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Polygyny

Polygyny usually grants wives equal status, although the husband may have personal preferences. One type of de facto polygyny is concubinage, where only one woman gets a wife's rights and status, while other women remain legal house mistresses.

Although a society may be classified as polygynous, not all marriages in it necessarily are; monogamous marriages may in fact predominate. It is to this flexibility that Anthropologist Robin Fox attributes its success as a social support system: "This has often meant – given the imbalance in the sex ratios, the higher male infant mortality, the shorter life span of males, the loss of males in wartime, etc. – that often women were left without financial support from husbands. To correct this condition, females had to be killed at birth, remain single, become prostitutes, or be siphoned off into celibate religious orders. Polygynous systems have the advantage that they can promise, as did the Mormons, a home and family for every woman."

Nonetheless, polygyny is a gender issue which offers men asymmetrical benefits. In some cases, there is a large age discrepancy (as much as a generation) between a man and his youngest wife, compounding the power differential between the two. Tensions not only exist between genders, but also within genders; senior and junior men compete for wives, and senior and junior wives in the same household may experience radically different life conditions, and internal hierarchy. Several studies have suggested that the wive's relationship with other women, including co-wives and husband's female kin, are more critical relationships than that with her husband for her productive, reproductive and personal achievement. In some societies, the co-wives are relatives, usually sisters, a practice called sororal polygyny; the pre-existing relationship between the co-wives is thought to decrease potential tensions within the marriage.

Fox argues that "the major difference between polygyny and monogamy could be stated thus: while plural mating occurs in both systems, under polygyny several unions may be recognized as being legal marriages while under monogamy only one of the unions is so recognized. Often, however, it is difficult to draw a hard and fast line between the two."

As polygamy in Africa is increasingly subject to legal limitations, a variant form of de facto (as opposed to legal or de jure) polygyny is being practiced in urban centers. Although it does not involve multiple (now illegal) formal marriages, the domestic and personal arrangements follow old polygynous patterns. The de facto form of polygyny is found in other parts of the world as well (including some Mormon sects and Muslim families in the United States). In some societies such as the Lovedu of South Africa, or the Nuer of the Sudan, aristocratic women may become female 'husbands.' In the Lovedu case, this female husband may take a number of polygamous wives. This is not a lesbian relationship, but a means of legitimately expanding a royal lineage by attaching these wives' children to it. The relationships are considered polygynous, not polyandrous, because the female husband is in fact assuming masculine gendered political roles.

Religious groups have differing views on the legitimacy of polygyny. It is allowed in Islam and Confucianism. Judaism and Christianity have mentioned practices involving polygyny in the past, however, outright religious acceptance of such practices was not addressed until its rejection in later passages. They do explicitly prohibit polygyny today.