The Evolution of Cooperation insects, where the workers – which are sterile, and therefore incapable of passing on their genes – benefit the queen, who is essentially passing on copies of "their" genes. This is further elaborated in the "selfish gene" theory of Richard Dawkins, that the unit of evolution is not the individual organism, but the gene. (As stated by Wilson: "the organism is only DNA's way of making more DNA.") However, kinship selection works only where the individuals involved are closely related; it fails to explain the presence of altruism and cooperation between unrelated individuals, particularly across species. In a 1971 paper
Feathers: The Evolution of a Natural Miracle 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 evolution, and their history both in nature and in use by humans. "Feathers" is divided into five parts. In "Evolution", Hanson discusses the scientific debate over how feathers evolved, interviewing ornithologists Richard Prum and Alan Feduccia, as well as paleontologist Xing Xu. In "Fluff", Hanson discusses how feathers play a role in regulating a bird's body temperature