Final answer:
Polygyny involves one man with multiple wives and is common, with social and economic advantages such as larger workforces and extended kinship ties. Polyandry, where one woman has multiple husbands, is much rarer. Monogamy, the union of two adults, is well-suited to modern societies and includes same-sex marriages.
Step-by-step explanation:
There are several types of marriages that are recognized around the world, each with its own defined structure and societal role. Polygyny is the most common form of polygamy and it involves one man being married to more than one woman simultaneously. In these relationships, there is often a significant age disparity, where husbands are older than their multiple wives. Economic and social advantages of such arrangements involve maximized labor forces and expanded kinship networks.
Polyandry is significantly less prevalent, identified by one woman being married to more than one man at the same time. It accounts for about 1% of the world's cultures and is seen as an outlier compared to other forms of marriage.
Monogamy is the marriage between two adults and is the most adaptable to postindustrial societies where smaller family units are more suitable. It includes different forms such as same-sex marriage, legally recognized in various countries around the world including the United States after the Obergefell v. Hodges ruling in 2015.