The social control of fertility

Abstract

Social factors are now well recognized as having profound effects on reproduction in many mammals, from rodents (McClintock, 1983) to humans (Preti et al., 1986). Given that a high degree of social complexity is synonymous with the primate order, it is not surprising that the social environment of primate groups has become a predominant environmental factor influencing reproduction at both behavioural and physiological levels (Wasser and Barash, 1983; Abbott, 1987; Keverne, 1987; Dunbar, 1988). The ability of social factors to exert such control over reproduction in primates is probably related to the development of the neocortex in the brain. The neocortex influences the neuroendocrine limbic brain, including the hypothalamus. Such increased cognitive input into the neural centres that control internal physiological events might explain the diminished effects of environmental cues, such as photoperiod on primate reproduction (Ruiz de Elvira et al., 1982; Wehrenberg and Dyrenfurth, 1983; Herndon et al., 1987), and the diminished effects of fluctuations in gonadal hormones on the expression of primate sexual behaviour (Dixson, 1983; Kendrick and Dixson, 1984; Keverne, 1985).