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
Feathers: The Evolution of a Natural Miracle is "something for everyone to learn", from professional ornithologists to non-biologists. Bostwick warned scientific readers, however, that "Feathers" uses poetic license "to adapt some of the historical accounts a little to make them flow as stories" and that "Hanson uses a few analogies to explain some of the more complex biological phenomenon that are not entirely accurate." Feathers: The Evolution of a Natural Miracle Feathers: The Evolution of a Natural Miracle is a 2011 natural history book by American conservation biologist Thor Hanson. Published by Basic Books and written for general audiences, the book discusses the significance of feathers, their