Polygyny and polyandry — anthropology and contemporary law

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The Murdock distribution

George Murdock's Ethnographic Atlas, the standard cross-cultural database, reports that of roughly 1,231 societies coded, about 84.6 percent permit polygyny in some form, 15.1 percent are monogamous, and only 0.3 percent — four societies — permit polyandry. Among societies permitting polygyny, actual practice varies: in many, only the wealthy or chiefly take multiple wives, and the median man has one. Still, the statistical dominance of permissive polygyny across the human record is overwhelming, and any cross-cultural theory of marriage has to start there.

Scheidel on Greco-Roman monogamy

Walter Scheidel's analysis of Greco-Roman monogamy argues that the strict legal monogamy of Greek and Roman elite culture was a striking historical anomaly. Surrounded by polygynous Mesopotamian, Persian, and Hellenistic neighbors, the Greek polis and the Roman Republic imposed legal monogamy on their citizens. The institution spread through Christianity and Roman law into medieval Europe, where it co-evolved with property primogeniture and church-enforced marital discipline. Scheidel argues this constraint on elite male mating was one of the institutional preconditions for European state formation, by reducing intra-elite mating competition and broadening the marriageable pool for non-elite men.

Henrich and the cooperative-monogamy hypothesis

Joseph Henrich and colleagues have argued that socially imposed monogamy, by reducing the pool of unmarried low-status men, also reduces violence, crime, and political instability. Their cross-cultural and longitudinal analyses link the imposition of monogamy on elite men to lower homicide rates, higher savings, and stronger paternal investment. The hypothesis is controversial — critics note confounders and selection effects — but the underlying mechanism is plausible and rooted in evolutionary mathematics. Where polygyny is permitted, the variance in male reproductive success rises, and so does competition among the unsuccessful.

Tibetan fraternal polyandry

In parts of the Tibetan plateau, Ladakh, and Nepal, brothers traditionally share a single wife in a household that holds undivided land. The arrangement preserves the agricultural plot across generations, retains household labor (since brothers do not split off to form competing households), and matches the demanding ecological reality of high-altitude farming. Nancy Levine's ethnography of Nyinba polyandry documents the practice in detail, including the genuine tensions and the women's significant role. The system declined sharply in the late 20th century as land scarcity eased, alternative livelihoods emerged, and external legal and moral pressure mounted against it.

The Mosuo walking-marriage system

The Mosuo of southwestern China, often described as a "matrilineal" or "matriarchal" society, practice a form of relationship called sese or "walking marriage": women have visiting partners who come to their household at night and return to their own household by day. Children belong to the mother's family. The arrangement is not exactly polyandry — partnerships can be exclusive — but it institutionalizes serial and sometimes concurrent female partner choice in a way no other large society does. The system is under stress from Chinese state pressure, tourism, and economic change, but it persists.

Mormon fundamentalist polygyny in Bennion's ethnography

Janet Bennion's long-term fieldwork in fundamentalist Mormon polygynous communities — the Allred group, the FLDS, and others — documents women's lives inside the institution. She finds substantial female networks and solidarity among sister-wives, real religious meaning for many participants, and significant economic precarity due to large household sizes and limited labor-market participation. She also documents coercion, especially of young women pressured into marriages with much older men, and the practice of expelling young men ("Lost Boys") to maintain the gender ratio. Her work refuses the simple narratives in either direction and is the best source on contemporary Western polygyny.

Islamic polygyny and its modern restrictions

Classical Islamic law permits a man up to four wives, conditioned on his ability to treat them equitably. Modern Muslim-majority states have introduced varying restrictions: Tunisia bans polygyny outright; Turkey banned it in 1926; Morocco and several Gulf states require court permission and the first wife's consent; Indonesia requires similar approvals. The practice has declined sharply across most of the Muslim world even where legal, with urban educated populations largely monogamous in practice. The institution survives most strongly in rural and economically polarized regions, often correlating with wealth disparity and traditional religious networks.

Sub-Saharan African polygyny patterns

Polygyny remains widespread in Sahelian and West African societies, with rates above 30 percent of married men in several countries. The practice is often justified by labor needs in agricultural and pastoral economies, by Islamic permission, or by customary law. Urbanization, female education, and economic change are eroding the institution slowly. African feminist scholars are divided on the question: some see polygyny as inherently coercive; others see it as a survivable institution that needs reform rather than abolition. The diversity within Africa undermines any single narrative.

The unmarriageable man problem under polygyny

Mathematically, if some men have multiple wives, an equal number of other men have none. In strongly polygynous societies, this surplus of unmarried males correlates with raiding, mercenary recruitment, religious militancy, and outward migration. The phenomenon has been documented from Plains Indian young men's warrior bands to contemporary Saudi unemployed bachelors. The Mormon Lost Boys, expelled from fundamentalist communities to maintain the polygynous ratio, are a modern microcosm. Any society contemplating expanded polygyny law has to address what happens to the men at the bottom of the resulting distribution.

The Western legal status

Most Western countries criminalize bigamy, but enforcement is selective. Plural cohabitation, religious ceremonies without legal registration, and serial divorce-and-remarriage produce de facto plural households that the law tolerates. The 2013 Brown v. Buhman decision in Utah struck down portions of the state's anti-cohabitation law, effectively decriminalizing religious polygyny without legalizing plural civil marriage. Canada upheld its anti-polygamy law in a 2011 reference, citing harms to women and children. The legal terrain is unstable, and the rise of "polyamory" advocacy among secular Westerners is opening new pressure on the monogamous default.

Polyamory as a different category

Contemporary polyamory — consensual non-monogamy with multiple partners of various genders — is structurally different from historical polygyny. It is typically egalitarian in principle, not patriarchal; it does not assume one central partner with several subordinate ones; it includes both polygynous and polyandrous configurations as well as more complex networks. Empirical research on polyamorous relationships is young, with small and self-selected samples reporting relatively high satisfaction but also frequent instability. Whether polyamory scales to a population-level institution or remains a subcultural practice for high-communication, high-resource adults is unsettled.

Partible paternity in Amazonia

Several Amazonian societies — including the Bari and the Aché — recognize the concept of partible paternity, in which a child can have multiple biological fathers if the mother had sexual relations with several men during pregnancy. The named fathers all contribute to the child's upbringing. The institution is not exactly polyandry, since it does not constitute a formal multi-husband household, but it institutionalizes a similar reproductive logic. Sarah Hrdy's analysis of cooperative breeding and shared paternal investment treats partible paternity as one solution to the high cost of human child-rearing, achieved by spreading paternal certainty across multiple men.

The honest collective trade-off

Modern legal monogamy is not natural law, but it is not arbitrary either. It distributes marital opportunity more evenly than permissive polygyny does, at the cost of criminalizing some consenting arrangements. Permissive plural marriage respects autonomy at the cost of producing predictable concentration effects in the marriage market. A society that wants to think clearly about its own marriage law has to acknowledge both sides honestly: monogamy is enforced not because plural marriage is unnatural — it is the historical norm — but because the population-level externalities of permissive polygyny are real and worth preventing. Whether the trade-off remains worth it under changing demographic, economic, and cultural conditions is a question each generation has to answer. The 21st century is currently answering it inconsistently, and the inconsistency itself is a sign that the collective has not yet thought the question through.

Citations

1. Murdock, George Peter. Ethnographic Atlas: A Summary. Pittsburgh: University of Pittsburgh Press, 1967. 2. Scheidel, Walter. "Monogamy and Polygyny." In A Companion to Families in the Greek and Roman Worlds, edited by Beryl Rawson, 108–115. Malden, MA: Wiley-Blackwell, 2011. 3. Henrich, Joseph, Robert Boyd, and Peter J. Richerson. "The Puzzle of Monogamous Marriage." Philosophical Transactions of the Royal Society B 367, no. 1589 (2012): 657–669. 4. Bennion, Janet. Polygamy in Primetime: Media, Gender, and Politics in Mormon Fundamentalism. Waltham, MA: Brandeis University Press, 2012. 5. Bennion, Janet. Women of Principle: Female Networking in Contemporary Mormon Polygyny. New York: Oxford University Press, 1998. 6. Levine, Nancy E. The Dynamics of Polyandry: Kinship, Domesticity, and Population on the Tibetan Border. Chicago: University of Chicago Press, 1988. 7. Hrdy, Sarah Blaffer. Mothers and Others: The Evolutionary Origins of Mutual Understanding. Cambridge, MA: Belknap Press, 2009. 8. Westermarck, Edward. The History of Human Marriage. 5th ed. London: Macmillan, 1921. 9. Fisher, Helen. Anatomy of Love: A Natural History of Mating, Marriage, and Why We Stray. Rev. ed. New York: W. W. Norton, 2016. 10. Hudson, Valerie M., and Andrea M. den Boer. Bare Branches: The Security Implications of Asia's Surplus Male Population. Cambridge, MA: MIT Press, 2004. 11. Vemsani, Lavanya. Modern Hinduism in Text and Context. London: Bloomsbury Academic, 2019. 12. Cherlin, Andrew J. The Marriage-Go-Round: The State of Marriage and the Family in America Today. New York: Knopf, 2009.

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