If you look at some of the fiercest and bloodiest rivalries in history, what’s striking is not how different the opposing groups are, but how similar. Sure, they often hold different beliefs, but they live as neighbors, share ancestry, and hold similar customs.
In his 1930 essay “Civilization and Its Discontents,” Sigmund Freud commented on this dynamic, noting that it is frequently “communities with adjoining territories, and related to each other in other ways as well, who are engaged in constant feuds and in ridiculing each other.” Elsewhere he notes that the phenomenon is not limited to ethnic or religious peoples either: “Every time two families become connected by a marriage, each of them thinks itself superior to or of better birth than the other. Of two neighboring towns each is the other’s most jealous rival; every little canton looks down upon the others with contempt.”
If as a teenage football fan you were caught up in a cross-town rivalry with another high school, you know of which Freud speaks.
So what accounts for the peculiar hostility between groups of people that are in many ways quite alike?