 This was contrasted with personal reproductive fitness, the number of offspring that the individual directly begets.Hamilton, and others such as John Maynard Smith, argued that a gene's success consisted in maximising the number of copies of itself, either by begetting them or by indirectly encouraging begetting by related individuals who shared the gene, the theory of kin selection.In 1966, George C. Williams published "Adaptation and Natural Selection", outlined 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.