Unit of selection and Confirmation of Evolutionary Theory" provides a basic "philosophical" introduction to the debate. Below, cases of selection at the genic, cellular, individual and group level from within the multi-level selection perspective are presented and discussed. George C. Williams in his influential book "Adaptation and Natural Selection" was one of the first to present a gene-centered view of evolution with the gene as the unit of selection, arguing that a unit of selection should exhibit a high degree of permanence. Richard Dawkins has written several books popularizing and expanding the idea. According to Dawkins, genes cause phenotypes and a gene is
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,