Editing Alfred Russel Wallace (section)

=== Early evolutionary thinking ===
Wallace began his career as a travelling naturalist who already believed in the transmutation of species. The concept had been advocated by [[Jean-Baptiste Lamarck]], [[Étienne Geoffroy Saint-Hilaire|Geoffroy Saint-Hilaire]], [[Erasmus Darwin]], and [[Robert Edmond Grant|Robert Grant]], among others. It was widely discussed, but not generally accepted by leading naturalists, and was considered to have [[radicalism (historical)|radical]], even revolutionary connotations.{{sfn|Larson|2004|p=73}}{{sfn|Bowler|Morus|2005|p=141}} Prominent anatomists and geologists such as [[Georges Cuvier]], [[Richard Owen]], [[Adam Sedgwick]], and Lyell attacked transmutation vigorously.{{sfn|McGowan|2001|pp=101, 154–155}}{{sfn|Larson|2004|pp=23–24, 37–38}} It has been suggested that Wallace accepted the idea of the transmutation of species in part because he was always inclined to favour radical ideas in politics, religion and science,{{sfn|Larson|2004|p=73}} and because he was unusually open to marginal, even fringe, ideas in science.{{sfn|Shermer|2002|p=54}}

Wallace was profoundly influenced by [[Robert Chambers (journalist)|Robert Chambers]]'s ''Vestiges of the Natural History of Creation'', a controversial work of popular science published anonymously in 1844. It advocated an evolutionary origin for the [[Solar System]], the Earth, and living things.{{sfn|Slotten|2004|p=31}} Wallace wrote to Henry Bates in 1845 describing it as "an ingenious hypothesis strongly supported by some striking facts and analogies, but which remains to be proven by ... more research".{{sfn|Shermer|2002|p=54}} In 1847, he wrote to Bates that he would "like to take some one family [of beetles] to study thoroughly, ... with a view to the theory of the origin of species."<ref>Wallace Family Archive, 11 October 1847, quoted in {{harvnb|Raby|2002|p=1}}.</ref>

Wallace planned fieldwork to test the evolutionary hypothesis that closely related species should inhabit neighbouring territories.{{sfn|Larson|2004|p=73}} During his work in the [[Amazon basin]], he came to realise that geographical barriers—such as the Amazon and its major tributaries—often separated the ranges of closely allied species. He included these observations in his 1853 paper "On the Monkeys of the Amazon". Near the end of the paper he asked the question, "Are very closely allied species ever separated by a wide interval of country?"{{sfn|Slotten|2004|p=94}}

In February 1855, while working in [[Sarawak]] on the island of [[Borneo]], Wallace wrote "On the Law which has Regulated the Introduction of New Species". The paper was published in the ''[[Journal of Natural History|Annals and Magazine of Natural History]]'' in September 1855.<ref>{{cite web |title=Wallace Collection – Wallace's 'Sarawak law' paper |url=http://www.nhm.ac.uk/nature-online/collections-at-the-museum/wallace-collection/closeup.jsp?itemID=138&theme=Evolution |publisher=[[Natural History Museum, London|Natural History Museum]] |year=2012 |access-date=14 February 2012 }}</ref> In this paper, he discussed observations of the geographic and geologic distribution of both living and fossil species, a field that became biogeography. His conclusion that "Every species has come into existence coincident both in space and time with a closely allied species" has come to be known as the "Sarawak Law", answering his own question in his paper on the monkeys of the Amazon basin. Although it does not mention possible mechanisms for evolution, this paper foreshadowed the momentous paper he would write three years later.<ref>{{cite web |last=Wallace |first=Alfred Russel |title=On the Law Which has Regulated the Introduction of Species |url=http://www.wku.edu/%7Esmithch/wallace/S020.htm |year=1855 |publisher=[[Western Kentucky University]] |access-date=8 May 2007 |archive-url=https://web.archive.org/web/20070428194531/http://www.wku.edu/~smithch/wallace/S020.htm |archive-date=28 April 2007 |url-status=live}}</ref>

The paper challenged Lyell's belief that species were immutable. Although Darwin had written to him in 1842 expressing support for transmutation, Lyell had continued to be strongly opposed to the idea. Around the start of 1856, he told Darwin about Wallace's paper, as did [[Edward Blyth]] who thought it "Good! Upon the whole!&nbsp;... Wallace has, I think put the matter well; and according to his theory the various domestic races of animals have been fairly developed into ''species''." Despite this hint, Darwin mistook Wallace's conclusion for the [[progressive creationism]] of the time, writing that it was "nothing very new&nbsp;... Uses my simile of tree [but] it seems all creation with him." Lyell was more impressed, and opened a notebook on species in which he grappled with the consequences, particularly for human ancestry. Darwin had already shown his theory to their mutual friend [[Joseph Dalton Hooker|Joseph Hooker]] and now, for the first time spelt out the full details of natural selection to Lyell. Although Lyell could not agree, he urged Darwin to publish to establish priority. Darwin demurred at first, but began writing up a ''species sketch'' of his continuing work in May 1856.{{sfn|Desmond|Moore|1991|p=438}}{{sfn|Browne|1995|pp=537–546}}