Theory Of Evolution By Natural And Sexual Selection
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
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