzees (genus Pan) split off from the line
leading to the humans; human DNA is approximately 98.4% identical to that of chimpanzees when comparing single
nucleotide polymorphisms (see human evolutionary genetics). The fossil record of gorillas and chimpanzees is quite
limited. Both poor preservation (rain forest soils tend to be acidic and dissolve bone) and sampling bias probably
contribute to this problem.
Other hominines likely adapted to the drier environments outside the equatorial belt, along with antelopes, hyenas,
dogs, pigs, elephants, and horses. The equatorial belt contracted after about 8 million years ago. Fossils of these
hominans - the species in the human lineage following divergence from the chimpanzees - are relatively well known.
The earliest are Sahelanthropus tchadensis (7 Ma) and Orrorin tugenensis (6 Ma), followed by:
• Ardipithecus (5.5–4.4 Ma), with species Ar. kadabba and Ar. ramidus;
• Australopithecus (4–1.8 Ma), with species Au. anamensis, Au. afarensis, Au. africanus, Au. bahrelghazali, Au.
garhi, and Au. sediba;
• Kenyanthropus (3–2.7 Ma), with species Kenyanthropus platyops;
• Paranthropus (3–1.2 Ma), with species P. aethiopicus, P. boisei, and P. robustus;
• Homo (2 Ma–present), with species Homo habilis, Homo rudolfensis, Homo ergaster, Homo georgicus, Homo
antecessor, Homo cepranensis, Homo erectus, Homo heidelbergensis, Homo rhodesiensis, Homo
neanderthalensis, Homo sapiens idaltu, Archaic Homo sapiens, Homo floresiensis.

Genus Homo
Homo sapiens is the only extant species of its genus, Homo. While some other, extinct, Homo species might have
been ancestors of Homo sapiens, many were likely our "cousins", having speciated away from our ancestral line.[12]
[13]
There is not yet a consensus as to which of these groups should count as separate species and which as
subspecies. In some cases this is due to the dearth of fossils, in other cases it is due to the slight differences used to
classify species in the Homo genus.[13] The Sahara pump theory (describing an occasionally passable "wet" Sahara
Desert) provides an explanation of the early variation in the genus Homo.
Based on archaeological and paleontological evidence, it has been possible to infer, to some extent, the ancient
dietary practices of various Homo species and to study the role of diet in physical and behavioral evolution within
Homo.[14] [15] [16] [17] [18]

H. habilis
Homo habilis lived from about 2.4 to 1.4 Ma. Homo habilis, the first species of the genus Homo, evolved in South
and East Africa in the late Pliocene or early Pleistocene, 2.5–2 Ma, when it diverged from the Australopithecines.
Homo habilis had smaller molars and larger brains than the Australopithecines, and made tools from stone and
perhaps animal bones. One of the first known hominids, it was nicknamed 'handy man' by its discoverer, Louis
Leakey due to its association with stone tools. Some scientists have proposed moving this species out of Homo and
into Australopithecus due to the morphology of its skeleton being more adapted to living on trees rather than to
moving on two legs like Homo sapiens.[19]
Human evolution 303

H. rudolfensis and H. georgicus

These are proposed species names for fossils from about 1.9–1.6 Ma, the relation of which with Homo habilis is not
yet clear.
• Homo rudolfensis refers to a single, incomplete skull from Kenya. Scientists have suggested that this was another
Homo habilis, but this has not been confirmed.[20]
• Homo georgicus, from Georgia, may be an intermediate form between Homo habilis and Homo erectus,[21] or a
sub-species of Homo erectus.[22]

H. ergaster and H. erectus

The first fossils of Homo erectus were
discovered by Dutch physician Eugene
Dubois in 1891 on the Indonesian
island of Java. He originally gave the
material the name Pithecanthropus
erectus based on its morphology that
he considered to be intermediate
between that of humans and apes.[24]
Homo erectus (H erectus) lived from
about 1.8 Ma to about 70,000 years
ago (which would indicate that they
were probably wiped out by the Toba
catastrophe; however, Homo erectus
soloensis and Homo floresiensis
survived it). Often the early phase,
from 1.8 to 1.25 Ma, is considered to
be a separate species, Homo ergaster,
or it is seen as a subspecies of Homo
erectus, Homo erectus ergaster. In the
early Pleistocene, 1.5–1 Ma, in Africa,
Asia, and Europe, some populations of
Homo habilis are thought to have
evolved larger brains and made more One current view of the temporal and geographical distribution of hominid
[23]
elaborate stone tools; these differences populations. Other interpretations differ mainly in the taxonomy and geographical
and others are sufficient for distribution of hominid species.

anthropologists to classify them as a

new species, Homo erectus. In addition Homo erectus was the first human ancestor to walk truly upright.[25] This
was made possible by the evolution of locking knees and a different location of the foramen magnum (the hole in the
skull where the spine enters). They may have used fire to cook their meat.

A famous example of Homo erectus is Peking Man; others were found in Asia (notably in Indonesia), Africa, and
Europe. Many paleoanthropologists now use the term Homo ergaster for the non-Asian forms of this group, and
reserve Homo erectus only for those fossils that are found in Asia and meet certain skeletal and dental requirements
which differ slightly from H. ergaster.
Human evolution 304

H. cepranensis and H. antecessor

These are proposed as species that may be intermediate between H. erectus and H. heidelbergensis.
• H. antecessor is known from fossils from Spain and England that are dated 1.2 Ma–500 ka.[26] [27]
• H. cepranensis refers to a single skull cap from Italy, estimated to be about 800,000 years old.[28]

H. heidelbergensis
H. heidelbergensis (Heidelberg Man) lived from about 800,000 to about 300,000 years ago. Also proposed as Homo
sapiens heidelbergensis or Homo sapiens paleohungaricus.[29]

H. rhodesiensis, and the Gawis cranium

• H. rhodesiensis, estimated to be 300,000–125,000 years old. Most current experts believe Rhodesian Man to be
within the group of Homo heidelbergensis, though other designations such as Archaic Homo sapiens and Homo
sapiens rhodesiensis have also been proposed.
• In February 2006 a fossil, the Gawis cranium, was found which might possibly be a species intermediate between
H. erectus and H. sapiens or one of many evolutionary dead ends. The skull from Gawis, Ethiopia, is believed to
be 500,000–250,000 years old. Only summary details are known, and no peer reviewed studies have been
released by the finding team. Gawis man's facial features suggest its being either an intermediate species or an
example of a "Bodo man" female.[30]

H. neanderthalensis
H. neanderthalensis lived from 400,000[31] years ago. Also
proposed as Homo sapiens neanderthalensis: there is ongoing
debate over whether the "Neanderthal Man" was a separate
species, Homo neanderthalensis, or a subspecies of H. sapiens.[32]
While the debate remains unsettled, evidence from sequencing
mitochondrial DNA indicates that no significant gene flow
occurred between H. neanderthalensis and H. sapiens, and,
therefore, the two were separate species that shared a common
ancestor about 660,000 years ago.[33] [34] In 1997, Mark Stoneking
stated: "These results [based on mitochondrial DNA extracted
from Neanderthal bone] indicate that Neanderthals did not
Le Ferrassie Neanderthal skull (cast)
contribute mitochondrial DNA to modern humans… Neanderthals
are not our ancestors." Subsequent investigation of a second
source of Neanderthal DNA supported these findings.[35] However, the 2010 sequencing of the Neanderthal genome
indicates that Neanderthals did indeed interbreed with H. sapiens circa 75,000 BC (after H. sapiens moved out from
Africa, but before they separated into Europe, the Middle East, and Asia).[36] Nearly all modern humans have 1% to
4% of their DNA derived from Neanderthal DNA.[36] (To appreciate how big of a percentage this is, consider that
humans and chimps only differ in 1.5% of their DNA.) This 1-4% bit of DNA is only present in non-African
humans.[36] However, supporters of the multiregional hypothesis point to recent studies indicating non-African
nuclear DNA heritage dating to one Ma,[37] although the reliability of these studies has been questioned.[38]
Competition from Homo sapiens probably contributed to Neanderthal extinction.[39] [40] They could have coexisted
in Europe for as long as 10,000 years.[41]
Human evolution 305

H. sapiens
H. sapiens (the adjective sapiens is Latin for "wise" or "intelligent") have lived from about 250,000 years ago to the
present. Between 400,000 years ago and the second interglacial period in the Middle Pleistocene, around 250,000
years ago, the trend in skull expansion and the elaboration of stone tool technologies developed, providing evidence
for a transition from H. erectus to H. sapiens. The direct evidence suggests there was a migration of H. erectus out of
Africa, then a further speciation of H. sapiens from H. erectus in Africa. A subsequent migration within and out of
Africa eventually replaced the earlier dispersed H. erectus. This migration and origin theory is usually referred to as
the recent single origin or Out of Africa theory. Current evidence does not preclude some multiregional evolution or
some admixture of the migrant H. sapiens with existing Homo populations. This is a hotly debated area of
paleoanthropology.
Current research has established that humans are genetically highly homogenous; that is, the DNA of individuals is
more alike than usual for most species, which may have resulted from their relatively recent evolution or the
possibility of a population bottleneck resulting from cataclysmic natural events such as the Toba catastrophe.[42] [43]
[44]
Distinctive genetic characteristics have arisen, however, primarily as the result of small groups of people moving
into new environmental circumstances. These adapted traits are a very small component of the Homo sapiens
genome, but include various characteristics such as skin color and nose form, in addition to internal characteristics
such as the ability to breathe more efficiently in high altitudes.
H. sapiens idaltu, from Ethiopia, is a possible extinct sub-species who lived from about 160,000 years ago.

H. floresiensis
H. floresiensis, which lived from approximately 100,000 to 12,000 before present, has been nicknamed hobbit for its
small size, possibly a result of insular dwarfism.[45] H. floresiensis is intriguing both for its size and its age, being a
concrete example of a recent species of the genus Homo that exhibits derived traits not shared with modern humans.
In other words, H. floresiensis share a common ancestor with modern humans, but split from the modern human
lineage and followed a distinct evolutionary path. The main find was a skeleton believed to be a woman of about 30
years of age. Found in 2003 it has been dated to approximately 18,000 years old. The living woman was estimated to
be one meter in height, with a brain volume of just 380 cm3 (considered small for a chimpanzee and less than a third
of the H. sapiens average of 1400 cm3).
However, there is an ongoing debate over whether H. floresiensis is indeed a separate species.[46] Some scientists
presently believe that H. floresiensis was a modern H. sapiens suffering from pathological dwarfism.[47] This
hypothesis is supported in part, because some modern humans who live on Flores, the island where the skeleton was
found, are pygmies. This coupled with pathological dwarfism, it is argued, could indeed create a hobbit-like human.
The other major attack on H. floresiensis is that it was found with tools only associated with H. sapiens.[47]
The hypothesis of pathological dwarfism, however, fails to explain additional anatomical features that are unlike
those of modern humans (diseased or not) but much like those of ancient members of our genus. Aside from cranial
features, these features include the form of bones in the wrist, forearm, shoulder, knees, and feet.

Denisova hominin
In 2008, archeologists working at the site of Denisova Cave in the Altai Mountains of Siberia uncovered a small
bone fragment from the fifth finger of a juvenile hominin, dubbed the "X-woman" (referring to the maternal descent
of mitochondrial DNA[48] , or the Denisova hominin. Artifacts, including a bracelet, excavated in the cave at the
same level were carbon dated to around 40,000 BP. As DNA had survived in the fossil fragment due to the cool
climate of the Denisova Cave, a team of scientists from the Max Planck Institute for Evolutionary Anthropology in
Leipzig, Germany sequenced mtDNA extracted from the fragment.[49]
Human evolution 306

The analysis indicated that modern humans, Neanderthals, and the Denisova hominin last shared a common ancestor
around 1 million years ago.[50] Modern humans are known to have overlapped with Neanderthals in Europe for more
than 10,000 years, and the discovery raises the possibility that Neanderthals, modern humans and the Denisovan
hominin may have co-existed together.
The DNA analysis further indicated that this new hominin species was the result of an early migration out of Africa,
distinct from the later out-of-Africa migrations associated with Neanderthals and modern humans, but also distinct
from the earlier African exodus of Homo erectus.[50] Professor Chris Stringer, human origins researcher at London's
Natural History Museum and one of the leading proponents of the recent single-origin hypothesis, remarked: "This
new DNA work provides an entirely new way of looking at the still poorly understood evolution of humans in
central and eastern Asia." Pääbo noted that the existence of this distant branch creates a much more complex picture
of humankind during the Late Pleistocene.[48]

Comparative table of Homo species

Species Lived when Lived where Adult Adult mass Cranial Fossil Discovery /
(Ma) height capacity (cm³) record publication of
name

H. antecessor 1.2 – 0.8 Spain 1.75 m (5.7 90 kg (200 lb) 1,000 2 sites 1997
ft)

H. cepranensis 0.9 – 0.8? Italy 1,000 1 skull cap 1994/2003

H. erectus 1.5 – 0.2 Africa, Eurasia 1.8 m (5.9 60 kg (130 lb) 850 (early) – Many 1891/1892
(Java, China, India, ft) 1,100 (late)
Caucasus)

H. ergaster 1.9 – 1.4 Eastern and 1.9 m (6.2 700–850 Many 1975

Southern Africa ft)

H. floresiensis 0.10? – 0.012 Indonesia 1.0 m (3.3 25 kg (55 lb) 400 7 2003/2004
ft) individuals

H. gautengensis >2 – 0.6 South Africa 1.0 m (3.3 2010

ft)

H. georgicus 1.8 600 4 1999/2002

individuals

H. habilis 2.3 – 1.4 Africa 1.0–1.5 m 33–55 kg 510–660 Many 1960/1964

(3.3–4.9 ft) (73–120 lb)

H. heidelbergensis 0.6 – 0.35 Europe, Africa, 1.8 m (5.9 60 kg (130 lb) 1,100–1,400 Many 1908
China ft)

H. neanderthalensis 0.35 – 0.03 Europe, Western 1.6 m (5.2 55–70 kg 1,200–1,900 Many (1829)/1864
Asia ft) (120–150 lb)
(heavily built)

H. rhodesiensis 0.3 – 0.12 Zambia 1,300 Very few 1921

H. rudolfensis 1.9 Kenya 1 skull 1972/1986

H. sapiens idaltu 0.16 – 0.15 Ethiopia 1,450 3 craniums 1997/2003

H. sapiens sapiens 0.2 – present Worldwide 1.4–1.9 m 50–100 kg 1,000–1,850 Still living —/1758

(modern humans) (4.6–6.2 ft) (110–220 lb)
Human evolution 307

Use of tools
Using tools has been interpreted as a sign of intelligence, and it
has been theorized that tool use may have stimulated certain
aspects of human evolution—most notably the continued
expansion of the human brain. Paleontology has yet to explain the
expansion of this organ over millions of years despite being
extremely demanding in terms of energy consumption. The brain
of a modern human consumes about 20 watts (400 kilocalories per
day), which is one fifth of the energy consumption of a human
body. Increased tool use would allow hunting for energy-rich meat
products, and would enable processing more energy-rich plant
"A sharp rock", an Oldowan pebble tool, the most basic
products. Researchers have suggested that early hominids were of human stone tools
thus under evolutionary pressure to increase their capacity to
create and use tools.[51]

Precisely when early humans started to use tools is difficult to

determine, because the more primitive these tools are (for
example, sharp-edged stones) the more difficult it is to decide
whether they are natural objects or human artifacts. There is some
evidence that the australopithecines (4 Ma) may have used broken
bones as tools, but this is debated.
It should be noted that many species make and use tools, but it is
the human species that dominates the areas of making and using
more complex tools. The oldest known tools are the "Oldowan
Fire, one of the greatest human discoveries
stone tools" from Ethiopia. It was discovered that these tools are
from 2.5 to 2.6 million years old, which predates the earliest
known "Homo" species. There is no known evidence that any
"Homo" specimens appeared by 2.5 Ma. A Homo fossil was found
near some Oldowan tools, and its age was noted at 2.3 million
years old, suggesting that maybe the Homo species did indeed
create and use these tools. It is surely possible, but not solid
evidence. Bernard Wood noted that "Paranthropus" coexisted with
the early Homo species in the area of the "Oldowan Industrial
Complex" over roughly the same span of time. Although there is
no direct evidence that points to Paranthropus as the tool makers,
their anatomy lends to indirect evidence of their capabilities in this
An Acheulean hand axe, the pinnacle of Homo erectus
area. Most paleoanthropologists agree that the early "Homo"
stone working
species were indeed responsible for most of the Oldowan tools
found. They argue that when most of the Oldowan tools were
found in association with human fossils, Homo was always present, but Paranthropus was not.[52]

In 1994, Randall Susman used the anatomy of opposable thumbs as the basis for his argument that both the Homo
and Paranthropus species were toolmakers. He compared bones and muscles of
Human evolution 308

human and chimpanzee thumbs, finding that humans have 3

muscles that chimps lack. Humans also have thicker metacarpals
with broader heads, making the human hand more successful at
precision grasping than the chimpanzee hand. Susman defended
that modern anatomy of the human thumb is an evolutionary
response to the requirements associated with making and handling
tools and that both species were indeed toolmakers.[52]

Stone tools
Stone tools are first attested around 2.6 Ma, when H. habilis in
Eastern Africa used so-called pebble tools, choppers made out of
round pebbles that had been split by simple strikes.[53] This marks
the beginning of the Paleolithic, or Old Stone Age; its end is taken
to be the end of the last Ice Age, around 10,000 years ago. The
Paleolithic is subdivided into the Lower Paleolithic (Early Stone
Age, ending around 350,000–300,000 years ago), the Middle
Paleolithic (Middle Stone Age, until 50,000–30,000 years ago),
and the Upper Paleolithic.

The period from 700,000–300,000 years ago is also known as the

Acheulean, when H. ergaster (or erectus) made large stone Venus of Willendorf, an example of Paleolithic art
hand-axes out of flint and quartzite, at first quite rough (Early
Acheulian), later "retouched" by additional, more subtle strikes at the sides of the flakes. After 350,000 BP (Before
Present) the more refined so-called Levallois technique was developed. It consisted of a series of consecutive strikes,
by which scrapers, slicers ("racloirs"), needles, and flattened needles were made.[53] Finally, after about 50,000 BP,
ever more refined and specialized flint tools were made by the Neanderthals and the immigrant Cro-Magnons
(knives, blades, skimmers). In this period they also started to make tools out of bone.

Modern humans and the "Great Leap Forward" debate

Until about 50,000–40,000 years ago the use of stone tools seems to have progressed stepwise. Each phase (H.
habilis, H. ergaster, H. neanderthalensis) started at a higher level than the previous one, but once that phase started
further development was slow. These Homo species were culturally conservative, but after 50,000 BC modern
human culture started to change at a much greater speed. Jared Diamond, author of The Third Chimpanzee, and some
anthropologists characterize this as a "Great Leap Forward".
Modern humans started burying their dead, making clothing out of hides, developing sophisticated hunting
techniques (such as using trapping pits or driving animals off cliffs), and engaging in cave painting.[54] As human
culture advanced, different populations of humans introduced novelty to existing technologies: artifacts such as fish
hooks, buttons and bone needles show signs of variation among different populations of humans, something that had
not been seen in human cultures prior to 50,000 BP. Typically, H. neanderthalensis populations do not vary in their
technologies.
Among concrete examples of Modern human behavior, anthropologists include specialization of tools, use of
jewellery and images (such as cave drawings), organization of living space, rituals (for example, burials with grave
gifts), specialized hunting techniques, exploration of less hospitable geographical areas, and barter trade networks.
Debate continues as to whether a "revolution" led to modern humans ("the big bang of human consciousness"), or
whether the evolution was more gradual.[55]
Human evolution 309

Models of human evolution

Today, all humans belong to one, undivided by species barrier, population of Homo sapiens sapiens. However,
according to the "Out of Africa" model this is not the first species of hominids: the first species of genus Homo,
Homo habilis, evolved in East Africa at least 2 Ma, and members of this species populated different parts of Africa
in a relatively short time. Homo erectus evolved more than 1.8 Ma, and by 1.5 Ma had spread throughout the Old
World.
Anthropologists have been divided as to whether current human population evolved as one interconnected
population (as postulated by the Multiregional Evolution hypothesis), or evolved only in East Africa, speciated, and
then migrating out of Africa and replaced human populations in Eurasia (called the "Out of Africa" Model or the
"Complete Replacement" Model).

Multiregional model
Multiregional evolution, a model to account for the pattern of human evolution, was proposed by Milford H.
Wolpoff[56] in 1988.[57] Multiregional evolution holds that human evolution from the beginning of the Pleistocene
2.5 million years BP to the present day has been within a single, continuous human species, evolving worldwide to
modern Homo sapiens.
According to the multiregional hypothesis, fossil and genomic data are evidence for worldwide human evolution and
contradict the recent speciation postulated by the Recent African origin hypothesis. The fossil evidence was
insufficient for Richard Leakey to resolve this debate.[58] Studies of haplogroups in Y-chromosomal DNA and
mitochondrial DNA have largely supported a recent African origin.[59] Evidence from autosomal DNA also supports
the Recent African origin. However the presence of archaic admixture in modern humans remains a possibility and
has been suggested by some studies.[60]

Out of Africa
According to the Out of Africa model, developed by Chris Stringer and Peter Andrews, modern H. sapiens evolved
in Africa 200,000 years ago. Homo sapiens began migrating from Africa between 70,000 – 50,000 years ago and
eventually replaced existing hominid species in Europe and Asia.[61] [62] Out of Africa has gained support from
research using mitochondrial DNA (mtDNA). After analysing genealogy trees constructed using 133 types of
mtDNA, researchers concluded that all were descended from a woman from Africa, dubbed Mitochondrial Eve. Out
of Africa is also supported by the fact that mitochondrial genetic diversity is highest among African populations.[63]
There are differing theories on whether there was a single exodus or several. A multiple dispersal model involves the
Southern Dispersal theory,[64] which has gained support in recent years from genetic, linguistic and archaeological
evidence. In this theory, there was a coastal dispersal of modern humans from the Horn of Africa around 70,000
years ago. This group helped to populate Southeast Asia and Oceania, explaining the discovery of early human sites
in these areas much earlier than those in the Levant. A second wave of humans dispersed across the Sinai peninsula
into Asia, resulting in the bulk of human population for Eurasia. This second group possessed a more sophisticated
tool technology and was less dependent on coastal food sources than the original group. Much of the evidence for the
first group's expansion would have been destroyed by the rising sea levels at the end of the Holocene era.[64] The
multiple dispersal model is contradicted by studies indicating that the populations of Eurasia and the populations of
Southeast Asia and Oceania are all descended from the same mitochondrial DNA lineages, which support a single
migration out of Africa that gave rise to all non-African populations.[65]
The broad study of African genetic diversity headed by Dr. Sarah Tishkoff found the San people to express the
greatest genetic diversity among the 113 distinct populations sampled, making them one of 14 "ancestral population
clusters". The research also located the origin of modern human migration in south-western Africa, near the coastal
border of Namibia and Angola.[66]
Human evolution 310

According to the Toba catastrophe theory to which some anthropologists and archeologists subscribe, the
supereruption of Lake Toba on Sumatra island in Indonesia roughly 70,000 years ago had global consequences,[67]
killing most humans then alive and creating a population bottleneck that affected the genetic inheritance of all
humans today.[68]

Recent and current human evolution

Natural selection is being observed in contemporary human populations, with recent findings demonstrating the
population which is at risk of the severe debilitating disease kuru has significant over-representation of an immune
variant of the prion protein gene G127V versus non-immune alleles. Scientists postulate one of the reasons for the
rapid selection of this genetic variant is the lethality of the disease in non-immune persons.[69] [70] Other reported
evolutionary trends in other populations include a lengthening of the reproductive period, reduction in cholesterol
levels, blood glucose and blood pressure.[71]
In their 2009 book The 10,000 Year Explosion, Gregory Cochran and Henry Harpending argue that human evolution
has accelerated since and as a result of the development of agriculture and civilisation since some 50,000 years ago,
and that there are consequently substantial genetic differences between different current human populations.

Genetics
Human evolutionary genetics studies how one human genome differs from the other, the evolutionary past that gave
rise to it, and its current effects. Differences between genomes have anthropological, medical and forensic
implications and applications. Genetic data can provide important insight into human evolution.

Notable human evolution researchers

• Robert Broom, a Scottish physician and palaeontologist whose work on South Africa led to the discovery and
description of the Paranthropus genus of hominins, and of "Mrs. Ples"
• James Burnett, Lord Monboddo, a British judge most famous today as a founder of modern comparative historical
linguistics
• Raymond Dart, an Australian anatomist and palaeoanthropologist, whose work at Taung, in South Africa, led to
the discovery of Australopithecus africanus
• Charles Darwin, a British naturalist who documented considerable evidence that species originate through
evolutionary change
• Richard Dawkins, a British ethologist, evolutionary biologist who has promoted a gene-centered view of
evolution
• J. B. S. Haldane, a British geneticist and evolutionary biologist
• William D. Hamilton, a British Evolutionary Biologist who expounded a rigorous genetic basis for kin selection,
and on the evolution of HIV and other human diseases.
• Sir Alister Hardy, a British zoologist, who first hypothesised the aquatic ape theory of human evolution
• Henry McHenry, an American anthropologist who specializes in studies of human evolution, the origins of
bipedality, and paleoanthropology
• Jeffrey Laitman, an American anatomist and physical anthropologist whose work has explored the evolution of
the vocal tract and speech
• Louis Leakey, an African archaeologist and naturalist whose work was important in establishing human
evolutionary development in Africa
• Mary Leakey, a British archaeologist and anthropologist whose discoveries in Africa include the Laetoli
footprints
• Richard Leakey, an African paleontologist and archaeologist, son of Louis and Mary Leakey
Human evolution 311

• Svante Pääbo, a Swedish biologist specializing in evolutionary genetics

• David Pilbeam, a paleoanthropologist, researcher and writer on a range of topics involving human and primate
evolution.
• Jeffrey H. Schwartz, an American physical anthropologist and professor of biological anthropology
• Chris Stringer, anthropologist, leading proponent of the recent single origin hypothesis
• Alan Templeton, geneticist and statistician, proponent of the multiregional hypothesis
• Philip V. Tobias, a South African palaeoanthropologist is one of the world's leading authorities on the evolution
of humankind
• Erik Trinkaus, a prominent American paleoanthropologist and expert on Neanderthal biology and human
evolution
• Alfred Russel Wallace, a British naturalist, sometimes called the "father of biogeography", who independently
from Charles Darwin proposed the principles of evolution of animal species
• Milford H. Wolpoff, an American paleoanthropologist who is the leading proponent of the multiregional
evolution hypothesis.
• Pardis Sabeti, an Iranian American evolutionary geneticist who developed a statistical method which identifies
sections of the genome that have been subject to natural selection

Species list
This list is in chronological order across the page by genus.

• Sahelanthropus • Australopithecus • Homo

• Sahelanthropus tchadensis • Australopithecus anamensis • Homo habilis
• Orrorin • Australopithecus afarensis • Homo rudolfensis
• Orrorin tugenensis • Australopithecus bahrelghazali • Homo ergaster
• Ardipithecus • Australopithecus africanus • Homo georgicus
• Australopithecus garhi • Homo erectus
• Ardipithecus kadabba
• Australopithecus sediba • Homo cepranensis
• Ardipithecus ramidus
• Paranthropus • Homo antecessor
• Paranthropus aethiopicus • Homo heidelbergensis
• Paranthropus boisei • Homo rhodesiensis
• Paranthropus robustus • Homo neanderthalensis
• Kenyanthropus • Homo sapiens idaltu
• Homo sapiens (Cro-Magnon)
• Kenyanthropus platyops
• Homo sapiens sapiens
• Homo floresiensis

See also
• List of human evolution fossils • Evolutionary psychology
• Timeline of human evolution • History of Earth
• Archaeogenetics • Hominid intelligence
• Dual inheritance theory • Human behavioral ecology
• Dysgenics • Human skeletal changes due to bipedalism
• Evolutionary anthropology • Human vestigiality
• Evolutionary medicine • Ida (fossil)
• Evolutionary neuroscience • Pan prior
• Evolution of human intelligence • Physical anthropology
• Evolution of morality • Sahara pump theory
• Evolutionary origin of religions • Sexual selection in human evolution
• Sociocultural evolution
Human evolution 312

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doi:10.1056/NEJMoa0809716. PMID 19923577.
[71] Byars, S. G.; Ewbank, D.; Govindaraju, D. R.; Stearns, S. C. (2009). "Evolution in Health and Medicine Sackler Colloquium: Natural
selection in a contemporary human population" (http:/ / www. pubmedcentral. nih. gov/ articlerender. fcgi?tool=pmcentrez& artid=2868295).
Proceedings of the National Academy of Sciences 107: 1787. doi:10.1073/pnas.0906199106. PMID 19858476. PMC 2868295.

Further reading
• Hill, Andrew; Ward, Steven (1988). "Origin of the hominidae: The record of african large hominoid evolution
between 14 my and 4 my". Yearbook of Physical Anthropology 31 (59): 49–83. doi:10.1002/ajpa.1330310505
• Alexander, R. D. (1990). "How Did Humans Evolve? Reflections on the Uniquely Unique Species" (http://
insects.ummz.lsa.umich.edu/pdfs/Alexander1990.pdf). University of Michigan Museum of Zoology Special
Publication (University of Michigan Museum of Zoology) (1): 1–38.
• Flinn, M. V., Geary, D. C., & Ward, C. V. (2005). Ecological dominance, social competition, and coalitionary
arms races: Why humans evolved extraordinary intelligence. Evolution and Human Behavior, 26, 10-46. Full text.
(http://web.missouri.edu/~gearyd/Flinnetal2005.pdf)PDF (345 KB)
• edited by Steve Jones, Robert Martin, and David Pilbeam ; foreword by Richard Dawkins. (1994). Jones, S.,
Martin, R., & Pilbeam, D.. ed. The Cambridge Encyclopedia of Human Evolution. Cambridge: Cambridge
University Press. ISBN 0-521-32370-3. Also ISBN 0-521-46786-1
Human evolution 315

• Wolfgang Enard et al. (2002-08-22). "Molecular evolution of FOXP2, a gene involved in speech and language".
Nature 418: 870.
• DNA Shows Neandertals Were Not Our Ancestors (http://www.psu.edu/ur/NEWS/news/Neandertal.html)
• J. W. IJdo, A. Baldini, D. C. Ward, S. T. Reeders, R. A. Wells (October 1991). "Origin of human chromosome 2:
An ancestral telomere-telomere fusion" (http://www.pnas.org/cgi/reprint/88/20/9051.pdf) (PDF). Genetics
88: 9051–9055.—two ancestral ape chromosomes fused to give rise to human chromosome 2.
• Ovchinnikov, et al.; Götherström, Anders; Romanova, Galina P.; Kharitonov, Vitaliy M.; Lidén, Kerstin;
Goodwin, William (2000). "Molecular analysis of Neanderthal DNA from the Northern Caucasus". Nature 404
(6777): 490. doi:10.1038/35006625. PMID 10761915.
• Heizmann, Elmar P J, Begun, David R (2001). "The oldest Eurasian hominoid". Journal of Human Evolution 41
(5): 463. doi:10.1006/jhev.2001.0495. PMID 11681862.
• BBC: Finds test human origins theory. (http://news.bbc.co.uk/2/hi/science/nature/6937476.stm)
2007-08-08 Homo habilis and Homo erectus are sister species that overlapped in time.

External links
• BBC: The Evolution of Man (http://www.bbc.co.uk/sn/prehistoric_life/human/human_evolution/index.
shtml)
• Illustrations from Evolution (textbook) (http://www.evolution-textbook.org/content/free/figures/ch25.html)
• Smithsonian – Homosapiens (http://www.mnh.si.edu/anthro/humanorigins/ha/sap.htm)
• Smithsonian – The Human Origins Program (http://www.mnh.si.edu/anthro/humanorigins/faq/encarta/
encarta.htm)
• Becoming Human: Paleoanthropology, Evolution and Human Origins, presented by Arizona State University's
Institute of Human Origins (http://www.becominghuman.org)
Evolutionary psychology 316

Evolutionary psychology
Evolutionary psychology (EP) explains psychological traits—such as memory, perception, or language—as
adaptations, that is, as the functional products of natural selection or sexual selection. Adaptationist thinking about
physiological mechanisms, such as the heart, lungs, and immune system, is common in evolutionary biology.
Evolutionary psychology applies the same thinking to psychology.
Modern evolutionary psychologists argue that much of human behavior is generated by psychological adaptations
that evolved to solve recurrent problems in human ancestral environments.[1] They hypothesize, for example, that
humans have inherited special mental capacities for acquiring language, making it nearly automatic, while inheriting
no capacity specifically for reading and writing.
Other adaptations, according to EP, might include the abilities to infer others' emotions, to discern kin from non-kin,
to identify and prefer healthier mates, to cooperate with others, and so on. Consistent with the theory of natural
selection, evolutionary psychology sees organisms as often in conflict with others of their species, including mates
and relatives. For example, mother mammals and their young offspring sometimes struggle over weaning, which
benefits the mother more than the child. Humans, however, have a marked capacity for cooperation under certain
conditions as well.
Evolutionary psychologists see those behaviors and emotions that are nearly universal, such as fear of spiders and
snakes, as more likely to reflect evolved adaptations. Evolved psychological adaptations (such as the ability to learn
a language) interact with cultural inputs to produce specific behaviors (e.g., the specific language learned). This view
is contrary to the idea that human mental faculties are general-purpose learning mechanisms.

Overview
Evolutionary psychology (EP) is an approach to the entire discipline that views human nature as a universal set of
evolved psychological adaptations to recurring problems in the ancestral environment. Proponents of EP suggest that
it seeks to heal a fundamental division at the very heart of science --- that between the soft human social sciences and
the hard natural sciences, and that the fact that human beings are living organisms demands that psychology be
understood as a branch of biology. Anthropologist John Tooby and psychologist Leda Cosmides note:
"Evolutionary psychology is the long-forestalled scientific attempt to assemble out of the disjointed,
fragmentary, and mutually contradictory human disciplines a single, logically integrated research
framework for the psychological, social, and behavioral sciences—a framework that not only
incorporates the evolutionary sciences on a full and equal basis, but that systematically works out all of
the revisions in existing belief and research practice that such a synthesis requires."[2]
In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the
necessary acquirement of each mental power and capacity by gradation. Light will be thrown on the origin of man and his history.

Charles Darwin, On the Origin of Species

Just as human physiology and evolutionary physiology have worked to identify physical adaptations of the body that
represent "human physiological nature," the purpose of evolutionary psychology is to identify evolved emotional and
cognitive adaptations that represent "human psychological nature." EP is, to quote Steven Pinker, "not a single
theory but a large set of hypotheses" and a term which "has also come to refer to a particular way of applying
evolutionary theory to the mind, with an emphasis on adaptation, gene-level selection, and modularity."
Evolutionary psychology is founded on a computational theory of mind maintaining that our "inner world" is the
result of complex neural structures and interactions in the brain. For example, our brains can perceive a spider,
compute that it is a potential threat, and initiate a fear response.
Evolutionary psychology 317

EP proposes that the human brain comprises many functional mechanisms,[3] called psychological adaptations or
evolved cognitive mechanisms or cognitive modules designed by the process of natural selection. Examples include
language acquisition modules, incest avoidance mechanisms, cheater detection mechanisms, intelligence and
sex-specific mating preferences, foraging mechanisms, alliance-tracking mechanisms, agent detection mechanisms,
and others. EP has roots in cognitive psychology and evolutionary biology (See also sociobiology).
It also draws on behavioral ecology, artificial intelligence, genetics, ethology, anthropology, archaeology, biology,
and zoology. EP is closely linked to sociobiology, but there are key differences between them including the emphasis
on domain-specific rather than domain-general mechanisms, the relevance of measures of current fitness, the
importance of mismatch theory, and psychology rather than behaviour. Most of what is now labeled as
sociobiological research is now conducted in the field of behavioral ecology.
The term evolutionary psychology was probably coined by American biologist Michael Ghiselin in a 1973 article
published in the journal Science.[4] Jerome Barkow, Leda Cosmides and John Tooby popularized the term
"evolutionary psychology" in their highly influential 1992 book The Adapted Mind: Evolutionary Psychology and
The Generation of Culture.[5] EP has been applied to the study of many fields, including economics, aggression, law,
psychiatry, politics, literature, and sex.
EP uses Nikolaas Tinbergen's four categories of questions and explanations of animal behavior. Two categories are
at the species level; two, at the individual level, as noted in the table below.

How vs. Why Questions: Sequential vs. Static Perspective

Historical/ Developmental Current Form

Explanation of current form in terms of a historical Explanation of the current form of species
sequence

Proximate Ontogeny Mechanism

How organisms' structures function Developmental explanations for changes in Mechanistic explanations for how an organism's
individuals, from DNA to their current form structures work

Evolutionary Phylogeny Adaptation

Why organisms evolved the The history of the evolution of sequential changes A species trait that evolved to solve a reproductive or
structures (adaptations) they have in a species over many generations survival problem in the ancestral environment

The species-level categories (often called "ultimate explanations") are

• the function (i.e., adaptation) that a behavior serves and
• the evolutionary process (i.e., phylogeny) that resulted in the adaptation (functionality).
The individual-level categories are
• the development of the individual (i.e., ontogeny) and
• the proximate mechanism (e.g., brain anatomy and hormones).
Evolutionary psychology mostly focuses on the adaptation (functional) category.
Evolutionary psychology 318

Related disciplines
The content of EP has derived from, on the one
hand, the biological sciences (especially
evolutionary theory as it relates to ancient human
environments, the study of paleoanthropology and
animal behavior) and, on the other, the human
sciences especially psychology. Evolutionary
biology as an academic discipline emerged with
the modern evolutionary synthesis in the 1930s
and 1940s,[7] although it was not until the 1970s
and 1980s that university departments included
the term evolutionary biology in their titles.
Several behavioural subjects relate to this core
discipline: in the 1930s the study of animal Nobel Laureates Nikolaas Tinbergen (left) and Konrad Lorenz (right) who
were, with Karl von Frisch, acknowledged for work on animal behavior
behaviour (ethology) emerged with the work of
"The Nobel Prize in Physiology or Medicine 1973". Nobel Foundation. .
Dutch biologist Nikolaas Tinbergen and Austrian Retrieved 2007-07-28.
biologists Konrad Lorenz and Karl von Frisch. In
the 1970s two major branches developed from ethology. Firstly, the study of animal social behavior (including
humans) generated sociobiology, defined by its pre-eminent proponent Edward O. Wilson in 1975 as "the systematic
study of the biological basis of all social behavior"[8] and in 1978 as "the extension of population biology and
evolutionary theory to social organization".[9] Secondly, there was behavioral ecology which placed less emphasis on
social behavior by focusing on the ecological and evolutionary basis of both animal and human behavior.

From psychology there are the primary streams of developmental, social and cognitive psychology. Establishing
some measure of the relative influence of genetics and environment on behavior has been at the core of behavioral
genetics and its variants, notably studies at the molecular level that examine the relationship between genes,
neurotransmitters and behavior. Dual inheritance theory (DIT), developed in the late 1970s and early 1980s, has a
slightly different perspective by trying to explain how human behavior is a product of two different and interacting
evolutionary processes: genetic evolution and cultural evolution. DIT is a "middle-ground" between much of social
science, which views culture as the primary cause of human behavioral variation, and human sociobiology and
evolutionary psychology which view culture as an insignificant by-product of genetic selection.[10]

Principles
Leading practitioners of EP have proposed a foundation of core premises. Those proposed by David Buss state that:
1. Manifest behavior depends on underlying psychological mechanisms, information processing devices housed in
the brain, in conjunction with the external and internal inputs that trigger their activation.
2. Evolution by selection is the only known causal process capable of creating such complex organic mechanisms.
3. Evolved psychological mechanisms are functionally specialized to solve adaptive problems that recurred for
humans over deep evolutionary time.
4. Selection designed the information processing of many evolved psychological mechanisms to be adaptively
influenced by specific classes of information from the environment.
5. Human psychology consists of a large number of functionally specialized evolved mechanisms, each sensitive to
particular forms of contextual input, that get combined, coordinated, and integrated with each other to produce
manifest behavior.
Pioneers of the subject Leda Cosmides and John Tooby consider the following five principles as critical:
Evolutionary psychology 319

1. The brain is a physical system. It functions as a computer with circuits that have evolved to generate behavior
that is appropriate to environmental circumstances
2. Neural circuits were designed by natural selection to solve problems that human ancestors faced while evolving
into Homo sapiens
3. Consciousness is a small portion of the contents and processes of the mind; conscious experience can mislead
individuals to believe their thoughts are simpler than they actually are. Most problems experienced as easy to
solve are very difficult to solve and are driven and supported by very complicated neural circuitry
4. Different neural circuits are specialized for solving different adaptive problems.
5. Modern skulls house a Stone age mind.[11]
These researchers suggest that EP is not simply a subdiscipline of psychology but that evolutionary theory can
provide a foundational, metatheoretical framework that integrates the entire field of psychology, in the same way it
has for biology.[11]

General evolutionary theory

Main article: Evolution
EP is sometimes seen not simply as a subdiscipline of psychology but as a way in which evolutionary theory can be
used as a metatheoretical framework within which to examine the entire field of psychology[11] although a few
biologists challenge its basic premises.[12]

Natural selection
Natural selection, a key component of evolutionary theory,
involves three main ingredients:
• Genetically based inheritance of traits - some traits are
passed down from parents to offspring in genes,
• Variation - heritable traits vary within a population (now
we know that mutation is the source of some of this genetic
variation),
• Differential survival and reproduction - these traits will
vary in how strongly they promote the survival and
reproduction of their bearers.
Selection refers to the process by which environmental
conditions "select" organisms with the appropriate traits to Darwin's illustrations of beak variation in the finches of the
Galápagos Islands.
survive; these organisms will have such traits more strongly
represented in the next generation. This is the basis of
adaptive evolution. The insight of Wallace and Darwin was that this "natural selection" was creative - it could lead to
new traits and even new species, it was based on differential survival of variable individuals, and it could explain the
broad scale patterns of evolution.
Evolutionary psychology 320

Sexual selection
Many traits that are selected for can actually hinder survival of the organism while increasing its reproductive
opportunities. Consider the classic example of the peacock's tail. It is metabolically costly, cumbersome, and
essentially a "predator magnet." What the peacock's tail does do is attract mates. Thus, the type of selective process
that is involved here is what Darwin called "sexual selection". Sexual selection can be divided into two types:
• Intersexual selection, which refers to the traits that one sex generally prefers in the other sex, (e.g. the peacock's
tail).
• Intrasexual competition, which refers to the competition among members of the same sex for mating access to the
opposite sex, (e.g. two stags locking antlers).

Inclusive fitness
Inclusive fitness theory, which was proposed by William D. Hamilton in 1964 as a revision to evolutionary theory, is
essentially a combination of natural selection, sexual selection, and kin selection. It refers to the sum of an
individual's own reproductive success in addition to the effects the individual's actions have on the reproductive
success of their genetic relatives. General evolutionary theory, in its modern form, is essentially inclusive fitness
theory.
Inclusive fitness theory resolved the issue of how "altruism" evolved. The dominant, pre-Hamiltonian view was that
altruism evolved via group selection: the notion that altruism evolved for the benefit of the group. The problem with
this was that if one organism in a group incurred any fitness costs on itself for the benefit of others in the group, (i.e.
acted "altruistically"), then that organism would reduce its own ability to survive and/or reproduce, therefore
reducing its chances of passing on its altruistic traits.
Furthermore, the organism that benefited from that altruistic act and only acted on behalf of its own fitness would
increase its own chance of survival and/or reproduction, thus increasing its chances of passing on its "selfish" traits.
Inclusive fitness resolved "the problem of altruism" by demonstrating that altruism can evolve via kin selection as
expressed in Hamilton's rule:
cost < relatedness × benefit
In other words, altruism can evolve as long as the fitness cost of the altruistic act on the part of the actor is less than
the degree of genetic relatedness of the recipient times the fitness benefit to that recipient. This perspective reflects
what is referred to as the gene-centered view of evolution and demonstrates that group selection is a very weak
selective force. However, in recent years group selection has been making a comeback (albeit a controversial one) as
multilevel selection, which posits that evolution can act not just on the "gene" level but on many levels of functional
organization, including the "group" level.

Foundations
Evolutionary psychology 321

System level and Author Basic ideas Example adaptations

problem

System Level: Charles Darwin Natural Selection (or "survival selection") The bodies and minds Bones, skin, vision, pain
Individual (1859) of organisms are made up of evolved adaptations designed to help perception, etc.
the organism survive in a particular ecology (for example, the fur of
Problem:
polar bears or the anus of an octopus).
How to survive?

System Level: Charles Darwin Sexual selection Organisms can evolve physical and mental traits Peacock's tail, antlers, courtship
Dyad (1859) designed specifically to attract mates (e.g., the Peacock's tail) or to behavior, etc.
compete with members of one's own sex for access to the opposite
Problem:
sex (e.g., antlers).
How to attract a mate
and/or compete with
members of one's own
sex for access to the
opposite sex?

System Level: W.D. Hamilton Inclusive fitness (or a "gene's eye view" of selection, "kin Altruism toward kin, parental
Family & Kin (1964) selection") / The evolution of sexual reproduction Selection investment, the behavior of the
Problem: Gene occurs most robustly at the level of the gene, not the individual, social insects with sterile workers
replication. How to help group, or species. Reproductive success can thus be indirect, via (e.g., ants).
those with whom we shared genes in kin. Being altruistic toward kin can thus have
share genes survive and genetic payoffs. (Also see Gene-centered view of evolution) Also,
reproduce? Hamilton argued that sexual reproduction evolved primarily as a
defense against pathogens (bacteria and viruses) to "shuffle genes"
to create greater diversity, especially immunological variability, in
offspring.

System Level: Robert Trivers Parental Investment Theory / Parent - Offspring Conflict / Sexually dimorphic adaptations
Kin and Family (1972) Reproductive Value The two sexes often have conflicting strategies that result in a "battle of the
Problem: regarding how much to invest in offspring, and how many offspring sexes," parental favoritism,
How are resources best to have. timing of reproduction,
allocated in mating Parents allocate more resources to their offspring with higher parent-offspring conflict, sibling
and/or parenting reproductive value (e.g., "mom always liked you best"). Parents and rivalry, etc.
contexts to maximize offspring may have conflicting interests (e.g., when to wean,
inclusive fitness? allocation of resources among offspring, etc.)

System Level: John von Game Theory / Evolutionary Game Theory Facultative, or
Non-kin small group Neumann and Organisms adapt, or respond, to competitors depending on the frequency-dependent,
Problem: Oskar strategies used by competitors. Strategies are evaluated by the adaptations. Examples: hawks vs.
Morgenstern probable payoffs of alternatives. In a population, this typically doves, cooperate vs. defect, fast
How to succeed in
(1944); results in an "evolutionary stable strategy," or "evolutionary stable vs. coy courtship, etc.
competitive interactions
John Maynard equilibrium" -- strategies that, on average, cannot be bettered by
with non-kin? How to
Smith (1982) alternative strategies.
select the best strategy
given the strategies
being used by
competitors?

System Level: Robert Trivers "Tit for Tat" Reciprocity One can play nice with non-kin if a Cheater detection, emotions of
Non-kin small group (1971) mutually beneficially reciprocal relationship is maintained across revenge and guilt, etc.
Problem: multiple social interactions, and cheating is punished.

How to maintain
mutually beneficial
relationships with
non-kin in repeated
interactions?
Evolutionary psychology 322

System Level: Herbert Gintis Generalized Reciprocity (Also called "strong reciprocity"). One can To in-group members: Capacity
Non-kin, large groups (2000, 2003); play nice with non-kin strangers even in single interactions if social for generalized altruism, acting
governed by rules and and others. rules against cheating are maintained by neutral third parties (e.g., like a "good Samaritan,"
laws other individuals, governments, institutions, etc.), a majority group cognitive concepts of justice,
Problem: members cooperate by generally adhering to social rules, and social ethics and human rights.
interactions create a positive sum game (i.e., a bigger overall "pie" To out-group members:
How to maintain
results from group cooperation).
mutually beneficial Capacity for xenophobia, racism,
relationships with Generalized reciprocity may be a set of adaptations that were warfare, genocide.
strangers with whom designed for small in-group cohesion during times of high
one may interact only inter-tribal warfare with out-groups.
once? Today the capacity to be altruistic to in-group strangers may result
from a serendipitous generalization (or "mismatch") between
ancestral tribal living in small groups and today's large societies
that entail many single interactions with anonymous strangers. (The
dark side of generalized reciprocity may be that these adaptations
may also underlie aggression toward out-groups.)

System Level: Richard Memetic Selection / Memetics Genes are not the only replicators Language, music, evoked culture,
Large groups / culture. Dawkins (1976) subject to evolutionary change. "Memes" (e.g., ideas, rituals, tunes, etc. Some possible by-products,
Problem: cultural fads, etc.) can replicate and spread from brain to brain, and or "exaptations," of language may
How to transfer many of the same evolutionary principles that apply to genes apply include writing, reading,
information across to memes as well. Genes and memes may at times co-evolve mathematics, etc.
distance and time? ("gene-culture co-evolution").

Source:[13]

Middle-level evolutionary theories

Middle-level evolutionary theories are theories that encompass broad domains of functioning. They are compatible
with general evolutionary theory but not derived from it. Furthermore, they are applicable across species. During the
early 1970s, three very important middle-level evolutionary theories were contributed by Robert Trivers[14] [15] [16]
• The theory of parent-offspring conflict rests on the fact that even though a parent and his/her offspring are 50%
genetically related, they are also 50% genetically different. All things being equal, a parent would want to allocate
their resources equally amongst their offspring, while each offspring may want a little more for themselves.
Furthermore, an offspring may want a little more resources from the parent than the parent is willing to give. In
essence, parent-offspring conflict refers to a conflict of adaptive interests between parent and offspring. However,
if all things are not equal, a parent may engage in discriminative investment towards one sex or the other,
depending on the parent's condition.
Additional middle-level evolutionary theories used in EP include:
• The Trivers–Willard hypothesis, which proposes that parents will invest more in the sex that gives them the
greatest reproductive payoff (grandchildren) with increasing or marginal investment. Females are the heavier
parental investors in our species. Because of that, females have a better chance of reproducing at least once in
comparison to males, but males in good condition have a better chance of producing high numbers of offspring
than do females in good condition. Thus, according to the Trivers–Willard hypothesis, parents in good condition
are predicted to favor investment in sons, and parents in poor condition are predicted to favor investment in
daughters.
• r/K selection theory, which, in ecology, relates to the selection of traits in organisms that allow success in
particular environments. r-selected species, (in unstable or unpredictable environments), produce many offspring,
each of which is unlikely to survive to adulthood, while K-selected species, (in stable or predictable
environments), invest more heavily in fewer offspring, each of which has a better chance of surviving to
adulthood.
Evolutionary psychology 323

Evolved psychological mechanisms

At a proximal level, evolutionary psychology is based on the hypothesis that, just like hearts, lungs, livers, kidneys,
and immune systems, cognition has functional structure that has a genetic basis, and therefore has evolved by natural
selection. Like other organs and tissues, this functional structure should be universally shared amongst a species, and
should solve important problems of survival and reproduction. Evolutionary psychologists seek to understand
psychological mechanisms by understanding the survival and reproductive functions they might have served over the
course of evolutionary history.
While philosophers have generally considered human mind to include broad faculties, such as reason and lust,
evolutionary psychologists describe EPMs as narrowly evolved to deal with specific issues, such as catching cheaters
or choosing mates.
Some mechanisms, termed domain-specific, deal with recurrent adaptive problems over the course of human
evolutionary history. Domain-general mechanisms, on the other hand, deal with evolutionary novelty.

Environment of evolutionary adaptedness

EP argues that to properly understand the functions of the brain, one must understand the properties of the
environment in which the brain evolved. That environment is often referred to as the environment of evolutionary
adaptedness, or EEA for short.[17]

Definition
The term environment of evolutionary adaptedness was coined by John Bowlby as part of attachment theory. It
refers to the environment to which a particular evolved mechanism is adapted. More specifically, the EEA is defined
as the set of historically recurring selection pressures that formed a given adaptation, as well as those aspects of the
environment that were necessary for the proper development and functioning of the adaptation. In the environment in
which ducks evolved, for example, attachment of ducklings to their mother had great survival value for the
ducklings. Because the first moving being that a duckling was likely to see was its mother, a psychological
mechanism that evolved to form an attachment to the first moving being would therefore properly function to form
an attachment to the mother. In novel environments, however, the mechanism can malfunction by forming an
attachment to a dog or human instead.

Human EEA
Humans, comprising the genus Homo, appeared between 1.5 and 2.5 million years ago, a time that roughly coincides
with the start of the Pleistocene 1.8 million years ago. Because the Pleistocene ended a mere 12,000 years ago, most
human adaptations either newly evolved during the Pleistocene, or were maintained by stabilizing selection during
the Pleistocene. Evolutionary psychology therefore proposes that the majority of human psychological mechanisms
are adapted to reproductive problems frequently encountered in Pleistocene environments.[18] In broad terms, these
problems include those of growth, development, differentiation, maintenance, mating, parenting, and social
relationships.

Mismatches
Because humans are mostly adapted to Pleistocene environments, psychological mechanisms sometimes exhibit
"mismatches" to the modern environment, similar to the attachment patterns of ducks. One example is the fact that
although about 10,000 people are killed with guns in the US annually,[19] whereas spiders and snakes kill only a
handful, people nonetheless learn to fear spiders and snakes about as easily as they do a pointed gun, and more easily
than an unpointed gun, rabbits or flowers.[20] A potential explanation is that spiders and snakes were a threat to
human ancestors throughout the Pleistocene, whereas guns (and rabbits and flowers) were not. There is thus a
Evolutionary psychology 324

mismatch between our evolved fear-learning psychology and the modern environment.[21] [22] This mismatch also
shows up in the phenomena of the supernormal stimulus-- a stimulus that elicits a response more strongly than the
stimulus for which it evolved. The term was coined by Nobel Laureate Niko Tinbergen to describe animal behavior,
but Harvard psychologist Deirdre Barrett has pointed out that supernormal stimulation governs the behavior of
humans as powerfully as that of animals. In her 2007 book, Waistland[23] she explains junk food as an exaggerated
stimulus to cravings for salt, sugar, and fats, and in her 2010 book, "Supernormal Stimuli: How Primal Urges
Overran Their Evolutionary Purpose,"[24] she describes how television is an exaggeration of social cues of laughter,
smiling faces and attention-grabbing action. Magazine centerfolds and double cheeseburgers pull instincts intended
for an EEA where breast development was a sign of health and fertility in a prospective mate, and fat was a rare and
vital nutrient.[25]

Research methods
Evolutionary psychologists use several methods and data sources to test their hypotheses, as well as various
comparative methods to test for similarities and differences between: humans and other species, males and females,
individuals within a species, and between the same individuals in different contexts. They also use more traditional
experimental methods involving, for example, dependent and independent variables. Recently, methods and tools
have been introduced based on fictional scenarios,[26] mathematical models,[27] and multi-agent computer
simulations.[28]
Evolutionary psychologists also use various sources of data for testing, including archeological records, data from
hunter-gatherer societies, observational studies, self-reports, public records, and human products.[29]

Areas of research
Areas of research in evolutionary psychology can be divided into broad categories of adaptive problems that arise
from the broader theory of evolution itself: survival, mating, parenting, kinship, and group living.

Survival
The Hunting Hypothesis might explain the emergence of human coalitions as a psychological mechanism. With men
being the providers for the family, their lives depended on hunting wild game. They could not risk going about such
an arduous task on their own. If they did it alone they risked not catching anything at all. Also, the meat would spoil
if they caught a large animal and could not finish it on their own. Therefore, they hunted together with other men and
shared their food. These human coalitions can be seen today. One form of evolutionary adaptiveness can be found in
morning sickness in women during their first trimester.Highly acclaimed scientist Luke Gunn describes how 'Over
thousands of years, women's bodies have adapted to the dangers that the environment may pose to the developing
fetus when they eat something. Therefore, during this time many women experience disgust and even vomiting when
eating certain foods which may be toxic to the fetus. Vomiting is the body's way of coping with the toxins in the
environment and keeping them from reaching the child during this critical period when the vital organs are being
formed. The function of this physiological reaction was to protect the fetus.'
Evolutionary psychology 325

Mating
Given that sexual reproduction is the means by which genes are propagated into future generations, sexual selection
plays a large role in the direction of human evolution. Human mating, then, is of interest to evolutionary
psychologists who aim to investigate evolved mechanisms to attract and secure mates.[30] Several lines of research
have stemmed from this interest, such as studies of mate selection[31] [32] [33] mate poaching,[34] and mate
retention,[35] to name a few.
Much of the research on human mating is based on parental investment theory,[36] which makes important
predictions about the different strategies men and women will use in the mating domain (see above under
"Middle-level evolutionary theories"). In essence, it predicts that women will be more selective when choosing
mates, whereas men will not, especially under short-term mating conditions. This has led some researchers to predict
sex differences in such domains as sexual jealousy,[37] [38] (however, see also,)[39] wherein females will react more
aversively to emotional infidelity and males will react more aversively to sexual infidelity. This particular pattern is
predicted because the costs involved in mating for each sex are distinct. Women, on average, should prefer a mate
who can offer some kind of resources (e.g., financial, commitment), which means that a woman would also be more
at risk for losing those valued traits in a mate who commits an emotional infidelity. Men, on the other hand, are
limited by the fact that they can never be certain of the paternity of their children because they do not bear the
offspring themselves. This obstacle entails that sexual infidelity would be more aversive than emotional infidelity for
a man because investing resources in another man's offspring does not lead to propagation of the man's own genes.
Another interesting line of research is that which examines women's mate preferences across the ovulatory cycle.[40]
[41]
The theoretical underpinning of this research is that ancestral women would have evolved mechanisms to select
mates with certain traits depending on their hormonal status. For example, the theory hypothesizes that, during the
ovulatory phase of a woman's cycle (approximately days 10-15 of a woman's cycle),[42] a woman who mated with a
male with high genetic quality would have been more likely, on average, to produce and rear a healthy offspring than
a woman who mated with a male with low genetic quality. These putative preferences are predicted to be especially
apparent for short-term mating domains because a potential male mate would only be offering genes to a potential
offspring. This hypothesis allows researchers to examine whether women select mates who have characteristics that
indicate high genetic quality during the high fertility phase of their ovulatory cycles. Indeed, studies have shown that
women's preferences vary across the ovulatory cycle. In particular, Haselton and Miller (2006) showed that highly
fertile women prefer creative but poor men as short-term mates. Creativity may be a proxy for good genes.[43]
Research by Gangestad et al. (2004) indicates that highly fertile women prefer men who display social presence and
intrasexual competition; these traits may act as cues that would help women predict which men may have, or would
be able to acquire, resources.

Evolutionary Developmental Psychology

In evolutionary theory, what matters most is that individuals live long enough to reproduce and pass on their genes.
So why do humans live so long after reproduction? Many evolutionary psychologists have proposed that living a
long life improves the survival of babies because while the parents were out hunting, the grandparents cared for the
young.
According to Paul Baltes, the benefits granted by evolutionary selection decrease with age. Natural Selection has not
eliminated many harmful conditions and nonadaptive characteristics that appear among older adults, such as
Alzheimer disease. If it were a disease that killed 20 year-olds instead of 70 year-olds this may have been a disease
that natural selection could have destroyed ages ago. Thus, unaided by evolutionary pressures against nonadaptive
conditions, we suffer the aches, pains, and infirmities of aging. And as the benefits of evolutionary selection decrease
with age, the need for culture increases.[44]
Evolutionary psychology 326

History

19th century
After his seminal work in developing theories of natural selection, Charles Darwin devoted much of his final years to
the study of animal emotions and psychology. He wrote two books;The Descent of Man, and Selection in Relation to
Sex in 1871 and The Expression of the Emotions in Man and Animals in 1872 that dealt with topics related to
evolutionary psychology. He introduced the concepts of sexual selection to explain the presence of animal structures
that seemed unrelated to survival, such as the peacock's tail. He also introduced theories concerning group selection
and kin selection to explain altruism. Darwin pondered why humans and animals were often generous to their group
members. Darwin felt that acts of generosity decreased the fitness of generous individuals. This fact contradicted
natural selection which favored the fittest individual. Darwin concluded that while generosity decreased the fitness
of individuals, generosity would increase the fitness of a group. In this case, altruism arose due to competition
between groups.[45] Darwin anticipated evolutionary psychology with this quote from the Origin of Species:
In the distant future I see open fields for far more important researches. Psychology will be based on a new
foundation, that of the necessary acquirement of each mental power and capacity by gradation.
-- Charles Darwin, The Origin of Species, 1859, p. 449.
According to Noam Chomsky, the founder of evolutionary psychology might have been Peter Kropotkin, who
argued in his 1902 book Mutual Aid: A Factor of Evolution for the evolutionary benefits of behavioral traits related
to mutual aid. [46]

Post world war II

While Darwin's theories on natural selection gained acceptance in the early part of the 20th century, his theories on
evolutionary psychology were largely ignored. Only after the second world war, in the 1950s, did interest increase in
the systematic study of animal behavior. It was during this period that the modern field of ethology emerged. Konrad
Lorenz and Nikolaas Tinbergen were pioneers in developing the theoretical framework for ethology for which they
would receive a Nobel prize in 1973.

Sociobiology
In 1975, E O Wilson built upon the works of Lorenz and Tinbergen by combining studies of animal behavior, social
behavior and evolutionary theory in his book Sociobiology:The New Synthesis. Wilson included a chapter on human
behavior. The specific chapter caused considerable controversy as it reignited the nature versus nurture debate.
E O Wilson argues that the field of evolutionary psychology is essentially the same as sociobiology.[47] According to
Wilson, the heated controversies surrounding Sociobiology:The New Synthesis, significantly stigmatized the term
"sociobiology". Evolutionary psychology emerged as a more acceptable term in the 1980s that was not tainted by
earlier controversies, and also emphasized that organisms are "adaptation executors" rather than "fitness maximizers"
(which can help to explain maladaptive behaviors due to "fitness lags" given novel environmental changes). In
addition, rather than focus primarily on overt behavior, EP attempts to identify underlying psychological adaptations
(including emotional, motivational and cognitive mechanisms), and how these mechanisms interact with the
developmental and current environmental influences to produce behavior.[48] [49]
Evolutionary psychology 327

Controversies
Applying evolutionary theory to animal behavior is uncontroversial. However, adaptationist approaches to human
psychology are contentious, with critics questioning the scientific nature of evolutionary psychology, and with more
minor debates within the field itself.[50] [51] Criticisms of the field have also been addressed by scholars.[52]

See also
• Behavioural genetics
• Dual inheritance theory
• Ethnic nepotism
• Evolutionary developmental psychology
• Evolutionary educational psychology
• Evolutionary neuroscience
• Evolutionary Psychology Research Groups and Centers
• Gene-centered view of evolution
• Human behavioral ecology
• List of evolutionary psychologists
• Memetics
• Multiple discovery
• Outline of psychology

Notes
[1] Confer, Easton, Fleischman, Goetz, Lewis, Perilloux & Buss, 2010 (http:/ / homepage. psy. utexas. edu/ homepage/ Group/ BussLAB/
pdffiles/ evolutionary_psychology_AP_2010. pdf); Buss, 2005; Durrant & Ellis, 2003; Pinker, 2002; Tooby & Cosmides, 2005
[2] Tooby & Cosmides 2005, p. 5
[3] evolutionary psychology (http:/ / psychegames. com/ evolutionary-psychology. htm) Psyche Games. Accessed August 22, 2007
[4] Ghiselin MT (1973). "Darwin and Evolutionary Psychology: Darwin initiated a radically new way of studying behavior". Science 179 (4077):
964–968. doi:10.1126/science.179.4077.964. PMID 17842154.
[5] Tooby, John; Barkow, Jerome H.; Cosmides, Leda (1995). The Adapted mind: evolutionary psychology and the generation of culture. Oxford
[Oxfordshire]: Oxford University Press. ISBN 0-19-510107-3.
[6] "The Nobel Prize in Physiology or Medicine 1973" (http:/ / nobelprize. org/ nobel_prizes/ medicine/ laureates/ 1973/ index. html). Nobel
Foundation. . Retrieved 2007-07-28.
[7] Sterelny, Kim. 2009. In Ruse, Michael & Travis, Joseph (eds) Wilson, Edward O. (Foreword) Evolution: The First Four Billion Years.
Harvard University Press, Cambridge, Ma. 978-o674031753. p. 314.
[8] Wilson, Edward O. 1975. The New Synthesis. (http:/ / www. hup. harvard. edu/ catalog/ WILSOR. html''Sociobiology:) Harvard University
Pre ss, Cambridge, Ma. ISBN 0-674-00089-7 p.4.
[9] Wilson, Edward O. 1978. On Human Nature. Harvard University Press, Cambridge, Ma. p. x.
[10] Laland, Kevin N. and Gillian R. Brown. 2002. Sense & Nonsense: Evolutionary Perspectives on Human Behavior. Oxford University Press,
Oxford. pp. 287-319.
[11] Cosmides, L; Tooby J (1997-01-13). "Evolutionary Psychology: A Primer" (http:/ / www. psych. ucsb. edu/ research/ cep/ primer. html).
Center for Evolutionary Psychology. . Retrieved 2008-02-16.
[12] See for example:Gould, Stephen Jay (2002). The Structure of Evolutionary Theory. Harvard University Press. ISBN 0674006135.
[13] Mills, M.E. (2004). Evolution and motivation. Symposium paper presented at the Western Psychological Association Conference, Phoenix,
AZ. April, 2004.
[14] Trivers, Robert L. (March 1971). "The evolution of reciprocal altruism" (http:/ / links. jstor. org/
sici?sici=0033-5770(197103)46:1<35:TEORA>2. 0. CO;2-S). Quarterly Review of Biology 46 (1): 35–57. doi:10.1086/406755. .
[15] Trivers, Robert L. (1972). "Parental investment and sexual selection". In Bernard Campbell. Sexual selection and the descent of man,
1871-1971. Aldine Transaction (Chicago). pp. 136–179. ISBN 0202020053.
[16] Trivers, Robert L. (1974). "Parent-offspring conflict". American Zoologist (The Society for Integrative and Comparative Biology) 14 (1):
249–264. doi:10.1093/icb/14.1.249.
[17] See also "Environment of evolutionary adaptation," a variation of the term used in Economics, e.g., in Rubin, Paul H., 2003, "Folk
economics" Southern Economic Journal, 70:1, July 2003, 157-171.
Evolutionary psychology 328

[18] Symons, Donald (1992). "On the use and misuse of Darwinism in the study of human behavior". The Adapted Mind: Evolutionary
psychology and the generation of culture. Oxford University Press. pp. 137–159. ISBN 0195101073.
[19] CDC pdf (http:/ / www. cdc. gov/ nchs/ data/ nvsr/ nvsr54/ nvsr54_10. pdf)
[20] Ohman, A.; Mineka, S. (2001). "Fears, phobias, and preparedness: Toward an evolved module of fear and fear learning" (http:/ / instruct.
uwo. ca/ psychology/ 371g/ Ohman2001. pdf) (PDF). Psychological Review 108 (3): 483–522. doi:10.1037/0033-295X.108.3.483.
PMID 11488376. . Retrieved 2008-06-16.
[21] Pinker, S. (1999). How the Mind Works. WW Norton & Co. New York. pp. 386–389
[22] Hagen, EH; Hammerstein, P (2006). "Game theory and human evolution: a critique of some recent interpretations of experimental games.".
Theoretical population biology 69 (3): 339–48. doi:10.1016/j.tpb.2005.09.005. PMID 16458945.
[23] Barrett, Deirdre. Waistland: The R/Evolutionary Science Behind Our Weight and Fitness Crisis (2007) NY, NY: W.W. Norton, . See
especially section "Supernormal Stimuli--Why Birds Are Cuckoo" p. 31-51. (http:/ / books. google. com/ books?id=vTsnl4KRLegC&
dq=inauthor:Deirdre+ inauthor:Barrett)
[24] Barrett, Deirdre. SUPERNORMAL STIMULI: How Primal Urges Overran Their Evolutionary Purpose. NY NY: W.W. Norton, 2010 (http:/
/ www. amazon. com/ s/ ref=nb_sb_ss_c_1_9?url=search-alias=stripbooks& field-keywords=supernormal+ stimuli& sprefix=supernorm)
[25] Hagen, E and Hammerstein, P (2006). "Game theory and human evolution: A critique of some recent interpretations of experimental
games". Theoretical Population Biology 69 (3): 339. doi:10.1016/j.tpb.2005.09.005. PMID 16458945
[26] Omar Tonsi Eldakar; David Sloan Wilson, and Rick O'Gorman. (2006). "Emotions and actions associated with altruistic helping and
punishment" (http:/ / www. epjournal. net/ filestore/ ep04274286. pdf) (PDF). Evolutionary Psychology 4: 274–286. . Retrieved 2010-08-15.
[27] Omar Tonsi Eldakar; David Sloan Wilson. (2008). "Selfishness as second-order altruism" (http:/ / www. pnas. org/ content/ 105/ 19/ 6982.
full. pdf+ html) (PDF). Proceedings of the National Academy of Sciences of the USA 105 (19): 6982–6986. doi:10.1073/pnas.0712173105.
PMID 18448681. PMC 2383986. . Retrieved 2010-08-15.
[28] Francisco W.S. Lima; Tarik Hadzibeganovic, and Dietrich Stauffer. (2009). "Evolution of ethnocentrism on undirected and directed
Barabási-Albert networks" (PDF). Physica A: Statistical Mechanics and its Applications 388: 4999–5004. doi:10.1016/j.physa.2009.08.029.
[29] Buss, David (2004). Evolutionary Psychology: The New Science of the Mind. Boston: Pearson Education, Inc. ISBN 978-0205483389.
[30] Wilson, G.D. Love and Instinct. London: Temple Smith, 1981.
[31] Buss, D. M. (1994). The evolution of desire: Strategies of human mating. New York: Basic Books.
[32] Buss, D. M., & Barnes, M. (1986). Preferences in human mate selection. (http:/ / homepage. psy. utexas. edu/ homepage/ Group/ BussLAB/
pdffiles/ prefs_mate_selection_1986_jpsp. pdf) Journal of Personality and Social Psychology, 50, 559-570.
[33] Li, N. P., Bailey, J. M., Kenrick, D. T., & Linsenmeier, J. A. W. (2002). The necessities and luxuries of mate preferences: Testing the
tradeoffs. (http:/ / www. psych. northwestern. edu/ psych/ people/ faculty/ bailey/ Publications/ Li et al. , 2002. pdf) Journal of Personality
and Social Psychology, 6, 947-955.
[34] Schmitt, D. P., & Buss, D. M. (2001). Human mate poaching: Tactics and temptations for infiltrating existing relationships. (http:/ /
homepage. psy. utexas. edu/ homepage/ Group/ BussLAB/ pdffiles/ Human_Mate_Poaching_2001. pdf) Journal of Personality and Social
Psychology, 80, 894-917.
[35] Buss, D. M. (1988). From vigilance to violence: Tactics of mate retention in American undergraduates. (http:/ / homepage. psy. utexas. edu/
homepage/ Group/ BussLAB/ pdffiles/ Vigilance_to_Violence_1988. pdf) Ethology and Sociobiology, 9, 291-317.
[36] Trivers, R. (1972). Parental investment and sexual selection. In B. Campbell (Ed.), Sexual Selection and the Descent of Man. Chicago:
Aldine-Atherton.
[37] Buss, D. M. (1989). Sex differences in human mate preferences: Evolutionary hypotheses tested in 37 cultures. (http:/ / homepage. psy.
utexas. edu/ homepage/ Group/ BussLAB/ pdffiles/ SexDifferencesinHuman. PDF) Behavioral and Brain Sciences, 12, 1-49.
[38] Buss, D. M., Larsen, R. J., Westen, D., & Semmelroth J. (1992). Sex differences in jealousy: Evolution, physiology, and psychology. (http:/
/ homepage. psy. utexas. edu/ homepage/ Group/ BussLAB/ pdffiles/ SexDifferencesinJealousy. PDF) Psychological Science 3(4), 251–255
[39] Harris, C. R. (2002) Sexual and romantic jealousy in heterosexual and homosexual adults. Psychological Science 13(1), 7–12
[40] Haselton, M. G., & Miller, G. F. (2006). Women's fertility across the cycle increases the short-term attractiveness of creative intelligence.
(http:/ / www. sscnet. ucla. edu/ comm/ haselton/ webdocs/ haseltonmiller. pdf) Human Nature, 17(1), 50-73.
[41] Gangestad, S. W., Simpson, J. A., Cousins, A. J., Garver-Apgar, C. E., & Christensen, P. N. (2004). Women's preferences for male
behavioral displays change across the menstrual cycle. (http:/ / faculty. oxy. edu/ clint/ evolution/ articles/ Women’s Preferences for Male
behavioral display change across the menstrual cycle. pdf) Psychological Science, 15(3), 203-207.
[42] Wilcox, A. J., Dunson, D. B., Weinberg, C. R., Trussell, J., & Baird, D. D. (2001). Likelihood of conception with a single act of intercourse:
Providing benchmark rates for assessment of post-coital contraceptives. Contraception, 63, 211-215.
[43] Miller, G. F. (2000b) The mating mind: How sexual choice shaped the evolution of human nature. Anchor Books: New York.
[44] Santrock, W. John (2005). A Topical Approach to Life-Span Development (3rd ed.). New York, NY: McGraw-Hill. pp.62.
[45] Shermer (2004). The Science of Good and Evil (http:/ / books. google. com/ ?id=igN6Q9weoYQC& pg=PA51& lpg=PA51& dq="from+
competition+ between+ groups"). Henry Holt and Co.. ISBN 9780805077698. .
[46] http:/ / www. chomsky. info/ interviews/ 200401--. htm
[47] Wilson, EO (2000). Sociobiology (http:/ / books. google. com/ ?id=whG6wOFN-A0C& q=ISBN+ 0674000897& dq=ISBN+ 0674000897).
Belknap Press of Harvard University Press. ISBN 9780674002357. . "Human sociobiology, now often called evolutionary psychology, has in
the last quarter of a century emerged as its own field of study, drawing on theory and data from both biology and the social sciences."
[48] Controversies in the evolutionary social sciences: a guide for the perplexed (http:/ / instruct. uwo. ca/ psychology/ 371g/ Smith2001. pdf)
Evolutionary psychology 329

[49] Evolutionary Psychology By Lance Workman, Will Reader (http:/ / books. google. com/ books?id=9Ni9ggiew1UC& pg=PA17&
dq=sociobiology+ evolutionary+ psychology+ controversy& ei=XqZRSYmJOIzukgSGm-mwBg#PPA17,M1)
[50] Alcock, John (2001). The Triumph of Sociobiology. Oxford [Oxfordshire]: Oxford University Press. ISBN 0-19-516335-4.
[51] Segerstråle, Ullica Christina Olofsdotter (2000). Defenders of the truth : the battle for science in the sociobiology debate and beyond.
Oxford [Oxfordshire]: Oxford University Press. ISBN 0-19-850505-1.
[52] Tooby, J; Cosmides L (2005). "Conceptual foundations of evolutionary psychology" (http:/ / www. psych. ucsb. edu/ research/ cep/ papers/
bussconceptual05. pdf) (pdf). ; in Buss, David M. (2005). Handbook of evolutionary psychology. Chichester: John Wiley & Sons.
ISBN 0-471-26403-2.

References
• Barkow, Jerome H. (2006). Missing the Revolution: Darwinism for Social Scientists. Oxford University Press,
USA. ISBN 0-19-513002-2.
• Buss, David M. (2004). Evolutionary psychology: the new science of the mind. Boston: Pearson/A and B.
ISBN 0-205-37071-3.
• Clarke, Murray (2004). Reconstructing reason and representation. Cambridge, Mass: MIT Press.
ISBN 0-262-03322-4.
• Joyce, Richard (2006). The Evolution of Morality (Life and Mind: Philosophical Issues in Biology and
Psychology). Cambridge, Mass: The MIT Press. ISBN 0-262-10112-2.
• Miller, Geoffrey P. (2000). The mating mind: how sexual choice shaped the evolution of human nature. Garden
City, N.Y: Doubleday. ISBN 0-385-49516-1.
• Pinker, Steven (1997). How the mind works. New York: Norton. ISBN 0-393-04535-8.
• Pinker, Steven (2002). The blank slate: the modern denial of human nature. New York, N.Y: Viking.
ISBN 0-670-03151-8.
• Richards, Janet C. (2000). Human nature after Darwin: a philosophical introduction. New York: Routledge.
ISBN 0-415-21243-X.
• Wilson, Edward Raymond (2000). Sociobiology: the new synthesis. Cambridge: Belknap Press of Harvard
University Press. ISBN 0-674-00089-7.
• Wright, Robert C. M. (1995). The moral animal: evolutionary psychology and everyday life. New York: Vintage
Books. ISBN 0-679-76399-6.
• Santrock, John W. (2005). The Topical Approach to Life-Span Development(3rd ed.). New York, N.Y: McGraw
Hill. ISBN 0-07-322626-2.

Further reading
• Buss, D. M. (1995). Evolutionary psychology: A new paradigm for psychological science. Psychological Inquiry,
6, 1-30. Full text (http://homepage.psy.utexas.edu/homepage/Group/BussLAB/pdffiles/
ANewParadigmforPsych.PDF)
• Durrant, R., & Ellis, B.J. (2003). Evolutionary Psychology. In M. Gallagher & R.J. Nelson (Eds.), Comprehensive
Handbook of Psychology, Volume Three: Biological Psychology (pp. 1–33). New York: Wiley & Sons. Full text
(http://media.wiley.com/product_data/excerpt/38/04713840/0471384038.pdf#search='evolutionary
psychologypdf')
• Kennair, L. E. O. (2002). "Evolutionary psychology: An emerging integrative perspective within the science and
practice of psychology" (http://www.human-nature.com/nibbs/02/ep.html). Human Nature Review (2):
17–61.
• Medicus, G. (2005). "Evolutionary Theory of Human Sciences" (http://homepage.uibk.ac.at/~c720126/
humanethologie/ws/medicus/block1/inhalt.html). pp. 9, 10, 11. Retrieved 2009-09-08.
• Tooby, J. & Cosmides, L. (2005). Conceptual foundations of evolutionary psychology. In D. M. Buss (Ed.), The
Handbook of Evolutionary Psychology (pp. 5–67). Hoboken, NJ: Wiley. Full text (http://www.psych.ucsb.edu/
research/cep/papers/bussconceptual05.pdf)
Evolutionary psychology 330

• For more readings, see the books (http://hbes.com/Hbes/books_c.htm) page at the Human Behavior and
Evolution Society (http://hbes.com/)

External links
• Evolutionary Psychology page (http://www.scholarpedia.org/article/Evolutionary_psychology) at
Scholarpedia
• Evolutionary Psychology (http://www.dmoz.org/Science/Social_Sciences/Psychology/
Evolutionary_Psychology/) at the Open Directory Project
• Evolutionary Psychology page (http://en.citizendium.org/wiki/Evolutionary_psychology) at Citizendium
• What Is Evolutionary Psychology? by Clinical Evolutionary Psychologist Dale Glaebach (http://www.
systemsthinker.com/interests/mind/glabachep/glabachwhatisep.shtml).
• Evolutionary Psychology-Approaches in Psychology (http://www.psychegames.com/evolutionary-psychology.
htm)

Academic societies
• Human Behavior and Evolution Society (http://www.hbes.com); international society dedicated to using
evolutionary theory to study human nature
• The International Society for Human Ethology (http://evolution.anthro.univie.ac.at/ishe); promotes
ethological perspectives on the study of humans worldwide
• The Association for Politics and the Life Sciences (http://www.aplsnet.org/); international and interdisciplinary
association concerned with evolutionary, genetic and ecological knowledge
• Society for Evolutionary Analysis in Law (http://www.sealsite.org/)
• The New England Institute for Cognitive Science and Evolutionary Psychology (http://www.une.edu/nei/)
• The NorthEastern Evolutionary Psychology Society (http://www.neepsociety.com/); regional society dedicated
to encouraging scholarship and dialogue on the topic of evolutionary psychology

Journals
• Evolutionary Psychology (http://www.epjournal.net/) free access online scientific journal
• Evolution and Human Behavior (http://www.sciencedirect.com/science/journal/10905138); journal of the
Human Behavior and Evolution Society (http://www.hbes.com)
• Politics and the Life Sciences (http://www.politicsandthelifesciences.org/) is an interdisciplinary
peer-reviewed journal published by the Assoication for Politics and the Life Sciences (http://www.aplsnet.org/
)
• Human Nature: An Interdisciplinary Biosocial Perspective (http://www.springer.com/social+sciences/
anthropology+and+archaeology/journal/12110) advances the interdisciplinary investigation of the biological,
social, and environmental factors that underlie human behavior. It focuses primarily on the functional unity in
which these factors are continuously and mutually interactive. These include the evolutionary, biological, and
sociological processes as they interact with human social behavior.
• Biological Theory: Integrating Development, Evolution and Cognition (http://www.kli.ac.at/publications-a.
html) devoted to theoretical advances in the fields of biology and cognition, with an emphasis on the conceptual
integration afforded by evolutionary and developmental approaches.
• Evolutionary Anthropology (http://www3.interscience.wiley.com/cgi-bin/jtoc?ID=38641)
• Behavioral and Brain Sciences (http://www.bbsonline.org/) interdisciplinary articles in psychology,
neuroscience, behavioral biology, cognitive science, artificial intelligence, linguistics and philosophy. About 30%
of the articles have focused on evolutionary analyses of behavior.
Evolutionary psychology 331

• Evolution and Development (http://www3.interscience.wiley.com/journal/118546131/home) Research

relevant to interface of evolutionary and developmental biology
• Journal of Social, Evolutionary & Cultural Psychology (http://www.jsecjournal.com/)
• Biological Theory: Integrating Development, Evolution and Cognition (http://www.kli.ac.at/publications-a.
html); publishes theoretical advances in the fields of biology and cognition, emphasizing the conceptual
integration afforded by evolutionary and developmental approaches. Free access to Winter 2006 issues (http://
www.mitpressjournals.org/toc/biot/1/1)

Videos
• Brief video clip re what EP is (from the "Evolution" PBS Series) (http://www.youtube.com/
watch?v=pEmX8Rim-hs)
• TED talk (http://www.ted.com/index.php/talks/steven_pinker_chalks_it_up_to_the_blank_slate.html) by
Steven Pinker about his book The Blank Slate: The Modern Denial of Human Nature
• Margaret Mead and Samoa; (http://video.google.com/videoplay?docid=-3157675332479529894&
q=margaret+mead+and+samoa&total=11&start=0&num=10&so=0&type=search&plindex=0) review of the
nature vs. nurture debate triggered by Coming of Age in Samoa
• Video interview (http://video.google.com/videoplay?docid=3554279466299738997) with Steven Pinker by
Robert Wright (journalist) discussing evolutionary psychology
• Video interview (http://video.google.com/videoplay?docid=-4975549474851602314) with Edward O. Wilson
by Robert Wright (journalist), contextualizing evolutionary psychology within science, politics, academics and
philosophy
 332

Controversy and social impacts

Creation–evolution controversy
The creation–evolution controversy (also termed the creation vs. evolution debate or the origins debate) is a
recurring cultural, political, and theological dispute about the origins of the Earth, humanity, life, and the universe.[1]
The dispute is between those who espouse religious belief and thus support a creationist view, versus those who
accept evolution, as supported by scientific consensus. The dispute particularly involves the field of evolutionary
biology, but also the fields of geology, palaeontology, thermodynamics, nuclear physics and cosmology.[2] Though
also present in Europe and elsewhere,[3] and often portrayed as part of the culture wars,[4] this debate is most
prevalent in the United States. While the controversy has a long history,[5] today it is mainly over what constitutes
good science,[6] with the politics of creationism primarily focusing on the teaching of creation and evolution in
public education.[7]
The debate also focuses on issues such as the definition of science (and of what constitutes scientific research and
evidence), science education (and whether the teaching of the scientific consensus view should be 'balanced' by also
teaching fringe theories), free speech, separation of Church and State, and theology (particularly how different
Christians and Christian denominations interpret the Book of Genesis).
Within the scientific community and academia the level of support for evolution is essentially universal,[8] while
support for biblically-literal accounts or other creationist alternatives is very small among scientists, and virtually
nonexistent among those in the relevant fields.[9]
The debate is sometimes portrayed as being between science and religion. However, as the National Academy of
Sciences states:
Today, many religious denominations accept that biological evolution has produced the diversity of living
things over billions of years of Earth’s history. Many have issued statements observing that evolution and the
tenets of their faiths are compatible. Scientists and theologians have written eloquently about their awe and
wonder at the history of the universe and of life on this planet, explaining that they see no conflict between
their faith in God and the evidence for evolution. Religious denominations that do not accept the occurrence of
evolution tend to be those that believe in strictly literal interpretations of religious texts.
—National Academy of Sciences, Science, Evolution, and Creationism[10]

History of the controversy

The creation-evolution controversy originated from Europe and North America in the late 18th century when
discoveries in geology led to various theories of an ancient earth, and fossils showing past extinctions prompted
early ideas of evolution, notably Lamarckism. In England these ideas of continuing change were seen as a threat to
the fixed social order, and were harshly repressed.[11] Conditions eased, and in 1844 the controversial Vestiges
popularised transmutation of species. The scientific establishment dismissed it scornfully and the Church of England
reacted with fury, but many Unitarians, Quakers and Baptists opposed to the privileges of the Established church
favoured its ideas of God acting through laws.[12]
Creation–evolution controversy 333

Controversies in the age of Darwin

Publication of Charles Darwin's On the Origin of Species by Means of
Natural Selection in 1859 brought scientific credibility to evolution,
and made it a respectable field of study.[13]
There was intense interest in the religious implications of Darwin's
book, but the Church of England's attention was largely diverted by
theological controversy over higher criticism set out in Essays and
Reviews by liberal Christian authors, some of whom expressed support
for Darwin, as did many nonconformists. The Reverend Charles
Kingsley openly supported the idea of God working through evolution.
However, many Christians were opposed to the idea and even some of
Darwin's close friends and supporters including Charles Lyell and Asa
Gray could not accept some of his ideas.[14] Thomas Huxley, who
strongly promoted Darwin's ideas while campaigning to end the
dominance of science by the clergy, coined the term agnostic to
describe his position that God’s existence is unknowable, and Darwin
also took this position,[14] but evolution was also taken up by A satirical 1871 image of Charles Darwin as an
ape reflects part of the social controversy over
prominent atheists including Edward Aveling and Ludwig Büchner and whether humans and apes share a common
criticised, in the words of one reviewer, as "tantamount to atheism."[15] lineage.
Following the lead of figures such as St. George Jackson Mivart and
John Zahm Catholics in the United States were accepting of evolution itself while ambivalent towards natural
selection and stressing humanity's divinely imbued soul.[16] Though evolution was never condemned by the church,
initially the more conservative leaning Catholic leadership in Rome held back but gradually adopted a similar
position.[16] [17]

Creationists during this period were largely premillennialists, whose belief in Christ's return depended on a
quasi-literal reading of the Bible.[18] However, they were not as concerned about geology, freely granting scientists
any time they needed before the Garden of Eden to account for scientific observations, such as fossils and geological
findings.[19] In the immediate post-Darwinian era, few scientists or clerics rejected the antiquity of the earth or the
progressive nature of the fossil record.[20] Likewise, few attached geological significance to the Biblical flood, unlike
subsequent creationists.[20] Evolutionary skeptics, creationist leaders and skeptical scientists were usually willing
either to adopt a figurative reading of the first chapter of Genesis, or to allow that the six days of creation were not
necessarily 24-hour days.[21]

Creationism
During the 19th century and up until the mid-20th century, Creationism was widely accepted and was considered a
foundational truth, but there was no official resistance to evolution by mainline denominations within the United
States of America.[14] Around the start of the 20th century some evangelical scholars had ideas accommodating
evolution, such as B. B. Warfield who saw it as a natural law expressing God’s will. However, development of the
eugenics movement led many Catholics to reject evolution.[14] In this enterprise they received little aid from
conservative Christians in Britain and Europe. In Britain this has been attributed to their minority status leading to a
more tolerant, less militant theological tradition. The main British Creationist movement in this period was the
Evolution Protest Movement, formed in the 1930s.[22]
Creation–evolution controversy 334

The Butler Act and the Scopes monkey trial

In the aftermath of World War I, the Fundamentalist-Modernist

Controversy brought a surge of opposition to the idea of evolution,
and following the campaigning of William Jennings Bryan several
states introduced legislation prohibiting the teaching of evolution.
By 1925, such legislation was being considered in 15 states, and
passed in some states, such as Tennessee.[23] The American Civil
Liberties Union offered to defend anyone who wanted to bring a
test case against one of these laws. John T. Scopes accepted, and
he confessed to teaching his Tennessee class evolution in defiance
of the Butler Act. The textbook in question was Hunter's Civic
Biology (1914). The trial was widely publicized by H. L. Mencken Clarence Darrow and William Jennings Bryan chat in
among others, and is commonly referred to as the Scopes Monkey court during the Scopes trial.

Trial. Scopes was convicted; however, the widespread publicity

galvanized proponents of evolution. When the case was appealed to the Tennessee Supreme Court, the Court
overturned the decision on a technicality (the judge had assessed the minimum $100 fine instead of allowing the jury
to assess the fine).[24] [25]

Although it overturned the conviction, the Court decided that the law was not in violation of the Religious Preference
provisions of the Tennessee Constitution (section 3 of article 1), which stated that "that no preference shall ever be
given, by law, to any religious establishment or mode of worship."[26] The Court, applying that state Constitutional
language, held
We are not able to see how the prohibition of teaching the theory that man has descended from a lower order
of animals gives preference to any religious establishment or mode of worship. So far as we know, there is no
religious establishment or organized body that has in its creed or confession of faith any article denying or
affirming such a theory....Protestants, Catholics, and Jews are divided among themselves in their beliefs, and
that there is no unanimity among the members of any religious establishment as to this subject. Belief or
unbelief in the theory of evolution is no more a characteristic of any religious establishment or mode of
worship than is belief or unbelief in the wisdom of the prohibition laws. It would appear that members of the
same churches quite generally disagree as to these things.
...Furthermore, [the Butler Act] requires the teaching of nothing. It only forbids the teaching of evolution of
man from a lower order of animals....As the law thus stands, while the theory of evolution of man may not be
taught in the schools of the State, nothing contrary to that theory [such as Creationism] is required to be taught.
...It is not necessary now to determine the exact scope of the Religious Preference clause of the Constitution ...
Section 3 of article 1 is binding alike on the Legislature and the school authorities. So far we are clear that the
Legislature has not crossed these constitutional limitations.
—Scopes v. State, 289 S.W. 363, 367 (Tenn. 1927).[27]
The interpretation of the Establishment clause up to that time was that the government could not establish a
particular religion as the State religion. The Tennessee Supreme Court's decision held in effect that the Butler Act
was constitutional under the state Constitution's Religious Preference Clause, because the Act did not establish one
religion as the "State religion."[28] As a result of the holding, the teaching of evolution remained illegal in Tennessee,
and continued campaigning succeeded in removing evolution from school textbooks throughout the United
States.[29] [30]
Creation–evolution controversy 335

Epperson v. Arkansas
In 1968, the United States Supreme Court invalidated a forty year old Arkansas statute that prohibited the teaching of
evolution in the public schools. A Little Rock high school biology teacher, Susan Epperson, filed suit charging the
law violated the federal constitutional prohibition against establishment of religion as set forth in the Establishment
Clause. The Little Rock Ministerial Association supported Epperson's challenge, declaring, "to use the Bible to
support an irrational and an archaic concept of static and undeveloping creation is not only to misunderstand the
meaning of the Book of Genesis, but to do God and religion a disservice by making both enemies of scientific
advancement and academic freedom."[31] The Court held that the United States Constitution prohibits a state from
requiring, in the words of the majority opinion, "that teaching and learning must be tailored to the principles or
prohibitions of any religious sect or dogma."[32] But the Supreme Court decision also suggested that creationism
could be taught in addition to evolution.[33]

Daniel v. Waters
Daniel v. Waters was a 1975 legal case in which the United States Court of Appeals for the Sixth Circuit struck
down Tennessee's law regarding the teaching of "equal time" of evolution and creationism in public school science
classes because it violated the Establishment clause of the US Constitution. Following this ruling, creationism was
stripped of overt biblical references and renamed creation science, and several states passed legislative acts requiring
that this be given equal time with the teaching of evolution.

Creation Science
As biologists grew more and more confident in evolution as the central defining principle of biology,[34] American
membership in churches favoring increasingly literal interpretations of scripture rose, with the Southern Baptist
Convention and Lutheran Church - Missouri Synod outpacing all other denominations.[35] With growth, these
churches became better equipped to promulgate a creationist message, with their own colleges, schools, publishing
houses, and broadcast media.[36]
In 1961, the first major modern creationist book was published: Henry M. Morris and John C. Whitcomb Jr.'s The
Genesis Flood. Morris and Whitcomb argued that creation was literally 6 days long, that humans lived concurrently
with dinosaurs, and that God created each 'kind' of life individually.[37] On the strength of this, Morris became a
popular speaker, spreading anti-evolutionary ideas at fundamentalist churches, colleges, and conferences.[38] Morris'
Creation Science Research Center (CSRC) rushed publication of biology text books that promoted creationism, and
also published other books such as Kelly Segrave's sensational Sons of God Return that dealt with UFOlogy, flood
geology, and demonology against Morris' objections.[39] Ultimately, the CSRC broke up over a divide between
sensationalism and a more intellectual approach, and Morris founded the Institute for Creation Research, which was
promised to be controlled and operated by scientists.[40] During this time, Morris and others who supported flood
geology adopted the terms scientific creationism and creation science.[41] The flood geologists effectively co-opted
"the generic creationist label for their hyperliteralist views".[42]
Creation–evolution controversy 336

Court cases

McLean v. Arkansas
In 1982 another case in Arkansas ruled that the Arkansas "Balanced Treatment for Creation-Science and
Evolution-Science Act" was unconstitutional because it violated the establishment clause of the U.S. Constitution.
Much of the transcript of the case was lost, including evidence from Francisco Ayala.

Edwards v. Aguillard
In the early 1980s, the Louisiana legislature passed a law titled the "Balanced Treatment for Creation-Science and
Evolution-Science in Public School Instruction Act". The act did not require teaching either evolution or creationism
as such, but did require that when evolutionary science was taught, creation science had to be taught as well.
Creationists had lobbied aggressively for the law, arguing that the act was about academic freedom for teachers, an
argument adopted by the state in support of the act. Lower courts ruled that the State's actual purpose was to promote
the religious doctrine of creation science, but the State appealed to the Supreme Court.
In the similar case of McLean v. Arkansas (see above) the federal trial court had also decided against creationism.
Mclean v. Arkansas however was not appealed to the federal Circuit Court of Appeals, creationists instead thinking
that they had better chances with Edwards v. Aguillard. In 1987 the Supreme Court of the United States ruled that
the Louisiana act was unconstitutional, because the law was specifically intended to advance a particular religion. At
the same time, however, it stated in its opinion that "teaching a variety of scientific theories about the origins of
humankind to school children might be validly done with the clear secular intent of enhancing the effectiveness of
science instruction," leaving open the door for a handful of proponents of creation science to evolve their arguments
into the iteration of creationism that came to be known as intelligent design.[43]

Intelligent Design
In response to Edwards v. Aguillard, the Neo-Creationist intelligent
design movement was formed around the Discovery Institute's Center
for Science and Culture. Its goal is to restate creationism in terms more
likely to be well received by the public, policy makers, educators, and
the scientific community, and makes the claim that "certain features of
the universe and of living things are best explained by an intelligent
cause, not an undirected process such as natural selection."[45] It has The Discovery Institute's Center for the Renewal
been viewed as a "scientific" approach to creationism by creationists, of Science and Culture used banners based on
"The Creation of Adam" from the Sistine Chapel.
but is widely rejected as unscientific by the science community —
Later it used a less religious image, then was
primarily because intelligent design cannot be tested and rejected like [44]
renamed the Center for Science and Culture.
scientific hypotheses (see for example, list of scientific societies
rejecting intelligent design).

Controversy in recent times

The controversy continues to this day, with the mainstream scientific consensus on the origins and evolution of life
challenged by creationist organizations and religious groups who desire to uphold some form of creationism (usually
young earth creationism, creation science, old earth creationism or intelligent design) as an alternative. Most of these
groups are explicitly Christian, and more than one sees the debate as part of the Christian mandate to evangelize.[46]
Some see science and religion as being diametrically opposed views which cannot be reconciled. More
accommodating viewpoints, held by many mainstream churches and many scientists, consider science and religion to

be separate categories of thought, which ask fundamentally different questions about reality and posit different
avenues for investigating it.[47] Public opinion in regards to the concepts of evolution, creationism, and intelligent
Creation–evolution controversy 337

design is fluctuating.
More recently, the Intelligent Design movement has taken an anti-evolution position which avoids any direct appeal
to religion. Scientists argue that Intelligent design does not represent any research program within the mainstream
scientific community, and is essentially creationism.[48] Its leading proponent, the Discovery Institute, made widely
publicised claims that it was a new science, though the only paper arguing for it published in a scientific journal was
accepted in questionable circumstances and quickly disavowed in the Sternberg peer review controversy, with the
Biological Society of Washington stating that it did not meet the journal's scientific standards, was a "significant
departure" from the journal's normal subject area and was published at the former editor's sole discretion, "contrary
to typical editorial practices".[49] President Bush commented endorsing the teaching of Intelligent design alongside
evolution "I felt like both sides ought to be properly taught ... so people can understand what the debate is about."[50]

Kansas evolution hearings

In the push by intelligent design advocates to introduce intelligent design in public school science classrooms, the
hub of the intelligent design movement, the Discovery Institute, arranged to conduct hearings to review the evidence
for evolution in the light of its Critical Analysis of Evolution lesson plans. The Kansas Evolution Hearings were a
series of hearings held in Topeka, Kansas 5 May to 12 May 2005. The Kansas State Board of Education eventually
adopted the institute's Critical Analysis of Evolution lesson plans over objections of the State Board Science Hearing
Committee, and electioneering on behalf of conservative Republican candidates for the Board.[51] On 1 August 2006,
4 of the 6 conservative Republicans who approved the Critical Analysis of Evolution classroom standards lost their
seats in a primary election. The moderate Republican and Democrats gaining seats vowed to overturn the 2005
school science standards and adopt those recommended by a State Board Science Hearing Committee that were
rejected by the previous board,[52] and on 13 February 2007, the Board voted 6 to 4 to reject the amended science
standards enacted in 2005. The definition of science was once again limited to "the search for natural explanations
for what is observed in the universe."[53]

The Dover Trial

Following the Edwards v. Aguillard decision by the Supreme Court of the United States, in which the Court held that
a Louisiana law requiring that creation science be taught in public schools whenever evolution was taught was
unconstitutional, because the law was specifically intended to advance a particular religion, creationists renewed
their efforts to introduce creationism into public school science classes. This effort resulted in intelligent design,
which sought to avoid legal prohibitions by leaving the source of creation to an unnamed and undefined intelligent
designer, as opposed to God.[54] This ultimately resulted in the "Dover Trial," Kitzmiller v. Dover Area School
District, which went to trial on 26 September 2005 and was decided on 20 December 2005 in favor of the plaintiffs,
who charged that a mandate that intelligent design be taught in public school science classrooms was an
unconstitutional establishment of religion. The Kitzmiller v. Dover decision held that intelligent design was not a
subject of legitimate scientific research, and that it "cannot uncouple itself from its creationist, and hence religious,
antecedents".[55]

Viewpoints

Young Earth creationism

Young Earth creationism is the belief that the Earth was created by God within the last 10,000 years, literally as
described in Genesis, within the approximate timeframe of biblical genealogies (detailed for example in the Ussher
chronology). Young Earth creationists often believe that the Universe has a similar age to the Earth's. Creationist
cosmologies are attempts by some creationist thinkers to give the universe an age consistent with the Ussher
chronology and other Young-Earth timeframes. This belief generally has a basis in a literal and inerrant
interpretation of the Bible.
Creation–evolution controversy 338

Old Earth creationism

Old Earth creationism holds that the physical universe was created by God, but that the creation event of Genesis is
not to be taken strictly literally. This group generally believes that the age of the Universe and the age of the Earth
are as described by astronomers and geologists, but that details of the evolutionary theory are questionable. Old
Earth creationists interpret the Genesis creation narrative in a number of ways, that each differ from the six,
consecutive, 24-hour day creation of the Young Earth Creationist view.

Neo-Creationism
Neo-Creationists intentionally distance themselves from other forms of creationism, preferring to be known as
wholly separate from creationism as a philosophy. Their goal is to restate creationism in terms more likely to be well
received by the public, education policy makers and the scientific community. It aims to re-frame the debate over the
origins of life in non-religious terms and without appeals to scripture, and to bring the debate before the public.
Neo-creationists may be either Young Earth or Old Earth Creationists, and hold a range of underlying theological
viewpoints (e.g. on the interpretation of the Bible). Neo-Creationism currently exists in the form of the intelligent
design movement, which has a 'big tent' strategy making it inclusive of many Young Earth Creationists (such as Paul
Nelson and Percival Davis).

Theistic evolution
Theistic evolution is the general view that, instead of faith being in opposition to biological evolution, some or all
classical religious teachings about God and creation are compatible with some or all of modern scientific theory,
including, specifically, evolution. It generally views evolution as a tool used by a creator god, who is both the first
cause and immanent sustainer/upholder of the universe; it is therefore well accepted by people of strong theistic (as
opposed to deistic) convictions. Theistic evolution can synthesize with the day-age interpretation of the Genesis
creation myth; however most adherents consider that the first chapters of Genesis should not be interpreted as a
"literal" description, but rather as a literary framework or allegory.
This position does not generally exclude the viewpoint of methodological naturalism, a long standing convention of
the scientific method in science.
Theistic evolutionists have frequently been prominent in opposing creationism (including intelligent design). Notable
examples have been biologist Kenneth R. Miller and theologian John Haught, who testified for the plaintiffs in
Kitzmiller v. Dover Area School District. Another example is the Clergy Letter Project, an organization that has
created and maintains a statement signed by American Christian clergy of different denominations rejecting
creationism, with specific reference to points raised by intelligent design proponents. Theistic evolutionists have also
been active in Citizens Alliances for Science that oppose the introduction of creationism into public school science
classes (one example being evangelical Christian geologist Keith B. Miller, who is a prominent board member of
Kansas Citizens for Science).
Creation–evolution controversy 339

Naturalistic evolution
Naturalistic evolution is the position of acceptance of biological evolution and of metaphysical naturalism (and thus
rejection of theism and theistic evolution). A prominent proponent of this viewpoint is British evolutionary biologist
Richard Dawkins.

Arguments relating to the definition and limits of science

Critiques such as those based on the distinction between theory and fact are often leveled against unifying concepts
within scientific disciplines. Principles such as uniformitarianism, Occam's Razor or parsimony, and the Copernican
principle are claimed to be the result of a bias within science toward philosophical naturalism, which is equated by
many creationists with atheism.[56] In countering this claim, philosophers of science use the term methodological
naturalism to refer to the long standing convention in science of the scientific method. The methodological
assumption is that observable events in nature are explained only by natural causes, without assuming the existence
or non-existence of the supernatural, and therefore supernatural explanations for such events are outside the realm of
science.[57] Creationists claim that supernatural explanations should not be excluded and that scientific work is
paradigmatically close-minded.[58]
Because modern science tries to rely on the minimization of a priori assumptions, error, and subjectivity, as well as
on avoidance of Baconian idols, it remains neutral on subjective subjects such as religion or morality.[59] Mainstream
proponents accuse the creationists of conflating the two in a form of pseudoscience.[60]

Definitions
Fact: In science, an observation that has been repeatedly confirmed and for all practical purposes is accepted
as "true." Truth in science, however, is never final, and what is accepted as a fact today may be modified or
even discarded tomorrow.
Hypothesis: A tentative statement about the natural world leading to deductions that can be tested. If the
deductions are verified, it becomes more probable that the hypothesis is correct. If the deductions are incorrect,
the original hypothesis can be abandoned or modified. Hypotheses can be used to build more complex
inferences and explanations.
Law: A descriptive generalization about how some aspect of the natural world behaves under stated
circumstances.
Theory: In science, a well-substantiated explanation of some aspect of the natural world that can incorporate
facts, laws, inferences, and tested hypotheses.
—National Academy of Sciences, Science and Creationism[61]

Limitations of the scientific endeavor

In science, explanations are limited to those based on observations and experiments that can be substantiated
by other scientists. Explanations that cannot be based on empirical evidence are not a part of science.
—National Academy of Sciences, Science and Creationism[61]

Theory vs. fact

The argument that evolution is a theory, not a fact, has often been made against the exclusive teaching of
evolution.[62] The argument is related to a common misconception about the technical meaning of "theory" that is
used by scientists. In common usage, "theory" often refers to conjectures, hypotheses, and unproven assumptions.
However, in science, "theory" usually means "a plausible or scientifically acceptable general principle or body of
principles offered to explain phenomena."[63]
Creation–evolution controversy 340

Exploring this issue, paleontologist Stephen Jay Gould wrote:

Evolution is a theory. It is also a fact. And facts and theories are different things, not rungs in a hierarchy of
increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts.
Facts do not go away when scientists debate rival theories to explain them. Einstein's theory of gravitation
replaced Newton's, but apples did not suspend themselves in mid-air, pending the outcome. And humans
evolved from ape-like ancestors whether they did so by Darwin's proposed mechanism or by some other yet to
be discovered.
—Stephen Jay Gould, Evolution as Fact and Theory[64]

Falsifiability
Philosopher of science Karl R. Popper set out the concept of falsifiability as a way to distinguish science and
pseudoscience: Testable theories are scientific, but those that are untestable are not.[65] However, in Unended Quest,
Popper declared "I have come to the conclusion that Darwinism is not a testable scientific theory but a metaphysical
research programme, a possible framework for testable scientific theories," while pointing out it had "scientific
character".[66]
In what one sociologist derisively called "Popper-chopping,"[67] opponents of evolution seized upon Popper's
definition to claim evolution was not a science, and claimed creationism was an equally valid metaphysical research
program.[68] For example, Duane Gish, a leading Creationist proponent, wrote in a letter to Discover magazine (July
1981): "Stephen Jay Gould states that creationists claim creation is a scientific theory. While many Creationists
claim creation is a scientific theory other Creationists have stated that neither creation nor evolution is a scientific
theory (and each is equally religious)."[69]
Popper responded to news that his conclusions were being used by anti-evolutionary forces by affirming that
evolutionary theories regarding the origins of life on earth were scientific because "their hypotheses can in many
cases be tested."[70] However, creationists claimed that a key evolutionary concept, that all life on Earth is descended
from a single common ancestor, was not mentioned as testable by Popper, and claimed it never would be.[71]
In fact, Popper wrote admiringly of the value of Darwin's theory.[72] Only a few years later, Popper wrote, "I have in
the past described the theory as "almost tautological"...I still believe that natural selection works in this way as a
research programme. Nevertheless, I have changed my mind about the testability and logical status of the theory of
natural selection; and I am glad to have an opportunity to make a recantation". His conclusion, later in the article is
"The theory of natural selection may be so formulated that it is far from tautological. In this case it is not only
testable, but it turns out to be not strictly universally true."[73]
Debate among some scientists and philosophers of science on the applicability of falsifiability in science
continues.[74] However, simple falsifiability tests for common descent have been offered by some scientists: For
instance, biologist and prominent critic of creationism Richard Dawkins and J.B.S. Haldane both pointed out that if
fossil rabbits were found in the Precambrian era, a time before most similarly complex lifeforms had evolved, "that
would completely blow evolution out of the water."[75] [76]
Falsifiability has also caused problems for creationists: In his 1982 decision McLean v. Arkansas Board of
Education, Judge William R. Overton used falsifiability as one basis for his ruling against the teaching of creation
science in the public schools, ultimately declaring it "simply not science."[77]
Creation–evolution controversy 341

Conflation of science and religion

Appeal to consequences
A number of creationists have blurred the boundaries between their disputes over the truth of the underlying facts,
and explanatory theories, of evolution, with their purported philosophical and moral consequences. This type of
argument is known as an appeal to consequences, and is a logical fallacy. Examples of these arguments include those
of prominent creationists such as Ken Ham[78] and Henry M. Morris.[79]

Disputes relating to science

Many creationists strongly oppose certain scientific theories in a number of ways, including opposition to specific
applications of scientific processes, accusations of bias within the scientific community,[80] and claims that
discussions within the scientific community reveal or imply a crisis. In response to perceived crises in modern
science, creationists claim to have an alternative, typically based on faith, creation science, and/or intelligent design.
The scientific community has responded by pointing out that their conversations are frequently misrepresented (e.g.
by quote mining) in order to create the impression of a deeper controversy or crisis, and that the creationists'
alternatives are generally pseudoscientific.

Biology
Disputes relating to evolutionary
biology are central to the controversy
between Creationists and the scientific
community. The aspects of
evolutionary biology disputed include
common descent (and particularly
human evolution from common
ancestors with other members of the
Great Apes), macroevolution, and the
existence of transitional fossils.

Common descent

[The] Discovery [Institute]

presents common descent as A phylogenetic tree based on rRNA genes.
controversial exclusively within
the animal kingdom, as it focuses on embryology, anatomy, and the fossil record to raise questions about them.
In the real world of science, common descent of animals is completely noncontroversial; any controversy
resides in the microbial world. There, researchers argued over a variety of topics, starting with the very
beginning, namely the relationship among the three main branches of life.
—John Timmer, Evolution: what's the real controversy?[81]
A group of organisms is said to have common descent if they have a common ancestor. A theory of universal
common descent based on evolutionary principles was proposed by Charles Darwin and is now generally accepted
by biologists. The last universal common ancestor, that is, the most recent common ancestor of all currently living
organisms, is believed to have appeared about 3.9 billion years ago.
With a few exceptions (e.g. Michael Behe), the vast majority of Creationists reject this theory.[82] [83] [84]
Evidence of common descent includes evidence from genetics, fossil records, comparative anatomy, geographical
distribution of species, comparative physiology and comparative biochemistry.
Creation–evolution controversy 342

Human evolution
Human evolution is the study of the biological evolution of humans as a distinct species from its common ancestors
with other animals. Analysis of fossil evidence and genetic distance are two of the means by which scientists
understand this evolutionary history.
Fossil evidence suggests that humans' earliest hominoid ancestors may have split from other primates as early as the
late Oligocene, circa 26-24 Ma, and that by the early Miocene, the adaptive radiation of many different hominoid
forms was well underway.[85] Evidence from the molecular dating of genetic differences indicates that the gibbon
lineage (family Hylobatidae) diverged between 18 and 12 Ma, and the orangutan lineage (subfamily Ponginae)
diverged about 12 Ma. While there is no fossil evidence thus far clearly documenting the early ancestry of gibbons,
fossil proto-orangutans may be represented by Sivapithecus from India and Griphopithecus from Turkey, dated to
around 10 Ma. Molecular evidence further suggests that between 8 and 4 Ma, first the gorillas, and then the
chimpanzee (genus Pan) split from the line leading to the humans.[86] We have no fossil record of this divergence,
but distinctively hominid fossils have been found dating to 3.2 Ma (see Lucy) and possibly even earlier, at 6 or 7 Ma
(see Toumaï).[87] Comparisons of chimpanzee and human DNA show the two are approximately 98.4 percent
identical, and are taken as strong evidence of recent common ancestry.[88] Today, only one distinct human species
survives, but many earlier species have been found in the fossil record, including Homo erectus, Homo habilis, and
Homo neanderthalensis.
Creationists dispute there is evidence of shared ancestry in the fossil evidence, and argue either that these are
misassigned ape fossils (e.g. that Java man was a gibbon[89] ) or too similar to modern humans to designate them as
distinct or transitional forms.[90] However Creationists frequently disagree where the dividing lines would be.[91]
Creation myths (such as the Book of Genesis) frequently posit a first man (Adam, in the case of Genesis) as an
alternative viewpoint to the scientific account.
Creationists also dispute science's interpretation of genetic evidence in the study of human evolution. They argue that
it is a "dubious assumption" that genetic similarities between various animals imply a common ancestral relationship,
and that scientists are coming to this interpretation only because they have preconceived notions that such shared
relationships exist. Creationists also argue that genetic mutations are strong evidence against evolutionary theory
because the mutations required for major changes to occur would almost certainly be detrimental.[31]

Macroevolution
Many creationists now accept the possibilities of microevolution within "kinds" but refuse to accept and have long
argued against the possibility of macroevolution. Macroevolution is defined by the scientific community to be
evolution that occurs at or above the level of species. Under this definition, macroevolution can be considered to be a
fact, as evidenced by observed instances of speciation. Creationists however tend to apply a more restrictive, if
vaguer, definition of macroevolution, often relating to the emergence of new body forms or organs. The scientific
community considers that there is strong evidence for even such more restrictive definitions, but the evidence for this
is more complex.
Recent arguments against (such restrictive definitions of) macroevolution include the intelligent design arguments of
irreducible complexity and specified complexity. However, neither argument has been accepted for publication in a
peer-reviewed scientific journal, and both arguments have been rejected by the scientific community as
pseudoscience. Further when taken to court in attempt to introduce ID into the classroom, the judge wrote "The
overwhelming evidence at trial established that ID is a religious view, a mere re-labeling of creationism, and not a
scientific theory."
Biologist Richard Dawkins published a book 'The Greatest Show on Earth: The Evidence for Evolution' giving
evidence for evolution and Macroevolution.
Creation–evolution controversy 343

Transitional fossils
It is commonly stated by critics of evolution that there are no known transitional fossils.[92] [93] This position is based
on a misunderstanding of the nature of what represents a transitional feature. A common creationist argument is that
no fossils are found with partially functional features. It is plausible, however, that a complex feature with one
function can adapt a wholly different function through evolution. The precursor to, for example, a wing, might
originally have only been meant for gliding, trapping flying prey, and/or mating display. Nowadays, wings can still
have all of these functions, but they are also used in active flight.
As another example, Alan Haywood stated in Creation and
Evolution that "Darwinists rarely mention the whale because it
presents them with one of their most insoluble problems. They
believe that somehow a whale must have evolved from an
ordinary land-dwelling animal, which took to the sea and lost
its legs ... A land mammal that was in the process of becoming
a whale would fall between two stools—it would not be fitted
Reconstruction of Ambulocetus natans
for life on land or at sea, and would have no hope for
survival."[94] The evolution of whales has however been
documented in considerable detail, with Ambulocetus, described as looking like a three-metre long mammalian
crocodile, as one of the transitional fossils.

Although transitional fossils elucidate the evolutionary transition of one life-form to another, they only exemplify
snapshots of this process. Due to the special circumstances required for preservation of living beings, only a very
small percentage of all life-forms that ever have existed can be expected to be discovered. Thus, the transition itself
can only be illustrated and corroborated by transitional fossils, but it will never be known in detail. However,
progressing research and discovery managed to fill in several gaps and continues to do so. Critics of evolution often
cite this argument as being a convenient way to explain off the lack of 'snapshot' fossils that show crucial steps
between species.
The theory of punctuated equilibrium developed by Stephen Jay Gould and Niles Eldredge is often mistakenly drawn
into the discussion of transitional fossils. This theory, however, pertains only to well-documented transitions within
taxa or between closely related taxa over a geologically short period of time. These transitions, usually traceable in
the same geological outcrop, often show small jumps in morphology between periods of morphological stability. To
explain these jumps, Gould and Eldredge envisaged comparatively long periods of genetic stability separated by
periods of rapid evolution. For example the change from a creature the size of a mouse, to one the size of an
elephant, could be accomplished over 60,000 years, with a rate of change too small to be noticed over any human
lifetime. 60,000 years is too small a gap to be identified or identifiable in the fossil record.[95]
Furthermore, promoters of evolution (such as Richard Dawkins) have pointed out that, even if it were possible for
enough fossils to survive to show a close transitional change, evolution's critics will never be satisfied, as the
discovery of one "missing link" itself creates two more so-called "missing links" on either side of the discovery.
Dawkins goes on to say that the reason for this "losing battle" is that many of these critics are theists who "simply
don't want to see the truth".

Geology
Many believers in Young Earth Creationism – a position held by the majority of proponents of Flood Geology –
accept biblical chronogenealogies (such as the Ussher chronology which in turn is based on the Masoretic version of
the Genealogies of Genesis).[96] [97] They believe that God created the universe approximately 6000 years ago, in the
space of six days. Much of creation geology is devoted to debunking the dating methods used in anthropology,
geology, and planetary science that give ages in conflict with the young Earth idea. In particular, creationists dispute
the reliability of radiometric dating and isochron analysis, both of which are central to mainstream geological
Creation–evolution controversy 344

theories of the age of the Earth. They usually dispute these methods based on uncertainties concerning initial
concentrations of individually considered species and the associated measurement uncertainties caused by diffusion
of the parent and daughter isotopes. However, a full critique of the entire parameter-fitting analysis, which relies on
dozens of radionuclei parent and daughter pairs, has not been done by creationists hoping to cast doubt on the
technique.
The consensus of professional scientific organisations worldwide is that no scientific evidence contradicts the age of
approximately 4.5 billion years.[98] Young Earth creationists reject these ages on the grounds of what they regard as
being tenuous and untestable assumptions in the methodology. Apparently inconsistent radiometric dates are often
quoted to cast doubt on the utility and accuracy of the method. Mainstream proponents who get involved in this
debate point out that dating methods only rely on the assumptions that the physical laws governing radioactive decay
have not been violated since the sample was formed (harking back to Lyell's doctrine of uniformitarianism). They
also point out that the "problems" that creationists publicly mentioned can be shown to either not be problems at all,
are issues with known contamination, or simply the result of incorrectly evaluating legitimate data.

Other sciences

Cosmology
Whilst Young Earth Creationists believe that the Universe was created by the Judeo-Chrisitian God approximately
6000 years ago, the current scientific consensus is that the Universe as we know it emerged from the Big Bang 13.7
billion years ago. The recent science of nucleocosmochronology is extending the approaches used for Carbon-14
dating to the dating of astronomical features. For example based upon this emerging science, the Galactic thin disk
of the Milky Way galaxy is estimated to have been formed 8.3 ± 1.8 billion years ago.[99]
Old Earth Creationists and some others do not necessarily dispute these figures.

Nuclear physics
Creationists point to experiments they have performed, which they claim demonstrate that 1.5 billion years of
nuclear decay took place over a short period of time, from which they infer that "billion-fold speed-ups of nuclear
decay" have occurred, a massive violation of the principle that radioisotope decay rates are constant, a core principle
underlying nuclear physics generally, and radiometric dating in particular.[100]
The scientific community points to numerous flaws in these experiments, to the fact that their results have not been
accepted for publication by any peer-reviewed scientific journal, and to the fact that the creationist scientists
conducting them were untrained in experimental geochronology.[101] [102]
In refutation of young-Earth claims of inconstant decay rates affecting the reliability of radiometric dating, Roger C.
Wiens, a physicist specialising in isotope dating states:
There are only three quite technical instances where a half-life changes, and these do not affect the dating
methods [under discussion]":[103]
1. Only one technical exception occurs under terrestrial conditions, and this is not for an isotope used for dating.
... The artificially-produced isotope, beryllium-7 has been shown to change by up to 1.5%, depending on its
chemical environment. ... [H]eavier atoms are even less subject to these minute changes, so the dates of rocks
made by electron-capture decays would only be off by at most a few hundredths of a percent.
2. ... Another case is material inside of stars, which is in a plasma state where electrons are not bound to atoms.
In the extremely hot stellar environment, a completely different kind of decay can occur. 'Bound-state beta
decay' occurs when the nucleus emits an electron into a bound electronic state close to the nucleus. ... All
normal matter, such as everything on Earth, the Moon, meteorites, etc. has electrons in normal positions, so
these instances never apply to rocks, or anything colder than several hundred thousand degrees. ...
Creation–evolution controversy 345

3. The last case also involves very fast-moving matter. It has been demonstrated by atomic clocks in very fast
spacecraft. These atomic clocks slow down very slightly (only a second or so per year) as predicted by
Einstein's theory of relativity. No rocks in our solar system are going fast enough to make a noticeable change
in their dates. ...
—Roger C. Wiens, Radiometric Dating, A Christian Perspective[104]

Misrepresentations of science

Quote mining
As a means to criticise mainstream science, creationists have been known to quote, at length, scientists who
ostensibly support the mainstream theories, but appear to acknowledge criticisms similar to those of creationists.[105]
However, almost universally these have been shown to be quote mines that do not accurately reflect the evidence for
evolution or the mainstream scientific community's opinion of it, or highly out-of-date.[106] [107] Many of the same
quotes used by creationists have appeared so frequently in Internet discussions due to the availability of cut and paste
functions, that the TalkOrigins Archive has created "The Quote Mine Project" for quick reference to the original
context of these quotations.[106]

Public policy issues

Science education
Creationists promote that evolution is a theory in crisis[108] [109] with scientists criticizing evolution[110] and claim
that fairness and equal time requires educating students about the alleged scientific controversy.
Opponents, being the overwhelming majority of the scientific community and science education organizations,[111]
reply that there is no scientific controversy and that the controversy exists solely in terms of religion and politics.[108]
[110]
The American Association for the Advancement of Science and other science and education professional
organizations say that Teach the Controversy proponents seek to undermine the teaching of evolution[108] [112] while
promoting intelligent design,[113] [114] [115] and to advance an education policy for US public schools that introduces
creationist explanations for the origin of life to public-school science curricula.[116] [117] This viewpoint was
supported by the December 2005 ruling in the Kitzmiller v. Dover Area School District trial.[117]
George Mason University Biology Department introduced a course on the creation/evolution controversy, and
apparently as students learn more about biology, they find objections to evolution less convincing, suggesting that
“teaching the controversy” rightly as a separate elective course on philosophy or history of science, or "politics of
science and religion," would undermine creationists’ criticisms, and that the scientific community’s resistance to this
approach was bad public relations.[118]
On March 27, 2009, the Texas Board of Education, by a vote of 13 to 2, voted that at least in Texas, textbooks must
teach intelligent design alongside evolution, and question the validity of the fossil record. Don McLeroy, a dentist
and chair of the board, said, "I think the new standards are wonderful ... dogmatism about evolution" has sapped
"America's scientific soul." According to Science magazine, "Because Texas is the second-largest textbook market in
the United States, publishers have a strong incentive to be certified by the board as 'conforming 100% to the state's
standards'."[119]
Creation–evolution controversy 346

Freedom of speech
Creationists have claimed that preventing them from teaching Creationism violates their right of Freedom of speech.
However court cases (such as Webster v. New Lenox School District and Bishop v. Aronov) have upheld school
districts' and universities' right to restrict teaching to a specified curriculum.

Issues relating to religion

Religion and historical scientists

Creationists often argue that Christianity and literal belief in the Bible are either foundationally significant or directly
responsible for scientific progress.[120] To that end, Institute for Creation Research founder Henry M. Morris has
enumerated scientists such as astronomer and philosopher Galileo, mathematician and theoretical physicist James
Clerk Maxwell, mathematician and philosopher Blaise Pascal, geneticist monk Gregor Mendel, and Isaac Newton as
believers in a biblical creation narrative.[121]
This argument usually involves scientists either who were no longer alive when evolution was proposed or whose
field of study didn't include evolution. The argument is generally rejected as specious by those who oppose
creationism.[122]
Many of the scientists in question did some early work on the mechanisms of evolution, e.g., the Modern
evolutionary synthesis combines Darwin's Evolution with Mendel's theories of inheritance and genetics. Though
biological evolution of some sort had become the primary mode of discussing speciation within science by the
late-19th century, it was not until the mid-20th century that evolutionary theories stabilized into the modern
synthesis. Some of the historical scientists marshalled by creationists were dealing with quite different issues than
any are engaged with today: Louis Pasteur, for example, opposed the theory of spontaneous generation with
biogenesis, an advocacy some creationists describe as a critique on chemical evolution and abiogenesis. Pasteur
accepted that some form of evolution had occurred and that the Earth was millions of years old.[123]
The relationship between science and religion was not portrayed in antagonistic terms until the late-19th century, and
even then there have been many examples of the two being reconcilable for evolutionary scientists.[124] Many
historical scientists wrote books explaining how pursuit of science was seen by them as fulfillment of spiritual duty
in line with their religious beliefs. Even so, such professions of faith were not insurance against dogmatic opposition
by certain religious people.
Some extensions to this creationist argument have included the incorrect suggestions that Einstein's deism was a tacit
endorsement of creationism or that Charles Darwin converted on his deathbed and recanted evolutionary theory.

Forums for the controversy

Debates
Many creationists and scientists engage in frequent public debates regarding the origin of human life, hosted by a
variety of institutions. However, some scientists disagree with this tactic, arguing that by openly debating supporters
of supernatural origin explanations (creationism and intelligent design), scientists are lending credibility and
unwarranted publicity to creationists, which could foster an inaccurate public perception and obscure the factual
merits of the debate.[125] For example, in May 2004 Dr. Michael Shermer debated creationist Kent Hovind in front of
a predominantly creationist audience. In Shermer's online reflection while he was explaining that he won the debate
with intellectual and scientific evidence he felt it was "not an intellectual exercise," but rather it was "an emotional
drama", with scientists arguing from "an impregnable fortress of evidence that converges to an unmistakable
conclusion", whilst for creationists it is "a spiritual war".[126] While receiving positive responses from creationist
observers, Shermer concluded "Unless there is a subject that is truly debatable (evolution v. creation is not), with a
Creation–evolution controversy 347

format that is fair, in a forum that is balanced, it only serves to belittle both the magisterium of science and the
magisterium of religion."[126] (see: scientific method). Others, like evolutionary biologist Massimo Pigliucci, have
debated Hovind, and have expressed surprise to hear Hovind try "to convince the audience that evolutionists believe
humans came from rocks" and at Hovind's assertion that biologists believe humans "evolved from bananas."[127]
Eugenie Scott of the National Center for Science Education, a non-profit organization dedicated to defending the
teaching of evolution in the public schools, claimed debates are not the sort of arena to promote science to
creationists.[126] Scott says that "Evolution is not on trial in the world of science," and "the topic of the discussion
should not be the scientific legitimacy of evolution" but rather should be on the lack of evidence in creationism.
Stephen Jay Gould adopted a similar position, explaining:
Debate is an art form. It is about the winning of arguments. It is not about the discovery of truth. There are
certain rules and procedures to debate that really have nothing to do with establishing fact — which
[creationists] are very good at. Some of those rules are: never say anything positive about your own position
because it can be attacked, but chip away at what appear to be the weaknesses in your opponent's position.
They are good at that. I don't think I could beat the creationists at debate. I can tie them. But in courtrooms
they are terrible, because in courtrooms you cannot give speeches. In a courtroom you have to answer direct
questions about the positive status of your belief.
—Stephen Jay Gould, lecture 1985[128]

Political lobbying
A wide range of organisations, on both sides of the controversy, are involved in lobbying in an attempt to influence
political decisions relating to the teaching of evolution, at a number of levels. These include the Discovery Institute,
the National Center for Science Education, the National Science Teachers Association, state Citizens Alliances for
Science, and numerous national science associations and state Academies of Science.[129]

In the media
The controversy has been discussed in numerous newspaper articles, reports, op-eds and letters to the editor, as well
as a number of radio and television programmes (including the PBS series, Evolution and Coral Ridge Ministries'
Darwin's Deadly Legacy). This has led some commentators to express a concern at what they see as a highly
inaccurate and biased understanding of evolution among the general public. Edward Humes states:
There are really two theories of evolution. There is the genuine scientific theory and there is the talk-radio
pretend version, designed not to enlighten but to deceive and enrage. The talk-radio version had a packed town
hall up in arms at the Why Evolution Is Stupid lecture. In this version of the theory, scientists supposedly
believe that all life is accidental, a random crash of molecules that magically produced flowers, horses and
humans – a scenario as unlikely as a tornado in a junkyard assembling a 747. Humans come from monkeys in
this theory, just popping into existence one day. The evidence against Darwin is overwhelming, the purveyors
of talk-radio evolution rail, yet scientists embrace his ideas because they want to promote atheism.
—Edward Humes, Unintelligent Designs on Darwin[130]
Creation–evolution controversy 348

Outside the United States

While the controversy has been
prominent in the United States, it has
flared up in other countries as
well.[133] [134] [135]

Europe
Europeans have often regarded the
creation-evolution controversy as an
American matter.[134] However, in
recent years the conflict has become an
issue in a variety of countries including
Germany, the United Kingdom, Italy,
the Netherlands, Poland, and
Serbia.[134] [135] [136] [137]

On 17 September 2007 the Committee [131] [132]

Views on human evolution in various countries.
on Culture, Science and Education of
the Parliamentary Assembly of the Council of Europe issued a report on the attempt by American-inspired
creationists to promote creationism in European schools. It concludes "If we are not careful, creationism could
become a threat to human rights which are a key concern of the Council of Europe.... The war on the theory of
evolution and on its proponents most often originates in forms of religious extremism which are closely allied to
extreme right-wing political movements... some advocates of creationism are out to replace democracy by
theocracy."[138]

Australia
With declining church attendance, there has been some growth in fundamentalist and Pentecostal Christian
denominations.[139] Under the former Queensland state government of Joh Bjelke-Petersen, in 1980 lobbying was so
successful that Queensland allowed the teaching of creationism as science to school children. In 2010 the
Queensland state government introduced the topic of creationism into school classes within the "ancient history"
subject where its origins and nature are discussed as a significant controversy.[140] Public lectures have been given in
rented rooms at Universities, by visiting American speakers, and speakers with doctorates purchased by mail from
Florida sites.[141] One of the most acrimonious aspects of the Australian debate was featured on the science
television program Quantum, about a long-running and ultimately unsuccessful court case by Ian Plimer, Professor
of Geology at Melbourne University, against an ordained minister, Dr. Allen Roberts, who had claimed that there
were remnants of Noah's Ark in eastern Turkey. Although the court found that Dr Roberts had made false and
misleading claims, they were not made in the course of trade or commerce, so the case failed.[142]
Creation–evolution controversy 349

Islamic countries
In recent times, the controversy has become more prominent in Islamic countries.[143] Currently, in Egypt evolution
is taught in schools but Saudi Arabia and Sudan have both banned the teaching of evolution in schools.[133] Creation
science has also been heavily promoted in Turkey and in immigrant communities in Western Europe, primarily by
Harun Yahya.[135]

See also
• Abiogenesis
• Allegorical interpretations of Genesis
• Anti-intellectualism
• Biogenesis
• Clergy Letter Project
• Creation science
• Creationism
• Evidence of common descent
• Evolution and the Roman Catholic Church
• Evolution Sunday
• Evolutionary origin of religions
• Hindu views on evolution
• History of the creation-evolution controversy
• Intelligent design
• Jainism and non-creationism
• Jewish views on evolution
• Level of support for evolution
• List of participants in the creation-evolution controversy
• Mormonism and evolution
• Natural theology
• Objections to evolution
• Politics of creationism
• Project Steve
• Relationship between religion and science
• Teach the Controversy
• Theology of creationism and evolution

Notes
[144]

[1] See Hovind 2006, for example.

[2] An Index to Creationist Claims (http:/ / www. talkorigins. org/ indexcc/ index. html) , Mark Isaak, Talkorigins Archive,Copyright © 2006.
[3] Curry, Andrew (27 February 2009). "Creationist Beliefs Persist in Europe". Science 323 (5918): 1159. doi:10.1126/science.323.5918.1159.
PMID 19251601. "News coverage of the creationism-versus-evolution debate tends to focus on the United States ... But in the past 5 years,
political clashes over the issue have also occurred in countries all across Europe. ... "This isn't just an American problem," says Dittmar Graf
of the Technical University of Dortmund, who organized the meeting".
[4] Larson 2004, pp. 247–263 Chapter titled Modern Culture Wars. See also Ruse 1999, p. 26, who writes "One thing that historians delighted in
showing is that, contrary to the usually held tale of science and religion being always opposed...religion and theologically inclined philosophy
have frequently been very significant factors in the forward movement of science."
[5] Numbers 1992, pp. 3–240
[6] See:
• Peters & Hewlett 2005, p. 1;
Creation–evolution controversy 350

• Kitzmiller v. Dover Area School District, page 20

[7] See:
• Battle on Teaching Evolution Sharpens (http:/ / www. washingtonpost. com/ wp-dyn/ articles/ A32444-2005Mar13. html), Peter Slevin,
Washington Post, Monday, 14 March 2005, Page A01;
• The Political Design of Intelligent Design (http:/ / cstl-cla. semo. edu/ Renka/ Renka_papers/ intell_design. htm), Russell D. Renka, 16
November 2005;
• Politicized Scholars Put Evolution on the Defensive (http:/ / pewforum. org/ news/ display. php?NewsID=5262), Jody Wilgoren, The New
York Times, 21 April 2005
• The Newest Evolution of Creationism (http:/ / www. evcforum. net/ RefLib/ NaturalHistory_200204_Forrest. html), Barbara Forrest,
Natural History, April, 2002, page 80;
• Kitzmiller vs. Dover Area School District, pages 7-9, also pages 64-90
[8] Myers 2006; NSTA 2007; IAP 2006; AAAS 2006; and Pinholster 2006; Ruling, Kitzmiller v. Dover page 83
[9] Larson 2004, p. 258 "Virtually no secular scientists accepted the doctrines of creation science; but that did not deter creation scientists from
advancing scientific arguments for their position." See also Martz & McDaniel 1987, p. 23, a Newsweek article which states "By one count
there are some 700 scientists (out of a total of 480,000 U.S. earth and life scientists) who give credence to creation-science, the general theory
that complex life forms did not evolve but appeared 'abruptly'."
[10] Committee on Revising Science and Creationism, A View from the National Academy of Sciences, National Academy of Sciences and
Institute of Medicine of the National Academies (2008). Science, Evolution, and Creationism (http:/ / www. nap. edu/ catalog.
php?record_id=11876). National Academy of Sciences. p. 12. ISBN 0-309-10586-2. .
[11] Desmond & Moore 1991, pp. 34–35
[12] See":
• van Wyhe 2006;
• Desmond & Moore 1991, pp. 321–323, 503–505.
[13] van Wyhe 2006
[14] AAAS Evolution Dialogues: Science, Ethics and Religion (http:/ / www. aaas. org/ spp/ dser/ images_Doser/ Publications/
evol_dialogue_study_guide. pdf) study guide (pdf)
[15] See:
• Hodge 1874, p. 177;
• Numbers 1992, p. 14;
• Burns, Ralph, Lerner, & Standish 1982, p. 965;
• Huxley 1902
[16] Witham 2002
[17] Barbour 1997
[18] Numbers 1992, p. 14
[19] Numbers 1992, pp. 14–15
[20] Numbers 1992, p. 17
[21] Numbers 1992, p. 18, noting that this applies to published or public skeptics. Many or most Christians may have held on to a literal six days
of creation, but these views were rarely expressed in books and journals. Exceptions are also noted, such as literal interpretations published by
Eleazar Lord (1788-1871) and David Nevins Lord (1792-1880). However, the observation that evolutionary critics had a relaxed interpretation
of Genesis is supported by specifically enumerating: Louis Agassiz (1807-1873); Arnold Henry Guyot (1807-1884); John William Dawson
(1820-1899); Enoch Fitch Burr (1818-1907); George D. Armstrong (1813-1899); Charles Hodge, theologian (1797-1878); James Dwight
Dana (1813-1895); Edward Hitchcock, clergyman and respected Amherst College geologist, (1793-1864); Reverend Herbert W. Morris
(1818-1897); H. L. Hastings (1833?-1899); Luther T. Townsend (1838-1922; Alexander Patterson, Presbyterian evangelist who published The
Other Side of Evolution Its Effects and Fallacy
[22] Numbers(2006) p161
[23] Similar legislation was passed in two other states prior to the Scopes trial, in Oklahoma and Florida. The efforts to enact "Butler Acts" in
other jurisdictions were abandoned after the Scopes trial. See HistoryNet (http:/ / www. historynet. com/ scopes-trial. htm) (describing the
Florida and Oklahoma acts and Scientific American Article (http:/ / www. scientificamerican. com/ article.
cfm?id=50-years-ago-scope-trial-witness& offset=6).
[24] The statute required a minimum fine of $100, and the state Constitution required all fines over $50 to be assessed by a jury. Court's opinion
(http:/ / www. law. umkc. edu/ faculty/ projects/ ftrials/ scopes/ statcase. htm).
[25] In his closing argument, Darrow told the jury that they essentially had no choice but to convict Scopes on the evidence, and he did not hold
that against them. The jury was out for a total of nine minutes (including time for egress and ingress). The jury informed the Court that they
"passed" the question of the sentence to the Court, a move which the judge accepted despite the Constitutional provision establishing a $50
limit on judge-imposed fines.
[26] The Establishment Clause of the First Amendment of the United States Constitution was not, at the time of the Scopes decision in the 1920s,
deemed applicable to the states. Thus, Scopes' constitutional defense on establishment grounds rested solely on the state constitution. See
Court's opinion (http:/ / www. law. umkc. edu/ faculty/ projects/ ftrials/ scopes/ statcase. htm). See generally Incorporation doctrine and
Creation–evolution controversy 351

Everson v. Board of Education (seminal U.S. Supreme Court opinion finally applying the Establishment Clause against states in 1947). See
also Book Review (http:/ / volokh. com/ posts/ 1122414938. shtml) of Professor Larson's Pulitzer Prize winning Summer for the Gods at point
4 ("The constitutional case was largely based on state constitutional law; this was before most of the Bill of Rights had been incorporated and
applied to the states."); Cantwell v. Connecticut (1940 Supreme Court case stating that the Free Exercise Clause of the First Amendment is
incorporated into the Fourteenth Amendment and is therefore applicable against the states); Cookson, Catharine (2003). Encyclopedia of
religious freedom. Taylor & Francis. pp. 132 et seq.. ISBN 0415941814.(explaining incorporation doctrine relative to First Amendment);
Incorporation Doctrine Explained (http:/ / www. crf-usa. org/ bill-of-rights-in-action/ bria-7-4-b. html) by Constitutional Rights Foundation.
[27] The Court accordingly did not address the question of whether the teaching of Creationism in the public schools was unconstitutional.
[28] The Court stated in its opinion that "England and Scotland maintained State churches as did some of the Colonies, and it was intended by
this clause of the Constitution [the Religious Preference Clause] to prevent any such undertaking in Tennessee."
[29] See:
• s:Kitzmiller v. Dover Area School District/2:Context#Page 19 of 139;
• Understanding the Intelligent Design Creationist Movement: Its True Nature and Goals. (http:/ / www. centerforinquiry. net/ uploads/
attachments/ Forrest_Paper. pdf) (pdf) A Position Paper from the Center for Inquiry, Office of Public Policy Barbara Forrest. May, 2007;
• TalkOrigins Archive: Post of the Month: March 2006 (http:/ / www. talkorigins. org/ origins/ postmonth/ mar06. html), The History of
Creationism by Lenny Flank.
[30] Timeline and Myths of Scopes Trial (http:/ / www. antievolution. org/ topics/ law/ scopes/ scopes. html)
[31] Nelkin, Dorothy (2000). The Creation Controversy: Science or Scripture in Schools. New York: iUniverse. pp. 242. ISBN 0-595-00194-7.
[32] Epperson et al. v. Arkansas, 393 U.S. 97 (http:/ / caselaw. lp. findlaw. com/ scripts/ getcase. pl?navby=CASE& court=US& vol=393&
page=97) (U.S. Supreme Court 1968-11-12).
[33] Larson, Edward J. (2003). Trial and Error: The American Controversy Over Creation and Evolution. Oxford University Press. pp. 276.
ISBN 0195154703.
[34] Larson 2004, p. 248,250, see also Dobzhansky 1973
[35] Larson 2004, p. 251
[36] Larson 2004, p. 252
[37] Larson 2004, p. 255,Numbers 1992, pp. xi,200–208
[38] Larson 2004, p. 255
[39] Numbers 1992, pp. 284–285
[40] Numbers 1992, pp. 284–6
[41] Quoting Larson 2004, pp. 255–256: "Fundamentalists no longer merely denounced Darwinism as false; they offered a scientific-sounding
alternative of their own, which they called either 'scientific creationism (as distinct from religious creationism) or 'creation science' (as
opposed to evolution science."
[42] Larson 2004, pp. 254–255, Numbers 1998, pp. 5–6
[43] Ruling, Kitzmiller v. Dover Area School District pp 7-9.
[44] "NCSE Resource" (http:/ / ncse. com/ creationism/ general/ evolving-banners-at-discovery-institute). Evolving Banners at the Discovery
Institute. 2002-08-29. . Retrieved 2009-04-07.
[45] "Top Questions-1.What is the theory of intelligent design?" (http:/ / www. discovery. org/ csc/ topQuestions.
php#questionsAboutIntelligentDesign). Discovery Institute. . Retrieved 2007-05-13..
[46] Verderame 2007,Simon 2006
[47] Dewey 1994, p. 31, and Wiker 2003, summarizing Gould.
[48] Larson 2004, p. 258 "Virtually no secular scientists accepted the doctrines of creation science; but that did not deter creation scientists from
advancing scientific arguments for their position." See also Martz & McDaniel 1987, p. 23, a Newsweek article which states "By one count
there are some 700 scientists (out of a total of 480,000 U.S. earth and life scientists) who give credence to creation-science, the general theory
that complex life forms did not evolve but appeared 'abruptly'."
[49] Statement from the Council of the Biological Society of Washington (http:/ / web. archive. org/ web/ 20070926214521/ http:/ / www.
biolsocwash. org/ id_statement. html) at the Wayback Machine (archived September 26, 2007).
[50] Bumiller 2005, Peters & Hewlett 2005, p. 3
[51] Some question group's move with elections nearing (http:/ / www. 6newslawrence. com/ news/ 2006/ jul/ 07/
many_question_groups_move_elections_nearing/ ) 6News Lawrence, Lawrence Journal-World. 7 July 2006.
[52] Evolution’s foes lose ground in Kansas (http:/ / www. msnbc. msn. com/ id/ 14137751/ ) MSNBC, 2 August 2006.
[53] Evolution of Kansas science standards continues as Darwin's theories regain prominence (http:/ / www. iht. com/ articles/ ap/ 2007/ 02/ 13/
america/ NA-GEN-US-Kansas-Evolution-History. php) The Associated Press, via the International Herald Tribune, 13 February 2007.
[54] The "Evolution" of Creationism (http:/ / www. pfaw. org/ pfaw/ general/ default. aspx?oid=20418& print=yes& units=all) Timeline: how
creationism has "evolved". People for the American Way.
[55] Kitzmiller v. Dover Area School District, 04 cv 2688 (December 20, 2005)., Conclusion of Ruling.
[56] Johnson 1998, Hodge 1874, p. 177, Wiker 2003, Peters & Hewlett 2005, p. 5--Peters and Hewlett argue that the atheism of many
evolutionary supporters must be removed from the debate
[57] Lenski 2000, p. Conclusions
[58] Johnson 1998
Creation–evolution controversy 352

[59] Einstein 1930, pp. 1–4

[60] Dawkins 1997
[61] Free Executive Summary (http:/ / www. nap. edu/ execsumm_pdf/ 6024. pdf), Science and Creationism: A View from the National Academy
of Sciences, Second Edition, Steering Committee on Science and Creationism, National Academy of Sciences, 1999, ISBN
978-0-309-06406-4.
[62] Johnson 1993, p. 63, Tolson 2005, Moran 1993 ; Selman v. Cobb County School District (http:/ / www. aclu. org/ FilesPDFs/ cobb county
decision. pdf). US District Court for the Northern District of Georgia (2005); Talk. Origins; Bill Moyers et al., 2004. " Now with Bill Moyers
(http:/ / www. pbs. org/ now/ transcript/ transcript349_full. html#dawkins)." PBS. Accessed 2006-01-29. Interview with Richard Dawkins
[63] Merriam-Webster online dictionary. www.m-w.com
[64] Gould 1981
[65] See:
• Number 1992, p. 247;
• Wilkins, John S, Evolution and Philosophy: Is Evolution Science, and What Does 'Science' Mean? (http:/ / www. talkorigins. org/ faqs/
evolphil/ falsify. html), TalkOrigins Archive
[66] Popper 1976, p. 168 and 172 quoted in Kofahl 1981
[67] Unknown sociologist quoted in Numbers 1992, p. 247
[68] Kofahl 1989 as quoted by Numbers 1992, p. 247
[69] Lewin 1982
[70] Numbers(2006) p274
[71] Kofahl 1981, p. 873
[72] Talkorigins summary of Karl Popper attitudes towards evolution (http:/ / www. talkorigins. org/ indexcc/ CA/ CA211_1. html)
[73] Karl Popper (1978). "Natural selection and the emergence of mind" (http:/ / www. informationphilosopher. com/ solutions/ philosophers/
popper/ natural_selection_and_the_emergence_of_mind. html). Dialectica 32(3/4): 339–355. ., Massimo Pigliucci (Sept-October 2004). "Did
Popper refute evolution?" (http:/ / www. lehman. edu/ deanhum/ philosophy/ platofootnote/ PlatoFootnote. org/ Outreach_files/ 2004-Did
Popper refute evolution?-Skeptical Inquirer. pdf). Skeptical Inquirer. .
[74] Ruse 1999, pp. 13–37, which discusses conflicting ideas about science among Karl Popper, Thomas Samuel Kuhn, and their disciples.
[75] As quoted by Wallis 2005, p. 32. Also see Dawkins 1986 and Dawkins 1995
[76] Wallis 2005, p. 6 Dawkins quoting Haldane
[77] Dorman 1996
[78] "One thing we have come to realise in Creation Science is that the Lord has not just called us to knock down evolution, but to help in
restoring the foundation of the gospel in our society. We believe that if the churches took up the tool of Creation Evangelism in society, not
only would we see a stemming of the tide of humanistic philosophy, but we would also see the seeds of revival sown in a culture which is
becoming increasingly more pagan each day.
...
It is also worth noting the comment in the book, ‘By Their Blood-Christian Martyrs of the 20th Century’ (Most Media) by James and Marti
Helfi, on page 49 and 50: ‘New philosophies and theologies from the West also helped to erode Chinese confidence in Christianity. A new
wave of so-called missionaries from mainline Protestant denominations came teaching evolution and a non-supernatural view of the Bible.
Methodist, Presbyterian, Congregationalist, and Northern Baptist schools were especially hard hit. Bertrand Russell came from England
preaching atheism and socialism. Destructive books brought by such teachers further undermined orthodox Christianity. The Chinese
Intelligentsia who had been schooled by Orthodox Evangelical Missionaries were thus softened for the advent of Marxism.’ Evolution is
destroying the Church and society, and Christians need to be awakened to that fact!" Ham, Ken. Creation Evangelism (http:/ / www.
answersingenesis. org/ creation/ v6/ i2/ creationII. asp) (Part II of Relevance of Creation). Creation Magazine '6'(2):17, November 1983.
[79] "...I want to list seventeen summary statements which, if true, provide abundant reason why the reader should reject evolution and accept
special creation as his basic world-view. ...

13. Belief in special creation has a salutary influence on mankind, since it encourages responsible obedience to the
Creator and considerate recognition of those who were created by Him. ...
16. Belief in evolution and animal kinship leads normally to selfishness, aggressiveness, and fighting between
groups, as well as animalistic attitudes and behaviour by individuals." Henry M. Morris, The Remarkable Birth of
Planet Earth (Creation-Life Publishers, 1972), pp. vi-viii. Cited in Appeal to Consequences (http:/ / www.
fallacyfiles.org/adconseq.html), Fallacy Files
[80] Johnson 1993, p. 69 where Johnson cites three pages spent in Issac Asimov's New Guide to Science that take creationists to task, while only
spending one half page on evidence of evolution.
[81] Evolution: what's the real controversy? (http:/ / arstechnica. com/ journals/ science. ars/ 2008/ 05/ 07/ evolution-whats-the-real-controversy),
John Timmer, Nobel Intent, 7 May 2008
[82] The Discontinuity of Life (http:/ / www. answersingenesis. org/ articles/ am/ v4/ n1/ discontinuity), Kurt Wise, Answers in Genesis
[83] A Primer on the Tree of Life (http:/ / www. discovery. org/ a/ 10651), Casey Luskin, Center for Science and Culture, Discovery Institute
[84] Evolution versus the People (http:/ / www. icr. org/ article/ evolution-versus-people/ ), Henry M. Morris, Institute for Creation Research
Creation–evolution controversy 353

[85] Stringer, Chris; Andrews, Peter (2005). The complete world of human evolution. London: Thames & Hudson. pp. 240. ISBN 0-500-05132-1.
[86] Relethford, John (2003). Reflections of our past: how human history is revealed in our genes. Boulder, Colo: Westview Press. pp. 257.
ISBN 0-8133-3958-8.
[87] "Toumaï the Human Ancestor: Skull of Oldest Known Hominid Unearthed in Chad" (http:/ / www. npr. org/ programs/ atc/ features/ 2002/
july/ toumai/ index. html). NPR: All Things Considered. . Retrieved 2009-02-21.
[88] Chimps are human, gene study implies (http:/ / www. newscientist. com/ article/ dn3744-chimps-are-human-gene-study-implies. html) New
Scientist, website, 19 May 2003
[89] Was Java Man a gibbon? (http:/ / www. talkorigins. org/ faqs/ homs/ gibbon. html), Jim Foley, TalkOrigins website, 30 April 2003.
[90] See disputes over the classification of Neanderthals in The Counter-Creationism Handbook, Mark Isaak, University of California Press
(2007), ISBN 978-0520249264
[91] Comparison of all skulls (http:/ / www. talkorigins. org/ faqs/ homs/ compare. html), Jim Foley, TalkOrigins website, 8 August 2005.
[92] Scientific Creationism, Henry M. Morris, 1985, pp. 78-90
[93] Life—How Did It Get Here?, Watchtower Bible and Tract Society, 1985, pp. 57-59
[94] Haywood, Alan (1985) Creation and Evolution.Triangle Books, London. Quoted in Hooking Leviathan by Its Past (http:/ / www.
stephenjaygould. org/ library/ gould_leviathan. html), Stephen Jay Gould
[95] Exploring the Way Life Works, Mahlon B. Hoagland, Bert Dodson, Judith Hauck, p298
[96] Biblical chronogenealogies (http:/ / www. answersingenesis. org/ tj/ v17/ i3/ chronogenealogies. asp)
[97] The Meaning of the Chronogenealogies of Genesis 5 and 11 (http:/ / www. grisda. org/ origins/ 07053. htm)
[98] IAP Statement on the Teaching of Evolution (http:/ / www. interacademies. net/ Object. File/ Master/ 6/ 150/ Evolution statement. pdf),
Interacademy Panel on Global Issues, 21 June 2006.
[99] Del Peloso, E.F.; Da Silva, L.; De Mello, G.F.P.; Arany-prado, L.I. (2005). "The age of the Galactic thin disk from Th/Eu
nucleocosmochronology". A&A 434: 301–308. doi:10.1051/0004-6361:20047060.
[100] Nuclear Decay: Evidence For A Young World (http:/ / www. icr. org/ index. php?module=articles& action=view& ID=302), D. Russell
Humphreys, Impact, Number 352, October 2002.
[101] Young-Earth Creationist Helium Diffusion "Dates" Fallacies Based on Bad Assumptions and Questionable Data (http:/ / www. talkorigins.
org/ faqs/ helium/ zircons. html), Kevin R. Henke, TalkOrigins website, Original version: 17 March 2005, Revision: 24 November 2005.
[102] R.A.T.E: More Faulty Creation Science from The Institute for Creation Research (http:/ / gondwanaresearch. com/ rate. htm), J. G. Meert,
Gondwana Research, The Official Journal of the International Association for Gondwana, 13 November 2000 (updated 6 February 2003).
[103] Dating methods discussed were potassium-argon dating, argon-argon dating, rubidium-strontium dating, samarium-neodymium dating,
lutetium-hafnium, rhenium-osmium dating, and uranium-lead dating.
[104] Radiometric Dating, A Christian Perspective (http:/ / www. asa3. org/ ASA/ resources/ Wiens. html#page 20), Roger C. Wiens, American
Scientific Affiliation, p20-21
[105] Dobzhansky 1973
[106] Pieret 2006
• Isaak, Mark (2004). "Index to Creationist Claims: Claim CA113" (http:/ / www. talkorigins. org/ indexcc/ CA/ CA113. html). Talk.origins.
. Retrieved 2007-12-27.
• Dunford, Mike (2007-07-02). "A new (mis)take on an old paper (and other posts)" (http:/ / web. archive. org/ web/ 20071209204412/
http:/ / www. pandasthumb. org/ archives/ quote_mines/ ). The Panda's Thumb (blog). Archived from the original (http:/ / www.
pandasthumb. org/ archives/ quote_mines/ ) on 2007-12-09. . Retrieved 2007-12-26.
• Myers, PZ (2004-09-11). "I'm shocked, shocked to find that quote mining is going on in there!" (http:/ / pharyngula. org/ index/ weblog/
comments/ im_shocked_shocked_to_find_that_quote_mining_is_going_on_in_there). Pharyngula. . Retrieved 2007-12-27.
[108] "Some bills seek to discredit evolution by emphasizing so-called "flaws" in the theory of evolution or "disagreements" within the scientific
community. Others insist that teachers have absolute freedom within their classrooms and cannot be disciplined for teaching non-scientific
"alternatives" to evolution. A number of bills require that students be taught to "critically analyze" evolution or to understand "the
controversy." But there is no significant controversy within the scientific community about the validity of the theory of evolution. The current
controversy surrounding the teaching of evolution is not a scientific one." AAAS Statement on the Teaching of Evolution (http:/ / www. aaas.
org/ news/ releases/ 2006/ pdf/ 0219boardstatement. pdf) American Association for the Advancement of Science. 16 February 2006 (PDF file)
[109] Ruling, Kitzmiller v. Dover Area School District, page 89
[110] "That this controversy is one largely manufactured by the proponents of creationism and intelligent design may not matter, and as long as
the controversy is taught in classes on current affairs, politics, or religion, and not in science classes, neither scientists nor citizens should be
concerned." Intelligent Judging — Evolution in the Classroom and the Courtroom (http:/ / content. nejm. org/ cgi/ content/ full/ 354/ 21/ 2277)
George J. Annas, New England Journal of Medicine, Volume 354:2277-25 May 2281 2006
[111] See: 1) List of scientific societies rejecting intelligent design 2) Kitzmiller v. Dover page 83. The Discovery Institute's Dissent From
Darwin Petition (http:/ / www. dissentfromdarwin. org/ ) has been signed by about 500 scientists. The AAAS, the largest association of
scientists in the U.S., has 120,000 members, and firmly rejects intelligent design and denies that there is a legitimate scientific controversy
(http:/ / www. aaas. org/ news/ releases/ 2002/ 1106id2. shtml). More than 70,000 Australian scientists and educators condemn teaching of
intelligent design in school science classes (http:/ / www. science. unsw. edu. au/ news/ 2005/ intelligent. html). Statements from Scientific
Organizations (http:/ / ncse. com/ media/ voices/ science) on the status intelligent design and other forms of creationism.
Creation–evolution controversy 354

[112] "In summary, the disclaimer singles out the theory of evolution for special treatment, misrepresents its status in the scientific community,
causes students to doubt its validity without scientific justification, presents students with a religious alternative masquerading as a scientific
theory, directs them to consult a creationist text as though it were a science resource, and instructs students to forgo scientific inquiry in the
public school classroom and instead to seek out religious instruction elsewhere." Ruling - disclaimer, pg. 49 Kitzmiller v. Dover Area School
District.
[113] "ID's home base is the Center for Science and Culture at Seattle's conservative Discovery Institute. Meyer directs the center; former Reagan
adviser Bruce Chapman heads the larger institute, with input from the Christian supply-sider and former American Spectator owner George
Gilder (also a Discovery senior fellow). From this perch, the ID crowd has pushed a "teach the controversy" approach to evolution that closely
influenced the Ohio State Board of Education's recently proposed science standards, which would require students to learn how scientists
"continue to investigate and critically analyze" aspects of Darwin's theory." Chris Mooney. The American Prospect. 2 December 2002
Survival of the Slickest: How anti-evolutionists are mutating their message (http:/ / www. prospect. org/ print/ V13/ 22/ mooney-c. html)
[114] Teaching Intelligent Design: What Happened When? (http:/ / www. arn. org/ docs/ dembski/ wd_teachingid0201. htm) by William A.
Dembski"The clarion call of the intelligent design movement is to "teach the controversy." There is a very real controversy centering on how
properly to account for biological complexity (cf. the ongoing events in Kansas), and it is a scientific controversy."
[115] Nick Matzke's analysis shows how teaching the controversy using the Critical Analysis of Evolution model lesson plan is a means of
teaching all the intelligent design arguments without using the intelligent design label. No one here but us Critical Analysis-ists... (http:/ /
www. pandasthumb. org/ archives/ 2006/ 07/ no_one_here_but. html) Nick Matzke. The Panda's Thumb, 11 July 2006
[116] "has the effect of implicitly bolstering alternative religious theories of origin by suggesting that evolution is a problematic theory even in
the field of science." ... The effect of Defendants’ actions in adopting the curriculum change was to impose a religious view of biological
origins into the biology course, in violation of the Establishment Clause. Kitzmiller v. Dover Area School District, Conclusion, page 134
[117] "ID's backers have sought to avoid the scientific scrutiny which we have now determined that it cannot withstand by advocating that the
controversy, but not ID itself, should be taught in science class. This tactic is at best disingenuous, and at worst a canard. The goal of the IDM
is not to encourage critical thought, but to foment a revolution which would supplant evolutionary theory with ID."Kitzmiller v. Dover Area
School District, whether ID is science, page 89
[118] AAAS Dialogue on Science, Ethics, and Religion (http:/ / www. aaas. org/ spp/ dser/ 02_Events/ Lectures/ 2006/ 02_Lecture_2006_0420.
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[119] Science, 3 APRIL 2009
[120] Woods 2005, pp. 67–114, Chapter Five: The Church and Science
[121] Morris 1982
[122] Index to Creationist Claims - Claim CA114 (http:/ / talkorigins. org/ indexcc/ CA/ CA114. html) edited by Mark Isaak. 2005
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[125] Why I Won't Debate Creationists (http:/ / richarddawkins. net/ article,119,Why-I-Wont-Debate-Creationists,Richard-Dawkins), Richard
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[126] Shermer, Michael (2004-05-10). "Then a Miracle Occurs: An Obstreperous Evening with the Insouciant Kent Hovind, Young Earth
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[127] Massimo Pigliucci. Denying Evolution: Creationism, Scientism, and the Nature of Science. (Sinauer, 2002): ISBN 0878936599 page 102.
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[141] Plimer, Ian "Telling lies for God- Reason versus Creationism", (Random House)
[142] "Telling Lies for God"? - One Man's Crusade (http:/ / www. abc. net. au/ quantum/ info/ 97lies. htm), accessed 2008-02-05, Quantum. See
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[144] While the term myth is often used colloquially to refer to "a false story", this article uses the term "creation myth" in the formal sense,
common in academic literature, meaning "a religious or supernatural story or explanation that describes the beginnings of humanity, earth,
life, and the universe."

Footnotes

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Angeles Times (2006-02-11), archived from the original (http://philosophy.tamucc.edu/article.pl?sid=06/02/
12/1727208&mode=thread) on 2006-09-04, retrieved 2007-02-03
• Tolson, Jay (2005-09-05), Religion in America (http://www.usnews.com/usnews/culture/articles/050928/
28religion.htm), "Religion in America: Intelligent Design on Trial", U.S. News & World Report, retrieved
2007-01-06
• van Wyhe, John (2006), Charles Darwin: gentleman naturalist: A biographical sketch (http://darwin-online.org.
uk/darwin.html), retrieved 2007-01-24
• Verderame, John (2007), Creation evangelism: cutting through the excess (http://www.answersingenesis.org/
docs2001/0510news.asp), answersingenesis.org, retrieved 2007-02-07
• Wallis, Claudia (2005-08-07), "The Evolution Wars" (http://www.time.com/time/magazine/article/
0,9171,1090909-1,00.html), Time Magazine Retrieved on 2007-01-31
• Wiker, Benjamin D. (July/August 2003), "Does Science Point to God? Part II: The Christian Critics" (http://
www.crisismagazine.com/julaug2003/feature1.htm), Crisis Politics, Culture, and the Church (CRISIS
Magazine), retrieved 2007-01-21
• Witham, Larry A. (2002). "From Broadway to Biophilia". Where Darwin Meets the Bible: Creationists and
Evolutionists in America (kindle ed.). Oxford University Press. Chapter 2, sect. "From Broadway to Biophilia",
para. 9. ISBN 978-0195150452.
• Woods, Thomas E., Jr. (2005), How the Catholic Church Built Western Civilization, Regnery Publishing, Inc.,
ISBN 0-89526-038-7

Published books and other resources

• Burian, RM: 1994. Dobzhansky on Evolutionary Dynamics: Some Questions about His Russian Background; in
Adams, Mark A. (1994). The Evolution of Theodosius Dobzhansky: essays on his life and thought in Russia and
America. Princeton, N.J.: Princeton University Press. ISBN 0-691-03479-6.
• Butler, Samuel (2007). Evolution, Old And New: Or The Theories Of Buffon, Dr. Erasmus Darwin And Lamarck,
As Compared With That Of Charles Darwin (1911). Kessinger Publishing, LLC. ISBN 0548641323.
• Beer, Gillian; Darwin, Charles (1996). The origin of species. Oxford [Oxfordshire]: Oxford University Press.
ISBN 019283438X.
• Gould, Stephen Jay; Dobzhansky, Theodosius Grigorievich (1982). Genetics and the origin of species. New York:
Columbia University Press. ISBN 0231054750.
• Haught, John F. (2010). Making Sense of Evolution: Darwin, God, and the Drama of Life. Louisville:
Westminster John Knox Press. pp. 144. ISBN 9780664232856.
• Henig, Robin Marantz (2000). The monk in the garden: the lost and found genius of Gregor Mendel, the father of
genetics. Boston: Houghton Mifflin. ISBN 0395977657.
• Kutschera U, Niklas KJ (2004). "The modern theory of biological evolution: an expanded synthesis".
Naturwissenschaften 91 (6): 255–76. doi:10.1007/s00114-004-0515-y. PMID 15241603.
• Mayr, Ernst (1985). The Growth of Biological Thought: Diversity, Evolution, and Inheritance. Cambridge, Mass:
Belknap Press. ISBN 0674364465.
• Miller, James H. (2001). An evolving dialogue: theological and scientific perspectives on evolution. Valley Forge,
Pa: Trinity Press International. ISBN 1-56338-349-7.
• Morris, HR (1963). The Twilight of Evolution. Grand Rapids, MI: Baker Pub Group. ISBN 0801058627.
• Numbers, Ronald L. (1993). The creationists. Berkeley: University of California Press. ISBN 0520083938.
• Pennock RT (2003). "Creationism and intelligent design". Annu Rev Genomics Hum Genet 4: 143–63.
doi:10.1146/annurev.genom.4.070802.110400. PMID 14527300.
• Sagan, Carl (1997). The demon-haunted world: science as a candle in the dark. New York: Ballantine Books.
ISBN 0345409469.
Creation–evolution controversy 358

• Scott, E.C. (1997). "Antievolution And Creationism In The United States". Annual Review of Anthropology 26
(1): 263–289. doi:10.1146/annurev.anthro.26.1.263.
• Maynard Smith, "The status of neo-Darwinism," in "Towards a Theoretical Biology" (C.H. Waddington, ed.,
University Press, Edinburgh, 1969.
• Hull, D.L. (1999). "The Use and Abuse of Sir Karl Popper" (http://www.springerlink.com/index/
T4220X33T0284444.pdf). Biology and Philosophy 14 (4): 481–504. doi:10.1023/A:1006554919188. Retrieved
2008-04-11.
• Strobel, Lee (2004). The case for a Creator: a journalist investigates scientific evidence that points toward God.
Grand Rapids, Mich: Zondervan/Willow Creek Resources. ISBN 0310240506.

External links
• Gallup public opinion poll in regards to the concepts of Evolution, Creationism, and Intelligent Design as of May
2007 (http://www.gallup.com/poll/21814/Evolution-Creationism-Intelligent-Design.aspx)
• Data by country regarding the percentage of the population that believes in evolution (http://www.data360.org/
graph_group.aspx?Graph_Group_Id=286)
• Opinion of Tennessee Supreme Court in Scopes v. State (http://www.law.umkc.edu/faculty/projects/ftrials/
scopes/statcase.htm)
Creationism as social policy
• Isaac Asimov, The "Threat" of Creationism. (http://www.stephenjaygould.org/ctrl/azimov_creationism.html)
Evolution versus creationism debates

Location and link Pro-evolution Pro-creationism

Year

1994 Will Provine Phillip E. Johnson

Stanford University (http:/ / webcast. ucsd. edu:8080/ ramgen/
UCSD_TV/ 6287DarSciorPhi. rm)

1996 Kenneth R. Miller Phillip E. Johnson

Nova on-line (http:/ / www. pbs. org/ wgbh/ nova/ odyssey/ debate/ )

1997 Kenneth R. Miller, Michael Phillip E. Johnson, Michael

Firing Line (http:/ / www. bringyou. to/ apologetics/ p45. htm)
Ruse, Eugenie Scott & Behe, David Berlinski & William
Barry Lynn F. Buckley

2007 Lewis Wolpert Steve Fuller

University of London (http:/ / www. pc. rhul. ac. uk/ sites/ debate/
debate_audio. html) ( transcript (http:/ / bcseweb. org. uk/ index. php/
Main/ RoyalHollowayCollegeDebate))
Objections to evolution 359

Objections to evolution
Objections to evolution have been raised since evolutionary ideas came to prominence in the 19th century.[1] When
Charles Darwin published his 1859 book On the Origin of Species, his theory of evolution by natural selection
initially met opposition from alternate scientific theories, but came to be universally accepted by the scientific
community.[2] The observation of evolutionary processes occurring, as well as the current theory explaining that
evidence, have been uncontroversial among mainstream biologists for nearly a century.[3]
Since then, nearly all criticisms of evolution have come from religious sources, rather than from the scientific
community.[4] Although most religions have accepted the occurrence of evolution, such as those advocating theistic
evolution, there still exist religious beliefs which reject evolutionary explanations in favor of creationism, the belief
that a deity supernaturally created the world largely in its current form.[5] The resultant U.S. centric
creation-evolution controversy has been a focal point of recent conflict between religion and science.
In contrast to earlier objections to evolution that were either strictly scientific or explicitly religious, recent
objections to evolution have frequently blurred the distinction between the two. Such objections have often centered
on undermining evolution's scientific basis, with the intent of combating the teaching of evolution as fact and
opposing the spread of "atheistic materialism".[6] Modern creationism is characterized by movements such as
Creation Science, neocreationism, and Intelligent Design which argue that the idea of life being directly "designed"
by a god or intelligence is at least as scientific as evolutionary theory, and should therefore be taught in public
schools. Their arguments against evolution have become widespread, and include objections to evolution's evidence,
methodology, plausibility, morality, and scientific acceptance. The scientific community, however, does not accept
such objections as having any validity, citing detractors' misinterpretations of scientific method, evidence, and basic
physical laws.[7]
While objections primarily originate from the United States, there is widespread belief in creationism in the Muslim
world,[8] South Africa and India[9] with smaller followings in Australia, New Zealand, the United Kingdom and
Canada.[10] However, in India 77% of respondents who had heard of Charles Darwin and knew something about the
theory of evolution agreed it was backed by scientific evidence.[11]

Defining evolution
One of the main sources of confusion and ambiguity in the creation-evolution debate is the definition of evolution
itself. In the context of biology, evolution is genetic changes in populations of organisms over successive
generations. However, the word has a number of different meanings in different fields, from evolutionary
computation to molecular evolution to sociocultural evolution to stellar and galactic evolution. It can even refer to
metaphysical evolution, spiritual evolution, or any of a number of evolutionist philosophies. When biological
evolution is conflated with other evolutionary processes, this can cause errors such as the claim that modern
evolutionary theory says anything about abiogenesis or the Big Bang.[12]
In colloquial contexts, evolution can refer to any sort of progressive development, and often bears a connotation of
gradual improvement: here evolution is understood as a process that results in greater quality or complexity. This
common definition, when misapplied to biological evolution, leads to frequent misunderstandings. For example, the
idea of devolution ("backwards" evolution) is a result of erroneously assuming that evolution is directional or has a
specific goal in mind (cf. orthogenesis). In reality, the evolution of an organism has no "objective" other than
increasing the organism's ability to survive and reproduce in its environment; and its suitability is only defined in
relation to this environment. Biologists do not consider any one species, such as humans, to be more highly evolved
or advanced than another. Certain sources have been criticized for indicating otherwise due to a tendency to evaluate
nonhuman organisms according to anthropocentric standards rather than more objective ones.[13]
Objections to evolution 360

Evolution also does not require that organisms become more complex. Although the history of life shows an
apparent trend towards the evolution of complexity; there is a question if this appearance of increased complexity is
real, or if this conclusion comes from neglecting the fact that the majority of life on earth has always consisted of
prokaryotes.[14] In this view, complexity is not a necessary consequence of evolution; rather, it is a consequence of
the specific circumstances of evolution on Earth, which frequently made greater complexity advantageous, and thus
naturally selected for. Depending on the situation, organisms' complexity can either increase, decrease, or stay the
same, and all three of these trends have been observed in evolution.[13]
Creationist sources frequently define evolution according to a colloquial, rather than scientific, meaning.[15] As a
result, many attempts to rebut evolution do not address the findings of evolutionary biology (see straw man
argument). This also means that advocates of creationism and evolutionary biologists often simply speak past each
other.[12] [16]

History
Various evolutionary ideas came to prominence around
the start of the nineteenth century, in particular the
transmutation of species theory put forward by
Jean-Baptiste Lamarck. These were opposed on
scientific grounds, most notably by Georges Cuvier, as
well as meeting political and religious objections.[1]
These ideas that natural laws controlled the
development of nature and society gained vast popular
audiences with George Combe's The Constitution of
Man of 1828 and the anonymous Vestiges of the
Natural History of Creation of 1844. When Charles
Darwin published his 1859 book On the Origin of
Species, within fifteen to twenty years he convinced
most of the scientific community that evolution through
common descent was true, but while most accepted that
natural selection was a valid and empirically testable
hypothesis, his view that it was the primary mechanism
of evolution was generally rejected.[2]

The earliest objections to Darwinian evolution were

both scientific and religious. Darwin's contemporaries
eventually came to accept the transmutation of species
Darwin's theory of evolution through common descent gained
widespread acceptance, but there was continued resistance to his based upon fossil evidence; forming the X Club to
views on the significance of natural selection. defend it against the church and wealthy amateurs,[17]
although the specific evolutionary mechanism which
Darwin provided – natural selection – was actively disputed by alternative theories such as Lamarckism and
orthogenesis. Darwin's gradualistic account was also opposed by saltationism and catastrophism. Lord Kelvin led
scientific opposition to gradualism on the basis of his thermodynamic calculations that the Age of the Earth was
between 24 and 400 million years old, an estimate strongly disputed by geologists. These figures were corrected in
1907 when radioactive dating of rocks showed that the Earth was billions of years old.[18] [19] Kelvin's own views
favoured a version of theistic evolution speeded up by divine guidance.[20] The specific hereditary mechanism
Darwin provided, pangenesis, lacked any supporting evidence. In the early 20th century, pangenesis was replaced by
Objections to evolution 361

Mendelian inheritance, leading to the rise of the modern evolutionary synthesis. The modern synthesis rose to
universal acceptance among biologists with the help of new evidence, such as genetics, which confirmed Darwin's
predictions and refuted the competing theories.[21]
Protestantism, especially in America, broke out in "acrid polemics" and argument about evolution from 1860 to the
1870s – with the turning point possibly marked with the death of Louis Agassiz in 1873 – and by 1880 a form of
"Christian evolution" was becoming the consensus.[22] In Britain while publication of The Descent of Man by
Darwin in 1871 reinvigorated debate from the previous decade, Sir Henry Chadwick notes a steady acceptance of
evolution "among more educated Christians" between 1860 and 1885. This led evolutionary theory to be "both
permissible and respectable" by 1876.[22] Frederick Temple's lectures on Relations between Religion and Science
(1884) speaking on how evolution was not "antagonistic" to religion highlighted this trend.[23] Temple's appointment
to Archbishop of Canterbury in 1896 showed the broad acceptance of evolution within the church hierarchy.[22]
For decades Catholicism avoided official refutation of evolution. However, it would rein in Catholics who proposed
that evolution could be reconciled with the Bible, as this conflicted with First Vatican Council's (1869–70) finding
that everything was created out of nothing by God, and to question that could lead to excommunication. In 1950, the
encyclical Humani Generis of Pope Pius XII first mentioned evolution directly and officially.[24] It allowed for
inquiry into humans coming from pre-existing living matter, but to not question Adam and Eve or the creation of the
soul. In 1996, Pope John Paul II stated evolution was "more than a hypothesis" and acknowledged the large body of
work accumulated in its support, but reiterated that any attempt to give a material explanation of the human soul was
"incompatible with the truth about man."[25]
Muslim reaction covered the gamut with those believing in literal creation from the Qur'an while many educated
Muslims subscribed to a version of theistic or guided evolution where the Qur'an reinforced rather than contradicted
mainstream science. This occurred relatively quickly as medieval Madrasah's taught ideas of Al-Jahiz, a Muslim
scholar from the 9th century, who proposed concepts similar to natural selection.[8] However, acceptance of
evolution remains low in the Muslim world as prominent figures reject evolution's underpinning philosophy of
materialism as unsound to human origins and a denial of Allah.[8] Further objections by Muslim scholars and writers
largely reflect those put forward in the Western world.[26]
Regardless of acceptance from major religious hierarchies, early religious objections to Darwin's theory are still used
in opposition to evolution. The ideas that species change over time through natural processes and that different
species share common ancestors seemed to contradict the Genesis account of Creation. Believers in Biblical
infallibility attacked Darwinism as heretical. The natural theology of the early 19th century was typified by Paley's
watchmaker analogy, an argument from design still used by the creationist movement. Natural theology included a
range of ideas and arguments from the outset, and when Darwin's theory was published, ideas of theistic evolution
were presented in which evolution is accepted as a secondary cause open to scientific investigation, while still
holding belief in God as a first cause with a non-specified role in guiding evolution and creating humans.[27] This
position has been adopted by denominations of Christianity and Judaism in line with modernist theology which
views the Bible and Torah as allegorical thus removing the conflict between evolution and religion.
However, in the 1920s Christian fundamentalists in the United States developed their literalist arguments against
Modernist theology into opposition to the teaching of evolution due to fears that ‘‘Darwinism’’ had led to German
militarism and was a threat to religion and morality. This opposition developed into the creation-evolution
controversy involving Christian literalists in the United States objecting to the teaching of evolution in public
schools. Although early objections dismissed evolution for contradicting their interpretation of the Bible, this
argument was invalidated when the Supreme Court ruled in Epperson v. Arkansas that forbidding the teaching of
evolution on religious grounds violated the Establishment Clause.[28]
Since then creationists have developed more nuanced objections to evolution, alleging variously that it is
unscientific, infringes on creationists' religious freedoms or that the acceptance of evolution is a religious stance.[29]
Creationists have appealed to democratic principles of fairness, arguing that evolution is controversial, and that
Objections to evolution 362

science classrooms should therefore "Teach the Controversy".[30] These objections to evolution culminated in the
intelligent design movement in the early 2000s that unsuccessfully attempted to present itself as a scientific
alternative to evolution.[31] [32]

Scientific acceptance
Recent objections to evolutionary theory have focused on its scientific validity,[33] [34] or attempting to come up with
alternative ideas such as Creationism to debate its findings.[35] Creationists often argue, for example, that evolution
is unproven, non-factual, or controversial.[36]

Status as a theory
Critics of evolution frequently assert that evolution is "just a theory", with the intent of emphasizing evolution's
unproven nature, or of characterizing it as a matter of opinion rather than of fact or evidence. This reflects a
misunderstanding of the meaning of theory in a scientific context: whereas in colloquial speech a theory is a
conjecture or guess, in science a theory is simply an explanation or model of the world that makes testable
predictions. When evolution is used to describe a theory, it refers to an explanation for the diversity of species and
their ancestry. An example of evolution as theory is the modern synthesis of Darwinian natural selection and
Mendelian inheritance. As with any scientific theory, the modern synthesis is constantly debated, tested, and refined
by scientists. There is an overwhelming consensus in the scientific community that it remains the only robust model
that accounts for the known facts concerning evolution.[37]
Critics state that evolution is not a fact.[38] In science, a fact is a verified empirical observation; in colloquial
contexts, however, a fact can simply refer to anything for which there is overwhelming evidence. For example, in
common usage theories such as "the Earth revolves around the Sun" and "objects fall due to gravity" may be referred
to as "facts", even though they are purely theoretical. From a scientific standpoint, therefore, evolution may be called
a "fact" for the same reason that gravity can: under the scientific definition, evolution is an observable process that
occurs whenever a population of organisms genetically changes over time. Under the colloquial definition, the theory
of evolution can also be called a fact, referring to this theory's well-established nature. Thus, evolution is widely
considered both a theory and a fact by scientists.[39] [40] [41]
Similar confusion is involved in objections that evolution is "unproven";[42] strict proof is possible only in formal
sciences such as logic and mathematics, not natural sciences (where the proper term is "validated"), so this is trivially
true, and no more an indictment of evolution than calling it a "theory". The confusion arises, however, in that the
colloquial meaning of proof is simply "compelling evidence", in which case scientists would indeed consider
evolution "proven". The distinction is an important one in philosophy of science, as it relates to the lack of absolute
certainty in all empirical claims, not just evolution.[43]

Degree of acceptance
In 1999 a new major objection to evolution appeared in Kansas, and is in a sense self-fulfilling: it argues that
evolution is controversial or contentious.[44] Unlike past creationist arguments which sought to abolish the teaching
of evolution altogether, this argument makes the weaker claim that evolution, being controversial, should be
presented alongside other, alternative views, and students should be allowed to evaluate and choose between the
options on their own.[45] This appeal to "fairness" and a more democratic, "balanced" approach in which conflicting
views are given "equal time" appeals to American creationists, and was endorsed by U.S. President George W.
Bush.[32] [42] [46]
This objection forms the basis of the "Teach the Controversy" campaign, an attempt by the Discovery Institute to
promote the teaching of intelligent design in public schools. This in turn forms a major part of the Institute's "wedge
strategy", an attempt to gradually undermine evolution and ultimately to "reverse the stifling materialist world view
and replace it with a science consonant with Christian and theistic convictions".[30]
Objections to evolution 363

Scientists and U.S. courts have rejected this objection on the grounds that science is not based on appeals to
popularity, but on evidence. The scientific consensus of biologists, not popular opinion or fairness, determines what
is considered acceptable science, and it is argued that although evolution is clearly controversial in the public arena,
it is entirely uncontroversial among experts in the field.[47]
In response, creationists have disputed the level of scientific support for evolution. The Discovery Institute has
gathered over 600 scientists since 2001 to sign "A Scientific Dissent From Darwinism" in order to show that there
are a number of scientists who dispute what they refer to as "Darwinian evolution". This statement did not profess
outright disbelief in evolution, but expressed skepticism as to the ability of "random mutation and natural selection to
account for the complexity of life." Several counter-petitions have been launched in turn, including A Scientific
Support for Darwinism, which gathered over 7,000 signatures in four days, and Project Steve, a tongue-in-cheek
petition that has gathered 1,140 (as of August 12, 2010) evolution-supporting scientists named "Steve".
Creationists have argued for over a century that evolution is "a theory in crisis" that will soon be overturned,[48]
based on objections that it lacks reliable evidence or violates natural laws. These objections have been rejected by
most scientists, as have claims that intelligent design, or any other creationist explanation, meets the basic scientific
standards that would be required to make them scientific alternatives to evolution. It is also argued that even if
evidence against evolution exists, it is a false dilemma to characterize this as evidence for intelligent design.[46] [49]
A similar objection to evolution is that certain scientific authorities – mainly pre-modern ones – have doubted or
rejected evolution.[50] Most commonly, it is argued that Darwin "recanted" on his deathbed, a false anecdote
originating from the Lady Hope Story.[51] These objections are generally rejected as appeals to authority. Even if this
myth were true, it would hold no bearing on the merit of the theory itself.

Scientific status
A common neo-creationist objection to evolution is that evolution does not adhere to normal scientific
standards—that it is not genuinely scientific. It is argued that evolutionary biology does not follow the scientific
method, and therefore should not be taught in science classes, or at least should be taught alongside other views (i.e.,
creationism). These objections often deal with the very nature of evolutionary theory and the scientific method.

Religious nature
Creationists commonly argue against evolution on the grounds that "evolution is a religion; it is not a science".[52]
The purpose of this criticism is to undermine the higher ground biologists claim in debating creationists, and to
reframe the debate from being between science (evolution) and religion (creationism) to being between two equally
religious beliefs – or even to argue that evolution is religious while intelligent design is not.[53] [54] Those that
oppose evolution frequently refer to supporters of evolution as "Evolutionists" or "Darwinists".[52]
The arguments for evolution being a religion generally amount to arguments by analogy: it is argued that evolution
and religion have one or more things in common, and that therefore evolution is a religion. Examples of claims made
in such arguments are statements that evolution is based on faith, that supporters of evolution revere Darwin as a
prophet, and that supporters of evolution dogmatically reject alternative suggestions out-of-hand.[42] [55] These
claims have become more popular in recent years as the neocreationist movement has sought to distance itself from
religion, thus giving it more reason to make use of a seemingly anti-religious analogy.[47]
In response, supporters of evolution have argued that no scientist's claims, including Darwin's, are treated as
sacrosanct, as shown by the aspects of Darwin's theory that have been rejected or revised by scientists over the years,
to form first Neo-Darwinism and later the modern evolutionary synthesis.[56] [57] The claim that evolution relies on
faith, often based on the creationist belief that evolution has never been observed, is likewise rejected on the grounds
that evolution has strong supporting evidence, and therefore does not require faith.
Objections to evolution 364

In general, the argument that evolution is religious has been rejected on the grounds that religion is not defined by
how dogmatic or zealous its adherents are, but by its spiritual or supernatural beliefs. Evolutionary supporters point
out evolution is neither dogmatic nor based on faith, and they accuse creationists of equivocating between the strict
definition of religion and its colloquial usage to refer to anything that is enthusiastically or dogmatically engaged in.
U.S. courts have also rejected this objection:
Assuming for the purposes of argument, however, that evolution is a religion or religious tenet, the
remedy is to stop the teaching of evolution, not establish another religion in opposition to it. Yet it is
clearly established in the case law, and perhaps also in common sense, that evolution is not a religion
and that teaching evolution does not violate the Establishment Clause.[58]
A related claim is that evolution is atheistic; creationists sometimes merge the two claims and describe evolution as
an "atheistic religion" (cf. humanism).[54] This argument against evolution is also frequently generalized into a
criticism of all science; it is argued that "science is an atheistic religion", on the grounds that its methodological
naturalism is as unproven, and thus as "faith-based", as the supernatural and theistic beliefs of creationism.[59]

Unfalsifiability
A statement is considered falsifiable if there is an observation or a test that could be made that would demonstrate
that the statement is false. Statements that are not falsifiable cannot be examined by scientific investigation since
they permit no tests that evaluate their accuracy. Creationists such as Henry M. Morris have claimed that evolution is
unfalsifiable. They claim that any observation can be fitted into the evolutionary framework, and that therefore it is
impossible to demonstrate that evolution is wrong. As such, they claim that evolution is non-scientific.[60] [61]
However, evolution is considered falsifiable by scientists because it can
make predictions that, were they contradicted by the evidence, would
falsify evolution. Several kinds of evidence have been proposed that
could falsify evolution, such as the fossil record showing no change over
time, confirmation that mutations are prevented from accumulating, or
observations showing organisms being created supernaturally or
spontaneously.[60] Many of Darwin's ideas and assertions of fact have
been falsified as evolutionary science has developed and has continued
to confirm his central concepts.[62] In contrast, creationism consists
largely of unsubstantiated claims that evolution has been falsified.[60]
Creationist explanations involving the direct intervention of the
supernatural in the physical world are not falsifiable, because any result
of an experiment or investigation could be the unpredictable action of an
omnipotent deity.[63]

In 1976, philosopher Karl Popper said that "Darwinism is not a testable

scientific theory but a metaphysical research programme".[64] However,
Popper later recanted and offered a more nuanced view of its status: Darwin and an ape, circa 1874 from
Julkaistussa picture source.
However, Darwin's own most important contribution to the
theory of evolution, his theory of natural selection, is difficult to test. There are some tests, even some
experimental tests; and in some cases, such as the famous phenomenon known as 'industrial melanism',
we can observe natural selection happening under our very eyes, as it were. Nevertheless, really severe
tests of the theory of natural selection are hard to come by, much more so than tests of otherwise
comparable theories in physics or chemistry.[65] [66]

The most direct evidence that evolutionary theory is falsifiable may be the original words of Charles Darwin who, in
chapter 6 of On the Origin of Species wrote: "If it could be demonstrated that any complex organ existed, which
Objections to evolution 365

could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely
break down."[67]
In response to the unfalsifiability criticism of evolutionary theory, numerous examples of potential ways to falsify
evolution have been proposed. J.B.S. Haldane, when asked what hypothetical evidence could disprove evolution,
replied "fossil rabbits in the Precambrian era".[68] [69] Numerous other potential ways to falsify evolution have also
been proposed.[43] For example, the fact that humans have one fewer pair of chromosomes than the great apes
offered a testable hypotheses involving the fusion or splitting of chromosomes from a common ancestor. The fusion
hypothesis was confirmed in 2005 by discovery that human chromosome 2 is homologous with a fusion of two
chromosomes that remain separate in other primates. Extra, inactive telomeres and centromeres remain on human
chromosome 2 as a result of the fusion.[70] The assertion of common descent could also have been disproven with
the invention of DNA analysis. If true, human DNA should be far more similar to chimpanzees and other great apes,
than to other mammals. If not, then common descent is falsified. DNA analysis has shown that humans and
chimpanzees share a large percentage of their DNA (between 95% to 99.4% depending on the measure).[71] Also, the
evolution of chimpanzees and humans from a common ancestor predicts a (geologically) recent common ancestor.
Numerous transitional fossils have since been found.[72] Hence, human evolution has passed several falsifiable tests.
A related claim, also once used, but then abandoned, by Popper, is that natural selection is tautological.[65]
Specifically, it is often argued that the phrase "survival of the fittest" is a tautology, in that fitness is defined as
ability to survive and reproduce. However, this phrase, first used by Herbert Spencer in 1864, is rarely used by
biologists. Additionally, fitness is more accurately defined as the state of possessing traits that make survival more
likely; this definition, unlike simple "survivability", avoids being trivially true.[73] [74] [75]
Similarly, it is argued that evolutionary theory is circular reasoning, in that evidence is interpreted as supporting
evolution, but evolution is required to interpret the evidence. An example of this is the claim that geological strata
are dated through the fossils they hold, but that fossils are in turn dated by the strata they are in.[42] However, in most
cases strata are not dated by their fossils, but by their position relative to other strata and by radiometric dating, and
most strata were dated before the theory of evolution was formulated.[76]
In his book, Abusing Science: The Case Against Creationism, philosopher of science Philip Kitcher specifically
addresses the "falsifiability" question by taking into account notable philosophical critiques of Popper by Carl
Gustav Hempel and Willard Van Orman Quine that reject his definition of theory as a set of falsifiable
statements.[77] As Kitcher points out, if one took a strictly Popperian view of “theory,” observations of Uranus when
first discovered in 1781 would have “falsified” Newton’s celestial mechanics. Rather, people suggested that another
planet influenced Uranus’ orbit – and this prediction was indeed eventually confirmed. Kitcher agrees with Popper
that “there is surely something right in the idea that a science can succeed only if it can fail.”[78] But he insists that we
view scientific theories as consisting of an “elaborate collection of statements,” some of which are not falsifiable, and
others – what he calls “auxiliary hypotheses,” which are.
According to Kitcher, good scientific theories must have three features – unity, fecundity, and independent
testability of auxiliary hypotheses:
Unity
“A science should be unified .... Good theories consist of just one problem-solving strategy, or a small family
of problem-solving strategies, that can be applied to a wide range of problems” (1982: 47).
Fecundity
A great scientific theory, like Newton’s, opens up new areas of research... Because a theory presents a
new way of looking at the world, it can lead us to ask new questions, and so to embark on new and
fruitful lines of inquiry... Typically, a flourishing science is incomplete. At any time, it raises more
questions than it can currently answer. But incompleteness is no vice. On the contrary, incompleteness is
the mother of fecundity... A good theory should be productive; it should raise new questions and
Objections to evolution 366

presume that those questions can be answered without giving up its problem-solving strategies (1982:
47–48).
Auxiliary hypothesis that are independently testable
“An auxiliary hypothesis ought to be testable independently of the particular problem it is introduced to solve,
independently of the theory it is designed to save” (1982: 46) (e.g. the evidence for the existence of Neptune is
independent of the anomalies in Uranus’s orbit).
Like other definitions of theories, including Popper’s, Kitcher makes it clear that a good theory includes statements
that have (in his terms) “observational consequences.” But, like the observation of irregularities in Uranus’s orbit,
falsification is only one possible consequence of an observation. The production of new hypotheses is another
possible – and equally important – observational consequence. Kitcher’s account of a good theory is based not only
on his understanding of how physical sciences work. He is also taking into account the way the life sciences work.
From Kitcher’s point of view, Darwinian theory not only meets the three conditions for a good scientific theory; it is
without question an extraordinarily successful theory:
The heart of Darwinian evolutionary theory is a family of problem-solving strategies, related by their
common employment of a particular style of historical narrative. A Darwinian history is a piece of
reasoning of the following general form. The first step consists in a description of an ancestral
population of organisms. The reasoning proceeds by tracing the modification of the population through
subsequent generations, showing how characteristics were selected, inherited, and became prevalent.
Reasoning like this can be used to answer a host of biological questions.[79]
The same kind of story can be told again and again to answer all sorts of questions about all sorts of
living things. Evolutionary theory is unified because so many diverse questions ... can be addressed by
advancing Darwinian histories. Moreover, these narratives constantly make claims that are subject to
independent check.[80]
Darwin not only provided a scheme for unifying the diversity of life. He also gave a structure to our
ignorance. After Darwin, it was important to resolve general issues about the presuppositions of
Darwinian histories. The way in which biology should proceed had been made admirably plain, and it
was clear that biologists had to tackle questions for which they had, as yet, no answers.[81]
Objections to evolution 367

Evidence
Objections to the evidence that evolution occurs tend to be more concrete and specific, often involving direct
analysis of evolutionary biology's methods and claims.

Lack of observation
A common claim of creationists is that evolution has
never been observed.[82] Challenges to such objections
often come down to debates over how evolution is
defined (see above). Under the conventional biological
definition of evolution, it is a simple matter to observe
evolution occurring. Evolutionary processes, in the
form of populations changing their genetic composition
from generation to generation, have been observed in
different scientific contexts, including the evolution of
fruit flies, mice and bacteria in the laboratory,[83] and
of tilapia in the field. Such studies on experimental
evolution, particularly those using microorganisms, are
now providing important insights into how evolution
occurs.[83] [84]
Transitional species such as the Archaeopteryx have been a fixture of
In response to such examples, creationists specify that
the creation-evolution debate for almost 150 years.
they are objecting only to macroevolution, not
microevolution:[85] [86] most creationist organizations
do not dispute the occurrence of short-term, relatively minor evolutionary changes, such as that observed even in dog
breeding. Rather, they dispute the occurrence of major evolutionary changes over long periods of time, which by
definition cannot be directly observed, only inferred from microevolutionary processes and the traces of
macroevolutionary ones.

However, as biologists define macroevolution, both microevolution and macroevolution have been observed.
Speciations, for example, have been directly observed many times, despite popular misconceptions to the
contrary.[87] Additionally, the modern evolutionary synthesis draws no distinction between macroevolution and
microevolution, considering the former to simply be the latter on a larger scale.[43] [88] An example of this is ring
species.
Additionally, past macroevolution can be inferred from historical traces. Transitional fossils, for example, provide
plausible links between several different groups of organisms, such as Archaeopteryx linking birds and dinosaurs,[89]
or the recently-discovered Tiktaalik linking fish and limbed amphibians.[90] Creationists dispute such examples, from
asserting that such fossils are hoaxes or that they belong exclusively to one group or the other, to asserting that there
should be far more evidence of obvious transitional species.[91] Darwin himself found the paucity of transitional
species to be one of the greatest weaknesses of his theory: "Why then is not every geological formation and every
stratum full of such intermediate links? Geology assuredly does not reveal any such finely graduated organic chain;
and this, perhaps, is the most obvious and gravest objection which can be urged against my theory. The explanation
lies, as I believe, in the extreme imperfection of the geological record." Darwin appealed to the limited collections
then available, the extreme lengths of time involved, and different rates of change with some living species differing
very little from fossils of the Silurian period. In later editions he added "that the periods during which species have
been undergoing modification, though very long as measured by years, have probably been short in comparison with
the periods during which these same species remained without undergoing any change."[92] The number of clear
transitional fossils has increased enormously since Darwin's day, and this problem has been largely resolved with the
Objections to evolution 368

advent of the theory of punctuated equilibrium, which predicts a primarily stable fossil record broken up by
occasional major speciations.[93]
Creationists counter that even observed speciations and transitional fossils are insufficient evidence for the vast
changes summarized by such phrases as "fish to philosophers" or "particles to people".[94] As more and more
compelling direct evidence for inter-species and species-to-species evolution has been gathered, creationists have
redefined their understanding of what amounts to a "created kind", and have continued to insist that more dramatic
demonstrations of evolution be experimentally produced.[95] One version of this objection is "Were you there?",
popularized by Ken Ham. It argues that because no one except God could directly observe events in the distant past,
scientific claims are just speculation or "story-telling".[96] [97] DNA sequences of the genomes of organisms allow an
independent test of their predicted relationships, since species which diverged more recently will be more closely
related genetically than species which are more distantly related; such phylogenetic trees show a hierarchical
organization within the tree of life, as predicted by common descent.[98] [99]
In fields such as astrophysics or meteorology, where direct observation or laboratory experiments are difficult or
impossible, the scientific method instead relies on observation and logical inference. In such fields, the test of
falsifiability is satisfied when a theory is used to predict the results of new observations. When such observations
contradict a theory's predictions, it may be revised or discarded if an alternative better explains the observed facts.
For example, Newton's theory of gravitation was replaced by Einstein's theory of General Relativity when the latter
was observed to more precisely predict the orbit of Mercury.[100]

Instability of evidence
A related objection is that evolution is based on unreliable evidence. This objection goes further than the less
substantial "evolution isn't proven" arguments, claiming that evolution isn't even well-evidenced. Typically, this is
either based on the argument that evolution's evidence is full of frauds and hoaxes, that current evidence for
evolution is likely to be overturned because past evidence has been, or that certain types of evidence are inconsistent
and dubious.
Arguments against evolution's reliability are thus often based on analyzing the history of evolutionary thought or the
history of science in general. Creationists point out that in the past, major scientific revolutions have overturned
theories that were at the time considered near-certain. They thus claim that current evolutionary theory is likely to
undergo such a revolution in the future, on the basis that it is a "theory in crisis" for one reason or another.[101]
Critics of evolution commonly appeal to past scientific hoaxes such as
the Piltdown Man forgery. It is argued that because scientists have
been mistaken and deceived in the past about evidence for various
aspects of evolution the current evidence for evolution is likely to also
be based on fraud and error. Much of the evidence for evolution has
been accused of being fraudulent at various times, including
Archaeopteryx, peppered moth melanism, and Darwin's finches; these
claims have been subsequently refuted.[103] [104] [105]

It has also been claimed that certain former pieces of evidence for
evolution which are now considered out-of-date and erroneous, such as
Romanes's 1892 copy of Ernst Haeckel's embryo
Ernst Haeckel's 19th-century comparative drawings of embryos, used
drawings, often attributed incorrectly to
to illustrate his Recapitulation theory ("Ontogeny recapitulates [102]
Haeckel.
[106]
Phylogeny"), were not merely errors but frauds. Jonathan Wells
criticizes biology textbooks by alleging that they continue to reproduce such evidence after it has been
debunked.[104] In response, the National Center for Science Education notes that none of the textbooks reviewed by
Objections to evolution 369

Wells makes the claimed error, as Haeckel's drawings are shown in a historical context with discussion about why
they are wrong, and the accurate modern drawings and photos used in the textbooks are misrepresented by
Wells.[107]

Unreliable or inconsistent evidence

Creationists claim that evolution relies on certain types of evidence that do not give reliable information about the
past. It is argued, for example, that radiometric dating, the technique of evaluating a material's age based on the
radioactive decay rates of certain isotopes, generates inconsistent, and thus unreliable, results. Radiocarbon dating,
based on the Carbon 14 isotope, has been particularly criticized. It is argued that radiometric decay relies on a
number of unwarranted assumptions, such as the principle of uniformitarianism, consistent decay rates, or rocks
acting as closed systems. Such arguments have been dismissed by scientists on the grounds that independent
methods have confirmed the reliability of radiometric dating as a whole; additionally, different radiometric dating
methods and techniques have independently confirmed each other's results.[108]
Another form of this objection is that fossil evidence is not reliable. This is based on a much wider range of claims.
These include that there are too many "gaps" in the fossil record,[109] [110] that fossil-dating is circular (see evolution
is unfalsifiable), or that certain fossils, such as polystrate fossils, are seemingly "out of place". Examination by
geologists have found polystrate fossils to be consistent with in situ formation.[111] It is argued that certain features
of evolution support creationism's catastrophism (cf. Great Flood), rather than evolution's gradualistic punctuated
equilibrium,[112] which some assert is an "ad-hoc" theory to explain the fossil gaps.[113]

Plausibility
Some of the oldest and most common objections to evolution dispute whether evolution can truly account for all the
apparent complexity and order in the natural world. It is argued that evolution is too unlikely or otherwise lacking to
account for various aspects of life, and therefore that an intelligence, God, must at the very least be appealed to for
those specific features.

Improbability
A common objection to evolution is that it is simply too unlikely for
life, in its complexity and apparent "design", to have arisen "by
chance". It is argued that the odds of life having arisen without a
deliberate intelligence guiding it are so astronomically low that it is
unreasonable not to infer an intelligent designer from the natural world,
and specifically from the diversity of life.[115] A more extreme version
of this argument is that evolution cannot create complex structures.
The idea that it is simply too implausible for life to have evolved is
often encapsulated with a quotation that the "probability of life
originating on earth is no greater than the chance that a hurricane
sweeping through a scrap-yard would have the luck to assemble a
Boeing 747" (a claim attributed to astrophysicist Fred Hoyle and
known as Hoyle's fallacy).[116]

Because the theory of evolution is often thought This view is thus invariably justified with arguments from analogy.
of as the idea that life arose "by chance", design The basic idea of this argument for a designer is the teleological
arguments such as William Paley's watchmaker
argument, an argument for the existence of God based on the perceived
analogy have been popular objections to the
[114]
theory since Darwin's day.
Objections to evolution 370

order or purposefulness of the universe. A common way of using this as an objection to evolution is by appealing to
the 18th-century philosopher William Paley's watchmaker analogy, which argues that certain natural phenomena are
analogical to a watch (in that they are ordered, or complex, or purposeful), which means that, like a watch, they must
have been designed by a "watchmaker"—an intelligent agent. This argument forms the core of intelligent design, a
neocreationist movement seeking to establish certain variants of the design argument as legitimate science, rather
than as philosophy or theology, and have them be taught alongside evolution.[28] [47]
This objection is fundamentally an argument by lack of imagination, or argument from incredulity: a certain
explanation is seen as being counter-intuitive, and therefore an alternate, more intuitive explanation is appealed to
instead. Supporters of evolution generally respond by arguing that evolution is not based on "chance", but on
predictable chemical interactions: natural processes, rather than supernatural beings, are the "designer". Although the
process involves some random elements, it is the non-random selection of survival-enhancing genes that drives
evolution along an ordered trajectory. The fact that the results are ordered and seem "designed" is no more evidence
for a supernatural intelligence than the appearance of complex natural phenomenon (e.g. snowflakes).[117] It is also
argued that there is insufficient evidence to make statements about the plausibility or implausibility of abiogenesis,
that certain structures demonstrate poor design, and that the implausibility of life evolving exactly as it did is no
more evidence for an intelligence than the implausibility of a deck of cards being shuffled and dealt in a certain
random order.[47] [114]
It has also been noted that arguments against some form of life arising "by chance" are really objections to
nontheistic abiogenesis, not to evolution. Indeed, arguments against "evolution" are based on the misconception that
abiogenesis is a component of, or necessary precursor to, evolution. Similar objections sometimes conflate the Big
Bang with evolution.[12]
Christian apologist and philosopher Alvin Plantinga, a supporter of intelligent design, has formalized and revised the
improbability argument as the evolutionary argument against naturalism, which asserts that it is irrational to reject a
supernatural, intelligent creator because the apparent probability of certain faculties evolving is so low. Specifically,
Plantinga claims that evolution cannot account for the rise of reliable reasoning faculties. Plantinga argues that
whereas a God would be expected to create beings with reliable reasoning faculties, evolution would be just as likely
to lead to unreliable ones, meaning that if evolution is true, it is irrational to trust whatever reasoning one relies on to
conclude that it is true.[118] This novel epistemological argument has been criticized similarly to other probabilistic
design arguments. It has also been argued that rationality, if conducive to survival, is more likely to be selected for
than irrationality, making the natural development of reliable cognitive faculties more likely than unreliable
ones.[119] [120]

Unexplained aspects of the natural world

It is frequently argued that a great weakness of evolutionary theory is that it does not, or cannot, explain a certain
aspect of the natural world. Although there is broad agreement that certain aspects of life remain unexplained,
creationists argue that evolution should be abandoned altogether because of the phenomena it does not explain. It is
argued that an alternative explanation, such as intelligent design, can explain the things which evolution cannot. For
example, Michael Behe has argued that current evolutionary theory cannot account for certain complex structures,
particularly in microbiology. On this basis, Behe argues that such structures were "purposely arranged by an
intelligent agent" (see argument from incredulity).[121]
In addition to complex structures and systems, among the phenomena that critics variously claim evolution cannot
explain are consciousness, free will, hominid intelligence, instincts, emotions, metamorphosis, photosynthesis,
homosexuality, music, language, religion, morality, and altruism (see altruism in animals).[122] Most of these, such
as homosexuality, hominid intelligence, instinct, emotion, photosynthesis, language, and altruism, have been
well-explained by evolution, while others remain mysterious, or only have preliminary explanations. However,
supporters of evolution contend that no alternative explanation has been able to adequately explain the biological
Objections to evolution 371

origin of these phenomena either.[123] [124]

Creationists argue against evolution on the grounds that it cannot explain certain non-evolutionary processes, such as
abiogenesis, the Big Bang, or the meaning of life. In such instances, evolution is being redefined to refer to the entire
history of the universe, and it is argued that if one aspect of the universe is seemingly inexplicable, the entire body of
scientific theories must be baseless. At this point, objections leave the arena of evolutionary biology and become
general scientific or philosophical disputes.[125]

Implausibility
This class of objections is more radical than the above, claiming that a major aspect of evolution is not merely
unscientific or implausible, but rather impossible, because it contradicts some other law of nature or is constrained in
such a way that it cannot produce the biological diversity of the world.

Creation of complex structures

"Living things have fantastically intricate features-at the
anatomical, cellular, and molecular levels-that could not
function if they were any less complicated or sophisticated. The
only prudent conclusion is that they are products of Intelligent
Design, not Evolution" - from Refuting Evolution 2, Jonathan
Sarfati[126]

Modern evolutionary theory posits that all biological systems must

have evolved incrementally, through a combination of natural selection
and genetic drift. Both Darwin and his early detractors recognized the
potential problems that could arise for his theory of natural selection if
the lineage of organs and other biological features could not be The bacterial flagellum is often invoked to
illustrate the concept of irreducible complexity.
accounted for by merely gradual, step-by-step changes over successive
Careful analysis shows that there are no major
generations; if all the intermediary stages between an initial organ and obstacles to a gradual evolution of flagella.
the organ it will become are not all improvements upon the original, it
will be impossible for the later organ to develop by the process of natural selection alone. Anticipating early
criticisms that the evolution of the eye and other complex organs seemed impossible, Darwin noted that:

[R]eason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and
simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever
so slightly, and the variations be inherited, which is certainly the case; and if any variation or
modification in the organ be ever useful to an animal under changing conditions of life, then the
difficulty of believing that a perfect and complex eye could be formed by natural selection, though
insuperable by our imagination, can hardly be considered real.[92]

Similarly, Richard Dawkins said on the topic of the evolution of the feather in an interview for the television
program The Atheism Tapes:
There's got to be a series of advantages all the way in the feather. If you can't think of one, then that's
your problem not natural selection's problem... It's perfectly possible feathers began as fluffy extensions
of reptilian scales to act as insulators... The earliest feathers might have been a different approach to
hairiness among reptiles keeping warm.
Creationist arguments have been made such as "What use is half an eye?" and "What use is half a wing?".[127]
Research has confirmed that the natural evolution of the eye and other intricate organs is entirely feasible.[128] [129]
Creationist claims have persisted that such complexity evolving without a designer is inconceivable, however, and
this objection to evolution has been refined in recent years as the more sophisticated irreducible complexity
Objections to evolution 372

argument of the intelligent design movement, formulated by biochemist Michael Behe.[28]

Irreducible complexity is the idea that certain biological systems cannot be broken down into their constituent parts
and remain functional, and therefore that they could not have evolved naturally from less complex or complete
systems. Whereas past arguments of this nature generally relied on macroscopic organs, Behe's primary examples of
irreducible complexity has been cellular and biochemical in nature. He has argued that the components of systems
such as the blood clotting cascade, the immune system, and the bacterial flagellum are so complex and
interdependent that they could not have evolved from simpler systems.[130]
"In fact, my argument for intelligent design is open to direct experimental rebuttal. Here is a thought
experiment that makes the point clear. In Darwin’s Black Box (Behe 1996) I claimed that the bacterial
flagellum was irreducibly complex and so required deliberate intelligent design. The flip side of this claim is
that the flagellum can’t be produced by natural selection acting on random mutation, or any other
unintelligent process. To falsify such a claim, a scientist could go into the laboratory, place a bacterial species
lacking a flagellum under some selective pressure (for mobility, say), grow it for ten thousand generations,
and see if a flagellum—or any equally complex system—was produced. If that happened, my claims would be
neatly disproven."-Michael Behe[131]
In the years since Behe proposed irreducible complexity, new developments and advances in biology, such as an
improved understanding of the evolution of flagella,[132] have already undermined these arguments.[133] [134] The
idea that seemingly irreducibly complex systems cannot evolve has been refuted through evolutionary mechanisms,
such as exaptation (the adaptation of organs for entirely new functions)[135] and the use of "scaffolding", which are
initially necessary features of a system that later degenerate when they are no longer required. Potential evolutionary
pathways have been provided for all of the systems Behe used as examples of irreducible complexity.[133] [136] [137]

Creation of information
Another new, and increasingly common, objection of creationists to evolution is that evolutionary mechanisms such
as mutation cannot generate new information. Creationists such as William A. Dembski, Werner Gitt, and Lee
Spetner have attempted to use information theory to dispute evolution. Dembski has argued that life demonstrates
specified complexity, and that evolution without an intelligent agent cannot account for the generation of
information that would be required to produce specified complexity. The Christian apologetics site Answers in
Genesis, for example, makes frequent appeals to concepts from information theory in its objections to evolution and
affirmations of the Genesis account of Creation; "[I]t should be clear that a rigorous application of the science of
information is devastating to materialistic philosophy in the guise of evolution, and strongly supportive of Genesis
creation."[138]
However, these claims have been widely rejected by the scientific community; new information is regularly
generated in evolution, whenever a novel mutation or gene duplication arises. Dramatic examples of entirely new,
unique traits arising through mutation have been observed in recent years, such as the evolution of nylon-eating
bacteria, which developed new enzymes to efficiently digest a material that never existed before the modern era.[139]
[140]
In fact, when an organism is considered together with the environment it evolved in, there is no need to account
for the creation of information. The information in the genome forms a record of how it was possible to survive in a
particular environment. It is not created, but rather gathered from the environment through research—by trial and
error, as mutating organisms either reproduce or fail.[141]
A related argument against evolution is that most mutations are harmful.[142] However, in reality the vast majority of
mutations are neutral, and the minority of mutations which are beneficial or harmful are often situational; a mutation
that is harmful in one environment may be helpful in another.[143]
Objections to evolution 373

Violation of the second law of thermodynamics

Another objection is that evolution violates the second law of thermodynamics. Though the law applies to all
systems, in the case of a closed one it states, "the entropy of an isolated system not in equilibrium will tend to
increase over time, approaching a maximum value at equilibrium". In other words, an ideal isolated system's entropy
(a measure of the dispersal of energy in a physical system so that it is not available to do mechanical work) will tend
to increase or stay the same, not decrease. Creationists argue that evolution violates this physical law by requiring a
decrease in entropy, or disorder, over time.[144]
However, this claim is based on a manifestation of the law only applicable to isolated systems, which do not
exchange matter or energy with their surroundings. Organisms, in contrast, are open systems, as they constantly
exchange energy and matter with their environment: for example animals eat food and excrete waste, and radiate and
absorb heat. Similarly, the Earth absorbs energy from the Sun and emits energy back into space. The
Sun-Earth-space system does not violate the second law, because the enormous increase in entropy due to the Sun
and Earth radiating into space dwarfs the local decrease in entropy caused by the existence and evolution of
self-organizing life.[39] [145]
Since the second law of thermodynamics has a precise mathematical definition, this argument can be analyzed
quantitatively.[146] [147] This was done by physicist Daniel Styer, who concluded: "Quantitative estimates of the
entropy involved in biological evolution demonstrate that there is no conflict between evolution and the second law
of thermodynamics."[146]
In a published letter to the editor of The Mathematical Intelligencer titled "How anti-evolutionists abuse
mathematics", mathematician Jason Rosenhouse stated:
The fact is that natural forces routinely lead to decreases in entropy. Water freezes into ice and fertilised
eggs turn into babies. Plants use sunlight to convert carbon dioxide and water into sugar and oxygen, but
[we do] not invoke divine intervention to explain the process [...] thermodynamics offers nothing to
dampen our confidence in Darwinism.[148]
Objections to evolution 374

Moral implications
Other common objections to evolution allege that evolution leads to objectionable results, including bad beliefs,
behaviors, and events. It is argued that the teaching of evolution degrades values, undermines morals, and fosters
irreligion or atheism. These may be considered appeals to consequences (a form of logical fallacy), as the potential
ramifications of belief in evolutionary theory have nothing to do with its objective empirical reality.

Humans as animals
Even though biology has long shown that humans are animals,
some people feel that humans should be considered separate
from, and/or superior to, animals. The mediaeval concept of a
great chain of being set out a static hierarchy in which humans
are "above" animals, but below angels and God. As
evolutionary thought developed it was feared that evolution
implied that there was no real separation between man and
brute, and that it undermined human social hierarchy.
Assertions of ape ancestry in the 1844 publication Vestiges of
Creation gained much public acceptance but were scornfully
attacked by establishment scientists, and though Darwin 1871 caricature of Charles
avoided the subject when announcing his theory in On the Darwin as an ape, accompanied
Origin of Species in 1859, the issue was quickly raised. by a satirical disclaimer claiming
a fait accompli for its
Anatomists claimed that humans had unique physical features; [149]
inclusion
however, English biologist Thomas Henry Huxley showed
that they were wrong and overcame their opposition to
Darwin's ideas. Evolutionary common descent does not imply
that human beings should behave like other animals, but
instead shows that animals behave in different ways, and
teaches that humans behave like humans.[150]

Traditionalists still object to the idea that diversity in life,

including human beings, arose through natural processes
without a need for supernatural intervention, and they argue
against evolution on the basis that it contradicts their literal
Huxley's book Man's Place in Nature was the first devoted to
interpretation of creation myths about separate "kinds".
human evolution and an early example of comparative
However, most religions, such as Catholicism, have biology.
reconciled their beliefs with evolution through theistic
evolution.[151] [152]

Social effects
Some Creationists claim that perceived social ills like crime, teen pregnancies, homosexuality, abortion, immorality,
wars and genocide are caused by a belief in evolution.[153] R. Albert Mohler, Jr., President of Southern Baptist
Theological Seminary in Louisville, Kentucky, wrote August 8, 2005, in National Public Radio's forum, "Taking
Issue", that "Debates over education, abortion, environmentalism, homosexuality and a host of other issues are really
debates about the origin—and thus the meaning—of human life.... Evolutionary theory stands at the base of moral
relativism and the rejection of traditional morality".[154] [155] Creationist Ken Ham likens evolution to a horde of

termites, weakening society's foundation. In Why Won't They Listen?, Ham suggests that "evolutionary termites" are
responsible for pornography, homosexual behavior and lawlessness. He also writes, "I'm not saying that evolution is
Objections to evolution 375

the cause of abortion or school violence. What I'm saying is that the more a culture abandons God's word as the
absolute authority, and the more a culture accepts an evolutionary philosophy, then the way people think, and their
attitudes, will also change."[156]
Former Texas Republican Representative Tom DeLay claimed that the Columbine school shootings were caused by
the teaching of evolution. DeLay is quoted as stating that "Our school systems teach the children that they are
nothing but glorified apes who are evolutionized [sic] out of some primordial soup."[157] Henry M. Morris,
engineering professor and founder of the Creation Research Society and the Institute of Creation Research, claims
that evolution was part of a pagan religion that emerged after the Tower of Babel, was part of Plato's and Aristotle's
philosophies, and was responsible for everything from war to pornography to the breakup of the nuclear family.[158]
Rev. D. James Kennedy of The Center for Reclaiming America for Christ and Coral Ridge Ministries claims that
Darwin was responsible for Adolf Hitler's atrocities. In D. James Kennedy's documentary, and the accompanying
pamphlet with the same title, Darwin’s Deadly Legacy, Kennedy states that "To put it simply, no Darwin, no Hitler."
In his efforts to expose the "harmful effects that evolution is still having on our nation, our children, and our world",
Kennedy also states that, "We have had 150 years of the theory of Darwinian evolution, and what has it brought us?
Whether Darwin intended it or not, millions of deaths, the destruction of those deemed inferior, the devaluing of
human life, increasing hopelessness."[159] [160] [161] Discovery Institute fellow Richard Weikart has made similar
claims,[162] [163] as have other creationists.[164] The claim was central to Ben Stein's film Expelled: No Intelligence
Allowed promoting intelligent design creationism. The Anti-Defamation League describes such claims as outrageous
misuse of the the Holocaust and its imagery, and as trivializing "the many complex factors that led to the mass
extermination of European Jewry. Hitler did not need Darwin or evolution to devise his heinous plan to exterminate
the Jewish people, and Darwin and evolutionary theory cannot explain Hitler’s genocidal madness. Moreover,
anti-Semitism existed long before Darwin ever wrote a word."[161] [165]
Kent Hovind of Creation Science Evangelism blames communism, socialism, World War I, World War II, racism,
the Holocaust, Stalin's war crimes, the Vietnam War and Pol Pot's Cambodian killing fields on evolution, as well as
the increase in crime, unwed mothers, and other social ills.[82] Kent Hovind's son Eric Hovind has now taken over
the family business while his father is in prison, and claims that evolution is responsible for tattoos, body piercing,
premarital sex, unwed births, sexually transmitted diseases (STDs), divorce and child abuse.[166]
Supporters of evolution dismiss such criticisms as counterfactual, and some argue that the opposite seems to be the
case. A study published by the author and illustrator Gregory S. Paul found that religious beliefs, including belief in
creationism and disbelief in evolution, are positively correlated with social ills like crime.[167] The Barna Group
surveys find that Christians and non-Christians in the US have similar divorce rates, and the highest divorce rates in
the US are among Baptists and Pentecostals, both sects which reject evolution and embrace creationism.[168]
Michael Shermer argued in Scientific American in October 2006 that evolution supports concepts like family values,
avoiding lies, fidelity, moral codes and the rule of law.[169] He goes on to suggest that evolution gives more support
to the notion of an omnipotent creator, rather than a tinkerer with limitations based on a human model, the more
common image subscribed to by creationists. Careful analyses of the creationist charges that evolution has led to
moral relativism and the Holocaust yields the conclusion that these charges appear to be highly suspect.[170] Such
analyses conclude that the origins of the Holocaust are more likely to be found in historical Christian anti-semitism
than in evolution.[171] [172]
Evolution has been used to justify Social Darwinism, the exploitation of "lesser breeds without the law" by "superior
races," particularly in the nineteenth century.[173] Strong, typically European, nations successfully expanded their
empires, and as such, these strong nations could be said to have "survived" in the struggle for dominance.[173] With
this attitude, Europeans, with the exception of Christian missionaries, seldom adopted the customs and languages of
local people under their empires.[173]
Objections to evolution 376

Atheism
Another charge leveled at evolutionary theory by creationists is that belief in evolution is either tantamount to
atheism, or conducive to atheism.[174] It is commonly claimed that all proponents of evolutionary theory are
"materialistic atheists".[175] On the other hand, Davis Young argues that Creation Science itself is harmful to
Christianity because its bad science will turn more away than it recruits. Young asks, "Can we seriously expect
non-Christians to develop a respect for Christianity if we insist on teaching the brand of science that creationism
brings with it?"[176] However, evolution neither requires nor rules out the existence of a supernatural being.
Philosopher Robert Pennock makes the comparison that evolution is no more atheistic than plumbing.[177] H. Allen
Orr, professor of biology at University of Rochester, notes that:
Of the five founding fathers of twentieth-century evolutionary biology — Ronald Fisher, Sewall Wright, J. B.
S. Haldane, Ernst Mayr, and Theodosius Dobzhansky — one was a devout Anglican who preached sermons
and published articles in church magazines, one a practicing Unitarian, one a dabbler in Eastern mysticism,
one an apparent atheist, and one a member of the Russian Orthodox Church and the author of a book on
religion and science.[178]
In addition, a wide range of religions have reconciled a belief in a supernatural being with evolution.[179] Molleen
Matsumura of the National Center for Science Education found that "of Americans in the twelve largest Christian
denominations, 89.6% belong to churches that support evolution education". These churches include the United
Methodist Church, National Baptist Convention USA, Evangelical Lutheran Church in America, Presbyterian
Church (USA), National Baptist Convention of America, African Methodist Episcopal Church, the Roman Catholic
Church, the Episcopal Church, and others.[180] A poll in 2000 done for People for the American Way found that 70%
of the American public felt that evolution was compatible with a belief in God. Only 48% of the people polled could
choose the correct definition of evolution from a list, however.[181]
One poll reported in the journal Nature showed that among American scientists (across various disciplines), about 40
percent believe in both evolution and an active deity (theistic evolution).[182] This is similar to the results reported
for surveys of the general American public. Also, about 40 percent of the scientists polled believe in a God that
answers prayers, and believe in immortality.[183] While about 55% of scientists surveyed were atheists, agnostics, or
nonreligious theists, atheism is far from universal among scientists who support evolution, or among the general
public that supports evolution. Very similar results were reported from a 1997 Gallup survey of the American public
and scientists.[184]

[184] Belief in Young Earth Belief in God-guided Belief in evolution without God guiding the
Group
Creationism evolution process

American public 44% 39% 10%

American 5% 40% 55%

scientists
Objections to evolution 377

See also
• Faith and rationality

Notes
[1] Johnston, Ian C. (1999). "Section Three: The Origins of Evolutionary Theory" (http:/ / records. viu. ca/ ~johnstoi/ darwin/ title. htm). ... And
Still We Evolve. Liberal Studies Department, Malaspina University College. . Retrieved 2007-07-25.
[2] van Wyhe, John (2002-7). "Charles Darwin: gentleman naturalist: A biographical sketch" (http:/ / darwin-online. org. uk/ darwin. html). The
Complete Work of Charles Darwin Online. University of Cambridge. . Retrieved 2007-07-25.
[3] IAP Statement on the Teaching of Evolution (http:/ / www. interacademies. net/ Object. File/ Master/ 6/ 150/ Evolution statement. pdf),
Interacademy Panel
[4] In his comprehensive treatise on Creationism, The Creationists, historian Ronald Numbers traces the religious motivations and scientific
pretensions, of prominent creationists from George Frederick Wright through George McCready Price, Harry Rimmer, John C. Whitcomb,
Henry M. Morris and his Institute for Creation Research (and lesser figures) to Phillip E. Johnson and the Intelligent design movement.
Numbers, Ronald (November 30, 2006). The Creationists: From Scientific Creationism to Intelligent Design, Expanded Edition. Harvard
University Press. p. 624 pages. ISBN 0674023390.
[5] Godfrey, Laurie R. Scientists Confront Creationism. Pg 8. W. W. Norton & Company (1984). ISBN 0-393-30154-0.
[6] Sarfati, Jonathan & Matthews, Michael (2000). Argument: Creationism is religion, not science (http:/ / www. answersingenesis. org/
get-answers/ topic/ religion). Answers in Genesis.
[7] "Statement on the Teaching of Evolution" (http:/ / www. aaas. org/ news/ releases/ 2006/ pdf/ 0219boardstatement. pdf) (PDF). American
Association for the Advancement of Science. 2006. . Retrieved 2007-03-20.
[8] Abdul Majid (2002). "The Muslim Responses To Evolution" (http:/ / diberri. dyndns. org/ cgi-bin/ templatefiller/ ?type=& id=) (html).
Islamic Research Foundation International, Inc.. . Retrieved 2010-05-24.
[9] "Worldwide creationism, Shotgun stunner, and more" (http:/ / www. newscientist. com/ article/ mg20327153.
900-worldwide-creationism-shotgun-stunner-and-more. html) (html). New Scientist. . Retrieved 2010-05-24.
[10] "About Us" (http:/ / creation. com/ about-us#who_we_are) (html). . Retrieved 2010-05-24.
[11] "Opinions on evolution from ten countries | NCSE" (http:/ / ncse. com/ news/ 2009/ 07/ opinions-evolution-from-ten-countries-004885)
(html). National Center for Science Education. . Retrieved 2010-06-14.
[12] Moran, Laurence (1993). "What is Evolution?" (http:/ / www. talkorigins. org/ faqs/ evolution-definition. html). The TalkOrigins Archive
(http:/ / www. talkorigins. org). . Retrieved 2007-03-24.
[13] "Ask the experts:Biology-Is the human race evolving or devolving?" (http:/ / www. scientificamerican. com/ article.
cfm?id=is-the-human-race-evolvin). Scientific American. 1998. . Retrieved 2007-03-24.
[14] Carroll SB (2001). "Chance and necessity: the evolution of morphological complexity and diversity". Nature 409 (6823): 1102–9.
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[15] "CA212: Definition of evolution" (http:/ / www. talkorigins. org/ indexcc/ CA/ CA212. html) (HTML). talkorigins.org. . Retrieved
2010-06-07.
[16] Doolan, Robert (1996). "Oh! My aching wisdom teeth!" (http:/ / www. answersingenesis. org/ creation/ v18/ i3/ wisdom_teeth. asp).
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[17] AboutDarwin.com (http:/ / www. aboutdarwin. com/ timeline/ November. html)
[18] England, P.; Molnar, P.; Righter, F. (January 2007). "John Perry's neglected critique of Kelvin's age for the Earth: A missed opportunity in
geodynamics". GSA Today 17 (1): 4–9. doi:10.1130/GSAT01701A.1.
[19] Boltwood, B. B. (1907). "On the ultimate disintegration products of the radio-active elements. Part II. The disintegration products of
uranium". American Journal of Science 23: 77–88.
[20] Bowler, Peter J. (1983). The eclipse of Darwinism: anti-Darwinian evolution theories in the decades around 1900 (paperback ed.).
Baltimore: Johns Hopkins University Press. pp. 23–24. ISBN 0-8018-4391-X.
[21] Bowler, PJ (2003). Evolution: The History of an Idea, Third Edition, Completely Revised and Expanded. University of California Press.
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[22] Moore, James R. (1981). The Post-Darwinian Controversies: A Study of the Protestant Struggle to Come to Terms with Darwin in Great
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[23] The Relations Between Religion and Science by Frederick Temple (http:/ / www. gutenberg. org/ files/ 17194/ 17194-h/ 17194-h.
htm#LECTURE_IV) Lecture IV of Eight Lectures Preached Before the University of Oxford in 1884
[24] Pius XII, encyclical Humani Generis (http:/ / www. vatican. va/ holy_father/ pius_xii/ encyclicals/ documents/
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[113] Isaak, M (2004). "Index to Creationist Claims, CC201: Phyletic gradualism" (http:/ / www. talkorigins. org/ indexcc/ CC/ CC201. html).
The TalkOrigins Archive (http:/ / www. talkorigins. org). . Retrieved 2008-07-13.
[114] Wilkins, J (1997). "Evolution and Chance" (http:/ / www. talkorigins. org/ faqs/ chance/ chance. html). The TalkOrigins Archive (http:/ /
www. talkorigins. org). . Retrieved 2007-03-24.
[115] Battern, D (1995). "Cheating with chance" (http:/ / creation. com/ cheating-with-chance). Answers in Genesis. . Retrieved 2009-12-06.
[116] Lies, Damned Lies, Statistics, and Probability of Abiogenesis Calculations (http:/ / www. talkorigins. org/ faqs/ abioprob/ abioprob. html)
[117] "CI100: Intelligent Design" (http:/ / www. talkorigins. org/ indexcc/ CI/ CI100. html). .
[118] Plantinga, A (1993). Warrant and Proper Function. Oxford University Press. doi:10.1093/0195078640.001.0001. ISBN 0-19-507864-0.
[119] Fitelson, B; Sober, E (1997). "Plantinga's Probability Arguments Against Evolutionary Naturalism" (http:/ / fitelson. org/ plant. pdf) (PDF).
. Retrieved 2007-03-24.
[120] Isaak, M (2005). "Index to Creationist Claims, Claim CA120: Mind's fallibility" (http:/ / www. talkorigins. org/ indexcc/ CA/ CA120.
html). The TalkOrigins Archive (http:/ / www. talkorigins. org). . Retrieved 2007-03-24.
[121] Behe, MJ (1996-10-29). "Darwin under the microscope" (http:/ / www. arn. org/ docs/ behe/ mb_dm11496. htm). New York Times. p. 25. .
Retrieved 2007-03-24.
[122] Johnson, P (1990). "Evolution as dogma: The establishment of naturalism" (http:/ / www. arn. org/ docs/ johnson/ pjdogma1. htm). .
Retrieved 2007-03-24.
[123] "CB401: Inconceivable instinct" (http:/ / www. talkorigins. org/ indexcc/ CB/ CB401. html). . Retrieved 2009-12-05.
[124] "CB400: Evolution of consciousness" (http:/ / www. talkorigins. org/ indexcc/ CB/ CB400. html). . Retrieved 2009-12-05.
Objections to evolution 381

[125] Isaak, M (2004). "Index to Creationist Claims, Claim CE440: The origin of it all" (http:/ / www. talkorigins. org/ indexcc/ CE/ CE440.
html). theTalkOrigins Archive (http:/ / www. talkorigins. org). . Retrieved 2007-03-24.
[126] Jonathan Sarfati, Ph.D; 2003 Refuting Evolution 2. Master Books ISBN 0-89051-387-2
[127] "CB921.2: Half a wing" (http:/ / www. talkorigins. org/ indexcc/ CB/ CB921_2. html) (HTML). talkorigins.org. . Retrieved 2010-06-07.
[128] Gehring, W.J. (2005). "New Perspectives on Eye Development and the Evolution of Eyes and Photoreceptors". Journal of Heredity 96 (3):
171–184. doi:10.1093/jhered/esi027. PMID 15653558.
[129] "Eyes, Part One: Opening Up the Russian Doll. The Loom: A blog about life, past and future" (http:/ / www. corante. com/ loom/ archives/
2005/ 02/ 15/ eyes_part_one_opening_up_the_russian_doll. php). . Retrieved 2007-09-22.
[130] Behe, MJ (1996). Darwin's Black Box: The Biochemical Challenge to Evolution. Free Press. ISBN 978-0743290319.
[131] Behe, Michael (2000-07-31). "Philosophical Objections to Intelligent Design: Response to Critics" (http:/ / www. arn. org/ docs/ behe/
mb_philosophicalobjectionsresponse. htm). . Retrieved 2010-01-02.
[132] Liu, R.Y.; Ochman, H. (2007). "Stepwise formation of the bacterial flagellar system" (http:/ / www. pubmedcentral. nih. gov/ articlerender.
fcgi?tool=pmcentrez& artid=1852327). PNAS 104 (17): 7116–7121. doi:10.1073/pnas.0700266104. PMID 17438286. PMC 1852327.
[133] Isaak, M (2005). "Index to Creationist Claims, Claim CB200: Irreducible complexity" (http:/ / www. talkorigins. org/ indexcc/ CB/ CB200.
html). The TalkOrigins Archive (http:/ / www. talkorigins. org). . Retrieved 2007-03-24.; and references therein
[134] Ussery, D. (1999). "A biochemist's response to "The biochemical challenge to evolution"" (http:/ / www. cbs. dtu. dk/ staff/ dave/ Behe.
html). Bios 70: 40–45. .
[135] Aharoni, A.; Gaidukov, L.; Khersonsky, O.; Gould, S.M.; Roodveldt, C; Tawfik, D.S. (2005). "The 'evolvability' of promiscuous protein
functions". Nature Genetics 37 (1): 73–76. doi:10.1038/ng1482. PMID 15568024.
[136] Robison, K (1996). "Darwin's Black Box: Irreducible Complexity or Irreproducible Irreducibility?" (http:/ / www. talkorigins. org/ faqs/
behe/ review. html). The TalkOrigins Archive (http:/ / www. talkorigins. org). . Retrieved 2007-03-24.
[137] Sanz, V.C. (2009). "Darwin's golden flame. Responses of biochemistry to intelligent design". Teorema 28: 173–188.
[138] Gitt, Werner (1996). Information, science and biology (http:/ / www. answersingenesis. org/ tj/ v10/ i2/ information. asp). Answers in
Genesis.
[139] Musgrave, I; Baldwin, R, et al. (2005). "Information Theory and Creationism" (http:/ / www. talkorigins. org/ faqs/ information/
infotheory. html). The TalkOrigins Archive (http:/ / www. talkorigins. org). . Retrieved 2007-03-24.
[140] Thomas, D. "Evolution and Information: The Nylon Bug" (http:/ / www. nmsr. org/ nylon. htm). New Mexicans for Science and Reason. .
Retrieved 2007-03-24.
[141] Bergstrom, CT; Lachmann, M (2006). "The fitness value of information" (http:/ / arxiv. org/ pdf/ q-bio. PE/ 0510007). . Retrieved
2007-03-24.
[142] "CB101: Most mutations harmful?" (http:/ / www. talkorigins. org/ indexcc/ CB/ CB101. html) (html). talkorigins.org. . Retrieved
2010-05-30.
[143] Harter, R (1999). "Are Mutations Harmful?" (http:/ / www. talkorigins. org/ faqs/ mutations. html). The TalkOrigins Archive (http:/ / www.
talkorigins. org). . Retrieved 2007-03-24.
[144] Lambert, F (2002). "Disorder — A Cracked Crutch For Supporting Entropy Discussions" (http:/ / www. entropysite. com/ cracked_crutch.
html). Journal of Chemical Education 79: 187–192. doi:10.1021/ed079p187. . Retrieved 2007-03-24.
[145] Oerter, RN (2006). "Does Life On Earth Violate the Second Law of Thermodynamics?" (http:/ / physics. gmu. edu/ ~roerter/
EvolutionEntropy. htm). . Retrieved 2007-03-24.
[146] Daniel F. Styer, "Entropy and evolution," American Journal of Physics, Vol. 76, No. 11, November 2008, p. 1031
[147] Emory F. Bunn, "Evolution and the Second Lqw of Thermodynamics," American Journal of Physics, Vol. 77, No. 10, October 2009, p. 922
[148] Rosenhouse, J (2001). "How Anti-Evolutionists Abuse Mathematics" (http:/ / www. math. jmu. edu/ ~rosenhjd/ sewell. pdf) (PDF). The
Mathematical Intelligencer 23 (4): 3–8. . Retrieved 2007-03-26.
[149] A venerable Orang-utang (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=image& itemID=CUL-DAR141. 5& pageseq=1) "I
have to apologize once more for the wild flights of my incorrigible artist. I told him most clearly and positively to draw me a life-like portrait
of that profound philosopher, Mr. Darwin..." – The Hornet, 1871, from the collection of Darwin Online
[150] Isaak, M (2004). "Claim CA009: Evolution teaches that people are animals. We should not be surprised when people who are taught
evolution start behaving like animals" (http:/ / www. talkorigins. org/ indexcc/ CA/ CA009. html). The TalkOrigins Archive (http:/ / www.
talkorigins. org). . Retrieved 2007-03-24.
[151] Churches urged to challenge Intelligent Design (http:/ / www. ekklesia. co. uk/ content/ news_syndication/ article_060220creationism.
shtml)
[152] Pope John Paul II, "Truth Cannot Contradict Truth", New Advent, ed. Kevin Knight, 2009-Feb-15
<http://www.newadvent.org/library/docs_jp02tc.htm>
[153] Morris, H (1982). The Troubled Waters of Evolution. Master Books. ISBN 978-0890510872.
[154] Mohler, RA (2005). "The Origins of Life: An Evangelical Baptist View" (http:/ / www. npr. org/ templates/ story/ story.
php?storyId=4760816). NPR (http:/ / www. npr. org). . Retrieved 2007-03-24.
[155] "The Result of Believing Evolution" (http:/ / www. lwbc. co. uk/ Genesis/ results of believing evolution. htm). Living Word Bible Church
(http:/ / www. lwbc. co. uk/ index. htm). . Retrieved 2007-03-24.
[156] Ham, K (2002). Why Won't They Listen? A Radical New Approach to Evangelism (http:/ / www. answersingenesis. org/ home/ area/
WWTL/ index. asp). Master Books. ISBN 0890513783. .
Objections to evolution 382

[157] Raymo, C (1999-09-06). "Darwin's Dangerous De-evolution" (http:/ / www. boston. com/ globe/ search/ stories/ reprints/ darwin100199.
htm). Boston Globe. . Retrieved 2007-03-24.
[158] Morris, HM (1989). The Long War Against God: The History and Impact of the Creation/Evolution Conflict. Baker Book House.
ISBN 0-89051-291-4.
[159] "Kennedy: Evolution to Blame for Death, Hopelessness in World" (http:/ / www. rightwingwatch. org/ 2006/ 08/ kennedy_evoluti. html).
Right Wing Watch. . Retrieved 2007-03-24.
[160] Martin, A; Parker, J (2006). "TV Producer Defends Documentary Exposing Darwin-Hitler Link" (http:/ / headlines. agapepress. org/
archive/ 8/ 252006b. asp). Agape Press (http:/ / headlines. agapepress. org). . Retrieved 2007-03-24.
[161] "ADL Blasts Christian Supremacist TV Special & Book Blaming Darwin For Hitler" (http:/ / www. adl. org/ PresRele/ HolNa_52/
4877_52. htm). Anti-Defamation League. August 22, 2006. . Retrieved 2009-12-07.
[162] Weikart, R (2004). From Darwin to Hitler: Evolutionary Ethics, Eugenics, and Racism in Germany. Palgrave Macmillan.
ISBN 978-1403972019.
[163] From Darwin to Hitler: A Pathway to Horror (Updated) (http:/ / www. evolutionnews. org/ 2006/ 12/ from_darwin_to_hitler_a_straig.
html#more), Jonathan Witt, Evolution News and Views, Discovery Institute, December 15, 2006.
[164] This creationist claim that is part of a Discovery Institute campaign ( New book by Discovery Institute Fellow shows influence of
Darwinian principles on Hitler's Nazi regime (http:/ / www. darwintohitler. com/ ), Discovery Institute) and is amply repeated in creationist
literature. For example:
• Darwinism and the Nazi race Holocaust (http:/ / www. answersingenesis. org/ tj/ v13/ i2/ nazi. asp), Jerry Bergman, CEN Technical
Journal, 13(2):101–111, 1999.
• The Holocaust and evolution (http:/ / creation. com/ the-holocaust-and-evolution), Jonathan Sarfati, Creation 22(1):4, December 1999.
• From Darwin to Hitler: Evolutionary Ethics, Eugenics, and Racism in Germany (http:/ / web. csustan. edu/ History/ Faculty/ Weikart/
FromDarwintoHitler. htm), Richard Weikart, Palgrave MacMillan, 2004.
[165] "Anti-Evolution Film Misappropriates the Holocaust" (http:/ / www. adl. org/ PresRele/ HolNa_52/ 5277_52. htm). Anti-Defamation
League. April 29, 2008. . Retrieved 2009-12-07.
"Intelligent Design: It's Not Science – Religious Freedom Resources" (http:/ / www. adl. org/ religious_freedom/ resource_kit/
intelligent_design. asp). Anti-Defamation League. 2009. . Retrieved 2009-12-07.
[166] Creationist Links Origins to Faith, Everyday Life: Says outlook on Genesis account affects every aspect of life (http:/ / www. dakotavoice.
com/ 200605/ 20060507_1. html), Bob Ellis, Dakota Voice, 5/7/2006
[167] Paul, GS (2005). "Cross-National Correlations of Quantifiable Societal Health with Popular Religiosity and Secularism in the Prosperous
Democracies: A First Look" (http:/ / moses. creighton. edu/ JRS/ 2005/ 2005-11. html). Journal of Religion & Society 7. . Retrieved
2007-03-24.
The paper was criticized by Moreno-Riaño, Smith, and Mach in a published article in the same journal (http:/ / moses. creighton. edu/ JRS/
2006/ 2006-1. html) because "[Paul's] methodological problems do not allow for any conclusive statement to be advanced regarding the
various hypotheses Paul seeks to demonstrate or falsify." Of course, correlation does not imply causality, and Paul does not produce any
speculations about the cause of these correlations.
[168] "Born Again Christians Just As Likely to Divorce As Are Non-Christians" (http:/ / www. barna. org/ barna-update/ article/ 5-barna-update/
194-born-again-christians-just-as-likely-to-divorce-as-are-non-christians). The Barna Group (http:/ / www. barna. org). 2004. . Retrieved
2004-03-24.
[169] Shermer, M (2006). "Darwin on the Right: Why Christians and conservatives should accept evolution" (http:/ / www. sciam. com/ article.
cfm?chanID=sa006& articleID=00068F43-E189-150E-A18983414B7F0000& colID=13). Scientific American. . Retrieved 2007-04-26.
[170] Darwin and Hitler: a not-very-intelligent link (http:/ / pqasb. pqarchiver. com/ tallahassee/ access/ 1715211751. html?FMT=ABS&
amp;date=Feb+ 06,+ 2008), Michael Ruse, My View, Tallahassee Democrat, February 6, 2008
[171] Talkorigins Claim CA006.1: Adolf Hitler exploited the racist ideas of Darwinism to justify genocide (http:/ / www. talkorigins. org/
indexcc/ CA/ CA006_1. html), Mark Isaak, Index to Creationist Claims, Talkorigins, created 2001-4-29, modified 2005-7-1, © 2006
[172] Creationists for Genocide (http:/ / www. talkreason. org/ articles/ Genocide. cfm), Hector Avalos, Talkreason
[173] "Western Civilization: Ideas, Politics, and Society" (http:/ / books. google. com/ books?id=kKGgoNo4un0C& pg=PA653& lpg=PA653).
Houghton Mifflin Harcourt Publishing Company. . Retrieved 2007–03–25. "The most extreme ideological expression of nationalism and
imperialism was Social Darwinism. In the popular mind, the concepts of evolution justified the exploitation of "lesser breeds without the law"
by superior races. This language of race and conflict, of superior and inferior people, had wide currency in the Western states. Social
Darwinists vigorously advocated the acquisition of empires, saying that strong nations-by definition, those that were successful at expanding
industry and empire-would survive and that others would not. To these elitists, all white men were more fit than non-whites to prevail in the
struggle for dominance. Even among Europeans, some nations were deemed more fit than others for the competition. Usually, Social
Darwinists thought their own nation the best, an attitude that sparked their competitive enthusiasm. In the nineteenth century, in contrast to the
seventeenth and eighteenth centuries, Europeans, except for missionaries, rarely adopted the customs or learned the languages of local people.
They had little sense that other cultures and other people had merit or deserved respect. Many westerners believed that it was their duty as
Christians to set an example and to educate others. Missionaries were the first to meet and learn about many peoples and were the first to
develop writing for those without a written language. Christian missionaries were ardently opposed to slavery."
[174] Strobel, Lee (2004). The Case for a Creator. Zondervan. p. 32. ISBN 0310241448. "In my quest to determine if contemporary science
points toward or away from God, I knew I had to first examine the claims of evolution in order to conclude once and for all whether
Objections to evolution 383

Darwinism creates a reasonable foundation for atheism. That's because if the materialism of Darwinian evolution is a fact, then the atheist
conclusions I reached as a student might still be valid."
[175] Johnson, Phillip (1999). "The Church of Darwin" (http:/ / www. arn. org/ docs/ johnson/ chofdarwin. htm). Wall Street Journal. . Retrieved
2010-05-23.
[176] Young, D (1988). Christianity and the Age of the Earth. Artisan Publishers. ISBN 093466627X.
[177] Pennock, RT (2000). Tower of Babel: The Evidence Against the New Creationism (http:/ / ncse. com/ store/ title/ tower-babel). MIT Press.
ISBN 978-0262661652. . Retrieved 2007-03-24.
[178] Devolution: Why intelligent design isn’t (http:/ / www. newyorker. com/ archive/ 2005/ 05/ 30/ 050530fa_fact?currentPage=1), H. Allen
Orr, Annals of Science, The New Yorker, May 30, 2005.
[179] "Statements from Religious Organizations" (http:/ / ncse. com/ media/ voices/ religion). National Center for Science Education. 2002. .
Retrieved 2007-03-24.
[180] Schrock, JR (2005-05-17). "Christianity, Evolution Not in Conflict" (http:/ / www. emporia. edu/ biosci/ schrock/ docs/ Eagle-25. pdf)
(PDF). Wichita Eagle. pp. 17A. . Retrieved 2007-03-24.
[181] "Evolution and Creationism In Public Education: An In-depth Reading Of Public Opinion" (http:/ / docs. google. com/ viewer?a=v&
q=cache:UDwdl6q3IgwJ:67. 192. 238. 59/ multimedia/ pdf/ Reports/ evolutionandcreationisminpubliceducation. pdf+
evolutionandcreationisminpubliceducation. pdf& hl=en& gl=ca& pid=bl&
srcid=ADGEESj-27vCwtszKiottg8mjbOKovsUvtJqRXXlLit-R3VitD5tlX4OfMPkfEEzNwQjvUSioQSua6y3LN1SR72877bW3dc6wFzFlG2pFdWl-21CVU68FW
sig=AHIEtbQjqyUehD_pbin4wiuZlHKkn--pTA) (PDF). People for the American Way. 2002. . Retrieved 2007-03-24.
[182] Larson, EJ; Witham, L (1997). "Scientists are still keeping the faith". Nature 386: 435–436. doi:10.1038/386435a0.
[183] Witham, L (1997). "Many scientists see God's hand in evolution" (http:/ / ncse. com/ rncse/ 17/ 6/
many-scientists-see-gods-hand-evolution). Reports of the National Center for Science Education 17 (6): 33. . Retrieved 2007-03-24.
[184] Robinson, BA (1995). "Public beliefs about evolution and creation" (http:/ / www. religioustolerance. org/ ev_publi. htm). . Retrieved
2007-03-24.

Further reading
• Philip Kitcher 1982 Abusing Science: The Case Against Creationism. Cambridge: The MIT Press
• Jonathan Sarfati, Ph.D; 2003 Refuting Evolution 2. Master Books ISBN 0-89051-387-2
• Coleman, Simon; Leslie Carlin (2004). The Cultures of Creationism: Antievolution in English-speaking
Countries. Burlington, Vermont: Ashgate. p. 195. ISBN 075460912X.
• Isaak, Mark (2005). The Counter-Creationism Handbook. Westport, Connecticut: Greenwood Press. p. 330.
ISBN 031333305X.
• Rennie J (July 2002). "15 answers to creationist nonsense" (http://www.swarthmore.edu/NatSci/cpurrin1/
textbookdisclaimers/wackononsense.pdf) (PDF). Sci. Am. 287 (1): 78–85.
doi:10.1038/scientificamerican0702-78. PMID 12085506.
Creationism 384

Creationism
"Creationism" can also refer to creation myths, or to a concept about the origin of the soul. For the movement
in Spanish literature, see Creacionismo.
Creationism is the religious belief[1] that humanity, life, the Earth, and the universe are the creation of a
supernatural being. However, the term is more commonly used to refer to religiously motivated rejection of certain
biological processes, in particular much of evolution, as an explanation accounting for the history, diversity, and
complexity of life on earth.[2] As science developed from the 18th century onwards, various views developed which
aimed to reconcile science with the Genesis creation narrative.[3] At this time those holding that species had been
separately created were generally called "advocates of creation" but they were occasionally called "creationists" in
private correspondence between Charles Darwin and his friends. As the creation–evolution controversy developed,
the term "anti-evolutionists" became more common, then in 1929 in the United States the term "creationism" first
became specifically associated with Christian fundamentalist opposition to human evolution and belief in a young
Earth, though its usage was contested by other groups who believed in various concepts of creation.[4]
Since the 1920s, creationism in America has contested scientific theories, such as that of evolution,[5] [6] which
derive from natural observations of the universe and life. Strict creationists[7] believe that evolution cannot
adequately account for the history, diversity, and complexity of life on Earth.[8] Strict creationists of the Christian
faith usually base their belief on a literal reading of the Genesis creation narrative.[7] [9] Other religions have
different deity-led creation myths,[10] [11] [12] [13] while different members of individual faiths vary in their
acceptance of scientific findings. In contrast to the strict creationists, evolutionary creationists maintain that,
although evolution accounts for the nature of the biosphere, evolution itself is cosmologically attributable to a
Creator deity.[14]
When mainstream scientific research produces theoretical conclusions which contradict a strict creationist
interpretation of scripture, creationists often reject the conclusions of the research[15] or its underlying scientific
theories[16] or its methodology.[17] The rejection of scientific findings has sparked political and theological
controversy.[2] Two offshoots of creationism—creation science and intelligent design—have been characterized as
pseudoscience by the mainstream scientific community.[18] The most notable disputes concern the evolution of living
organisms, the idea of common descent, the geological history of the Earth, the formation of the solar system and the
origin of the universe.[19] [20] [21] [22]

History
The history of creationism is part of the history of religions, though the term itself is modern. In the 1920s the term
became particularly associated with Christian fundamentalist movements that insisted on a literalist interpretation of
the Genesis creation narrative and likewise opposed the idea of human evolution. These groups succeeded in getting
teaching of evolution banned in United States public schools, then from the mid-1960s the young Earth creationists
promoted the teaching of "scientific creationism" using "Flood geology" in public school science classes as support
for a purely literal reading of Genesis.[23] After the legal judgment of the case Daniel v. Waters (1975) ruled that
teaching creationism in public schools contravened the Establishment Clause of the First Amendment, the content
was stripped of overt biblical references and renamed creation science. When the court case Edwards v. Aguillard
(1987) ruled that creation science similarly contravened the constitution, all references to "creation" in a draft school
textbook were changed to refer to intelligent design, which was subsequently claimed to be a new scientific theory.
The Kitzmiller v. Dover (2005) ruling concluded that intelligent design is not science and contravenes the
constitutional restriction on teaching religion in public school science classes.[24]
Creationism 385

Judaism and early and medieval Christianity

The Genesis creation narrative appears in the Jewish Torah, and early Jewish teachers believed that the inspired
biblical text contains layers of meaning, with the spiritual and allegorical interpretations of Genesis often being seen
as more important than the literal. The first century Jewish writer Philo admired the literal narrative of passages
concerning the Patriarchs, but in other passages viewed the literal interpretation as being for those unable to see an
underlying deeper meaning. For example, he noted that Moses said the world was created in six days, but did not
consider this as a length of time as "we must think of God as doing all things simultaneously" and the six days were
mentioned because of a need for order and according with a perfect number. Genesis was about real events, but God
through Moses described them in figurative or allegorical language. The tradition of such writers as Abraham ibn
Ezra consistently rejected overly literal understandings of Genesis, and Maimonides described the story of Eve and
the serpent as "most absurd in its literal sense; but as an allegory it contains wonderful wisdom, and fully agrees with
the real facts".[25] [26]
To a large extent, the early Christian Church Fathers read creation history as an allegory, and followed Philo's ideas
of time beginning with an instantaneous creation, with days not meant literally. Christian orthodoxy rejected the
second century Gnostic belief that Genesis was purely allegorical, but without taking a purely literal view of the
texts. Thus Origen believed that the physical world is ‘literally’ a creation of God, but did not take the chronology or
the days as ‘literal’. Similarly, Saint Basil in the fourth century while literal in many ways, described creation as
instantaneous and timeless, being immeasurable and indivisible.[25]
Augustine of Hippo in The Literal Meaning of Genesis was insistent that Genesis describes the creation of physical
things, but also shows creation occurring simultaneously, with the days of creation being categories for didactic
reasons, a logical framework which has nothing to do with time. For him, light was the illumination of angels rather
than visible light, and spiritual light was just as literal as physical light. Augustine emphasized that the text was
difficult to understand and should be reinterpreted as new knowledge became available. In particular, Christians
should not make absurd dogmatic interpretations of scripture which contradict what people know from physical
evidence.[27]
In the thirteenth century Thomas Aquinas, like Augustine, asserted the need to hold the truth of Scripture without
wavering while cautioning "that since Holy Scripture can be explained in a multiplicity of senses, one should not
adhere to a particular explanation, only in such measure as to be ready to abandon it if it be proved with certainty to
be false; lest holy Scripture be exposed to the ridicule of unbelievers, and obstacles be placed to their believing."[25]

Natural theology
From 1517 the Protestant Reformation brought a new emphasis on lay literacy, with Martin Luther advocating the
idea that creation took six literal days about 6000 years ago, and claiming that "Moses wrote that uneducated men
might have clear accounts of creation", though a German peasant listening to a translation would have different
perceptions from a Jew familiar with early Jewish language and culture, and Luther still had to refer to allegorical
understandings such as the meaning of the serpent. John Calvin also rejected instantaneous creation, but criticised
those who, contradicting the contemporary understanding of nature, asserted that there are "waters above the
heavens".[25]
Discoveries of new lands brought knowledge of a huge diversity of life, and a new belief developed that each of
these biological species had been individually created by God. In 1605 Francis Bacon emphasized that the works of
God in nature teach us how to interpret the word of God in the Bible, and his Baconian method introduced the
empirical approach which became central to modern science.[28] Natural theology developed the study of nature with
the expectation of finding evidence supporting Christianity, and numerous attempts were made to reconcile new
knowledge with the biblical Deluge myth and story of Noah's Ark.[29]
In 1650 the Archbishop of Armagh, James Ussher, published the Ussher chronology based on Bible history giving a
date for Creation of 4004 BC. This was generally accepted, but the development of modern geology in the 18th and
Creationism 386

19th centuries found geological strata and fossil sequences indicating an ancient Earth. Catastrophism was favoured
in England as supporting the Biblical flood, but this was found to be untenable[29] and by 1850 all geologists and
most Evangelical Christians had adopted various forms of old Earth creationism, while continuing to firmly reject
evolution.[25]

Growing evidence for evolution

From around the start of the nineteenth century, ideas such as Jean-Baptiste Lamarck's concept of transmutation of
species had gained a small number of supporters in Paris and Edinburgh, mostly amongst anatomists.[25] Britain at
that time was enmeshed in the Napoleonic Wars, and fears of republican revolutions such as the American
Revolution and French Revolution led to a harsh repression of such evolutionary ideas, which challenged the divine
hierarchy justifying the monarchy. Charles Darwin's development of his theory of natural selection at this time was
kept closely secret. Repression eased, and the anonymous publication of Vestiges of Creation in 1844 aroused wide
public interest with support from Quakers and Unitarians, but was strongly criticised by the scientific community,
which emphasized the need for solidly backed science. In 1859 Darwin's On the Origin of Species provided that
evidence from an authoritative and respected source, and gradually convinced scientists that evolution occurs. This
acceptance was resisted by conservative evangelicals in the Church of England, but their attention quickly turned to
the much greater uproar about Essays and Reviews by liberal Anglican theologians, which introduced into the
controversy "the higher criticism" begun by Erasmus centuries earlier. This book re-examined the Bible and cast
doubt on a literal interpretation.[30] By 1875 most American naturalists supported ideas of theistic evolution, often
involving special creation of human beings.[23]
At this time those holding that species had been separately created were generally called "advocates of creation", but
they were occasionally called "creationists" in private correspondence between Charles Darwin and his friends.[4]
The term appears in letters Darwin wrote between 1856 and 1863,[31] and was also used in a response by Charles
Lyell.[32]

Theistic evolution
Through the 19th century the term creationism most commonly referred to direct creation of individual souls, in
contrast to traducianism. Following the publication of Vestiges there was interest in ideas of Creation by divine law.
In particular, the liberal theologian Baden Powell argued that this illustrated the Creator's power better than the idea
of miraculous creation, which he thought ridiculous.[33] When On the Origin of Species was published, the cleric
Charles Kingsley wrote of evolution as "just as noble a conception of Deity".[34] [35] Darwin's view at the time was
of God creating life through the laws of nature,[36] [37] and the book makes several references to "creation", though
he later regretted using the term rather than calling it an unknown process.[38] In America, Asa Gray argued that
evolution is the secondary effect, or modus operandi, of the first cause, design,[39] and published a pamphlet
defending the book in theistic terms, Natural Selection is not inconsistent with Natural Theology.[34] [40] [41] Theistic
evolution became a popular compromise, and St. George Jackson Mivart was among those accepting evolution but
attacking Darwin's naturalistic mechanism. Eventually it was realised that supernatural intervention could not be a
scientific explanation, and naturalistic mechanisms such as neo-Lamarckism were favoured as being more
compatible with purpose than natural selection.[42]
Some theists took the general view that, instead of faith being in opposition to biological evolution, some or all
classical religious teachings about Christian God and creation are compatible with some or all of modern scientific
theory, including specifically evolution; it is also known as "evolutionary creation". In Evolution Vs. Creationism,
Eugenie Scott and Niles Eldredge state that it is in fact a type of evolution.[43]
It generally views evolution as a tool used by God, who is both the first cause and immanent sustainer/upholder of
the universe; it is therefore well accepted by people of strong theistic (as opposed to deistic) convictions. Theistic
evolution can synthesize with the day-age interpretation of the Genesis creation narrative; however most adherents
Creationism 387

consider that the first chapters of Genesis should not be interpreted as a "literal" description, but rather as a literary
framework or allegory.
From a theistic viewpoint, the underlying laws of nature were designed by God for a purpose, and are so
self-sufficient that the complexity of the entire physical universe evolved from fundamental particles in processes
such as stellar evolution, life forms developed in biological evolution, and in the same way the origin of life by
natural causes has resulted from these laws.[44]
In one form or another, theistic evolution is the view of creation taught at the majority of mainline Protestant
seminaries[45] For Catholics, human evolution is not a matter of religious teaching, and must stand or fall on its own
scientific merits. Evolution and the Roman Catholic Church are not in conflict. The Catechism of the Catholic
Church comments positively on the theory of evolution, which is neither precluded nor required by the sources of
faith, stating that scientific studies "have splendidly enriched our knowledge of the age and dimensions of the
cosmos, the development of life-forms and the appearance of man."[46] Roman Catholic schools teach evolution
without controversy on the basis that scientific knowledge does not extend beyond the physical, and scientific truth
and religious truth cannot be in conflict.[47] Theistic evolution can be described as "creationism" in holding that
divine intervention brought about the origin of life or that divine Laws govern formation of species, though many
creationists (in the strict sense) would deny that the position is creationism at all. In the creation-evolution
controversy its proponents generally take the "evolutionist" side. This sentiment was expressed by Fr. George Coyne,
(Vatican's chief astronomer between 1978 and 2006):
...in America, creationism has come to mean some fundamentalistic, literal, scientific interpretation of
Genesis. Judaic-Christian faith is radically creationist, but in a totally different sense. It is rooted in a
belief that everything depends upon God, or better, all is a gift from God.[48]
While supporting the methodological naturalism inherent in modern science, the proponents of theistic evolution
reject the implication taken by some atheists that this gives credence to ontological materialism. In fact, many
modern philosophers of science,[49] including atheists,[50] refer to the long standing convention in the scientific
method that observable events in nature should be explained by natural causes, with the distinction that it does not
assume the actual existence or non-existence of the supernatural.

Re-emergence in the United States

In the United States, some religious communities have refused to accept, as theistic evolutionists have accepted,
naturalistic explanations, and tried instead to counter them. In the United States the term started to become
associated with Christian fundamentalist opposition to human evolution and belief in a young Earth in 1929.[4]
Several U.S. states passed laws against the teaching of evolution in public schools, as upheld in the Scopes Trial.
Evolution was omitted entirely from school textbooks in much of the United States until the 1960s. Since then,
renewed efforts to introduce teaching creationism in American public schools in the form of flood geology, creation
science, and intelligent design have been consistently held to contravene the constitutional separation of Church and
State by a succession of legal judgments.[24] The meaning of the term creationism was contested, but by the 1980s it
had been co-opted by proponents of creation science and flood geology.[4]
Such beliefs include Young Earth creationism, proponents of which believe that the earth is thousands rather than
billions of years old. They typically believe the days in Genesis Chapter 1 are 24 hours in length, while Old Earth
creationism accepts geological findings and other methods of dating the earth and believes that these findings do not
contradict the Genesis myth, but reject evolution. The term theistic evolution has been coined to refer to beliefs in
creationism which are more compatible with the scientific view of evolution and the age of the Earth. Alternately,
there are other religious people who support creationism, but in terms of allegorical interpretations of Genesis.
By the start of the twentieth century, evolution was widely accepted and was beginning to be taught in U.S. public
schools. After World War I, popular belief that German aggression resulted from a Darwinian doctrine of "survival
of the fittest" inspired William Jennings Bryan to campaign against the teaching of Darwinian ideas of human
Creationism 388

evolution.[23] In the 1920s, the Fundamentalist-Modernist Controversy led to an upsurge of fundamentalist religious
fervor in which schools were prevented from teaching evolution through state laws such as Tennessee’s 1925 Butler
Act,[51] [52] and by getting evolution removed from biology textbooks nationwide. Creationism became associated in
common usage with opposition to evolution.[53]
In 1961 in the United States, an attempt to repeal the Butler Act failed.[24] The Genesis Flood by the Baptist engineer
Henry M. Morris brought the Seventh-day Adventist biblically literal flood geology of George McCready Price to a
wider audience, popularizing a novel idea of Young Earth creationism,[25] and by 1965 the term "scientific
creationism" had gained currency.[54] The 1968 Epperson v. Arkansas judgment ruled that state laws prohibiting the
teaching of evolution violate the Establishment Clause of the First Amendment of the U.S. Constitution which
prohibits state aid to religion.[55] and when in 1975 Daniel v. Waters ruled that a state law requiring biology
textbooks discussing "origins or creation of man and his world" to give equal treatment to creation as per Book of
Genesis was unconstitutional, a new group identifying themselves as creationists promoted a "Creation science"
which omitted explicit biblical references.[24]
In 1981 the state of Arkansas passed a law, Act 590, mandating that "creation science" be given equal time in public
schools with evolution, and defining creation science as positing the “creation of the universe, energy, and life from
nothing,” as well as explaining the earth’s geology by "the occurrence of a worldwide flood".[54] This was ruled
unconstitutional at McLean v. Arkansas in January 1982 as the creationists' methods were not scientific but took the
literal wording of the Book of Genesis and attempted to find scientific support for it.[54] Undaunted, Louisiana
introduced similar legislation that year. A series of judgments and appeals led to the 1987 Supreme Court ruling in
Edwards v. Aguillard that it too violated the Establishment Clause of the First Amendment.[52]
"Creation science" could no longer be taught in public schools, and in drafts of the creation science school textbook
Of Pandas and People all references to creation or creationism were changed to refer to intelligent design.[52]
Proponents of the intelligent design movement organised widespread campaigning to considerable effect. They
officially denied any links to creation or to religion, and indeed claimed that "creationism" only referred to young
Earth creationism with flood geology;[56] but in Kitzmiller v. Dover the court found intelligent design to be
essentially religious, and unable to dissociate itself from its creationist roots, as part of the ruling that teaching
intelligent design in public school science classes was unconstitutional.[52]
However, the percentage of people in the USA who accept the idea of evolution declined from 45% in 1985, to 40%
in 2005.[57]

Movements
Creationist movements exist among peoples with various religions perspectives such as Judaism, Hinduism,
Christianity and Islam.

Ahmadiyya Muslim Community

The Ahmadiyya Movement is perhaps the only denomination in Islam that actively promotes evolutionary theory.[58]
Ahmadis interpret scripture from the Quran to support the concept of macroevolution and give precedence to
scientific theories. Furthermore, unlike more orthodox Muslims, Ahmadis believe that mankind has gradually
evolved from different species. Ahmadis regard Adam as being the first Prophet of God – as opposed to him being
the first man on Earth.[59] Rather than wholly adopting the theory of natural selection, Ahmadis promote the idea of a
"guided evolution", viewing each stage of the evolutionary process as having been selectively woven by God.[60]
Mirza Tahir Ahmad, Fourth Caliph of the Ahmadiyya Muslim Community has stated in his magnum opus
Revelation, Rationality, Knowledge & Truth that evolution did occur but only through God being the One who brings
it about. It does not occur itself, according to the Ahmadiyya Muslim Community.
Creationism 389

Bahá'í Faith
The Bahá'í Faith holds the harmony of religion and science as a fundamental principle. Bahá'ís regards the biblical
account of creation as symbolic, albeit important and full of symbolic meaning.[61] Far from accepting the idea of a
Young Earth, Bahá'í theology regards the Earth as ancient.[62]
Humanity, Bahá'ís hold, has changed in physical form over time. Bahá'í theology holds that humanity is a species
essence - an essential reality and part of God's eternal creation; as a biological species, however, humanity has gone
through numerous physical changes and adaptations in time.[62] The Bahá'í faith regards evolution (as a progress of
physical form) and the act of divine creation as related processes or even as the same process viewed in different
contexts. However, Bahá'í literature maintains that humanity is distinct from other parts of creation on Earth - that
only mankind has a soul, and is capable of abstract thought and of spiritual development.[62]

Judaism and Christianity

Many Christians around the world today accept evolution as the most likely explanation for the origins of species,
and do not take a literal view of the Genesis creation narrative. The United States is the exception where belief in
religious fundamentalism is much more likely to affect attitudes towards evolution than it is for believers elsewhere.
Political partisanship affecting religious belief may be a factor because whilst political partisanship in the U.S. is
highly correlated with fundamentalist thinking this is not so in Europe.[57]
Most contemporary Christian leaders and scholars from mainstream churches,[63] such as Anglicans[64] and
Lutherans,[65] consider that there is no conflict between the spiritual meaning of creation and the science of
evolution. According to the Archbishop of Canterbury, Rowan Williams, "...for most of the history of Christianity
(and I think this is fair enough) an awareness that a belief that everything depends on the creative act of God, is quite
compatible with a degree of uncertainty or latitude about how precisely that unfolds in creative time."[66]
Leaders of the Anglican[67] and Roman Catholic[68] [69] churches have made statements in favor of evolutionary
theory, as have scholars such as John Polkinghorne, who argue that evolution is one of the principles through which
God created living beings. Earlier supporters of evolutionary theory include Frederick Temple, Asa Gray and
Charles Kingsley who were enthusiastic supporters of Darwin's theories upon their publication,[70] and the French
Jesuit priest and geologist Pierre Teilhard de Chardin saw evolution as confirmation of his Christian beliefs, despite
condemnation from Church authorities for his more speculative theories. Another example is that of Liberal
theology, not providing any creation models, but instead focusing on the symbolism in beliefs of the time of
authoring Genesis, the cultural environment, and comparison to non-Jewish "cosmologies" of that age. In fact, both
Jews and Christians had been considering the idea of the creation history as an allegory (instead of a historical
description) long before the development of Darwin's theory of evolution. Two notable examples are the first century
Jewish neoplatonic philosopher Philo of Alexandria and Saint Augustine of the late fourth century who was also a
former neoplatonist. Philo wrote that it would be a mistake to think that creation happened in six days, or in any set
amount of time.[71] Augustine argued that everything in the universe was created by God at the same moment in time
(and not in six days as a literal reading of Genesis would seem to require);[72] It appears that both Philo and
Augustine felt uncomfortable with the idea of a seven day creation because it detracted from the notion of God's
omnipotence.
However, in the United States, an inversion has happened. Few Jews today (17%) are likely to accept the Biblical
literal interpretation of the creation and favor an alternative explanation. However evangelical Christians have
continued to believe the literal claims of Genesis. Members of Protestant (70%), Mormon (76%) and Jehovah's
Witnesses (90%) denominations are those most likely to reject the evolutionary interpretation of the origins of
life.[73]
The historic Christian literal interpretation of creation requires the harmonization of the two creation stories, Genesis
1:1-2:3 and Genesis 2:4-25, for there to be a consistent interpretation.[74] [75] They sometimes seek to ensure that
their belief is taught in science classes, mainly in American schools (see Young Earth Creationism, for example).
Creationism 390

Opponents reject the claim that the literalistic Biblical view meets the criteria required to be considered scientific.
Many religious sects teach that God created the Cosmos. From the days of the early Christian Church Fathers there
were allegorical interpretations of Genesis as well as literal aspects.[25]

Types of Biblical creationism

Several attempts have been made to categorize the different types of creationism, and create a "taxonomy" of
creationists.[76] [77] [78] Creationism covers a spectrum of beliefs which have been categorized into the broad types
listed below. As a matter of popular belief and characterizations by the media, most people labeled "creationists" are
those who object to specific parts of science for religious reasons; however many (if not most) people who believe in
a divine act of creation do not categorically reject those parts of science.

Comparison of major creationist views

Humanity Biological species Earth Age of Universe

Young Earth Directly created by God. Directly created by God. Macroevolution does Less than 10,000 years old. Less than 10,000
creationism not occur. Reshaped by global flood. years old.

Gap Directly created by God. Directly created by God. Macroevolution does Scientifically accepted age. Scientifically
creationism not occur. Reshaped by global flood. accepted age.

Progressive Directly created by God Direct creation + evolution. No single common Scientifically accepted age. No Scientifically
creationism (based on primate anatomy). ancestor. global flood. accepted age.

Intelligent Proponents hold various Divine intervention at some point in the past, Some adherents claim the Scientifically
design beliefs. e.g. Behe accepts as evidenced by what intelligent-design existence of Earth is the result accepted age
evolution from primates creationists call "irreducible complexity" of divine intervention

Theistic Evolution from primates. Evolution from single common ancestor. Scientifically accepted age. No Scientifically
evolution global flood. accepted age.

Young Earth creationism

Young Earth creationism is the belief that the Earth was created by God within the last ten thousand years, literally
as described in Genesis creation narrative, within the approximate time frame of biblical genealogies (detailed for
example in the Ussher chronology). Most Young Earth creationists believe that the Universe has a similar age as the
Earth. A few assign a much older age to the Universe than to Earth. Creationist cosmologies are attempts by some
creationist thinkers to give the universe an age consistent with the Ussher chronology and other Young-Earth time
frames. Other Young-Earth creationists believe that the Earth and the universe were created with the appearance of
age, so that the world appears to be much older than it is, and that this appearance is what gives the geological
findings and other methods of dating the earth and the universe their much longer timelines.
The Christian organizations Institute for Creation Research (ICR) and the Creation Research Society (CRS) both
promote Young Earth Creationism in the USA. Another organization with similar views, Answers in Genesis (AIG)
Ministries based in both the US and United Kingdom, has opened a Creation Museum to promote Young Earth
Creationism. Creation Ministries International promotes Young Earth views in Australia, Canada, South Africa and
New Zealand. Among Catholics, the Kolbe Center for the Study of Creation promotes similar ideas.
Creationism 391

Modern geocentrism
Modern geocentrism holds that God recently created a spherical world, and placed it in the center of the universe.
The Sun, planets and everything else in the universe revolve around it.

Omphalos hypothesis
The Omphalos hypothesis argues that in order for the world to be functional, God must have created a mature Earth
with mountains and canyons, rock strata, trees with growth rings, and so on; therefore no evidence that we can see of
the presumed age of the earth and universe can be taken as reliable.[79] The idea has seen some revival in the
twentieth century by some modern creationists, who have extended the argument to light that appears to originate in
far-off stars and galaxies (see Starlight problem).

Creation science
Creation science is the attempt to present scientific evidence interpreted with Genesis axioms that supports the
claims of creationism. Various claims of creation scientists include such ideas as creationist cosmologies which
accommodate a universe on the order of thousands of years old, attacks on the science of radiometric dating through
a technical argument about radiohalos, explanations for the fossil record as a record of the destruction of the global
flood recorded in Book of Genesis (see flood geology), and explanations for the present diversity as a result of
pre-designed genetic variability and partially due to the rapid degradation of the perfect genomes God placed in
"created kinds" or "Baramin" (see creation biology) due to mutations.

Old Earth creationism

Old Earth creationism holds that the physical universe was created by God, but that the creation event of Genesis is
not to be taken strictly literally. This group generally believes that the age of the Universe and the age of the Earth
are as described by astronomers and geologists, but that details of modern evolutionary theory are questionable.
Old-Earth creationism itself comes in at least three types:

Gap creationism
Gap creationism, also called "Restitution creationism", holds that life was recently created on a pre-existing old
Earth. This theory relies on a particular interpretation of Genesis  1:1-2. It is considered that the words formless and
void in fact denote waste and ruin, taking into account the original Hebrew and other places these words are used in
the Old Testament. Genesis 1:1-2 is consequently translated:
"In the beginning God created the heavens and the earth." (Original act of creation.)
"And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God
moved upon the face of the waters."
Thus, the six days of creation (verse 3 onwards) start sometime after the Earth was "without form and void." This
allows an indefinite "gap" of time to be inserted after the original creation of the universe, but prior to creation
according to the Genesis creation narrative(when present biological species and humanity were created). Gap
theorists can therefore agree with the scientific consensus regarding the age of the Earth and universe, while
maintaining a literal interpretation of the biblical text.
Some gap theorists expand the basic theory by proposing a "primordial creation" of biological life within the "gap"
of time. This is thought to be "the world that then was" mentioned in 2 Peter 3:3-7.[80] Discoveries of fossils and
archaeological ruins older than 10,000 years are generally ascribed to this "world that then was", which may also be
associated with Lucifer's rebellion. These views became popular with publications of Hebrew Lexicons such as the
Strong's Concordance, and Bible commentaries such as the Scofield Reference Bible and the Companion Bible.
Creationism 392

Day-Age creationism
Day-Age creationism states that the "six days" of Book of Genesis are not ordinary twenty-four-hour days, but rather
much longer periods (for instance, each "day" could be the equivalent of millions, or billions of years of human
time). This theory often states that the Hebrew word "yôm", in the context of Genesis 1, can be properly interpreted
as "age." Some adherents claim we are still living in the seventh age ("seventh day").
Strictly speaking, Day-Age creationism is not so much a creationist theory as a hermeneutic option which may be
combined with theories such as progressive creationism.

Progressive creationism
Progressive creationism holds that species have changed or evolved in a process continuously guided by God, with
various ideas as to how the process operated—though it is generally taken that God directly intervened in the natural
order at key moments in Earth/life's history. This view accepts most of modern physical science including the age of
the earth, but rejects much of modern evolutionary biology or looks to it for evidence that evolution by natural
selection alone is incorrect. Organizations such as Reasons to Believe, founded by Hugh Ross, promote this theory.
Progressive creationism can be held in conjunction with hermeneutic approaches to Genesis chapter 1 such as the
day-age theory or framework/metaphoric/poetic views.

Neo-Creationism
Neo-Creationists intentionally distance themselves from other forms of creationism, preferring to be known as
wholly separate from creationism as a philosophy. Its goal is to restate creationism in terms more likely to be well
received by the public, education policy makers and the scientific community. It aims to re-frame the debate over the
origins of life in non-religious terms and without appeals to scripture, and to bring the debate before the public.
One of its principal claims is that ostensibly objective orthodox science is actually a dogmatically atheistic religion.
Neo-Creationists argue that the scientific method excludes certain explanations of phenomena, particularly where
they point towards supernatural elements. They argue that this effectively excludes any possible religious insight
from contributing to a scientific understanding of the universe. Neo-Creationists also argue that science, as an
"atheistic enterprise," is at the root of many of contemporary society's ills including social unrest and family
breakdown.
The most recognized form of Neo-Creationism in the United States is the Intelligent Design movement. Unlike their
philosophical forebears, Neo-Creationists largely do not believe in many of the traditional cornerstones of
creationism such as a young Earth, or in a dogmatically literal interpretation of the Bible. Common to all forms of
Neo-Creationism is a rejection of naturalism, usually made together with a tacit admission of supernaturalism, and
an open and often hostile opposition to what they term "Darwinism", which generally is meant to refer to evolution.

Intelligent design
Intelligent design (ID) is the claim that "certain features of the universe and of living things are best explained by an
intelligent cause, not an undirected process such as natural selection".[81] All of its leading proponents are associated
with the Discovery Institute,[82] a think tank whose Wedge strategy aims to replace the scientific method with "a
science consonant with Christian and theistic convictions" which accepts supernatural explanations.[52] [83] It is
widely accepted in the scientific and academic communities that intelligent design is a form of creationism,[84] [77]
[78] [85]
and some have even begun referring to it as "intelligent design creationism".[86] [87] [88]
ID originated as a re-branding of creation science in an attempt to get round a series of court decisions ruling out the
teaching of creationism in U.S. public schools, and the Discovery Institute has run a series of campaigns to change
school curricula.[24] In Australia, where curricula are under the control of State governments rather than local school
boards, there was a public outcry when the notion of ID being taught in science classes was raised by the Federal
Education Minister Brendan Nelson; the minister quickly conceded that the correct forum for ID, if it were to be
Creationism 393

taught, is in religious or philosophy classes.[89]

In the United States, teaching of Intelligent Design in public schools has been decisively ruled by a Federal District
court to be in violation of the Establishment Clause of the First Amendment to the United States Constitution. In
Kitzmiller v. Dover Area School District, the court found that intelligent design is not science and "cannot uncouple
itself from its creationist, and thus religious, antecedents.", and hence cannot be taught as an alternative to Evolution
in public school science classrooms under the jurisdiction of that court. This sets a persuasive precedent, based on
previous Supreme Court decisions in Edwards v. Aguillard and Epperson v. Arkansas, and by the application of the
Lemon test, that creates a legal hurdle to teaching Intelligent Design in public school districts in other Federal court
jurisdictions.[52] [90]

Hinduism
Some Hindus find support for, or foreshadowing of evolutionary ideas in scriptures, namely the Vedas.[91] The
International Society for Krishna Consciousness (ISKCON) includes several members who actively oppose
"Darwinism" and the modern evolutionary synthesis.[92]

Islam
Islamic creationism is the belief that the universe (including humanity) was directly created by God as explained in
the Qur'an. It usually views Genesis as a corrupted version of God's message. The creation myths in the Qur'an are
vaguer and allow for a wider range of interpretations similar to those in other Abrahamic religions. Most Muslims
generally accept the scientific positions on the age of the earth, the age of the universe, however unlike Ahmadi
Muslims, not evolution. Muslims believe that humans have been inserted on earth on a much later date from the
creation of earth.
Islam also has its own school of Evolutionary creationism/Theistic evolutionism, which holds that mainstream
scientific analysis of the origin of the universe is supported by the Qur'an. Some Muslims believe in evolutionary
creationism, especially among Liberal movements within Islam.
Khalid Anees, president of the Islamic Society of Britain, at a conference called 'Creationism: Science and Faith in
Schools', made points including the following:[93] There is no contradiction between what is revealed in the Koran
and natural selection and survival of the fittest. However, some Muslims, such as Adnan Oktar, do not agree that one
species can develop from another.[94]
But there is also a growing movement of Islamic creationism. Similar to Christian creationism, there is concern
regarding the perceived conflicts between the Qur'an and the main points of evolutionary theory. The main location
for this has been in Turkey, where fewer than 25% of people believe in evolution.[95]
There are several verses in the Qur'an which some modern writers have interpreted as being compatible with the
expansion of the universe, Big Bang and Big Crunch theories:[96] [97] [98]
"Do not the Unbelievers see that the skies (space) and the earth were joined together, then We (Allah)
clove them asunder and We (Allah) created every living thing out of the water. Will they not then
believe?"[Qur'an 21:30]
"Then turned He to the sky (space) when it was smoke, and said unto it and unto the earth: Come both of
you, willingly or loth. They said: We come, obedient."[Qur'an 41:11]
"And it is We (Allah) Who have constructed the sky (space) with might, and it is We (Allah) Who are
steadily expanding it."[Qur'an 51:47]
"On the day when We (Allah) will roll up the sky (space) like the rolling up of the scroll for writings, as
We (Allah) originated the first creation, (so) We (Allah) shall reproduce it; a promise (binding on Us);
surely We will bring it about."[Qur'an 21:104]
Many Islam majority countries have expelled science textbooks containing human evolution.[99]
Creationism 394

Judaism
Judaism has a continuum of views about creation, the origin of life and the role of evolution in the formation of
species. The major Jewish denominations, including many Orthodox Jewish groups, accept evolutionary creationism
or theistic evolution. Many Conservative Rabbis follow theistic evolution, although Conservative Judaism does not
have an official view on the subject. Conservative Judaism however, does generally embrace science and therefore
finds it a "challenge to traditional Jewish theology."[100] Reform Judaism does not take the Torah as a literal text, but
rather as a symbolic or open-ended work. For Orthodox Jews who seek to reconcile discrepancies between science
and the Bible, the notion that science and the Bible should even be reconciled through traditional scientific means is
questioned. To these groups, science is as true as the Torah and if there seems to be a problem, our own
epistemological limits are to blame for any apparent irreconcilable point. They point to various discrepancies
between what is expected and what actually is to demonstrate that things are not always as they appear. They point
out the fact that the even root word for "world" in the Hebrew language — ‫( םלוע‬Olam) — means hidden — ‫םלענ‬
(Neh-Eh-Lahm). Just as they believe God created man and trees and the light on its way from the stars in their adult
state, so too can they believe that the world was created in its "adult" state, with the understanding that there are, and
can be, no physical ways to verify it. This belief has been advanced by Rabbi Dr. Dovid Gottlieb, former philosophy
professor at Johns Hopkins University. Also, relatively old Kabbalistic sources from well before the scientifically
apparent age of the universe was first determined are in close concord with modern scientific estimates of the age of
the universe, according to Rabbi Aryeh Kaplan, and based on Sefer Temunah, an early kabbalistic work attributed to
the 1st century Tanna Nehunya ben ha-Kanah. Many kabbalists accepted the teachings of the Sefer Temunah,
including the Ramban, his close student Yitzhak of Akko, and the RADBAZ. Other interesting parallels are derived,
among other sources, from Nachmanides, who expounds that there was a Neanderthal-like species with which Adam
mated (he did this long before Neanderthals had even been discovered scientifically).[101] [102] [103] [104] In 1838
rabbi Israel Lipschitz again restated that the calculations of the ancient kabbalists that Creation occurred about 15.3
billion years ago were in line with the 19th century scientific theories.

Prevalence
Most vocal strict creationists are from
the United States, and strict creationist
views are much less common in other
developed countries. According to a
study published in Science, a survey of
the United States, Turkey, Japan and
Europe showed that public acceptance
of evolution is most prevalent in
Iceland, Denmark and Sweden at 80%
of the population.[57]

Australia
According to a PBS documentary on
evolution, Australian Young Earth
Creationists claimed that "five percent Views on human evolution in various countries.
[105] [106]
of the Australian population now
believe that Earth is thousands, rather than billions, of years old."[107] A 2009 Nielsen poll showed that almost a
quarter of Australians believe "the biblical account of human origins" over the Darwinian account. Forty-two percent
believe in a "wholly scientific" explanation for the origins of life, while 32 percent believe in an evolutionary process
Creationism 395

"guided by God".[108]

Canada
A 2008 Canadian poll revealed that "58 percent accept evolution, while 22 percent think that God created humans in
their present form within the last 10,000 years."[109]

Europe
In Europe, strict creationism is less well accepted, though regular opinion polls are not available. Most people accept
that evolution is the most widely accepted scientific theory as taught in most schools. In countries with a Roman
Catholic majority, papal acceptance of evolution as worthy of study has essentially ended debate on the matter for
many people.
In the United Kingdom, the Archbishop of Canterbury Rowan Williams, head of the worldwide Anglican
Communion, views the idea of teaching creationism in schools as a mistake.[110] A 2006 poll on the "origin and
development of life" asked participants to choose between three different perspectives on the origin of life: 22%
chose creationism, 17% opted for intelligent design, 48% selected evolutionary theory, and the rest did not
know.[111] [112]
Exceptionally, in the United Kingdom the Emmanuel Schools Foundation (previously the Vardy Foundation), which
runs three government-funded 13 to 19 schools in the north of England (out of several thousand in the country)
teaches that creationism and evolution are equally valid "faith positions". One exam board (OCR) also specifically
mentions and deals with creationism in its biology syllabus.[113] However, this deals with it as a historical belief and
addresses hostility towards evolution rather than promoting it as an alternative to naturalistic evolution. Mainstream
scientific accounts are expressed as fact. In Italy, prime minister Silvio Berlusconi wanted to retire evolution from
schools in the middle level; after one week of massive protests, he reversed his opinion.[114]
There continues to be scattered and possibly mounting efforts on the part of religious fundamentalists throughout
Europe to introduce creationism into public education.[115] In response, the Parliamentary Assembly of the Council
of Europe has released a draft report entitled The dangers of creationism in education on June 8, 2007,[116]
reinforced by a further proposal of banning it in schools dated October 4, 2007.[117]
Serbia suspended the teaching of evolution for one week in September 2004, under education minister Ljiljana Čolić,
only allowing schools to reintroduce evolution into the curriculum if they also taught creationism.[118] "After a
deluge of protest from scientists, teachers and opposition parties" says the BBC report, Čolić's deputy made the
statement, "I have come here to confirm Charles Darwin is still alive" and announced that the decision was
reversed.[119] Čolić resigned after the government said that she had caused "problems that had started to reflect on
the work of the entire government."[120]
Poland saw a major controversy over creationism in 2006 when the deputy education minister, Mirosław
Orzechowski, denounced evolution as "one of many lies" taught in Polish schools. His superior, Minister of
Education Roman Giertych, has stated that the theory of evolution would continue to be taught in Polish schools, "as
long as most scientists in our country say that it is the right theory." Giertych's father, Member of the European
Parliament Maciej Giertych, has opposed the teaching of evolution and has claimed that dinosaurs and humans
co-existed.[121]
Creationism 396

United States
According to a 2001 Gallup poll,[122] about 45% of North
Americans believe that "God created human beings pretty
much in their present form at one time within the last
10,000 years or so." Another 37% believe that "human
beings have developed over millions of years from less
advanced forms of life, but God guided this process",[123]
and 14% believe that "human beings have developed over
millions of years from less advanced forms of life, but God
had no part in this process".[122]

Belief in creationism is inversely correlated to education; of

those with postgraduate degrees, 74% accept evolution.[124]
[125] Anti-evolution car in Athens, Georgia
In 1987, Newsweek reported: "By one count there are
some 700 scientists with respectable academic credentials
(out of a total of 480,000 U.S. earth and life scientists) who give credence to creation-science, the general theory that
complex life forms did not evolve but appeared 'abruptly.'"[126] [127]

A 2000 poll for People for the American Way found 70% of the United States public felt that evolution was
compatible with a belief in God.[128]
According to a study published in Science, between 1985 and 2005 the number of adult North Americans who accept
evolution declined from 45% to 40%, the number of adults who reject evolution declined from 48% to 39% and the
number of people who were unsure increased from 7% to 21%. Besides the United States the study also compared
data from 32 European countries, Turkey, and Japan. The only country where acceptance of evolution was lower
than in the United States was Turkey (25%).[57]

Education controversies

In the United States, creationism has become centered in the political

controversy over creation and evolution in public education, and
whether teaching creationism in science classes conflicts with the
separation of church and state. Currently, the controversy comes in the
form of whether advocates of the Intelligent Design movement who The Truth fish, one of the many creationist
responses to the Darwin fish.
wish to "Teach the Controversy" in science classes have conflated
science with religion.[90]

People for the American Way polled 1500 North Americans about the teaching of evolution and creationism in
November and December 1999. They found that most North Americans were not familiar with Creationism, and
most North Americans had heard of evolution, but many did not fully understand the basics of the theory. The main
findings were:
Creationism 397

[128]
Americans believe that:

Public schools should teach evolution only 20%

Only evolution should be taught in science classes, religious explanations can be discussed in another class 17%

Creationism can be discussed in science class as a 'belief,' not a scientific theory 29%

Creationism and evolution should be taught as 'scientific theories' in science class 13%

Only Creationism should be taught 16%

Teach both evolution and Creationism, but unsure how to do so 4%

No opinion 1%

In such political contexts, creationists argue that their particular religiously based origin belief is superior to those of
other belief systems, in particular those made through secular or scientific rationale. Political creationists are
opposed by many individuals and organizations who have made detailed critiques and given testimony in various
court cases that the alternatives to scientific reasoning offered by creationists are opposed by the consensus of the
scientific community.[129] [130]

Christian criticism
Many Christians disagree with the teaching of creationism. Several religious organizations, among them the Catholic
Church, hold that their faith is not in conflict with the scientific consensus regarding evolution.[131] The Clergy
Letter Project, which has collected more than 13,000 signatures, is an "endeavor designed to demonstrate that
religion and science can be compatible."
In the article "Intelligent Design as a Theological Problem", George Murphy argues against the view that life on
Earth, in all its forms, is direct evidence of God's act of creation (Murphy quotes Phillip Johnson's claim that he is
speaking "of a God who acted openly and left his fingerprints on all the evidence."). Murphy argues that this view of
God is incompatible with the Christian understanding of God as "the one revealed in the cross and resurrection of
Jesus." The basis of this theology is Isaiah 45:15, "Truly, thou art a God who hidest thyself, O God of Israel, the
Savior."
Murphy observes that the execution of a Jewish carpenter by Roman authorities is in and of itself an ordinary event
and did not require Divine action. On the contrary, for the crucifixion to occur, God had to limit or "empty" Himself.
It was for this reason that Paul wrote, in Philippians 2:5-8,
Have this mind among yourselves, which is yours in Christ Jesus, who, though he was in the form of God, did
not count equality with God a thing to be grasped, but emptied himself, taking the form of a servant, being
born in the likeness of men. And being found in human form he humbled himself and became obedient unto
death, even death on a cross.
Murphy concludes that,
Just as the son of God limited himself by taking human form and dying on the cross, God limits divine
action in the world to be in accord with rational laws God has chosen. This enables us to understand the
world on its own terms, but it also means that natural processes hide God from scientific observation.
For Murphy, a theology of the cross requires that Christians accept a methodological naturalism, meaning that one
cannot invoke God to explain natural phenomena, while recognizing that such acceptance does not require one to
accept a metaphysical naturalism, which proposes that nature is all that there is.[132]
Other Christians have expressed qualms about teaching creationism. In March 2006, Archbishop of Canterbury
Rowan Williams, the leader of the world's Anglicans, stated his discomfort about teaching creationism, saying that
creationism was "a kind of category mistake, as if the Bible were a theory like other theories." He also said: "My
Creationism 398

worry is creationism can end up reducing the doctrine of creation rather than enhancing it." The views of the
Episcopal Church, the American branch of the Anglican Communion, on teaching creationism are also the same as
Williams.[133]
In April 2010, the American Academy of Religion issued Guidelines for Teaching About Religion in K‐12 Public
Schools in the United States which included guidance that creation science or intelligent design should not be taught
in science classes, as "Creation science and intelligent design represent worldviews that fall outside of the realm of
science that is defined as (and limited to) a method of inquiry based on gathering observable and measurable
evidence subject to specific principles of reasoning." However, they, as well as other "worldviews that focus on
speculation regarding the origins of life represent another important and relevant form of human inquiry that is
appropriately studied in literature or social sciences courses. Such study, however, must include a diversity of
worldviews representing a variety of religious and philosophical perspectives and must avoid privileging one view as
more legitimate than others."[134]

Scientific criticism
Science is a system of knowledge based on observation, empirical evidence and testable explanations of natural
phenomena. By contrast, creationism is based on literal interpretations of the narratives of particular religious texts.
Some creationist beliefs involve purported forces that lie outside of nature, such as supernatural intervention, and
these cannot be confirmed or disproved by scientists.[135] However, many creationist beliefs can be framed as
testable predictions about phenomena such as the age of the Earth, its geological history and the origins, distributions
and relationships of living organisms found on it. Early science incorporated elements of these beliefs, but as science
developed these beliefs were gradually falsified and were replaced with understandings based on accumulated and
reproducible evidence.[136] [137] Some scientists, such as Stephen Jay Gould,[138] consider science and religion to be
two compatible and complementary fields, with authorities in distinct areas of human experience, so-called
non-overlapping magisteria.[139] This view is also held by many theologians, who believe that ultimate origins and
meaning are addressed by religion, but favour verifiable scientific explanations of natural phenomena over those of
creationist beliefs. Other scientists, such as Richard Dawkins,[140] reject the non-overlapping magisteria and argue
that, in disproving literal interpretations of creationists, the scientific method also undermines religious texts as a
source of truth. Irrespective of this diversity in viewpoints, since creationist beliefs are not supported by empirical
evidence, the scientific consensus is that any attempt to teach creationism as science should be rejected.[141] [142]
[143]

Organizations

Intelligent design
Young Earth Creationism
• Access Research Network
• Answers in Genesis, a group promoting Young-Earth Creationism
• Center for Science and Culture
• Creation Ministries International, an organisation promoting biblical creation
• Institute for Creation Research, "a Christ-Focused Creation Ministry" Evolution
• Creation Research Society • TalkOrigins Archive
Old Earth Creationism • National Center for Science Education

• Reasons to Believe led by Hugh Ross

[144]
• Answers In Creation led by Greg Neyman
Creationism 399

See also
• Abiogenesis
• Biogenesis
• Biblical inerrancy
• Cosmological argument
• Flying Spaghetti Monster
• Teleological argument
• Watchmaker analogy

Notes on terminology
[1] Eugenie C. Scott (with forward by Niles Eldredge) (2004). Evolution vs. Creationism: An Introduction (http:/ / books. google. com/
?id=03b_a0monNYC& printsec=frontcover& dq=evolution+ vs. + creationism& q). Berkley & Los Angeles, California: University of
California Press. p. 114. ISBN 0-520-24650-0. . Retrieved 16 June 2010 Also: Westport, Connecticut: Greenwood Press. ISBN 0313321221
[2] "NCSE : National Center for Science Education - Defending the Teaching of Evolution in Public Schools." (http:/ / ncse. com/ creationism).
Creationism. 2008. . Retrieved 2009-06-22.
[3] Ronald L. Numbers. "The ‘Ordinary’ View of Creation" (http:/ / www. counterbalance. net/ history/ ordcreat-frame. html). Counterbalance
Meta-Library. . Retrieved 2010-08-11.
[4] Ronald L. Numbers. "Antievolutionists and Creationists" (http:/ / www. counterbalance. net/ history/ anticreat-frame. html). Creationism
History. Counterbalance Meta-Library. . Retrieved 2007-08-15.
[5] For example, the Scopes Trial of 1925 brought creationism and evolution into the adversarial environment of the American justice system.
The trial was well-publicized, and served as a catalyst for the wider creation–evolution controversy; Giberson & Yerxa (2002), pp. 3-4.
[6] Evolution's status as a "theory" has played a prominent role in the creation–evolution controversy. In scientific terminology, "theories are
structures of ideas that explain and interpret facts". It is understood, therefore, that "evolution is a fact and a theory". In contrast, when strict
creationists refer to evolution as a theory, they often mean to characterize evolution as an "imperfect fact", drawing upon the vernacular
conception of "theory" as "part of a hierarchy of confidence running downhill from fact to theory to hypothesis to guess"; Gould SJ (May
1981). Evolution as fact and theory (http:/ / www. stephenjaygould. org/ library/ gould_fact-and-theory. html). Retrieved 12 April 2010;
Moran L (2002). Evolution is a fact and a theory (http:/ / www. talkorigins. org/ faqs/ evolution-fact. html). Retrieved 12 April 2010. Original
work published 1993.
[7] Campbell D (2006, 21 February). "Academics fight rise of creationism at universities" (http:/ / www. guardian. co. uk/ world/ 2006/ feb/ 21/
religion. highereducation). The Guardian. Retrieved 07 April, 2010.
[8] For the biological understanding of complexity, see Evolution of complexity. For a creationist perspective, see Irreducible complexity.
[9] Ronald L. Numbers. "Creationism History: Topic Index" (http:/ / www. counterbalance. net/ history/ intro-frame. html). Counterbalance
Meta-Library. . Retrieved 2009-06-22.
[10] While the term myth is often used colloquially to refer to "a false story", this article uses the term in the academic meaning of "a sacred
narrative explaining how the world and mankind came to be in their present form" (Dundes A, 1996. "Madness in method plus a plea for
projective inversion in myth". In LL Patton & W Doniger (Eds.), Myth & method (http:/ / books. google. com/ books?id=OgsTmeRHpeUC&
printsec=frontcover& source=gbs_navlinks_s#v=onepage& q& f=false). Charlottesville: University Press of Virginia [pp. 147-162], p. 147).
[11] Dundes, Alan (Winter, 1997). "Binary Opposition in Myth: The Propp/Levi-Strauss Debate in Retrospect". Western Folklore (56): 39–50.
[12] Dundes, Alan (1984). Introduction. Sacred Narrative: Readings in the Theory of Myth. Ed. Alan Dunes.. University of California Press.
[13] Dundes, Alan (1996). "Madness in Method Plus a Plea for Projective Inversion in Myth". Myth and Method. Ed. Laurie Patton and Wendy
Doniger.. Charlottesville: University of Virginia Press.
[14] See, e.g., Corey MA (1993). "Making sense of the 'coincidences'". In MA Corey, God and the new cosmology: The anthropic design
argument (http:/ / books. google. com/ books?id=M8wYPYrKnHgC& printsec=frontcover#v=onepage& q& f=false) (pp. 157-174). Lanham,
MD: Rowman & Littlefield.
[15] Isaak, Mark (2004). "CA230: Interpretation and observation" (http:/ / www. talkorigins. org/ indexcc/ CA/ CA230. html). Index to
Creationist Claims. TalkOrigins Archive. . Retrieved 2009–08-20.
[16] Isaak, Mark (2005). "CA215: Practical uses of evolution." (http:/ / www. talkorigins. org/ indexcc/ CA/ CA215. html). Index to Creationist
Claims. TalkOrigins Archive. . Retrieved 2009–08-20.
Isaak, Mark (2005). "CH100.1: Science in light of Scripture" (http:/ / www. talkorigins. org/ indexcc/ CH/ CH100_1. html). Index to
Creationist Claims. TalkOrigins Archive. . Retrieved 2009–08-20.
[17] Isaak, Mark (2004). "CA301: Science and naturalism" (http:/ / www. talkorigins. org/ indexcc/ CA/ CA301. html). Index to Creationist
Claims. TalkOrigins Archive. . Retrieved 2009–08-20.
[18] "Statements from Scientific and Scholarly Organizations" (http:/ / ncse. com/ media/ voices/ science). National Center for Science
Education. . Retrieved 2008-08-28.
[19] Royal Society statement on evolution, creationism and intelligent design (http:/ / www. royalsoc. ac. uk/ news. asp?year=& id=4298)
Creationism 400

[20] National Association of Biology Teachers Statement on Teaching Evolution (http:/ / www. nabt. org/ sub/ position_statements/ evolution.
asp)
[21] IAP Statement on the Teaching of Evolution (http:/ / www. interacademies. net/ Object. File/ Master/ 6/ 150/ Evolution statement. pdf) Joint
statement issued by the national science academies of 67 countries, including the United Kingdom's Royal Society (PDF file)
[22] From the American Association for the Advancement of Science, the world's largest general scientific society: 2006 Statement on the
Teaching of Evolution (http:/ / www. aaas. org/ news/ releases/ 2006/ pdf/ 0219boardstatement. pdf)PDF (44.8 KB), AAAS Denounces
Anti-Evolution Laws (http:/ / www. aaas. org/ news/ releases/ 2006/ 0219boardstatement. shtml)
[23] " Creationism (http:/ / encarta. msn. com/ text_761580511___0/ Creationism. html)" Contributed By: Ronald L. Numbers, William
Coleman: Microsoft Encarta Online Encyclopedia 2007. Archived (http:/ / www. webcitation. org/ query?id=1257023127596318)
2009-10-31.
[24] Creationism/ID, A Short Legal History (http:/ / www. talkreason. org/ articles/ HistoryID. cfm) By Lenny Flank, Talk Reason
[25] Forster, Roger; Marston, Dr Paul (2001). "Chapter 7 - Genesis Through History" (http:/ / www. ivycottage. org/ group/ group.
aspx?id=6826). Reason Science and Faith. Chester, England: Monarch Books. ISBN 1854244418. . Retrieved 2007-06-30.
[26] The Works of Philo Judaeus (http:/ / www. earlychristianwritings. com/ yonge/ index-2. html), translated from the Greek by Charles Duke
Yonge:
Philo: Allegorical Interpretation, I (http:/ / www. earlychristianwritings. com/ yonge/ book2. html)
[27] Davis A. Young (1988). "The contemporary relevance of Augustine" (http:/ / www. asa3. org/ ASA/ PSCF/ 1988/ PSCF3-88Young. html).
Perspectives on Science and Christian Faith. . Retrieved 2008-08-18.
[28] Moore, James. "Evolution and Wonder - Understanding Charles Darwin" (http:/ / speakingoffaith. publicradio. org/ programs/ darwin/
transcript. shtml). Speaking of Faith (Radio Program). American Public Media. . Retrieved 2007-06-27.
[29] History of the Collapse of "Flood Geology" and a Young Earth (http:/ / www. bringyou. to/ apologetics/ p82. htm), adapted from The
Biblical Flood: A Case Study of the Church's Response to Extrabiblical Evidence (Eerdmans, 1995) by Davis A. Young. Retrieved
2007-06-30.
[30] Desmond, Adrian; Moore, James (1991). Darwin. London: Michael Joseph, Penguin Group. ISBN 0-7181-3430-3.
[31] "Letter 1919 — Darwin, C. R. to Hooker, J. D., 5 (July 1856)" (http:/ / www. darwinproject. ac. uk/ entry-1919). Darwin Correspondence
Project. . Retrieved 2010-08-11.
"Letter 4196 — Darwin, C. R. to Gray, Asa, 31 May (1863)" (http:/ / www. darwinproject. ac. uk/ entry-4196). Darwin Correspondence
Project. . Retrieved 2010-08-11.
[32] "Letter 4041 — Lyell, Charles to Darwin, C. R., 15 March 1863" (http:/ / www. darwinproject. ac. uk/ entry-4041). Darwin Correspondence
Project. . Retrieved 2010-08-11.
[33] Bowler 2003, p. 139
[34] Darwin and design: historical essay (http:/ / www. darwinproject. ac. uk/ content/ view/ 110/ 104/ ). Darwin Correspondence Project. 2007.
. Retrieved 2008-09-17.
[35] "Darwin Correspondence Project - Letter 2534 — Kingsley, Charles to Darwin, C. R., 18 November 1859" (http:/ / www. darwinproject. ac.
uk/ darwinletters/ calendar/ entry-2534. html). . Retrieved 2009-04-11.
[36] Quammen 2006, p. 119
[37] Moore 2006
[38] Barlow 1963, p.  207 (http:/ / darwin-online. org. uk/ content/ frameset?viewtype=text& itemID=F1577& pageseq=9).
[39] Dewey 1994, p. 27
[40] Miles 2001
[41] Gray, Asa (1860). "Natural Selection is not inconsistent with Natural Theology" (http:/ / www. darwinproject. ac. uk/ content/ view/ 84/ 69/
). Atlantic Monthly (Darwin Correspondence Project - Essay: Natural selection & natural theology). . Retrieved 2009-04-11.
[42] Bowler 2003, pp. 202–208
[43] Evolution Vs. Creationism, Eugenie Scott, Niles Eldredge, p62-63
[44] Albrecht Moritz (October 31, 2006). "The Origin of Life" (http:/ / www. talkorigins. org/ faqs/ abioprob/ originoflife. html#intro).
TalkOrigins Archive. . Retrieved 2008-11-22.
[45] Science, Religion, and Evolution (http:/ / ncse. com/ evolution/ education/ science-religion-evolution) by Eugenie Scott (accessed at
2007-07-09).
[46] Akin, Jimmy (January 2004). "Evolution and the Magisterium" (http:/ / www. catholic. com/ thisrock/ 2004/ 0401bt. asp). This Rock. .
Retrieved 2007-08-15.
[47] Jeff Severns Guntzel (2005). "National Catholic Reporter: Catholic schools steer clear of anti-evolution bias" (http:/ / www. findarticles.
com/ p/ articles/ mi_m1141/ is_21_41/ ai_n13592804/ print). National Catholic Reporter. . Retrieved 2007-08-15.
[48] Text of talk by Vatican Observatory director on ‘Science Does Not Need God. Or Does It? A Catholic Scientist Looks at Evolution’ -
Catholic Online (http:/ / www. catholic. org/ national/ national_story. php?id=18504)
[49] The Tower of Babel (http:/ / www. amazon. com/ gp/ product/ product-description/ 026216180X) by Robert T. Pennock, Naturalism is an
Essential Part of Science and Critical Inquiry (http:/ / www. freeinquiry. com/ naturalism. html) by Steven D. Schafersman, The Leiter Reports
(http:/ / webapp. utexas. edu/ blogs/ archives/ bleiter/ 001072. html), Report on "Naturalism, Theism and the Scientific Enterprise" conference
(http:/ / www. arn. org/ docs/ odesign/ od182/ ntse182. htm), The Oxford Handbook of Philosophy of Religion, 11: God, Science, and
Naturalism (http:/ / www. oxfordscholarship. com/ oso/ public/ content/ philosophy/ 0195138090/ acprof-0195138090-chapter-12. html) by
Creationism 401

Paul R. Draper, Philosophy Now: The Alleged Fallacies of Evolutionary Theory (http:/ / www. philosophynow. org/ issue46/ 46pigliucci.
htm), Statement on Intelligent Design (http:/ / www. biology. uiowa. edu/ ID. html), Science and fundamentalism (http:/ / www. nature. com/
embor/ journal/ v6/ n12/ full/ 7400589. html) by Massimo Pigliucci, Justifying Methodological Naturalism (http:/ / www. infidels. org/ library/
modern/ michael_martin/ naturalism. html) by Michael Martin (philosopher)
[50] Butterflies and wheels article (http:/ / www. butterfliesandwheels. com/ articleprint. php?num=158) by Raymond D. Bradley, Emeritus
Professor of Philosophy at the Simon Fraser University (New Zealand).
[51] s:Kitzmiller v. Dover Area School District/2:Context#Page 19 of 139
[52] Understanding the Intelligent Design Creationist Movement: Its True Nature and Goals. (http:/ / www. centerforinquiry. net/ uploads/
attachments/ Forrest_Paper. pdf)PDF (413 KB) A Position Paper from the Center for Inquiry, Office of Public Policy Barbara Forrest. May,
2007.
[53] TalkOrigins Archive: Post of the Month: March 2006 (http:/ / www. talkorigins. org/ origins/ postmonth/ mar06. html), The History of
Creationism by Lenny Flank.
[54] McLean v. Arkansas Board of Education (http:/ / www. talkorigins. org/ faqs/ mclean-v-arkansas. html), Decision January 5, 1982.
[55] Edwards v. Aguillard (http:/ / www. talkorigins. org/ faqs/ edwards-v-aguillard. html)
[56] Evolution News & Views: Dover Judge Regurgitates Mythological History of Intelligent Design (http:/ / www. evolutionnews. org/ 2005/
12/ post_6. html), Discovery Institute, Posted by Jonathan Witt on December 20, 2005 4:43 PM. Retrieved 2007-07-01
[57] Miller JD, Scott EC, Okamoto S (August 2006). "Science communication. Public acceptance of evolution". Science 313 (5788): 765–6.
doi:10.1126/science.1126746. PMID 16902112.
[58] ITL: Jesus and the Indian Messiah - Every Wind of Doctrine (http:/ / textonly. itl-usa. org/ ahmadi/ ahmadi13. html)
[59] http:/ / textonly. itl-usa. org/ ahmadi/ ahmadi13. html
[60] http:/ / www. alislam. org/ library/ articles/ Guided_evolution_and_punctuated_equilibrium-20081104MN. pdf
[61] Matthews, Gary L. (2005). The Challenge of Baha'u'llah (http:/ / books. google. com/ ?id=EGbZMLCmE1IC& lpg=PA90&
pg=PA90#v=onepage& q). US Baha'i Publishing Trust. pp. 90–5. ISBN 9781931847162. .
[62] Brown, Keven; Von Kitzing, Eberhard, eds (2001). Evolution and Bahá'í belief: ʻAbduʾl-Bahá's response to nineteenth-century Darwinism;
Volume 12 of Studies in the Bábí and Bahá'í religions (http:/ / books. google. com/ ?id=egDAfpkONRsC). Kalimat Press. pp. 6, 17, 117, etc..
ISBN 9781890688080. .
[63] "Denominational Views" (http:/ / ncse. com/ religion/ denominational-views). National Center for Science Education. October 17, 2008. .
Retrieved 2010-05-17.
[64] "Episcopal Church, General Convention (2006)" (http:/ / ncse. com/ media/ voices/ episcopal-church-general-convention-2006). National
Center for Science Education. . Retrieved 2010-05-17.
[65] Edwin A. Schick (1965). "Lutheran World Federation" (http:/ / ncse. com/ media/ voices/ lutheran-world-federation). "Evolution", in The
Encyclopedia of the Lutheran Church. National Center for Science Education. . Retrieved 2010-05-17.
Allen R. Utke; Patrick Russell (October 2006). "'God allows the universe to create itself and evolve'" (http:/ / www. thelutheran. org/ article/
article_buy. cfm?article_id=6093). The Lutheran. . Retrieved 2010-05-17. "The Lutheran is the magazine of the Evangelical Lutheran Church
in America"
[66] Archbishop of Canterbury, Transcript of interview with the Guardian (http:/ / www. archbishopofcanterbury. org/ 354)
[67] Archbishop of Canterbury backs evolution: Well, he is a Primate, Chris Williams, The Register, Tuesday 21 March 2006 (http:/ / www.
theregister. co. uk/ 2006/ 03/ 21/ archbishop_backs_evolution/ )
[68] What Catholics Think of Evolution? They don't not believe in it (http:/ / slate. com/ id/ 2122506/ ), Keelin McDonell, Explainer, Slate
Magazine, July 12, 2005.
[69] See also the article Evolution and the Roman Catholic Church.
[70] see eg John Polkinghorne's Science and Theology pp6-7
[71] The Works of Philo Judaeus, Chapter 2, translated by Charles Duke Yonge (http:/ / www. earlychristianwritings. com/ yonge/ book2. html)
[72] ASA3.org (http:/ / www. asa3. org/ ASA/ topics/ Bible-Science/ PSCF3-88Young. html), Davis A. Young, "The Contemporary Relevance
of Augustine's View of Creation" (From: Perspectives on Science and Christian Faith 40.1:42-45 (3/1988)), The American Scientific
Affiliation
[73] Pugh Forum findings Page 95 (http:/ / religions. pewforum. org/ pdf/ report2religious-landscape-study-chapter-2. pdf)
[74] Wayne Jackson. "Are There Two Creation Accounts in Genesis?" (http:/ / www. apologeticspress. org/ articles/ 2194). . Retrieved
2007-05-23.
[75] "The Creation Myths: Internal Difficulties" (http:/ / www. geocities. com/ paulntobin/ creationint. html). . Retrieved 2007-05-23.
[76] The Creation/Evolution Continuum (http:/ / ncse. com/ creationism/ general/ creationevolution-continuum), Eugenie Scott, NCSE Reports,
v. 19, n. 4, p. 16-17, 23-25, July/August, 1999.
[77] Wise, D.U., 2001, Creationism's Propaganda Assault on Deep Time and Evolution, Journal of Geoscience Education, v. 49, n. 1, p. 30-35.
[78] Who Believes What? Clearing up Confusion over Intelligent Design and Young-Earth Creationism (http:/ / nagt. org/ files/ nagt/ jge/
abstracts/ Ross_v53n3p319. pdf), Marcus R. Ross, Journal of Geoscience Education, v. 53, n. 3, May, 2005, p. 319-323
[79] Gosse, Henry Philip, 1857. Omphalos: An Attempt to Untie the Geological Knot. J. Van Voorst, London
[80] "The Holy Bible, King James Version" (http:/ / www. biblegateway. com/ passage/ ?book_id=68& chapter=3& version=9). . Retrieved
2006-12-31.
Creationism 402

[81] "Top Questions-1.What is the theory of intelligent design?" (http:/ / www. discovery. org/ csc/ topQuestions.
php#questionsAboutIntelligentDesign). Discovery Institute. . Retrieved 2007-05-13.
[82] Kitzmiller v. Dover Testimony (http:/ / www. talkorigins. org/ faqs/ dover/ day6pm. html), Barbara Forrest, 2005.
[83] Wedge Strategy (http:/ / www. antievolution. org/ features/ wedge. pdf), Discovery Institute, 1999.
[84] "for most members of the mainstream scientific community, ID is not a scientific theory, but a creationist pseudoscience." Trojan Horse or
Legitimate Science: Deconstructing the Debate over Intelligent Design (http:/ / www. hcs. harvard. edu/ ~hsr/ fall2005/ mu. pdf), David Mu,
Harvard Science Review, Volume 19, Issue 1, Fall 2005.
"Creationists are repackaging their message as the pseudoscience of intelligent design theory." Professional Ethics Report (http:/ / www. aaas.
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[85] The Creationists: From Scientific Creationism to Intelligent Design, Expanded Edition, Ronald L. Numbers, Harvard University Press,
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[86] Forrest, Barbara (May,2007) (PDF). Understanding the Intelligent Design Creationist Movement: Its True Nature and Goals. A Position
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[87] "Dembski chides me for never using the term "intelligent design" without conjoining it to "creationism." He implies (though never explicitly
asserts) that he and others in his movement are not creationists and that it is incorrect to discuss them in such terms, suggesting that doing so
is merely a rhetorical ploy to "rally the troops". (2) Am I (and the many others who see Dembski's movement in the same way)
misrepresenting their position? The basic notion of creationism is the rejection of biological evolution in favor of special creation, where the
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[89] Intelligent design not science: experts (http:/ / www. smh. com. au/ news/ national/ intelligent-design-not-science-experts/ 2005/ 10/ 20/
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[90] Full text of Judge Jones' ruling, dated December 20, 2005
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[100] Judaism and Evolution (http:/ / www. jewishvirtuallibrary. org/ jsource/ Judaism/ jewsevolution. html), Jewish Virtual Library
[101] Aviezer, Nathan. In the Beginning: Biblical Creation and Science. Ktav, 1990. Hardcover. ISBN 0-88125-328-6
[102] Carmell, Aryeh and Domb, Cyril, eds. Challenge: Torah Views on Science New York: Association of Orthodox Jewish Scientists/Feldheim
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[103] Schroeder, Gerald L. The Science of God: The Convergence of Scientific and Biblical Wisdom Broadway Books, 1998, ISBN
0-7679-0303-X
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[111] "Britons unconvinced on evolution" (http:/ / news. bbc. co. uk/ 2/ hi/ science/ nature/ 4648598. stm), BBC News, 26 January 2006
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[114] Italy Keeps Darwin in its Classrooms (http:/ / www. dw-world. de/ dw/ article/ 0,2144,1188423,00. html), Deutsche Welle, 3 May 2004
[115] In the beginning: The debate over creation and evolution, once most conspicuous in America, is fast going global (http:/ / www.
economist. com/ world/ displaystory. cfm?story_id=9036706), ISTANBUL, MOSCOW AND ROME, Evolution and religion, The Economist,
April 19th 2007.
[116] The dangers of creationism in education (http:/ / assembly. coe. int/ main. asp?Link=/ documents/ workingdocs/ doc07/ edoc11297. htm),
Committee on Culture, Science and Education, Rapporteur: Mr Guy LENGAGNE, France, Socialist Group, Doc. 11297, Parliamentary
Assemble Council of Europe, June 8, 2007.
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[118] "Darwin is off the curriculum for Serbian schools" (http:/ / www. telegraph. co. uk/ news/ 1471367/
Darwin-is-off-the-curriculum-for-Serbian-schools. html), telegraph.co.uk, 9 September 2004
[119] "Serbia reverses Darwin suspension" (http:/ / news. bbc. co. uk/ 2/ hi/ europe/ 3642460. stm), BBC News, 9 September 2004
[120] "'Anti-Darwin' Serb minister quits" (http:/ / news. bbc. co. uk/ 2/ hi/ europe/ 3663196. stm), BBC News, 16 September 2004
[121] " And finally... (http:/ / www. wbj. pl/ ?command=article& id=35336& type=wbj)", Warsaw Business Journal, 18 December 2006
[122] Majority of Americans Doubt Theory of Evolution (http:/ / www. gallup. com/ poll/ 14107/
Third-Americans-Say-Evidence-Has-Supported-Darwins-Evolution-Theory. aspx)
[123] Substantial Numbers of Americans Continue to Doubt Evolution as Explanation for Origin of Humans (http:/ / www. unl. edu/ rhames/
courses/ current/ creation/ evol-poll. htm)
[124] Frank Newport, "Evolution Beliefs." (http:/ / www. gallup. com/ video/ 27838/ Evolution-Beliefs. aspx) Gallup Organization, June 11,
2007.
[125] "Public beliefs about evolution and creation." (http:/ / www. religioustolerance. org/ ev_publi. htm) From: religioustolerance.org. Retrieved
on November 11, 2007.
[126] "Keeping God Out of the Classroom". Newsweek. June 29, 1987. p. 23.
[127] US poll results - "Public beliefs about evolution and creation", religioustolerance.org (http:/ / www. religioustolerance. org/ ev_publi. htm)
[128] Evolution and Creationism In Public Education: An In-depth Reading Of Public Opinion (http:/ / media. pfaw. org/ pdf/ creationism/
creationism-poll. pdf)PDF (481 KB)
[129] "Statement on the Teaching of Evolution" (http:/ / www. aaas. org/ news/ releases/ 2006/ pdf/ 0219boardstatement. pdf) (PDF). American
Association for the Advancement of Science. 2006. . Retrieved 2007-03-20.
[130] "99.9 percent of scientists accept evolution" Finding the Evolution in Medicine (http:/ / www. nih. gov/ nihrecord/ 07_28_2006/ story03.
htm) National Institutes of Health
[131] National Center for Science Education: Statements from Religious Organizations (http:/ / ncse. com/ media/ voices/ religion)
[132] Murphy, George L., 2002, "Intelligent Design as a Theological Problem," in Covalence: the Bulletin of the Evangelical Lutheran Church in
America Alliance for Faith, Science, and Technology
[133] The Guardian, Archbishop: Stop teaching creationism, Williams backs science over Bible (http:/ / www. guardian. co. uk/ religion/ Story/
0,,1735730,00. html) See transcript of Guardian interview for primary source
[134] "American Academy of Religion on teaching creationism" (http:/ / ncse. com/ news/ 2010/ 07/
american-academy-religion-teaching-creationism-005712). National Center for Science Education. July 23, 2010. . Retrieved 2010-08-09.
[135] Committee on Revising Science and Creationism: A View from the National Academy of Sciences, National Academy of Sciences and
Institute of Medicine of the National Academies (2008). Science, Evolution, and Creationism (http:/ / www. nap. edu/ catalog/ 11876. html)
(free pdf download ed.). Washington, D.C.: National Academies Press. pp. 10–12. ISBN 0-309-10586-2. . Retrieved 2008-10-27. "In science,
explanations must be based on naturally occurring phenomena. Natural causes are, in principle, reproducible and therefore can be checked
independently by others. If explanations are based on purported forces that are outside of nature, scientists have no way of either confirming or
disproving those explanations."
[136] "An Index to Creationist Claims" (http:/ / www. talkorigins. org/ indexcc/ index. html). . Retrieved 2008-08-12.
[137] Futuyma, Douglas J.. "Evolutionary Science, Creationism, and Society" (http:/ / www. biologi. kva. se/ arkiv/ FutuymaCh22final. pdf)
(PDF). "Evolution" (2005). . Retrieved 2008-08-12.
[138] Gould, S. J. (2002). Rocks of Ages: Science and Religion in the Fullness of Life. New York: Ballantine Books.
[139] Gould, Stephen Jay (1997). "Nonoverlapping Magisteria" (http:/ / www. stephenjaygould. org/ library/ gould_noma. html). Natural History
106 (3): 16–22. .
[140] Dawkins, Richard (2006). The God Delusion. Transworld Publishers. p. 5. ISBN 0-5930-5548-9.
Creationism 404

[141] "Royal Society statement on evolution, creationism and intelligent design" (http:/ / www. royalsoc. ac. uk/ news. asp?year=& id=4298).
The Royal Society. 2006-04-11. . Retrieved 2007-04-23.
[142] Matsumura, Molleen; Mead, Louise (2007-07-31). "10 Significant Court Decisions Regarding Evolution/Creationism" (http:/ / ncse. com/
taking-action/ ten-major-court-cases-evolution-creationism). National Center for Science Education. . Retrieved 2008-11-04.
[143] Myers, PZ (2006-02-15). "Ann Coulter: No Evidence for Evolution?" (http:/ / scienceblogs. com/ pharyngula/ 2006/ 06/
ann_coulter_no_evidence_for_ev. php). Pharyngula (ScienceBlogs). . Retrieved 2007-09-12.
[144] Answers In Creation (http:/ / www. answersincreation. org)

Notes

References
• "Darwin's Ornithological Notes" (http://darwin-online.org.uk/content/frameset?viewtype=text&
itemID=F1577&pageseq=1). Bulletin of the British Museum (Natural History) Historical Series 2 (No. 7):
pp. 201–278. 1963. Retrieved 2009-06-10.
• Bowler, Peter J. (2003). Evolution: The History of an Idea (3rd ed.). University of California Press.
ISBN 0-520-23693-9.
• Darwin, Charles (1958). Barlow, Nora. ed. [[The Autobiography of Charles Darwin (http://darwin-online.org.
uk/EditorialIntroductions/Freeman_LifeandLettersandAutobiography.html)] 1809–1882. With the Original
Omissions Restored. Edited and with Appendix and Notes by his Granddaughter Nora Barlow]. London: Collins.
Retrieved 2009-01-09.
• Desmond, Adrian (1989). The Politics of Evolution: Morphology, Medicine, and Reform in Radical London.
Chicago: University of Chicago Press. ISBN 0-226-14374-0.
• Desmond, Adrian; Moore, James (1991). Darwin. London: Michael Joseph, Penguin Group.
ISBN 0-7181-3430-3.
• Dewey, John (1994). "The Influence of Darwinism on Philosophy". In Martin Gardner. Great Essays in Science.
Prometheus Books. ISBN 0-87975-853-8.
• Forster, Roger; Marston, Dr Paul (1999). "Genesis Through History" (http://www.ivycottage.org/group/group.
aspx?id=6826). Reason Science and Faith (Ivy Cottage: E-Books ed.). Chester, England: Monarch Books.
ISBN 1-85424-441-8. Retrieved 2009-03-24.
• Hayward, James L. (1998). The Creation/Evolution Controversy: an annotated bibliography. Scarecrow
Press/Salem Press. pp. 253. ISBN 0-8108-3386-7.
• Miles, Sara Joan (2001). "Charles Darwin and Asa Gray Discuss Teleology and Design" (http://www.asa3.org/
ASA/PSCF/2001/PSCF9-01Miles.html). Perspectives on Science and Christian Faith 53: pp. 196–201.
Retrieved 2008-11-22.
• Moore, James (2006). Evolution and Wonder - Understanding Charles Darwin (http://speakingoffaith.
publicradio.org/programs/darwin/transcript.shtml). Speaking of Faith (Radio Program). American Public
Media. Retrieved 2008-11-22.
• Quammen, David (2006). The Reluctant Mr. Darwin. New York: Atlas Books. ISBN 0-393-05981-2.
• Secord, James A. (2000). Victorian Sensation: The Extraordinary Publication, Reception, and Secret Authorship
of Vestiges of the Natural History of Creation. Chicago: University of Chicago Press. ISBN 0-226-74411-6.
Creationism 405

Further reading
• Adams Leeming, David (1996). A Dictionary of Creation Myths. OUP. ISBN 978-0195102758.
• Anderson, Bernhard W. (editor) Creation in the Old Testament (ISBN 0-8006-1768-1)
• Anderson, Bernhard W. Creation Versus Chaos: The Reinterpretation of Mythical Symbolism in the Bible (ISBN
1-59752-042-X)
• Ian Barbour When Science Meets Religion, 2000, Harper SanFrancisco
• Ian Barbour Religion and Science: Historical and Contemporary Issues, 1997, Harper SanFrancisco.
• Stephen Jay Gould Rocks of Ages: Science and Religion in the fullness of life, Ballantine Books, 1999
• Aryeh Kaplan, Immortality, Resurrection, and the Age of the Universe: A Kabbalistic View, Ktav, NJ, in
association with the Association of Orthodox Jewish Scientists, NY, 1993
• Stuart Kauffman Reinventing the Sacred, 2008
• Numbers, Ronald (November 30, 2006). The Creationists: From Scientific Creationism to Intelligent Design,
Expanded Edition. Harvard University Press. ISBN 0674023390.
• Joel R. Primack and Nancy Ellen Abrams In a Beginning...: Quantum Cosmology and Kabbalah, Tikkun, Vol. 10,
No. 1, pp. 66–73

External links
• The Edinburgh Creation Group (http://edinburghcreationgroup.org/) This site features many videos bringing a
Creationist perspective.
• Creationism (Stanford Encyclopedia of Philosophy) (http://plato.stanford.edu/entries/creationism/) by
Michael Ruse
• HowStuffWorks: How creationism works (http://www.howstuffworks.com/creationism.htm)
• Harun Yahya (http://www.harunyahya.com), Muslim creationist web site
• Darwinism Refuted (http://www.darwinismrefuted.com) based on Harun Yahya's writings
• Can Creation and Evolution Both Be True? | epologetics (http://epologetics.org/creationevolutionboth.php)
Examines whether Biblical creation and neo-darwinistic evolution can be reconciled.
• Evolution, Creationism & ID Timeline (http://www.allviewpoints.org/RESOURCES/EVOLUTION/timeline.
htm) Focuses on major historical and recent events in the scientific and political debate
• Evolution and Creationism (http://images.derstandard.at/20051012/Evolution-and-Creationism.
pdf)PDF (204 KB). A Guide for Museum Docents
• What is creationism? (http://www.talkorigins.org/faqs/wic.html) from talk.origins
• The Creation/Evolution Continuum (http://ncse.com/creationism/general/creationevolution-continuum) by
Eugenie Scott.
• Armies of the Night (http://www.stephenjaygould.org/ctrl/azimov_creationism.html) by Isaac Asimov.
• Workers have stake in defending science (http://www.themilitant.com/2005/6935/693551.html) a materialist
statement on creationism by The Militant, 2005.
• Edward J. Larson and Larry Witham Leading scientists still reject God in Nature, Vol. 394, No. 6691 (1998),
p. 313. Online at Freethought-web.org (http://www.freethought-web.org/ctrl/news/file002.html)
• Creationism: The Hindu View (http://www.talkorigins.org/faqs/mom/groves.html) from talk.origins
• 15 Answers to Creationist Nonsense (http://www.sciam.com/article.cfm?id=15-answers-to-creationist) from
Scientific American
Intelligent design 406

Intelligent design
For the philosophical "argument from design", see Teleological argument.
Intelligent design is the proposition that "certain features of the universe and of living things are best explained by
an intelligent cause, not an undirected process such as natural selection."[1] [2] It is a form of creationism and a
contemporary adaptation of the traditional teleological argument for the existence of God, but one which deliberately
avoids specifying the nature or identity of the designer.[3] Its leading proponents—all of whom are associated with
the Discovery Institute, a politically conservative think tank[4] [5] —believe the designer to be the God of
Christianity.[6] [7]
Intelligent design was developed by a group of American creationists who revised their argument in the
creation–evolution controversy to circumvent court rulings that prohibit the teaching of creationism as science.[8] [9]
[10]
Proponents argue that intelligent design is a scientific theory.[1] In so doing, they seek to fundamentally redefine
science to include supernatural explanations.[11] The overwhelming consensus in the scientific community is that
intelligent design is not science,[12] [13] [14] [15] and indeed is pseudoscience.[16] [17] [18]
Intelligent design originated in response to the United States Supreme Court Edwards v. Aguillard ruling, which
barred the teaching of "creation science" in public schools as breaching the separation of church and state.[8] The
first significant published use of intelligent design was in Of Pandas and People, a 1989 textbook intended for
high-school biology classes.[19] From the mid-1990s, intelligent design proponents were supported by the Discovery
Institute which, together with its Center for Science and Culture, planned and funded the "intelligent design
movement".[20] [4] They advocated inclusion of intelligent design in public school curricula, leading to the 2005
Kitzmiller v. Dover Area School District trial, where U.S. District Judge John E. Jones III ruled that intelligent
design is not science, that it "cannot uncouple itself from its creationist, and thus religious, antecedents", and that the
school district's promotion of it therefore violated the Establishment Clause of the First Amendment to the U.S.
Constitution.[21]
Intelligent design 407

History

Origin of the concept

Whether the order and complexity of nature indicates purposeful design has
been the subject of debate since the Greeks. In the 4th century BCE, Plato
posited a good and wise "demiurge" as the creator and first cause of the
cosmos in his Timaeus.[22] In his Metaphysics, Aristotle developed the idea
of an "Unmoved Mover".[23] [24] In De Natura Deorum (On the Nature of
the Gods, 45 BCE) Cicero wrote that "the divine power is to be found in a
principle of reason which pervades the whole of nature."[25] This line of
reasoning has come to be known as the teleological argument for the
existence of God. Some well-known forms of it were expressed in the 13th
century by Thomas Aquinas and in the 19th century by William Paley.
Aquinas, in his Summa Theologiae, used the concept of design in his "fifth
proof" for God's existence.[26]

In the early 19th century, Paley's argument from design in Natural

Theology (1802), used the watchmaker analogy,[27] and such arguments led
to the development of what was called natural theology, the study of nature
A marble bust based on a portrait ca. 370
as way of understanding "the mind of God". This movement fueled the BC of Plato. The teleological argument, or
passion for collecting fossils and other biological specimens, which "argument from design", is an ancient one,
ultimately led to Charles Darwin's On the Origin of Species (1859). Similar held in some form by Plato and Aristotle.

reasoning postulating a divine designer is embraced today by many

believers in theistic evolution, who consider modern science and the theory of evolution to be compatible with the
concept of a supernatural designer. In correspondence about the question with Asa Gray, Darwin wrote that "I cannot
honestly go as far as you do about Design. I am conscious that I am in an utterly hopeless muddle. I cannot think that
the world, as we see it, is the result of chance; & yet I cannot look at each separate thing as the result of Design."[28]
Though he had studied Paley's work while at university, by the end of his life he came to regard it as useless for
scientific development.[29]

Intelligent design in the late 20th and early 21st century is a development of natural theology that seeks to change the
basis of science and undermine evolutionary theory.[30] As evolutionary theory expanded to explain more
phenomena, the examples held up as evidence of design changed, though the essential argument remains the same:
complex systems imply a designer. Past examples have included the eye and the feathered wing; current examples
are typically biochemical: protein functions, blood clotting, and bacterial flagella; see irreducible complexity.
Philosopher Barbara Forrest writes that the intelligent design movement began in 1984 with the publication by Jon
A. Buell's the Foundation for Thought and Ethics of The Mystery of Life's Origin by Charles B. Thaxton, a chemist
and creationist. Thaxton held a conference in 1988, "Sources of Information Content in DNA," which attracted
creationists such as Stephen C. Meyer. Forrest writes that, in December 1988, Thaxton decided to use the term
"intelligent design," instead of creationism, for the movement.[31]
In March 1986 a review by Meyer used information theory to suggest that messages transmitted by DNA in the cell
show "specified complexity" specified by intelligence, and must have originated with an intelligent agent.[32] In
November of that year Thaxton described his reasoning as a more sophisticated form of Paley's argument from
design.[33] At the Sources of Information Content in DNA conference in 1988 he said that his intelligent cause view
was compatible with both metaphysical naturalism and supernaturalism,[34]
Intelligent design avoids identifying or naming the agent of creation—it merely states that one (or more) must
exist—but leaders of the movement have said the designer is the Christian God.[6] [7] [35] [36] [37] Whether this lack of
Intelligent design 408

specificity about the designer's identity in public discussions is a genuine feature of the concept, or just a posture
taken to avoid alienating those who would separate religion from the teaching of science, has been a matter of great
debate between supporters and critics of intelligent design. The Kitzmiller v. Dover Area School District court ruling
held the latter to be the case.

Origin of the term

The phrase "intelligent design" can be found in an 1847 issue of Scientific
American,[39] in an 1850 book by Patrick Edward Dove,[40] and in an 1861
letter from Charles Darwin.[41] The Paleyite botanist George James Allman
used the phrase in an address to the 1873 annual meeting of the British
Association for the Advancement of Science:
"No physical hypothesis founded on any indisputable fact has
yet explained the origin of the primordial protoplasm, and,
above all, of its marvellous properties, which render evolution
possible—in heredity and in adaptability, for these properties
are the cause and not the effect of evolution. For the cause of
this cause we have sought in vain among the physical forces
which surround us, until we are at last compelled to rest upon
an independent volition, a far-seeing intelligent design."[42] Of Pandas and People was the first modern
intelligent design book. Rethinking Schools
The phrase can be found again in Humanism, a 1903 book by one of the magazine characterizes it as a "creationist
founders of classical pragmatism, F.C.S. Schiller: "It will not be possible to treatise dressed up to look like a legitimate
[38]
rule out the supposition that the process of evolution may be guided by an discussion of science".

intelligent design". A derivative of the phrase appears in the Macmillan

Encyclopedia of Philosophy (1967) in the article titled, "Teleological argument for the existence of God": "Stated
most succinctly, the argument runs: The world exhibits teleological order (design, adaptation). Therefore, it was
produced by an intelligent designer".[43] Robert Nozick (1974) wrote: "Consider now complicated patterns which
one would have thought would arise only through intelligent design".[44] The phrases "intelligent design" and
"intelligently designed" were used in a 1979 philosophy book Chance or Design? by James Horigan[45] and the
phrase "intelligent design" was used in a 1982 speech by Sir Fred Hoyle in his promotion of panspermia.[46]
Intelligent design 409

The modern use of the words "intelligent

design", as a term intended to describe a
field of inquiry, began after the Supreme
Court of the United States, in the case of
Edwards v. Aguillard (1987), ruled that
creationism is unconstitutional in public
school science curricula. A Discovery
Institute report says that Charles Thaxton,
editor of Of Pandas and People, had picked
the phrase up from a NASA scientist, and
thought "That's just what I need, it's a good
engineering term".[48] In drafts of the book
over one hundred uses of the root word
"creation", such as "creationism" and
"creation science", were changed, almost
Use of the terms "creationism" versus "intelligent design" in sequential drafts of without exception, to "intelligent
[47] [19]
the book Of Pandas and People design", while "creationists" was
changed to "design proponents" or, in one
instance, "cdesign proponentsists". [sic][47] In June 1988 Thaxton held a conference titled "Sources of Information
Content in DNA" in Tacoma, Washington,[34] and in December decided to use the label "intelligent design" for his
new creationist movement.[49] Stephen C. Meyer was at the conference, and later recalled that "the term came
up".[50]

Of Pandas and People was published in 1989, and was the first book to make frequent use of the phrases "intelligent
design," "design proponents," and "design theory", thus representing the beginning of the modern "intelligent
design" movement.[51] "Intelligent design” was the most prominent of around fifteen new terms it introduced as a
new lexicon of creationist terminology to oppose evolution without using religious language.[52] It was the first place
where the phrase "intelligent design" appeared in its present use, as stated both by its publisher Jon Buell,[53] [54] and
by William A. Dembski in his expert witness report.[55] The book presented all of the basic arguments of intelligent
design proponents before any research had been done to support these arguments, and was actively promoted by
creationists for public school use.[51] Rethinking Schools magazine has criticized the book, saying it was a
"creationist treatise" packaged to look like a high quality science textbook, with a "glossy cover, full-color
illustrations, and chapter titles such as 'Homology' and 'Genetics and Macroevolution'", with numerous
"professionally prepared charts and illustrations appear to show how concrete scientific evidence supports the
existence of the unnamed 'designer'". Philosopher of science Michael Ruse believes the contents were "worthless and
dishonest", and it was described by an ACLU lawyer as a political tool aimed at students who did not "know science
or understand the controversy over evolution and creationism".[38]
Intelligent design 410

Integral concepts

Irreducible complexity
The term "irreducible complexity" was introduced by biochemist
Michael Behe in his 1996 book Darwin's Black Box, though he had
already described the concept in his contributions to the 1993 revised
edition of Of Pandas and People.[51] Behe defines it as "a single
system which is composed of several well-matched interacting parts
that contribute to the basic function, wherein the removal of any one of
the parts causes the system to effectively cease functioning".[56]

Behe uses the analogy of a mousetrap to illustrate this concept. A

The concept of irreducible complexity was
mousetrap consists of several interacting pieces—the base, the catch, popularised by Michael Behe, in his 1996 book,
the spring and the hammer—all of which must be in place for the Darwin's Black Box.
mousetrap to work. Removal of any one piece destroys the function of
the mousetrap. Intelligent design advocates assert that natural selection could not create irreducibly complex
systems, because the selectable function is present only when all parts are assembled. Behe argued that irreducibly
complex biological mechanisms include the bacterial flagellum of E. coli, the blood clotting cascade, cilia, and the
adaptive immune system.[57] [58]

Critics point out that the irreducible complexity argument assumes that the necessary parts of a system have always
been necessary and therefore could not have been added sequentially.[59] [60] They argue that something which is at
first merely advantageous can later become necessary as other components change. Furthermore, they argue,
evolution often proceeds by altering preexisting parts or by removing them from a system, rather than by adding
them. This is sometimes called the "scaffolding objection" by an analogy with scaffolding, which can support an
"irreducibly complex" building until it is complete and able to stand on its own.[61] Behe has acknowledged using
"sloppy prose", and that his "argument against Darwinism does not add up to a logical proof".[62] Irreducible
complexity has remained a popular argument among advocates of intelligent design; in the Dover trial, the court held
that "Professor Behe's claim for irreducible complexity has been refuted in peer-reviewed research papers and has
been rejected by the scientific community at large".[63]

Specified complexity
In 1986 the creationist chemist Charles Thaxton used the term "specified complexity" from information theory when
claiming that messages transmitted by DNA in the cell were specified by intelligence, and must have originated with
an intelligent agent.[32] The intelligent design concept of "specified complexity" was developed in the 1990s by
mathematician, philosopher, and theologian William Dembski. Dembski states that when something exhibits
specified complexity (i.e., is both complex and "specified", simultaneously), one can infer that it was produced by an
intelligent cause (i.e., that it was designed) rather than being the result of natural processes. He provides the
following examples: "A single letter of the alphabet is specified without being complex. A long sentence of random
letters is complex without being specified. A Shakespearean sonnet is both complex and specified".[64] He states that
details of living things can be similarly characterized, especially the "patterns" of molecular sequences in functional
biological molecules such as DNA.
Intelligent design 411

Dembski defines complex specified information (CSI) as anything with a less

than 1 in 10150 chance of occurring by (natural) chance. Critics say that this
renders the argument a tautology: complex specified information cannot occur
naturally because Dembski has defined it thus, so the real question becomes
whether or not CSI actually exists in nature.[66] [67] [68]
The conceptual soundness of Dembski's specified complexity/CSI argument has
been widely discredited by the scientific and mathematical communities.[69] [70]
[71]
Specified complexity has yet to be shown to have wide applications in other
fields as Dembski asserts. John Wilkins and Wesley Elsberry characterize
Dembski's "explanatory filter" as eliminative, because it eliminates explanations
William Dembski proposed the sequentially: first regularity, then chance, finally defaulting to design. They
[65]
concept of specified complexity. argue that this procedure is flawed as a model for scientific inference because
the asymmetric way it treats the different possible explanations renders it prone
to making false conclusions.[72]

Richard Dawkins, another critic of intelligent design, argues in The God Delusion that allowing for an intelligent
designer to account for unlikely complexity only postpones the problem, as such a designer would need to be at least
as complex.[73] Other scientists have argued that evolution through selection is better able to explain the observed
complexity, as is evident from the use of selective evolution to design certain electronic, aeronautic and automotive
systems which are considered problems too complex for human "intelligent designers".[74]

Fine-tuned Universe
Intelligent design proponents have also occasionally appealed to broader teleological arguments outside of biology,
most notably an argument based on the fine-tuning of universal constants that make matter and life possible and
which are argued not to be solely attributable to chance. These include the values of fundamental physical constants,
the relative strength of nuclear forces, electromagnetism, and gravity between fundamental particles, as well as the
ratios of masses of such particles. Intelligent design proponent and Center for Science and Culture fellow Guillermo
Gonzalez argues that if any of these values were even slightly different, the universe would be dramatically different,
making it impossible for many chemical elements and features of the Universe, such as galaxies, to form.[75] Thus,
proponents argue, an intelligent designer of life was needed to ensure that the requisite features were present to
achieve that particular outcome.
Scientists have generally responded that this argument cannot be tested and is therefore not science but metaphysics.
Some scientists argue that even when taken as mere speculation, these arguments are poorly supported by existing
evidence.[76] Victor J. Stenger and other critics say both intelligent design and the weak form of the anthropic
principle are essentially a tautology; in his view, these arguments amount to the claim that life is able to exist
because the Universe is able to support life.[77] [78] [79] The claim of the improbability of a life-supporting universe
has also been criticized as an argument by lack of imagination for assuming no other forms of life are possible. Life
as we know it might not exist if things were different, but a different sort of life might exist in its place. A number of
critics also suggest that many of the stated variables appear to be interconnected and that calculations made by
mathematicians and physicists suggest that the emergence of a universe similar to ours is quite probable.[80]
Proponent Granville Sewell argues that the evolution of complex forms of life represents a decrease of entropy, and
that it thus violates the second law of thermodynamics and so supports intelligent design.[81] This, however, is a
misapplication of thermodynamic principles.[82] The second law applies to closed systems only. If Granville's
argument were valid, living things could not be born and grow, as this also would be a decrease in entropy. Neither
evolution nor the growth of living things violates the second law of thermodynamics because living things are not
closed systems—they have external energy sources (e.g. food, oxygen, sunlight) whose production requires an
offsetting net increase in entropy.
Intelligent design 412

Intelligent designer
Intelligent design arguments are formulated in secular terms and intentionally avoid identifying the intelligent agent
(or agents) they posit. Although they do not state that God is the designer, the designer is often implicitly
hypothesized to have intervened in a way that only a god could intervene. Dembski, in The Design Inference,
speculates that an alien culture could fulfill these requirements. The authoritative description of intelligent design,[83]
however, explicitly states that the Universe displays features of having been designed. Acknowledging the paradox,
Dembski concludes that "no intelligent agent who is strictly physical could have presided over the origin of the
universe or the origin of life".[84] The leading proponents have made statements to their supporters that they believe
the designer to be the Christian God, to the exclusion of all other religions.[6] [7] [35]
Beyond the debate over whether intelligent design is scientific, a number of critics argue that existing evidence
makes the design hypothesis appear unlikely, irrespective of its status in the world of science. For example, Jerry
Coyne asks why a designer would "give us a pathway for making vitamin C, but then destroy it by disabling one of
its enzymes" (see pseudogene) and why he or she would not "stock oceanic islands with reptiles, mammals,
amphibians, and freshwater fish, despite the suitability of such islands for these species". Coyne also points to the
fact that "the flora and fauna on those islands resemble that of the nearest mainland, even when the environments are
very different" as evidence that species were not placed there by a designer.[85] Previously, in Darwin's Black Box,
Behe had argued that we are simply incapable of understanding the designer's motives, so such questions cannot be
answered definitively. Odd designs could, for example, "have been placed there by the designer ... for artistic
reasons, to show off, for some as-yet undetectable practical purpose, or for some unguessable reason". Coyne
responds that in light of the evidence, "either life resulted not from intelligent design, but from evolution; or the
intelligent designer is a cosmic prankster who designed everything to make it look as though it had evolved".[85]
Asserting the need for a designer of complexity also raises the question "What designed the designer?"[86] Intelligent
design proponents say that the question is irrelevant to or outside the scope of intelligent design.[87] Richard Wein
counters that the unanswered questions an explanation creates "must be balanced against the improvements in our
understanding which the explanation provides. Invoking an unexplained being to explain the origin of other beings
(ourselves) is little more than question-begging. The new question raised by the explanation is as problematic as the
question which the explanation purports to answer".[68] Richard Dawkins sees the assertion that the designer does
not need to be explained, not as a contribution to knowledge, but as a thought-terminating cliché.[88] [89] In the
absence of observable, measurable evidence, the very question "What designed the designer?" leads to an infinite
regression from which intelligent design proponents can only escape by resorting to religious creationism or logical
contradiction.[90]

Movement
The intelligent design movement is a direct outgrowth of the
creationism of the 1980s.[10] The scientific and academic communities,
along with a U.S. federal court, view intelligent design as either a form
of creationism or as a direct descendant that is closely intertwined with
traditional creationism;[17] [18] [92] [93] [94] [95] and several authors
explicitly refer to it as "intelligent design creationism".[10] [96] [97] [98]
The Discovery Institute's Center for the Renewal
The movement is headquartered in the Center for Science and Culture
of Science and Culture used banners based on
"The Creation of Adam" from the Sistine Chapel. (CSC), established in 1996 as the creationist wing of the Discovery
Later it used a less religious image, then was Institute to promote a religious agenda[99] calling for broad social,
[91]
renamed the Center for Science and Culture. academic and political changes. The Discovery Institute's intelligent
Intelligent design 413

design campaigns have been staged primarily in the United States, although efforts have been made in other
countries to promote intelligent design. Leaders of the movement say intelligent design exposes the limitations of
scientific orthodoxy and of the secular philosophy of naturalism. Intelligent design proponents allege that science
should not be limited to naturalism and should not demand the adoption of a naturalistic philosophy that dismisses
out-of-hand any explanation which contains a supernatural cause. The overall goal of the movement is to "defeat
[the] materialist world view" represented by the theory of evolution in favor of "a science consonant with Christian
and theistic convictions".[99]
Phillip E. Johnson stated that the goal of intelligent design is to cast creationism as a scientific concept.[36] [100] All
leading intelligent design proponents are fellows or staff of the Discovery Institute and its Center for Science and
Culture.[101] Nearly all intelligent design concepts and the associated movement are the products of the Discovery
Institute, which guides the movement and follows its wedge strategy while conducting its Teach the Controversy
campaign and their other related programs.
Leading intelligent design proponents have made conflicting statements regarding intelligent design. In statements
directed at the general public, they say intelligent design is not religious; when addressing conservative Christian
supporters, they state that intelligent design has its foundation in the Bible.[100] Recognizing the need for support, the
institute affirms its Christian, evangelistic orientation: "Alongside a focus on influential opinion-makers, we also
seek to build up a popular base of support among our natural constituency, namely, Christians. We will do this
primarily through apologetics seminars. We intend these to encourage and equip believers with new scientific
evidences that support the faith, as well as to 'popularize' our ideas in the broader culture."[99]
Barbara Forrest, an expert who has written extensively on the movement, describes this as being due to the
Discovery Institute's obfuscating its agenda as a matter of policy. She has written that the movement's "activities
betray an aggressive, systematic agenda for promoting not only intelligent design creationism, but the religious
world-view that undergirds it".[102]

Religion and leading proponents

Although arguments for intelligent design are formulated in secular terms and intentionally avoid positing the
identity of the designer,[103] the majority of principal intelligent design advocates are publicly religious Christians
who have stated that in their view the designer proposed in intelligent design is the Christian conception of God.
Stuart Burgess, Phillip E. Johnson, William Dembski, and Stephen C. Meyer are evangelical Protestants, and
Michael Behe is a Roman Catholic, while Jonathan Wells is a member of the Unification Church. Phillip E. Johnson
has stated that cultivating ambiguity by employing secular language in arguments that are carefully crafted to avoid
overtones of theistic creationism is a necessary first step for ultimately reintroducing the Christian concept of God as
the designer. Johnson explicitly calls for intelligent design proponents to obfuscate their religious motivations so as
to avoid having intelligent design identified "as just another way of packaging the Christian evangelical
message".[104] Johnson emphasizes that "the first thing that has to be done is to get the Bible out of the discussion";
"after we have separated materialist prejudice from scientific fact [...] only then can 'biblical issues' be
discussed".[105]
The strategy of deliberately disguising the religious intent of intelligent design has been described by William
Dembski in The Design Inference.[106] In this work Dembski lists a god or an "alien life force" as two possible
options for the identity of the designer; however, in his book Intelligent Design: The Bridge Between Science and
Theology, Dembski states that "Christ is indispensable to any scientific theory, even if its practitioners don't have a
clue about him. The pragmatics of a scientific theory can, to be sure, be pursued without recourse to Christ. But the
conceptual soundness of the theory can in the end only be located in Christ."[107] Dembski also stated, "ID is part of
God's general revelation [...] Not only does intelligent design rid us of this ideology (materialism), which suffocates
the human spirit, but, in my personal experience, I've found that it opens the path for people to come to Christ".[108]
Both Johnson and Dembski cite the Bible's Gospel of John as the foundation of intelligent design.[35] [100]
Intelligent design 414

Barbara Forrest contends such statements reveal that leading proponents see intelligent design as essentially religious
in nature, not merely a scientific concept that has implications with which their personal religious beliefs happen to
coincide.[109] She writes that the leading proponents of intelligent design are closely allied with the
ultra-conservative Christian Reconstructionism movement. She lists connections of (current and former) Discovery
Institute Fellows Phillip Johnson, Charles Thaxton, Michael Behe, Richard Weikart, Jonathan Wells and Francis
Beckwith to leading Christian Reconstructionist organizations, and the extent of the funding provided the Institute by
Howard Ahmanson Jr., a leading figure in the Reconstructionist movement.[110]

Reaction from other creationist groups

Not all creationist organizations have embraced the intelligent design movement. Hugh Ross of Reasons to Believe,
a proponent of Old Earth creationism, believes that the efforts of intelligent design proponents to divorce the concept
from Biblical Christianity make its hypothesis too vague. In 2002 he wrote: "Winning the argument for design
without identifying the designer yields, at best, a sketchy origins model. Such a model makes little if any positive
impact on the community of scientists and other scholars… The time is right for a direct approach, a single leap into
the origins fray. Introducing a biblically based, scientifically verifiable creation model represents such a leap."[111]
Likewise, two of the most prominent Young Earth creationism organizations in the world have attempted to
distinguish their views from intelligent design. Henry M. Morris of the Institute for Creation Research (ICR) wrote,
in 1999, that ID, "even if well-meaning and effectively articulated, will not work! It has often been tried in the past
and has failed, and it will fail today. The reason it won't work is because it is not the Biblical method.” According to
Morris: “The evidence of intelligent design… must be either followed by or accompanied by a sound presentation of
true Biblical creationism if it is to be meaningful and lasting."[112] In 2002, Carl Wieland of Answers in Genesis
(AiG) criticized design advocates who, though well-intentioned, "left the Bible out of it" and thereby unwittingly
aided and abetted the modern rejection of the Bible. Wieland explained that "AiG's major 'strategy' is to boldly, but
humbly, call the church back to its Biblical foundations… [so] we neither count ourselves a part of this movement
nor campaign against it."[113]

Polls
Several surveys were conducted prior to the December 2005 decision in Kitzmiller v. Dover, which sought to
determine the level of support for intelligent design among certain groups. According to a 2005 Harris poll, 10% of
adults in the United States viewed human beings as "so complex that they required a powerful force or intelligent
being to help create them".[114] Although Zogby polls commissioned by the Discovery Institute show more support,
these polls suffer from considerable flaws, such as having a very low response rate (248 out of 16,000), being
conducted on behalf of an organization with an expressed interest in the outcome of the poll, and containing leading
questions.[115] [116] [117]
A May 2005 survey of nearly 1500 physicians in the United States conducted by the Louis Finkelstein Institute and
HCD Research showed that 63% of the physicians agreed more with evolution than with intelligent design.[118]
A series of Gallup polls in the United States from 1982 through 2008 on "Evolution, Creationism, Intelligent
Design" found support for "human beings have developed over millions of years from less advanced formed of life,
but God guided the process" of between 35% and 40%, support for "God created human beings in pretty much their
present form at one time within the last 10,000 years or so" varied from 43% to 47%, and support for "human beings
have developed over millions of years from less advanced formed of life, but God had no part in the process" varied
from 9% to 14%. The polls also noted answers to a series of more detailed questions.[119]
Intelligent design 415

Film
The film Expelled: No Intelligence Allowed sparked further controversy in 2008. This documentary, hosted by Ben
Stein, spends much time focusing on professors who have been asked to leave or have left numerous institutions
because, the film insinuates, of their beliefs in Intelligent Design. One of the film's first screenings resulted in Paul
"PZ" Myers, an interviewee in the film, being asked to leave the theater. There have also been allegations from some
interviewees that interviews were recorded many times in order to get the exact phrasing required by the producer.
The production company, Premise Media, also has helped finance some religious films such as The Passion of the
Christ. [120] [121]

Creating and teaching the controversy

The intelligent design movement states that there is a debate among scientists about whether life evolved. The
movement stresses the importance of recognizing the existence of this supposed debate, seeking to convince the
public, politicians, and cultural leaders that schools should "Teach the Controversy".[122] But in fact, there is no such
controversy in the scientific community; the scientific consensus is that life evolved.[123] [124] [125] Intelligent design
is widely viewed as a stalking horse for its proponents' campaign against what they say is the materialist foundation
of science, which they argue leaves no room for the possibility of God.[126] [127]
Advocates of intelligent design seek to keep God and the Bible out of the discussion, and present intelligent design
in the language of science as though it were a scientific hypothesis.[103] [105] However, among a significant
proportion of the general public in the United States the major concern is whether conventional evolutionary biology
is compatible with belief in God and in the Bible, and how this issue is taught in schools.[128] The public controversy
was given widespread media coverage in the United States, particularly during the Kitzmiller v. Dover trial in late
2005 and after President George W. Bush expressed support for the idea of teaching intelligent design alongside
evolution in August 2005. In response to Bush’s statement and the pending federal trial, Time magazine ran an
eight-page cover story on the Evolution Wars in which they examined the issue of teaching intelligent design in the
classroom.[129] [130] The cover of the magazine featured a parody of The Creation of Adam from the Sistine Chapel.
Rather than pointing at Adam, Michelangelo’s God points at the image of a chimpanzee contemplating the caption
which read "The push to teach "intelligent design" raises a question: Does God have a place in science class?".[131]
In the Kitzmiller v. Dover case, the court ruled that intelligent design was a religious and creationist position, finding
that God and intelligent design were both distinct from the material that should be covered in a science class.[9]
Empirical science uses the scientific method to create a posteriori knowledge based on observation and repeated
testing of hypotheses and theories. Intelligent design proponents seek to change this fundamental basis of
science[132] by eliminating "methodological naturalism" from science[133] and replacing it with what the leader of the
intelligent design movement, Phillip E. Johnson, calls "theistic realism".[134] Some have called this approach
"methodological supernaturalism", which means belief in a transcendent, nonnatural dimension of reality inhabited
by a transcendent, nonnatural deity.[135] Intelligent design proponents argue that naturalistic explanations fail to
explain certain phenomena and that supernatural explanations provide a very simple and intuitive explanation for the
origins of life and the universe.[136] Proponents say evidence exists in the forms of irreducible complexity and
specified complexity that cannot be explained by natural processes.[1] They also hold that religious neutrality
requires the teaching of both evolution and intelligent design in schools, saying that teaching only evolution unfairly
discriminates against those holding creationist beliefs. Teaching both, they argue, allows for the possibility of
religious belief, without causing the state to actually promote such beliefs. Many intelligent design followers believe
that "Scientism" is itself a religion that promotes secularism and materialism in an attempt to erase theism from
public life, and they view their work in the promotion of intelligent design as a way to return religion to a central role
in education and other public spheres. Some allege that this larger debate is often the subtext for arguments made
over intelligent design, though others note that intelligent design serves as an effective proxy for the religious beliefs
of prominent intelligent design proponents in their efforts to advance their religious point of view within society.[137]
Intelligent design 416

[138] [139]

Intelligent design has not presented a credible scientific case and is an attempt to teach religion in public schools,
substituting public support for scientific research.[140] If the argument to give "equal time for all theories" were
actually practiced, there would be no logical limit to the number of mutually incompatible supernatural "theories"
regarding the origins and diversity of life to be taught in the public school system, including intelligent design
parodies such as the Flying Spaghetti Monster "theory"; intelligent design does not provide a mechanism for
discriminating among them. Philosopher of biology Elliott Sober, for example, states that intelligent design is not
falsifiable because "[d]efenders of ID always have a way out".[141] [142] Intelligent design proponent Michael Behe
concedes "You can't prove intelligent design by experiment".[128]
Intelligent design proponents cannot legitimately infer that an intelligent designer is behind the part of the process
that is not understood scientifically, since they have not shown that anything supernatural has occurred. The
inference that an intelligent designer created life on Earth, which advocate William Dembski has said could
alternately be an "alien" life force,[106] has been compared to the a priori claim that aliens helped the ancient
Egyptians build the pyramids.[143] [144] In both cases, the effect of this outside intelligence is not repeatable,
observable or falsifiable, and it violates the principle of parsimony. From a strictly empirical standpoint, one may list
what is known about Egyptian construction techniques, but one must admit ignorance about exactly how the
Egyptians built the pyramids.
Supporters of intelligent design have also reached out to other faith groups with similar accounts of creation with the
hope that the broader coalition will have greater influence in supporting science education that does not contradict
their religious views.[136] Many religious bodies have responded by expressing support for evolution. The Roman
Catholic church has stated that religious faith is fully compatible with science, which is limited to dealing only with
the natural world[145] — a position described by the term theistic evolution.[146] As well as pointing out that
intelligent design is not science, they also reject it for various philosophical and theological reasons.[147] [148] The
arguments of intelligent design have been directly challenged by the over 10,000 clergy who signed the Clergy
Letter Project. Prominent scientists who strongly express religious faith, such as the astronomer George Coyne and
the biologist Ken Miller, have been at the forefront of opposition to intelligent design. While creationist
organizations have welcomed intelligent design's support against naturalism, they have also been critical of its
refusal to identify the designer,[149] [150] [151] and have pointed to previous failures of the same argument.[152]
Rabbi Natan Slifkin directly criticized the advocates of intelligent design as presenting a perspective of God that is
dangerous to religion.[153] Those who promote it as parallel to religion, he asserts, do not truly understand it. Slifkin
criticizes intelligent design's advocacy of teaching their perspective in biology classes, wondering why no one claims
that God's hand should be taught in other secular classes, such as history, physics or geology. Slifkin also asserts that
the intelligent design movement is inordinately concerned with portraying God as "in control" when it comes to
things that cannot be easily explained by science, but not in control in respect to things which can be explained by
scientific theory.[153] Kenneth Miller expressed a view similar to Slifkin's: "[T]he struggles of the Intelligent Design
movement are best understood as clamorous and disappointing double failures - rejected by science because they do
not fit the facts, and having failed religion because they think too little of God.[154]

Defining science
The scientific method is a body of techniques for investigating phenomena and acquiring new knowledge of the
natural world without assuming the existence or nonexistence of the supernatural, an approach sometimes called
methodological naturalism. Intelligent design proponents believe that this can be equated to materialist metaphysical
naturalism, and have often said that not only is their own position scientific, but it is even more scientific than
evolution, and that they want a redefinition of science as a revived natural theology or natural philosophy to allow
"non-naturalistic theories such as intelligent design".[155] This presents a demarcation problem, which in the
philosophy of science is about how and where to draw the lines around science.[156] For a theory to qualify as
Intelligent design 417

scientific,[157] [158] [159] it is expected to be:

• Consistent
• Parsimonious (sparing in its proposed entities or explanations, see Occam's Razor)
• Useful (describes and explains observed phenomena, and can be used predictively)
• Empirically testable and falsifiable (see Falsifiability)
• Based on multiple observations, often in the form of controlled, repeated experiments
• Correctable and dynamic (modified in the light of observations that do not support it)
• Progressive (refines previous theories)
• Provisional or tentative (is open to experimental checking, and does not assert certainty)
For any theory, hypothesis or conjecture to be considered scientific, it must meet most, and ideally all, of these
criteria. The fewer criteria are met, the less scientific it is; and if it meets only a few or none at all, then it cannot be
treated as scientific in any meaningful sense of the word. Typical objections to defining intelligent design as science
are that it lacks consistency,[160] violates the principle of parsimony,[161] is not scientifically useful,[162] is not
falsifiable,[163] is not empirically testable,[164] and is not correctable, dynamic, provisional or progressive.[165] [166]
[167]

Critics also say that the intelligent design doctrine does not meet the Daubert Standard,[168] the criteria for scientific
evidence mandated by the US Supreme Court. The Daubert Standard governs which evidence can be considered
scientific in United States federal courts and most state courts. Its four criteria are:
• The theoretical underpinnings of the methods must yield testable predictions by means of which the theory could
be falsified.
• The methods should preferably be published in a peer-reviewed journal.
• There should be a known rate of error that can be used in evaluating the results.
• The methods should be generally accepted within the relevant scientific community.
In Kitzmiller v. Dover Area School District, using these criteria and others mentioned above, Judge Jones ruled that
"... we have addressed the seminal question of whether ID is science. We have concluded that it is not, and moreover
that ID cannot uncouple itself from its creationist, and thus religious, antecedents".
Against this, the philosopher Thomas Nagel argues that intelligent design is very different from creation science, in
that it does not depend on distortion of evidence, or on the assumption that it is immune to empirical evidence. It
depends only on the idea that the hypothesis of a designer makes sense. Whatever the merits of the positions, he
argues that it is a scientific disagreement, not a disagreement between science and something else.[169]
The U.S. National Academy of Sciences has stated that "creationism, intelligent design, and other claims of
supernatural intervention in the origin of life or of species are not science because they are not testable by the
methods of science."[170] The U.S. National Science Teachers Association and the American Association for the
Advancement of Science have termed it pseudoscience.[171] [17] [18] Others in the scientific community have
concurred,[172] and some have called it junk science.[173] [174]

Peer review
The failure to follow the procedures of scientific discourse and the failure to submit work to the scientific
community that withstands scrutiny have weighed against intelligent design being accepted as valid science.[175] The
intelligent design movement has not published a properly peer-reviewed article in a scientific journal.[175]
Intelligent design, by appealing to a supernatural agent, directly conflicts with the principles of science, which limit
its inquiries to empirical, observable and ultimately testable data and which require explanations to be based on
empirical evidence. Dembski, Behe and other intelligent design proponents say bias by the scientific community is to
blame for the failure of their research to be published.[176] Intelligent design proponents believe that their writings
are rejected for not conforming to purely naturalistic, non-supernatural mechanisms rather than because their
Intelligent design 418

research is not up to "journal standards", and that the merit of their articles is overlooked. Some scientists describe
this claim as a conspiracy theory.[177] Michael Shermer has rebutted the claim, noting "Anyone who thinks that
scientists do not question Darwinism has never been to an evolutionary conference." He noted that scientists such as
Joan Roughgarden and Lynn Margulis have challenged certain Darwinist theories and offered explanations of their
own and despite this they "have not been persecuted, shunned, fired or even expelled. Why? Because they are doing
science, not religion."[178] The issue that supernatural explanations do not conform to the scientific method became a
sticking point for intelligent design proponents in the 1990s, and is addressed in the wedge strategy as an aspect of
science that must be challenged before intelligent design can be accepted by the broader scientific community.
Critics and advocates debate over whether intelligent design produces new research and has legitimately attempted to
publish this research. For instance, the Templeton Foundation, a former funder of the Discovery Institute and a major
supporter of projects seeking to reconcile science and religion, says that it asked intelligent design proponents to
submit proposals for actual research, but none were ever submitted. Charles L. Harper Jr., foundation vice-president,
said: "From the point of view of rigor and intellectual seriousness, the intelligent design people don't come out very
well in our world of scientific review".[179]
The only article published in a peer-reviewed scientific journal that made a case for intelligent design was quickly
withdrawn by the publisher for having circumvented the journal's peer-review standards.[180] Written by the
Discovery Institute's Center for Science & Culture Director Stephen C. Meyer, it appeared in the peer-reviewed
journal Proceedings of the Biological Society of Washington in August 2004.[181] The article was a literature review,
which means that it did not present any new research, but rather culled quotations and claims from other papers to
argue that the Cambrian explosion could not have happened by natural processes. The choice of venue for this article
was also considered problematic, because it was so outside the normal subject matter (see Sternberg peer review
controversy[182] ). Dembski has written that "perhaps the best reason [to be skeptical of his ideas] is that intelligent
design has yet to establish itself as a thriving scientific research program."[183] In a 2001 interview, Dembski said
that he stopped submitting to peer-reviewed journals because of their slow time-to-print and that he makes more
money from publishing books.[184]
In the Dover trial, the judge found that intelligent design features no scientific research or testing.[185] There,
intelligent design proponents cited just one paper, on simulation modeling of evolution by Behe and Snoke,[186]
which mentioned neither irreducible complexity nor intelligent design and which Behe admitted did not rule out
known evolutionary mechanisms.[187] Michael Lynch called the conclusions of the article "an artifact of unwarranted
biological assumptions, inappropriate mathematical modeling, and faulty logic".[188] In sworn testimony, however,
Behe said: "There are no peer reviewed articles by anyone advocating for intelligent design supported by pertinent
experiments or calculations which provide detailed rigorous accounts of how intelligent design of any biological
system occurred".[189] As summarized by the judge, Behe conceded that there are no peer-reviewed articles
supporting his claims of intelligent design or irreducible complexity. In his ruling, the judge wrote: "A final indicator
of how ID has failed to demonstrate scientific warrant is the complete absence of peer-reviewed publications
supporting the theory".[175]
The Discovery Institute insists that a number of intelligent design articles have been published in peer-reviewed
journals,[190] including in its list the two articles mentioned above. Critics, largely members of the scientific
community, reject this claim, stating that no established scientific journal has yet published an intelligent design
article. Rather, intelligent design proponents have set up their own journals with peer review that lacks impartiality
and rigor,[191] consisting entirely of intelligent design supporters.[192]
Intelligent design 419

Intelligence as an observable quality

The phrase intelligent design makes use of an assumption of the quality of an observable intelligence, a concept that
has no scientific consensus definition. William Dembski, for example, has written that "Intelligence leaves behind a
characteristic signature". The characteristics of intelligence are assumed by intelligent design proponents to be
observable without specifying what the criteria for the measurement of intelligence should be. Dembski, instead,
asserts that "in special sciences ranging from forensics to archaeology to SETI (the Search for Extraterrestrial
Intelligence), appeal to a designing intelligence is indispensable".[193] How this appeal is made and what this implies
as to the definition of intelligence are topics left largely unaddressed. Seth Shostak, a researcher with the SETI
Institute, disputed Dembski's comparison of SETI and intelligent design, saying that intelligent design advocates
base their inference of design on complexity—the argument being that some biological systems are too complex to
have been made by natural processes—while SETI researchers are looking primarily for artificiality.[194]
Critics say that the design detection methods proposed by intelligent design proponents are radically different from
conventional design detection, undermining the key elements that make it possible as legitimate science. Intelligent
design proponents, they say, are proposing both searching for a designer without knowing anything about that
designer's abilities, parameters, or intentions (which scientists do know when searching for the results of human
intelligence), as well as denying the very distinction between natural/artificial design that allows scientists to
compare complex designed artifacts against the background of the sorts of complexity found in nature.[195]
As a means of criticism, certain skeptics have pointed to a challenge of intelligent design derived from the study of
artificial intelligence. The criticism is a counter to intelligent design claims about what makes a design intelligent,
specifically that "no preprogrammed device can be truly intelligent, that intelligence is irreducible to natural
processes".[196] This claim is similar in type to an assumption of Cartesian dualism that posits a strict separation
between "mind" and the material Universe. However, in studies of artificial intelligence, while there is an implicit
assumption that supposed "intelligence" or creativity of a computer program is determined by the capabilities given
to it by the computer programmer, artificial intelligence need not be bound to an inflexible system of rules. Rather, if
a computer program can access randomness as a function, this effectively allows for a flexible, creative, and adaptive
intelligence. Evolutionary algorithms, a subfield of machine learning (itself a subfield of artificial intelligence), have
been used to mathematically demonstrate that randomness and selection can be used to "evolve" complex, highly
adapted structures that are not explicitly designed by a programmer. Evolutionary algorithms use the Darwinian
metaphor of random mutation, selection and the survival of the fittest to solve diverse mathematical and scientific
problems that are usually not solvable using conventional methods. Intelligence derived from randomness is
essentially indistinguishable from the "innate" intelligence associated with biological organisms, and poses a
challenge to the intelligent design conception that intelligence itself necessarily requires a designer. Cognitive
science continues to investigate the nature of intelligence along these lines of inquiry. The intelligent design
community, for the most part, relies on the assumption that intelligence is readily apparent as a fundamental and
basic property of complex systems.[197]

Arguments from ignorance

Eugenie Scott, along with Glenn Branch and other critics, has argued that many points raised by intelligent design
proponents are arguments from ignorance.[198] In the argument from ignorance, a lack of evidence for one view is
erroneously argued to constitute proof of the correctness of another view. Scott and Branch say that intelligent
design is an argument from ignorance because it relies on a lack of knowledge for its conclusion: lacking a natural
explanation for certain specific aspects of evolution, we assume intelligent cause. They contend most scientists
would reply that the unexplained is not unexplainable, and that "we don't know yet" is a more appropriate response
than invoking a cause outside science.[198] Particularly, Michael Behe's demands for ever more detailed explanations
of the historical evolution of molecular systems seem to assume a false dichotomy, where either evolution or design
is the proper explanation, and any perceived failure of evolution becomes a victory for design. Scott and Branch also
Intelligent design 420

contend that the supposedly novel contributions proposed by intelligent design proponents have not served as the
basis for any productive scientific research.
Intelligent design has also been characterized as a "god of the gaps" argument,[199] which has the following form:
• There is a gap in scientific knowledge.
• The gap is filled with acts of God (or intelligent designer) and therefore proves the existence of God (or
intelligent designer).[199]
A god-of-the-gaps argument is the theological version of an argument from ignorance. A key feature of this type of
argument is that it merely answers outstanding questions with explanations (often supernatural) that are unverifiable
and ultimately themselves subject to unanswerable questions.[200]

Kitzmiller trial
Kitzmiller v. Dover Area School District was the first direct challenge brought in the United States federal courts
against a public school district that required the presentation of intelligent design as an alternative to evolution. The
plaintiffs successfully argued that intelligent design is a form of creationism, and that the school board policy thus
violated the Establishment Clause of the First Amendment to the United States Constitution.[201]
Eleven parents of students in Dover, Pennsylvania, sued the Dover Area School District over a statement that the
school board required be read aloud in ninth-grade science classes when evolution was taught. The plaintiffs were
represented by the American Civil Liberties Union (ACLU), Americans United for Separation of Church and State
(AU) and Pepper Hamilton LLP. The National Center for Science Education (NCSE) acted as consultants for the
plaintiffs. The defendants were represented by the Thomas More Law Center.[202] The suit was tried in a bench trial
from September 26, 2005 to November 4, 2005 before Judge John E. Jones III. Ken Miller, Kevin Padian, Brian
Alters, Robert Pennock, Barbara Forrest and John Haught served as expert witnesses for the prosecution. Michael
Behe, Steve Fuller and Scott Minnich served as expert witnesses for the defense.
On December 20, 2005 Judge Jones issued his 139-page findings of fact and decision, ruling that the Dover mandate
was unconstitutional, and barring intelligent design from being taught in Pennsylvania's Middle District public
school science classrooms. The eight Dover school board members who voted for the intelligent design requirement
were all defeated in a November 8, 2005 election by challengers who opposed the teaching of intelligent design in a
science class, and the current school board president stated that the board does not intend to appeal the ruling.[203]
In his finding of facts, Judge Jones made the following condemnation of the Teach the Controversy strategy:
"Moreover, ID’s backers have sought to avoid the scientific scrutiny which we have now determined that
it cannot withstand by advocating that the controversy, but not ID itself, should be taught in science
class. This tactic is at best disingenuous, and at worst a canard."

Reaction
Judge Jones himself anticipated that his ruling would be criticized, saying in his decision that:
"Those who disagree with our holding will likely mark it as the product of an activist judge. If so, they
will have erred as this is manifestly not an activist Court. Rather, this case came to us as the result of the
activism of an ill-informed faction on a school board, aided by a national public interest law firm eager
to find a constitutional test case on ID, who in combination drove the Board to adopt an imprudent and
ultimately unconstitutional policy. The breathtaking inanity of the Board's decision is evident when
considered against the factual backdrop which has now been fully revealed through this trial. The
students, parents, and teachers of the Dover Area School District deserved better than to be dragged into
this legal maelstrom, with its resulting utter waste of monetary and personal resources."[204]
As Jones had predicted, John G. West, Associate Director of the Center for Science and Culture at Discovery
Institute, said:
Intelligent design 421

"The Dover decision is an attempt by an activist federal judge to stop the spread of a scientific idea and
even to prevent criticism of Darwinian evolution through government-imposed censorship rather than
open debate, and it won't work. He has conflated Discovery Institute's position with that of the Dover
school board, and he totally misrepresents intelligent design and the motivations of the scientists who
research it."[205]
Newspapers have noted with interest that the judge is "a Republican and a churchgoer".[206] [207] [208] [209]
Subsequently, the decision has been examined in a search for flaws and conclusions, partly by intelligent design
supporters aiming to avoid future defeats in court. In the Spring of 2007 the University of Montana Law review
published three articles.[210] In the first, David K. DeWolf, John G. West and Casey Luskin, all of the Discovery
Institute, argued that intelligent design is a valid scientific theory, the Jones court should not have addressed the
question of whether it was a scientific theory, and that the Kitzmiller decision will have no effect at all on the
development and adoption of intelligent design as an alternative to standard evolutionary theory.[130] In the second
Peter Irons responded, arguing that the decision was extremely well reasoned and spells the death knell for the
intelligent design efforts to introduce creationism in public schools,[211] while in the third, DeWolf et al. answer the
points made by Irons.[212] However, fear of a similar lawsuit has resulted in other school boards abandoning
intelligent design "teach the controversy" proposals.[10]
In April 2010, the American Academy of Religion issued Guidelines for Teaching About Religion in K‐12 Public
Schools in the United States which included guidance that creation science or intelligent design should not be taught
in science classes, as "Creation science and intelligent design represent worldviews that fall outside of the realm of
science that is defined as (and limited to) a method of inquiry based on gathering observable and measurable
evidence subject to specific principles of reasoning." However, they, as well as other "worldviews that focus on
speculation regarding the origins of life represent another important and relevant form of human inquiry that is
appropriately studied in literature or social sciences courses. Such study, however, must include a diversity of
worldviews representing a variety of religious and philosophical perspectives and must avoid privileging one view as
more legitimate than others."[213]

Status outside the United States

Europe
In June 2007 the Council of Europe's "Committee on Culture, Science and Education" issued a report, The dangers
of creationism in education, which states "Creationism in any of its forms, such as 'intelligent design', is not based on
facts, does not use any scientific reasoning and its contents are pathetically inadequate for science classes."[214] In
describing the dangers posed to education by teaching creationism, it described intelligent design as "anti-science"
and involving "blatant scientific fraud" and "intellectual deception" that "blurs the nature, objectives and limits of
science" and links it and other forms of creationism to denialism. On October 4, 2007, the Council of Europe's
Parliamentary Assembly approved a resolution stating that schools should "resist presentation of creationist ideas in
any discipline other than religion", including "intelligent design" which it described as "the latest, more refined
version of creationism", "presented in a more subtle way". The resolution emphasises that the aim of the report is not
to question or to fight a belief, but to "warn against certain tendencies to pass off a belief as science".[215]
In the United Kingdom, public education includes Religious Education as a compulsory subject, and many "faith
schools" that teach the ethos of particular denominations. When it was revealed that a group called Truth in Science
had distributed DVDs produced by the Discovery Institute affiliate Illustra Media[216] featuring Discovery Institute
fellows making the case for design in nature,[217] and claimed they were being used by 59 schools,[218] the
Department for Education and Skills (DfES) stated that "Neither creationism nor intelligent design are taught as a
subject in schools, and are not specified in the science curriculum" (part of the National Curriculum which does not
apply to independent schools or to Education in Scotland).[219] [220] The DfES subsequently stated that "Intelligent
Intelligent design 422

design is not a recognised scientific theory; therefore, it is not included in the science curriculum", but left the way
open for it to be explored in religious education in relation to different beliefs, as part of a syllabus set by a local
Standing Advisory Council on Religious Education.[221] In 2006 the Qualifications and Curriculum Authority
produced a Religious Education model unit in which pupils can learn about religious and nonreligious views about
creationism, intelligent design and evolution by natural selection.[222] [223]
On June 25, 2007, the UK Government responded to an e-Petition by saying that creationism and intelligent design
should not be taught as science, though teachers would be expected to answer pupils' questions within the standard
framework of established scientific theories.[224] Detailed government "Creationism teaching guidance" for schools
in England was published on September 18, 2007. It states that "Intelligent design lies wholly outside of science",
has no underpinning scientific principles, or explanations, and is not accepted by the science community as a whole.
Though it should not be taught as science, "questions about creationism and intelligent design which arise in science
lessons, for example, as a result of media coverage, could provide the opportunity to explain or explore why they are
not considered to be scientific theories and, in the right context, why evolution is considered to be a scientific
theory". However, "Teachers of subjects such as RE, history or citizenship may deal with creationism and intelligent
design in their lessons".[13]
The British Centre for Science Education lobbying group has the goal of "countering creationism within the UK" and
has been involved in government lobbying in the UK in this regard.[225] However, in Northern Ireland the
Democratic Unionist Party claims that the revised curriculum provides an opportunity for alternative theories to be
taught, and has sought assurances that pupils will not lose marks if they give creationist or intelligent design answers
to science questions.[226] In Lisburn the DUP has arranged that the City Council will write to post primary schools
asking what their plans are to develop teaching material in relation to "creation, intelligent design and other theories
of origin".[227]
Plans by Dutch Education Minister Maria van der Hoeven to "stimulate an academic debate" on the subject in 2005
caused a severe public backlash.[228] After the 2007 elections she was succeeded by Ronald Plasterk, described as a
"molecular geneticist, staunch atheist and opponent of intelligent design".[229] As a reaction on this situation in the
Netherlands, in Belgium the President of the Flemish Catholic Educational Board (VSKO) Mieke Van Hecke
declared that: "Catholic scientists already accepted the theory of evolution for a long time and that intelligent design
and creationism doesn't belong in Flemish Catholic schools. It's not the tasks of the politics to introduce new ideas,
that's task and goal of science."[230]

Relation to Islam
Creationism has strong political support in many Islamic countries, and antievolutionary views are mainstream
among academic theologians and scientists.[231] In general, Muslim creationists have partnered with the Institute for
Creation Research for ideas and materials which they adapted to their own theological positions. Similarly, some use
was made of intelligent design antievolution resources. Muzaffar Iqbal, a notable Muslim in Canada, signed the
Scientific Dissent list of the Discovery Institute.[232] Ideas similar to intelligent design have been considered
respected intellectual options among Muslims, and in Turkey many intelligent design books have been translated. In
Istanbul in 2007, public meetings promoting intelligent design were sponsored by the local government,[231] and
David Berlinski of the Discovery Institute was the keynote speaker at a meeting in May 2007.[233]
Intelligent design 423

Australia
The status of intelligent design in Australia is somewhat similar to that in the UK (see: Education in Australia).
When the former Australian Federal Education Minister, Brendan Nelson, raised the notion of intelligent design
being taught in science classes, the public outcry caused the minister to quickly concede that the correct forum for
intelligent design, if it were to be taught, is in religious or philosophy classes.[234]

See also
• Abiogenesis • Intelligent falling
• Argument from poor design • List of works on intelligent design
• Cosmological argument • Neo-Creationism
• Creation science • Old Earth creationism
• Flock of Dodos • Santorum Amendment
• Flying Spaghetti Monster • Watchmaker analogy

Notes
[1] Discovery Institute. Top Questions-1.What is the theory of intelligent design? (http:/ / www. discovery. org/ csc/ topQuestions.
php#questionsAboutIntelligentDesign) [cited 2007-05-13].
[2] Intelligent Design and Evolution Awareness Center. Primer: Intelligent Design Theory in a Nutshell (http:/ / www. ideacenter. org/ stuff/
contentmgr/ files/ 393410a2d36e9b96329c2faff7e2a4df/ miscdocs/ intelligentdesigntheoryinanutshell. pdf) [PDF]; 2004 [cited 2007-05-13].
• Intelligent Design network. Intelligent Design (http:/ / www. intelligentdesignnetwork. org/ ); 2007 [cited 2007-05-13].
[3] The Creationists, Expanded Edition. Harvard University Press; 2006. ISBN 0674023390. p. 373, 379–380.
[4] "Q. Has the Discovery Institute been a leader in the intelligent design movement? A. Yes, the Discovery Institute's Center for Science and
Culture. Q. And are almost all of the individuals who are involved with the intelligent design movement associated with the Discovery
Institute? A. All of the leaders are, yes." Barbara Forrest, 2005, testifying in the Kitzmiller v. Dover Area School District trial. TalkOrigins
Archive. Kitzmiller v. Dover Area School District Trial transcript: Day 6 (October 5), PM Session, Part 1. (http:/ / www. talkorigins. org/ faqs/
dover/ day6pm. html); 2005 [cited 2007-07-19].
• "The Discovery Institute is the ideological and strategic backbone behind the eruption of skirmishes over science in school districts and
state capitals across the country". In: Wilgoren, J. Politicized Scholars Put Evolution on the Defensive (http:/ / www. msu. edu/ course/ te/
407/ FS05Sec3/ te408/ files/ Politicized Scholars Put Evolution on the Defensive - New York Times. pdf) [PDF].. August 21, 2005 [cited
2007-07-19]. New York Times.
• American Civil Liberties Union. Who is behind the ID movement? (http:/ / www. aclu. org/ religion/ schools/ 16371res20050916. html);
September 16, 2005 [cited 2007-07-20].
• Kahn, JP. The Evolution of George Gilder. The Author And Tech-Sector Guru Has A New Cause To Create Controversy With: Intelligent
Design (http:/ / www. discovery. org/ scripts/ viewDB/ index. php?command=view& program=DI Main Page - News& id=2745). July 27,
2005 [cited 2007-07-19]. The Boston Globe.
• "Who's Who of Intelligent Design Proponents" (http:/ / www. discovery. org/ scripts/ viewDB/ filesDB-download.
php?command=download& id=602) (PDF). Science & Religion Guide. Science & Theology News. November 2005. . Retrieved
2007-07-20.
• "The engine behind the ID movement is the Discovery Institute". Attie, Alan D.; Elliot Sober, Ronald L. Numbers, Richard M. Amasino,
Beth Cox4, Terese Berceau, Thomas Powell and Michael M. Cox (2006). "Defending science education against intelligent design: a call to
action" (http:/ / www. jci. org/ articles/ view/ 28449). Journal of Clinical Investigation 116:1134–1138. A publication of the American
Society for Clinical Investigation.. doi:10.1172/JCI28449. . Retrieved 2007-07-20.
[5] "Science and Policy: Intelligent Design and Peer Review" (http:/ / www. aaas. org/ spp/ dser/ 03_Areas/ evolution/ issues/ peerreview. shtml).
American Association for the Advancement of Science. 2007. . Retrieved 2007-07-19.
[6] "the writings of leading ID proponents reveal that the designer postulated by their argument is the God of Christianity". Kitzmiller v. Dover
Area School District, 04 cv 2688 (December 20, 2005)., Ruling p. 26. A selection of writings and quotes of intelligent design supporters
demonstrating this identification of the Christian God with the intelligent designer are found in the pdf Horse's Mouth (http:/ / home. kc. rr.
com/ bnpndxtr/ download/ HorsesMouth-BP007. pdf) Archived (http:/ / web. archive. org/ web/ 20080627021627/ http:/ / home. kc. rr. com/
bnpndxtr/ download/ HorsesMouth-BP007. pdf) June 27, 2008 at the Wayback Machine. (PDF) by Brian Poindexter, dated 2003.
[7] William A. Dembski, when asked in an interview whether his research concluded that God is the Intelligent Designer, stated "I believe God
created the world for a purpose. The Designer of intelligent design is, ultimately, the Christian God". Devon Williams (December 14, 2007).
"CitizenLink: Friday Five: William A. Dembski" (http:/ / www. citizenlink. org/ content/ A000006139. cfm). Focus on the Family. . Retrieved
2007-12-15.
Intelligent design 424

[8] Kitzmiller v. Dover Area School District, 04 cv 2688 (December 20, 2005)., Context pg. 32 ff, citing Edwards v. Aguillard, 482 U.S. 578
(http:/ / caselaw. lp. findlaw. com/ scripts/ getcase. pl?navby=CASE& court=US& vol=482& page=578) .
[9] "ID is not a new scientific argument, but is rather an old religious argument for the existence of God. He traced this argument back to at least
Thomas Aquinas in the 13th century, who framed the argument as a syllogism: Wherever complex design exists, there must have been a
designer; nature is complex; therefore nature must have had an intelligent designer." "This argument for the existence of God was advanced
early in the 19th century by Reverend Paley" (the teleological argument) "The only apparent difference between the argument made by Paley
and the argument for ID, as expressed by defense expert witnesses Behe and Minnich, is that ID's 'official position' does not acknowledge that
the designer is God." Kitzmiller v. Dover Area School District, 04 cv 2688 (December 20, 2005)., Ruling, p. 24.
[10] Washington, D.C.: Center for Inquiry, Office of Public Policy. Understanding the Intelligent Design Creationist Movement: Its True Nature
and Goals. (http:/ / www. centerforinquiry. net/ uploads/ attachments/ intelligent-design. pdf) [PDF]; 2007 May [cited 2007-08-06].
[11] Stephen C. Meyer and Paul A. Nelson (May 1, 1996). "CSC – Getting Rid of the Unfair Rules (http:/ / www. discovery. org/ scripts/
viewDB/ index. php?command=view& id=1685), A book review, Origins & Design"]. . Retrieved 2007-05-20.
• Phillip E. Johnson (August 31, 1996). "Starting a Conversation about Evolution" (http:/ / www. arn. org/ docs/ johnson/ ratzsch. htm).
Phillip Johnson Files. Access Research Network. . Retrieved 2007-05-20.
• Stephen C. Meyer (December 1, 2002). "The Scientific Status of Intelligent Design: The Methodological Equivalence of Naturalistic and
Non-Naturalistic Origins Theories" (http:/ / www. discovery. org/ scripts/ viewDB/ index. php?command=view& id=1780). Ignatius Press.
.
• Kitzmiller v. Dover Area School District, 04 cv 2688 (December 20, 2005)., Whether ID Is Science
• Kitzmiller v. Dover Area School District, 04 cv 2688 (December 20, 2005)., Lead defense expert Professor Behe admitted that his
broadened definition of science, which encompasses ID, would also include astrology.
• See also "Evolution of Kansas science standards continues as Darwin's theories regain prominence" (http:/ / www. iht. com/ articles/ ap/
2007/ 02/ 13/ america/ NA-GEN-US-Kansas-Evolution-History. php). International Herald Tribune. February 13, 2007. . Retrieved
2007-05-20.
[12] See: 1) List of scientific societies explicitly rejecting intelligent design 2) Kitzmiller v. Dover page 83. 3) The Discovery Institute's A
Scientific Dissent From Darwinism petition begun in 2001 has been signed by "over 700 scientists" as of August 20, 2006. A four day A
Scientific Support for Darwinism petition gained 7733 signatories from scientists opposing ID. The AAAS, the largest association of scientists
in the U.S., has 120,000 members, and firmly rejects ID (http:/ / www. aaas. org/ news/ releases/ 2002/ 1106id2. shtml). More than 70,000
Australian scientists and educators condemn teaching of intelligent design in school science classes (http:/ / web. archive. org/ web/
20060115091707/ http:/ / www. science. unsw. edu. au/ news/ 2005/ intelligent. html) List of statements from scientific professional
organizations (http:/ / ncse. com/ media/ voices/ science) on the status intelligent design and other forms of creationism. According to The New
York Times "There is no credible scientific challenge to the theory of evolution as an explanation for the complexity and diversity of life on
earth". Dean, Cordelia (September 27, 2007). "Scientists Feel Miscast in Film on Life's Origin" (http:/ / www. nytimes. com/ 2007/ 09/ 27/
science/ 27expelled. html?_r=2& oref=slogin& oref=slogin). New York Times. . Retrieved 2007-09-28.
[13] "Teachernet, Document bank" (http:/ / www. teachernet. gov. uk/ docbank/ index. cfm?id=11890). Creationism teaching guidance. UK
Department for Children, Schools and Families. September 18, 2007. . Retrieved 2007-10-01. "The intelligent design movement claims there
are aspects of the natural world that are so intricate and fit for purpose that they cannot have evolved but must have been created by an
'intelligent designer'. Furthermore they assert that this claim is scientifically testable and should therefore be taught in science lessons.
Intelligent design lies wholly outside of science. Sometimes examples are quoted that are said to require an 'intelligent designer'. However,
many of these have subsequently been shown to have a scientific explanation, for example, the immune system and blood clotting
mechanisms.
Attempts to establish an idea of the 'specified complexity' needed for intelligent design are surrounded by complex mathematics. Despite this,
the idea seems to be essentially a modern version of the old idea of the "God-of-the-gaps". Lack of a satisfactory scientific explanation of
some phenomena (a 'gap' in scientific knowledge) is claimed to be evidence of an intelligent designer."
[14] Nature Methods Editorial. An intelligently designed response. Nat. Methods. 2007;4(12):983. doi:10.1038/nmeth1207-983 (http:/ / dx. doi.
org/ 10. 1038/ nmeth1207-983).
[15] Mark Greener. Taking on creationism. Which arguments and evidence counter pseudoscience? (http:/ / www. ncbi. nlm. nih. gov/ pmc/
articles/ PMC2267227/ ). EMBO Reports. 2007;8(12):1107–1109. doi:10.1038/sj.embor.7401131 (http:/ / dx. doi. org/ 10. 1038/ sj. embor.
7401131). PMID 18059309.
[16] National Science Teachers Association, a professional association of 55,000 science teachers and administrators National Science Teachers
Association (August 3, 2005). "National Science Teachers Association Disappointed About Intelligent Design Comments Made by President
Bush" (http:/ / www. nsta. org/ about/ pressroom. aspx?id=50794). Press release. . "We stand with the nation's leading scientific organizations
and scientists, including Dr. John Marburger, the president's top science advisor, in stating that intelligent design is not science. ...It is simply
not fair to present pseudoscience to students in the science classroom."
[17] David Mu. Trojan Horse or Legitimate Science: Deconstructing the Debate over Intelligent Design (http:/ / www. hcs. harvard. edu/ ~hsr/
fall2005/ mu. pdf) [PDF]. Harvard Science Review. Fall 2005;19(1). "For most members of the mainstream scientific community, ID is not a
scientific theory, but a creationist pseudoscience"."
[18] American Association for the Advancement of Science. Professional Ethics Report (http:/ / www. aaas. org/ spp/ sfrl/ per/ per26. pdf)
[PDF]; 2001. "Creationists are repackaging their message as the pseudoscience of intelligent design theory."
[19] Kitzmiller v. Dover Area School District, 04 cv 2688 (December 20, 2005)., pp. 31 – 33.
Intelligent design 425

[20] Discovery Institute. Media Backgrounder: Intelligent Design Article Sparks Controversy (http:/ / www. discovery. org/ scripts/ viewDB/
index. php?command=view& id=2190); September 7, 2004.
• James M. Kushiner. Berkeley's Radical (http:/ / touchstonemag. com/ archives/ article. php?id=15-05-037-i); 2002 June.
• Jodi Wilgoren. Politicized Scholars Put Evolution on the Defensive (http:/ / www. msu. edu/ course/ te/ 407/ FS05Sec3/ te408/ files/
Politicized Scholars Put Evolution on the Defensive - New York Times. pdf) [PDF].. August 21, 2005.
• Discovery's Creation (http:/ / seattleweekly. com/ 2006-02-01/ news/ discovery-s-creation. php). February 1, 2006 [cited 2007-07-27].
Seattle Weekly.
[21] Kitzmiller v. Dover Area School District, 04 cv 2688 (December 20, 2005)., Conclusion of Ruling.
[22] Stanford Encyclopedia of Philosophy. Plato's Timaeus (http:/ / plato. stanford. edu/ entries/ plato-timaeus/ ); October 25, 2005 [cited
2007-07-22].
[23] Aristotle, Metaphysics Bk. 12
[24] See also, e.g.
*Richard Hooker (1996) "Aristotle" (http:/ / wsu. edu/ ~dee/ GREECE/ ARIST. HTM). "Aristotle's analysis of phenomenon and change, then,
is fundamentally teleological."
*Monte Ransome Johnson (2005) Aristotle on teleology, Clarendon Press.
[25] Linda Trinkaus Zagzebski (2006). The Philosophy of Religion: An Historical Introduction, 31; Cicero, De Natura Deorum, Book I, 36–37,
Latin Library (http:/ / www. thelatinlibrary. com/ cicero/ nd. shtml).
[26] Thomas Aquinas, Summa Theologiae " Thomas Aquinas' 'Five Ways' (http:/ / web. archive. org/ web/ 20070926220422/ http:/ / www.
faithnet. org. uk/ AS+ Subjects/ Philosophyofreligion/ fiveways. htm) ( archive link (http:/ / web. archive. org/ web/ 20070808152431/ http:/ /
www. faithnet. org. uk/ AS+ Subjects/ Philosophyofreligion/ fiveways. htm))" in faithnet.org.uk.
[27] William Paley, Natural Theology: or, Evidences of the Existence and Attributes of the Deity (http:/ / darwin-online. org. uk/ content/
frameset?itemID=A142& viewtype=text& pageseq=1), 1809, London, Twelfth Edition.
[28] Darwin Correspondence Project. Letter 2998 — Darwin, C. R. to Gray, Asa, 26 Nov (1860) (http:/ / www. darwinproject. ac. uk/
entry-2998) [cited 2010-08-11].
[29] Gerard Radnitzky. Evolutionary epistemology, rationality, and the sociology of knowledge. Open Court Publishing; 1993. ISBN
0812690397. p. 140.
[30] See, e.g., the publisher's editorial description of the 2006 paperback printing of William Paley (1803) Natural Theology" : "William Paley's
classic brings depth to the history of intelligent design arguments. The contrivance of the eye, the ear, and numerous other anatomical
features throughout the natural world are presented as arguments for God's presence and concern. While there are distinctive differences
between Paley's argument and those used today by intelligent design theorists and creationists, it remains a fascinating glimpse of the
nineteenth-century's debate over the roles of religion and science".
• David C. Steinmetz (2005) "The Debate on Intelligent Design" in The Christian Century, (December 27, 2005, pp. 27–31.)
• Leading intelligent design proponent William Dembski (2001) argues the opposing view in Is Intelligent Design a form of natural
theology? (http:/ / www. designinference. com/ documents/ 2001. 03. ID_as_nat_theol. htm)
[31] Forrest, Barbara. Know Your Creationists: Know Your Allies (http:/ / www. dailykos. com/ story/ 2006/ 3/ 11/ 8448/ 52824)
[32] Stephen C. Meyer. Access Research Network. We Are Not Alone (http:/ / www. arn. org/ docs/ meyer/ sm_notalone. htm); 1986 March
[cited 2007-10-10].
[33] Charles B. Thaxton, Ph.D.. Christian Leadership Ministries. DNA, Design and the Origin of Life (http:/ / www. origins. org/ articles/
thaxton_dnadesign. html); November 13–16, 1986 [cited 2007-10-10].
[34] Charles B. Thaxton. In Pursuit of Intelligent Causes: Some Historical Background (http:/ / www. leaderu. com/ offices/ thaxton/ docs/
inpursuit. html); June 23–26, 1988, revised July 1988 and May 1991 [cited 2007-10-06].
[35] Dembski: "Intelligent design is just the Logos theology of John's Gospel restated in the idiom of information theory," Touchstone Magazine.
Volume 12, Issue4: July/August, 1999 (http:/ / touchstonemag. com/ archives/ issue. php?id=49)
[36] Phillip Johnson: "Our strategy has been to change the subject a bit so that we can get the issue of Intelligent Design, which really means the
reality of God, before the academic world and into the schools." Johnson 2004. Christianity.ca. Let's Be Intelligent About Darwin (http:/ /
www. christianity. ca/ news/ social-issues/ 2004/ 03. 001. html) Archived (http:/ / web. archive. org/ web/ 20070608233455/ http:/ / www.
christianity. ca/ news/ social-issues/ 2004/ 03. 001. html) June 8, 2007 at the Wayback Machine.. "This isn't really, and never has been a
debate about science. It's about religion and philosophy." Johnson 1996. World Magazine. Witnesses For The Prosecution (http:/ / www.
leaderu. com/ pjohnson/ world2. html). "So the question is: "How to win?" That's when I began to develop what you now see full-fledged in
the "wedge" strategy: "Stick with the most important thing"—the mechanism and the building up of information. Get the Bible and the Book of
Genesis out of the debate because you do not want to raise the so-called Bible-science dichotomy. Phrase the argument in such a way that you
can get it heard in the secular academy and in a way that tends to unify the religious dissenters. That means concentrating on, "Do you need a
Creator to do the creating, or can nature do it on its own?" and refusing to get sidetracked onto other issues, which people are always trying
to do." Johnson 2000. Touchstone magazine. Berkeley's Radical An Interview with Phillip E. Johnson (http:/ / web. archive. org/ web/
20070609033219/ http:/ / www. touchstonemag. com/ docs/ issues/ 15. 5docs/ 15-5pg40. html) at the Wayback Machine (archived June 9,
2007).
[37] Stephen C. Meyer: "I think the designer is God ..." ( Darwin, the marketing of Intelligent Design (http:/ / www. bringyou. to/ apologetics/
p90. htm) . Nightline ABC News, with Ted Koppel, August 10, 2005); Nancy Pearcey: "By contrast, design theory demonstrates that
Christians can sit in the supernaturalist’s “chair” even in their professional lives, seeing the cosmos through the lens of a comprehensive
Intelligent design 426

biblical worldview. Intelligent Design steps boldly into the scientific arena to build a case based on empirical data. It takes Christianity out of
the ineffectual realm of value and stakes out a cognitive claim in the realm of objective truth. It restores Christianity to its status as genuine
knowledge, equipping us to defend it in the public arena". ( Total Truth (http:/ / web. archive. org/ web/ 20061028204903/ http:/ / rightreason.
ektopos. com/ archives/ 2005/ 09/ why_sciencetype. html), Crossway Books, June 29, 2004, ISBN 1581344589, pp. 204-205)
[38] Leon Lynn. Rethinking Schools Online (http:/ / www. rethinkingschools. org/ archive/ 12_02/ panda. shtml); Winter 1997/98 [cited
2009-02-08].
[39] Nick Matzke. The Panda's Thumb. The true origin of "intelligent design" (http:/ / pandasthumb. org/ archives/ 2007/ 08/ the-true-origin.
html); August 14, 2007 [cited 2010-01-21].
Journals: Scientific American (1846 - 1869) (http:/ / digital. library. cornell. edu/ cgi/ t/ text/ pageviewer-idx?c=scia;cc=scia;rgn=full
text;idno=scia0002-48;didno=scia0002-48;view=image;seq=00383;node=scia0002-48:1) [cited 2010-01-21].
[40] Dove, Patrick Edward, The theory of human progression, and natural probability of a reign of justice. London, Johnstone & Hunter, 1850.
LC 08031381 "Intelligence-Intelligent Design".
[41] Charles Darwin. Letter 3154—Darwin, C. R. to Herschel, J. F. W., 23 May 1861 (http:/ / www. darwinproject. ac. uk/ darwinletters/
calendar/ entry-3154. html); May 23, 1861.
[42] The British Association. September 20, 1873:10; col A.. The Times.
[43] William P. Alston. In: Paul Edwards. Encyclopedia of Philosophy. New York City, London: Macmillan Publishing Company, The Free
Press, Collier Macmillan Publishers; 1967. ISBN 0028949900.
[44] Robert Nozick. Anarchy, State, and Utopia. USA: Basic Books; 1974. ISBN 0465097200. p. 19.
[45] James E. Horigan. Chance or Design?. Philosophical Library; 1979.
[46] Nicholas Timmins. Evolution according to Hoyle: Survivors of disaster in an earlier world (http:/ / telicthoughts. com/
sir-fred-hoyle-and-the-origins-of-id/ ). January 13, 1982:22. "F. Hoyle stated in a 1982 speech: '...one arrives at the conclusion that
biomaterials with their amazing measure or order must be the outcome of intelligent design.'"
[47] Nick Matzke. National Center for Science Education. NCSE Resource -- 9.0. Matzke (2006): The Story of the Pandas Drafts (http:/ / ncse.
com/ rncse/ 26/ 1-2/ design-trial); 2006 [cited 2009-11-18]. *Nick Matzke. National Center for Science Education. Missing Link discovered!
(http:/ / www2. ncseweb. org/ wp/ ?p=80); 2006 [ archived (http:/ / web. archive. org/ web/ 20070114121029/ http:/ / www2. ncseweb. org/
wp/ ?p=80) 2007-01-14; cited 2009-11-18].
[48] Jonathan Witt. Discovery Institute. Evolution News & Views: Dover Judge Regurgitates Mythological History of Intelligent Design (http:/ /
www. evolutionnews. org/ 2005/ 12/ post_6. html); December 20, 2005 [cited 2007-10-05].
[49] DarkSyde. Daily Kos: Know Your Creationists: Know Your Allies (http:/ / www. dailykos. com/ story/ 2006/ 3/ 11/ 8448/ 52824); March
11, 2006 [cited 2007-10-05].
[50] William Safire. On Language: Neo-Creo (http:/ / www. nytimes. com/ 2005/ 08/ 21/ magazine/ 21ONLANGUAGE. html?position=&
ei=5090& en=f2de0d764cc7e0e8& ex=1282276800& adxnnl=1& partner=rssuserland& emc=rss& pagewanted=print&
adxnnlx=1132902202-gyP0H4EZfG7IeNHPMWlcBw). August 21, 2005.
[51] Nick Matzke. National Center for Science Education. NCSE Resource (http:/ / ncse. com/ creationism/ analysis/ critique-pandas-people);
2004 [cited 2007-09-24].
[52] Richard P. Aulie. National Association of Biology Teachers. A Reader's Guide to Of Pandas and People (http:/ / www. stephenjaygould.
org/ ctrl/ archive/ design/ aulie_of-pandas. html); 1998 [cited 2007-10-05].
[53] Eugenie C. Scott. Biological design in science classrooms (http:/ / www. pnas. org/ content/ 104/ suppl. 1/ 8669. full). Proceedings of the
National Academy of Sciences. May 15, 2007 [cited 2009-06-02];104(Suppl 1):8669–8676. doi:10.1073/pnas.0701505104 (http:/ / dx. doi.
org/ 10. 1073/ pnas. 0701505104). PMID 17494747. PMC 1876445 (http:/ / www. ncbi. nlm. nih. gov/ pmc/ articles/ PMC1876445/ ).
[54] Nick Matzke; Jon Buell (October 13, 2005). "I guess ID really was "Creationism's Trojan Horse" after all" (http:/ / www. pandasthumb. org/
archives/ 2005/ 10/ i_guess_id_real. html). The Panda's Thumb. . Retrieved 2009-06-02.
[55] William A. Dembski. Expert Witness Report: The Scientific Status of Intelligent Design (http:/ / www. designinference. com/ documents/
2005. 09. Expert_Report_Dembski. pdf) [PDF]. March 29, 2005 [cited 2009-06-02].
[56] Behe, Michael (1997): Molecular Machines: Experimental Support for the Design Inference (http:/ / www. apologetics. org/
MolecularMachines/ tabid/ 99/ Default. aspx)
[57] Irreducible complexity of these examples is disputed; see Kitzmiller, pp. 76–78, and Ken Miller Webcast (http:/ / www. pandasthumb. org/
archives/ 2006/ 01/ ken_miller_webc. html)
[58] The Collapse of "Irreducible Complexity" Kenneth R. Miller Brown University (http:/ / www. millerandlevine. com/ km/ evol/ design2/
article. html)
[59] John H. McDonald's " reducibly complex mousetrap (http:/ / udel. edu/ ~mcdonald/ mousetrap. html)"
[60] David Ussery, " A Biochemist's Response to 'The Biochemical Challenge to Evolution' (http:/ / www. cbs. dtu. dk/ staff/ dave/ Behe. html)"
[61] For example, Bridgham et al. (http:/ / www. sciencemag. org/ cgi/ content/ abstract/ 312/ 5770/ 97) showed that gradual evolutionary
mechanisms can produce complex protein-protein interaction systems from simpler precursors. Bridgham et al.. Evolution of
Hormone-Receptor Complexity by Molecular Exploitation. Science. 2006;312(5770):97–101. doi:10.1126/science.1123348 (http:/ / dx. doi.
org/ 10. 1126/ science. 1123348). PMID 16601189.
[62] Devolution (http:/ / www. newyorker. com/ archive/ 2005/ 05/ 30/ 050530fa_fact). May 30, 2005. The New Yorker. This article draws from
the following exchange of letters in which Behe admits to sloppy prose and non-logical proof: Discovery Institute. Has Darwin met his match?
Letters—An exchange over ID (http:/ / www. discovery. org/ scripts/ viewDB/ index. php?program=CRSC Responses& command=view&
Intelligent design 427

amp;id=1406); March 26, 2003 [cited 2006-11-30].

[63] Kitzmiller v. Dover Area School District, 04 cv 2688 (December 20, 2005)., p. 64.
[64] Dembski. Intelligent Design, p. 47
[65] William Dembski, Photo by Wesley R. Elsberry, taken at lecture given at University of California at Berkeley, 2006/03/17.
[66] Branden Fitelson, Christopher Stephens, Elliott Sober. How Not to Detect Design: A review of William A. Dembski's The Design
Inference—Eliminating Chance Through Small Probabilities (http:/ / philosophy. wisc. edu/ sober/ dembski. pdf) [PDF]. Cambridge
University Press; 1998.
[67] Some of Dembski's responses to assertions of specified complexity being a tautology can be found at William A. Dembski. "Another way to
detect design" (http:/ / www. arn. org/ docs/ dembski/ wd_anotherwaytodetectdesign. htm). ARN. .
[68] Richard Wein. Not a Free Lunch But a Box of Chocolates: A critique of William Dembski's book No Free Lunch (http:/ / www. talkorigins.
org/ design/ faqs/ nfl/ ); 2002.
[69] Rich Baldwin. Information Theory and Creationism (http:/ / www. talkorigins. org/ faqs/ information/ dembski. html); 2005.
[70] Mark Perakh. Dembski 'displaces Darwinism' mathematically -- or does he? (http:/ / www. talkreason. org/ articles/ newmath. cfm); 2005.
[71] Jason Rosenhouse. How Anti-Evolutionists Abuse Mathematics (http:/ / www. math. jmu. edu/ ~rosenhjd/ sewell. pdf) [PDF]. The
Mathematical Intelligencer. Fall 2001;23(4):3–8.
[72] John S. Wilkins, Wesley R. Elsberry. The Advantages of Theft over Toil: The Design Inference and Arguing from Ignorance (http:/ / www.
talkdesign. org/ cs/ theft_over_toil). Biology and Philosophy. 2001;16:711–724.
[73] Richard Dawkins. The God Delusion. Boston: Houghton Mifflin; 2006. ISBN 0618680004.
[74] Evolutionary algorithms now surpass human designers (http:/ / www. newscientist. com/ article/ mg19526146.
000-evolutionary-algorithms-now-surpass-human-designers. html). New Scientist. July 28, 2007.
[75] Guillermo Gonzalez. The Privileged Planet: How Our Place in the Cosmos is Designed for Discovery. Washington, DC: Regnery Publ.;
2004. ISBN 0-89526-065-4.
[76] The Panda's Thumb. review of The Privileged Planet (http:/ / www. pandasthumb. org/ archives/ 2004/ 08/ privileged_plan_4. html)
[77] Is The Universe Fine-Tuned For Us? (http:/ / www. colorado. edu/ philosophy/ vstenger/ Cosmo/ FineTune. pdf#search="Fine tuned
universe") Victor J. Stenger. University of Colorado. (PDF file)
[78] Victor J. Stenger. University of Colorado. The Anthropic Principle (http:/ / www. colorado. edu/ philosophy/ vstenger/ Cosmo/ ant_encyc.
pdf) [PDF].
[79] Joseph Silk. Our place in the Multiverse (http:/ / www. nature. com/ nature/ journal/ v443/ n7108/ full/ 443145a. html). Nature. September
14, 2006;443(7108).
[80] See, e.g., Gerald Feinberg and Robert Shapiro. A Puddlian Fable. In: Huchingson. Religion and the Natural Sciences. 1993. p. 220–221.
[81] Evolution's Thermodynamic Failure (http:/ / spectator. org/ archives/ 2005/ 12/ 28/ evolutions-thermodynamic-failu). The American
Spectator. December 28, 2005 [cited 2007-02-16]. (Also available from the Discovery Institute (http:/ / www. discovery. org/ scripts/
viewDB/ index. php?command=view& id=3122))
[82] TalkOrigins Archive. Entropy, Disorder and Life (http:/ / www. talkorigins. org/ faqs/ thermo/ entropy. html) [cited 2007-07-17].
[83] Dembski. Discovery Institute. Questions About Intelligent Design (http:/ / www. discovery. org/ csc/ topQuestions.
php#questionsAboutIntelligentDesign). "The theory of Intelligent Design holds that certain features of the universe and of living things are
best explained by an intelligent cause, not an undirected process such as natural selection."
[84] LeaderU. The Act of Creation: Bridging Transcendence and Immanence (http:/ / www. leaderu. com/ offices/ dembski/ docs/ bd-the_ac.
html).
[85] The Case Against Intelligent Design (http:/ / pondside. uchicago. edu/ cluster/ pdf/ coyne/ New_Republic_ID. pdf) [PDF]. The New
Republic. August 22–29, 2005 [ archived (http:/ / web. archive. org/ web/ 20060618235930/ http:/ / pondside. uchicago. edu/ cluster/ pdf/
coyne/ New_Republic_ID. pdf) 2006-06-18];233(8/9):21–33.
[86] Donald E. Simanek. Intelligent Design: The Glass is Empty (http:/ / www. lhup. edu/ ~dsimanek/ philosop/ empty. htm).
[87] IDEA "One need not fully understand the origin or identity of the designer to determine that an object was designed. Thus, this question is
essentially irrelevant to intelligent design theory, which merely seeks to detect if an object was designed ... Intelligent design theory cannot
address the identity or origin of the designer—it is a philosophical / religious question that lies outside the domain of scientific inquiry.
Christianity postulates the religious answer to this question that the designer is God who by definition is eternally existent and has no origin.
There is no logical philosophical impossibility with this being the case (akin to Aristotle's 'unmoved mover') as a religious answer to the
origin of the designer..." FAQ: Who designed the designer? FAQ: Who designed the designer? (http:/ / www. ideacenter. org/ contentmgr/
showdetails. php/ id/ 1147)
[88] Jason Rosenhouse. Committee for the Scientific Investigation of Claims of the Paranormal. Who Designed the Designer? (http:/ / www.
csicop. org/ intelligentdesignwatch/ designer. html).
[89] Richard Dawkins. The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe without Design. p. 141.
[90] See, e.g., Joseph Manson. Intelligent design is pseudoscience (http:/ / www. today. ucla. edu/ portal/ ut/ 050927voices_pseudoscience. aspx);
September 27, 2005.; Rev Max (July–August 2006). "The Incredibly Strange Story of Intelligent Design". New Dawn Magazine (97).
[91] NCSE Resource (http:/ / ncse. com/ creationism/ general/ evolving-banners-at-discovery-institute); August 29, 2002 [cited 2007-10-07].
[92] Conclusion of Kitzmiller v. Dover Area School District Ruling
[93] Wise, D.U., 2001, Creationism's Propaganda Assault on Deep Time and Evolution, Journal of Geoscience Education, v. 49, n. 1, p. 30–35.
Intelligent design 428

[94] Marcus R. Ross. Who Believes What? Clearing up Confusion over Intelligent Design and Young-Earth Creationism (http:/ / nagt. org/ files/
nagt/ jge/ abstracts/ Ross_v53n3p319. pdf) [PDF]. Journal of Geoscience Education. May, 2005;53(3):319–323.
[95] Ronald L. Numbers. The Creationists: From Scientific Creationism to Intelligent Design, Expanded Edition. Cambridge, Massachusetts:
Harvard University Press; November 30, 2006. ISBN 0674023390.
[96] Forrest, B.C. and Gross, P.R.. Evolution and the Wedge of Intelligent Design: The Trojan Horse Strategy. Oxford: Oxford University Press;
2003. ISBN 0195157427.
[97] Robert T. Pennock. Wizards of ID: Reply to Dembski. In: Robert T. Pennock. Intelligent Design Creationism and Its Critics: Philosophical,
Theological, and Scientific Perspectives (http:/ / www. metanexus. net/ magazine/ ArticleDetail/ tabid/ 68/ id/ 2645/ Default. aspx).
Cambridge, Massachusetts: MIT Press; 2001. ISBN 0262661241. "Dembski chides me for never using the term "intelligent design" without
conjoining it to "creationism". He implies (though never explicitly asserts) that he and others in his movement are not creationists and that it
is incorrect to discuss them in such terms, suggesting that doing so is merely a rhetorical ploy to "rally the troops". (2) Am I (and the many
others who see Dembski's movement in the same way) misrepresenting their position? The basic notion of creationism is the rejection of
biological evolution in favor of special creation, where the latter is understood to be supernatural. Beyond this there is considerable
variability..." p. 645–667.; Pennock, Robert T.. Tower of Babel: Evidence Against the New Creationism. Cambridge, Massachusetts: MIT
Press; 1999.
[98] Eugenie Scott. The Creation/Evolution Continuum (http:/ / ncse. com/ creationism/ general/ creationevolution-continuum). NCSE Reports.
1999;19(4):16–17, 23–25.; Scott, Eugenie C.. Evolution vs. Creationism: An Introduction. Westport, Connecticut: Greenwood Press; 2004.
ISBN 0520246500.
[99] "The social consequences of materialism have been devastating. As symptoms, those consequences are certainly worth treating. However,
we are convinced that in order to defeat materialism, we must cut it off at its source. That source is scientific materialism. This is precisely our
strategy. If we view the predominant materialistic science as a giant tree, our strategy is intended to function as a 'wedge' that, while
relatively small, can split the trunk when applied at its weakest points. The very beginning of this strategy, the 'thin edge of the wedge,' was
Phillip Johnson's critique of Darwinism begun in 1991 in Darwinism on Trial, and continued in Reason in the Balance and Defeating
Darwinism by Opening Minds. Michael Behe's highly successful Darwin's Black Box followed Johnson's work. We are building on this
momentum, broadening the wedge with a positive scientific alternative to materialistic scientific theories, which has come to be called the
theory of intelligent design (ID). Design theory promises to reverse the stifling dominance of the materialist worldview, and to replace it with
a science consonant with Christian and theistic convictions". Wedge Document (http:/ / www. antievolution. org/ features/ wedge. pdf)
Discovery Institute, 1999. (PDF file)
[100] "I have built an intellectual movement in the universities and churches that we call The Wedge, which is devoted to scholarship and writing
that furthers this program of questioning the materialistic basis of science. [...] Now the way that I see the logic of our movement going is like
this. The first thing you understand is that the Darwinian theory isn't true. It's falsified by all of the evidence and the logic is terrible. When
you realize that, the next question that occurs to you is, well, where might you get the truth? [...] I start with John 1:1. In the beginning was
the word. In the beginning was intelligence, purpose, and wisdom. The Bible had that right. And the materialist scientists are deluding
themselves." Johnson 1999. Reclaiming America for Christ Conference. How the Evolution Debate Can Be Won (http:/ / web. archive. org/
web/ 20071107005414/ http:/ / www. coralridge. org/ specialdocs/ evolutiondebate. asp)
[101] Discovery Institute fellows and staff (http:/ / www. discovery. org/ fellows/ ). "Center for Science and Culture fellows and staff" (http:/ /
www. discovery. org/ csc/ fellows. php). .
[102] Barbara Forrest. The Wedge at Work: Intelligent Design Creationism and Its Critics (http:/ / www. infidels. org/ library/ modern/
barbara_forrest/ wedge. html); 2001.
[103] "...intelligent design does not address metaphysical and religious questions such as the nature or identity of the designer," and "...the nature,
moral character and purposes of this intelligence lie beyond the competence of science and must be left to religion and philosophy". In:
Discovery Institute. Truth Sheet # 09-05 Does intelligent design postulate a "supernatural creator? (http:/ / www. discovery. org/ scripts/
viewDB/ filesDB-download. php?command=download& id=565) [cited 2007-07-19].
[104] Phillip Johnson. 'Keeping the Darwinists Honest' an interview with Phillip Johnson. 1999. "Intelligent Design is an intellectual movement,
and the Wedge strategy stops working when we are seen as just another way of packaging the Christian evangelical message. [...] The
evangelists do what they do very well, and I hope our work opens up for them some doors that have been closed".
[105] Phillip Johnson. Touchstone: A Journal of Mere Christianity. 1999. "...the first thing that has to be done is to get the Bible out of the
discussion. ...This is not to say that the biblical issues are unimportant; the point is rather that the time to address them will be after we have
separated materialist prejudice from scientific fact". The Wedge (http:/ / www. arn. org/ docs/ johnson/ le_wedge. htm)
[106] William Dembski, 1998. The Design Inference.
[107] Dembski, 1999. Intelligent Design: The Bridge Between Science and Theology, p. 210.
[108] William Dembski. Intelligent Design's Contribution to the Debate Over Evolution: A Reply to Henry Morris (http:/ / www.
designinference. com/ documents/ 2005. 02. Reply_to_Henry_Morris. htm); 2005.
[109] Barbara Forrest. Expert Testimony. Kitzmiller v. Dover Area School District trial transcript, Day 6 (October 5) "What I am talking about is
the essence of intelligent design, and the essence of it is theistic realism as defined by Professor Johnson. Now that stands on its own quite
apart from what their motives are. I'm also talking about the definition of intelligent design by Dr. Dembski as the Logos theology of John's
Gospel. That stands on its own. [...] Intelligent design, as it is understood by the proponents that we are discussing today, does involve a
supernatural creator, and that is my objection. And I am objecting to it as they have defined it, as Professor Johnson has defined intelligent
design, and as Dr. Dembski has defined intelligent design. And both of those are basically religious. They involve the supernatural".
Intelligent design 429

[110] Center for Inquiry, Office of Public Policy. Understanding the Intelligent Design Creationist Movement: Its True Nature and Goals. A
Position Paper (http:/ / www. centerforinquiry. net/ uploads/ attachments/ intelligent-design. pdf) [PDF]; 2007 May.
[111] H. Ross. Pasadena, California: Reasons to Believe. More than intelligent design (http:/ / www. reasons. org/ resources/ fff/ 2002issue10/
index. shtml#more_than_id); 2002 [cited April 25, 2007].
[112] Henry M. Morris. Santee, California: Institute for Creation Research. Design is not enough! (http:/ / www. icr. org/ article/ 859/ 17/ ); 1999
[cited April 25, 2007].
[113] Carl Wieland. Answers in Genesis. AiG's views on the Intelligent Design movement (http:/ / www. answersingenesis. org/ docs2002/
0830_IDM. asp); 2002 [cited April 25, 2007].
[114] Harris Interactive. Nearly Two-thirds of U.S. Adults Believe Human Beings Were Created by God (http:/ / www. harrisinteractive. com/
harris_poll/ index. asp?PID=581); July 6, 2005 [cited 2007-07-13].
[115] New Mexicans for Science and Reason. Sandia National Laboratories says that the Intelligent Design Network (IDNet-NM/Zogby) "Lab
Poll" is BOGUS! (http:/ / www. nmsr. org/ id-poll. htm) [cited 2007-07-13].
[116] Committee for Skeptical Inquiry. Polling for ID (http:/ / www. csicop. org/ doubtandabout/ polling/ ); September 11, 2003 [ archived (http:/
/ web. archive. org/ web/ 20080327041611/ http:/ / csicop. org/ doubtandabout/ polling/ ) 2008-03-27; cited 2007-02-16].
[117] David Harris. Salon.com. 'Intelligent Design'-ers launch new assault on curriculum using lies and deception (http:/ / blogs. salon. com/
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[118] According to the poll, 18% of the physicians believed that God created humans exactly as they appear today. Another 42% believed that
God initiated and guided an evolutionary process that has led to current human beings. The poll also found that "an overwhelming majority of
Jewish doctors (83%) and half of Catholic doctors (51%) believe that intelligent design is simply "a religiously inspired pseudo-science rather
than a legitimate scientific speculation". The poll also found that "more than half of Protestant doctors (63%) believe that intelligent design is
a "legitimate scientific speculation".
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[119] Gallup, "Evolution, creationism, intelligent design," (http:/ / www. gallup. com/ poll/ 21814/ evolution-creationism-intelligent-design.
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[120] Expelled, No Intelligence Allowed (2008) (http:/ / www. imdb. com/ title/ tt1091617/ ).
[121] New Anti-Evolution Film Stirs Controversy (http:/ / www. livescience. com/ strangenews/ 080404-expelled-movie. html).
[122] Shaw, Linda. Does Seattle group "teach controversy" or contribute to it? (http:/ / seattletimes. nwsource. com/ html/ localnews/
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[123] National Association of Biology Teachers. NABT's Statement on Teaching Evolution (http:/ / www. nabt. org/ sub/ position_statements/
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[124] The Interacademy Panel on International Issues. IAP Statement on the Teaching of Evolution (http:/ / www. interacademies. net/ Object.
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[125] From the world's largest general scientific society:
• American Association for the Advancement of Science (February 16, 2006). "Statement on the Teaching of Evolution" (http:/ / www. aaas.
org/ news/ releases/ 2006/ pdf/ 0219boardstatement. pdf) (PDF). Press release. . Retrieved 2008-10-17.
• American Association for the Advancement of Science (February 19, 2006). "AAAS Denounces Anti-Evolution Laws" (http:/ / www.
aaas. org/ news/ releases/ 2006/ 0219boardstatement. shtml). Press release. . Retrieved 2008-10-17.
[126] Intelligent design a Trojan horse, says creationist (http:/ / www. smh. com. au/ news/ world/
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[127] Americans United for the Separation of Church and State. Intelligent Design: Creationism's Trojan Horse (http:/ / www. au. org/ site/
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[128] The Evolution Wars (http:/ / www. time. com/ time/ magazine/ article/ 0,9171,1090909,00. html). August 7, 2005 [cited 2007-07-23]. Time
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[129] National Center for Science Education. "The evolution wars" in Time (http:/ / ncse. com/ news/ 2005/ 08/ evolution-wars-time-00696);
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• Journalism and the Debate Over Origins: Newspaper Coverage of Intelligent Design. Journal of Media and Religion. 2006;5(1):49–61.
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• Television wildlife programming as a source of popular scientific information: a case study of evolution. Public Understanding of Science.
2006;15:131–152. doi:10.1177/0963662506060588 (http:/ / dx. doi. org/ 10. 1177/ 0963662506060588).
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[130] DeWolf, David K. Intelligent Design Will Survive Kitzmiller v. Dover (http:/ / www. umt. edu/ mlr/ Discovery Institute Article. pdf)
[PDF]. University of Montana Law Review. May 4, 2007;68(1).
Intelligent design 430

• Does God have a place in class?: Intelligent design ignites great debate (http:/ / www. discovery. org/ a/ 2920). Calgary Herald.
2005-08-25 [cited 2009-02-16].
• The Politically Incorrect Guide to Darwinism and Intelligent Design (http:/ / books. google. com/ ?id=H8yn0iaRRfoC& pg=PA1&
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[133] Reason in the Balance: The Case Against Naturalism in Science, Law and Education. InterVarsity Press; 1995. ISBN
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[134] Phillip E. Johnson. Access Research Network. Starting a Conversation about Evolution: Johnson, Phillip (http:/ / www. arn. org/ docs/
johnson/ ratzsch. htm); August 31, 1996 [cited 2008-10-18]. "My colleagues and I speak of 'theistic realism'—or sometimes, 'mere
creation'—as the defining concept of our [the ID] movement. This means that we affirm that God is objectively real as Creator, and that the
reality of God is tangibly recorded in evidence accessible to science, particularly in biology."
[135] See, for instance: University of Texas, Austin. Methodological Naturalism and the Supernatural (http:/ / www. utexas. edu/ cola/ depts/
philosophy/ faculty/ koons/ ntse/ papers/ Vuletic. html); 1997 February [ archived (http:/ / web. archive. org/ web/ 20080114094157/ http:/ /
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[136] Los Angeles Times. Enlisting Science to Find the Fingerprints of a Creator (http:/ / www. discovery. org/ scripts/ viewDB/ index.
php?programs=CSCstories& command=view& id=613); March 25, 2001 [cited 2007-07-22]. "[Phillip E. Johnson quoted]: We are taking an
intuition most people have and making it a scientific and academic enterprise ... We are removing the most important cultural roadblock to
accepting the role of God as creator."
[137] Witnesses For The Prosecution (http:/ / www. leaderu. com/ pjohnson/ world2. html) [Reprint by Leadership U.]. World Magazine.
November 30, 1996 [cited 2007-07-23];11(28):18.
[138] The Evangelical Fellowship of Canada. Let's Be Intelligent About Darwin (http:/ / www. christianity. ca/ news/ social-issues/ 2004/ 03.
001. html); January 10, 2003 [ archived (http:/ / web. archive. org/ web/ 20070608233455/ http:/ / www. christianity. ca/ news/ social-issues/
2004/ 03. 001. html) 2007-06-08; cited 2007-07-23]. "[Phillip E. Johnson quoted]: Our strategy has been to change the subject a bit so that we
can get the issue of Intelligent Design, which really means the reality of God, before the academic world and into the schools."
[139] The Foundation for Thought and Ethics, Dallas Christian Leadership, and the C. S. Lewis Fellowship. Darwinism: Science or Philosophy
(http:/ / ebd10. ebd. csic. es/ pdfs/ DarwSciOrPhil. pdf) [PDF]; 1992 March [cited 2007-07-23].
[140] Intelligent design's long march to nowhere (http:/ / www. templeton. org/ capabilities_2004/ press02. html). Templeton Foundation,
Science & Theology News; December 5, 2005 [cited 2007-07-23].
[141] What is wrong with intelligent design? (http:/ / philosophy. wisc. edu/ sober/ what's wrong with id qrb 2007. pdf) [PDF]. Quarterly Review
of Biology. 2007 [cited 2007-07-23];82(1):3–6. doi:10.1086/511656 (http:/ / dx. doi. org/ 10. 1086/ 511656).
[142] Science Daily. What Is Wrong With Intelligent Design? (http:/ / www. sciencedaily. com/ releases/ 2007/ 02/ 070222155420. htm);
February 23, 2007 [cited 2007-07-23].
[143] Franklin & Marshall College. Natural Providence (or Design Trouble) (http:/ / edisk. fandm. edu/ michael. murray/ Providence. pdf) [PDF];
Forthcoming [cited 2007-07-23].
[144] Creighton University. What is the position of the NRCSE on the teaching of intelligent design [ID] as an alternative to neo-Darwinian
evolution in Nebraska schools? (http:/ / puffin. creighton. edu/ NRCSE/ NRCSEPosReID. html) [cited 2007-07-23].
[145] Bring You To. Catechetical Lecture at St. Stephan's Cathedral, Vienna (http:/ / www. bringyou. to/ apologetics/ p91. htm) [Reprint];
October 2, 2005 [cited 2007-07-22]. "Purpose and design in the natural world, [has] no difficulty [...] with the theory of evolution [within] the
borders of scientific theory."
[146] National Center for Science Education. The Creation/Evolution Continuum (http:/ / ncse. com/ creationism/ general/
creationevolution-continuum); December 7, 2000 [cited 2009-11-18].
[147] National Council of Churches. Science, Religion, and the Teaching of Evolution in Public School Science Classes (http:/ / www. ncccusa.
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[148] Creighton University. Intelligent Design as a Theological Problem (http:/ / puffin. creighton. edu/ NRCSE/ IDTHG. html) [Reprint]; 2002
[cited 2007-07-21].
[149] Answers in Genesis. Intelligent design: is it intelligent; is it Christian? (http:/ / www. answersingenesis. org/ articles/ wow/
is-idm-christian); February 4, 2006 [cited 2007-07-21].
[150] Reasons to Believe. More Than Intelligent Design (http:/ / www. reasons. org/ resources/ fff/ 2002issue10/ index. shtml#more_than_id)
[cited 2007-07-21].
[151] Harun Yahya International (2007). "The "Intelligent Design" Distraction" (http:/ / www. harunyahya. com/ new_releases/ news/
intelligent_design. php). Press release. . Retrieved 2007-07-20.
[152] Answers in Genesis. AiG's views on the Intelligent Design Movement (http:/ / www. answersingenesis. org/ docs2002/ 0830_IDM. asp);
August 30, 2002 [cited 2007-07-20].
[153] Natan Slifkin (2006). The Challenge of Creation (New York: Yashar Books) 288 ff.
[154] Miller, Kenneth. Debating Design. Cambridge University Press; 2004. The Flagellum Unspun. p. 95.
Intelligent design 431

[155] Center for Science and Culture, Discovery Institute. The Scientific Status of Intelligent Design: The Methodological Equivalence of
Naturalistic and Non-Naturalistic Origins Theories (http:/ / www. discovery. org/ scripts/ viewDB/ index. php?command=view& id=1780);
December 1, 2002 [cited 2007-07-19].
[156] University of California at San Diego. Demarcating science vis-à-vis pseudoscience (http:/ / philosophyfaculty. ucsd. edu/ faculty/
wuthrich/ teaching/ 2007_145/ Lecture02. pdf) [PDF]; January 11, 2007 [ archived (http:/ / web. archive. org/ web/ 20070724203349/ http:/ /
philosophyfaculty. ucsd. edu/ faculty/ wuthrich/ teaching/ 2007_145/ Lecture02. pdf) 2007-07-24; cited 2007-07-19].
[157] Scientific Method in Practice. Cambridge UP; 2003. ISBN 0521017084. Chapters 5–8. Discusses principles of induction, deduction and
probability related to the expectation of consistency, testability, and multiple observations. Chapter 8 discusses parsimony (Occam's razor)
[158] Research Methods in Psychology. 8th ed. Wadsworth Publishing; 2005. ISBN 0534609767. Chapter 2. Discusses the scientific method,
including the principles of falsifiability, testability, progressive development of theory, dynamic self-correcting of hypotheses, and parsimony,
or "Occam's razor".
[159] Kitzmiller v. Dover Area School District, cv 2688 (December 20, 2005)., 4: whether ID is science. The ruling discusses central aspects of
expectations in the scientific community that a scientific theory be testable, dynamic, correctible, progressive, based upon multiple
observations, and provisional,
[160] See, e.g., Mark Perakh. Talk Reason. The Dream World of William Dembski's Creationism (http:/ / talkreason. com/ articles/
Skeptic_paper. cfm); 2005; p. 54–65.
[161] Intelligent design fails to pass Occam's razor. Adding entities (an intelligent agent, a designer) to the equation is not strictly necessary to
explain events. See, e.g., Branden Fitelson, et al.. How Not to Detect Design–Critical Notice: William A. Dembski The Design Inference. In:
Robert T. Pennock. Intelligent Design Creationism and Its Critics: Philosophical, Theological, and Scientific Perspectives. MIT Press; 2001.
p. 597–616.
[162] See, e.g., Department of Biological Sciences, Lehigh University. Thoughts on Evolution and Intelligent Design (http:/ / www. lehigh. edu/
~inbios/ schneider/ evolution. htm); 2005. "Q: Why couldn't intelligent design also be a scientific theory? A: The idea of intelligent design
might or might not be true, but when presented as a scientific hypothesis, it is not useful because it is based on weak assumptions, lacks
supporting data and terminates further thought."
[163] The designer is not falsifiable, since its existence is typically asserted without sufficient conditions to allow a falsifying observation. The
designer being beyond the realm of the observable, claims about its existence can be neither supported nor undermined by observation,
making intelligent design and the argument from design analytic a posteriori arguments. See, e.g., Kitzmiller v. Dover Area School District, cv
2688 (December 20, 2005). Ruling, p. 22 and p. 77.
[164] That intelligent design is not empirically testable stems from the fact that it violates a basic premise of science, naturalism. See, e.g.,
Kitzmiller v. Dover Area School District, cv 2688 (December 20, 2005). Ruling, p. 22 and p. 66.
[165] Intelligent design professes to offer an answer that does not need to be defined or explained, the intelligent agent, designer. By asserting a
conclusion that cannot be accounted for scientifically, the designer, intelligent design cannot be sustained by any further explanation, and
objections raised to those who accept intelligent design make little headway. Thus intelligent design is not a provisional assessment of data
which can change when new information is discovered. Once it is claimed that a conclusion that need not be accounted for has been
established, there is simply no possibility of future correction. The idea of the progressive growth of scientific ideas is required to explain
previous data and any previously unexplainable data. See, e.g., the brief explanation in Kitzmiller v. Dover Area School District, 04 cv 2688
(December 20, 2005). p. 66.
[166] "Nobel Laureates Initiative" (http:/ / media. ljworld. com/ pdf/ 2005/ 09/ 15/ nobel_letter. pdf) (PDF). The Elie Wiesel Foundation for
Humanity. September 9, 2005. . Retrieved 2007-07-19. The September 2005 statement by 38 Nobel laureates stated that: "Intelligent design is
fundamentally unscientific; it cannot be tested as scientific theory because its central conclusion is based on belief in the intervention of a
supernatural agent".
[167] Intelligent Design is not Science: Scientists and teachers speak out (http:/ / web. archive. org/ web/ 20060614003243/ www. science. unsw.
edu. au/ news/ 2005/ intelligent. html). 2005 October [cited 2009-01-09]. University of New South Wales. The October 2005 statement, by a
coalition representing more than 70,000 Australian scientists and science teachers said: "intelligent design is not science" and called on "all
schools not to teach Intelligent Design (ID) as science, because it fails to qualify on every count as a scientific theory".
[168] PZ Myers, Pharyngula.org. Creationism and the Daubert test? (http:/ / pharyngula. org/ index/ science/ comments/
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[169] Nagel, Thomas. "Public Education and Intelligent Design" (http:/ / www. stanford. edu/ ~joelv/ teaching/ 167/ nagel 08 - public education
and intelligent design. pdf), Philosophy and Public Affairs, Vol. 36, no. 2, 2008, pp. 196–197.
[170] National Academy of Sciences. Science and Creationism: A View from the National Academy of Sciences (http:/ / www. nap. edu/
openbook. php?isbn=0309064066& page=25); 1999.
[171] National Science Teachers Association, a professional association of 55,000 science teachers and administrators National Science Teachers
Association (August 3, 2005). "National Science Teachers Association Disappointed About Intelligent Design Comments Made by President
Bush" (http:/ / www. nsta. org/ about/ pressroom. aspx?id=50794). Press release. . "We stand with the nation's leading scientific organizations
and scientists, including Dr. John Marburger, the president's top science advisor, in stating that intelligent design is not science. ...It is simply
not fair to present pseudoscience to students in the science classroom."
[172] Evolution critics seek role for unseen hand in education. Nature. 2002;416(6878):250. doi:10.1038/416250a (http:/ / dx. doi. org/ 10. 1038/
416250a). PMID 11907537. "But many scientists regard ‘intelligent design’ as pseudoscience, and say that it is being used as a Trojan Horse to
introduce the teaching of creationism into schools"
Intelligent design 432

[173] Attie, A. D.. Defending science education against intelligent design: a call to action (http:/ / www. jci. org/ articles/ view/ 28449). Journal
of Clinical Investigation. 2006;116(5):1134–1138. doi:10.1172/JCI28449 (http:/ / dx. doi. org/ 10. 1172/ JCI28449). PMID 16670753. PMC
1451210 (http:/ / www. ncbi. nlm. nih. gov/ pmc/ articles/ PMC1451210/ ).
• H. Allen Orr. New Yorker. Devolution—Why intelligent design isn't (http:/ / www. newyorker. com/ archive/ 2005/ 05/ 30/
050530fa_fact); 2005 May. "Biologists aren't alarmed by intelligent design's arrival in Dover and elsewhere because they have all sworn
allegiance to atheistic materialism; they're alarmed because intelligent design is junk science."
• Robert T. Pennock Tower of Babel: The Evidence Against the New Creationism.
• Mark Bergin. World Magazine. Junk science (http:/ / www. worldmag. com/ articles/ 11553); February 25, 2006.
[174] Junk Science (http:/ / books. google. com/ ?id=kHeQhdNQvrUC& pg=PA210& lpg=PA210& dq=intelligent+ design+ junk-science).
Macmillan; 2006. ISBN 9780312352417. p. 210 ff.
[175] Kitzmiller v. Dover Area School District, cv 2688 (December 20, 2005)., 4. Whether ID is Science, p. 87
[176] Free Speech on Evolution Campaign Main Page (http:/ / www. discovery. org/ csc/ freeSpeechEvolCampMain. php) Discovery Institute,
Center for Science and Culture.
[177] John Hawks Weblog. The President and the teaching of evolution (http:/ / johnhawks. net/ weblog/ topics/ creation/
bush_intelligent_design_2005. html); 2005 August [cited 2007-07-19].
[178] Skeptic: eSkeptic: Thursday, April 17th, 2008 (http:/ / www. skeptic. com/ eskeptic/ 08-04-17. html#part1)
[179] Intelligent Design Might Be Meeting Its Maker (http:/ / www. nytimes. com/ 2005/ 12/ 04/ weekinreview/ 04good. html?ex=1291352400&
en=feb5138e425b9001& ei=5088& partner=rssnyt& emc=rss). December 4, 2005 [cited 2007-07-19]. New York Times.
[180] Statement from the Council of the Biological Society of Washington (http:/ / web. archive. org/ web/ 20070926214521/ http:/ / www.
biolsocwash. org/ id_statement. html) at the Wayback Machine (archived September 26, 2007).
[181] Meyer, S.C.. The origin of biological information and the higher taxonomic categories (http:/ / www. discovery. org/ scripts/ viewDB/
filesDB-download. php?command=download& id=549). Proceedings of the Biological Society of Washington. 2004 [cited
2007-05-10];117(2):213–239.
[182] The Sternberg peer review controversy and several similar academic disputes are the subject of the 2008 documentary "Expelled: No
Intelligence Allowed".
[183] Design Inference Website. Is Intelligent Design a Form of Natural Theology? (http:/ / www. designinference. com/ documents/ 2001. 03.
ID_as_nat_theol. htm); 2001 [cited 2007-07-19].
[184] Darwinism Under Attack (http:/ / chronicle. com/ free/ v48/ i17/ 17a00801. htm); December 21, 2001 [cited 2008-12-10].
[185] Ruling, Kitzmiller v. Dover Area School District 4: whether ID is science
[186] Simulating evolution by gene duplication of protein features that require multiple amino acid residues (http:/ / www3. interscience. wiley.
com/ cgi-bin/ fulltext/ 121602290/ HTMLSTART). Protein Science. October 2004 [cited 16 March 2009];13(10):2651–64.
doi:10.1110/ps.04802904 (http:/ / dx. doi. org/ 10. 1110/ ps. 04802904). PMID 15340163. PMC 2286568 (http:/ / www. ncbi. nlm. nih. gov/
pmc/ articles/ PMC2286568/ ).
[187] Kitzmiller v. Dover Area School District, 04 cv 2688 (December 20, 2005). 4: whether ID is science
[188] Simple evolutionary pathways to complex proteins (http:/ / www. ncbi. nlm. nih. gov/ pmc/ articles/ PMC2253472/ ). Protein Science.
September 2005 [cited 16 March 2009];14(9):2217–2225. doi:10.1110/ps.041171805 (http:/ / dx. doi. org/ 10. 1110/ ps. 041171805). PMID
16131652.
[189] Kitzmiller v. Dover Area School District, October 19, 2005, AM session Kitzmiller Testimony, Behe (http:/ / www. talkorigins. org/ faqs/
dover/ day12am. html)
[190] Discovery Institute. Peer-Reviewed, Peer-Edited, and other Scientific Publications Supporting the Theory of Intelligent Design (Annotated)
(http:/ / www. discovery. org/ scripts/ viewDB/ index. php?command=view& id=2640& program=CSC - Scientific Research and Scholarship
- Science); 2007 July [cited 2007-07-17].
[191] Is It Science Yet?: Intelligent Design Creationism and the Constitution (http:/ / lawreview. wustl. edu/ inprint/ 83-1/ p 1 Brauer Forrest Gey
book pages. pdf) [PDF]. Washington University Law Quarterly. 2005 [cited 2007-07-18];83(1). "ID leaders know the benefits of submitting
their work to independent review and have established at least two purportedly "peer-reviewed" journals for ID articles. However, one has
languished for want of material and quietly ceased publication, while the other has a more overtly philosophical orientation. Both journals
employ a weak standard of "peer review" that amounts to no more than vetting by the editorial board or society fellows."
[192] TalkOrigins Archive. Index to Creationist Claims (http:/ / www. talkorigins. org/ indexcc/ CI/ CI001_4. html); 2006. "With some of the
claims for peer review, notably Campbell and Meyer (2003) and the e-journal PCID, the reviewers are themselves ardent supporters of
intelligent design. The purpose of peer review is to expose errors, weaknesses, and significant omissions in fact and argument. That purpose is
not served if the reviewers are uncritical"
[193] Natural History Magazine. Detecting Design in the Natural Sciences (http:/ / www. actionbioscience. org/ evolution/ nhmag. html); 2002
April [cited 2007-07-18].
[194] Space.com. SETI and Intelligent Design (http:/ / www. space. com/ searchforlife/ seti_intelligentdesign_051201. html); 2005 December
[cited 2007-07-18]. "In fact, the signals actually sought by today's SETI searches are not complex, as the ID advocates assume. [...] If SETI
were to announce that we're not alone because it had detected a signal, it would be on the basis of artificiality"
[195] "For human artifacts, we know the designer's identity, human, and the mechanism of design, as we have experience based upon empirical
evidence that humans can make such things, as well as many other attributes including the designer's abilities, needs, and desires. With ID,
proponents assert that they refuse to propose hypotheses on the designer's identity, do not propose a mechanism, and the designer,
Intelligent design 433

he/she/it/they, has never been seen. In that vein, defense expert Professor Minnich agreed that in the case of human artifacts and objects, we
know the identity and capacities of the human designer, but we do not know any of those attributes for the designer of biological life. In
addition, Professor Behe agreed that for the design of human artifacts, we know the designer and its attributes and we have a baseline for
human design that does not exist for design of biological systems. Professor Behe's only response to these seemingly insurmountable points of
disanalogy was that the inference still works in science fiction movies".—Kitzmiller v. Dover Area School District, cv 2688 (December 20,
2005)., p. 81
[196] Skeptical Inquirer Magazine. Darwin in Mind: Intelligent Design Meets Artificial Intelligence (http:/ / www. csicop. org/ si/ 2001-03/
intelligent-design. html); 2001 March/April [ archived (http:/ / web. archive. org/ web/ 20011018142820/ http:/ / www. csicop. org/ si/
2001-03/ intelligent-design. html) 2001-10-18; cited 2007-07-17].
[197] Intelligent Design and Evolution Awareness Center. Primer: Intelligent Design Theory in a Nutshell (http:/ / www. ideacenter. org/
contentmgr/ showdetails. php/ id/ 1136); 2007 [cited 2007-07-14].
[198] National Center for Science Education. "Intelligent Design" Not Accepted by Most Scientists (http:/ / ncse. com/ creationism/ general/
intelligent-design-not-accepted-by-most-scientists); 2002 September [cited 2009-11-18].
[199] Del Ratzsch (2005) "Teleological Arguments for God's Existence", Section 4.3, The “Intelligent Design” (ID) Movement (http:/ / plato.
stanford. edu/ entries/ teleological-arguments/ #4. 3), in Stanford Encyclopedia of Philosophy.
[200] See, for instance: Man Come Of Age: Bonhoeffer's Response To The God-Of-The-Gaps. Journal of the Evangelical Theological Society.
1971;14:203–220.
[201] Intelligent Design on Trial: Kitzmiller v. Dover (http:/ / ncse. com/ creationism/ legal/ intelligent-design-trial-kitzmiller-v-dover). National
Center for Science Education. October 17th, 2008
[202] Tammy Kitzmiller, et al. v. Dover Area School District, et al.', (http:/ / www. pamd. uscourts. gov/ kitzmiller/ 04cv2688-111. pdf) .
[203] Judge Rules Against 'Intelligent Design' (http:/ / pewforum. org/ news/ display. php?NewsID=5945). The Washington Post. December 21,
2005 [ archived (http:/ / web. archive. org/ web/ 20070928055938/ http:/ / pewforum. org/ news/ display. php?NewsID=5945) 2007-09-28;
cited 2007-09-03].
[204] Kitzmiller v. Dover Area School District, 04 cv 2688 (December 20, 2005)., pp. 137 – 138.
[205] Discovery Institute. Dover Intelligent Design Decision Criticized as a Futile Attempt to Censor Science Education (http:/ / www.
evolutionnews. org/ 2005/ 12/ dover_intelligent_design_decis. html); December 20, 2005 [cited 2007-09-03].
[206] Judge rules against 'intelligent design' (http:/ / www. msnbc. msn. com/ id/ 10545387/ ). December 20, 2005 [cited 2008-10-17].
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[207] Godless: The Church of Liberalism (http:/ / www. skeptic. com/ eskeptic/ 06-09-21. html); September 21, 2006 [cited 2007-09-03].
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[219] 'Design' attack on school science (http:/ / news. bbc. co. uk/ 1/ hi/ education/ 5392096. stm). September 29, 2006 [cited 2007-07-13]. BBC
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education/ tussle-of-biblical-proportions-over-creationism-in-ulster-classrooms-13479246. html). Belfast Telegraph. September 26, 2007
[cited 2007-10-01].
* Viewpoint: The world, according to Lisburn folk (http:/ / www. belfasttelegraph. co. uk/ opinion/
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[228] Enserink, Martin. Evolution Politics: Is Holland Becoming the Kansas of Europe? (http:/ / www. sciencemag. org/ cgi/ content/ summary/
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References

Further reading
• Gross PR; Forrest B. Creationism's Trojan Horse: the Wedge of Intelligent Design. Oxford [Oxfordshire]: Oxford
University Press; 2004. ISBN 0-19-515742-7. Preview (http://books.google.ca/books?id=raqJjM9LkeAC&
printsec=frontcover#v=onepage&q&f=false) at Google Books
• Humes E. Monkey Girl: Evolution, Education, Religion, and the Battle for America's Soul. New York, N.Y:
ECCO; 2007. ISBN 0-06-088548-3.
• Edis T; Young M. Why Intelligent Design Fails: A Scientific Critique of the New Creationism. New Brunswick,
N.J: Rutgers University Press; 2006. ISBN 0-8135-3872-6. Preview (http://books.google.ca/
books?id=hYLKdtlVeQgC&printsec=frontcover#v=onepage&q&f=false) at Google Books
• Why Darwin Matters: The Case Against Intelligent Design. New York: Henry Holt; 2007. ISBN
978-0-8050-8306-4.
• Slack G. The Battle over the Meaning of Everything: Evolution, Intelligent Design, and a School Board in Dover,
PA. San Francisco: Jossey-Bass; 2007. ISBN 0-7879-8786-7. Preview (http://books.google.ca/
books?id=1kpx8HrQ08cC&printsec=frontcover#v=onepage&q&f=false) at Google Books
ID perspectives
• Access Research Network (http://www.arn.org/)
• Design Inference: The website of William A. Dembski (http://www.designinference.com/)
Intelligent design 435

• Discovery Institute, Center for Science and Culture (http://www.discovery.org/) (Hub of the intelligent design
movement)
• EvolutionNews.org (http://www.evolutionnews.org/) Discovery Institute website tracking media coverage of
intelligent design.
• ID The Future (http://www.idthefuture.com/) A multiple contributor weblog by Discovery Institute fellows.
• International Society for Complexity, Information, and Design (ISCID) (http://www.iscid.org/)
• Uncommon Descent (http://www.uncommondescent.com/) William Dembski's blog
Non-ID perspectives
• Scientific American - 15 Answers to Creationist Questions (http://www.sciam.com/article.
cfm?id=15-answers-to-creationist)
• ACLU site on Intelligent Design (http://www.aclu.org/religion/intelligentdesign/index.html)
• Intelligent Design? (http://www.naturalhistorymag.com/darwinanddesign.html) http://web.archive.org/
web/20070620122151/http://www.naturalhistorymag.com/darwinanddesign.html special feature in the
Natural History Magazine
• Internet Encyclopedia of Philosophy: Design Arguments for the Existence of God (http://www.iep.utm.edu/d/
design.htm)
• National Center for Science Education What Is Intelligent Design Creationism? (http://ncse.com/creationism/
general/what-is-intelligent-design-creationism)
• Resolution from the American Association for the Advancement of Science (http://www.aaas.org/news/
releases/2002/1106id2.shtml)
• Science and Creationism: A View from the National Academy of Sciences (http://www.nap.edu/openbook.
php?isbn=0309064066) Second Edition (1999)
• Talk Origins Archive (http://www.talkorigins.org/) (Archive of the UseNet discussion group talk.origins)
• 139 page in-depth analysis of intelligent design, irreducible complexity, and the book Of Pandas and People
(http://www.pamd.uscourts.gov/kitzmiller/kitzmiller_342.pdf) by the Kitzmiller v. Dover Area School
District judge
• Kitzmiller: An Intelligent Ruling on 'Intelligent Design' (http://jurist.law.pitt.edu/forumy/2005/12/
kitzmiller-intelligent-ruling-on.php), JURIST
• ID and Creationism (http://www.csicop.org/intelligentdesignwatch/differences.html)
• The Design Argument (http://philosophy.wisc.edu/sober/design argument 11 2004.pdf) Elliott Sober, 2004.
• Short discussion on Natural Knowledge and Natural Design as a contrast to Intelligent Design (http://
richarddawkins.net/article,129,Natural-Knowledge-and-Natural-Design,Richard-Dawkins) http://web.archive.
org/web/20080307082606/http://richarddawkins.net/
article,129,Natural-Knowledge-and-Natural-Design,Richard-Dawkins by Richard Dawkins
Media articles
• Judgment Day: Intelligent Design on Trial (http://www.pbs.org/wgbh/nova/id/) A PBS-NOVA documentary
on the Dover, PA Intelligent Design trial in 2005.(PBS)
• Discovery's Creation (http://www.seattleweekly.com/2006-02-01/news/discovery-s-creation/) An overview
of the origin of the intelligent design movement. (Seattle Weekly)
• Intelligent Design vs. Evolution (http://www.tvw.org/MediaPlayer/Archived/WME.
cfm?EVNum=2006040103&TYPE=V) debate between paleontologist Peter Ward and Stephen Meyer
co-founder of the Discovery Institute
• Intelligent Design Deja Vu (http://www.washingtonpost.com/wp-dyn/content/article/2005/12/16/
AR2005121601559.html) What would "intelligent design" science classes look like? All we have to do is look
inside some 19th century textbooks. (The Washington Post)
Intelligent design 436

• How the media have covered ID (http://cjrarchives.org/issues/2005/5/mooney.asp) (Columbia Journalism

Review)
• Banned in biology class: intelligent design (http://www.csmonitor.com/2005/1221/p01s01-ussc.html)
(Christian Science Monitor)
• Devolution (http://www.newyorker.com/archive/2005/05/30/050530fa_fact) (The New Yorker)
• The Evolution Debate (http://www.nytimes.com/pages/science/sciencespecial2/) (The New York Times)
• Debating Evolution in the Classroom (http://www.npr.org/templates/story/story.php?storyId=5014428)
(NPR)
• Darwin Victorious (http://www.time.com/time/health/article/0,8599,1142672,00.html) (TIME)
• Intelligent Design: Scientific Inquiry or Religious Indoctrination? (http://web.archive.org/web/
20070928143835/http://www.justicetalking.org/viewprogram.asp?progID=506) (Justice Talking)
• Intelligent Judging—Evolution in the Classroom and the Courtroom (http://content.nejm.org/cgi/content/full/
354/21/2277) (New England Journal of Medicine)

Social effect of evolutionary theory

The social effects of evolutionary thought have been considerable. As the scientific explanation of life's diversity has
developed, it has often displaced alternative, sometimes very widely held, explanations. Because the theory of
evolution includes an explanation of humanity's origins, it has had a profound impact on human societies. Some have
vigorously opposed acceptance of the scientific explanation due to its perceived religious implications (e.g. its
implied rejection of the special creation of humans described in the Bible). This has led to a vigorous conflict
between creation and evolution in public education, primarily in the United States.

Evolution and ethics

The theory of evolution by natural selection has also been adopted as a foundation for various ethical and social
systems, such as social Darwinism, an idea that preceded the publication of The Origin of Species, popular in the
19th century, which holds that "the survival of the fittest" (a phrase coined in 1851 by Herbert Spencer, 6 years
before Darwin published his theory of evolution) explains and justifies differences in wealth and success among
societies and people. A similar interpretation was one created by Darwin's cousin, Francis Galton, known as
eugenics, which claimed that human civilization was subverting natural selection by allowing the "less fit" to survive
and "out-breed" the "more fit." Later advocates of this theory would suggest radical and often coercive social
measures to attempt to "correct" this imbalance. Thomas Huxley spent much time demonstrating through a series of
thought experiments that it would not only be immoral, but impossible,[1] Stephen Jay Gould and others have argued
that social Darwinism is based on misconceptions of evolutionary theory, and many ethicists regard it as a case of
the is-ought problem. After the atrocities of the Holocaust became linked with eugenics, it greatly fell out of favor
with public and scientific opinion, though it was never universally accepted by either, and at no point in Nazi
literature is Charles Darwin or the scientific theory of evolution mentioned. [2]
Darwin himself addressed eugenic concepts and denounced them as "evil" in his book, The Descent of Man.
Nor could we check our sympathy, even at the urging of hard reason, without deterioration in the noblest
part of our nature. The surgeon may harden himself whilst performing an operation, for he knows that he
is acting for the good of his patient; but if we were intentionally to neglect the weak and helpless; it
could only be for a contingent benefit, with an overwhelming present evil.
- Charles Darwin; The Descent of Man, 1871
Neo-creationist Polemics single out "Darwinism" as the cause of many, if not all, of modern society's ills. In the
controversial book From Darwin to Hitler by Richard Weikart [3], Weikart claims that Darwinism's impact on ethics
Social effect of evolutionary theory 437

and morality played a key role not only in the rise of eugenics, but also in euthanasia, infanticide, abortion, and racial
extermination, all ultimately embraced by the Nazis. Many critics contend this.
In his book The End of Faith, Sam Harris argues that Nazism was largely a continuation of Christian anti-Semitism.
Jim Walker has compiled a list of 129 quotes from Mein Kampf in which Hitler described himself as a Christian or
mentioned God or Jesus or a biblical passage.[4] Some argue that six million of the people killed during the
Holocaust were killed because of their religion (Judaism) not their race, "strength," or any reason with an obvious
link to the mechanism of Darwinian evolution. Hitler often used Christian beliefs like, "Jews killed Jesus," to justify
his anti-Semitism.[5] Of course, all indications are that Hilter was raised a catholic but rejected his beliefs and
certainly did not live them out.
Research for Weikart's book was funded by the Discovery Institute, which has been very active in promoting
intelligent design as an alternative to evolution in public school science classrooms, and whose "Wedge document"
and former mission statement expand on the theme: "The cultural consequences of this triumph of materialism were
devastating. Materialists denied the existence of objective standards binding on all cultures, claiming that
environment dictates our moral beliefs." ... "materialism spawned a virulent strain of utopianism. Thinking they
could engineer the perfect society through the application of scientific knowledge, materialist reformers advocated
coercive government programs that falsely promised to create heaven on earth." Archived [6] June 8, 1997 at the
Wayback Machine.
The notion that humans share ancestors with other animals has also affected how some people view the relationship
between humans and other species. Many proponents of animal rights hold that if animals and humans are of the
same nature, then rights cannot be distinct to humans.
Charles Darwin, in fact, considered "sympathy" to be one of the most important moral virtues — and that it was,
indeed, a product of natural selection and a trait beneficial to social animals (including humans). Darwin further
argued that the most "sympathetic" societies would consequently be the most "successful." He also stated that our
sympathy should be extended to "all sentient beings":
As man advances in civilization, and small tribes are united into larger communities, the simplest reason
would tell each individual that he ought to extend his social instincts and sympathies to all the members
of the same nation, though personally unknown to him. This point being once reached, there is only an
artificial barrier to prevent his sympathies extending to the men of all nations and races. If, indeed, such
men are separated from him by great differences in appearance or habits, experience unfortunately
shows us how long it is, before we look at them as our fellow-creatures. ... This virtue, one of the
noblest with which man is endowed, seems to arise incidentally from our sympathies becoming more
tender and more widely diffused, until they are extended to all sentient beings. As soon as this virtue is
honored and practiced by some few men, it spreads through instruction and example to the young, and
eventually becomes incorporated in public opinion.
- Charles Darwin; The Descent of Man, 1871

Thomas Huxley: Evolution and Ethics

Thomas Huxley, "Darwin's Bulldog", spent much of his book Evolution and Ethics debunking Social Darwinism,
piece by piece. The following is a summary of his arguments in the "Prolegomena", the most detailed and
comprehensive of the two sections devoted to it. It should be noted that Huxley is here attempting to disprove the
science behind Social Darwinism; as such, the moral arguments only come in later in the essay.
Consider a garden. Without constant upkeep, it would return to the "state of nature", even the very walls surrounding
it crumbling in sufficient time, but by constant diligence of the gardener, may be maintained in a "state of art". This
"state of art" is not permanent: It is instead the replacement of natural selection by artificial selection through the
human energy expended in maintaining it.
Social effect of evolutionary theory 438

This artificial selection is, however, part of natural selection: It is the action upon a set of species by the human
species by way of the human species expending energy through evolved intelligence on its choice of selection. It is
thus no less natural than, for example, a predator expending energy through evolved instinct on preferentially
hunting a certain prey species. The presence of humans may change the dynamic, but in a perfectly natural way.
Hence, it is part of the "cosmic process", that is natural laws, even though the "histological process" may remove
many aspects of the "struggle for existence" that is a key part of the natural laws that apply to biology, from its
preferred plant species by substituting human work for work done by the species itself.
Not only is the state of nature hostile to the state of art of the garden; but the principle of the
horticultural process, by which the latter is created and maintained, is antithetic to that of the cosmic
process. The characteristic feature of the latter is the intense and unceasing competition of the struggle
for existence. The characteristic of the former is the elimination of that struggle, by the removal of the
conditions which give rise to it. The tendency of the cosmic process is to bring about the adjustment of
the forms of plant life to the current conditions; the tendency of the horticultural process is the
adjustment of the conditions to the needs of the forms of plant life which the gardener desires to raise.
Nature uses unrestricted breeding to let hundreds compete for the natural resources that would only support one, and
uses frost and drought to kill off the weak and unlucky, requiring not just strength, but "flexibility and good fortune."
However, a gardener restricts multiplication, gives each plant sufficient space and nourishment, protects from frost
and drought—and, in every other way, attempts to modify the conditions to benefit the forms that most nearly
approach the result he desires. However, though the gardener's actions may have circumvented natural selection, he
can still improve the species, should he find them wanting, through selective breeding. The struggle for existence is
not actually required for improvement: only heritability, variation, and some form of selective pressure.
Can we then apply this to humans? Let's see how far we can take the analogy with respect to colonization:
Suppose a shipload of English colonists sent to form a settlement, in such a country as Tasmania was in the
middle of the last century. On landing, they find themselves in the midst of a state of nature, widely different
from that left behind them in everything but the most general physical conditions. The common plants, the
common birds and quadrupeds, are as totally distinct as the men from anything to be seen on the side of the
globe from which they come. The colonists proceed to put an end to this state of things over as large an area as
they desire to occupy. They clear away the native vegetation, extirpate or drive out the animal population, so
far as may be necessary, and take measures to defend themselves from the re-immigration of either. In their
place, they introduce English grain and fruit trees; English dogs, sheep, cattle, horses; and English men; in
fact, they set up a new Flora and Fauna and a new variety of mankind, within the old state of nature. Their
farms and pastures represent a garden on a great scale, and themselves the gardeners who have to keep it up, in
watchful antagonism to the old regime. Considered as a whole, the colony is a composite unit introduced into
the old state of nature; and, thenceforward, a competitor in the struggle for existence, to conquer or be
vanquished.
Under the conditions supposed, there is no doubt of the result, if the work of the colonists be carried out
energetically and with intelligent combination of all their forces. On the other hand, if they are slothful, stupid,
and careless; or if they waste their energies in contests with one another, the chances are that the old state of
nature will have the best of it. The native savage will destroy the immigrant civilized man; of the English
animals and plants some will be extirpated by their indigenous rivals, others will pass into the feral state and
themselves become components of the state of nature. In a few decades, all other traces of the settlement will
have vanished. However, as yet we lack an organized gardener. Let us imagine an idealized one: an
administrative authority of intelligence and foresight as much greater than men as men are to their livestock.
The unwanted native species - men, animals, or plants - are all weeded out and destroyed. Those to replace
them are chosen with a view to his ideal of the colony, just as a gardener tries to create through his selection
his ideal garden. And, finally, to ensure that no struggle for existence between the colonists interferes with the
Social effect of evolutionary theory 439

struggle against nature, he provides them with sufficient food, housing, and so on. "With every step of this
progress in civilization, the colonists would become more and more independent of the state of nature; more
and more, their lives would be conditioned by a state of art. In order to attain his ends, the administrator would
have to avail himself of the courage, industry, and co-operative intelligence of the settlers; and it is plain that
the interest of the community would be best served by increasing the proportion of persons who possess such
qualities, and diminishing that of persons devoid of them. In other words, by selection directed towards an
ideal." However, though this might create a paradise where every aspect of nature works to support its
colonists, problems arise: "as soon as the colonists began to multiply, the administrator would have to face the
tendency to the reintroduction of the cosmic struggle into his artificial fabric, in consequence of the
competition, not merely for the commodities, but for the means of existence. When the colony reached the
limit of possible expansion, the surplus population must be disposed of somehow; or the fierce struggle for
existence must recommence and destroy that peace, which is the fundamental condition of the maintenance of
the state of art against the state of nature. If the administrator is guided purely by scientific considerations, he
would work to restrict the population by removing "the hopelessly diseased, the infirm aged, the weak or
deformed in body or in mind, and the excess of infants born," just as a "gardener pulls up defective and
superfluous plants, or the breeder destroys undesirable cattle. Only the strong and the healthy, carefully
matched, with a view to the progeny best adapted to the purposes of the administrator, would be permitted to
perpetuate their kind." And so we have reached Social Darwinism. However, we do not have an idealized
administrator:
Of the more thoroughgoing of the multitudinous attempts to apply the principles of cosmic evolution, or
what are supposed to be such, to social and political problems, which have appeared of late years, a
considerable proportion appear to me to be based upon the notion that human society is competent to
furnish, from its own resources, an administrator of the kind I have imagined. The pigeons, in short, are
to be their own Sir John Sebright. A despotic government, whether individual or collective, is to be
endowed with the preternatural intelligence, and with what, I am afraid, many will consider the
preternatural ruthlessness, required for the purpose of carrying out the principle of improvement by
selection, with the somewhat drastic thoroughness upon which the success of the method depends.
Experience certainly does not justify us in limiting the ruthlessness of individual "saviors of society";
and, on the well-known grounds of the aphorism which denies both body and soul to corporations, it
seems probable (indeed the belief is not without support in history) that a collective despotism, a mob
got to believe in its own divine right by demagogic missionaries, would be capable of more thorough
work in this direction than any single tyrant, puffed up with the same illusion, has ever achieved. But
intelligence is another affair. The fact that "saviors of society" take to that trade is evidence enough that
they have none to spare. And such as they possess is generally sold to the capitalists of physical force on
whose resources they depend. However, I doubt whether even the keenest judge of character, if he had
before him a hundred boys and girls under fourteen, could pick out, with the least chance of success,
those who should be kept, as certain to be serviceable members of the polity, and those who should be
chloroformed, as equally sure to be stupid, idle, or vicious. The "points" of a good or of a bad citizen are
really far harder to discern than those of a puppy or a short-horn calf; many do not show themselves
before the practical difficulties of life stimulate manhood to full exertion. And by that time the mischief
is done. The evil stock, if it be one, has had time to multiply, and selection is nullified.
However, humans are not cattle, nor flowers: the organization of human society is kept together by ...bonds of
such a singular character, that the attempt to perfect society after his fashion would run serious risk of
loosening them. They do not even correspond to social insects such as bees: With bees, "The members of the
society are each organically predestined to the performance of one particular class of functions only. If they
were endowed with desires, each could desire to perform none but those offices for which its organization
specially fits it; and which, in view of the good of the whole, it is proper it should do. Among mankind, on the
Social effect of evolutionary theory 440

contrary, there is no such predestination to a sharply defined place in the social organism. However much men
may differ in the quality of their intellects, the intensity of their passions, and the delicacy of their sensations,
it cannot be said that one is fitted by his organization to be an agricultural laborer and nothing else, and
another to be a landowner and nothing else. Moreover, with all their enormous differences in natural
endowment, men agree in one thing, and that is their innate desire to enjoy the pleasures and to escape the
pains of life; and, in short, to do nothing but that which it pleases them to do, without the least reference to the
welfare of the society into which they are born", checked only by sympathy, familial and social bonds, and
fear of the judgment of ones fellow man. "Every forward step of social progress brings men into closer
relations with their fellows, and increases the importance of the pleasures and pains derived from sympathy. In
short, the creation of morality. Since morality is what keeps the desire for selfishness in check, it is necessary
to the propagation of society, with one requirement: the punishment of wrongdoers being necessary for the
continuation of society, self-restraint must not be taken so far that wrongdoers may act unrestrained: Without
the protection of society against them, "the followers of the "golden rule" may indulge in hopes of heaven, but
they must reckon with the certainty that other people will be masters of the earth."[7] Huxley sums up this
section of his argument against Social Darwinism:
I have further shown cause for the belief that direct selection, after the fashion of the horticulturist and
the breeder, neither has played, nor can play, any important part in the evolution of society; apart from
other reasons, because I do not see how such selection could be practiced without a serious weakening,
it may be the destruction, of the bonds which hold society together. It strikes me that men who are
accustomed to contemplate the active or passive extirpation of the weak, the unfortunate, and the
superfluous; who justify that conduct on the ground that it has the sanction of the cosmic process, and is
the only way of ensuring the progress of the race; who, if they are consistent, must rank medicine among
the black arts and count the physician a mischievous preserver of the unfit; on whose matrimonial
undertakings the principles of the stud have the chief influence; whose whole lives, therefore, are an
education in the noble art of suppressing natural affection and sympathy, are not likely to have any large
stock of these commodities left. But, without them, there is no conscience, nor any restraint on the
conduct of men, except the calculation of self-interest, the balancing of certain present gratifications
against doubtful future pains; and experience tells us how much that is worth. Every day, we see firm
believers in the hell of the theologians commit acts by which, as they believe when cool, they risk
eternal punishment; while they hold back from those which are opposed to the sympathies of their
associates.
Huxley finishes with a series of short, further evidences against Social Darwinism, including:
• Historical evidences against: Consider the vast changes of society between the Tudor and the Victorian eras;
however, human nature, as evidenced by their writing, remains the same. "In my belief, the innate qualities,
physical, intellectual, and moral, of our nation have remained substantially the same for the last four or five
centuries. If the struggle for existence has affected us to any serious extent (and I doubt it) it has been,
indirectly, through our military and industrial wars with other nations."
• Whether some qualities are virtues or vices depends on circumstance: "The benevolence and open-handed
generosity which adorn a rich man, may make a pauper of a poor one; the energy and courage to which the
successful soldier owes his rise, the cool and daring subtlety to which the great financier owes his fortune, may
very easily, under unfavorable conditions, lead their possessors to the gallows, or to the hulks. Moreover, it is
fairly probable that the children of a "failure" will receive from their other parent just that little modification of
character which makes all the difference. I sometimes wonder whether people, who talk so freely about
extirpating the unfit, ever dispassionately consider their own history. Surely, one must be very "fit," indeed,
not to know of an occasion, or perhaps two, in one's life, when it would have been only too easy to qualify for
a place among the "unfit.""
Social effect of evolutionary theory 441

Evolution and Ethics [8] at Project Gutenberg

Evolution and religion

See also: History of evolutionary thought
Before Darwin's argument and presentation of the evidence for evolution, Western religions generally discounted or
condemned any claims that diversity of life is the result of an evolutionary process, as did most scientists in the
English scientific establishment. However, evolution was accepted by some religious groups such as the Unitarian
church and the liberal Anglican theologians who went on to publish Essays and Reviews. as well as by many
scientists in France and Scotland and some in England, notably Robert Edmund Grant. Literal or authoritative
interpretations of Scripture hold that a supreme being directly created humans and other animals as separate "Created
kinds", which to some means species. This view is commonly referred to as creationism. From the 1920s to the
present in the US, there has been a strong religious backlash to the teaching of evolution theory, particularly by
conservative evangelicals. They have expressed concerns about the effects of the teaching of evolution on society
and their faith (see Creation-evolution controversy).
In response to the wide scientific acceptance of the theory of evolution, many religions have formally or informally
synthesized the scientific and religious viewpoints. Several important 20th century scientists (Fisher, Dobzhansky)
whose work confirmed Darwin's theory, were also Christians who saw no incompatibility between their experimental
and theoretical confirmations of evolution and their faith. Some religions have adopted a theistic evolution
viewpoint, where God provides a divine spark that ignited the process of evolution and (or), where God has guided
evolution in one way or another.

Evolution and the Roman Catholic Church

The Roman Catholic Church, beginning in 1950 with Pope Pius XII's encyclical Humani Generis, took up a neutral
position with regard to evolution. "The Church does not forbid that...research and discussions, on the part of men
experienced in both fields, take place with regard to the doctrine of evolution, in as far as it inquires into the origin of
the human body as coming from pre-existent and living matter." [9]
In an October 22, 1996, address to the Pontifical Academy of Science, Pope John Paul II updated the Church's
position, recognizing that Evolution is "more than a hypothesis" - "In his encyclical Humani Generis, my
predecessor Pius XII has already affirmed that there is no conflict between evolution and the doctrine of the faith
regarding man and his vocation... Today, more than a half-century after the appearance of that encyclical, some new
findings lead us toward the recognition of evolution as more than an hypothesis. In fact it is remarkable that this
theory has had progressively greater influence on the spirit of researchers, following a series of discoveries in
different scholarly disciplines." [10]

Evolutionary theory and the political left

The majority of those on the left do not oppose Darwinism per se, but are critical of interpretations of evolutionary
theory that, in their view, overemphasize the role of competition and ignore elements of co-operation in nature such
as symbiosis.
Many important political figures on the left have never publicized their views on biology, and so their opinions of
evolutionary theory are unknown. To some extent, Marxists are the exception. Karl Marx, Friedrich Engels and
Vladimir Lenin supported Darwin's evolutionary theory. Marx even sent Darwin a copy of his book Das Kapital,
though Darwin never wrote back to him. Karl Marx's work was based on a material view of the world that showed
natural causes and effects for all aspects of human society and economy. He recognized that Darwin's work provided
a similar material explanation for all of nature, thus supporting Marx's worldview.
Social effect of evolutionary theory 442

In 1861 Karl Marx wrote to his friend Ferdinand Lassalle, "Darwin’s work is most important and suits my purpose in
that it provides a basis in natural science for the historical class struggle. ... Despite all shortcomings, it is here that,
for the first time, 'teleology' in natural science is not only dealt a mortal blow but its rational meaning is empirically
explained."
Most later Marxists agreed with this view, but some - particularly those in the early Soviet Union - believed that
evolutionary theory conflicted with their economic and social ideals. As a result, they came to support Lamarckism
instead - the idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring. This
led to the practice of Lysenkoism, which caused agricultural problems.
In his book, Mutual Aid: A Factor of Evolution, anarcho-communist Peter Kropotkin argued that co-operation and
mutual aid are as important in the evolution of the species as competition and mutual strife, if not more so.
On the contemporary moderate left, some authors such as Peter Singer (in his book, A Darwinian Left) support
Darwinism but reach different political and economic lessons than more conservative observers. Richard Dawkins'
book, The Selfish Gene, has a chapter, "Nice guys finish first", which attempts to explain the role of altruism and
cooperation in evolution and how social animals not only cannot survive without such traits, but how evolution will
create them. Dawkins explains that when an animal sacrifices itself or uses its resources for the survival of other
members of the same species, its genes, present on the other animals, survive. For example, if a mother dies to save
three of its pups, one and a half copies (on average) of its genes will survive, because there is a 50% chance of a
particular gene being present in its offspring. Dawkins also made a documentary of the same name.[11] According to
the documentary, Dawkins added that chapter as a way of overcoming modern day misinterpretations of the concept
of "survival of the fittest".

Evolution in relation to Social Darwinism and Imperialism

Evolution has often been linked to Social Darwinism, which is further linked with nationalism and imperialism.[12]
During the age of New Imperialism, the concepts of evolution justifed the exploitation of "lesser breeds without the
law" by "superior races."[12] To elitists, strong nations were composed of white people who successful at expanding
their empires, and as such, these strong nations would survive in the struggle for dominance.[12] With this attitude,
Europeans, except for Christian missionaries, seldom adopted the customs and lanugages of local people under their
empires.[12] Christian missionaries, on the other hand, were the very first individuals to meet new peoples and
develop writing systems for local inhabitants' languages that lacked one.[12] Being critics of Darwinism, ardently
opposed slavery and provided an education and religious instruction to the new peoples they interacted with since
they felt that this was their duty as Christians.[12]

See also
• Social evolutionism
• Neo-Creationism
• Garden of Eden
• Hypergamy
• Natural philosophy
• Freethought
• Age of the Earth
Social effect of evolutionary theory 443

References
[1] Eugenics, etc (http:/ / www. gutenberg. org/ etext/ 2940)
[2] The fallacious nature of [[reductio ad Hitlerum (http:/ / www. rationalrevolution. net/ articles/ darwin_nazism. htm)] arguments by
anti-evolutionists.]
[3] http:/ / www. darwintohitler. com/
[4] Webpage containing 129 Mein Kampf quotes relating to his Christianity (http:/ / www. nobeliefs. com/ hitler. htm)
[5] Religion and Hitler - a history (http:/ / www. nobeliefs. com/ hitlerchristian. htm)
[6] http:/ / web. archive. org/ web/ 19970608130849/ http:/ / www. discovery. org/ crsc/ aboutcrsc. html
[7] Huxley credits Hartley (Observations on Man (1749), vol. ii p. 281.) for not only having "laid the foundations but built up much of the
superstructure of a true theory of the Evolution of the intellectual and moral faculties and for having realized that the creation of civilization
will in itself create ethics, if not in an evolutionary context." as well as Adam Smith
[8] http:/ / www. gutenberg. org/ etext/ 2940
[9] http:/ / www. vatican. va/ holy_father/ pius_xii/ encyclicals/ documents/ hf_p-xii_enc_12081950_humani-generis_en. html
[10] http:/ / www. ewtn. com/ library/ PAPALDOC/ JP961022. HTM
[11] Nice guys finish first (http:/ / www. youtube. com/ watch?v=FzeCn02l_Rw)
[12] "Western Civilization: Ideas, Politics, and Society" (http:/ / books. google. com/ books?id=kKGgoNo4un0C& pg=PA653& lpg=PA653&
dq=social+ darwinism+ missionaries+ india& source=bl& ots=Y_LLqh3b93& sig=zQsURzU455ZsXRa-SOQJIzIzP8w& hl=en&
ei=7TuhTLfJM8aNnQfF5bSiAw& sa=X& oi=book_result& ct=result& resnum=4& ved=0CCYQ6AEwAw#v=onepage& q=social darwinism
missionaries india& f=false). Houghton Mifflin Harcourt Publishing Company. . Retrieved 2007–03–25. "The most extreme ideological
expression of nationalism and imperialism was Social Darwinism. In the popular mind, the concepts of evolution justifed the exploitation of
"lesser breeds without the law" by superior races. This language of raece and conflict, of superior and inferior people, had wide currency in the
Western states. Social Darwinists vigourously advocated the acquistion of empires, saying that strong nations-by definition, those that were
successful at expanding industry and empire-would survive and that others would not. To these elitists, all white men were more fit than
nonwhites to prevail in the struggle for dominance. Even among Europeans, some nations were deemed more fit than others for the
competition. Usually, Social Darwinists thought their own nation the best, an attitude that sparked their competitive enthusiasm. In the
nineteenth centruy, in contrast to the seventeenth and eighteenth centuries, Europeans, except for missionaries, rarely adopted the customs or
learned the languages of local people. They had little sense that other cultures and other people had merit or deserved respect. Many
westerners believed that it was their duty as Christians to set an example and to educate others. Missionaries were the first to meet and learn
about many peoples and were the first to develop writing for those without a written language. Christian missionaries were ardently opposed
to slavery."
Article Sources and Contributors 444

Article Sources and Contributors

Introduction to evolution  Source: http://en.wikipedia.org/w/index.php?oldid=392593427  Contributors: 100110100, 16@r, ABoerma, AdultSwim, Agg56tt, Alan Liefting, Ali, AlphaEta,
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Howaboutthat, Hrafn, IP69.226.103.13, IVAN3MAN, IanCheesman, Instinct, Iwanttofitin, J.delanoy, JESUS LOVS YOU, JForget, Jacob1207, Jania902, JayHenry, JeremyA, Jgardner7777,
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Rambam rashi, Random Replicator, Randomblue, Raphite, RatKingSmurf, Ratphobia, Rich Farmbrough, Richard001, Rjwilmsi, Rosesflowers8, Rror, RucasHost, Ryantremblay, SU Linguist,
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Thethornofarose, Thingg, Thompsma, Tikiwont, TimVickers, Titanium Dragon, Tktktk, Tomandlu, Tstrobaugh, Tuxedo junction, Twooars, UncleBubba, Unhinged1122, VVtam, Vanished User
0001, Vanished user, Vsmith, WAS 4.250, Wassupwestcoast, Wat-up-guys, Wegotthe, Will Beback, Wizardboy777, Wknight94, Woohookitty, Woudloper, Writtenright, Z10x, Zapvet, ‫یناریا‬,
248 anonymous edits

Evolution  Source: http://en.wikipedia.org/w/index.php?oldid=393126466  Contributors: !!!niloivenutfotuO, .:Ajvol:., 0nlyth3truth, 10.175, 100110100, 119, 12 Cove, 123heyho,
162.129.26.xxx, 168..., 1nic, 210.50.54.xxx, 216.126.89.xxx, 2357, 24.108.14.xxx, 3 Lane, 4 Gnon, 4 trin, 40 tune, 489thCorsica, 6 Four, 6 y go, 65.68.87.xxx, 7 Fej, 8r13n, 9 noon,
99DBSIMLR, A Softer Answer, A bit iffy, A455bcd9, A8UDI, AC+79 3888, AH9, ASDFGHJKL, AVengel, Aaarrrggh, Aarnu, Aaron Schulz, AaronFX, Aartp, Abce2, Abdullais4u, Abi Don,
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JHunterJ, JNeal, JWSchmidt, JYolkowski, Jaberwocky6669, Jacek Kendysz, Jack Walsh, JackH, Jackrm, Jagged 85, Jak Tac, Jaknouse, James.Spudeman, Jamesofur, Jamyskis, Jan van Male,
Jason Potter, Javascap, Jclerman, Jdfoote, Jdhunt, Jecar, JedRothwell, Jedi Davideus, Jedi of redwall, Jedwina, JeffStickney, Jefffire, Jeffrey O. Gustafson, Jenequa, JeremyA, Jeremypyle, Jesus Is
Love, Jesus Loves You, Jhouser24, JiFish, Jiejunkong, Jim62sch, JimWae, Jimaltieri, Jimbobsween, Jimfbleak, JimmyButler, JinJian, Jitterro, Jiy, Jjb123, Jketola, Jlefler, Jlrobertson, Jmeppley,
Jnothman, Joannamasel, JoanneB, Joe.aston, Joe11, Joe1978, Joel.Gilmore, Joelr31, Joelsmades6, JoergenB, John, John Callender, John D. Croft, John Fader, John Stumbles, John Wilkins,
John254, JohnOwens, Johnleemk, JohnnyCalifornia, Johnstone, Johnuniq, Jok2000, Joka1991, Joke137, Jokerst44, Jordan117, Jos Jio, JosephPayseur, Josh Grosse, Joshjoshjosh1, JoshuaZ,
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Jvbishop, K, K. Aainsqatsi, KC Panchal, KMFDM Fan, Kaal, Kablammo, Kaboomywhackwhack, Kaisershatner, Kajisol, Kandar, Kanfood, Kangaru99, Karatenerd, Karmosin, Katalaveno, Kate,
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Bruning, KimvdLinde, KingTT, Kinst, Kirbytime, Kljenni, Kmweber, Knight of BAAWA, KnightLago, Kniknight, Knowledge Seeker, KnowledgeOfSelf, Knuv moor, Koavf, Kondspi,
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Magician that makes things white, Magicman710, Magister Mathematicae, Mal hen, Malcolm rowe, Malik Shabazz, Malo, Malvaro, ManaUser, Mann jess, Manph, Manuel Trujillo Berges,
Article Sources and Contributors 445

Maork, Maqsarian, MarSch, Marc210, MarcIam, MarcoTolo, Marcperkel, Margareta, MarineHebert, Mark Renier, Marr Plv, MarsRover, Marshman, Marskell, MartinHarper, MartinSpamer,
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Zappernapper, Zarniwoot, Zarru, Zashaw, Zbvhs, Zero g, Zeromegamanx, ZimZalaBim, Zoe, Zsinj, Zundark, Zx-man, Zyasu, Zyyx, Zzuuzz, 2608 anonymous edits

Evolution as theory and fact  Source: http://en.wikipedia.org/w/index.php?oldid=392830825  Contributors: A little insignificant, AdjustShift, Aitias, Aks818guy, AkselGerner, Aksi great, Alan
Liefting, Alansohn, AlphaEta, Anarchangel, Anas Emad, Andrew c, Andrewlp1991, Another Stickler, Antiuser, Aprock, ArielGold, Armchair info guy, Astatine-210, Ate98, Atl braves, Aunt
Entropy, Auraclan, Axel147, Barryruth, Bkell, Blanchardb, Blind designer, Blue Dinosaur Jr, Bluerasberry, Boeingbenn, Brougham96, Butwhatdoiknow, C.Fred, Cabe6403, Calvin 1998, Causa
sui, Charlesdrakew, Ched Davis, Chick Bowen, Chowbok, CooPs89, Courcelles, Craigmac41, Cremepuff222, Critter2482, Cst17, D, Dan Gluck, Dan8080, Daniel J. Leivick, DarkLink, Darth
Panda, Dave souza, Dawn Bard, Dbachmann, Dcljr, Deconstructhis, Diamondslide, Discospinster, Dock312, Dougweller, Eaglegordon, Earthmichael, Ed Poor, Eheneden, Elassint,
ElationAviation, Elfred, ElijahOmega, Endgame69, Ensign beedrill, Escape Orbit, Evrimfeyyaz, Excirial, Ezra Wax, Farsight001, Felix Folio Secundus, FeloniousMonk, Filll, FullMetal Patch,
Gabbe, Gail, GeneCallahan, Giovanni33, Gjmulder, Glane23, Glass Sword, Gnevin, Gniniv, GodMadeTheUniverse, Graham87, GregorB, Guettarda, Hans Adler, Headbomb, Hello32020, Hpa,
Hqb, Hrafn, Hut 8.5, II MusLiM HyBRiD II, IRP, IanCheesman, Icairns, Inniverse, Iridescent, IslaySolomon, Itisnotme, JRtheDude, JSF16, JSpung, Jaketola, Jazzed, Jchthys, Jeff G.,
Jesusforever, Johnuniq, Jomasecu, JoshuaZ, Julesd, Just plain Bill, Kal Sir, Keilana, Kerotan, KillerChihuahua, KimvdLinde, Kittiekatsu, Knucmo2, Lars Washington, Linkthewindow, Lord of
the Pit, Lradrama, Mann jess, MarcoTolo, Martin Hogbin, Mattinbgn, Matěj Grabovský, Methcub, Michael Johnson, Mikker, Mildly Mad, Mindmatrix, Monterey Bay, Montgomery '39,
NawlinWiki, Nefariousski, NellieBly, NeuroBells123, Nickptar, Nightscream, Nihiltres, Noctibus, Noleander, NorCal764, NuclearWarfare, Nukeh, Orangemarlin, Pbarnes, Peter coxhead, Peyre,
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Yasmine shenn, Yowuza, Zaharous, ZeWrestler, Zebspace, 362 anonymous edits

Evolutionary history of life  Source: http://en.wikipedia.org/w/index.php?oldid=391449486  Contributors: 10outof10die, 5 albert square, Ac02111993, Ajstov, Alan Liefting, AlphaEta, Arbeo,
Arthur Rubin, Artichoker, Artoannila, Aunt Entropy, Azcolvin429, BK4ME, Bdoom, Beardnomore, BellaKazza, BenFrantzDale, Benclewett, Chrisjj, Ciphergoth, Coffee2theorems,
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J.delanoy, J04n, Jag149, Janus01, Jarry1250, Jeff G., Jennavecia, Johannordholm, John, JohnCD, Johnuniq, Joshuajohnlee, Just plain Bill, Kevmin, Kingdon, Kku, KnowledgeOfSelf, Kozuch,
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Winterspan, Woohookitty, Woudloper, Yamakiri, Zappernapper, Zazaban, 81 anonymous edits
Article Sources and Contributors 446

Timeline of evolution  Source: http://en.wikipedia.org/w/index.php?oldid=392950288  Contributors: 1 use, A8UDI, AS, Abdul Muhib, Abosaleh911, Addshore, Aidan Elliott-McCrea, Akamad,
Akasbrian, Alan Liefting, Alansohn, Aldaron, Ancheta Wis, Andkore, Andrea105, Angela, Ankit jn, Anlace, Antandrus, ArcaneMachine, Arkuat, Armchair info guy, ArthurWeasley, Athaler,
Atlant, Auriam, Autodidactyl, AxelBoldt, Ballista, BenSittler, Bergsten, BigBurkey, Blades95, Blehfu, Bobby D. Bryant, Bobo192, Bogdangiusca, Bolivian Unicyclist, Bongoo, Boreas74, Brion
VIBBER, Brogers0436, Brunnock, Bryan Derksen, Burner0718, CJLL Wright, CSVR4, CSWarren, Cam, CanisRufus, CapitalR, CeoMaiy, CeoMaj, Cephal-odd, Cgingold, Chris.urs-o,
Ciphergoth, Cmdrjameson, Coffee2theorems, CommonsDelinker, Conversion script, Courcelles, Coyoty, CreaoTnismKickR, Crum375, Cyan, Cyde, DanielCD, Dave souza, Dawn Bard,
Dbabbitt, Dbachmann, Dcljr, Dendodge, DerHexer, Dethme0w, Diadem, Dichro, DirkvdM, Discospinster, Diza, Dodo bird, Dolphonia, Dr.Bastedo, Dragons flight, Dreish, Duncharris, Dweir,
Dysepsion, Dysmorodrepanis, Ebyabe, Ec5618, Edward, Ejosse1, Eleassar777, Elfguy, Emil Teofanov, Emmanuelm, Enviroboy, Eric Forste, Eric Kvaalen, Evolauxia, FT2,
Faithlessthewonderboy, Fang 23, Freakofnurture, Fred Bradstadt, Fred Hsu, Friginator, Frunobulax, Funhistory, Fuzheado, GSlicer, Gabbe, Gadfium, Gaius Cornelius, GameKeeper, Garion96,
Gary Cziko, Gdr, Gene Nygaard, George Hernandez, Gilliam, Goalie1002002, GoingBatty, Grim23, HGB, Hadal, Hairhorn, Headbomb, Heliogabalus1, Henrygb, Hephaestos,
Hereforhomework2, Heron, Hibernian, Horned1, Hugin&Munin, IanCheesman, Icairns, Imc, Immunize, IronGargoyle, JForget, JH-man, JakeVortex, Jaknouse, Jamesdowallen, Jatkins, Jayc,
Jcmo, JeffW, Jmc112693, JoeshB, John, John Abbe, John D. Croft, John Vandenberg, John37309, JohnCD, Johnuniq, Jon186, JorisvS, Jrockley, KWMec, Kaimiddleton, Kapow, Katalaveno,
Katharina Simon, Katieh5584, Kekm23, Keraunos, Kimiko, KimvdLinde, KirbyManiac, Knowledge Seeker, KnowledgeOfSelf, KnowledgeRequire, Koavf, Koebie, Kompar, Krclathrate, Kuru,
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Markjoseph125, Marknesbitt, Marshman, Marskell, Martin-vogel, Mateuszica, Matterfoot, Matthew Yeager, Maurreen, Maximus Rex, Meggar, Mencial, Merovingian, Michael Johnson,
Mikenorton, Mindmatrix, Momabdishu, Moondyne, Morning277, Mr Chuckles, Mrfunnyd, Mrh30, Mtg400, Nakon, NameIsRon, Narayanese, Natalie Erin, NatureA16, Ncmvocalist, Nedlum,
Neutrality, Neverquick, Nivix, Null Nihils, Oblivious, Odycee, Ollie senter, Onco p53, One-dimensional Tangent, OpenToppedBus, Orangemarlin, Pamdhiga, Parsa, Paul from Michigan,
Pennywisdom2099, Peruvianllama, Peter b, Petri Krohn, Pgk, Philip Stevens, Philip Trueman, Philippe, Philmcgrove, Plumbago, Pollinator, Quiddity, RJHall, RK, RainbowOfLight,
Raymondwinn, Rdsmith4, RedWolf, Rednblu, Rich Farmbrough, Rick Norwood, Rling, Robert Stevens, Roentgenium111, Ronhjones, Rossami, RoundSparrow, Royboycrashfan, Rune.welsh,
SMC, SMesser, Sabik, Saikiri, Salleman, Samak47, Samiam1955, SchfiftyThree, Shadowjams, SheffieldSteel, Shrimp wong, Silence, Simnicol, Sin-man, Slarre, Sleeppointer, Smallweed,
Smith609, Sonett72, Soulkeeper, Stefan, Stephan Schulz, Streona, StuffOfInterest, Sverdrup, Svetovid, Tannin, Teapotgeorge, The Thing That Should Not Be, Theultimatum, Tide rolls, Timwi,
Tomruen, Tonyfaull, Transisto, Tuganax, Tulostoma, TutterMouse, Twanderson, Tycho, Uncle Milty, Urhixidur, UtherSRG, VBGFscJUn3, Valich, Vcrs, Veda784, Vera Cruz, Voyagerfan5761,
Vsmith, Waggers, William Avery, William M. Connolley, Williamb, Wilson44691, Workster, Xagent86, Yamamoto Ichiro, Zoe, Zundark, 838 anonymous edits

History of evolutionary thought  Source: http://en.wikipedia.org/w/index.php?oldid=391895866  Contributors: AS, Aderksen, Adrian 1111, Afernand74, Alansohn, Alba, Albie34423, Allen3,
Allventon, AlphaEta, Andycjp, Anlace, AnonMoos, Arch dude, Armchair info guy, Art LaPella, Artichoker, Astatine-210, Athenean, Aunt Entropy, BD2412, Barnaby dawson, Barticus88,
BenB4, Bender235, Bendzh, Brighterorange, CCooke, Charles Matthews, CharlesGillingham, Circeus, Cmdrjameson, CommonsDelinker, Cygnis insignis, D-Notice, Dabomb87, Dave souza,
Descendall, Diedo1982, Dojarca, Doubting thomas, DrKiernan, Drumbeatsofeden, Duncharris, Eaglizard, Ealdgyth, Eastlaw, EchetusXe, Edital, Egmontaz, Emw, Enrique Cordero, Epbr123,
Ettrig, Evertype, Extremophile, Fang 23, Faro0485, Fastfission, Filll, Flexijane, Francis Hoar, Fred Bradstadt, Fvasconcellos, G716, GN, GRBerry, GSlicer, Galoubet, Gdr, Gil Gamesh,
Gimmetrow, GoonerDP, Gregbard, Grimhelm, Guest9999, H.sanat, Halaqah, HarryHenryGebel, Harryboyles, Headbomb, Heron, Hmains, Igiffin, Isolation booth, J. Spencer, J.delanoy, Jagged
85, Jeargle, Joe hill, Joel7687, Johnor, Johnuniq, Josh Grosse, JoshuaZ, Jrmccall, Juliancolton, Kaldari, Knight1993, Koavf, Kosmocentric, Kozuch, Lacatosias, Lauranrg, Leandrod,
Leonardorejorge, Leptictidium, Lexor, Lilac Soul, Ling.Nut, LittleHow, Logicus, LonelyMarble, LovesMacs, Macdonald-ross, Malick78, Marcus MacGregor, Martial75, Mattisse, MaxSem,
MayerG, Michael Devore, Nihiltres, NuclearWarfare, Oldag07, Opabinia regalis, Orangemarlin, PDH, Pbarnes, PhDP, Piledhigheranddeeper, Pince Nez, Pingveno, Piotrus, Plumbago, Portillo,
Qertis, RJHall, Ragesoss, Random account 47, Redtigerxyz, RevRagnarok, Rich Farmbrough, Richard001, Rjwilmsi, Rlinfinity, Robert1947, RobertG, Ruffmonster, Rusty Cashman, Ryan.vilbig,
Rysz, Safay, Samsara, SandyGeorgia, Scythia, Seegoon, Shyamal, Sillygrin, Sjdunn9, Skirby17, Spammer34567, Spotty11222, SpuriousQ, Srnec, StN, Stappsclass, Steinsky, StudyAndBeWise,
Syncategoremata, Syzygos, Szquirrel, THEN WHO WAS PHONE?, Taffboyz, TeleComNasSprVen, Tevildo, Thatguyflint, TimVickers, Tiptoety, Tmol42, Trialsanderrors, Tuxedo junction, User
A1, Vanished user, Vero.Verite, Vmaldia, Vsmith, WAS 4.250, Wavelength, Wayland, WolfmanSF, Wordwright, Writtenright, Xuehxolotl, Z10x, Zappernapper, Zef, 124 anonymous edits

Lamarckism  Source: http://en.wikipedia.org/w/index.php?oldid=392998003  Contributors: ***Ria777, A little insignificant, Achmed123456789, Aitias, Alansohn, Aliekens, Aljullu, Ams80,
Anadverb, Androstachys, Anna Lincoln, Ano-User, Anonywiki, Ashmoo, Astor, AxelBoldt, Barticus88, Bender235, Berton, Binadot, Black Kite, Bomac, Cesare Barbone, Chocolateboy, Chris
the speller, Chris55, Cinik, Colonies Chris, Coricus, Csernica, Cyberix, DARTH SIDIOUS 2, Damneinstien, Daniel Brockman, Dave souza, Discospinster, Dissembly, Dreaded Walrus,
Dumarest, Duncharris, Dyed Purple, Ethan Mitchell, Extremophile, Fastfission, Fences and windows, Fred Hsu, GCarty, Gilliam, Gogo Dodo, Gomm, GrahamP, Gregbard, Gwern, HaeB,
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Twang, User99, Vremya, WAS 4.250, WLU, Wiki Raja, Wimt, Xabian40409, Yuh66h, Zamphuor, Zoicon5, 213 anonymous edits

Saltationism  Source: http://en.wikipedia.org/w/index.php?oldid=382880304  Contributors: Adzyaye, Bcasterline, Digitata, Dysmorodrepanis, Everyking, Extremophile, Garygromet, Graham87,
Greeneto, Hadrian89, Havermayer, HumbleGod, Johnuniq, Lauranrg, Leonardorejorge, Leptictidium, Mchavez, Merzul, Mgerb, Mitteldorf, Mmcannis, Rusty Cashman, Tbjablin, Trilobitealive,
Unimaginative Username, Woohookitty, 15 anonymous edits

Orthogenesis  Source: http://en.wikipedia.org/w/index.php?oldid=385164271  Contributors: 3tcetera, Alba, Ano-User, Armchair info guy, Bcasterline, Bensaccount, Brichard37, Ceramufary,
Dgri, Entropix, Eras-mus, Ewlyahoocom, Extremophile, FanCollector, Filll, Fred Hsu, GoEThe, Headbomb, Infophile, J0m1eisler, Jacob1207, Johnuniq, Lauranrg, Lexor, MSchnitzler2000,
Manning Bartlett, Meco, Memestream, Michael Hardy, Nosson77, Nwbeeson, Opie, Rich Farmbrough, Rusty Cashman, Sam Hocevar, Sietse Snel, Smaines, StN, Steinsky, Stephen Morley,
Superborsuk, TeleComNasSprVen, Vanished User 0001, Vclaw, Viriditas, Zafiroblue05, 22 anonymous edits

On the Origin of Species  Source: http://en.wikipedia.org/w/index.php?oldid=392624508  Contributors: 1or2, 213.253.39.xxx, A.Kurtz, AC+79 3888, Aa77zz, Abecedare, Acc3ss, Adam Zivner,
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Xaliqen, Xiner, Xmahahdu, Yerpo, Yvori, Zachlipton, Александър, 609 anonymous edits

Darwinism  Source: http://en.wikipedia.org/w/index.php?oldid=391503292  Contributors: 16@r, A Raider Like Indiana, Abbenm, Akamad, Aksi great, Alansohn, Alexei Kouprianov,
Alexrio1013, Alienus, Allinthebrain, AlphaEta, Andres, Andrewlp1991, Antandrus, Ante Aikio, Anton Kos, Antrophica, Anwegmann, Arbeiter, Arde Madrid, Aristotle2600, Armchair info guy,
Article Sources and Contributors 447

Audacity, Aunt Entropy, AxiomOfFaith, BG, Backmask, Bebo liebe, BenAveling, Bless sins, Bloodofox, Blotchhead, Blove maple, Bobo192, Bonerface, Bongwarrior, Boris Živ, Bowlhover,
Brian0918, Brianrein, Briggsalex, Bryan Derksen, Builder w, Calebrw, CapitalR, Capricorn42, Carbuncle, CardinalDan, Carrionluggage, Cenarium, Chad625, Chase me ladies, I'm the Cavalry,
Chowbok, Chris5858, ChrisDuben, Coelacan, ConfuciusOrnis, Conversion script, Cornellrockey, Cornopeanus, Cuaxdon, Cureden, Cyde, CzarB, DLH, Daecon, DannyMuse, Daughter of Mímir,
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Vsmith, WLU, Wayne Olajuwon, Wetman, Wiki alf, WikiLaurent, Xaosflux, Yamamoto Ichiro, Yankeefan292, Yerpo, Zeamays, 437 anonymous edits

The Genetical Theory of Natural Selection  Source: http://en.wikipedia.org/w/index.php?oldid=347178552  Contributors: Adoniscik, Ambystoma, Angr, Betacommand, Bobo192, Brockert,
Duncharris, Gloriamarie, Headbomb, I am not a dog, Jefffire, Jengod, Jhbadger, Lexor, Mark Richards, Maximus Rex, Minhtung91, RadicalBender, Richard001, TedE, The wub, Timwi, 18
anonymous edits

Neo-Darwinism  Source: http://en.wikipedia.org/w/index.php?oldid=366488537  Contributors: Alan Liefting, Andrew c, Armchair info guy, Aunt Entropy, Barak Sh, Benhocking, Bueller 007,
ConfuciusOrnis, Dave souza, Duncharris, Ed Poor, Gnomon Kelemen, Headbomb, Hrafn, John Vandenberg, JoshuaZ, Jweiss11, K, Karan.m.khot, Lexor, Lindosland, Livingrm, MartinSpamer,
Mastad, Memestream, Odd nature, Oldekop, Orangemarlin, Rusty Cashman, Samspeedy1985, Senortypant, SimonD, Snalwibma, Tannin, TimVickers, Tuxedo junction, Vanished user, Vasiľ,
Woohookitty, 22 anonymous edits

Modern evolutionary synthesis  Source: http://en.wikipedia.org/w/index.php?oldid=392613323  Contributors: 168..., 2D, Aecis, Akendall, AlphaEta, Andre Engels, Andres, Ano-User,
Anthony, Arminius, Artichoker, Azcolvin429, Bcasterline, Belovedfreak, Benjaminmyklebust, Bhawthorne, Brighterorange, Canada Jack, ConfuciusOrnis, Dave souza, David Shear, Dawn Bard,
Dbachmann, Deb, Delirium, Dhochron, Djlayton4, DonSiano, DrThompson, Duncharris, Edgar181, El C, Erik Corry, Extremophile, Fabricebaro, FaerieInGrey, Fastfission, Filll, Fiskeharrison,
Fracker, Fratrep, Fred.e, GSlicer, Gabbe, Gaius Cornelius, Glenmin, Gloriamarie, Gnomon Kelemen, Gog, Gregbard, Ground Zero, Headbomb, Hibernian, Horselover Frost, Hrafn, I am not a
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initialisation script, TestPilot, The Merciful, The morgawr, Tiddly Tom, TimVickers, Tstrobaugh, Tuxedo junction, Twirligig, Ucucha, Vanished User 0001, VoteFair, Vsmith, WAS 4.250,
Wafulz, Waldow, Warofdreams, Woudloper, Writtenonsand, Z10x, 122 anonymous edits

Heredity  Source: http://en.wikipedia.org/w/index.php?oldid=393073936  Contributors: 2D, 5 albert square, Acather96, Acroterion, Afaz, Agathman, Akerans, Alansohn, Alec - U.K.,
Alex.muller, Alexpavlov12345, Alfalfa9, Amwyll Rwden, AnakngAraw, Andersrask1977, Andonic, Andrewpmk, Andy Marchbanks, Antandrus, Apeloverage, Arkarind, Azcolvin429, Beboots,
BirgitteSB, Bob f it, Bobianite, Bobo192, Bongwarrior, Borgx, Brian0918, Burntsauce, Calabraxthis, Camw, Can't sleep, clown will eat me, CaptainAmerica, Casull, ChXu, Charles Matthews,
Connormah, Conversion script, Courcelles, D, DARTH SIDIOUS 2, DGtal, Dan Polansky, Dave souza, DavidWBrooks, DeadEyeArrow, Debresser, Decltype, Deli nk, DerHexer, Derek
Andrews, Des, DharmaDreamer, Dingar, Discospinster, Doc Tropics, Doczilla, Dominus, Dripping Flame, Duncharris, E-citizen, Earlypsychosis, Emperorbma, Emw, Evolutionsucks, Fastfission,
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Haham hanuka, Hairy Dude, Happysailor, Headbomb, Heron, Hkhenson, Hmains, Hqb, Hult041956, Hut 8.5, I do not exist, IRP, Iamsnorlax, Igiffin, Ilyushka88, Insanity Incarnate, Ixfd64,
J.delanoy, JForget, JLaTondre, JRother, Jackie moons, Jagged 85, James089, JamesHilt62, JavaTenor, Jaxl, Jebus989, Jedi6, Jfdwolff, Jimmy Pitt, Jni, JoanneB, JoaoRicardo, Job tungol,
JoeSmack, Jonverve, Joxernolan, Jredmond, Jrockley, Kaiba, Keilana, Kevinmon, Killiondude, King of Hearts, Kukini, Kzollman, LDHan, LFaraone, La goutte de pluie, Ldavies, LedgendGamer,
Lexor, LittleOldMe, Lunakeet, Madhero88, Magister Mathematicae, Mailer diablo, Malo, Manco Capac, MarcoTolo, Marknen, Marquez, Masterofsuspense, Maurog, Mav, Mbc362, Melaen,
Menchi, Mengela, Minimac, Minisimon, Missbay67, Mrl, Mwills011, Myanw, Nakon, Nectarflowed, NellieBly, Nerdygeek101, NewEnglandYankee, Nibuod, Nicolae Coman, Nivix, Nunh-huh,
O, Obey, Ocsadanielsw@hotmail.com, OhanaUnited, PSWG1920, Patrick0Moran, Philip Trueman, Pinethicket, PinkPanthress, Qertis, Qurat-ul-ain Basit, RHaworth, Radagast83, RandomP,
Razorflame, RexNL, Rico12121212, Rico191919, RxS, SEWilco, Sandahl, Sceptre, Sdlr, Sexy Back 16, Shyamal, Simeon24601, Sir Vicious, Skullslayer15, Smigs, Snowmanradio, Some jerk on
the Internet, Sommers, Springnuts, Squirt2711, Stevenmitchell, Superborsuk, Syncategoremata, Synchronism, TableManners, Tail, Tameeria, TedE, Thatguyflint, The Anome, The Man in
Question, The Ogre, The Rambling Man, The Thing That Should Not Be, TheKMan, Tijfo098, TimVickers, Titoxd, Tobby72, Tom.k, Tommy2010, Tony Fox, Transcendence, Trimp, Trusilver,
Tyrenius, Uncle Dick, Uzzo2, Vcolin, Vegetator, Vietbio, Vimescarrot, Vipinhari, Viriditas, Vsmith, WTGDMan1986, Wavelength, Wikieditor06, Will Beback, William Avery, Woohookitty,
Yamamoto Ichiro, YanaGator, Yelyos, Yuanchosaan, Zhou Yu, Александър, 477 anonymous edits

Fitness  Source: http://en.wikipedia.org/w/index.php?oldid=390608842  Contributors: Abrahami, Andrea105, Apparition11, Bheest, Bobblehead, Corvi42, Dj Capricorn, Draicone, Duncharris,
EPM, Edward Ockham, Encyclopedia77, Felinasmith, Flarity, ForestDim, Frenkmelk, Froonyhoob, Furor1, GraemeL, GuyChaham, HTBrooks, Hazzeryoda, Hu12, I am not a dog, Jdvelasc,
Joannamasel, Johnuniq, KimvdLinde, Kjells, Kzollman, Levineps, Lexor, Melanie or mely, Nakon, Nikai, Nuttycoconut, Opabinia regalis, Pariah, Peripitus, Richard.decal, Richard001, Rumping,
Sbeath, Shadowjams, ShelfSkewed, Shiritai, Shot-caller8, Sslevine, Stephenb, Syp, TangentCube, Techman224, TehBrandon, Tide rolls, TimVickers, Timo Honkasalo, Txomin, Uriobolski,
Vachung 82, Vsmith, WAS 4.250, WadeSimMiser, Waldow, Wik, Wimt, Wlodzimierz, XxCrazySnoopxX, YouWillBeAssimilated, 94 anonymous edits

Common descent  Source: http://en.wikipedia.org/w/index.php?oldid=384873781  Contributors: 168..., 84user, Agathman, Alan Liefting, Alexs, Andycjp, Archaeopteryx, Armchair info guy,
Aunt Entropy, Azcolvin429, Bcasterline, Bender235, Bibliophile20, Bubbamagic87, Burris, CanisRufus, Cat Whisperer, Categorer, Catgut, Cement123, Ceyockey, Cheddarbob23, Christian
Skeptic, Conversion script, Cribbswh, Curtis Clark, Cyde, DLH, DRosenbach, Dawn Bard, Deeplogic, Deglr6328, Demfranchize, Dfinch, Digitwoman, Dionyseus, Doc Tropics, Donarreiskoffer,
Dtheobald, Ec5618, Ed Poor, Edward, Ewe nik, FeloniousMonk, Filll, Finell, Firsfron, ForestDim, Frank101, GSlicer, Gabbe, Glen, Guettarda, Haggiaomega, Harburg, Headbomb, Henrygb,
Horselover Frost, Infraredeclipse, J.delanoy, JH-man, JHunterJ, Jarhed, Jebus989, Jim62sch, Jogers, Johnuniq, Join Tile, Jondw, Jorgesalgueiro, JoshuaZ, Keegscee, Kjkolb, Lexor, Littlealien182,
Livingrm, Logicus, Martial75, MartinHarper, Mausy5043, Mccajor, Menchi, Michael Johnson, Mr. Wheely Guy, Naddy, Nihiltres, Northfox, Nwbeeson, Octavian history, Opie, Orangemarlin,
PDH, Palnatoke, Pavel Vozenilek, Pbarnes, Peak, Persian Poet Gal, Petri Krohn, Pmanderson, PoolPartay, Poor Yorick, Princeofexcess, RHaworth, Rafikgl, Randwicked, Rgamble, Rich
Farmbrough, Richard001, Robert Stevens, Rogue-pilot, Sam Hocevar, Samsara, SheffieldSteel, SpuriousQ, Stiepan Pietrov, Strictscrutiny, Sven Heinicke, Thomas Arelatensis, TimShell, TomS
TDotO, Tomtheman5, Traxs7, Ungtss, Valich, Vanished user, Vsmith, WAS 4.250, Webridge, Winterschlaefer, Zappernapper, 104 anonymous edits

Evidence of common descent  Source: http://en.wikipedia.org/w/index.php?oldid=392814660  Contributors: 10outof10die, 1exec1, Aalexandros, Adrian J. Hunter, Agathman, Aianrnoens,
Alienus, Allstarecho, Altenmann, AmericanKido, Anarkisto, Andonic, Andrewpmk, Andreybigb, AnonMoos, Antandrus, Antiuser, Apokryltaros, Aquishix, AresAndEnyo, Armchair info guy,
ArthurWeasley, Ashnard, Asrghasrhiojadrhr, Aunt Entropy, Auntof6, Authorized User, AxelBoldt, Axeloide, Azcolvin429, Azeleas=awsome, Aznmastermind5, B00P, BW52, Bairh, Balzi,
Beland, BenB4, Bkkbrad, Blacklake, BlaiseFEgan, BlueGoose, BlytheG, BrainUser, Brightmoon, Can't sleep, clown will eat me, CanisRufus, Carradee, Cavrdg, Cerealkiller13, Christian Skeptic,
ClamDip, Condem, Crystallina, DO11.10, DRosenbach, DabMachine, DancingPenguin, Daniel J. Leivick, Daniel5127, Danielrcote, Darrenhusted, Dave souza, David Gerard, Davril2020, Dawn
Bard, Dekimasu, Dfarrar, DiLLuS, Diannaa, Digitwoman, Digwuren, Dinofan135, Dionyseus, Dougweller, Drbug, Dreadstar, Dsbrod, Dude112233, Duncharris, Dziewa, Eall Ân Ûle,
EarthRise33, Ec5618, Ed Poor, EdJohnston, Eeekster, Eequor, ElijahOmega, Enviroboy, ErikHaugen, Ezra Wax, Fama Clamosa, FeloniousMonk, Fences and windows, Filll, Firsfron, Fubar
Obfusco, G4rfunkel, GSlicer, Gaius Cornelius, GeneralBelly, Geoff, Gimmetrow, GlassFET, Godisnotmocked, Gombo, Grafen, Graft, GreatWhiteNortherner, Gregbard, GromXXVII, Guettarda,
Gurch, GusChiggins21, Haemo, Harley peters, Headbomb, Herbee, Hesperian, HiEv, Hmains, Hrafn, Hugin&Munin, Hut 8.5, Ian.thomson, Icairns, Imjustmatthew, Io Katai, J.delanoy, JFFCakes,
JH-man, JaGa, Jefffire, JeremyA, John D. Croft, Johnuniq, Jon186, Jooler, JoshuaZ, Jpbowen, Julianonions, Jusdafax, JustSomeKid, K, Kafziel, Kdbuffalo, Kilonum, Kingdon, Kjkolb,
Knowledge Seeker, Koveras, Kraziur, Kuru, La hapalo, Lantios, Leptictidium, Lexor, Likeminas, Lindert, Lizard1959, Ljhliesl, LossIsNotMore, M, MAURY, Man with two legs, Maniadis,
Mboverload, Mcy jerry, Meggar, MetsFan76, MichaelSH, Mindmatrix, Missvain, Morenooso, Moulder, Mouse555, Mouse8128, Myanw, Nadiatalent, Nads240721, Nahallac Silverwinds,
Nbound, Northfox, Obli, Ollyoxenfree, Omicronpersei8, Onevalefan, Orangemarlin, Orion 5, Ospalh, Ourai, PAK Man, PMDrive1061, Paul August, Pgk, PhilipO, Piano non troppo, Pinotgris,
Pkeck, Plumbago, Portillo, Prohlep, Pterodactyler, Quietmarc, Qxz, R Lee E, RDBrown, Rambam rashi, Ramdrake, Ratphobia, Reedy, Reinis, Reinyday, Rhobite, Rich Farmbrough, Richard001,
Richhoncho, Rjwilmsi, Robert Stevens, Rock nj, Roland Deschain, Rory096, Run!, Rusty Cashman, Ryanmcg2006, Sammalin, Samsara, Sander Säde, Sander123, ScientistDragonmouse,
Security`57, Sharkface217, Shenme, Shrimp wong, Silence, Silly rabbit, Slrubenstein, Smalljim, Smith609, Snalwibma, SomeStranger, Soulkeeper, Sp, Spammer34567, Splanxna, SpuriousQ,
Sraoof18, Stemonitis, SteveBaker, Sylentkorean, Szquirrel, T.J.V., TDogg310, Tamfang, Taneli HUUSKONEN, Teapotgeorge, Tedernst, Teenageactivist, The Anome, The Matrix Prime,
Article Sources and Contributors 448

TheChrisD, TheIncredibleEdibleOompaLoompa, TheresaWilson, Therucks, Thomas Arelatensis, Tide rolls, TimVickers, Tktktk, Tmol42, Tonicthebrown, Trek-a-Tolk-a-Lewisite, Triona,
Turkishbob, Tycho, Ucucha, UkPaolo, UncleBubba, Usernodunno, UtherSRG, Vanished user, Venmon, Virginia Dutch, Viridae, Volfy, Vsmith, WAS 4.250, Whittrocks, WikiDisambiguation,
Wilhelm meis, Wolfrock, Woohookitty, Writtenallover, Wtmitchell, Yamamoto Ichiro, Yath, Ychennay, YechezkelZilber, Zahid Abdassabur, Zerokitsune, Zundark, ZxqamF, 351 anonymous
edits

Adaptation  Source: http://en.wikipedia.org/w/index.php?oldid=392416091  Contributors: 0zymandias, 10outof10die, Abdullais4u, Addaick, Addshore, Aitias, Alansohn, Alex314058,
Amcbride, Andonic, Andre Engels, Andres, Angusmclellan, Antiuser, ArchStanton69, Archanamiya, Arnold90, Aunt Entropy, Azcolvin429, BananaFiend, Bencherlite, Bender235, Bhadani, Big
iron, Bigger digger, Bluerasberry, Bobamnertiopsis, Bobo192, Bongwarrior, Brianga, CanbekEsen, Cfsenel, Cimex, Cvata, DARTH SIDIOUS 2, DJ Clayworth, DMacks, Da monster under your
bed, Danski14, DeadEyeArrow, Deathgod1995, Delmonte, DerHexer, DerekLaw, Deskana, Dmanning, Dmitri Lytov, Doc Tropics, Doczilla, Dodgydobson, Dr Dima, Dxballer08,
Dysmorodrepanis, EPM, Egmontaz, ElectricRay, Electrified mocha chinchilla, Elliskev, Enlil Ninlil, Epbr123, Eptalon, Eric-Wester, EverSince, Ex nihil, Extremophile, FT2, Fanatix, Fangfufu,
Favonian, Femto, Finalius, FinnWiki, Fl, Friginator, Gabbe, Gadfium, Gaius Cornelius, Gary King, Ghost2, Gimme danger, Gioto, Gogo Dodo, Golden.josh, GoldenTorc, Graham87, Gtstricky,
Gunnar Mikalsen Kvifte, Guyzero, Habbilow, Habj, Harland1, Hede2000, Hornlitz, ImpalerBugz, Iridium ionizer, Irixman, J.delanoy, J04n, JaGa, Jackelfive, James086, Jeff G., Jerzy, Jisily,
Joannamasel, Jobin104, Joelmills, John, Johnuniq, Joie de Vivre, Josh Parris, Juliancolton, Jwing79, Kbh3rd, Keilana, Kingjalis3, Kipholbeck, Korou, L Kensington, Lawrence Cohen,
LazyBoi633, Leandro Palacios, Lexor, Lindenburg, Liontooth, MBisanz, MCTales, Macdonald-ross, Majorly, Mandarax, Marek69, Martial75, Mc4th, Mchavez, Melsaran, Memills, Mentifisto,
Mercenario97, Methcub, Michael Hardy, MigueldelosSantos, Mike.lifeguard, Minimac, Miquonranger03, Mrsssgt, Muad, Munita Prasad, Mx740, Myanw, NYKevin, Nascar1996, NeilN,
Nethgirb, Nihiltres, NuclearWarfare, Numbo3, Nut-meg, Ocaasi, On the other side, Openstrings, PAR, Paps 70, Pdorrell, Pete.Hurd, Philip Trueman, Pigman, Pilotbob, Pip2andahalf,
PleaseStand, Plumpurple, Polinizador, Porqin, Protez, Pyrrhus16, Rang3rofskil, Ravenswood Media, Razorflame, Reconsider the static, Redwrathe, RexNL, Rgoodermote, Rich Farmbrough,
Richard001, Rjwilmsi, Ronhjones, RoyBoy, Royboycrashfan, S3000, Salamurai, Salvio giuliano, Samsara, Sander123, Seahorseruler, Sewings, Shanes, Shenme, Shirulashem, SixteenBitJorge,
Smartse, Snek01, Soccerdu82, SomeStranger, Steel, Steinsky, Stemonitis, Steven Zhang, Stevertigo, StripeyBadger, Sushant gupta, Svick, The Claw, The Nut, The Thing That Should Not Be,
Tiddly Tom, Tide rolls, Timo Honkasalo, Tio1, Tombomp, Tommy2010, Townmouse, Trusilver, Uncle Dick, Unint, Van helsing, Vangoghhasamachette, Vespristiano, Vipinhari, Vsmith,
Waggers, Waldow, WaysToEscape, Werdan7, WikiDao, WikipedianMarlith, Wimt, Xezbeth, YDaniel7, Yuanchosaan, Z10x, ZeroJanvier, Zhou Yu, ZuluPapa5, İnfoCan, 597 anonymous edits

Genetic drift  Source: http://en.wikipedia.org/w/index.php?oldid=390717271  Contributors: 10outof10die, 168..., 21655, 9mw, Abdullais4u, Aericanwizard, Ahoerstemeier, Ajgorhoe, Alansohn,
Aliekens, Amit man, Andre Engels, AnonMoos, Archie Paulson, Atulsnischal, Bendzh, BiT, Bill37212, Bobo192, Bomac, Borgx, C. A. Russell, CWY2190, CanbekEsen, Cohesion, Courcelles,
Dendodge, DianaGaleM, Discospinster, Donama, Duncharris, Dwheeler, Dysmorodrepanis, Edsova, Electric goat, Eloquence, Ettrig, Etxrge, FF2010, Fireyair, Flashinfinity, Forluvoft,
Freakoverdose, Freerow@gmail.com, Fubar Obfusco, GD, GK, Gaius Cornelius, Giftlite, Gilliam, Gimme danger, Giordanobruno, Graft, GrahamN, Guettarda, Haetmachine, Hatch68, Huji, Hut
8.5, JWB, Jcobb, Jebba, Jeffmcneill, Jheald, Joannamasel, JohnOwens, Johnuniq, Julian Mendez, Kcordina, KimvdLinde, Lavateraguy, Lexor, Lingwitt, Maedin, Mattb112885, Mav, Megan1967,
Mokotillon, Mortartion, Mouseomatic, Narayanese, Natalie Erin, NickSeigal, Nk, Nmerriam, Nomer0591, Notjimsteele, Octopus-Hands, Omc, Pgan002, PhDP, Pixeltoo, Poethical, Professor
marginalia, RJC, Rat at WikiFur, RedWolf, Reinyday, RexNL, Rich Farmbrough, Risk one, Ronhjones, Samsara, Sasata, Sdarwin, Shadowjams, Showgun45, Sir Nicholas de Mimsy-Porpington,
Slrubenstein, Someone else, Standardfact, Steinsky, Susan118, Tannin, Technopilgrim, TedE, Template namespace initialisation script, Tempodivalse, The Anome,
TheIncredibleEdibleOompaLoompa, TimVickers, Timwi, Tom harrison, Tothebarricades.tk, Tuxedo junction, Vanished user, Versus22, WAS 4.250, WikiHigor, Z10x, 197 anonymous edits

Gene flow  Source: http://en.wikipedia.org/w/index.php?oldid=391795037  Contributors: 10outof10die, Abdullais4u, Ahoerstemeier, Aircorn, AnonMoos, Apers0n, Atubeileh, Atulsnischal,
Bakerccm, Balohmann, Bar fly high, BiT, Borgx, Calmypal, CanbekEsen, Chewie, CryptoDerk, Decltype, Dlohcierekim's sock, Duncharris, Dysmorodrepanis, Ettrig, Foant, ForestDim, GSlicer,
Guettarda, I am not a dog, Isilanes, Ixfd64, JSpudeman, JellyWarriorAllele, Jennavecia, Johnuniq, Lab-oratory, Leek Francis, Leptictidium, Lexor, LifeScience, Michael Hardy, Muntuwandi,
Nadsozinc, Nakon, Nectarflowed, NickSeigal, Noclevername, Odiem00n, Pengo, Piperh, R'n'B, Richard001, Rjwilmsi, Samsara, Satyrium, Seb951, Shaocc, Sleigh, Sugarfish, Suisun, Talking
image, Template namespace initialisation script, TheOtherJesse, Vicenarian, WAS 4.250, Yamamoto Ichiro, Zandperl, Zerothis, 65 anonymous edits

Mutation  Source: http://en.wikipedia.org/w/index.php?oldid=390815129  Contributors: 0612, 478jjjz, 4v4l0n42, Abdullais4u, Abergabe, Abstraktn, Academic Challenger, AdamXtreme18,
Adenosine, AdjustShift, Agathman, Agreene175, Ahoerstemeier, Aitias, Ajoust, Alansohn, Alasdair, Alchemes, Aled 12345, Alex tudor, Alikingofkings, Allstarecho, Amorymeltzer, Anastacie,
Andres, Ansell, Anypodetos, Arcadian, Archanamiya, ArielGold, Arjun01, Aunt Entropy, Axel Driken, Azcolvin429, Bayerischermann, Bensaccount, Bevo, Bioephemera, Biskot, Bobo192,
Boing! said Zebedee, Bomac, Bongwarrior, BorisTM, Bradshej, Brentt, Brian Kendig, Brian0918, Bryan Derksen, Cal 1234, Calvin 1998, Camw, Can't sleep, clown will eat me,
CanadianLinuxUser, Cantus, Capeo, Capricorn42, Carifio24, Ceranthor, Ceyockey, Cgingold, Chain funds, Chaosof99, Chopchopwhitey, ChrisTheBrown, Chrislk02, Christinebenson58,
Christomaniac76, Ciar, Clappingsimon, ClockworkSoul, ClockworkTroll, Closedmouth, CodeCat, Conversion script, Corpx, Courcelles, Crazy Boris with a red beard, Crazynas, Credema,
Cremepuff222, Culverin, Curehd, Cww, Cyde, D6, DVD R W, Daarznieks, DanielCD, Dante mars, Dantecubed, David D., Davidhorman, Daycd, Dcooper, DeadEyeArrow, Delldot, DerHexer,
Derek Ross, Deville, Dhollm, Dingopup, Dinosaurdarrell, Discospinster, Dlohcierekim, Dncarley, DoctorDNA, Dr d12, Drew R. Smith, Drmies, Duncharris, Dureo, Dysmorodrepanis, EWS23,
Eagleal, Ed Poor, Egmontaz, Ehrenkater, Eleassar, Elvin fimel, Emw, Enviroboy, Epbr123, Equendil, Ettrig, Etxrge, Exponent, Faradayplank, Faustnh, Fedir, Filll, Firebat08, Flewis,
Flowerpotman, Forluvoft, Frank Lofaro Jr., Frankie816, Fungusnunchuck, Furrykef, GSlicer, Gabbe, Gail, Gcm, Gcrossan, Genenome, Giftlite, Gilgamesh he, Gimme danger, Gog,
GoodScienceForYou, Gr8niladri, Gracenotes, Graevemoore, Gsmgm, Guettarda, Guillom, Gurch, Gusgould, Gwernol, HJ Mitchell, Hadal, Haetmachine, Hanmi74, Harland1, Hede2000,
HiDrNick, Hobartimus, Hogyn Lleol, Hut 6.5, Hydrogen Iodide, Hylobius, ITxT, Ian Dunster, Icek, Ifiber, Imarockstarfoo, InfoCan, Instinct, Ioeth, Irishguy, Ivan Bajlo, J.delanoy, JForget,
JWSchmidt, Jakeisbaked, Jakirfirozkamal, Jason.Rafe.Miller, Jason7825, Jcorry10, Jeff G., JerryFriedman, Jiddisch, Jiy, Jmjanzen, JoanneB, Joejoeftw, John Reaves, JohnRobertMartin,
Johnpseudo, Johnuniq, Jojhutton, Jon Cates, JosephCCampana, Joycierules, Joyous!, Jrockley, Juicy fisheye, Jungenbergs, Jusdafax, Kahkooi, Karajade, Katalaveno, Kazkaskazkasako,
Kdawson66, Keegan, Ketiltrout, Khatru2, Kim Bruning, Klgroom, KnightofZion, Kodemage, Kpjas, Ktfreese, Kubigula, Kungfuadam, Kupirijo, LFaraone, Lavateraguy, LeadSongDog,
LeoNomis, Leonard^Bloom, LestatdeLioncourt, Letatcestmoi94, Lewa.27, Lexor, Lid6, LindsayH, Livajo, Lordlosss2, Lothar von Richthofen, LovesMacs, Lradrama, Lupo, MIT Trekkie,
MONGO, Madeleine Price Ball, Maedin, Magnus Manske, Makemi, Malcolm Farmer, Marek69, Marj Tiefert, Markhurd, Mashford, Matdrodes, Mauler90, Mav, Mboverload, MeSoDark,
Meaghan, Meepmoop, Mentifisto, Methcub, Metzenberg, MiRroar, Micha L. Rieser, Michael Hardy, Michael Johnson, Mikael Häggström, Mike6271, Millahnna, Mintleaf, Miquonranger03,
Misza13, Mjb, Mouse555, Mxn, Myanw, Nabarry, Naohiro19 revertvandal, Narayanese, Ncfuzzy101, Ndteegarden, Netnuevo, Nezzadar, Ngsmart, Nhandler, Nikai, Nikola Smolenski, Ninly,
Nixeagle, Novangelis, NuclearWarfare, Nunh-huh, Ocon, Oda Mari, Oleksii0, Oliver Lineham, Omegatron, Oneiros, Ooikahkooi0507, Oxwil, Oxymoron83, PDH, Pakaran, Palnatoke,
ParisianBlade, ParticleMan, Pb0823, Peachiezworld, Pengo, Peternewell, PhDP, Phantomsteve, Pharaoh of the Wizards, Phenz, Phlyght, Piano non troppo, PierreAbbat, Pigman, Pinethicket,
PizzaBox, Planettelex23, Plop, Plumbago, Poechalkdust, Ppgardne, Quadell, Quintote, Quizkajer, RDBrown, Rabo3, Radagast83, Radon210, Ragesoss, Rahul sig, RainbowOfLight, Reedy,
Res2216firestar, RexNL, Rgamble, Robert Stevens, Rogerd, Roke, Roland Deschain, Romanm, Rrburke, Rror, Rustygin, Ryanjunk, SMC89, Saganaki-, SallyForth123, Samsara, Sancassania,
Sander123, Sango123, Savant13, ScaldingHotSoup, Scepia, Sceptre, SchnitzelMannGreek, Seb951, Semperf, Seven of Nine, Shanel, Sharonlees, Sheitan, Shell Kinney, Shirik, Shogun, Sikatriz,
SimonSayz, SineCurve, Sintaku, Sionus, Sithu.Win, Sk741, Skysmith, Snigbrook, Solenoozerec, Somnathroy, Specs112, Standinguptoit, Standonbible, Stardust8212, Steinsky, Stephenpratt,
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High Fin Sperm Whale, The Thing That Should Not Be, Thebestlaidplans, Thedude212, Thewall2, Thingg, Thue, Tide rolls, TimVickers, Timwi, Toastybread, Tohd8BohaithuGh1,
TomTheHand, Trichodinamitra, Tuganax, Tupeliano, Turnstep, Tuxedo junction, Ukexpat, Uncle Dick, VK35, Violetriga, Voyajer, WAS 4.250, Waggers, Watchdogb, Wavelength, Wayne
Olajuwon, Wedian, WhatTheBlack, Whosasking, Wickey-nl, Wiki alf, WikiDao, Wikibofh, Wimt, Wmahan, Wouterstomp, Xyzzyplugh, Yamamoto Ichiro, YassineMrabet, Zargulon, Zephyris,
Zsingaya, Zurrr, Zzyzx11, 838 anonymous edits

Natural selection  Source: http://en.wikipedia.org/w/index.php?oldid=393098533  Contributors: -Ril-, .:Ajvol:., 10outof10die, 12345ryan12345, 15lsoucy, 15mypic, 168..., 2468Aaron, 5 albert
square, 65.96.132.xxx, 7, A8UDI, AC+79 3888, Aadamescu, Aaron Bowen, Abc518, Abdullais4u, Adriaan, Agathman, Aitias, Akeldamma, Alai, Alan Liefting, Alansohn, Alienus, Allangmiller,
Amaltheus, Amcguinn, Amorymeltzer, Andonic, Andrea105, Annasweden, Antandrus, Arakunem, Aranel, Arjun01, Artichoker, Atlas1, Atulsnischal, Aunt Entropy, Avillia, Axel147, AxelBoldt,
Az1568, Backslash Forwardslash, BananaFiend, Barefootmatt, Barsonian20, Batmanand, Bcasterline, Ben1002, Benhocking, Bheest, Big Bird, Bobkenshaw, Bogey97, Bomac, Bongwarrior,
BrokenSegue, Bueller 007, Buickid, Bwangia, Bwhack, CJLL Wright, CSWarren, CWY2190, CWii, CYD, Calliopejen1, Calvinloa, CanadianLinuxUser, Cannaya, Captain-tucker, CardinalDan,
Carlroller, CharlotteWebb, Chazza 94, Ches88, Childhoodsend, Chris 73, Chris55, ChrisCork, Circeus, Citizen Premier, Closedmouth, Code Burner, Cohesion, ConfuciusOrnis, Conversion script,
Cool3, Cooner7777777, Copypaste45, Cossey mo, Courcelles, Cp111, Cpu111, CreationScientist, Cremepuff222, Cyde, D, DARTH SIDIOUS 2, DGG, DMacks, DVD R W, DabMachine,
Daggermouth, Daleep123, Dan100, Dancey2, Danimoth, Danthedude, Dardasavta, Darwinek, Dave souza, David D., Davril2020, Dawn Bard, Defender of torch, Delldot, Derek Ross, Deryck
Chan, Deville, Diego pmc, Discospinster, Dmerrill, Dnvrfantj, Doc Tropics, Doc glasgow, Dockingman, DoktorDec, Donarreiskoffer, Dr d12, DrMontik, Dreadstar, Duckling78, Duncharris,
Dunn8, Dweje, Dycedarg, Dysepsion, Dysmorodrepanis, EPM, ESkog, Eatme20005, Ec5618, Ed Poor, EdwinHJ, Edwy, Eeekster, Eisnel, Eliyak, Emw, Ency456, Enfresdezh, Engelmann15,
Enviroboy, Epbr123, Eperotao, ErgoSum88, Ettrig, EuPhyte, Excirial, Extremophile, FCSundae, FCYTravis, FF2010, Fanatix, Farquaadhnchmn, Fastfission, FayssalF, FeloniousMonk, Flubajub
boy, Forluvoft, Fox, Freedom to share, GLaDOS, GSlicer, Gabbe, Gaius Cornelius, Galygal, Ganny, Garcsera82, Garik, Gawaxay, Gclassballer, GeneralAtrocity, Genetics411, Geologyguy,
GetAgrippa, Giftlite, Gimboid13, Gimme danger, GirasoleDE, Gleng, Gniniv, Goethean, Gracenotes, GraemeL, Grafen, Graft, Graham87, Grcaldwell, Guettarda, Guitarist0820, Gurch, Gwernol,
HIGA, HTBrooks, Hadal, Hadrians, HalfShadow, Hannes Röst, Harry R, Harryboyles, Headbomb, Hensa, HexaChord, Hobartimus, Hoppity25, Hordaland, Hornlitz, Hrafn, Husond, Hydrogen
Iodide, I try this account, IMatthew, IRP, Ian Dunster, IanCheesman, Ideogram, Immunize, InBalance, Indosauros, Iridescent, Isilanes, Izehar, J.delanoy, JHunterJ, JaGa, Jackelfive, Jackol,
Jagged 85, Jamesooders, Jamie Lokier, Javascap, Jaxl, Jcurious, Jebus989, Jeff G., Jefffire, Jerry Zhang, Jessisamaknows, Jinxed, Jkoeslag, Joannamasel, John Lynch, John Vandenberg,
Johnstone, Johnuniq, Join Tile, Jonahib, Jonathanstray, Jonny1q2w3e4r5t6y7u8i9op, Josh Grosse, JoshuaZ, Jusdafax, Jwissick, JzG, K, Kaarel, Kalv372, Katalaveno, KathrynLybarger,
Kazikameuk, Keilana, Kevin aylward, Khoikhoi, KillerChihuahua, KimvdLinde, King of Hearts, Knowledge Seeker, KnowledgeOfSelf, Kosnapyo, Kubra, Kungfuadam, Kuru, Kyknos, Kyoko,
Kzollman, LAX, Larrybarry, Lazylaces, Leafyplant, LeaveSleaves, Lee Daniel Crocker, Leithp, Leuko, Lexor, Lightmouse, Limbo socrates, Livajo, Logan, LookingGlass, Loren1994, Lotje,
Lova Falk, Lowellian, Luna Santin, Luuva, MAXimum Xtreme, MC10, MECU, MKS, Mac mckinlay, MacMed, Macy, Magister Mathematicae, Magnus Manske, Malcolm Farmer, Malevious,
Mann jess, Marcosantezana, Master of Puppets, Mav, Mboverload, Mc4th, Mccready, Michael Devore, Michael Johnson, Mihoshi, Mike2vil, Mindmatrix, Mintleaf, Mkpg, Mlpkr, Modulatum,
Article Sources and Contributors 449

Moe Epsilon, Moreschi, Mr. Wheely Guy, MrOllie, MrSomeone, MrStalker, Mzsabusayeed, N4nojohn, Naddy, Nakon, Narayanese, Nareek, Natalie Erin, Nate1481, Natisto, NatureA16,
NawlinWiki, Neapoli, Neptune5000, NerdyScienceDude, Nethgirb, Neutrality, NickCT, Nikola Smolenski, Nixeagle, Nlu, No Guru, Nsaa, Nudve, OLH06, Okedem, Oking83, Olianov,
Ombudsman, Opabinia regalis, Orangemarlin, Ormy, Oxymoron83, PDH, Patstuart, Paul Hjul, Pawyilee, Pepper, Persian Poet Gal, Pete.Hurd, Peter morrell, Petri Krohn, PhJ, Pharaoh of the
Wizards, Philip Trueman, Pinethicket, Pinkgirl941222, Polly, Poo HEAD JESS, Ppe42, Pschemp, PseudoSudo, Purnajitphukon, Quizkajer, Qxz, R, RGTraynor, RUL3R, Radiocar, Radon210,
Ragesoss, RandomStringOfCharacters, Raven in Orbit, Ravenswood Media, Razorflame, Rdsmith4, Recognizance, RedAlphaRock, RedHillian, Redian, Redsunrising15, Regancy42, RexNL,
RhiannonAmelie, Richard001, RickK, Rickproser, Rjwilmsi, Robert Stevens, Roland Deschain, Romanm, RoyBoy, Royalguard11, SEJohnston, SJP, Sam Clark, Samashton, Samsara, Samuell,
Sander Säde, Sandman, Sandstein, SandyGeorgia, Sango123, Scibah (new account), ScienceApologist, Scndlbrkrttmc, Sean.hoyland, Separa, Seqsea, Sergeantbreinholt, Sfmammamia, SgtDrini,
Shanel, Shanes, Shazalusose, Shenme, Shoemaker's Holiday, Sholto Maud, Sid mishra94, Sietse Snel, Silly rabbit, Sjö, Skydog100, Slakr, Slon02, Slowking Man, Slrubenstein, Sluzzelin,
Slysplace, Smmurphy, Snailwalker, Snalwibma, Snigbrook, Snowmanradio, Snoyes, Spamsara, Spiritia, SpuriousQ, SqueakBox, Staffwaterboy, Standonbible, SteinbDJ, Steinsky, Steven Argue,
Striker2712, Sundar, Syncategoremata, TEPutnam, Taffboyz, Takometer, Tameeria, Tea Tzu, TedE, Tellyaddict, Template namespace initialisation script, Thankyousir8, The Anome, The
Merciful, The Thing That Should Not Be, TheProject, Thehelpfulone, Thesoxlost, Thingg, ThisIsAce, Thomas Arelatensis, Tide rolls, TimVickers, Timwi, Tito-, Titoxd, Tktktk, Tmol42, Tobias
Bergemann, Toddst1, TomGreen, TongueSpeaker, Tony1, Trevor MacInnis, Tristanf12, Triwbe, Tslocum, TutterMouse, Tuxedo junction, Twaz, Tyw7, Ugen64, Ulluxo, Ulric1313, Ummhihello,
Uncle Dick, Uncle Milty, UncleBubba, Vanished user, Verson, VirtualDelight, Vsmith, Wafulz, Waldow, Walkingwithyourwhiskey, Wayward, Welsh, West.andrew.g, WikiRat1, Wikichickenlol,
Wilhelm meis, Willking1979, WillowW, Wimt, WinContro, Wmahan, Woland37, Wykis, Wykymania, Xaosflux, Yamamoto Ichiro, Yerpo, Yousalame23, Yue44003, Zbvhs, Zephae,
ZeroJanvier, ZjarriRrethues, Zro, Zsinj, Île flottante, 1180 anonymous edits

Speciation  Source: http://en.wikipedia.org/w/index.php?oldid=392458047  Contributors: -Ril-, 100110100, 168..., 200.191.188.xxx, Abdullais4u, Agathman, Ajsh, Alastair Haines, Alex.muller,
Amaltheus, Ameliorate!, Ann arbor street, Anthere, Antipastor, Arakunem, Armchair info guy, Atulsnischal, Aunt Entropy, AxelBoldt, Azcolvin429, BSquared04, Basher018, Bcasterline,
Beland, BenB4, Benthehutt, Berton, Betterusername, Biol433, Blue Tie, Bobo192, Boreal99, Boredzo, Boston6788, Bryan Derksen, Bueller 007, CKCortez, Calair, Calaschysm, Can't sleep,
clown will eat me, CanisRufus, CardinalDan, Chris Roy, ChrisCork, CinchBug, ConfuciusOrnis, Conversion script, CzarNick, Dante Alighieri, Darth Panda, Dave souza, Dawn Bard,
Dayewalker, Debresser, Diagonalfish, Diannaa, Dj Capricorn, Dmerrill, Dmitri Lytov, Dr d12, Drphilharmonic, Duncharris, Dysepsion, Dysmorodrepanis, DéRahier, ESkog, Ed Poor, Egern,
Eratosignis, Ettrig, Euyyn, Evolve17, Extra999, Fastfission, Fastily, Fbartolom, ForestDim, Frankenpuppy, Gabbe, GoEThe, Gogo Dodo, Graft, GraphicArtist1, Greeneto, Grimey109, Guettarda,
Gökhan, Headbomb, Heron, Hkim43, Hu12, I dream of horses, IanCheesman, Ilmari Karonen, Imasleepviking, Inferno, Lord of Penguins, J.delanoy, JRR Trollkien, JackH, Jamiejoseph,
Jasmaunder, Jerainseltran, Jmeppley, Johnuniq, Jojhutton, Joriki, JoshuaZ, Jrockley, Juan448, Julian Mendez, Juliancolton, Junyor, Justanotherdomino, Karada, Katalaveno, Kazvorpal,
KimvdLinde, Knownot, Lakmiseiru, LeaveSleaves, Lee Daniel Crocker, Leet3lite, Levineps, Lexor, LossIsNotMore, MB83, Magnus Manske, Manitobamountie, MarcoTolo, MarkGallagher,
Marknau, Matthias.mace, Mav, Mdsam2, Mendaliv, Mensfortis, Michael Hardy, Michael Johnson, Michael93555, MichaelBillington, Mikespedia, Mindmatrix, Modify, Mokele, Moshe
Constantine Hassan Al-Silverburg, NCC-8765, NielsHietberg, Noctibus, Noodleman, Nrcprm2026, Nurg, O, OGoncho, Onevalefan, PDH, Palica, Pallab1234, Pathoschild, Pharaoh of the
Wizards, Ppe42, Professor marginalia, Psarj, Pschemp, Quailman, Quietmarc, RJaguar3, RK, Raymondwinn, RexNL, Rich Farmbrough, Richard Arthur Norton (1958- ), Rjwilmsi, Rmhermen,
Robert Stevens, RoyBoy, Rusty Cashman, Ryulong, Sabik, Sacquebout, Sadalmelik, Samsara, Schnolle, Scilit, Seb951, Shyamal, Sikatriz, Sirkad, Skysmith, Slrubenstein, SomeStranger, Stefan
Kruithof, Susan118, Template namespace initialisation script, The Thing That Should Not Be, The sock that should not be, TheAlphaWolf, Time9, TorreFernando, Toytown Mafia, Ultramarine,
Unyoyega, User6985, Valich, Vaughan Pratt, Vercillo, Veryhuman, Victor falk, Visionholder, Vsmith, WAS 4.250, Who then was a gentleman?, WikiDao, WillJeck, Wintran, Wmgetz, Wobble,
Woohookitty, Yamamoto Ichiro, Zhou Yu, 332 anonymous edits

Phylogenetics  Source: http://en.wikipedia.org/w/index.php?oldid=390075235  Contributors: AS, Agathman, Akriasas, Amaltheus, Andres, Andycjp, Aranae, BD2412, Beland, Benbest, Bendzh,
Benpayne2007, BlackPh0enix, Bomac, Bonadea, Brandon, Bruno Dantas, Bwsmith1, C.Fred, Carlosp420, Circeus, ConcernedVancouverite, Consist, Conversion script, Cybercobra, D I
Williamson, DianaGaleM, Discospinster, Dkabban-GMU, Dpr, Drdaveng, Drphilharmonic, Dysmorodrepanis, EJF, Ecorahul, EdJohnston, ElfQrin, Emaraite, EncycloPetey, Enzymes-GMU,
Eroston, Eyallow, F.j.gaze, Fastily, Gilliam, GoEThe, GreatWhiteNortherner, Grendelkhan, Gruzd, Gurch, Hadal, Hadrianheugh, Halidecyphon, Huji, Huson, Imagine-GMU, Inquam, Jan
Pospíšil, JerrySteal, Johnuniq, Juliokhat, Kevin Saff, KillerChihuahua, Kku, Kosigrim, Ksbrown, LOL, Lapaz, Lexor, LilHelpa, LoganFrost, MAH!, Mario1952, Martinwguy, Michael Hardy,
MrDolomite, Mygerardromance, Naj-GMU, Nakon, Neelix, Netsnipe, Nielses, Noleander, Nomoskedasticity, Nurg, Omnipedian, Opabinia regalis, Opie, Pexego, Ph.eyes, Pinethicket, Poethical,
Predheini, Quiddity, Rasmuss, Recordinghistory, Restre419, Richard001, Rjwilmsi, Rossami, Rossnixon, Samsara, Samw, Santa Sangre, Sedulus, Sentausa, Shyamal, SidP, SimonGreenhill,
Sinbad68101, Slack---line, Sluzzelin, Smith609, Snowmanradio, Springbok26, Stevegiacomelli, Stfg, Swithrow2546, Syp, Template namespace initialisation script, Thatguyflint, TheCatalyst31,
Themfromspace, Thorwald, TimVickers, Tofof, Tommy Kronkvist, Tony Sidaway, TotoBaggins, Touchstone42, Unyoyega, UtherSRG, Vanished User 0001, Verbist, Wgmccallum, Whatiguana,
Who, Wickey-nl, Woudloper, Wzhao553, XCalPab, Yuekling, Zfr, Zvika, 140 anonymous edits

Cladistics  Source: http://en.wikipedia.org/w/index.php?oldid=392634694  Contributors: 10outof10die, 130.94.122.xxx, 172.153.96.xxx, 2004-12-29T22:45Z, 9eyedeel, ABF, APH, Adrian,
Afasmit, Agathman, Ahoerstemeier, Alarichall, Aldenrw, Anaxial, Andycjp, Aranae, Armchair info guy, AshLin, Athf1234, Avb, Azzors, BadDoggie, Ballista, BananaFiend, Beland,
BenFrantzDale, Berton, Bigturtle, BiologyForksWA, BirdValiant, Blechnic, Bobblewik, Bobo192, Bomac, Bosmon, Branko, Breandandalton, Brian0918, Bruno Dantas, Brya, Buffison, Bz75,
C.Fred, Capitaljay, Carlaude, Carlosp420, Cephal-odd, Chameleon, Chewie, Christian Kreibich, Cladist, Cmporter, Colonies Chris, Consist, Consists, Conversion script, Corpx, Craigy144,
Cromwellt, Cthompson, Cyde, DMG413, David Gerard, Dbabbitt, Debivort, Deltabeignet, Demi, Dexterhaven, DianaGaleM, Dinoguy2, Dj Capricorn, Donarreiskoffer, Dr.Bastedo, Dragon
Helm, Duncan, Dyanega, Dysmorodrepanis, EEye, Ecphora, EdJohnston, Entnahme, Erianna, Espoo, Fanghong, Fatapatate, Faustnh, Fedor, Figma, FireBrandon, Fredrik, Fui in terra aliena,
Furrykef, Gadfium, Gaurav, Gcm, Gdr, Gdvorsky, Geoff, GerardM, Ggriffit1, Gimme danger, Gioto, Good Olfactory, Graminophile, Grouchy Chris, Gunnar Mikalsen Kvifte, HJJHolm,
HalfShadow, Hamamelis, Harry R, HorsePunchKid, Hrmaham, Hughcharlesparker, Hurmata, Ian mccarthy, Infomuse, Invertzoo, Ioverka, Iridescent, Ish ishwar, J. Spencer, Jaknouse, Jeffpw,
JerryFriedman, JerrySteal, Jfraatz, JoJan, John of Reading, JohnCD, Johnuniq, JonHarder, Josh Grosse, Julesd, Just Another Dan, K, Ke4roh, Kembangraps, Kencf0618, KiloByte, Kiwiboy1221,
Knnwill, Kosigrim, Kralizec!, Lexor, Ligulem, LilyCylinder, Littenberg, LittleHow, Littlealien182, M, Mariachi2324, Mark t young, Marshman, Mav, Mdhowe, Mercury543210,
Metamagician3000, Mgiganteus1, Michael Hardy, MichaelSH, Mike Dillon, Mr. Blackout, MrDarwin, MrDolomite, Müslimix, Nakon, Nandreeson, Nbarth, Neutrality, Nicke L, NickelShoe,
Nishkid64, NoahElhardt, Noleander, Oblivious, Olivier, Omegatron, Oxymoron83, PAvdK, Paalexan, ParlorGames, Pasquale, Patrick0Moran, Paul Richter, Peak, Pen-pen, Peter coxhead,
PeterMSimons, Petter Bøckman, Philcha, Pigsonthewing, Pizza1512, Plantsurfer, Plumpurple, Polinizador, Popnose, PrestonH, Quizkajer, RG2, RJO, Raul654, Rich Farmbrough, Richard001,
Rillian, Rintrah, Rjanag, Rjwilmsi, Robert1947, Safay, Samir, Samsara, Scbomber, Seglea, Shao, Sheep81, Sidhekin, SilkTork, SimonGreenhill, Sjschen, Sjö, Slrubenstein, Smith609, Snek01,
Sobreira, SpankDatAzz, Squids and Chips, Stemonitis, Stephen C. Carlson, Stephenchou0722, Strobilomyces, Surachit, Susurrus, Syp, TUF-KAT, Tarquin, TestPilot, The Braz, The Thing That
Should Not Be, Themfromspace, Themusicgod1, Theresa knott, TimVickers, Tjunier, Tmkeesey, Tom Schmal, Townmouse, Trabucogold, Treisijs, Tremello22, Tualha, Utcursch, UtherSRG,
Valich, Vanished user, VeryVerily, Vishnava, Visionholder, Vsmith, WadeSimMiser, WereSpielChequers, Wickey-nl, Will Beback Auto, Wordbuilder, YK Times, Zvika, 220 anonymous edits

Cladogram  Source: http://en.wikipedia.org/w/index.php?oldid=387836487  Contributors: ArkinAardvark, Damian Yerrick, Earrnz, Koavf, Shanes, SilkTork, Snek01, 8 anonymous edits

Molecular phylogenetics  Source: http://en.wikipedia.org/w/index.php?oldid=377909149  Contributors: 168..., Aranae, Biophys, Brya, Carlosp420, Dysmorodrepanis, EdJohnston, Eugene van
der Pijll, Extremophile, Florentino floro, Fratrep, Genypholy, Herbm, Igodard, JForget, JoJan, Joseph Solis in Australia, Kingdon, Lexor, M1ss1ontomars2k4, Mario1952, Marj Tiefert, Onco p53,
PierreAbbat, Radagast83, Ragesoss, RoRo, Samsara, Seglea, Shyamal, Stemonitis, StephenWeber, Styrofoam1994, Themfromspace, Tide rolls, Touchstone42, True Pagan Warrior, Vanished
User 1004, 27 anonymous edits

Evolutionary developmental biology  Source: http://en.wikipedia.org/w/index.php?oldid=391298611  Contributors: 10outof10die, APH, Adam Retchless, Adoniscik, AdultSwim, Alamowit,
Alteripse, Antoni Barau, Bookuser, CHW100, Cholling, Clicketyclack, Cohesion, Courcelles, Culmination, Dave souza, DavidLevinson, Dcljr, Ecobion, Ernestfax, Fama Clamosa, Frostus,
Gabbe, Gauravm1312, GetAgrippa, Gongoozler123, Ian Pitchford, Insanity Incarnate, JWSchmidt, Jacek FH, JackWasey, Jknabe, Johnuniq, Karmosin, Katefan0, Kevin Forsyth, Lauranrg,
Leptictidium, Lexor, Lightmouse, LittleHow, Mat8989, Mav, Memestream, Miaers, Mike Dillon, Mindmatrix, Moosepuggle, Naddy, Narayanese, Niteowlneils, Nmg20, Ospalh, Outriggr, Pekaje,
PierreAbbat, Pjvpjv, Rich Farmbrough, Rmarquezp, Roland Deschain, Roosme, Samsara, Shyamal, Sitearm, Slrubenstein, StN, Stevertigo, Template namespace initialisation script, Vanished
User 0001, Vary, Wdanwatts, Wikipeditor, William R. Buckley, Woohookitty, Wotnow, Zundark, 59 anonymous edits

Molecular evolution  Source: http://en.wikipedia.org/w/index.php?oldid=392407939  Contributors: 10outof10die, 168..., A.bit, AdamRetchless, Alan Liefting, Aranae, Aunt Entropy, AxelBoldt,
Borgx, Bornhj, Darth Ag.Ent, Debresser, Duncharris, Emw, Etxrge, Eugene van der Pijll, Ewen, GSlicer, Gaius Cornelius, GeoMor, Johnuniq, Josiahtimy, Kosigrim, Lexor, Lindosland, M stone,
MER-C, Marooned Morlock, Mcw1139, Neutrality, Nonsuch, Northfox, Notreallydavid, OnBeyondZebrax, Owenman, PDH, PhDP, Ragesoss, Rigadoun, Rjwilmsi, Ryulong, Sadi Carnot,
Samsara, Sebastiano venturi, Seglea, Shyamal, Steinsky, Stirling Newberry, StormBlade, Swpb, Template namespace initialisation script, That Guy, From That Show!, The Anome, Theuser,
Thue, Tide rolls, Timwi, Vanished User 0001, Vsmith, Wavesmikey, Whatiguana, 54 anonymous edits

Human evolution  Source: http://en.wikipedia.org/w/index.php?oldid=393080483  Contributors: !1029qpwoalskzmxn, 04carrolld, 168..., 2over0, 4444hhhh, 999powell, A robustus, A8UDI,
ABF, Acaeton, Addshore, Aeon1006, Afronathan, Agathman, Ahimsa xrqhd, Aidan Elliott-McCrea, Ainlina, Airplaneman, Ak1255, Al-Zaidi, Alan Liefting, Alan Peakall, Alansohn, Albedo,
Alex543211, Alexius08, AlienHook, Alpha Quadrant (alt), Amorymeltzer, Anabus, Anburnett, Ancheta Wis, Andersmusician, Andre Engels, AndriyK, Animum, Anlace, AnonMoos, Antandrus,
Antelan, Anthon.Eff, Anthonyjameswood, Antiuser, Arctic.gnome, Arfn24, ArglebargleIV, Arkuat, Arnold90, Arnon Chaffin, Arny, AshLin, Atarr, Atif.t2, Atl braves, Attilios, Aua,
AubreyEllenShomo, Auno3, Aunt Entropy, Autonova, Aviv007, Aymatth2, B jonas, BD2412, BG, BMF81, BaNkR17, Babylonian Armor, Badams5115, Ballinchad15, Banno, BarretBonden,
Bassbonerocks, Bcasterline, Bdb484, Beland, Belizefan, Belthil, Bender235, Benhocking, BerndH, Betacommand, Beyazid, Bfinn, Bhawthorne, Bigtimepeace, Bikeable, BlaiseFEgan,
BlastOButter42, Blue98, Bluecurtis, Bluefrog67, BlytheG, Bmeirose, BobKawanaka, Bobby D. Bryant, Bobo192, Boing! said Zebedee, Bongwarrior, Bookandcoffee, Borgx, Brazucs, Brentt,
BrettAllen, BrianGV, Brianlucas, Bryan Derksen, BryanEkers, Bubbha, Buddho, Buritdd, Bussech, CDN99, Calliopejen1, Caltas, CalumH93, Calypso, Camw, Can't sleep, clown will eat me,
Canadian-Bacon, Captain-tucker, Captinhippie, CardinalDan, Carolmooredc, Casito, Castjean, Cfortunato, Chakazul, Chamaeleon, Chandrax, Chanting Fox, CharlotteWebb, Chase me ladies, I'm
Article Sources and Contributors 450

the Cavalry, Cheesemancheeseman, Cheryl dennison, Chris 73, Chris goulet, Chriskl, Chrislk02, Chrissmith22, Ckatz, Clasqm, Claudelepoisson, Clicketyclack, Cmart1, Cmyers, Cometstyles,
CommonsDelinker, Concerning, ConfuciusOrnis, ConservativeChristian, Conversion script, Couloir007, Cptmurdok, Cquan, Crohnie, Ctbolt, Cybercobra, Cyrius, DARTH SIDIOUS 2, DDek,
DFS454, DHBoggs, DRTllbrg, DVD R W, Da monster under your bed, DanMS, Daniel.Cardenas, Danski14, DarkKunai, Darkchaos556, Darklilac, Das Baz, Dave souza, David Pro, Davril2020,
Daweirdo911, Dawn Bard, Daycd, Dbachmann, Dbrodbeck, Delldot, Denny, Der Falke, DerHexer, Derekt75, Deus Ex Machina, Diego Grez, Digthepast, Dinesh.malshe, Dionyseus,
Discospinster, Dmarquard, Dmyersturnbull, Doc Tropics, DocWatson42, Dogposter, DoktorDec, Don231194, DopefishJustin, DougsTech, Dr. Norris, Drbreznjev, Drc79, Dreamyshade,
DrunkDriver333, Drur93, Duncan.france, Duncharris, Dupz, Dustinasby, Dysepsion, EPM, Ed Poor, Edivorce, Efnar, El C, Elassint, Eleanor J Miller, Emc2, Emijrp, Ems57fcva, Engleaugen666,
Enlil Ninlil, Epastore, Epbr123, Epf, Eric-Wester, Esanchez7587, Eu.stefan, Everyking, EvilFlyingMonkey, Excirial, Exxxs, F13nd, Fabartus, Falcon8765, Fama Clamosa, Fang 23, Fastfission,
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Fredbauder, FreeThinker09, FreplySpang, Fryed-peach, Ftjrwrites, Fui in terra aliena, Funhistory, Fæ, G worroll, GRider, GSlicer, Ga13be, Gabbe, Gaia Octavia Agrippa, Gaia1CB3, Gary King,
Gdr, Gensanders, Geoff, Geologyguy, Ghelae, Gilgameshfuel, Gilliam, Gimme danger, Gimmetrow, Gladysvale, Glenn, Gogo Dodo, GoldenXuniversity, GordonUS, Graham87,
GreatWhiteNortherner, Greensburger, Greenwraith, Gregchapman, GreyCat, Grigri, Grouf, Grundle2600, Guettarda, Gurch, Guslacerda, Gzkn, Gökhan, Hairhorn, Hairy Dude, HalJor, Hanjabba,
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JForget, JFreeman, JNW, Ja 62, Jackaranga, Jackollie, Jaguar, Jagz, Jamalj03, James pic, Jamesontai, Jason Potter, JayJasper, Jayantanth, Jcw69, Jebus989, Jeeny, Jeremyloveshistory, Jidliqz,
JimVC3, Jlrobertson, Jlujan69, Jmcc150, JoanneB, Joed6829, Johanmathiesen, John Abbe, John Wilkins, Johnuniq, Jonathan Hall, Jor, Jordgubbe, Jorvik, Joscquin, Joseph Solis in Australia,
Josephjordania, Josh Grosse, Josh Parris, Jossi, Josue arnold, Joy, Joymmart, Jpgordon, Jrockley, Juliancolton, Jæs, Ka Faraq Gatri, Kaiwen1, Kariteh, Karl Dickman, Karukera, KateH,
Kaylabelle, Kazkaskazkasako, Kazvorpal, Keitei, Kemet, Kevin j, Kevs, KimDabelsteinPetersen, King of the Dancehall, Kingpin13, Kingturtle, Kkrueger, Klingoncowboy4, Kljenni, Knowledge
Seeker, Koavf, Kosigrim, Kotiwalo, Kotuku33, Kpjas, Kubigula, Kuimov, Kukini, Kuru, Kurykh, Kusunose, Kzzl, LA2, La Fuente, La goutte de pluie, Lala357, Larry_Sanger, Leadwind,
Leafyplant, Lemmey, Lemonflash, Lexicon, Lexor, Liftarn, Lighthead, LilDice, Lincspoacher, Little Mountain 5, LittleHow, LizardJr8, Loquacious conundrum, Lord Patrick, Lord Pistachio,
Lorenzo Braschi, Lottamiata, Ludovika26, LuisFagundes, Lynn Wilbur, M3taphysical, MBisanz, MER-C, MFNickster, MK8, Mac Davis, Maelnuneb, Magister Mathematicae, Maldek, Malo,
Mangostar, Mapetite526, Marc Verhaegen, Marcus MacGregor, Margareta, Maristoddard, Markunator, Martin Breheny, Martin451, Masonrose, Master Jay, Master Scott Hall, Matau,
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Evolutionary psychology  Source: http://en.wikipedia.org/w/index.php?oldid=389004714  Contributors: 2004-12-29T22:45Z, Adhib, Adoniscik, Alan Peakall, Alansohn, Allinthebrain, Andonic,
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Creation–evolution controversy  Source: http://en.wikipedia.org/w/index.php?oldid=392083460  Contributors: -Ril-, .:., 5 albert square, A vivid dreamer, A. Parrot, A8UDI, ABF, ABlake,
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Article Sources and Contributors 451

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Objections to evolution  Source: http://en.wikipedia.org/w/index.php?oldid=392192847  Contributors: 2over0, ADude, Aaker, Adriancurrier, Adriansrfr, Agamemnon2, Agathman, Alan
Liefting, Alex.rosenheim, American Eagle, Anarchangel, AndrewWTaylor, Another Stickler, Anupam, Apokryltaros, Apologian, Armchair info guy, Art LaPella, Artichoker, Ashnard, Aunt
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Creationism  Source: http://en.wikipedia.org/w/index.php?oldid=392955936  Contributors: -Midorihana-, 100110100, 129.128.164.xxx, 144.132.75.xxx, 14ledzeppelin, 1rachelkanter,
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JackH, Jager3333, Jagged 85, Jakes18, James A Whitson, Jamesgibbon, Jandalhandler, Jaranda, Jason Potter, Jaxl, Jc4901, Jdvelasc, Jed 20012, Jeff G., Jefffire, JeremyA, Jesse Viviano, Jezmck,
Jfg284, Jgarth, Jim62sch, Jimfbleak, Jimput, Jin, Jiohdi, Jiy, Jmcc150, Joe Kress, Joe1978, Johann Wolfgang, John, John Broughton, John Fader, John of Reading, Johnleemk, Johnor, Johnstone,
Johntex, Johnuniq, Jointquest, Jok2000, Joker828, JokersWild1, Jokestress, Jonzim, Jose Ramos, JosephCCampana, Joshbuddy, JoshuaZ, Jossi, Jpeob, Jpgordon, Jpittman, Jprw, Jtkiefer, Jtneill,
Jujutacular, Jules.lt, Jumbo Snails, JustSomeKid, Justin Eiler, Jwbaumann, Jwissick, JzG, K, K-UNIT, Kaldari, Kalense, Karada, KarlFrei, Karuna8, Kasreyn, Kazrak, Kazvorpal, Kbdank71,
Kcarson, Kdouglaslee, Keith-h, Kelly Martin, Kevin B12, Kevinccc, Kf4bdy, Khukri, KillerChihuahua, KimvdLinde, King of Hearts, Kingpin13, Kirill Lokshin, KnightLago, Knowledge Seeker,
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Leremyus, LexCorp, Lexor, Life, Liberty, Property, Liftarn, Lightdarkness, Lightmouse, Ligulem, LilHelpa, Lilwik, Linas, LinkinPark, Liontherock, Lithfo, LittleOldMe, Littlealien182,
Logophile, Loodog, Lookie Louis, Lordsong, Lordvolton, Ludwigs2, LukeSurl, Luna Santin, Luokehao, M, M1rtyn, M2K 2, MAD, MEGOP, MER-C, MONGO, Macarion, Macguysoft, Mad
Scientist, Madman, Magioladitis, Magister Mathematicae, Magnus Manske, Mahjongg, Mailer diablo, Mainstreetmark, Majorly, Makaristos, Malc82, Malcolm Farmer, Malcolmchurch, Mallocks,
Malo, Mange01, Mann jess, Margareta, Mark Foskey, Mark Musante, MarkGallagher, Markaci, Markbassett, Markbruder, Markburton, Marshill, Marskell, Martin Hinks, MartinHarper, Mathfan,
Matilda, MattShepherd, Matthew Gibson, Matthew Stannard, Matthu999, Mav, Mawest217, Mayalld, Mazin07, McGrupp10799, McKay, Measure, MegaMind, Mego'brien, Mehandas, Mel Etitis,
Melly42, Mentifisto, Merzul, Methcub, Metzenberg, Mglg, Mholland, Micah Fitch, Michael Devore, Michael Hardy, Michael Johnson, Michaelas10, MickWest, Micov, Midnight Gardener,
Mikael Häggström, Mike.m, MikeWren, Mikker, Mildly Mad, Millahnna, Mindmatrix, Minna Sora no Shita, Mirage GSM, Mirlen, MisfitToys, Misonzeng, MisterSheik, Mjb, Mk270,
Article Sources and Contributors 453

Mkmcconn, Mlm42, Mloclam901, Mm40, Mo0, Modemac, Mojoe1185, Molas, Molerat, Monkeyman, Monkeyspangler, Moriori, Morphh, Morwen, MosheZadka, Moxy, Mr Adequate, Mr
Christopher, Mr. Billion, Mr. Lefty, MrPeabody, Mrt23498, Mswake, Mtdeeley, Mulp, MuncherOfSpleens, Munnin, Murfquake82, Murilo, Myles325a, Myork, Mysteryboi4u, N4nojohn, NJM,
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Notinasnaid, Nowimnthing, Nsoonhui, Nstott, NuclearWarfare, NuclearWinner, Nufy8, Nurban, Nuttycoconut, Nv8200p, Nydas, Nyenyec, Octavabasso, Odd nature, Ohnoitsjamie, OldakQuill,
Oliphaunt, Olivier, Omegatron, OmerT, Omicronpersei8, Omphaloscope, One-dimensional Tangent, Orangemarlin, Orderinchaos, Orthologist, Osbus, Osculate, Ospalh, Ossworks, Ott, Ottava
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Patstuart, Patton123, Paul A. Newman, Paul August, Paul Stansifer, Paul rembrandt, Pcarbonn, PeR, Pediainsight, Peedrag, Peripitus, Persian Poet Gal, Peruvianllama, Pete.tian, Peter, Peter M
Dodge, Peter Menke, PeterGrecian, Petesmiles, Petrafan007, Petral, Petral-1, Petri Krohn, Pgan002, Pgecaj, Pgk, PhDP, Phaedriel, PhilKnight, Philip J. Rayment, PhilipO, PiCo, Pigman,
Pilotguy, Piotrus, Pitcdbf, Pithecusson, Pjrm, PlantEvolBioGuy, Plazak, Plumbago, Plunge, Politepunk, Pollinator, Polsmeth, Poor Yorick, Popeofdope420, Portillo, Princeofexcess,
Privatemusings, Prkastoria, Professor marginalia, Profg, PromX1, Psy guy, Psychohistorian, Pudor, Punctilius, Purplefeltangel, Pyrospirit, Quietmarc, Quizkajer, Quokkapox, R. Baley, R. fiend,
R6144, RK, Radiant chains, Ragesoss, Rahulb64, RainbowOfLight, Rakwiki, Ramdrake, Random account 47, Raspor, Raul654, Ravenswood, Rbj, Rbones, Rc brooks, Rcarlberg, Rd232,
Rdrabik, Rdsmith4, RebelChrysanthemum, RedMC, Rednblu, Redrocket, Reedy, Refreshments, Reginmund, Reidgeo, Reinis, Reject, Retired username, RexNL, Reywas92, Rhobite, Rholton,
Rich Farmbrough, Richard Arthur Norton (1958- ), Richard001, RickReinckens, Rickyrab, Rictus, Rjcflyer@aol.com, Rje, Rjwilmsi, Rlsheehan, Rmky87, Rnt20, Robben salter, Robbrown,
Robert Merkel, Robert Stevens, RobertG, Robuddha, Roger4911, Roland Deschain, Rolinator, Ronabop, Rootxploit, Rory096, Rossnixon, Rotem Dan, Rothacisms, Rothery, Rousseau, RoyBoy,
Royalguard11, Royboycrashfan, Rpspeck, Rracecarr, Rrburke, Rriss, Rtc, RucasHost, Rufus843, Rumping, Ruslik0, RussBlau, RxS, RyanParis, Ryguasu, SCEhardt, SDY, SJP, SMesser,
Sabre23t, Sad mouse, Saksjn, SallyForth123, Sam Hocevar, Sam Korn, Samsara, Samuell, Sander Säde, SandyGeorgia, Sannse, Sardanaphalus, Savidan, Sceptre, Scetoaux, Schama, Schapel,
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rabbit, Sillygrin, Silverback, Simoes, Simpletoremember, Singletoned, Sj, Sjschen, Sjö, Skye.houston, Skyraider7, Slicing, Slicky, SlimVirgin, Slrubenstein, Smack, Smadmead, Smartse,
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harrison, Tomandlu, Tomlillis, Tony Avedon, Tony Fox, Tony Sidaway, Tony1, Topbanana, Treisijs, Tretten, TreveX, Trevor MacInnis, Trilemma, Trilobite, Triops, Trishm, Triwbe, Truthandi,
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Unbehagen, Uncle Dick, Ungtss, UnicornTapestry, UninvitedCompany, Unitvm, Unknown, Unyoyega, Uogl, VFHwebdev, Vague Rant, Vanished User 0001, Vanished User 4517, Vanished
user, Vanished user 03, Vapour, Variable, Vecrumba, Veinor, Venske, Vesal, Vicki Rosenzweig, Videmus Omnia, Vinson L Watkins, Voln, VorpalBlade, Voulouza, Vranak, Vsmith, W8IMP,
WAS 4.250, WJBscribe, WLU, WTucker, Wafulz, Waninge, Warpsmith, Wasabe3543, Wasell, Wassupwestcoast, Watgap, Wavelength, Wayward, Wdanwatts, Wdavies, We66er,
Webpendragon, Wee Jimmy, WeezerGeek182, Wereon, Wesley, Wesley R. Elsberry, Whatjesusdoforyou, Whirlicane, White Wolf, Whoistheroach, Whoutz, Wiki alf, Wikidudeman,
Wikignizable, Wikipediarules2221, Wikipediatoperfection, Wikitumnus, Wikiwikibangbang, Wikroach, Wildemoi, Wildspell, Will231, William2233, WilsonjrWikipedia, Wimt, Wing Nut,
Wisco, Wisdom89, Wknight94, Wmarkham, Wolfrock, Womentime, Wookipedia, Wren337, Wshun, Www.jpfo.org, Wyorunner, Xabian40409, XerKibard, Xerxesnine, Xiahou, Xianxxx,
Xstreeem, Xyzzy n, Y0u, Yamamoto Ichiro, Yath, Year 2144, YellowMonkey, Yidisheryid, Yobol, Yopienso, Yqbd, Yserarau, Yumyumpuppies, ZS, Zandperl, Zargulon, Zaslav, ZayZayEM,
Zeke pbuh, Zelmerszoetrop, ZeroOne, Zginder, Zleitzen, Zscout370, Zsinj, Zzuuzz, Zzxc, 2391 anonymous edits

Social effect of evolutionary theory  Source: http://en.wikipedia.org/w/index.php?oldid=391190096  Contributors: 10outof10die, AdamRetchless, Agamemnon2, Airminded, Alan Liefting,
Anupam, Apokryltaros, Arctic.gnome, Aunt Entropy, Black Falcon, Cerebellum, Charles Matthews, Ciroa, Cmdrjameson, ConfuciusOrnis, Cosmic Latte, Cyde, Darklilac, Dave souza, Deepraine,
Donarreiskoffer, Duncharris, Ec5618, Ed Poor, Erik Daniel P, FD Johnston, Fastfission, FeloniousMonk, Filll, Fubar Obfusco, Gimme danger, Grutter, Headbomb, Hillman, J Milburn,
Jacob1207, Johnuniq, JoshuaZ, KillerChihuahua, Lacarnean, Laurence Boyce, Leinad-Z, Lexor, LilHelpa, Markjoseph125, Millosh, Mqduck, Nick Number, Nikodemos, Northfox, Patstuart,
Piotrus, Portillo, RoyBoy, Samsara, Search4Lancer, Simpsons contributor, SonOfNothing, Sovietbill9989, SpacemanAfrica, Steinsky, Stevertigo, TheIncredibleEdibleOompaLoompa, Thialfi,
Vanished user, WikiDao, Wikisk8r, 46 anonymous edits
Image Sources, Licenses and Contributors 454

Image Sources, Licenses and Contributors

Image:Tyrannosaurus BW.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Tyrannosaurus_BW.jpg  License: Creative Commons Attribution 2.5  Contributors: User:ArthurWeasley
Image:Age-of-Man-wiki.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Age-of-Man-wiki.jpg  License: Public Domain  Contributors: Original uploader was Kosigrim at
en.wikipedia
file:Charles_Darwin_by_G._Richmond.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Charles_Darwin_by_G._Richmond.jpg  License: Public Domain  Contributors:
ArséniureDeGallium, Blurpeace, Kilom691, Marco Cristo, Tohma, 3 anonymous edits
file:Haeckel Orchidae.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Haeckel_Orchidae.jpg  License: Public Domain  Contributors: BerndH, Dysmorodrepanis, Orchi, Pengo,
Ragesoss
Image:Glyptodon-Armadillo.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Glyptodon-Armadillo.jpg  License: unknown  Contributors: User:Sadi Carnot
Image:Aquila spinogaster (African Hawk Eagle).jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Aquila_spinogaster_(African_Hawk_Eagle).jpg  License: Creative Commons
Attribution 2.0  Contributors: Steve Jurvetson
Image:Square-townsend-fledermaus.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Square-townsend-fledermaus.jpg  License: GNU Free Documentation License  Contributors:
Original uploader was Velho at en.wikipedia
Image:DNA Overview.png  Source: http://en.wikipedia.org/w/index.php?title=File:DNA_Overview.png  License: GNU Free Documentation License  Contributors: User:Mstroeck
Image:IMG013biglittledogFX wb.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:IMG013biglittledogFX_wb.jpg  License: GNU Free Documentation License  Contributors:
User:ToB
Image:Aulonocara jacobfreibergi RB3.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Aulonocara_jacobfreibergi_RB3.jpg  License: GNU Free Documentation License
 Contributors: User:Radomil
Image:James Hutton.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:James_Hutton.jpg  License: Public Domain  Contributors: Flominator, Svdmolen, Woudloper, 3 anonymous
edits
Image:Stephen Jay Gould (by Kathy Chapman).jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Stephen_Jay_Gould_(by_Kathy_Chapman).jpg  License: Creative Commons
Attribution 3.0  Contributors: w:en:Kathy ChapmanKathy Chapman online
Image:Richard dawkins.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Richard_dawkins.jpg  License: Creative Commons Attribution-Sharealike 2.0  Contributors: Matti Á
File:Charles Darwin aged 51 crop.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Charles_Darwin_aged_51_crop.jpg  License: Public Domain  Contributors: User:Dave souza
File:ADN static.png  Source: http://en.wikipedia.org/w/index.php?title=File:ADN_static.png  License: Public Domain  Contributors: User:Brian0918
File:Gene-duplication.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Gene-duplication.svg  License: Public Domain  Contributors: User:K. Aainsqatsi
file:Biston.betularia.7200.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Biston.betularia.7200.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: Kilom691,
Olei
file:Biston.betularia.f.carbonaria.7209.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Biston.betularia.f.carbonaria.7209.jpg  License: Creative Commons Attribution-Sharealike 2.5
 Contributors: Kilom691, Olei
File:Lion waiting in Nambia.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Lion_waiting_in_Nambia.jpg  License: Creative Commons Attribution 2.0  Contributors: yaaaay
File:Mutation and selection diagram.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Mutation_and_selection_diagram.svg  License: GNU Free Documentation License
 Contributors: User:Elembis
File:Selection Types Chart.png  Source: http://en.wikipedia.org/w/index.php?title=File:Selection_Types_Chart.png  License: Creative Commons Attribution-Sharealike 3.0  Contributors:
User:Azcolvin429
File:Allele-frequency.png  Source: http://en.wikipedia.org/w/index.php?title=File:Allele-frequency.png  License: GNU Free Documentation License  Contributors: Original uploader was Esurnir
at en.wikipedia
File:Whale skeleton.png  Source: http://en.wikipedia.org/w/index.php?title=File:Whale_skeleton.png  License: Public Domain  Contributors: Meyers Konversionlexikon
File:Thamnophis sirtalis sirtalis Wooster.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Thamnophis_sirtalis_sirtalis_Wooster.jpg  License: Public Domain  Contributors:
User:Wilson44691
File:Speciation modes edit.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Speciation_modes_edit.svg  License: Public Domain  Contributors: User:Ilmari Karonen
File:Darwin's finches.jpeg  Source: http://en.wikipedia.org/w/index.php?title=File:Darwin's_finches.jpeg  License: Public Domain  Contributors: John Gould (14.Sep.1804 - 3.Feb.1881)
File:Palais de la Decouverte Tyrannosaurus rex p1050042.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Palais_de_la_Decouverte_Tyrannosaurus_rex_p1050042.jpg  License:
GNU Free Documentation License  Contributors: User:David.Monniaux
File:Ape skeletons.png  Source: http://en.wikipedia.org/w/index.php?title=File:Ape_skeletons.png  License: Public Domain  Contributors: Original uploader was TimVickers at en.wikipedia
Image:Collapsed_tree_labels_simplified.png  Source: http://en.wikipedia.org/w/index.php?title=File:Collapsed_tree_labels_simplified.png  License: Public Domain  Contributors: Original
uploader was TimVickers at en.wikipedia
File:Darwin ape.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Darwin_ape.jpg  License: Public Domain  Contributors: Unknown, The Hornet is no longer in publication and it is
very likely for a 20-year-old artist in 1871 to have died before 1939
Image:Liposome.png  Source: http://en.wikipedia.org/w/index.php?title=File:Liposome.png  License: Public Domain  Contributors: User:Philcha
Image:Stromatolites in Sharkbay.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Stromatolites_in_Sharkbay.jpg  License: GNU Free Documentation License  Contributors: Paul
Harrison
Image:Slime mold solves maze.png  Source: http://en.wikipedia.org/w/index.php?title=File:Slime_mold_solves_maze.png  License: Public Domain  Contributors: User:Philcha
Image:Horodyskia per Fedonkin 2003.png  Source: http://en.wikipedia.org/w/index.php?title=File:Horodyskia_per_Fedonkin_2003.png  License: Public Domain  Contributors: User:Philcha
Image:Opabinia BW2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Opabinia_BW2.jpg  License: Creative Commons Attribution 3.0  Contributors: User:ArthurWeasley
Image:Acanthodes BW.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Acanthodes_BW.jpg  License: Creative Commons Attribution 3.0  Contributors: User:ArthurWeasley
File:Lichen.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Lichen.jpg  License: GNU Free Documentation License  Contributors: Farbenfreude, Millifolium
Image:Cooksonia pertoni.png  Source: http://en.wikipedia.org/w/index.php?title=File:Cooksonia_pertoni.png  License: Creative Commons Attribution 3.0  Contributors: User:Smith609
Image:Gilboa.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Gilboa.jpg  License: Public Domain  Contributors: DragonFire1024, Ies, Kevmin, Philcha
Image:Acanthostega BW.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Acanthostega_BW.jpg  License: Creative Commons Attribution 2.5  Contributors: User:ArthurWeasley
Image:Termite cathedral mounds in a bushfire blackened tropical savanna.jpg  Source:
http://en.wikipedia.org/w/index.php?title=File:Termite_cathedral_mounds_in_a_bushfire_blackened_tropical_savanna.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors:
Photo by and ©2002 Dustin M. Ramsey (Kralizec!)
Image:Extinction intensity.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Extinction_intensity.svg  License: GNU Free Documentation License  Contributors: Beland, Dragons
flight, Geoffrey.landis, Patrick, Smith609, TomCatX, Wst
Image:Phanerozoic biodiversity blank 01.png  Source: http://en.wikipedia.org/w/index.php?title=File:Phanerozoic_biodiversity_blank_01.png  License: GNU Free Documentation License
 Contributors: User:Philcha
Image:Eopraptor sketch5.png  Source: http://en.wikipedia.org/w/index.php?title=File:Eopraptor_sketch5.png  License: unknown  Contributors: -
File:Tree of life by Haeckel.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Tree_of_life_by_Haeckel.jpg  License: Public Domain  Contributors: Ernst Haeckel
File:Sanzio 01 Plato Aristotle.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Sanzio_01_Plato_Aristotle.jpg  License: Public Domain  Contributors: Beria, Bibi Saint-Pol,
G.dallorto, Jacobolus, Kentin, Mattes, MonteChristof, Tomisti, Wutsje, 5 anonymous edits
File:Great Chain of Being 2.png  Source: http://en.wikipedia.org/w/index.php?title=File:Great_Chain_of_Being_2.png  License: Public Domain  Contributors: Didacus Valades (Diego Valades)
File:BelonBirdSkel.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:BelonBirdSkel.jpg  License: Public Domain  Contributors: L C Miall
Image Sources, Licenses and Contributors 455

File:Owen geologic timescale.png  Source: http://en.wikipedia.org/w/index.php?title=File:Owen_geologic_timescale.png  License: Public Domain  Contributors: Original uploader was
TimVickers at en.wikipedia
File:Vestiges dev diag.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Vestiges_dev_diag.jpg  License: Public Domain  Contributors: Robert Chambers
File:Vertebrate archetype.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Vertebrate_archetype.jpg  License: Public Domain  Contributors: Richard Owen
File:Darwins first tree.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Darwins_first_tree.jpg  License: Public Domain  Contributors: Charles Darwin
File:Marsh Huxley horse.png  Source: http://en.wikipedia.org/w/index.php?title=File:Marsh_Huxley_horse.png  License: Public Domain  Contributors: Original uploader was TimVickers at
en.wikipedia
File:Huxley - Mans Place in Nature.png  Source: http://en.wikipedia.org/w/index.php?title=File:Huxley_-_Mans_Place_in_Nature.png  License: Public Domain  Contributors: Original uploader
was TimVickers at en.wikipedia
File:Titanothere Osborn.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Titanothere_Osborn.jpg  License: unknown  Contributors: Henry Fairfield Osborn
File:Sexlinked inheritance white.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Sexlinked_inheritance_white.jpg  License: Public Domain  Contributors: User:Electric goat
File:CollapsedtreeLabels-simplified.svg  Source: http://en.wikipedia.org/w/index.php?title=File:CollapsedtreeLabels-simplified.svg  License: Public Domain  Contributors: Original uploader
was User:TimVickers, SVG conversion by User:User_A1. Original uploader was User A1 at en.wikipedia
Image:Jean-baptiste lamarck2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Jean-baptiste_lamarck2.jpg  License: GNU Free Documentation License  Contributors:
User:Valérie75
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File:Origin of Species title page.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Origin_of_Species_title_page.jpg  License: Public Domain  Contributors: Aleator, Alex6122,
Aristeas, Ben Tillman, Fastfission, Gveret Tered, Inductiveload, Jappalang, Juiced lemon, Ragesoss, 5 anonymous edits
File:Charles Darwin seated.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Charles_Darwin_seated.jpg  License: Public Domain  Contributors: w:Henry MaullHenry Maull
(1829–1914) and w:John FoxJohn Fox (1832–1907) (Maull & Fox) UNIQ-ref-0-7337d7d7159c63fb-QINU
File:Georges Cuvier - Elephant jaw.png  Source: http://en.wikipedia.org/w/index.php?title=File:Georges_Cuvier_-_Elephant_jaw.png  License: Public Domain  Contributors:
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File:Darwin tree.png  Source: http://en.wikipedia.org/w/index.php?title=File:Darwin_tree.png  License: Public Domain  Contributors: Charles Darwin
File:Charles Darwin - Pigeon skulls.png  Source: http://en.wikipedia.org/w/index.php?title=File:Charles_Darwin_-_Pigeon_skulls.png  License: Public Domain  Contributors: Charles Darwin
and Francis Darwin
File:Alfred Russel Wallace 1862 - Project Gutenberg eText 15997.png  Source:
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File:Asa Gray (1867).jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Asa_Gray_(1867).jpg  License: Public Domain  Contributors: Jappalang
File:Image-Rhea Darwinii1.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Image-Rhea_Darwinii1.jpg  License: Public Domain  Contributors: John Gould
File:Darwin divergence.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Darwin_divergence.jpg  License: Public Domain  Contributors: User:Alexei Kouprianov
File:Huxley - Mans Place in Nature.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Huxley_-_Mans_Place_in_Nature.jpg  License: Public Domain  Contributors: w:Benjamin
Waterhouse HawkinsBenjamin Waterhouse Hawkins (1807–94)
File:Pedigree of man (Haeckel 1874).jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Pedigree_of_man_(Haeckel_1874).jpg  License: Public Domain  Contributors: E Haeckel
(1834–1919)
File:Rev Baden Powell.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Rev_Baden_Powell.jpg  License: Public Domain  Contributors: Hartmann
Image:Charles Darwin by Julia Margaret Cameron 2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Charles_Darwin_by_Julia_Margaret_Cameron_2.jpg  License: Public
Domain  Contributors: User:Davepape
Image:Darwin ape.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Darwin_ape.jpg  License: Public Domain  Contributors: Unknown, The Hornet is no longer in publication and it is
very likely for a 20-year-old artist in 1871 to have died before 1939
Image:Structure of Evolutionary Biology.png  Source: http://en.wikipedia.org/w/index.php?title=File:Structure_of_Evolutionary_Biology.png  License: Creative Commons
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File:Phylogenetic tree.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Phylogenetic_tree.svg  License: unknown  Contributors: User:Sting
Image:Brassica oleracea0.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Brassica_oleracea0.jpg  License: GNU Free Documentation License  Contributors: Ies, Lamiot, MPF
Image:Darwin's finches.jpeg  Source: http://en.wikipedia.org/w/index.php?title=File:Darwin's_finches.jpeg  License: Public Domain  Contributors: John Gould (14.Sep.1804 - 3.Feb.1881)
Image:HMS Beagle by Conrad Martens.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:HMS_Beagle_by_Conrad_Martens.jpg  License: Public Domain  Contributors: Conrad
Martens (1801 - 21 August 1878)
Image:Chromosome2 merge.png  Source: http://en.wikipedia.org/w/index.php?title=File:Chromosome2_merge.png  License: Public Domain  Contributors: Original uploader was Evercat at
en.wikipedia
file:Evolution pl.png  Source: http://en.wikipedia.org/w/index.php?title=File:Evolution_pl.png  License: unknown  Contributors: Original uploader was Mcy jerry at en.wikipedia
file:Saurischian & Ornithischian pelvis bone modification w- selected species of Dinosauria.png  Source:
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file:Evolution insect mouthparts color.png  Source: http://en.wikipedia.org/w/index.php?title=File:Evolution_insect_mouthparts_color.png  License: GNU Free Documentation License
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File:GiraffaRecurrEn.svg  Source: http://en.wikipedia.org/w/index.php?title=File:GiraffaRecurrEn.svg  License: Creative Commons Attribution-Sharealike 2.0  Contributors: User:Drbug
File:Route of vas deferens from testis to the penis.png  Source: http://en.wikipedia.org/w/index.php?title=File:Route_of_vas_deferens_from_testis_to_the_penis.png  License: GNU Free
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Image:Resin with insect (aka).jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Resin_with_insect_(aka).jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors:
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Image:Asaphiscuswheelerii.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Asaphiscuswheelerii.jpg  License: GNU Free Documentation License  Contributors: DanielCD, Glenn,
Kevmin, Saperaud
file:Glyptodon-1.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Glyptodon-1.jpg  License: GNU Free Documentation License  Contributors: Albasmalko, DaB., Haplochromis,
Hunadam, Kevmin, LadyofHats, Tolanor
file:Armadillo.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Armadillo.jpg  License: Public Domain  Contributors: Boivie, Common Good, Nordelch, Pfctdayelise, 3 anonymous
edits
Image:Cynognathus BW.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Cynognathus_BW.jpg  License: Creative Commons Attribution 2.5  Contributors: User:ArthurWeasley
Image:Horseevolution.png  Source: http://en.wikipedia.org/w/index.php?title=File:Horseevolution.png  License: GNU Free Documentation License  Contributors: Original uploader was Mcy
jerry at en.wikipedia Later version(s) were uploaded by Obli at en.wikipedia.
file:Camelid migration & evolution DymaxionMap 01.png  Source: http://en.wikipedia.org/w/index.php?title=File:Camelid_migration_&_evolution_DymaxionMap_01.png  License: GNU
Free Documentation License  Contributors: User:Azcolvin429, User:Mcy jerry
file:Pangaea Glossopteris.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Pangaea_Glossopteris.jpg  License: Public Domain  Contributors: User:Petter Bøckman
file:Marsupial biogeography present day - dymaxion map.png  Source: http://en.wikipedia.org/w/index.php?title=File:Marsupial_biogeography_present_day_-_dymaxion_map.png  License:
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Image:Drosophila melanogaster - side (aka).jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Drosophila_melanogaster_-_side_(aka).jpg  License: Creative Commons
Attribution-Sharealike 2.5  Contributors: user:Aka
Image:Arabidopsis thaliana.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Arabidopsis_thaliana.jpg  License: GNU Free Documentation License  Contributors: User:Roepers
Image Sources, Licenses and Contributors 456

Image:Tragopogon porrifolius flower.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Tragopogon_porrifolius_flower.jpg  License: GNU Free Documentation License
 Contributors: Ayacop, Quadell
Image:Jean-Baptiste Lamarck.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Jean-Baptiste_Lamarck.jpg  License: Public Domain  Contributors: User:Duesentrieb
File:Plumpollen0060.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Plumpollen0060.jpg  License: GNU Free Documentation License  Contributors: Aphaia, ComputerHotline,
Duesentrieb, Ghouston, Maksim, Quadell, Satyrium
File:Bee PD foto explained1.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Bee_PD_foto_explained1.jpg  License: Public Domain  Contributors: ComputerHotline, Dixi, Maksim,
Quadell, Satyrium, Wst, Xhienne, Überraschungsbilder, 1 anonymous edits
File:Carnica bee on sedum telephium.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Carnica_bee_on_sedum_telephium.jpg  License: Creative Commons Attribution 2.5
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Image:Wasp mimicry.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Wasp_mimicry.jpg  License: Creative Commons Attribution 2.5  Contributors: Image Credit: (A, C, E, and F)
by Rob Knell; (B and D) by Tom Ings
Image:Pfau imponierend.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Pfau_imponierend.jpg  License: GNU Free Documentation License  Contributors: User:BS Thurner Hof
File:Random sampling genetic drift.gif  Source: http://en.wikipedia.org/w/index.php?title=File:Random_sampling_genetic_drift.gif  License: Creative Commons Attribution-Sharealike 3.0
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File:Random genetic drift chart.png  Source: http://en.wikipedia.org/w/index.php?title=File:Random_genetic_drift_chart.png  License: Creative Commons Attribution-Sharealike 3.0
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File:Population bottleneck.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Population_bottleneck.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors:
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File:Founder effect with drift.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Founder_effect_with_drift.jpg  License: GNU Free Documentation License  Contributors:
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Image:Portulaca grandiflora mutant1.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Portulaca_grandiflora_mutant1.jpg  License: Creative Commons Attribution-Sharealike 3.0
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Image:Benzopyrene DNA adduct 1JDG.png  Source: http://en.wikipedia.org/w/index.php?title=File:Benzopyrene_DNA_adduct_1JDG.png  License: GNU Free Documentation License
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File:Chromosomes mutations-en.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Chromosomes_mutations-en.svg  License: Public Domain  Contributors: YassineMrabet
File:Notable mutations.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Notable_mutations.svg  License: Public Domain  Contributors: User:Mikael Häggström
Image:Life cycle of a sexually reproducing organism.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Life_cycle_of_a_sexually_reproducing_organism.svg  License: Public Domain
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Image:Antibiotic resistance.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Antibiotic_resistance.svg  License: Public Domain  Contributors: User:Wykis
Image:Pavo cristatus albino001xx.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Pavo_cristatus_albino001xx.jpg  License: GNU Free Documentation License  Contributors:
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Image:Polydactyly 01 Lhand AP.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Polydactyly_01_Lhand_AP.jpg  License: GNU Free Documentation License  Contributors: ,
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Image:Charles Darwin aged 51.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Charles_Darwin_aged_51.jpg  License: Public Domain  Contributors: Diwas, Fastfission,
Infrogmation, Kurpfalzbilder.de, Ragesoss, Ryz, Sandpiper, 5 anonymous edits
Image:Gasterosteus aculeatus.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Gasterosteus_aculeatus.jpg  License: unknown  Contributors: Bob Burkhardt, Siebrand, Visviva
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File:Drosophila speciation experiment.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Drosophila_speciation_experiment.svg  License: Public Domain  Contributors: User:BenB4,
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File:Phylogenetic-Groups.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Phylogenetic-Groups.svg  License: Public Domain  Contributors: Original uploader was TotoBaggins at
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File:Haeckel arbol bn.png  Source: http://en.wikipedia.org/w/index.php?title=File:Haeckel_arbol_bn.png  License: Public Domain  Contributors: User:Luis_Fernández_García
File:Clade types.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Clade_types.svg  License: unknown  Contributors: User:Surachit
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File:Cladogram-example1.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Cladogram-example1.svg  License: Creative Commons Attribution-Sharealike 2.5  Contributors:
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File:E1b1a ancestry.png  Source: http://en.wikipedia.org/w/index.php?title=File:E1b1a_ancestry.png  License: Public Domain  Contributors: User:Muntuwandi, User:Pdeitiker
File:Identical cladograms.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Identical_cladograms.svg  License: Creative Commons Attribution-Sharealike 2.5  Contributors:
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Image:Cladistics-Apomorphy.png  Source: http://en.wikipedia.org/w/index.php?title=File:Cladistics-Apomorphy.png  License: Creative Commons Attribution 3.0  Contributors: User:Faustnh
Image:Simple cladistics.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Simple_cladistics.svg  License: GNU Free Documentation License  Contributors: User:Adam Cuerden,
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File:Notharctus tenebrosus AMNH.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Notharctus_tenebrosus_AMNH.jpg  License: Creative Commons Attribution-Sharealike 2.0
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File:Proconsul skeleton reconstitution (University of Zurich).JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Proconsul_skeleton_reconstitution_(University_of_Zurich).JPG
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Image:Humanevolutionchart.png  Source: http://en.wikipedia.org/w/index.php?title=File:Humanevolutionchart.png  License: unknown  Contributors: Reed DL, Smith VS, Hammond SL,
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File:Ferrassie skull.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ferrassie_skull.jpg  License: Creative Commons Attribution 2.5  Contributors: User:120
File:Canto tallado 2-Guelmim-Es Semara.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Canto_tallado_2-Guelmim-Es_Semara.jpg  License: Public Domain  Contributors:
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File:Small bonfire.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Small_bonfire.JPG  License: Creative Commons Attribution-Sharealike 3.0  Contributors: User:Kenneth Hawes
File:Biface (France).jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Biface_(France).jpg  License: Creative Commons Attribution 3.0  Contributors: User:DocteurCosmos
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Image:Lorenz and Tinbergen1.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Lorenz_and_Tinbergen1.jpg  License: GNU Free Documentation License  Contributors: Max Planck
Gesellschaft
File:Scopes trial.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Scopes_trial.jpg  License: unknown  Contributors: Unknown
File:The Creation of Adam.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:The_Creation_of_Adam.jpg  License: Public Domain  Contributors: Barosaul, David Levy, G.dallorto,
Mattes, Nard the Bard, PFHLai, PxMa, Sailko, 1 anonymous edits
File:Ambulocetus BW.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ambulocetus_BW.jpg  License: Creative Commons Attribution 3.0  Contributors: User:ArthurWeasley
File:Views on Evolution.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Views_on_Evolution.svg  License: unknown  Contributors: User:Pbroks13
Image Sources, Licenses and Contributors 457

Image:Charles Darwin 1880.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Charles_Darwin_1880.jpg  License: Public Domain  Contributors: w:Elliott & FryElliott & Fry
Image:Caricatura de Darwin.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Caricatura_de_Darwin.jpg  License: Public Domain  Contributors: Derek Ross, Juiced lemon, Lobo,
Mu, Sanbec, Wolfmann, 1 anonymous edits
Image:Archaeopteryx-model.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Archaeopteryx-model.jpg  License: GNU Free Documentation License  Contributors:
Archaeopteryxdino, Dinoguy2, Dudo, Juiced lemon, Kevmin, Preto(m), Rooivalk, TomCatX, Vmenkov, 2 anonymous edits
Image:Haeckel drawings.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Haeckel_drawings.jpg  License: Public Domain  Contributors: Romanes, G. J.
Image:WilliamPaley.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:WilliamPaley.jpg  License: Public Domain  Contributors: Original uploader was Sir Paul at en.wikipedia
File:Flagellum base diagram en.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Flagellum_base_diagram_en.svg  License: Public Domain  Contributors: User:LadyofHats
Image:Huxley - Mans Place in Nature.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Huxley_-_Mans_Place_in_Nature.jpg  License: Public Domain  Contributors: w:Benjamin
Waterhouse HawkinsBenjamin Waterhouse Hawkins (1807–94)
Image:Creationist car.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Creationist_car.jpg  License: Creative Commons Attribution-Sharealike 2.0  Contributors: Dodo, Karppinen,
OSX, Para, Pixel ;-), Richard001
File:Truth fish.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Truth_fish.jpg  License: Public Domain  Contributors: Original uploader was Ungtss at en.wikipedia
File:Plato_Silanion_Musei_Capitolini_MC1377.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Plato_Silanion_Musei_Capitolini_MC1377.jpg  License: Creative Commons
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FeloniousMonk, Hrafn, J Milburn, John, K, Melesse, Odd nature, Peripitus, Skier Dude, SnowFire, Vanished user 03, Videmus Omnia
File:Pandas text analysis.png  Source: http://en.wikipedia.org/w/index.php?title=File:Pandas_text_analysis.png  License: Public Domain  Contributors: User:TimVickers
Image:MichaelBehe.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:MichaelBehe.jpg  License: GNU Free Documentation License  Contributors: Campus Photo • Bryan Matluk
Image:Dembski head shot.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Dembski_head_shot.jpg  License: Creative Commons Attribution 2.5  Contributors: Original uploader was
Kenosis at en.wikipedia
Image:The Creation of Adam.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:The_Creation_of_Adam.jpg  License: Public Domain  Contributors: Barosaul, David Levy, G.dallorto,
Mattes, Nard the Bard, PFHLai, PxMa, Sailko, 1 anonymous edits
License 458

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