George C. Williams (biologist) should only be used where it is really necessary", and, that, when it is necessary, selection among genes or individuals would in general be the preferable explanation for it. He elaborated this view in later books and papers, which contributed to the development of a gene-centered view of evolution; Richard Dawkins built on Williams' ideas in this area in the book "The Selfish Gene". Williams was also well known for his work on the evolution of sex, and was an advocate of evolutionary medicine. In later books, including "Natural Selection: Domains, Levels and Challenges", Williams softened his views on group
On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection Darwin apparently mistook Wallace's meaning, writing "nothing very new... Uses my simile of tree, [but] it seems all creation with him". However, he spelt out the details of Natural Selection to Lyell, who found the idea hard to accept but urged Darwin to publish to establish priority. On 14 May 1856 Darwin began what became his draft for a book titled "Natural Selection". Wallace collected specimens and corresponded with Darwin from Borneo. In December 1857, he wrote to ask if Darwin's book would delve into human origins, to which Darwin responded that "I think I shall avoid the whole subject,