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.
Polygyny offers husbands the benefit of allowing them to have more children, may provide them with a larger number of productive workers (where workers are family), and allows them to establish politically useful ties with a greater number of kin groups.
Senior wives can benefit as well when the addition of junior wives to the family lightens their workload.
In some of the sparsely populated regions where shifting cultivation takes place in Africa, women do much of the work.
This favours polygamous marriages in which men sought to monopolize the production of women "who are valued both as workers and as child bearers". Burton discuss and support Jack Goody's observation regarding African male farming systems in "Causes of Polygyny: Ecology, Economy, Kinship, and Warfare" where these authors note: "Goody (1973) argues against the female contributions hypothesis.
In such cases, the deceased man's heir may inherit his assets and wife; or, more usually, his brothers may marry the widow.
This provides support for the widow and her children (usually also members of the brothers' kin group) and maintains the tie between the husbands' and wives' kin groups.
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.
Both levirate and sororate may result in a man having multiple wives.