Plural marriage dating
Fraternal polyandry was traditionally practiced among nomadic Tibetans in Nepal, parts of China and part of northern India, in which two or more brothers would marry the same woman.
It is most common in societies marked by high male mortality.
For such reasons, senior wives sometimes work hard or contribute from their own resources to enable their husbands to accumulate the bride price for an extra wife.
Polygyny may also result from the practice of levirate marriage.
Anthropologist Jack Goody's comparative study of marriage around the world utilizing the Ethnographic Atlas demonstrated an historical correlation between the practice of extensive shifting horticulture and polygamy in the majority of sub-Saharan African societies.
The sororate resembles the levirate, in that a widower must marry the sister of his dead wife.
The family of the late wife, in other words, must provide a replacement for her, thus maintaining the marriage alliance.
Worldwide, different societies variously encourage, accept or outlaw polygamy.
Of societies which allow or tolerate polygamy, in the vast majority of cases the form accepted is polygyny.