sometimes evolving to foster more smoothly flowing trade between occupational castes or ethno-religious groups. In South Asia, for example, some medieval ports established enduring exchange relationships between local Hindus and Muslim traders on the Indian Ocean. Centuries later, long after the disruption of Islamic trade routes by European powers, trading ports experience less interethnic violence between Hindus and Muslims than nontrading cities. It seems that trade between these groups forged enduring informal institutions, the psychological effects of which persisted long after trade ceased. These kinds of prosocial effects can be observed today all over the world by examining the relationship between a community’s proximity to large rivers or oceans and the attitudes of its inhabitants toward foreigners and immigrants. Large rivers and oceans have long been, and remain, the arteries for much of the world’s trade. Living near a port usually means living in an urban center where norms, practices, and beliefs have been shaped by trade and commerce more intensely than elsewhere. This fact suggests that western Europe had a geographic edge over many parts of the world in developing trade and commerce: this region possesses an unusually large number of natural ports and navigable waterways as well as inland seas in both the north (Baltic) and the south (Mediterranean).64 Once market norms developed, they could rapidly disseminate along the waterways into the fertile grounds of ports. This geographic preparedness would have catalyzed the process of market integration that I’ve been describing. Summarizing our progress: the breakdown of intensive kin-based institutions opened the door to urbanization and the formation of free cities integration and—we can infer—higher levels of impersonal trust, fairness, and cooperation. While these psychological and social changes were occurring, people began to ponder notions of individual rights, personal freedoms, the rule of law, and the protection of private property. These new ideas just fit people’s emerging cultural psychology better than many alternatives. Urbanizing premodern Europe was being transformed from the middle outward, up and down the social strata. The last groups to feel these enduring psychological and social shifts were (1) the most remote subsistence farmers and (2) the highest levels of the aristocracy, who continued to consolidate power for centuries through intensive forms of kinship, long after it had been extirpated from the urban middle classes. Of course, this wasn’t a smooth and continuous transition, even in rapidly growing urban centers. One of the greatest threats to the functioning of voluntary associations was, and remains, intensive kinship. It wasn’t uncommon for new organizations, including banks and governments, to be usurped for a time by large, powerful families consolidated by arranged marriages.65 However, as noted, this is a tough road in the long run because the Church suppressed nearly all the basic tools of intensive kinship. Under these constraints, family businesses struggled to outcompete other organizational forms. At the same time, politically or economically powerful family lineages were simply more likely to die out without polygyny, customary inheritance, remarriage, and adoption. When dominant royal families did die out, urban communities were often able to re-forge their formal institutions in ways more appealing to people with a protoWEIRD psychology.

Joseph Patrick Henrich, The WEIRDest people in the world: How the west became psychologically peculiar and particularly prosperous, New York, 2020, p. 322