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 to make some critical distinctions, in particular, the difference between group selection for group advantage and group selection conveying individual advantage. A good deal of objection to "The Selfish Gene" stemmed from its failure to be always clear about "selection" and "replication". Dawkins says the gene is the fundamental unit of selection, and then points out that selection doesn't act directly upon the gene, but upon 'vehicles' or 'extended phenotypes'. Stephen Jay Gould took exception to calling the gene a 'unit of selection' because selection acted only upon phenotypes. Summarizing the Dawkins-Gould difference of view, Sterelny says: The word 'cause'