Paleontology, sometimes spelled palaeontology, (/ˌpeɪliɒnˈtɒlədʒi, ˌpæli-, -ən-/) is the
scientific study of life that existed prior to, and sometimes including, the start of
the Holocene Epoch (roughly 11,700 years before present). It includes the study of fossils to
determine organisms' evolution and interactions with each other and their environments
(their paleoecology). Paleontological observations have been documented as far back as
the 5th century BC. The science became established in the 18th century as a result
of Georges Cuvier's work on comparative anatomy, and developed rapidly in the
19th century. The term itself originates from Greek παλαιός, palaios, "old, ancient",
ὄν, on (gen. ontos), "being, creature" and λόγος, logos, "speech, thought, study".[1]
Paleontology lies on the border between biology and geology, but differs
from archaeology in that it excludes the study of anatomically modern humans. It now uses
techniques drawn from a wide range of sciences, including biochemistry, mathematics,
and engineering. Use of all these techniques has enabled paleontologists to discover much
of the evolutionary history of life, almost all the way back to when Earth became capable of
supporting life, about 3.8 billion years ago. As knowledge has increased, paleontology has
developed specialised sub-divisions, some of which focus on different types
of fossil organisms while others study ecology and environmental history, such as ancient
climates.
Body fossils and trace fossils are the principal types of evidence about ancient life,
and geochemical evidence has helped to decipher the evolution of life before there were
organisms large enough to leave body fossils. Estimating the dates of these remains is
essential but difficult: sometimes adjacent rock layers allow radiometric dating, which
provides absolute dates that are accurate to within 0.5%, but more often paleontologists
have to rely on relative dating by solving the "jigsaw puzzles"
of biostratigraphy (arrangement of rock layers from youngest to oldest). Classifying ancient
organisms is also difficult, as many do not fit well into the Linnaean taxonomy classifying
living organisms, and paleontologists more often use cladistics to draw up evolutionary
"family trees". The final quarter of the 20th century saw the development of molecular
phylogenetics, which investigates how closely organisms are related by measuring the
similarity of the DNA in their genomes. Molecular phylogenetics has also been used to
estimate the dates when species diverged, but there is controversy about the reliability of
the molecular clock on which such estimates depend.
Contents
1Overview
o 1.1A historical science
o 1.2Related sciences
o 1.3Subdivisions
2Sources of evidence
o 2.1Body fossils
o 2.2Trace fossils
o 2.3Geochemical observations
3Classifying ancient organisms
4Estimating the dates of organisms
5History of life
o 5.1Mass extinctions
6History
7See also
8References
9External links
Overview[edit]
The simplest definition of "paleontology" is "the study of ancient life".[2] The field seeks
information about several aspects of past organisms: "their identity and origin, their
environment and evolution, and what they can tell us about the Earth's organic and
inorganic past".[3]
A historical science[edit]
The preparation of the fossilised bones of Europasaurus holgeri
Paleontology is one of the historical sciences, along
with archaeology, geology, astronomy, cosmology, philology and history itself:[4] it aims to
describe phenomena of the past and reconstruct their causes.[5] Hence it has three main
elements: description of past phenomena; developing a general theory about the causes of
various types of change; and applying those theories to specific facts. [4] When trying to
explain the past, paleontologists and other historical scientists often construct a set of
hypotheses about the causes and then look for a smoking gun, a piece of evidence that
strongly accords with one hypothesis over the others. Sometimes the smoking gun is
discovered by a fortunate accident during other research. For example, the discovery
by Luis and Walter Alvarez of iridium, a mainly extraterrestrial metal, in the Cretaceous–
Tertiary boundary layer made asteroid impact the most favored explanation for
the Cretaceous–Paleogene extinction event, although the contribution of volcanism
continues to be debated.[5]
The other main type of science is experimental science, which is often said to work by
conducting experiments to disprove hypotheses about the workings and causes of natural
phenomena. This approach cannot prove a hypothesis, since some later experiment may
disprove it, but the accumulation of failures to disprove is often compelling evidence in
favor. However, when confronted with totally unexpected phenomena, such as the first
evidence for invisible radiation, experimental scientists often use the same approach as
historical scientists: construct a set of hypotheses about the causes and then look for a
"smoking gun".[5]
