The Biogeography of Social (dis)trust

Abstract: As a lubricant for mutually beneficial exchange, social trust is essential to the functioning of societies and helps overcome numerous collective action problems that would otherwise ail society. One of the most striking manifestations of cross-cultural variability, then, is the huge variation in social (dis)trust that can be observed across societies, specifically geopolitical units. So far, however, social scientists lack understanding of the deep roots of social distrust as one and perhaps the most important feature of human cultures. We test two theories on biogeographical factors explaining why some societies are so much more trusting than others, one identifying bio-climatic endowments and associated subsistence strategies and the other identifying pathogen stress and associated behavioural immune defences as fundamental determinants of social trust. A direct test with evidence for up to 94 geopolitical units consistently indicates that historical prevalence of infectious diseases is a more powerful predictor of social trust than are features related to subsistence strategies, including the availability of domesticable plants and animals, although both appear important. The timing of the Neolithic revolution, on the other hand, has little influence. Most importantly, distance to the equator trumps other influences, though not because it affects cultural diversity within geopolitical units.