Collectivism–Individualism, Family Ties, and Philopatry

Thornhill, Randy; Fincher, Corey L.

As predicted by the parasite-stress theory of values, variation in parasite stress correlated with collectivism–individualism across nations, USA states, and indigenous societies. In regions with high adversity of infectious diseases, human cultures are characterized by high collectivism, whereas in regions of low parasite stress cultures are highly individualistic. The prediction from the parasite-stress theory of values that infectious disease transmissible among humans (nonzoonotics) will be more important in predicting collectivism–individualism than those that humans can contract only from nonhuman animals (zoonotics) was supported. Evidence in human movement patterns for nations, states of the USA, and indigenous societies supports the hypothesis that the absence of dispersal (high philopatry) is a defense against contact with novel parasites in out-groups and their habitats. We show that human cultures with high degrees of collectivism have high degrees of cooperative breeding, and propose that the parasite-stress theory of sociality offers a general theory of family structure across humans as well as nonhuman animal taxa. We propose that a major context for the evolution of human reciprocity was in gaining benefits from out-group interactions during periods of relatively low disease threat. The parasite-stress theory of values offers a novel perspective to explain the evolution of reciprocity and human unique cognitive abilities. The parasite-stress theory suggests useful new research directions for the study of the demographic transition, patriotism, xenophobia, ethnocentrism, and moral foundations theory. We include discussion of ecological correlations and the ecological fallacy. The fact that all scientific findings are correlational is explained.