Racism I think there’s no such thing. The correct word is tribalism. An evolved characteristic important to survival. You identified and protected your in group/- family, group, tribe, clan, village. You internalized those you belonged to and were suspicious and defensive of those you didn’t.
If you did not develop tribalism you were on your own, and more likely to perish and not pass along those survival -centric genes.
It is coincidental that one of the best ways to identify your in group is by sight. Since that is our most important sense. The more people don’t look like you. The harder it is to overcome this evolutionary trait.