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 Selfish Gene and Natural Selection" (1966), which argued that altruism is not based upon group benefit "per se", but is a result of selection that occurs "at the level of the gene mediated by the phenotype" and any selection at the group level occurred only under rare circumstances. This approach was developed further during the 1960s by W. D. Hamilton and others who opposed group selection and selection aimed directly at benefit to the individual organism: Despite the principle of 'survival of the fittest' the ultimate criterion which determines whether [a gene] "G" will spread is not whether the behavior is to