In social anthropology and sociobiology, polyandry (Greek: poly many, andras man) generally means a woman marrying more than one man.
In social anthropology, polyandry refers to a marital practice, a form of polygamy, which simply means "multiple spouses." Polyandry is the specific form of polygamy in which a woman has more than one husband simultaneously. Polyandry is less commonly encountered than polygyny, which refers to multiple wives. Polyandry is fairly common in Tibet (Polyandry in tibet ), Zanskar, Nepal, and Sri Lanka. It is also encountered in some regions of China (especially Yunnan), and in some Subsaharan African and American indigenous communities. With regard to these examples, it is important to bear in mind that the reference is to formally recognized marriage forms: there are no doubt those who live in de facto polyandrous arrangements that are not recognized by either law or custom. The anthropological classification and analysis of marriage forms begins with forms that are generally recognized by law or custom, and anthropologists are also interested in, but not concerned about the morality or suitability of, particular forms, conventional or otherwise.
The form of polyandry in which two (or more) brothers marry the same woman is known as fraternal polyandry, and it has been well established by many anthropologists that this is by far the most frequently encountered form. On the other hand, polyandry is a controversial subject among anthropologists. For instance, Pennsylvania anthropologist Stephen Beckerman points out that at least 20 tribal societies accept that a child could, and ideally should, have more than one father. On the other hand, in Tibet, which is the most well-documented cultural domain within which polyandry is practiced, the testimony of certain "polyanders" themselves is that the marriage form is difficult to sustain. Polyandry is practiced in few societies, has a high failure rate and is never the only accepted form of marriage.
With particular regard to the failure rate of polyandry, it is important to note that there are high rates of infidelity and divorce in Western and other "monogamous" societies, so that it is possible to argue that polyandry is not somehow uniquely unworkable. In Tibet, which is today controlled politically by the People's Republic of China, polyandry has been outlawed, which means that it is difficult to measure the incidence of polyandry in what had been the world's most "polyandrous" society. In other parts of the world, where polyandry was never as widepread as it was in Tibet, due to widespread Westernization via colonialism and imperialism, most traditional societies have been drastically altered or destroyed, so that the incidence of polyandry in the past may not be accurately known. In India, among Tibetan refugee groups who fled the Chinese invasion of their country, polyandry is seldom encountered.
Some forms of polyandry appear to be associated with a) the perceived need to retain aristocratic titles or agricultural lands within kin groups, and/or b) with frequent male absence, for long periods, from the household. As to the former variety, consider that in Tibet where the practice is particularly popular among the wealthy Sakya priestly nobility as well as poor small farmers who could ill afford to divide their small holdings. As to the latter variety, as some males return to the household, others leave for a long time, so that there is (was) usually one husband present.
The term has been taken over into sociobiology, where it refers, analogously, to a mating system in which one female forms more or less permanent bonds to more than one male. It can take two different forms. In one, typified by the Northern Jacana and some other ground-living birds, the female takes on much the same role as the male in a polygynous species, holding a large territory within which several males build nests, laying eggs in all the nests, and playing little part in parental care . In the other form, typified by the Galapagos Hawk , a group of two or more males (which may or may not be related) and one female collectively care for a single nest. The latter situation more closely resembles typical human fraternal polyandry. These two forms reflect different resource situations: polyandry with shared parental care is more likely in very difficult environments, where the efforts of more than two parents are needed to give a reasonable chance of rearing young successfully.