Sociobiology is the study of the biological bases of behavior in the context of neo-Darwinian evolutionary theory. This review organizes the contribution of sociobiology to the understanding of human behavior around a small number of major theoretical articulations. These include identification of the gene as the basic unit of selection: the concept of inclusive fitness and the role of relatedness: models of reciprocal altruism and the concept of evolutionarily stable strategy (ESS): and the theory of optimal reproductive investment. Sociobiological and evolutionary thinking is expected to affect sociology in a number of areas including sex and gender roles: the theory of collective action: and the elaboration of a richer and more complex model of human nature.