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 Genius evolutionary theory that portrays natural selection as acting at the level of the individual gene to the exclusion of group selection models which state that it could also act at the level of organisms or species. The book also claims Dawkins embraces an outdated and prescriptive conception of evolution that actually restricts debate rather than promoting it. The book has provoked controversy with some online commentary claiming it is another 'flea', a term used by Dawkins to describe people who have published books about him or his ideas. An article by Fern Elsdon-Baker in "New Scientist" of 19 July 2009