Charles Darwin formally presented his theory of evolution by natural selection in 1858, but it was fully published and explained in his book On the Origin of Species, released on 24 November 1859.
Thoughts on the possibility of transmutation of species which he recorded in 1836 towards the end of his five-year voyage on the Beagle were followed on his return by findings and work which led him to conceive of his theory in September 1838. He gave priority to his career as a geologist whose observations and theories supported Charles Lyell's uniformitarian ideas, and to publication of the findings from the voyage as well as his journal of the voyage, but he discussed his evolutionary ideas with several naturalists and carried out extensive research on his "hobby" of evolutionary work.
He was writing up his theory in 1858 when he received an essay from Alfred Russel Wallace who was in Borneo, describing Wallace's own theory of natural selection, prompting immediate joint publication of extracts from Darwin's 1844 essay together with Wallace's paper as On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection in a presentation to the Linnaean Society on 1 July 1858. This attracted little notice, but spurred Darwin to write an "abstract" of his work which was published in 1859 as his book On the Origin of Species.
Background
Darwin's ideas developed rapidly from the return in 1836 of the Beagle survey expedition. By December 1838 he had developed the principles of his theory. At that time similar ideas brought others disgrace and association with the revolutionary mob. He was conscious of the need to answer all likely objections before publishing. While he continued with research as his "prime hobby", his priority was an immense amount of work on geology and analysing and publishing findings from the Beagle expedition. This was repeatedly delayed by illness.
Natural history at that time was dominated by clerical naturalists whose income came from the Established Church of England and who saw the science of the day as revealing God's plan. Darwin found three close allies: Charles Lyell, Joseph Dalton Hooker and Thomas Huxley. Books by the eminent geologist Charles Lyell had influenced the young Darwin during the voyage, and he then befriended Darwin who he saw as a supporter of his ideas of gradual geological processes with continuing divine Creation of species. By the 1840s Darwin became friends with the young botanist Joseph Dalton Hooker, who had followed his father into that science, and after going on a survey voyage used his contacts to eventually find a position. In the 1850s Darwin met Thomas Huxley, an ambitious naturalist who had returned from a long survey trip but lacked the family wealth or contacts to find a career and who joined the progressive group around Herbert Spencer fighting to make science a profession, freed from the clerics.
Darwin made attempts to open discussions about his theory with his close scientific colleagues. In January 1842 Darwin sent a tentative description of his ideas in a letter to Lyell, then prepared a "Pencil Sketch" of his theory. He worked up his "Sketch" into an "Essay" in 1844, and eventually persuaded Hooker to read a copy in January 1847. His geology books and publication of Beagle findings were completed in 1846, when he began what became eight years of research into classification of barnacle species, exploring the immense amount of variation in nature.
In September 1854 Darwin had the last of his barnacle monographs ready for publication, and he turned his attention fully to questions about how species originated. He freely discussed his intention to write a book on the subject, and planned avenues of research with other scientists. He went over his previous notes and writings on the topic, and drew up proposals for investigations and research into the implications of his theory. One topic was explaining geographical distribution of organisms; he got information from international correspondence, and experimented on the viability of methods of dispersal. He widened his investigations into variability in nature, and experimented on plant hybridisation and cross-fertilisation.
Variation under domestication became a major topic of research: in 1855 he began to develop a web of contacts, both in the UK and worldwide, to get information on the origins and variation of domesticated animals, particularly poultry, ducks, rabbits, and pigeons. He got extensive information, specimens and ideas from Edward Blyth in India, who put him in contact with Edgar Leopold Layard in South Africa. At the suggestion of William Yarrell, Darwin began pigeon breeding at Down House to investigate varieties of domestic pigeons, and gained access to the expertise of William Bernhard Tegetmeier who was glad to research aspects of interest to Darwin. From March, he also got information and specimens from his relative William Darwin Fox who bred poultry and ducks at his rectory in the parish of Delamere, Cheshire.
In 1856 he was gradually bringing his friends round towards accepting evolution as a process, but was far from convincing them about the mechanism, when Wallace's entry into the discussion brought a new urgency to publication.
Wallace Alfred Russel Wallace, a naturalist working as a specimen collector in Borneo, spent Christmas 1854 visiting Sir James Brooke, the White Rajah of Sarawak, then during the ensuing rainy season lived alone in a little Dayak house, with only one Malay servant as cook. He recalled, "during the evening and wet days, I had nothing to do but look over my books". He had already read Lyell's Principles of Geology which opposed Lamarck by arguing that the fossil record showed no progress. Wallace had also read the 1845 second edition of Darwin's Journal of Researches which hinted at evolution by describing the "wonderful relationship in the same continent" between fossil and extant species, which would "throw more light on the appearance of organic beings on our earth, and their disappearance from it, than any other class of facts". In it, Darwin had described how species unique to the Galápagos Islands "all show a marked relationship with those of America" despite its distance. – the first edition called the relationship the "law of the succession of types";
Wallace had also been impressed by Pictet's studies of palaeontology, and was now annoyed by a recent article by Edward Forbes which dismissed evolutionary ideas and instead proposed that species were created in a pattern showing a divine plan of polarity. In February, Wallace completed his paper "On the Law which has Regulated the Introduction of New Species" which was published in September 1855 in the Annals and Magazine of Natural History.
This "Sarawak paper" countered Forbes, and showed Wallace's opinions. He incorporated points from Lyell, Darwin, Pictet and others, including Vestiges of the Natural History of Creation. It combined these with Wallace's own observations to support his conclusion that "Every species has come into existence coincident both in space and time with a closely allied species". This was a theory of a succession of species, but referred to "creation" rather than explicitly proposing an evolutionary mechanism [in 1905 Wallace recalled that he left descent to be inferred]. Brooke read it as either a series of creations or one species growing into another, and in 1856 told Wallace he had no objection to the latter. Wallace had told him that the paper was to "feel the pulse of scientific men" about the hypothesis, and Brooke was indignant at the suggestion that "bigotry & intolerance" would be aroused by novel views: this would explain Wallace's ambiguity.Brooke, James. (1856), [WCP3073.3041: Letter from Brooke, James to Wallace, Alfred Russel, Sarawak, dated 4 July 1856]. In : Beccaloni, G. W. (Ed.). Wallace Letters Online, accessed 20 December 2016 Lyell's resistance to Darwin's evolutionary ideas was shaken by the paper; in November 1855 Lyell began writing species notebooks, starting with a note about Wallace. On 8 December Edward Blyth wrote from Calcutta to ask Darwin for his views on the paper. Blyth thought it "Good! Upon the whole!" and said "according to his theory, the various domestic races of animals have been fairly developed into species". It is not known when Darwin read this letter.
During December 1855, Darwin extended his research into variation under domestication with letters to nearly 30 people around the world, requesting their help in obtaining specimens of "Any domestic breed or race, of Poultry, Pigeons, Rabbits, Cats, & even dogs, if not too large, which has been bred for many generations in any little visited region." As Blyth had suggested earlier, Darwin wrote on 9 December to Edgar Leopold Layard in South Africa, and said that he was "collecting all the facts & reasoning which I could, in regard to the variation & origin of species", particularly pigeons. On 24 December Darwin wrote to the diplomat Sir Charles Murray in Persia, similarly saying he had "for many years been working on the perplexed subject of the origin of varieties & species, & for this purpose I am endeavouring to study the effects of domestication". Letters also went to Brooke, and to Wallace via his agent Samuel Stevens. In August 1856 Wallace told Stevens that specimens for Darwin were included in a shipment. In November Darwin wrote to tell William Bernhardt Tegetmeier that a box of Persian poultry specimens from Murray had arrived, and "Mr Wallace is collecting in the Malay Archipelago".
Wallace's "Sarawak paper" was included in the July–December 1855 volume of the Annals and Magazine of Natural History. Darwin jotted comments in his copy of this volume: "Laws of Geograph. Distrib. nothing very new", and "Uses my simile of tree— It seems all creation with him", but "he puts the facts in striking point of view". He noted Wallace's point that geological knowledge was imperfect, and commented "put generation for creation & I quite agree". (two years later, Darwin still thought Wallace was proposing creation).
"Natural Selection" When Lyell and his wife visited the Darwins at Downe from 13 to 16 April 1856, Darwin explained his theory to Lyell, who then wrote up notes headed "With Darwin: On the Formation of Species by Natural Selection", with pigeons as one example. At another Down House party on 26–27 April, Darwin had long discussions with his guests Joseph Dalton Hooker, Thomas Henry Huxley, and Thomas Vernon Wollaston. Lyell subsequently heard that they "ran a tilt against species farther I believe than they are deliberately prepared to go. ... I cannot easily see how they can go so far, and not embrace the whole Lamarckian doctrine."
On 1 May Lyell wrote to urge Darwin to establish priority: "I wish you would publish some small fragment of your data pigeons if you please & so out with the theory & let it take date—& be cited—& understood." Darwin replied on 3 May: "With respect to your suggestion of a sketch of my view; I hardly know what to think, but will reflect on it; but it goes against my prejudices. To give a fair sketch would be absolutely impossible, for every proposition requires such an array of facts. If I were to do anything it could only refer to the main agency of change, selection,—& perhaps point out a very few of the leading features which countenance such a view, & some few of the main difficulties. But I do not know what to think: I rather hate the idea of writing for priority, yet I certainly shd be vexed if any one were to publish my doctrines before me."
On Thursday 8 May, while in London for meetings, Darwin visited Lyell.