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
Vestiges of the Natural History of Creation a very wide circulation. Darwin even suggested that Chambers' book helped pave the way for the publication of his theory of evolution by natural selection. "In my opinion it has done excellent service in this country in calling attention to the subject, in removing prejudice, and in thus preparing the ground for the reception of analogous views." The harsh reception that "Vestiges" received, and the mockery which was made of its evolutionary ideas, has been cited by some historians as a factor leading to Darwin's caution in publishing his own theory of evolution. In a letter to Thomas Henry Huxley