Polygyny

• 1. Introduction

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  Polygyny, the practice of a man marrying multiple women at once, is not a relic of ancient history. It shapes the daily lives of roughly 11 percent of the population of sub-Saharan Africa today. In West Africa, more than one-third of women are married to a man who has more than one wife. In Burkina Faso, the figure reaches 36 percent. And yet in the same decade, a court in Ingushetia struck down its own government's edict permitting polygynous marriages because it contradicted national family law.

  This is a practice found in ancient Hebrew society, classical China, Polynesian cultures, and among some Mormon sects in twenty-first-century America. It has been defended by scholars, condemned by philosophers going back nearly eight centuries, and debated in parliaments from Kyrgyzstan to Nigeria. It sits at the intersection of economics, religion, public health, and the law.

  How did this marriage system become so deeply embedded in particular societies? What does the research actually show about its effects on women, on children, and on political stability? And why do countries as different as Somalia and South Africa handle it in such starkly different ways?

• 2. The Polygamy Belt

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  Burkina Faso, Mali, and Gambia sit at the top of every global measure of polygyny prevalence, and together with Niger and Nigeria they form the core of what researchers call the "polygamy belt" of West Africa and Central Africa. As of 2019, Burkina Faso recorded a rate of 36 percent, Mali 34 percent, and Gambia 30 percent. Outside Africa, the highest rates appear in Afghanistan, Yemen, and Iraq.

  Ester Boserup was the first scholar to propose a structural explanation for why sub-Saharan Africa specifically became the world center of this practice. Writing in 1970, she argued that the sexual division of labor in hoe-farming was the key. In regions of shifting cultivation, men and older boys typically fell trees, fenced fields, and sometimes planted crops, while wives handled cultivating, food processing, preparing meals, and domestic duties. Women's contribution was larger in total hours, Boserup found, yet they received a smaller share of the economic rewards.

  For a man with several wives, the arithmetic was direct. A 1930s study of the Mende in Sierra Leone concluded that a plurality of wives is an agricultural asset, making it unnecessary to hire wage laborers. The United Nations Economic Commission for Africa's secretariat put it plainly: one of the strongest appeals of polygyny to men in Africa is its economic aspect, because a man with several wives commands more land, produces more food, and achieves higher status through the wealth he can command.

  Anthropologist Jack Goody complicated Boserup's account by pointing to the West African savanna, where more agricultural work is done by men than women, yet polygyny rates are especially high. Goody quoted his own earlier work: "The reasons behind polygyny are sexual and reproductive rather than economic and productive," arguing that men in these systems marry polygynously to maximize fertility and build large households of young dependent males.

  A 2012 analysis by James Fenske found a third driver: child mortality. Areas with higher child mortality rates also had higher polygyny rates, and the correlation was stronger than the link to female agricultural contributions. Where children frequently die young, having more children matters more, and polygyny is one mechanism to pursue that goal.

• 3. Laws, Customs, and Loopholes

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  Nigeria operates under three legal systems simultaneously: Nigerian common law, Sharia law, and customary law. Under customary law, there is no upper limit to the number of wives a man may legally marry. Under Sharia, the cap is four, provided each wife is treated equally. Christians are generally expected to be monogamous. Research conducted in Ibadan, the second largest city in Nigeria, found that non-educated women are 58 percent more likely to be in a polygynous union, compared to just 4 percent of college-educated women.

  Malawi offers a different model. Polygynous marriages are not legally recognized under civil law there, yet customary law grants them substantial practical rights, including inheritance and child custody. Nearly one in five women in Malawi lives in such a relationship. An effort led in 2008 to outlaw polygyny was fiercely opposed by Islamic religious leaders, who cited it as a cultural, religious, and practical reality of the nation.

  South Africa permits polygynous marriages under the Recognition of Customary Marriages Act, and the practice has been associated publicly with figures including former President Jacob Zuma. But Islamic polygynous unions in South Africa occupy a legal grey area: they are not officially recognized at the national level, even as Islamic law encourages Muslim men to take up to four wives. After 1994, a series of legal instruments, including the UN Convention on the Elimination of All Forms of Discrimination Against Women, began to pressure that ambiguity.

  Australia offers the sharpest contrast. Under the Marriage Act of 1961, section 94, knowingly marrying a person who is already legally married constitutes bigamy, carrying a penalty of up to five years of imprisonment. On the 6th of March 2016, the Full Court of the Family Court of Australia ruled explicitly that polygamous marriages are illegal. The court did, however, recognize a category it called a "potentially polygamous marriage," one conducted in a country whose laws permit future additional spouses, even if no additional spouse has been taken yet.

• 4. Economics of Marriage

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  Economist Michèle Tertilt reached a conclusion that runs counter to the intuition that larger households mean more prosperity. Countries that practice polygyny tend to have higher fertility rates, fewer savings reserves, and lower GDP. A 2014 study estimated that if polygyny were banned, fertility would fall by 40 percent, savings would rise by 70 percent, and GDP would increase by 170 percent. The mechanism Tertilt identifies is behavioral: monogamous men invest more in their families and broader institutions, while polygynous men concentrate their resources on competing for additional wives.

  Yet a 1995 study found that men in polygynous marriages gain something the raw GDP figures miss: a large network of in-laws provides social and economic insurance that compensates for other shortfalls. With ties to multiple kinship groups, these men can draw on a wider support system when other resources fail.

  Bride price, the payment a groom or his family makes to the bride's family, ties these economic calculations together. Polygyny is more common in societies with the bride price custom. Boserup documented how, through the labor and agricultural contribution of several wives, a husband could generate enough surplus to pay the bride price for a new wife, expanding both his land access and his progeny. In practice, feminist critics note, this creates a trap: women who want to leave a polygynous marriage must repay their bride price, and husbands frequently keep that price at a level that is practically unpayable.

• 5. Health and Conflict Among Co-Wives

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  Studies of the Ngwa group in eastern Nigeria found that women in polygynous unions are, on average, 22 to 26 percent less fertile than women in monogamous ones. The deficit grows with wife order: first wives show a 15 percent fertility deficit relative to monogamous women; second wives, a 37 percent deficit; and third or later wives, a 46 percent deficit. Researchers attribute this partly to the widening age gap between a husband and each successive wife, and partly to decreased frequency of intercourse.

  Among the Logoli of Kenya, interviews revealed that fears about HIV infection specifically shape women's decisions about entering polygynous marriages. The research shows two mechanisms that elevate HIV risk in these unions: partners in polygynous households have more extramarital relationships, increasing each other's exposure; and women recruited into a polygynous marriage are more likely to already be HIV positive than those who marry a monogamous husband. In Malawi, studies found that HIV prevalence among people in polygynous marriages runs between 10 and 15 percent, in a country where approximately 14 percent of the total population is infected.

  The reported emotional environment within polygynous households is frequently characterized by jealousy, competition, and psychological stress. Research shows conflict between co-wives can intensify to the point where women commit suicide due to psychological distress. According to Bove and Valeggia, senior wives in some countries exploit their position to obtain healthcare benefits that are only available to one wife per household, leaving junior wives without access.

  Some societies have developed structural responses to these tensions. Sororal polygyny, in which co-wives are sisters, is used in some communities to reduce jealousy. Hut polygyny, in which each wife has her own residence and the husband visits in rotation, provides physical separation. A clear status hierarchy that specifies each wife's rights and obligations serves a similar function, though it does not eliminate the underlying inequalities.

• 6. Violence, Instability, and Young Men

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  In the 2017 Fragile States Index, polygyny is widely practiced in nineteen of the top twenty ranked countries. A study of 240,000 children across 29 African countries found that, after controlling for other variables, children in polygynous families were more likely to die young. A 2019 study of 800 rural African ethnic groups, published in the Journal of Conflict Resolution, found that young men in polygynous societies feel they are treated more unequally and are readier to use violence than those in monogamous groups.

  The connection to organized political violence is explored in a 2011 doctoral thesis by anthropologist Kyle R. Gibson, who reviewed three studies covering 1,208 suicide attacks from 1981 to 2007. Countries with higher polygyny rates correlated with greater production of suicide terrorists.

  Political scientist Robert Pape found that among Islamic suicide terrorists, 97 percent were unmarried and 84 percent were male. A study conducted by the U.S. military in Iraq in 2008 found that suicide bombers were almost always single men without children aged 18 to 30, with a mean age of 22, and were typically students or employed in blue-collar occupations.

  Cognitive scientist Steven Pinker, in his 2011 book The Better Angels of Our Nature, draws on research showing that 99 percent of Palestinian suicide terrorists are male, that 86 percent are unmarried, and that 81 percent have at least six siblings. Citing research by anthropologist Scott Atran on payments to families of suicide terrorists, Pinker argues that in societies where bride prices are unaffordable and many potential brides end up in polygynous marriages, the financial compensation attached to suicide terrorism can fund enough marriages for a man's brothers to make the act seem rational in terms of what Pinker calls kin selection. He invokes a quotation attributed to evolutionary biologist J. B. S. Haldane, who reportedly quipped that he would not die for his brother but would for "two brothers or eight cousins."

• 7. Religion and Doctrine

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  Thomas Aquinas, writing nearly eight centuries ago, argued that polygyny is unjust to wives and children. He contended that it creates rival stepchildren forced to compete for attention, food, and shelter, and that it violates the requirement of fidelity between spouses. His critique remains a foundation of Roman Catholic teaching: paragraph 2387 of the Catechism of the Catholic Church states that polygamy "is not in accord with the moral law," while paragraph 1645 calls it contrary to conjugal love.

  Martin Luther took a more permissive position. In a document known as Der Beichtrat, he granted Philip of Hesse, Landgrave of the Holy Roman Empire, a dispensation to take a second wife, on the condition that the marriage remain secret to avoid public scandal. In a letter to the Saxon Chancellor Gregor Brück, Luther stated that he could not "forbid a person to marry several wives, for it does not contradict Scripture." The Lutheran Church in Liberia later allowed polygynists who converted to Christianity to retain existing wives, while prohibiting them from taking new ones after baptism.

  Islam permits up to four wives, based on verse 4:3 of the Quran, subject to the condition that all wives are treated justly and provided for equally. Muhammad was monogamously married to Khadija for 25 years until her death, after which he married multiple women, mostly widows, for social and political reasons, and had a total of nine wives over his lifetime, though not all simultaneously. In most Muslim-majority countries polygyny is legal, with Kuwait the only one that imposes no restrictions. Turkey, Tunisia, Albania, Kosovo, and the Central Asian countries prohibit it.

  In the Ashkenazi Jewish tradition, polygyny has been banned since a ruling by Gershom ben Judah in the 11th century. Some Mizrahi communities, including Yemenite and Persian Jews, discontinued the practice only after immigrating to countries where it was forbidden. Israel prohibits new polygamous marriages for all its citizens, though existing ones may be maintained.

• 8. Polygyny in Nature

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  In zoology, polygyny describes a mating pattern in which a single male has multiple female mates within one breeding season. Males typically secure mates through one of two strategies: defending the females directly, or controlling the resources those females need.

  The European wool carder bee, Anthidium manicatum, is a well-documented example of resource defense polygyny. Males claim patches of flowering plants, drive off rival males and other competitors, and mate with the multiple females who forage within those territories.

  Among eusocial insects, polygyny takes a colony-wide form. In primary polygyny, multiple queens cooperate to found a new colony, but after the first workers hatch the queens fight until only one remains, making the colony monogynous. In secondary polygyny, an established colony continues to maintain several queens simultaneously. Red flour beetles use polygyny specifically to reduce inbreeding depression, widening the genetic pool to improve reproductive success across the colony.