Modern synthesis (20th century) a gene-centred view of evolution following Hamilton's concepts, disputing the idea of evolutionary progress, and attacking the then widespread theory of group selection. Williams argued that natural selection worked by changing the frequency of alleles, and could not work at the level of groups. Gene-centred evolution was popularised by Richard Dawkins in his 1976 book "The Selfish Gene" and developed in his more technical writings. In 1975, E. O. Wilson published his controversial book "", the subtitle alluding to the modern synthesis as he attempted to bring the study of animal society into the evolutionary fold. This appeared radically new,
The Evolution of Beauty preeminent. Prum proceeds to apply the principle of aesthetic evolution as an independent force in human evolution. Prum indicates that Darwin recognizing difficulties in the theory of natural selection advanced the view that sexual selection is an additional force in evolution and presented this argument in "The Descent of Man". Alfred Russel Wallace, St. George Mivart and other early evolutionists helped to elevate natural selection as the only force in evolution and delegated sexual selection to a subsidiary role. It was argued that sexual selection was based on recognition of markers of survival fitness, so that, for instance in birds,