Evolution did not equip us for solitary living. It has been done, but only rarely, and most of us would find it hellish if we could do it. For most of human history, rejection by one's tribe was practically a death sentence. There were usually no other tribes nearby, and if there were there was no assurance they would accept another tribe's outcast.
So there is no point in denouncing tribalism as such. What we can denounce is the kind of tribalism that says no person with good sense or good morals would belong to any tribe but our own. The prevalence of this kind of tribalism is a major reason for the current troubles.
This is especially pernicious with doxastic tribes, those defined by doctrinal systems. Religions are the archetypal doxastic tribes, but some political movements fit the category, too.
Us versus them is not the problem. You can't have tribalism without it.
OK, we need other people. But why the divisions? Why not just we all work together?
Because we're not all alike, and our differences can't all be trivialized.
(This page last updated on October 2, 2019.)