According to Science Daily, the roots of human suspicion and animosity toward outsiders go back some 25 million years:

Human Prejudice Has Ancient Evolutionary Roots

ScienceDaily (Mar. 18, 2011) — The tendency to perceive others as “us versus them” isn’t exclusively human but appears to be shared by our primate cousins, a new study led by Yale researchers has found.

In a series of ingenious experiments, Yale researchers led by psychologist Laurie Santos showed that monkeys treat individuals from outside their groups with the same suspicion and dislike as their human cousins tend to treat outsiders, suggesting that the roots of human intergroup conflict may be evolutionarily quite ancient.
The findings are reported in the March issue of the Journal of Personality and Social Psychology.
“One of the more troubling aspects of human nature is that we evaluate people differently depending on whether they’re a member of our ‘ingroup’ or ‘outgroup,'” Santos said. “Pretty much every conflict in human history has involved people making distinctions on the basis of who is a member of their own race, religion, social class, and so on. The question we were interested in is: Where do these types of group distinctions come from?”
The answer, she adds, is that such biases have apparently been shaped by 25 million years of evolution and not just by human culture…

In the article, we get the impression that scientists disapprove of what evolution/nature has wrought.  They describe it as “troubling” and “bad news”.  Not once is it considered that there might be good reasons for this tendency, or that the distinction between “insiders” and “outsiders” is necessary for the development, and preservation, of human biodiversity.  Any rational person, even a layman, should understand that, if evolution lead all primates to distinguish between “us” and “them” in such a way, surely there is an advantage to this.  The reader should be left scratching his head and wondering why, all of a sudden, these scientists are opposed to nature.  Clearly, they wish to relegate nature to the status of “them” and our modern social experiments and goals to the status of “us”.
But there is hope, they say.  Even though “us” and “them” clearly is rooted in biological relationships, nature can be fooled.  The nation-state, organized religion and sports teams are good examples of this.  But these scientists (AKA “social engineers”) do not wish to build onto what nature has given us; they wish to eliminate it:

“The bad news is that the tendency to dislike outgroup members appears to be evolutionarily quite old, and therefore may be less simple to eliminate than we’d like to think,” Santos said. “The good news, though, is that even monkeys seem to be flexible about who counts as a group member. If we humans can find ways to harness this evolved flexibility, it might allow us to become an even more tolerant species.”

“Tolerant” is a useful word; it masks the nefarious intentions of those who wish to erase racial/ethnic distinctions from our species (or, at least when it comes to whites).  What these scientists might not realize is that the old distinctions will be replaced by a new one: the ruling elite and the enslaved masses – under one world government.  Presumably, these scientists are intelligent people, so surely they must realize that the only possible outcome of a world without race/ethnicity would be a world without borders.  Or perhaps they really believe that a completely “tolerant” race/ethnicity can maintain its distinctiveness long term.  Can they be so naive?