In the Late 1960s and early 1970s, a revolution occurred in evolutionary biology when several investigators, including most notably W. D. Hamilton, R. L. Trivers, and G. C. Williams, began to apply Darwin's theory of natural selection to the social behavior of animals. This new approach to behavior, which came to be known as “sociobiology” after the title of E. O. Wilson's influential 1975 book, was rapidly applied to human, as well as nonhuman, animal behavior. These applications often represented a serious challenge to the theories of the social and behavioral sciences, many of which rested on the assumption that behavior could be profitably analyzed in terms of its effects on the group or species. Sociobiologists, in contrast, argued that an adequate understanding of animal, including human, societies can be gained only by viewing selection as operating at the level of the individual (and sometimes at the level of the gene) rather than at the group level. The resultant controversies continue to this day, and sociobiological approaches to human behavior have had an important impact on anthropology, psychology, and other behavioral sciences, including political science.