Gargantuan (174 pages) paper with an staggering amount of data about family systems and kinship related institutions by Jonathan Schulz et al. (2018): The Origins of WEIRD Psychology (h/t @pseudoerasmus).

Our approach integrates three insights. The first, drawing on anthropology, reveals that the institutions built around kinship and marriage vary greatly across societies (21–23) and that much of this variation developed as societies scaled up in size and complexity, especially after the origins of food production 12,000 years ago (22, 24–29). In forging the tightly-knit communities needed to defend agricultural fields and pastures, cultural evolution gradually wove together social norms governing marriage, post-marital residence and ingroup identity (descent), leading to a diversity of kin-based institutions, including the organizational forms known as clans, lineages and kindreds (21, 27, 30). The second insight, based on work in psychology, is that people’s motivations, emotions, perceptions, thinking styles and other aspects of cognition are heavily influenced by the social norms, social networks, technologies and linguistic worlds they encounter while growing up (31–38). In particular, with intensive kin-based institutions, people’s psychological processes adapt to the collectivistic demands and the dense social networks that they interweave (39–43). Intensive kinship norms reward greater conformity, obedience, holistic/relational awareness and in-group loyalty but discourage individualism, independence and analytical thinking (41, 44). Since the sociality of intensive kinship is based on people’s interpersonal embeddedness, adapting to these institutions tends to reduce people’s inclinations towards impartiality, universal (non-relational) moral principles and impersonal trust, fairness and cooperation. Finally, based on historical evidence, the third insight suggests that the branch of Western Christianity that eventually evolved into the Roman Catholic Church—hereafter, ‘the Western Church’ or simply ‘the Church’—systematically undermined the intensive kin-based institutions of Europe during the Middle Ages (45–52). The Church’s marriage policies and prohibitions, which we will call the Marriage and Family Program (MFP), meant that by 1500 CE, and likely centuries earlier in some regions, Europe lacked strong kin-based institutions, and was instead dominated by relatively weak, independent and isolated nuclear or stem families (49–51, 53–56). This made people exposed to Western Christendom rather unlike nearly all other populations. Integrating these insights, we propose that the spread of the Church, specifically through its transformation of kinship and marriage, was a key factor behind a cultural shift towards a WEIRDer psychology in Europe. This shift eventually fostered the creation of new formal institutions, including representative governments, individual rights, commercial law and impersonal markets (17, 57). This theory predicts that (1) societies with less intensive kin-based institutions should have a WEIRDer psychology and (2) historical exposure to the Church’s MFP should predict both less intensive kin-based institutions and, as a consequence, a WEIRDer psychology.

Anyhow, there is zero chance that I am going to read this paper closely now or anytime soon, so for now I am just going to highlight the things that caught my eye there.

All the correlations are as we would expect them to be.

Conclusion:

To begin to explain the psychological differences now documented around the globe, we have proposed a two-part theory. First, we hypothesize that, in adapting to the social worlds created by intensive kin-based institutions, human psychology shifts in ways that foster greater conformity, obedience and sensitivity to relational contexts but less individualism, analytic thinking and cooperation with strangers. Second, to account for part of the variation in kinship intensity, we hypothesize that Western Christianity, beginning around 500 CE, gradually implemented a set of policies about marriage and the family—the MFP—that was a critical contributor to the eventual dissolution of the intensive kin-based institutions of Europe. By 1500 CE, this left many regions of Western Europe dominated by independent, monogamous, nuclear families—a peculiar configuration called the European Marriage Pattern (54, 55, 97). This two-part theory implies that the Church, through the MFP, inadvertently contributed to what psychologists have termed WEIRD psychology. We tested these hypotheses at three levels of analysis. Across countries, our analyses of 16 variables confirm that populations with less intensive kin-based institutions historically are psychologically WEIRDer today: they are more individualistic and independent but less nepotistic, conformist, obedient and holistically-oriented. Socially, populations with weaker kin-based institutions reveal less in-group loyalty, diminished moral particularism and greater trust, fairness and cooperation with strangers. Then, zooming in on Europe, by tracking the diffusion of the MFP from 550 to 1500 CE, we show that the longer a regional population was exposed to the Church, the higher their measures of individualism-independence and generalized trust and fairness and the lower their measure of conformity-obedience. Then, by tapping remnants of intensive kinship in Western Europe, we demonstrate that greater exposure to the Church is associated with less cousin marriage in the 20th century, which in turn is associated with stronger individualism, less conformity and greater impersonal prosociality. In Italy, we further demonstrate that higher rates of cousin marriage are associated with fewer voluntary blood donations (a public good). Lastly, by linking second-generation immigrants in Europe back to the places where their parents originated, we demonstrate that the influence of both intensive kinship and Church exposure can still be detected psychologically among the adult children of immigrants living in the same European countries.

Comments:

1. No, hbd*chick is not acknowledged, though she really should be in what appears to be the most comprehensive overview of this topic to date.

2. Do they produce a national index of kinship intensity/cousin marriage/etc. anywhere in the paper, or could one at least be easily constructed from the wealth of data they have accumulated? (E.g., something like what JayMan attempted to do, if not very rigorously). It would be good to test if kinship intensity, cousin marriage, family structure, and/or some general “inbreeding index” combining all of these, has any independent effects (in addition to IQ/oil windfalls/Communist legacy) on current levels of GDP per capita/general socioeconomic success.