Xenophobia.

Xenophobia is a fear or contempt of foreigners or strangers. It comes from the Greek words xenos, meaning "foreigner," "stranger," and phobos, meaning "fear." The term is typically used to describe fear or dislike of foreigners or in general of people different from one's self.

Fear is the key word here.

The effects of Xenophobia sociobiological researchers see it as an innate biological response on the part of the evolved human organism in inter-group competition and the biologically rooted tendency of people that are more similar genetically to behave more generously toward each other.

Primates exhibit xenophobia when one social group comes across a rival group in the jungle. According to some researchers, all primates have an innate, evolution-produced tendency to seek proximity to familiar faces because what is unfamiliar is probably dangerous and should be avoided or perhaps attacked. Chimpanzees, and other primates, have been known to attack, kill, and eat, members of other groups.

More than two hundred social psychological experiments have confirmed the intimate connection between familiarity and fondness. (This would explain why we don't usually kill and eat family members.)

This universal innate, evolution-produced tendency in humans is the foundation for the behavioral expressions of xenophobia.

Favoritism towards one's own ethnicity is an evolutionarily based, "objective" value "universal nationalism", in which all planetary ethnic-based communities or nations have the right to preserve their own heritage and distinctiveness.

That's all well and good, but when will humans evolve enough to understand that to be truly human we must, for our own sakes, embrace all people and work together to solve the planets problems as one community?

It's time to stop drawing lines in the sand and defining ourselves as "us and them." We are all one people. All of us bleed red blood, we all treasure our children. Each and every one of us want the best for our selves and our families.