Final answer:
According to Melvyn Goldstein, one of the rarest forms of marriage is polyandry. The prevalence of marriage forms such as monogamy, and especially serial monogamy, is higher in Western societies. Changes in societal norms, such as those seen in Iceland, influence evolving marriage patterns.
Step-by-step explanation:
One of the rarest forms of marriage, according to Melvyn Goldstein, is polyandry, which refers to a type of polygamous union where one woman is married to more than one husband. This form of marriage is less common globally compared to other marriage customs like monogamy or polygyny. The factors influencing the rarity of polyandry are complex, including but not limited to, economic conditions, cultural practices, and the roles children play in a society's food-getting strategy.
In contrast, the most common form of marriage in American and European cultures is monogamy, a union of two people that often follows the pattern of serial monogamy due to high rates of divorce and remarriage. As cultural norms evolve, we also see the emergence of different family structures and marital unions adapting to societal changes, such as the consensual unions in Iceland, where many children are born to non-married but committed couples. This reflects how societal values and policies can shape marriage patterns over time.