On the Origin of Species, written by Charles Robert Darwin and published in November 1859, is the most defining and important book in evolutionary biology. In this book, Darwin argued that different forms of life could change over time, under the influence of natural (and artificial) selection. He backed up his arguments with examples and evidence that he collected during his global scientific expedition in the 1830s. How did a seemingly ordinary beetle-collecting student come to develop such an important idea?
The Voyage Of The Beagle
When Darwin first went on board the Beagle, he had an orthodox view of life on earth. He did not go looking for evidence to support evolution. He started the journey with the firm belief that species were fixed entities. But Darwin had an open and inquisitive mind, he was able to make clear observations and interpret them in an unbiased and evidence-based manner.
Darwin made three key observations that made him cast his doubts on the view that species were fixed:
i. The continuity of species through history.
Darwin found fossils from some extinct armadillos in southern America. The skeletons were much larger in size than those of the existing ones; however, much of the construction was similar. Intrigued by this, Darwin realised that the armadillo species must have changed over time.
ii. The geological specificity of species.
When Darwin was travelling across the great grasslands in southern America, he noticed that different regions along the geological landscape were occupied by similar species of ostrich with certain small differences. He thought of the possibility of species differentiating and developing according to geological differences.
iii. Evidence from the Archipelagos.
Darwin compared the species found on the Archipelago of Cape Verde with those found on Galapagos. While the two Archipelagos were similar in terms of environment and geological landscape, the respective wildlife were drastically different. From a creationist’s point of view this seemed strange: if two environments were similar then God should have created similar species to put into them. Darwin speculated that species on the Archipelago of Cape Verde came from the near-by African continent, but this was not the case for the wildlife on the distant Galapagos Islands, thus accounting for the observed phenomenon.
Evolution By Natural Selection
In 1837, a year after the return of H.M.S. Beagle, Darwin started to formulate his thoughts on the idea of evolution. In March, he was told by the ornithologist John Gould that the finches found on seven islands of Galapagos differed from one another on a specific level. At this point, Darwin was finally sure that geological separation played a very important part in the formation of new species: in different environments, species changed gradually over time in different ways to adapt to the local environment.
In October 1838, Darwin read The Principle of Population by Thomas Malthus, apparently ‘for fun’. Malthus suggested that there was an unlimited potential for the population of a species to grow. However, limited resources meant that there should be a struggle of existence between members of a population. Darwin saw that this should apply to populations of any living organism. Individuals in a species differed from one another and these differences could affect the ability of individuals to survive, and/or to reproduce. If, in ‘the struggle of existence’, a certain variant gave its carriers an advantage in survival and reproduction over others, then the carriers would be able to have more offspring.
Therefore, the mutations and characteristics carried would be passed on to more offspring, and so would therefore become more prevalent. On the other hand, less fit individuals would not be able to survive long enough to reproduce and pass on their mutations and characteristics. Thus, they would eventually become extinct. This is the idea of natural selection as the mechanism by which species change gradually over time: they evolve.
Find out more about how evolution occurs in the evolution section.
The Reception Of The Origin
The publishing of The Origin introduced a revolutionary and ground-breaking concept but how did the scientific world and the public react? Find out more.
Written by Henry Li
References & Further Reading
Almost Like a Whale
by Steve Jones, Doubleday: 1999
The Autobiography of Charles Darwin
by Charles Darwin (Edited by Francis Darwin), The Thinker's Library: 1929
Darwin
by John van Wyhe, Andre Deutsch: 2009
Darwin
by Adrian Desmond & James Moore, Penguin: 1991
Darwin: Discovering the Tree of Life
by Niles Eldredge, WW Norton & Co.: 2005
On the Origin of Species
by Charles Darwin, 1859 (any reprint - 2nd edition preferable)
Evolution
by Carl Zimmer, Arrow: 2003
Evolution
by Mark Ridley, Wiley Blackwell: 2003
Evolution
by Nick arton, Derek Briggs & Jonathan Eisen, Cold Spring Harbour: 2007
One Long Argument
by Ernst Mayr, Allen Lane: 1991
What Evolution Is
by Ernst Mayr, Phoenix: 2002
Why Evolution is True
by Jerry Coyne, OUP: 2009