Those who indulge in stupidity such as describing different "races" in terms of caucasians, or negroes, reveal their own racist subscription to the 19th century folly about races. There is only one race--the human race. My ancestors, the Irish, are about as white as they come--but we sure as hell are not descended from the wild tribesmen of the Caucasus. And in fact, the very concept of Caucasian gives the lie to the superficial ascribing of racial characteristics based on superficial appearance.
At the time of the crusades, the great Kurdish hero, Yusuf Sal'al Din (Saladin), came from his military base in Egypt. The backbone of Egyptian military might at the time were the Mamluks. Mamluk comes from an arabic word meaning "owned," they were military slaves. (
White warrior slave common in Muslim states from around the 9th century until the 19th century. "Mamluk" is Arabic for white slave, and the word is related to the word for king, "malik", indicating that a Mamluk was a slave owned by the ruler of a state --
Source.)
However, when Napoleon defeated the Mamluks at the Battle of the Pyramids in 1798, they were as black as the ace of spades, to use a common English language expression. The evidence for such a statement is to be found in literally hundreds of sources. Leave a white boy out in the sun for a few hundred years, and you'll have a black boy.
The point is that superficial traits are only significant to those who come to a discussion freighted with their own racist attitudes. A black woman and a white woman have far more in common on the basis of their gender than they have differences arising from the colors of their skins. Culture and ethnicity are greater determinants of what separates people, and it is petty tribal bigotry which makes that a problem.
So, once again, superficiality is at the heart of racism. Those who believe that there are "caucasians" and "negroes" and that they constitute separate races are in the grip of the nasty racism, born in the 19th century and reaching its apotheosis with the likes of Adolf Eichmann.