Anthropologists group marriage customs into two primary types: a union of two spouses only (monogamy) or a union involving more than two spouses (polygamy). Monogamy is the socially sanctioned union of two adults. In some societies this union is restricted to a man and a woman, and in other societies it can be two adults of any gender. Monogamy, because it produces an overall smaller family unit, is especially well adapted to postindustrial societies and cultures where family units are highly mobile (such as nomadic foragers). Monogamy also includes same-sex marriage. In June 2015, in Obergefell v. Hodges, the US Supreme Court legalized same-sex marriage in the United States, following earlier legal recognitions in many other Western countries. Today, same-sex marriage is legal in 30 countries. While the movement to legalize same-sex marriage has been long and tumultuous in many of these countries, same-sex marriages and unions have historically played significant roles in both Indigenous and Western societies. Serial monogamy: Serial monogamy is a form of monogamy in which adults have a series of two-person monogamous marriages over a lifetime. It is increasingly common in Western societies, but it is also practiced in some small-scale societies, such as bands. In serial monogamy, divorce and remarriage are common. Polygamy: Polygamy is the socially sanctioned union of more than two adults at the same time. In polygamous societies, families usually begin with a two-person marriage between a man and a woman. In some cases, the marriage will remain as a single couple for a long period of time or for the duration of their lives because of lack of resources or availability of partners. Adding partners is frequently a sign of status and is considered an ideal for families in polygamous societies. In some cases, too, polygamy is practiced to address extreme social stress due to things such as warfare or skewed population distributions caused by famine and high mortality rates. In her cross-cultural study of polygamy, cultural anthropologist Miriam Zeitzen (2008) noted a great deal of diversity within polygamy, from de jure unions that are formal, legal contracts (such as is found in Gambia) to de facto polygamy, which may be just as enduring, stable, and acceptable within a society (such as is found in Ivory Coast). Figure 11.15 In a polygynous marriage, there is one husband and more than one wife. This is the cast of Sister Wives, a television series about a polygamous household in the United States. (credit: “Sister Wives Cast on Valder Beebe” by Valder Beebe Show/Wikimedia Commons, CC BY 3.0) There are two principle kinds of polygamy, depending on the partners involved, as multiple men and multiple women in a single marriage (called group marriage) is not common. Polygyny, which is the more common form of polygamy, is the marriage of one man to more than one woman. There is often marked age asymmetry in these relationships, with husbands much older than their wives. In polygynous households, each wife commonly lives in her own house with her own biological children, but the family unit cooperates together to share resources and provide childcare. The husband usually “visits” his wives in succession and lives in each of their homes at various times (or lives apart in his own). It is common, also, for there to be a hierarchy of wives based on seniority. Polygyny is found worldwide and offers many benefits. It maximizes the family labor force and the shared resources and opportunities available for family members and creates wide kinship connections within society. Commonly in polygynous societies, larger families are afforded higher social status and they have stronger political and economic alliances. Polygyny is prevalent in Thailand today, with as many as one in four Thai men between the ages of 30 and 50 having a second wife, called a mia noi (minor wife). In her research in Thailand, cultural anthropologist Jiemin Bao (2008) studied polygyny among a group of lukchin Thai (Thai of Chinese descent). She found that the lukchin practiced polygynous marriages as a joint husband-and-wives economic enterprise, many times sending remittances back to family members still living in China. Bao found that husbands frequently seek their wives’ consent before adding another wife and that the family overall considers polygyny to create greater economic opportunities for all family members because multiple wives create a pool of stable laborers with individual skill sets. Even so, Bao observed turmoil and conflict even within economically successful polygynous families and observed that many marriages were conducted as if they were “cutting a business deal” (151). Gender politics of polygynous marriage among the lukchin often left women with few choices except to work for her husband’s family. Economic success for the family was culturally attributed to the male head of household and not his wives. A second form of polygamy is polyandry. In polyandry, which is comparatively rare, there is one wife and more than one husband. Polyandrous marriages minimize population growth and may occur in societies where there is a temporary surfeit of males and scarcity of females or scarcity of resources. In fraternal polyandry, brothers marry a single wife. This is the most common in Nepal, where it is practiced by a minority of mainly rural families. Fraternal polyandry offers several benefits for societies like Nepal with scarce resources and dense population. Where there is extreme scarcity of land acreage, it allows brothers to share an inheritance of land instead of dividing it up. It reduces inequality within the household, as the family can thus collectively subsist on the land as a family unit. Also, in areas where land is scattered over large distances, it allows brothers to take turns living away from home to tend herds of animals or fields and then spending time at home with their shared wife. It also minimizes reproduction and population growth in a society where there is a very dense population (Goldstein 1987), as the wife can carry only one pregnancy at a time.