Primal Taboo

This requirement created what he termed the "alliance theory." By forbidding marriage within the clan, families were forced to trade partners with neighboring clans. This mandatory exchange of individuals created web-like networks of communication, trade, alliance, and mutual dependence between previously hostile groups.

Modern sociologists often view these taboos as a defense against social confusion and the breakdown of family patterns, rather than just a moral sin. Literary and Cultural Usage primal taboo