Evolution Theory

Charles Robert Darwin (February 12, 1809 – April 19, 1882) was an English naturalist, who realised and demonstrated that all species of life have evolved over time from common ancestors through the process he called natural selection. The fact that evolution occurs became accepted by the scientific community and the general public in his lifetime, while his theory of natural selection came to be widely seen as the primary explanation of the process of evolution in the 1930s, and now forms the basis of modern evolutionary theory. In modified form, Darwin’s scientific discovery remains the foundation of biology, as it provides a unifying logical explanation for the diversity of life.

Darwin developed his interest in natural history while studying medicine at Edinburgh University, then theology at Cambridge. His five-year voyage on the Beagle established him as an eminent geologist whose observations and theories supported Charles Lyell’s uniformitarian ideas, and publication of his journal of the voyage made him famous as a popular author. Puzzled by the geographical distribution of wildlife and fossils he collected on the voyage, Darwin investigated the transmutation of species and conceived his theory of natural selection in 1838. Although he discussed his ideas with several naturalists, he needed time for extensive research and his geological work had priority. He was writing up his theory in 1858 when Alfred Russel Wallace sent him an essay which described the same idea, prompting immediate joint publication of both of their theories.

His 1859 book On the Origin of Species established evolution by common descent as the dominant scientific explanation of diversification in nature. He examined human evolution and sexual selection in The Descent of Man, and Selection in Relation to Sex, followed by The Expression of the Emotions in Man and Animals. His research on plants was published in a series of books, and in his final book, he examined earthworms and their effect on soil.

In recognition of Darwin’s pre-eminence, he was one of only five 19th century UK non-royal personages to be honoured by a state funeral, and was buried in Westminster Abbey, close to John Herschel and Isaac Newton.

The Beagle survey took five years, two-thirds of which Darwin spent on land. He carefully noted a rich variety of geological features, fossils and living organisms, and methodically collected an enormous number of specimens, many of them new to science. At intervals during the voyage he sent specimens to Cambridge together with letters about his findings, and these established his reputation as a naturalist. His extensive detailed notes showed his gift for theorising and formed the basis for his later work. The journal he originally wrote for his family, published as The Voyage of the Beagle, summarises his findings and provides social, political and anthropological insights into the wide range of people he met, both native and colonial.

While on board the ship, Darwin suffered badly from seasickness. In October 1833 he caught a fever in Argentina, and in July 1834, while returning from the Andes down to Valparaíso, he fell ill and spent a month in bed.

Before they set out, FitzRoy gave Darwin the first volume of Charles Lyell’s Principles of Geology, which explained landforms as the outcome of gradual processes over huge periods of time. On their first stop ashore at St Jago, Darwin found that a white band high in the volcanic rock cliffs consisted of baked coral fragments and shells. This matched Lyell’s concept of land slowly rising or falling, giving Darwin a new insight into the geological history of the island which inspired him to think of writing a book on geology. He went on to make many more discoveries, some of them particularly dramatic. He saw stepped plains of shingle and seashells in Patagonia as raised beaches, and after experiencing an earthquake in Chile saw mussel-beds stranded above high tide showing that the land had just been raised. High in the Andes he saw several fossil trees that had grown on a sand beach, with seashells nearby. He theorised that coral atolls form on sinking volcanic mountains, and confirmed this when the Beagle surveyed the Cocos (Keeling) Islands.

During the first year in South America, Darwin made a major find of fossils of huge extinct mammals in strata with modern seashells, indicating recent extinction and no change in climate or signs of catastrophe. They included the little known Megatherium and fragments of armour which he thought looked like giant versions of the armour on local armadillos, as well as unknown species which aroused great interest when they were sent to England. After the voyage Richard Owen showed that most were closely related to living creatures exclusively found in the Americas.


As HMS Beagle surveyed the coasts of South America, Darwin began to theorise about the wonders of nature around him.Lyell’s second volume, which argued against evolutionism and explained species distribution by “centres of creation”, was sent out to Darwin. He puzzled over all he saw, and his ideas went beyond Lyell. In Argentina, he found that two types of rhea had separate but overlapping territories. On the Galápagos Islands he collected birds, and noted that mockingbirds differed depending on which island they came from. He also heard that local Spaniards could tell from their appearance on which island tortoises originated, but thought the creatures had been imported by buccaneers. In Australia, the marsupial rat-kangaroo and the platypus seemed so unusual that Darwin thought it was almost as though two distinct Creators had been at work.

In Cape Town he and FitzRoy met John Herschel, who had recently written to Lyell about that “mystery of mysteries”, the origin of species. When organising his notes on the return journey, Darwin wrote that if his growing suspicions about the mockingbirds, the tortoises and the Falkland Island Fox were correct, “such facts undermine the stability of Species”, then cautiously added “would” before “undermine”. He later wrote that such facts “seemed to me to throw some light on the origin of species”.

Three natives who had been taken from Tierra del Fuego on the Beagle’s previous voyage were taken back there to become missionaries. They had become “civilised” in England over the previous two years, yet their relatives appeared to Darwin to be “miserable, degraded savages”. A year on, the mission had been abandoned and only Jemmy Button spoke with them to say he preferred his harsh previous way of life and did not want to return to England. Because of this experience, Darwin came to think that humans were not as far removed from animals as his friends then believed, and saw differences as relating to cultural advances towards civilisation rather than being racial. He detested the slavery he saw elsewhere in South America, and was saddened by the effects of European settlement on Aborigines in Australia and Maori in New Zealand.

Towards the end of the voyage Captain FitzRoy began writing the official Narrative of the Beagle voyages, and after reading Darwin’s diary he proposed incorporating it into the account. Darwin agreed to rewrite his Journal to provide a separate third volume, on natural history.

By the start of 1856, Darwin was investigating whether eggs and seeds could survive travel across seawater to spread species across oceans. Hooker increasingly doubted the traditional view that species were fixed, but their young friend Thomas Henry Huxley was firmly against evolution. Lyell was intrigued by Darwin’s speculations without realising their extent. When he read a paper by Alfred Russel Wallace on the Introduction of species, he saw similarities with Darwin’s thoughts and urged him to publish to establish precedence. Though Darwin saw no threat, he began work on a short paper. Finding answers to difficult questions held him up repeatedly, and he expanded his plans to a “big book on species” titled Natural Selection. He continued his researches, obtaining information and specimens from naturalists worldwide including Wallace who was working in Borneo. In December 1857, Darwin received a letter from Wallace asking if the book would examine human origins. He responded that he would avoid that subject, “so surrounded with prejudices”, while encouraging Wallace’s theorising and adding that “I go much further than you.”

Darwin’s book was half way when, on 18 June 1858, he received a paper from Wallace describing natural selection. Shocked that he had been “forestalled”, Darwin sent it on to Lyell, as requested, and, though Wallace had not asked for publication, he suggested he would send it to any journal that Wallace chose. His family was in crisis with children in the village dying of scarlet fever, and he put matters in the hands of Lyell and Hooker. They decided on a joint presentation at the Linnean Society on 1 July of On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection; however, Darwin’s baby son died of the scarlet fever and he was too distraught to attend.

There was little immediate attention to this announcement of the theory; after the paper was published in the August journal of the society, it was reprinted in several magazines and there were some reviews and letters, but the president of the Linnean remarked in May 1859 that the year had not been marked by any revolutionary discoveries. Only one review rankled enough for Darwin to recall it later; Professor Samuel Haughton of Dublin claimed that “all that was new in them was false, and what was true was old.” Darwin struggled for thirteen months to produce an abstract of his “big book”, suffering from ill health but getting constant encouragement from his scientific friends. Lyell arranged to have it published by John Murray.

On the Origin of Species by Means of Natural Selection, or The Preservation of Favoured Races in the Struggle for Life (usually abbreviated to On the Origin of Species) proved unexpectedly popular, with the entire stock of 1,250 copies oversubscribed when it went on sale to booksellers on 22 November 1859. In the book, Darwin set out “one long argument” of detailed observations, inferences and consideration of anticipated objections. His only allusion to human evolution was the understatement that “light will be thrown on the origin of man and his history”. His theory is simply stated in the introduction:

As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.

He put a strong case for common descent, but avoided the then controversial term “evolution”, and at the end of the book concluded that;

There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.