One has to wonder what our "hate running water" thing is - ie something we feel compelled to do which seems perfectly sensible to us but is really just an evolutionary gimmick that some other species would think is weird.
Being predisposed to distrust people who look different is one example from the recent past. Back when people lived in frequently-warring tribes, someone who looked different (either due to genetic differences or cultural differences) was far more likely to kill you.
As far as I'm aware, cats don't care at all what colour fur other cats have.
Actually in hunter-gatherer societies inter-tribal violence is extremely rare, with intra-tribal violence being way more common. One has to remember that in hunter gatherer societies concepts like territory and property are not as important as in settled societies, and population densities are incredibly low. It's a very rare occasion when you interact with anyone outside your immediate community, and when you do it's almost certainly an interaction with a neighboring community that you've been collectively living near and interbreeding with for longer than anyone can remember. Violence in these societies tends to be part of personal feuds between individuals.
Encountering someone from far enough away that they would be part of a distinct genetic or cultural group was basically unheard of. That's not to say it didn't happen at all, there would be migrations and smaller groups would potentially travel long distances out of necessity, but it simply was not a part of normal life. The idea that a fear of different looking people provided any meaningful benefit in the past simply does not pass the sniff test.
