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
The Evolution of Beauty that was adapted from "The Evolution of Beauty", stating that it is "both erroneous and confusing, for it misrepresents sexual selection, natural selection, and modern evolutionary theory." He later described the book as a "mixed bag" but stated that the bad parts outweighed the good, and stated that Prum's arguments were "tendentious". Evolutionary biologists Gerald Borgia and Gregory Ball state that Prum misrepresents opposition of scientists to the model of runaway selection and that he fails to make a case for its ubiquity. Further, they claim Prum inappropriately injects politics into biology, conflating eugenics and genocide with female mate choice