Thirty years ago, three disciplines – ethology, endocrinology, and ecology – undertook the explanation of primate social behavior. Ethological methods have since become universal in primatology, but endocrine and ecological investigations have maintained greater distance. Despite remarkable similarities in the research plans presented in influential papers in behavioral endocrinology (Beach, 1975) and socioecology (Crook et al., 1976) (see Fig. 10.1), differing methods and priorities (see Table 10.1) set these two research areas on divergent trajectories. The experimental methods of early behavioral endocrinology in which hormones were detected and characterized by their action focused attention on the evidence and mechanisms for hormonal influences on individual behavior with less attention to social context and contingencies (Worthman, 1990). Early socioecology, relying on correlations between gross categories of social system and environment, sidestepped the issue of process (Richard, 1981) while focusing attention on the group as the locus of behavioral evolution. Although these different emphases hampered the integration of endocrine and ecological perspectives, the research areas have independently converged as each has broadened its methodologies and perspectives. The causal focus and experimental approaches of behavioral endocrinology have expanded to include a more synergistic framework and observational approach, termed “socioendocrinology,” reflecting an emerging view of the individual as a social organism and new attention to the role of social processes in the regulation of hormone function (Bercovitch and Ziegler, 1990).