It's just skin color and incredibly slight genetic differences. Interbreeding and adaptation have been going on for as long as there have been different racial categories of humanity living throughout the different regions of the world, and in fact without them you and your precious "white race" wouldn't exist at all (because, if you remember, humanity started off in Africa, and if we had just stayed there, there'd be no modern caucasians, which you seem to love so much). And in truth, interbreeding between the races is actually one of the strengths of humanity, because over the years it has provided us with a massive amount of genetic diversity that has helped to eliminate the countless problems that arise when close-knit populations breed in isolation (which, if you remember learning about recessive traits back in school, causes normally hidden illnesses and deformations to become more and more common).
Now stop worrying about political boogeymen and live your life.
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