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
The Selfish Gene most common, simple, and profitable choice. More generally, the objection has been made that "The Selfish Gene" discusses philosophical and moral questions that go beyond biological arguments, relying upon anthropomorphisms and careless analogies. "The Selfish Gene" was first published by Oxford University Press in 1976 in eleven chapters with a preface by the author and a foreword by Robert Trivers. A second edition was published in 1989. This edition added two extra chapters, and substantial endnotes to the preceding chapters, reflecting new findings and thoughts. It also added a second preface by the author, but the original foreword by Trivers