[Tax-chick]

I agree that, conceptually, there's an obvious survival benefit to associating "people who look like us" with "people who think/act like us and therefore aren't an existential threat." It saves effort, as Thomas Sowell points out in explaining why travelers stop at McDonald's.

In practice, it's more complex, or Native American groups who were culturally and genetically very close wouldn't have identified themselves as deadly enemies. Perhaps, in difficult survival situations, humans define "like me" down to a very fine calibration.

But even that is too simplistic ...

I agree, "breeds of humans" doesn't sound right, but it might be a useful concept. On the other hand, we're supposed to be reasonable. We could say "nation" or "culture" or something non-biological to emphasize our differences. On the other, other hand, there is something biological, or the top marathoners wouldn't all be Ethiopian or Kenyan.

[Harmless Teddy Bear]

Reality is always complex and with really odd twists and turns.