Parasite-stress promotes in-group assortative sociality: The cases of strong family ties and heightened religiosity

Abstract

<jats:title>Abstract</jats:title><jats:p>Throughout the world people differ in the magnitude with which they value strong family ties or heightened religiosity. We propose that this cross-cultural variation is a result of a contingent psychological adaptation that facilitates in-group assortative sociality in the face of high levels of parasite-stress while devaluing in-group assortative sociality in areas with low levels of parasite-stress. This is because in-group assortative sociality is more important for the avoidance of infection from novel parasites and for the management of infection in regions with high levels of parasite-stress compared with regions of low infectious disease stress. We examined this hypothesis by testing the predictions that there would be a positive association between parasite-stress and strength of family ties or religiosity. We conducted this study by comparing among nations and among states in the United States of America. We found for both the international and the interstate analyses that in-group assortative sociality was positively associated with parasite-stress. This was true when controlling for potentially confounding factors such as human freedom and economic development. The findings support the parasite-stress theory of sociality, that is, the proposal that parasite-stress is central to the evolution of social life in humans and other animals.</jats:p>

Parasite stress promotes homicide and child maltreatment

“…Moreover, a diverse body of research supports the hypothesis of an evolved contingent assortative sociality in people that functions against infectious disease [9]. For example, both xenophobia and ethnocentrism within individuals increase under experimental primes of greater disease salience in the current environment [7,10].…”

Moral concerns across the United States: associations with life-history variables, pathogen prevalence, urbanization, cognitive ability, and social class

“…Specifically, when controlling for teenage birth rate and ethnicity as measures of faster life-history strategy and extrinsic risk, respectively, pathogen prevalence no longer predicted variation in homicide, child abuse, and strength of family ties across states (cf. Fincher & Thornhill, 2012;Thornhill & Fincher, 2011). Faster life-history strategy is expected to be associated with higher teenage birth rate and shorter life expectancy.…”

“…We obtained state-level data for urbanization, pathogen prevalence, and life-history For all 50 states, data on pathogen prevalence were obtained from Hackman and Hruschka (2013), who critiqued the pathogen prevalence measure provided by Fincher and Thornhill (2012). To estimate state-level pathogen prevalence, Fincher and Thornhill used data from the US's Centers for Disease Control for the set of infectious diseases monitored for all states for the years 1993-2007.…”

“…For Morals USA 12 each year, the number of cases of disease was controlled for state population. Hackman and Hruschka (2013) showed that Fincher and Thornhill's (2012) Table S3.…”

“…As noted by Hackman and Hruschka, with regard to tests of the parasite stress model, the C&G index suffers from the same issue as Fincher and Thornhill's (2012) estimates of USA state-level pathogen prevalence. As both these indexes focus on STDs, they are likely to reflect both causes of sexually transmitted pathogens (e.g., faster life-history strategy behaviors such as promiscuity) and their effects (e.g., activation of anti-pathogen defenses).…”