The Evolution of Monogamy: Hypotheses and Evidence

Abstract

Recent theoretical insights are helping to clarify how animal mating sys­ tems evolve. An integrated theory is beginning to emerge from the realiza­ tion that males and females have overlapping but nonidentical reproductive interests and that the type of mating system shown by a species results from interactions between the individual interests of each sex. The optimal mat­ ing system for promoting individual reproductive interests often differs for each sex, and when it does, the interests of one sex constrain the reproduc­ tive options open to the other. Thus, mating system theory revolves around two major issues: the factors determining which sex predominates in shap­ ing each mating system, and the factors determining which mating system is optimal for members of the controlling sex. The greatest progress has been made in explaining how polygynous mat­ ing systems evolved, particularly among territorial vertebrates, and more recent work is clarifying the specific environmental conditions involved (4, 46, 145, 146, 161, 227, 244, 246, 247). Promiscuous and polyandrous mating systems are less well understood, but several promising avenues toward a general theory have begun to develop (7 1, 9 1 , 126, 240, 245, 246). In contrast, theoretical work on the evolution of monogamy lags far behind, despite an enormous literature on monogamous animals.