[Harmless Teddy Bear]

I would say the concept of race was to divide people into "like us" and "not like us". If they "look like us" then they are probably neighbors even if we never met and we share cultural commonality. Unless they show active aggression they are assumed to be non-hostile.

If they don't "look like us" then we probably don't share culturally commonality and they are to be regarded with caution as they would have had to cross the territory of those that "look like us".

It is a survival concept.

Of course there is really only one human race but people get so upset if you use "breed" of human even though it is more accurate.

[TexasFreeper2009]

I agree completely. Breed is a far better word choice.

[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.