Polygyny is the system under which a man is married to two or more wives at the same time; it includes bigamy which is the (usually illicit) marriage to two women; and where polygamy is forbidden under the law, it can take the form of cohabitation with many women. As well as being discriminatory against women, men who cannot afford the bride-price and therefore cannot wed, can also be perceived as victims of this nuptial practice. Although polygyny ensures the birth of many children, as well as an additional supply of labour (both of which contribute, in traditional societies, to the wealth and prestige of the family), in a changing society it causes a strain on economic resources and can be a barrier to population control.
Polygamy in its traditional form occurs mainly in Africa, although concubinage still exists in Asia. Harems exist in Arabia and the Middle East but the Muslim law of taking up to four legal wives is much less followed in current practice, particularly because of the cost. It has been abolished in certain countries (Tunisia, Turkey), and severely restricted elsewhere (Pakistan, Egypt). But the rich in both Asia and Arabia continue to keep harems and this encourages traffic in women and children, particularly to Arabia. Bigamy occurs in isolated cases throughout developed society. A feature of the Mormon religion used to be polygamy, but the practice was outlawed in 1896 as a condition for Utah to become a state in the USA.
Nor did Christ Our Lord wish only to condemn any form of polygamy or polyandry, as they are called, whether successive or simultaneous, and every other external dishonorable act, but, in order that the sacred bonds of marriage may be guarded absolutely inviolate, He forbade also even willful thoughts and desires of such like things: "But I say to you, that whosoever shall look on a woman to lust after her hath already committed adultery with her in his heart." (Papal Encyclical, Casti Connubii, 31 December 1930).
Even with equal numbers of men and women in a society, there is always more marriageable women than men because women mature and marry earlier. Therefore polygamy provides full adult status in a traditional society for as many women as possible.
Serial polygamy is practised in most developed nations through the practice of divorce and remarriage or cohabitation and separation.