Human beings are by nature tribal. We are tribal because our ancestors were tribal. Our ancestors were tribal because tribalism had evolutionary survival value.
Fifty thousand years ago, our ancestors lived in small communities of about 150 people. These tribes competed with other tribes for resources, and the competition was often violent and brutal. Loyalty to one’s own group and hostility to members of other groups was a valuable characteristic in tribal combat.
Someone who loved his neighbor (that is, a member of another tribe) as much as himself would not have been of much value in tribal warfare. If such people existed – say, as a result of some genetic abnormality – they most likely didn’t live long enough to pass on their genes.'
I have often suspected that the zeal with which some people today enjoy sports is a modern manifestation of ancient tribal instincts. Why do Dallas Cowboy fans cheer so avidly for their team – when the players on the field are personally unknown to them, have nothing in common with them and wouldn’t even be in Dallas if they weren’t paid to be there?