The WEIRD Relationship between Cousin Marriage, Corruption, and the Mafia: A Selection from Joseph Henrich’s The WEIRDest People in the World (2020)

“The families found in WEIRD [i.e., Western, educated, industrialized, rich, and democratic] societies are peculiar, even exotic, from a global and historical perspective. We don’t have lineages or large kindreds that stretch out in all directions, entangling us in a web of familial responsibilities. Our identity, sense of self, legal existence, and personal security are not tied to membership in a house or clan, or to our position in a relational network. We limit ourselves to one spouse (at a time), and social norms usually exclude us from marrying relatives, including our cousins, nieces, stepchildren, and in-laws. Instead of arranged marriages, our ‘love marriages’ are usually motivated by mutual affection and compatibility. Ideally, newly married couples set up residence independent of their parents . . . .

How many people do you personally know who married their cousins? If you know none, that’s WEIRD [i.e., Western, educated, industrialized, rich, and democratic], since 1 in 10 marriages around the world today is to a cousin or other relative. . . . people in the Middle East and Africa marry relatives at least a quarter of the time, though in some places these numbers reach up above 50 percent—so over half of marriages are among relatives. . . . countries like India and China have moderate rates of cousin marriage, though it’s worth knowing that in China, when the government began promoting ‘modern’ (Western) marriage in the 1950s, it outlawed uncle-niece marriage and, later, first cousin marriage. By contrast, really WEIRD [i.e., Western, educated, industrialized, rich, and democratic] countries like the United States, Britain, [Canada], and the Netherlands have rates of about 0.2 percent, or one-fifth of 1 percent. . . .

In pre-Christian Europe, as in much of the world until recently, marriage customs had evolved culturally to empower and expand large kin-based organizations or networks. Marital bonds establish economic and social ties between kin-groups that foster trade, cooperation, and security. To sustain such ties, long-term marital exchanges are necessary, which usually means that new marriages must occur between blood or affinal relatives (in-laws). In patrilineal societies, senior males—the patriarchs—administer these ongoing spousal exchanges and thus use the marriage of their sisters, daughters, nieces, and granddaughters to cement relations with other kin-groups and nourish important alliances. Arranged marriages thus represent a key source of patriarchal power.

The Church dramatically undercut the potency of marriage as a social technology and a source of patriarchal power by . . . gradually extend[ing] its marriage prohibitions—the circle of incest—from primary relatives (e.g., daughters) and key in-laws (e.g., son’s wife) to include first cousins, siblings-in-law, and godchildren. The process first accelerated in the sixth century, under the Merovingian (Frankish) kings. From 511 to 627 CE, 13 of 17 Church councils addressed the problem of ‘incestuous’ marriage. By the beginning of the 11th century, the Church’s incest taboos had swollen to include even sixth cousins, which covered not only blood relatives but also affines and spiritual kin. For all practical purposes, these taboos excluded everyone you (or anyone else) believed that you were related to by blood, marriage, or spiritual kinship (god relatives). . . .

The higher a country’s . . . cousin marriage, the more people distrust strangers, new people, and adherents of other religions. . . . Based on responses from over 18,000 individuals from 68 different regions across four countries, people from regions with higher rates of cousin marriage in the 20th century show greater conformity-obedience, less individualism-independence, and lower levels of both impersonal trust and fairness. . . .

Now let’s zoom in even closer to focus on an enduring puzzle in the social sciences: the Italian enigma. While northern and central Italy emerged as powerful banking centers in the Middle Ages, stood at the center of the Renaissance, and prospered along with much of northern Europe during the Industrial Revolution in the 19th century, southern Italy has economically slogged along behind, becoming instead an epicenter for organized crime and corruption. Why? . . .

Southern Italy was never conquered by the Carolingian Empire and remained largely outside of the Holy Roman Empire. In fact, it wasn’t fully incorporated under the papal hierarchy until after the Norman conquests of the 11th and 12th centuries. Prior to this, Sicily had been under Muslim rule for roughly two and a half centuries, and much of the southern mainland had been under the control of the Eastern Empire and the Orthodox Church.

The imprint of this history can be seen in the prevalence of cousin marriages across Italian provinces in the 20th century . . . . In northern Italy, which has been largely under the Western Church since the MFP [Marriage & Family Program] began, the frequency of cousin marriage is less than 0.4 percent, and sometimes as low as zero. As we look south, rates of cousin marriage increase . . . .

Strikingly, the lower the prevalence of cousin marriage in a province, the higher the rate of voluntary blood donations to strangers. In southern Italy, including almost all of Sicily, the rates of blood donations are near zero. In some northern provinces, they reach 105 donations (16-ounce bags) per 1,000 people per year. . . .

Similar patterns emerge when we use real-world measures of people’s trust in impersonal organizations and strangers. Italians from provinces with more cousin marriage (1) use fewer checks, instead favoring cash; (2) keep more of their wealth in cash instead of putting it into banks, stocks, etc.; and (3) take more loans from family and friends than from banks. . . .

Corruption and Mafia activity reflect the same patterns seen for blood donations and impersonal trust. The greater the rate of cousin marriage in a province, the higher the rates of corruption and Mafia activity. There’s a reason why the Mafia is often referred to as ‘the family’ or ‘the clan’ and the boss is sometimes called ‘the godfather.’ The strength of in-group loyalty and the power of nepotism in societies with intensive kinship create precisely the kind of psychology and social relations that foster graft and fuel organized crime.”—Joseph Henrich, The WEIRDest People in the World: How the West Became Psychologically Peculiar and Particularly Prosperous (2020)