Humans have always lived and worked in groups and instinctively seek to cooperate with others in their group while viewing people in other groups with hostility. People in the same tribe work together for their common good. People in other tribes are potential predators or potential prey.
Those tribal instincts have stuck with us in modern times, often in socially harmful ways. Tribal instincts are the basis for racism and lay the foundations for nationalism. Modern societies have developed institutions to channel tribalism in non-destructive ways, such as organized sports. Rather than going to war with those of another tribe, we
