I've been reading a Jane Goodall book - you know, the chimpanzee lady. She talks about PSEUDOSPECIATION, which she prefers to call Cultural Speciation.

So, this chimpanzee group split up, with a smaller group kind of taking over a smaller part of the territory the whole group had previously inhabited. After a while, the larger group pretty much declared war on the smaller group and killed almost all of them.

The idea of pseudospeciation is, once a group of humans (and chimpanzees) becomes different enough culturally - by which is intended the things that individuals learn and pass down to offspring, such that, after a while, the whole group is different enough from another group of humans, the groups can stop seeing each other as some kind of kindred, and can kill and harm each other with no inhibitions.

Thus with people. Along almost any line of cultural division, humans can come to see the other side as different enough, and hateful enough that it becomes ok to kill them and war on them. That bodes very poorly for the divisiveness that's become so prevalent in the US, in the past 10 years, or so.

It's almost like a cultural evolution/survival of the fittest group.

It looks to explain racism, war, and all kinds of other group enmities and hatreds. And, we may not be as evil as we think, because it looks like something humans and chimpanzees fall into it fairly readily. And, it's part of why we're always battling it out between morality - the care of other humans, and war.