Another helping - A plea for studying kin effects from an interdisciplinary perspective

Having kin and living together with kin influence the individual life course, including a person’s marriage, reproductive career, and survival. A wide range of mechanisms are involved in connecting these life course transitions to support and competition between kin, as well as to characteristics of the family environment. How kin affect the life course is perceived differently in evolutionary anthropology than in the social sciences, and these perspectives are seldom integrated into research. In the present article, we review predictions of the influence of in-law relatives on fertility and mortality presented in selected studies. We will then discuss their explanatory power by discussing the influence of the mother-in-law on the mortality of reproductive females in the historical populations of the Krummhörn region in Germany (1720-1874) and the St. Lawrence Valley in Quebec, Canada (1670-1799). Social science studies tend to emphasize the role of kin in economic and social resource availability, and especially the family characteristics that are relevant in providing, accessing, and dividing resources. In contrast, evolutionary anthropology tends to emphasize the evolved inclinations of kin to support as well as to compete with each other. On the one hand, we argue that the social sciences would benefit from integrating the evolutionary theory of human behavior. On the other hand, evolutionary anthropology would benefit from the comprehensive acknowledgment of the socio-environmental factors in population since these may mask evolved inclinations.