Tribalism

In tribal societies, an "us vs. them" mentality frequently existed, probably because those who lacked it didn't survive conquest by those who possessed it. As larger and larger groups were prodded by technological developments to cooperate together, people came to realize that neighboring tribes were really not so different and people came increasingly to see members of other tribes as people rather than as food or slaves. Most languages have one word for people who are a member of the tribe and another word for foreigner/barbarian. Typically, no word or concept exists either to distingish foreigner from barbarian or which includes both members of the tribe and outsiders. As first city-states and then nation-states evolved, tribalism evolved into nationalism. With both tribalism and nationalism declining worldwide, this "us vs. them" mentality is frequently expressed through the identification with and barracking for local sports teams.