Final answer:
Marriage serves several purposes, including providing a structure for raising children, reducing competition among genders, and creating a stable household. Society has rules regarding who individuals can marry based on endogamy and exogamy.
Step-by-step explanation:
Marriage is an effective means of addressing several common challenges within families. It provides a structure in which to produce, raise, and nurture offspring. It reduces competition among and between males and females. And it creates a stable, long-term socioeconomic household in which the family unit can more adequately subsist with shared labor and resources.
All societies practice rules of marriage that determine what groups an individual should marry into (called endogamy rules) and which groups are considered off limits and not appropriate for marriage partners (called exogamy rules). These rules are behavioral norms in a society.
For example, in the United States, individuals tend to marry within the same generation (endogamy) and usually the same linguistic group, but they marry outside of very close kin (exogamy). Those considered to be too closely related to marry are prohibited by rules of incest, a relationship defined as too close for sexual relations.