Political Tribalism

Humans have always had tribal instincts, supporting those in their group and viewing outsiders with hostility. In primitive societies, people cooperated with other members of their group, and viewed outsiders as potential predators, and potential prey. Encounters between people who did not know each other were likely to be violent.
People in primitive societies identified members of their group based on personal knowledge, which limited the size of their groups. Anthropologist Robin Dunbar concludes that people are only able to have stable personal relationships with about 150 people, so primitive societies were small, limited to those the members knew personally, and

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