I think Eliza has put her finger on the crux of the origins of so-called "racial differences."

I have heard, from knowledgeable people such as anthropologists and environmentalists, that such things as a high quantity of melanin in the skin, making the skin dark, is an evolutionary adaptation to protection from strong sunlight in tropical climates.

I knew a number of Indian exchange students when I was in college, and although they were racially classed as "Caucasian," their skin was often as dark as that of many Black Africans.

And short and somewhat flatter noses:   if the air is warm and moist, It needs little pre-warming and moistening before it hits the lungs, whereas those who spent many generations in Northern climates (say, Scandinavians) tend to have larger noses with more sinus area to warm and moisten cold, dry air, along with light complexions (very little melanin) in order to absorb vitamin D from the sometimes meager sunlight.

And the "Moorish" or Arabic adaptations in North Africa and the Middle East? Brownish skin—melanin—as protection against strong sunlight, plus fairly large noses to "condition" dry desert air.

And the epicanthic fold that gives some Asian peoples their "slanted" eyes, evolved as a protection for the eyes against the glare of bright sunlight glinting off snow. Peoples such as the Inuit have the characteristic epicanthic fold.

A combination of evolutionary adaptation, and then—migration.

Or such is the theory of many anthropologists as to how different "races" came about. Sounds pretty reasonable to me.

So that means there is far less inherent difference between the "races" that some people would have us believe.

Don Firth