After years of childlessness, one of the most important biblical wives encouraged her husband to take another woman into his bed. In the Old Testament book of Genesis, Sarah, who was barren, suggested that her husband, Abraham, should take her maid, Hagar, as a second wife or concubine so that they could have a son. Abraham did, and Hagar bore Ishmael. Sarah then went on to bear a son, Isaac, with Abraham. The dynamics of this plural marriage became complicated, yet they also brought much-loved offspring, thus peopling the world. This situation has implied that polygamy could be, and indeed was, blessed. The tale has resonated for millennia as both a story of lived experience and an organizing mythology.

The ancient Israelite practice of polygamy echoes in other forms in various parts of the ancient and medieval world, from six continents. There were distinct iterations of polygamy in diverse political and social contexts. Overall, though, polygamy allowed for resource-building, diplomatic links, and the creation of significant networks. It was vital in numerous situations of royal power, linking the center with the regions under its control. It depended on the labor, and the endurance, of women, who were central to men’s ability to mobilize people and resources. Moreover, it had implications for demographic growth, for the spacing of births by wives, and for the replacement of populations of men lost through war.

. . .

Senior women often had an important role in Chinese households, too, especially royal ones. In its long history, China has had a generally consistent system of formal monogamy, but with a range of concubines and “maids” allowed, even encouraged, for prosperous men. The emperor could take only one wife, but he was supposed to have multiple consorts. One second-century ruler, Sun Quan of the kingdom of Wu, was an impressive leader with a fatal flaw. He failed to distinguish between his wife and concubines; the resulting domestic chaos made him a laughingstock. Although Chinese emperors were expected to sire numerous offspring, they were not supposed to enjoy it too much; such self-indulgence was suspect in Confucian teachings. Keeping favorites, too, could be a problem. In the sixth century, the Chen emperor was supposedly so preoccupied with his favorite concubine, who sat on his lap during court business, that he lost his dynasty to attacking Sui warriors. In the sixteenth century, courtiers reminded Xianzong, the Ming emperor besotted with his favorite: “Having sons depends on there being many mothers.” An empress was expected to preside over these various mothers with grace and authority. In the third century, Jin Emperor Wu received concubines from conquests, but they were vetted by the empress herself. The ancient Mao commentary praised an empress who not only avoided jealousy but also created harmony among the concubines. Wives had formally recognized children with the emperor, but so did consorts. Consorts could come from a range of backgrounds, but they and their children could rise high. In fact, the mothers of the Yongzheng, Qianlong, and Jiaqing emperors had all been bondservants.

The politics of polygamy played out differently in other settings, but here, too, there were tight connections between royal power and polygamy. In Siam, in what is now Thailand, the ruler had the authority to instigate polygamy for himself and others in the medieval and modern eras. Classic Thai Buddhist texts celebrated the potency of rulers and their plural wives, as in the Trai Phum Phra Ruang, a cosmology attributed to the fourteenth-century King Ruang. There was no word for polygamy in the Thai language, but the concept exists as “the principle of having many wives simultaneously.” The Family Code of 1361 enshrined this principle, recognizing four legal types of wives. The first group of wives, in marriages brokered by the king himself, had the highest rank. The next category of wives were those given by their parents in protracted negotiations that preserved their inheritance and rights in the event of death or marital breakdown. The third type were those married through personal choice, lacking the family protection of the second category. The fourth and lowest-ranking wives were enslaved ones, who had little by ways of rights to inheritance or property or child custody in the event of any problems. These categories of wives mattered in terms of legal outcomes and in terms of the dynamics of these households, organizing hierarchies among the wives in these plural marriages. Enslaved wives were subject to the will and whim not only of the husband but also of other wives.

. . .

Royal power showed itself in polygamy in early modern Incan, or Cuzco, society, in what is now Peru as well. Wives had vital economic and reproductive roles. One Spanish Jesuit, Bernabé Cobo, declared that “the possession of many wives was a sign of greatness and wealth among them. Only the commoners make do with one wife.” In a typical European claim, Cobo went on to note that “the wives serve their husbands like slaves. They do most of the work, because besides bringing up the children, they cook, make chicha [a fermented ceremonial drink] and all the clothing they, their husbands, and their children wear, and they even do more work in the fields than the men.” Since such assertions functioned as a way to criticize the gender and political regimes of indigenous people, it is important not to take them literally. Still, women’s contributions were considerable.

These Native American plural wives had diplomatic and political significance as well. In one of the starkest connections of polygamy and political power, only the ruler of the Cuzco, the Inca himself, had the authority to confer secondary wives on a man. This royal privilege was grounded in the mythology of the empire, as origin stories conveyed that the first Inca, Maco Capac, had received secondary wives from all the nations he had invaded. In other words, polygamy could exist only where the state directly sanctioned and encouraged it, and it was often a form of tribute to the Inca.

. . .

Royal power in the early modern kingdom of Buganda in east Africa also increasingly intertwined with polygyny in this same era. Here, as elsewhere, political power rested on wives. Kings linked themselves to multiple territories, including newly conquered ones, through polygamous marriages. People presented wives to the king as marks of respect or to accompany a request or to obtain forgiveness of a debt or transgression. Clans and family members established themselves by giving their women to the king’s household, with a few to perform specific intimate tasks.

. . .

Plural marriages also established rule in more modern times among indigenous people in the Pacific Islands, including what is now Australia, New Zealand, and Papua New Guinea. One nineteenth-century missionary in New Guinea observed that “a man may have as many wives as he can afford,” with headmen having up to six. This missionary lamented what he saw as the lack of harmony in polygynous families, recounting tales of conflict connected with jealousy over a favored wife. These problems threatened the whole social order: “nine-tenths of the quarrels in New Britain arise from jealousy of the women…[and] conjugal mistrust.” Imperial authors blamed indigenous polygamy and domestic rivalries for wider violence, conveniently ignoring their own settler colonialism and missionary activities. Even among European observers, though, there were accounts emphasizing domestic tranquility. Another British observer of the Māori in New Zealand was more positive, claiming that polygamy increased the power of rulers, but that all the spouses lived together in harmony. He conceded that “the sudden bringing home of a new wife, which sometimes happened (perhaps a slave, or from a distance)…made quite a sensation among the old wives, but it was only temporary. Often the old wives themselves encouraged their husband to take another, and aided efficiently in doing so. This statement suggests that wives could come from various backgrounds, including war, captivity, and diplomacy, a pattern found in numerous settings. It implies, too, that women had agency in the choosing of new wives and that they did not necessarily see them as a threat or simply a source of jealousy.

Harmonious and in fact helpful relations between wives have sometimes been the norm among indigenous people in the Pacific world, as more recent examples suggest. The Martu of Australia’s Western Desert have long practiced polygyny, though there, as elsewhere, it is difficult to ascertain much about its roots. Marriages could be arranged, often at or shortly after birth, with family and kin networks paramount in marital decisions. Polygyny could be sororal, so that a man married multiple sisters.

. . .

By contrast, European practices of polygamy, rarely involving sisters, seem to have been less friendly. Although it is often forgotten, polygamy was a long-standing practice of powerful European kings. The ancient Roman commentator Tacitus claimed that a few Germanic kings took multiple wives not because of “lust” but because of their need for political alliances and as a way to enhance their power. The lines between wife, secondary wife, and concubine could be thin, with certain kinds of unions receiving more formal recognition.

. . .

Medieval Irish kings, too, could have plural wives. By the eighth century, there were debates in legal texts about whether it was acceptable for Irish Christians to “live in plurality of unions,” with citations of the Old Testament polygamy of Solomon, David, and Jacob. These references imply long-standing Irish traditions of polygamy. There was clear endorsement in certain circles of a man taking a second wife if his first could not have children; moreover, there seems to have been political polygamy to knit together various kingdoms and communities. Other legal texts distinguished between two major types of wives: a primary wife, who ran the household, and a “betrothed” or secondary wife, who was her subordinate.

. . .

Yet, as this story of the Irish king suggests, the practice of polygamy never won the approval of the Catholic Church, no matter how powerful a few of its practitioners were. Numerous societies allowed both polygamy and monogamy as forms of union; usually, the former was the practice of the wealthy and powerful. Increasingly, the systems allowing both kinds of unions would come into contact with those in which monogamy was considered the only acceptable option. To understand the complexities of these encounters, it is useful to turn to the history of polygamy in the three great monotheistic religions: Christianity, Judaism, and Islam.