Polyandry is much less popular than polygyny and is illegal in virtually every state in the world. Polyandry is believed to be more likely in societies with scarce environmental resources, as it is believed to limit human population growth and enhance child survival.
For example, in the Himalayan Mountains polyandry is related to the scarcity of land; the marriage of all brothers in a family to the same wife allows family land to remain intact and undivided.
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 in polygyny.
If every brother married separately and had children, family land would be split into unsustainable small plots.
In Europe, this was prevented through the social practice of impartible inheritance (the disinheriting of most siblings, many of whom went on to become celibate monks and priests).
In contrast, monogamy is marriage consisting of only two parties.The wife's family, in other words, must provide a replacement for her thus maintaining the ties between them.Both levirate and sororate may result in a man having multiple wives.For men, the benefits of polygyny are that it allows them to have more children, may provide them with more 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 their work load is lightened by the addition of junior wives to the family.