FREE ESSAY ON THEORY OF EVOLUTION

THEORY OF EVOLUTION

CHARLES DARWIN AND THE THEORY OF EVOLUTION 
It is commonly thought today that the theory of evolution originated from Darwin in the 
nineteenth century. However, the idea that species mutate over time has been around for
a long 
time in one form or another. Therefore, by Darwin's time the idea that species change
from one 
type into another was by no means new, but was rejected by most because the
proponents of 
evolution could not come up with a satisfactory mechanism that would explain this
change.
The most influential evolutionary theories prior to Darwin were those of Lamarck and 
Geoffroy St. Hilaire, developed between 1794 and 1830. Lamarck suggested that species
evolve 
through the use or disuse of particular organs. In the classic example a giraffe that
stretches its 
neck slightly to reach higher leaves will gain in neck length, and this small gain would
be
passed 
on to its offspring. Geoffroy, on the other hand suggested that the change was
discontinuous, 
large in magnitude, and occurred at the production of offspring. However, these theories
of 
evolution were based on a priori explanations that offered no demonstrated mechanism. 
Darwin's theory of evolution differs in that it is based on three easily verified
observations. 
First, individuals within a species vary from one another in morphology, physiology, and

behavior. Second, variation is in some part heritable so that variant forms have
offspring
that 
resemble them. Third, different variants leave different number of offspring. Darwin than

proceeded to elaborate on the mechanism of evolution by suggesting that in the universal
struggle 
for life, nature selects those individuals who are best suited (fittest) for the
struggle, and
these 
individuals in turn reproduce more than those who are less fit, thus changing the
composition of 
the population. In addition to natural selection, Darwin also suggested that species
also
evolve 
through the complementary process of sexual selection. According to Darwin, in sexual
selection, 
one gender of a species develops a preference for individuals of the other gender who
possess 
certain features. The individuals who possess these features will than have a
reproductive 
advantage over others, resulting in a greater number of offspring, and thus, again, a
change in the 
composition of the population. Therefore, it was Darwin who made the theory of evolution

feasible by providing the mechanisms of natural and sexual selection. 
Darwin's Formative Years 
Charles Darwin was born in England in 1809 and belonged to a wealthy and respectable 
family. His grandfather, Erasamus Darwin, was a noted botanical expert in his day who
published 
two important books, Zoonomia, and the Botanic Garden. In these books, Erasamus
speculated 
about various evolutionary ideas that were dismissed as too radical (i.e., the nose of
the
swine has 
become hard for the purpose of turning up the soil in search of insects and roots).
Darwin
who in 
his youth read his grandfather's books with admiration, later commented that his
grandfather 
anticipated the views and erroneous grounds of opinion of Lamarck. Nevertheless,
Erasamus 
may have unconsciously influenced Darwin in preparing the way for evolution by natural 
selection. 
In 1818, at the age of 9, Darwin entered the Shrewsbury school, which was ran by Dr.
Butler. 
Darwin later recalled that nothing could have been worse for the development of my mind
than 
Dr. Butler's school, as it was strictly classical, nothing else being taught , except a
little
ancient 
geography and history. The school as a means of education to me was simply a blank. He
was 
removed from the school in 1825, and was sent to Edinburgh to study medicine. There he
studied 
for two years before deciding that he didn't like medicine. But before he left Edinburgh,
he
was 
introduced for the first time to the theories of Lamarck. According to Darwin at the time
he
was 
not very impressed with Lamarck's ideas. In 1828, at his father's suggestion, Darwin
entered 
Christ's College in Cambridge to become a clergyman. To Darwin a good education meant 
instruction in the methods and logic of thought. Therefore, Just about the only thing he
enjoyed 
studying there was Paley's works on theology, because of their logic. For the rest,
however, he 
judged Cambridge to be just as much a waste of time as Edinburgh and Shrewsbury. 
Nevertheless, in his spare time at Cambridge, Darwin became interested in various
scientific 
endeavors, and became acquainted with and influenced by the scientific ideas of Henslow,

Sedgwick, and Whewell (ironically Sedgwick later became a bitter opponent of Darwin's
theory). In addition, during his last year at Cambridge Darwin read two books which
influenced him greatly, Herschel's Preliminary Discourse on the Study of Natural
Philosophy, and Von 
Humboldt's Personal Narrative of Travels to the Equinoctial Regions of the New Continent.

Darwin later confessed that these books inspired in him a burning zeal to add even the
most 
humble contribution to the noble structure of Natural Science. 
In 1831 Darwin graduated from Cambridge, and as he was pondering his future he
received a 
proposal to join a scientific expedition that would survey the southern coast of Tierra
del
Fuego. 
Darwin accepted the proposal, and sailed from England aboard the famed Beagle on
December, 
27, 1831. His job was to collect and catalogue new species so that they could be sent
back
for 
further research in England. It is commonly thought that Darwin used the voyage to test
his 
theory of evolution, but this is highly unlikely. At the time Darwin's interests were
purely 
geological as can be seen by his correspondence with his sister. For instance, writing
about the 
fossils which he discovered he said, All the interest which I individually feel about
these
fossils 
is their connection with the geology of the Pampas. Furthermore, Darwin himself
confessed that he could not have appreciated the significance of his findings while on
the
voyage, because he 
lacked the necessary training in dissection and drawing as well as the knowledge of
comparative 
anatomy. It was only much later when Darwin returned from the voyage, and when the
fossils 
were identified by Owen, that Darwin began to examine them as zoological, rather then 
geological, phenomena. 
The voyage turned out to be very productive for Darwin, who upon his return in 1836
began to work on the conversion of the diary, which he kept during the voyage, into a
journal suitable for publication. The Journal was first published in 1839 under the
title
Journal and Remarks, as 
Volume III of the Narrative of the Surveying Voyages of H.M.S. Adventures and Beagle. 
However, enough people thought that Darwin's work was sufficiently important to warrant
a 
separate publication, and in 1845 a second edition was published under the name Journal
of 
Research into the Natural History and Geology of the Countries Visited during the Voyage
of 
(H.M.S. Beagle Round the World (henceforth referred to as the Journal). Darwin Discovers
Evolution 
It appears to be that only sometime in 1837 did Darwin first start to entertain the idea
of 
evolution seriously. The proof for this lies in the notebook which he kept from July 1837
to 
February 1838. In particular, the following statement from the notebook provides valuable

insight: In July opened first notebook on transmutation of species. Had been greatly
struck 
from about the previous March on character of South American fossils, and species of
Galapagos 
Archipelago. These facts (especially latter), origin of all my views. Therefore, it must
have
been 
at this time that Darwin's ideas took this turn. Furthermore, had the change occurred
earlier, it 
would have shown up in Darwin's writings in the Journal, which, more than half completed
by 
March, shows no trace of it. Overall, with the notable exception of the idea of natural
selection, 
most of what Darwin later wrote in On the Origin of Species by Means of Natural
Selection, or 
the preservation of Favoured Races in the Struggle for Life (henceforth referred to as
the
Origin), 
was already sketched in that notebook. It is important to note that Darwin's thinking at
this
point was still distinctly teleological in character. He still believed that God had
instituted
the laws governing reproduction to maintain species in a state of perfect adaptation to
their environment. Only after his full appreciation of the struggle for existence did he
come
to believe that a changed environment disturbs growth to produce random variation. 
Curiously, Darwin asserts that in originating his theory of evolution he was trying to
follow 
Baconian principles, that is collect facts before theorizing. Specifically, in his
autobiography
he 
states After my return to England it appeared to me that by following the example of
Lyell
in 
Geology, and by collecting all facts which bore in any way on the variation of animals
and
plants 
under domestication and nature, some light might perhaps be thrown on the whole
subject. My 
first notebook was opened in July 1837. I worked on true Baconian principles, and
without
any 
theory collected facts on a wholesale scalea. However, as his notebooks of the time amply

demonstrate, he was speculating boldly from the very beginning in favor of evolution. In

addition, Darwin himself at other times admitted his dislike for the Baconian method. For

instance in one of his correspondences he wrote How odd it is that any one should not
see that 
all observation must be for or against some view if it is to be of any service. And
elsewhere, 
No one could be a good observer unless he was an active theologian. Therefore, a more 
accurate description of his method would be, inventing a theory and seeing how many
classes of 
facts the theory could explain. Darwin Discovers Natural Selection During his early
theorizing Darwin was fixated upon the whys of evolution. He contemplated such questions
as Why is life short ? Why does the individual die, and why do species die ? Why does
nature put so high a premium on generation ? And why does generation have the twofold
character of perpetuation and variation. It seems that apart from the occasional
reference
to adaptation, Darwin ,at that time, almost deliberately tried to avoid the contemporary
theories of the mechanics of evolution. 
Notwithstanding, Darwin, sooner or later, had to confront the question of how evolution 
occurred. Amusingly, he happened to stumble upon the answer quite accidentally. In his
spare 
time Darwin enjoyed reading various books rather aimlessly, for amusement. One of these
books, 
which he read in October 1838, happened to be Malthus' Essay on the Principle of
Population. 
As Darwin himself later related, Malthus' description of the struggle for existence in
human
society immediately suggested to him that under the competitive conditions of animal and
plant 
life, favorable variations would tend to be preserved, and unfavorable ones destroyed,
the
result 
being the formation of new species. By this chance encounter than, Darwin's theory was 
provided with a rationale, and the how of evolution came to supplement the why. 
It is important to note, that even though the crux of Darwin's theory was inspired by
Malthus, Darwin diverged from Malthus in a critical way. Darwin's debt to Malthus lies
in
the borrowing of the concept of the struggle for existence. However, in general, what
Malthus was concerned about was not how the struggle for existence affected the quality
of the population (i.e., he did not suggest that in the struggle for existence the
strong
survive and the weak perish) but simply how it limited its numbers. Indeed, Malthus'
essay
was written as a rebuttal to Godwin and Condorcet, both of whom had argued that
humans, under conditions of equality, were capable of infinite progress and perfection.
In
the essay Malthus advanced the principle of population to refute that idea. Thus,
Malthus'
principle argued that human society could never progress toward perfectibility because
the
population inevitably tends to increase beyond the means of subsistence and is kept
within
the bounds of its resources only by misery, vice, and moral restraint. 
Malthus' principle of population was based on the supposed differences in reproduction
rates 
between humans (who because of their status as top dog in the animal kingdom
reproduced 
geometrically) and animals and plants (who could only increase arithmetically, because
they 
served mankind as a means of sustenance). Darwin by contrast, shifted the center of
attention 
from humans to the animal and plant kingdoms, because he was impressed by their
enormous 
natural fertility, which was kept in check only by their own limited means of sustenance.
By
shifting his perspective from mankind to animals and plants Darwin revealed the basic
fallacy of 
Malthus' argument. For if humans increased geometrically, animals and plants must also
increase at the same rate, and perhaps even more, because overall their natural rate of
reproduction is higher than that of mankind. Therefore, the struggle for existence,
which
to Malthus meant that hardship and misery were the defining features of human life, to
Darwin meant that every species was in constant change, because nature favored the
fittest through the process of natural selection. 
Writing the Origin 
Three and a half years have passed since Darwin read Malthus in October 1838 before he 
finally sat down to write his ideas formally in May 1842. There are two main reasons for
this 
lengthy delay. First, throughout his life Darwin suffered from ill-health , which began
to get
acute 
in 1837, and was particularly debilitating between 1838 and 1842. Second, during this
time
Darwin had more pressing matters to attend to. In particular he was working on the book
Coral 
Reefs, papers for the Geological society, and work connected with the Zoology of the
voyage of 
the Beagle. 
After completing the initial first sketch of 35 pages, he set out to write a larger and
more
thrall 
sketch in 1844 (by the time he was finished the sketch numbered 230 pages). However,
Darwin 
still proceeded to write his ideas on evolution at a leisurely pace, and not until 1856,
when 
urged by his colleague Lyell, did he start working on his magnum opus, the Origin. By
June
1858 
Darwin had completed about half of the book (on a scale three to four times as large as
when it 
was later published), when one day a nasty surprise awaited him. 
On June 18, Darwin received a manuscript from the English naturalist Wallace. In the 
manuscript Wallace described the theory of natural selection, and asked Darwin to
comment on 
his ideas. Darwin thought that the only honorable thing to do was to recommend the paper
for 
publication. Fortunately, for Darwin, Lyell suggested (and Wallace and Darwin accepted)
that 
both Wallace's paper and extracts from Darwin's sketch of 1844 be published
simultaneously, 
thus establishing the rights of both to priority. Interestingly, later on at the
fiftieth
anniversary 
meeting of their joint publication, Wallace made it clear that although the idea of
natural
selection 
came to both of them independently, Darwin's contributions outweighed his by twenty to
one 
because Darwin had the credit of twenty years of priority and work. 
The impact of the Origin 
Finally, by 1859 Darwin finished writing the book, and on November 24 the Origin was
first
published. The sales of the book exceeded everyone's expectations (by 1876 16,000 copies
were sold in England alone), and the book's impact was felt almost immediately. In the
mid 
nineteenth century English society where science was a popular topic of conversation,
the
book 
competed with such dinner party topics as the Italian revolution. Even those who most
bitterly 
despised its content were quick to concede its importance. 
Within the scientific community the book was creating a new paradigm that threatened to 
disrupt the existing status-quo. The mood of the time is illustrated by August Weismann
who 
states: Darwin's book fell like a bolt from the blue; it was eagerly devoured, and while
it 
excited in the minds of the younger students delight and enthusiasm, it aroused among
the
older 
naturalists anything from cool aversion to violent opposition. The young saw in Darwin an

opportunity for a new and freer philosophical universe. For instance, young biologists
such
as 
Karl Pearson, referring to the beginning of time, were rejoiced when that wretched date
BC 
4004, was replaced by a long vista of millions of years of development. However, the
older
more professional scientists, objected to Darwin's ideas on religious grounds. Before
Darwin 
published the Origin, science and religion existed in harmony. There was an
understanding
on 
the part of religion that evolution was discredited by science. Now that men of science
were 
finally favorites of the church (just two centuries ago scientists such as Galileo were
unfavorably 
perceived by the church), it seemed foolish to give up this hard won peace for just
another
evolutionary hypothesis. 
Sexual Selection 
Although Darwin discussed sexual selection in the Origin, the majority of the book (and
hence 
the primary importance) was devoted to natural selection. However, sexual selection
played a far 
more important role in Darwin's The Descent of Man, and Selection in Relation to Sex 
(henceforth referred to as the Descent), which was published on February 24, 1871. In
the
Descent, sexual selection assumed an equal if not greater than role for the origin of
species. For 
Darwin sexual selection was not simply a subcategory of natural selection, but rather an
alternative or complementary mechanism of evolution. In addition, sexual selection, to a
larger extent than natural selection, shifts the focus of attention to one of the most
significant and least appreciated aspects of Darwin's theory: the location of the
struggle
for existence lies primarily within species rather than between species. It is therefore
inaccurate, from this point on, to refer to Darwin's theory as simply evolution by
natural
selection (Darwin himself called the theory the principle of evolution). 
The primary reason why Darwin abandoned natural selection in favor of sexual selection
was the fact that natural selection could not properly explain either the evolution of
man
from the 
animals or the differences between the sexes and races. The problem is that natural
selection 
assumes that only beneficial changes get preserved in future generations, whereas in
reality the 
races of man differ from each other and from their nearest allies amongst the animals ,
in
certain 
characters which are of no service to them in their ordinary habits of life. By
contrast,
sexual 
selection does not have to be useful for the purpose of adaptation to the environment,
and
it may 
actually work against natural selection. Therefore, Darwin now argued that any features
which are not adaptive to the individual, and thus could not have been acquired through
the process of 
natural selection, must have been acquired through sexual selection. 
The Reaction to the Descent 
When the Descent was published in 1871 it became an immediate best-seller. The initial
2500 
copies were sold almost instantaneously, and an additional 5000 copies were sold by the
end of 
the year. The book was exceedingly controversial at the time, dealing with perhaps the
most 
provocative evolutionary topic of all, the origin of man. In the book Darwin suggested
that
man 
differed from animals in degree and not kind, and than proceeded to conclude that man
descended 
from a hairy, tailed quadruped, probably arboreal in its habits. Surprisingly, the
reaction to
the book was not as violent as one might have expected it to be, from Darwin's previous 
experience with the Origin. For instance, Hooker, who at that time found evolution
discussed 
everywhere relates the following: I dined out three times last weak, and at every table
heard 
evolution talked of as an accepted fact, and the descent of man with calmness. However,
the 
picture painted by Hooker is rather deceptive, as the portrayed amiability was often a
matter of 
tone rather than of substance. People may not have been outraged, but neither were they
placated. 
Most of the critics choose to ridicule Darwin's ideas rather than attack them head on.
For 
example, a typical response, published in the Athenaeum, went along the lines of: No man
will 
ever develop religion out of a dog or Christianity out of a cat. Nevertheless, criticism
was
mostly tempered with praise. A good example of this is provided in the Edinburgh Review
which 
carefully balanced displeasure with tribute: Mr. Darwin appears to us to be not more 
remarkable for the acuteness and ingenuity of his powers of observation of natural
phenomena, 
than he is for the want of logical power and sound reasoning on philosophical questions.

Therefore, while despised by some and adored by others Darwin's ideas were quickly
permeating into the fabric of society. 
Darwin left us a legacy which is greater than just the sum of his scientific work. Not
only
did 
his theory of evolution illuminate our past, but also the present and the future were
now
possible 
to interpret in Darwinian terms. Probably more so than any other scientific theory,
Darwin's 
theory of evolution, lends itself to various social interpretations known as social
Darwinism.
From the radical left to the radical right, Darwin's theory has been adopted by such
people
as 
Marx and Hitler, each of whom saw in it evidence for their own ideology. Alongside the
likes 
of Copernicus, Galileo, and Newton, Darwin has rightly earned his place in history as
one
of 
the giants of the scientific revolution.