The requirement that people select mates outside certain groups:

🧠 Explanation:

Exogamy, the practice of marrying outside one’s social or cultural group, promotes genetic diversity and social alliances. Common in many societies, it contrasts endogamy, where marriage occurs within a group. Exogamy strengthens intergroup ties, reducing conflict and fostering cooperation. Anthropologically, it’s studied to understand cultural norms and kinship systems. Its practice varies, from tribal customs to modern intercultural marriages, reflecting social evolution. Exogamy’s role in broadening social networks and genetic pools highlights its significance in human societies, shaping cultural exchange and community structures across diverse global traditions.