Polygyny
The term polygyny is used in related ways in social anthropology and sociobiology.
Definitions
In social anthropology, polygyny is a marital practice in which a man has more than one wife simultaneously. This is the usual form of polygamy. The man may marry more than one woman at the same time, or marry one or more other women while he is already married. The opposite form - polyandry - where a woman has more than one husband simultaneously, is much less common.
The anthropological meaning has been taken over into sociobiology, where polygyny refers to a mating system in which a male has a more or less stable breeding relationship with more than one female, but the females are only bonded to a single male. In eusocial insects it refers to situations where colonies have multiple queens.
Note that in both the human and the animal situations, either the male or the female may at times copulate with additional partners; "polygyny" describes the formal or persistent relationships that help structure the society rather than being an exhaustive description of actual behaviour.
Human polygyny
The majority of human societies have probably permitted polygyny. It was accepted in ancient Hebrew society, in classical China, and in Islam. It was accepted in many traditional African and Polynesian cultures. However, it was not accepted in ancient Greece or Rome, and has never been accepted in mainstream Christianity (early Mormonism was a notable exception). The political and economic dominance of (at least nominally) Christian nations from the sixteenth to the twentieth century has meant that on the world scale polygyny is legally recognised in very few nations. Although many Muslim majority countries still retain traditional Islamic law which permits polygyny, liberal movements within Islam continue to challenge its acceptability.
The Economy of Polygyny
Even where acceptable, for obvious reasons polygyny could never involve the majority of men, though it might involve the majority of women. Only the wealthy and politically powerful among men could afford to have more than one wife (or would be permitted to in many cultures, for example within Islam). Others may be lucky to have one wife or not be able to have any. This requires special social conventions if it is not to produce instability in the society. It is not, however, a unique problem of polygyny: some men (and women) never obtain mates in monogamous societies.
Stabilising conventions in polygynous societies
Since the number of human males and females born is approximately equal, if some men have more than one wife, that necessarily deprives other men from obtaining even one wife. The resulting imbalance tends to be corrected within polygynous societies by one or more of the following conventions:
- Men marry late (30+ years) and women marry early (mid teens, or earlier). This limits the number of men who can marry and prohibits the younger men from interfering. At the same time, because of mortality, the number of women available is always larger than the number of men seeking spouses. Some societies have formal age grades for males, and no man may marry until he succeeds into the highest grade. Younger age grades are used as a military force or for labor details.
- High male mortality from warfare, feuding, occupational accident, and disease. Not only are the men too involved in these activities to consider marriage, but the number arriving at the marriageable age is reduced. Again, this means that fewer men than females are marriageable.
- Bride price or bride service. Men are required to buy wives by presenting the bride's family with suitable and costly gifts, or carrying out long periods of work for them. Because bride prices are often collected by the groom's family, he will never be able to marry unless he has been obedient to their will, usually for a long period.
Modern Polygyny
Although polygynous marriages are not recognised in most modern societies, polygynous behaviour remains common. It survives through the use of mistresses and concubines, who are openly or secretly supported by wealthy males. In some cases the male may have a second (or more) family with the unofficial wife, supporting her and his illegitimate children. In some places the wife not only is aware of the husband's mistress, but helps him to select one that is "suitable" to his station.
The other form of modern polygyny is Serial Polygyny, sustained by divorces and remarriages that allow partners to experience multiple, legitimate relationships.
The Female in a Polygynous Marriage
The modern viewpoint adheres to the notion that polygyny degrades women, treating them as property and slaves. This is not a complete truism in a polygynous marriage, and is a criticism of monogamous marriages as well. Many polygynous marriages have shown considerable variability in the amount of influence and control multiple wives could command. Co-wives are able to support each other and help with "women's work." In cases of sororal polygyny (sisters marrying the same male), the close bonds have already been formed.
The Sociobiology of Polygyny
Polygyny is probably the most common mating system among vertebrates, and is especially common among mammals. It is characteristically associated with:
- Sexual dimorphism, particularly of size, with males being bigger, more aggressive, better equipped for fighting, and more colourful than females.
- Uniparental care of the young, with the males contributed less than the females or nothing at all
- Delayed sexual maturity among males, relative to females of the same species, or to males of related species with different mating systems.
Some species show facultative polygyny, with males mating with multiple females only when resource conditions are favourable. Recent research on voles has identified the genetic difference that predisposes one species to polygyny and another closely related species to pair bonding. The brain hormone mechanisms through which this very slight genetic difference acts have also been identified; they involve the response to vasopressin and oxytocin.
Considered in relation to other primates, humans are moderately sexually dimorphic, to an extent that a typical social group would be expected to consist of a male bonded to about three females. In reality, humans show much more flexibility in mating systems than most, perhaps all, other animals, and almost every possible kind of mating system exists in some society. However, the prevalence of polygyny in human societies combined with the biological evidence suggests that it may be the primitive form.
