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Catholicism’s policy forbidding cousins to wed may have led to the distinctive characteristics of Western society

The WEIRDest People in the World: How the West Became Psychologically Peculiar and Particularly Prosperous

Joseph Henrich
Farrar, Straus and Giroux
704 pp.
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A few years after the end of Tajikistan’s half-decade-long civil war, I was on an assignment in the former Soviet republic and announced my intention to purchase vegetables at the market. My local friends scoffed. “It’s impossible” they said. “You have no cousins at the market. People will sell you a poison tomato.” The poison tomato, I learned, was a wilted tomato made to look fresh by injecting it with water (usually from a nearby
sewer). As Joseph Henrich recounts in his new book, The WEIRDest People in the World, the Tajik civil war—which pitted clan against clan and, sometimes, neighbor against neighbor—resulted in a collapse of trust that made people more suspicious of nonrelatives.

This trajectory is puzzling, as it contrasts sharply with political development in Western Europe. There, conflict and intergroup
competition paved the way for strong and democratic states. So what accounts for the difference between these two groups?

War’s impact on cultural and institutional evolution, Henrich argues, depends on preexisting conditions, especially people’s psychological dispositions. In Europe, after the collapse of the Carolingian Empire, clans had been destroyed by the Roman Catholic Church, and people were already infused with a sense of universal morality. War further deepened their commitments to voluntary associations, such as universities, merchant guilds, and monasteries. It also reinforced Christian norms and motivated greater contributions to the public good, igniting the perpetuation of liberal values and strong impersonal states.

Henrich’s argument is that Catholicism, by forbidding cousin marriage, enabled Europe to escape the “tyranny of cousins” (1). More importantly, he argues, it explains how—in the process—Western Europeans became “WEIRD” (Western, educated, industrialized, rich, and democratic). The first part of the book describes WEIRD people in broad strokes, painting them
as individualistic, often guilty but never ashamed, patient, hardworking, achievement oriented, and trusting of strangers. Here, Henrich provides a backhanded criticism of the field of psychology, which claims to uncover how humans make choices, while relying mainly on WEIRD subjects. (Ironically, Henrich notes, the desire to uncover universal truths is another trait commonly seen in WEIRD people.)

The second part of the book provides a comparative political account of how societies scale up from families to states. Here, Henrich adds a twist, describing how institutional development feeds back into psychology. Citing data from his own research, he argues that religion not only enhances prosociality, enables the provision of public goods, and can legitimize political institutions but also shapes our cognition by, for example, making us think about moral universals.

The third section of the book focuses on how Catholicism, and later Protestantism, shaped institutions and psychology. Unlike other religions, Catholicism historically forbade cousin marriage and affinal remarriage (for example, marrying an inlaw after the death of one’s spouse), limited adoption, and encouraged individual ownership. By doing so, the Church managed to break what was, and remains, the biggest threat to states, the largest hurdle to the development of impersonal markets, and the greatest inhibitor of individualism: clannishness.

But how and why did the Church home in on cousin marriage prohibition? And why did some people and not others adopt and convert to Catholicism (and later Protestantism)? Henrich describes how ecological endowments shape people’s psychology and can make them more likely to adopt certain norms and institutions, but he never specifically applies this argument
to the reasons Western Europeans adopted Catholicism in the first place. He does, however, suggest that the Europeans’ propensity for late marriage was a consequence of the Church’s marriage prohibitions. This is inconsistent with the evidence that there has been much variation over time in the age at marriage and also the fact that it dropped sharply when 19th-century Europeans migrated to the colonies of the United States or Australia, where land was much more abundant.

Another point that Henrich does not address is the role that states may have played as competitors and regulators of the Church. In many parts of Africa and the Pacific, where states are weak, Catholic and Protestant churches are as successful as they are nepotistic and corrupt. What accounts for this difference? I will continue to follow Henrich’s work and avidly await the answer.


  1. An expression coined by Francis Fukuyama in his book The Origins of Political Order: From Prehuman Times to the French Revolution (Farrar, Straus and Giroux, 2011).

About the author

The reviewer is at the Department of Economics, University of New South Wales, Sydney, NSW 2052, Australia.