The use of evolutionary models to examine political behavior in international relations has been the subject of much debate, but serious scholarly work has generally been lacking, in part because the causal mechanisms have not always been clearly explicated. An evolutionary psychological framework can correct this deficit and benefit research in at least three major areas of international relations: (1) how political groups such as states are perceived and represented by individuals and groups; (2) how coalitional action is facilitated among states; and (3) sex differences in coalitional behavior. Hypotheses are offered in each of these areas to more clearly demonstrate the psychological mechanisms that are the bridge between evolutionary theory and political behavior in the international system. The social and political landscape of the ancestral environments in which humans evolved strongly suggests that the psychological architecture of humans possesses specialized design for coalitional living that continues to guide behavior in the modern political world. These evolved mechanisms structure human motivation and engagement in areas including leadership and war.

Does the security of women influence the security and behavior of states? Existing evidence linking the situation of women to state-level variables such as economic prosperity and growth, health, and corruption is fairly conclusive. Questions remain, however, concerning the degree to which state security and state security-related behavior is linked to the security of women. The “women and peace” thesis draws upon evolutionary biology/psychology for ultimate causes of this linkage, and sociological theories of social diffusion and psychological theories of social learning for more proximate causal mechanisms. Together, a new data resource—the WomanStats Database—and conventional methodology find a robust, positive relationship between the physical security of women and three measures of state security and peacefulness. In addition, a comparison of this proposition to alternative explanations involving level of democracy, level of economic development, and civilizational identity shows that the physical security of women is a better predictor of state security and peacefulness. Although these results are preliminary, it is still possible to conclude that the security of women must not be overlooked in the study of state security, especially given that the research questions to be raised and the policy initiatives to be considered in the promotion of security will differ markedly if the security of women is seriously considered as a significant influence on state security.