> Treat people as individuals, not as representatives of some kind of meaningless tribe

I dont't think that's how we make our day to day decisions. I usually treat people as individuals because I expect to be treated the same, but it doesn't make the "tribe" features meaningless. For example I would not live in given neighborhood if its tribe is knwon for [something bad] (this also applies to my own tribe). If I have an object of value, the tribe of a person would certainly be a factor to decide whether to entrust him with it or not. I'm sure a lot of people would do the same. It's just how probabilities are tranlated by the brain.