MBA Wallah

Batch : PIONEER (CAT)

Subject : Editorial
Topic : Editorial–06

Direction (1–5) : Read the following passage and answer change goes back 151 years – to Darwin himself. In the 6th
the questions that follow: edition of On the Origin of Species, published in 1872, he
acknowledged forms of variations that seemed to arise
(Source: Aeon Essays; Dated: 06/07/2023) spontaneously, without successive, slight modifications: “It
appears that I formerly underrated the frequency and value
Since 1859, when Charles Darwin’s On the Origin of of these latter forms of variation, as leading to permanent
Species was first published, the theory of natural selection modifications of structure independently of natural
has dominated our conceptions of evolution. As Darwin selection.” – from Chapter 15, p395, emphasis added
understood it, natural selection is a slow and gradual process Today, we know in exquisite detail how these larger-scale
that takes place across multiple generations through ‘spontaneous’ variations come about without the
successive random hereditary variations. In the short term, intervention of random mutations. And yet, even in the age
a small variation might confer a slight advantage to an of genome sequencing, many evolutionary scientists still
organism and its offspring, such as a longer beak or better cling stubbornly to a view of evolution fuelled by a gradual
camouflage, allowing it to out-compete similar organisms accumulation of random mutations. They insist on the
lacking that variation. Over longer periods of time, Darwin accuracy of the mid-20th-century ‘updated’ version of
postulated, an accumulation of advantageous variations Darwin’s ideas – the ‘Modern Synthesis’ of Darwinian
might produce more significant novel adaptations – or even evolution (through natural selection) and Mendelian
the emergence of an entirely new species. genetics – and have consistently failed to integrate evidence
Natural selection is not a fast process. It takes place for other genetic processes. As Ernst Mayr, a major figure
gradually through random variations, or ‘mutations’ as we in the Modern Synthesis, wrote in Populations, Species and
call them today, which accumulate over decades, centuries, Evolution (1970): “The proponents of the synthetic theory
or millions of years. Initially, Darwin believed that natural maintain that all evolution is due to the accumulation of
selection was the only process that led to evolution, and he small genetic changes, guided by natural selection, and that
made this explicit in On the Origin of Species: “If it could transpecific evolution [ie, the origins of new species and
be demonstrated that any complex organ existed, which taxonomic groups] is nothing but an extrapolation and
could not possibly have been formed by numerous, magnification of the events that take place within
successive, slight modifications, my theory would populations and species.”
absolutely break down. But I can find out no such case.” This failure to take account of alternative modes of change
A lot has changed since 1859. We now know that Darwin’s has been foundational to popular and scientific
‘gradualist’ view of evolution, exclusively driven by natural misconceptions of evolution. It continues to impact the
selection, is no longer compatible with contemporary study of antibiotic and pesticide resistance, the breeding of
science. It’s not just that random mutations are one of many new crops for agriculture, the mitigation of climate change,
evolutionary processes that produce new species; they have and our understanding of humanity’s impacts on
nothing to do with the major evolutionary transformations biodiversity.
of macroevolution. Species do not emerge from an During the past century, discoveries that have challenged
accumulation of random genetic changes. This has been the gradualist view of evolution have been sidelined,
confirmed by 21st-century genome sequencing, but the idea forgotten, and derided. This includes the work of 20th-
that natural selection inadequately explains evolutionary century geneticists such as Hugo de Vries, one of the
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rediscoverers of Mendelian genetics and the man who gave scientists of the Modern Synthesis simply could not imagine
us the term ‘mutation’, or Richard Goldschmidt, who any other way for hereditary variation to occur besides
distinguished between microevolution (change within a Darwinian gradualism. And so, for more than a century,
species) and macroevolution (changes leading to new natural selection through random mutations has dominated
species). Their findings were ignored or ridiculed to convey public conceptions of evolution.
the message that the gradual accumulation of random Ibecame embroiled in the evolution debates in the 1960s, at
mutations was the only reasonable explanation for the beginning of my life as a scientist. While doing my PhD
evolution. We can see the absence of other perspectives in research, I isolated genetic mutations in E coli bacteria
popular works by Richard Dawkins, such as The Selfish whose properties differed from standard explanations of
Gene (1976), The Extended Phenotype (1982), and The genetic variations at the time. According to molecular
Blind Watchmaker (1986); or in textbooks used in geneticists in 1965, mutations were supposed to take place
universities across the world, such as Evolution (2017) by only in two ways: through errors in DNA replication limited
Douglas Futuyma and Mark Kirkpatrick. However, it’s an to just one or two base pairs, or by deletions of longer
absence that’s particularly conspicuous because alternatives stretches of the genome. I eventually showed that the
to random mutation have not been difficult to find. puzzling mutations I found in E coli were caused by the
One of the most significant of these alternatives is insertion of long segments of genetic material, typically
symbiogenesis, the idea that evolution can operate through more than 1,000 base pairs.
symbiotic relationships rather than through gradual, I wasn’t the only one to come across these long insertions.
successive changes. In the early 20th century, American and Other bacterial geneticists had isolated unusual mutations in
Russian scientists such as Konstantin Mereschkowsky, Ivan different locations in the genome of bacteria, and they
Wallin and Boris Kozo-Polyansky argued that symbiotic turned out to be DNA insertions too. So, in 1976, two
cell fusions had led to the deepest kinds of evolutionary colleagues and I organised the first meeting on DNA
change: the origins of all cells with a nucleus. These insertions. During this meeting, it became clear that
arguments about symbiotic cell fusions, despite being geneticists working on bacteria, yeast, fruit flies, plants and
vigorously championed by the evolutionary biologist Lynn animals were all studying the same phenomenon
Margulis in later years, did not find a place in evolutionary McClintock had discovered in her maize plants 30 years
textbooks until they were confirmed by DNA sequencing at earlier. This realisation would profoundly change the way
the end of the 20th century. And yet, even though these we understood evolution, and it led me to begin thinking of
arguments have now been confirmed, the underlying insertions as important evolutionary tools, rather than
cellular processes of symbiotic cell fusions have still not supposedly harmful ‘junk DNA’ as they were later claimed
been incorporated into mainstream evolutionary theory. to be.
An absence that’s perhaps even harder to explain is why the It was at this 1976 meeting that I first met McClintock. In
pioneering work of the cytogeneticist Barbara McClintock, the early 1930s, she’d discovered that X-rays broke
one of the giants of 20th-century genetics, has not been chromosomes, and that maize could repair the damage by
accepted as posing a viable alternative to dominant theories joining broken ends together. If the rejoined ends came from
of evolution. McClintock won the Nobel Prize in 1983 for the same breakage event, the chromosome was restored to
her discovery during the 1940s of rapid genetic changes in its original configuration, but if those ends came from two
maize plants that were definitely not random – changes different breakage events, the chromosomes were
found not only in maize but, we now know, across all forms restructured. As McClintock delved deeper into
of life. After confirmation by molecular geneticists in the chromosome breakage and repair, she uncovered processes
20th century, discoveries like hers should have inspired a that led to chromosome restructurings and rapid genetic
radical rethinking of evolution. Instead, these ideas were changes in her maize plants. She had discovered
accepted only among a small circle of geneticists. The
 MBA Wallah

biologically mediated genome change, but even more like immune defences, embryonic development, and
startling results lay ahead. viviparous reproduction in mammals.
In 1944, McClintock began mating maize plants with To support his random mutation ideas, Darwin quoted Carl
genomes configured so that both parental pollen and ovule Linnaeus’s dictum ‘Natura non facit saltum’ (nature does
cells contained broken chromosomes. The result of these not make jumps) several times in On the Origin of Species,
experiments created what has been described as ‘a genetic but molecular genetics proved that nature does indeed make
earthquake’ in the fertilised embryos. Many could not jumps in cellular genomes – and they’re not random. Nature
produce viable maize plants, and those that could grow to has invented multiple biochemical mechanisms for those
maturity often exhibited variegated patterns of coloration in jumps to take place.
the stalks, leaves and kernels.
These characteristics were associated with ‘unstable’ 1. Based on the passage, which of the following best
genetic determinants at different sites in the plants’ genome. describes the tone of the author?
McClintock found that unstable loci carried insertions of (a) Sarcastic & satirical
genetic material that were unlike any previously discovered. (b) Populist & applauding
She demonstrated that these ‘controlling elements’, as she (c) Analytical & laudatory
came to call them, had previously been dormant in the (d) Biased & contemptuous
maize genome and were activated in response to ‘genome
shock’ from ongoing cycles of chromosome breakage and 2. Based on the passage, which one of the following is
repair. Controlling elements were not fixed at a specific site a valid argument about the theory of natural
in the chromosomes and, unexpectedly, were able to move selection?
or ‘transpose’ from one place to another in the genome. (a) Due to its violation of the theory of Modern
When they arrived at a new location in the genome, they Synthesis, it can be unequivocally dismissed
could alter the expression of nearby genetic material. This without hesitation.
discovery revealed an entirely new mechanism of genetic (b) The process of natural selection, which occurs
regulation and variability: maize plants were rapidly through hereditary variations, is characterized
changing their own genomes through transposable by its gradual and unhurried nature.
controlling elements (TEs). And moreover, TE changes (c) In contrast, natural selection is a rapid process
were nonrandom in two ways. Firstly, the same DNA that operates through random variations or
element could insert repeatedly at new target sites; and, mutations, contrary to the slow and gradual
secondly, TE mobility and mutagenic activity was activated pace typically associated with it.
by specific organismal stress conditions. (d) It considers for alternative modes of change
Since the 1970s, it became clear that all living organisms, apart from hereditary variations, due to which
from bacteria to plants and animals, use TEs as key the theory of Natural Selection has become
evolutionary tools. There are multiple types of TEs, rendered useless.
including purely DNA-based ‘transposons’ as well as two
different types of ‘retrotransposons’, which use RNA 3. The following statements could be inferred as
intermediates to move to new locations in the genome. supporting the arguments of the passage, EXCEPT:
Every species has its own characteristic content of different (a) Natural selection, being a slow process, occurs
TEs, which can accumulate to very high numbers in the gradually as a result of random variations,
genomes of more complex organisms. The human genome, commonly referred to as 'mutations'.
for example, contains more than 30 times as much TE DNA (b) The study of antibiotic and pesticide resistance
as it does protein-coding DNA. TEs have played a major is significantly affected by the failure to
role in evolving genome systems for complex properties consider alternative modes of change.
 MBA Wallah

(c) Darwin held the belief that natural selection 5. Which one of the following sets of words and
was the sole process responsible for driving the phrases serves best as keywords of the passage?
process of evolution. (a) Charles Darwin, Origin of Species, natural
(d) Contrary to the notion that evolution occurs selection, advantageous variations, adaptations
solely through gradual, successive changes, (b) Natural selection, mutations, macroevolution,
symbiogenesis does not support the idea that species, genetic material
evolution operates through symbiotic (c) Natural Selection, accumulation, Mendelian
relationships. Genetics, Modern Synthesis, symbiogenesis
(d) Transposable controlling elements,
4. Which of the following best describes what the transposons, retrotransposons, genome
passage is trying to do? systems, living organisms
(a) The article delves into the impact of alternative
modes of variations or mutations on our
comprehension of recent findings, specifically
in the study of antibiotic and pesticide
resistance.
(b) It explores how scientific developments have
the potential to challenge theories that were
once regarded as fundamental.
(c) The article examines the argument that natural
selection is no longer relevant in the modern
world, particularly following the emergence of
the theory of symbiogenesis.
(d) The article explores the idea that as time
passed, there was a growing need to upgrade
Darwinism with Neo-Darwinism.
 MBA Wallah

Answer Key
1. (c)
2. (b)
3. (d)
4. (b)
5. (b)
 MBA Wallah

Hints & Solutions

1. (c) And b, ‘The study of antibiotic and pesticide
c reflects the correct tone of the author in the given resistance is significantly affected by the failure to
passage, as the tone is of critical analysis of the consider alternative modes of change’, finds
Darwin’s theory and that of appraisal for the recent inference from Para 6 of the given passage.
scientific developments to counter that theory. c, ‘Darwin held the belief that natural selection was
Hence, c forms the most accurate answer. the sole process responsible for driving the process
The tone of author is not of sarcasm but a close of evolution’, also finds inference from the Para 2.
introspection of the facts presented in the passage, Whereas for d, it is mentioned that “One of the most
thus a can be rejected. significant of these alternatives is symbiogenesis,
b (Populist & applauding) also closely reflects the the idea that evolution can operate through
tone of author, but in the passage, the author symbiotic relationships rather than through gradual,
criticises the popular theory of Natural Selection by successive changes”. Thus, d is contrary to the
Darwin and also those supporting it, in the light of passage and is the answer.
recent developments challenging the same theory.
That’s why, b cannot be the answer. 4. (b)
d does not effectively reflects the tone of the author; b is the most accurate answer as the passage deals
as author doesn’t seem to biased about the Darwin’s with the timeline of how evolution theories were
theory and newer Neo-Darwinism or the rapid modified with the improvement in scientific
changes; but it is more of analytical. Hence d can understanding of concepts.
be rejected. a, also closely reflects the central theme of the
passage but on a closer look, it proves to be narrow
2. (b) and limits to the specificity of mutations to
b is the most suitable answer as it finds inference understand modern concepts only. Hence it can be
from the passage (Para 1) and is the fundamental rejected.
principle of the theory of Natural Selection. c is also too narrow as it only follows the influence
a is an extreme option, as it lists that theory of of symbiogenesis on natural selection. Hence it can
Natural Selection violated the theory of Modern be rejected.
Synthesis, which is not the case as from the passage d is narrow and vague, as passage rejects both
it is clear that theory of Modern Synthesis actually Darwinism & Neo-Darwinism to explain modern
expanded on the concept of natural selection and concepts. Hence it cannot be the answer.
included that changes can also be caused by
transpecific evolution. 5. (b)
c is contrary to the passage and can be rejected as it Here, b is the most accurate answer, as lists the
is mentioned in the passage that natural selection is major keywords reflecting upon the central theme
a slow and gradual process. of the passage.
d is also contrary to the passage as it finds mention that a is too narrow as it only revolves around the theory
natural selection is caused by hereditary variations of natural selection and misses several other
across many generations. Hence it can be rejected. comments made by the author in the passage.
Hence can be rejected.
3. (d) c, although lists the major theories listed by the
While a, b & c find direct inferences from the passage, author in the passage but does not discuss the how
d, on a closer look is contrary to the passage. & why they were modified during the time period.
a, ‘Natural selection, being a slow process, occurs Hence this option cannot be the answer.
gradually as a result of random variations, d is too narrow to be the answer, as it only revolves
commonly referred to as 'mutations'’, finds around the Transposable Elements, mentioned in
inference from Para 2. the passage.

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