True. But it begs the question, again, of Tribe.
Let's say your entire sample size comes from a single village. For some odd reason, scientists have collected babies from all across the world, and raised those children together, so that racial numbers were completely equal. Now assume that there's two other villages that were treated the same. All those children grew up wearing a distinct village-specific colour in their attire. Let's say village A had red, village B had blue, and village C had yellow.
My hypothesis is that people from a certain village will be more likely to want to form bonds of friendship with someone who had more of their specific village colour in their attire than of the others. People from village A would be more likely to wish to form friendships with someone who wore red as their predominant colour. Likewise, people from village A would feel more empathy towards someone wearing red.
According to my hypothesis, race wouldn't matter. Tribe would.
We've got a history of thousands of years of tribal warfare over resources. Unity came in the form of kingdoms, but those kingdoms used to be relatively small (with some exceptions) and even then, clan warfare was a predominant part of our cultures. Cultures. Tribal warfare is something we grow up in; the symptoms have more or less changed, but the basic premise has not.
Europe is still a very tribal place, with a predominantly tribal culture.