So, we know from modern genetics that people from the Caucuses invaded Europe about 9000 years ago. Those Caucasians are the ancestors of most Europeans … aka “white” folks.
However, that migration does not do much to explain skin color. White folks also include Jews, Arabs, Iranians, etc. So, our German friends had a problem. If being white was so much better, than how was it that the Jews, Arabs, and Iranians were not Christians? The answer was “race.” Since Christianity was TRUTH, the inability to see the truth had to be genetic and “Caucasians” had a duty to help the lesser races. Of course Jews, Iranians and Arabs were inferior and needed to be helped. “White mans burden” was invented.
As fas as I know this view of race, that is the idea that there are unique breeds of humans, is not all that old. Presumably, using modern racist classifications we would call the Romans “Caucasians.” But the Romans before Christianity were not, as far as I know, racists. They beat up on and dominated everyone BUT anyone could become Roman.
Then the Romans adopted a religion, Christianity and after the Muslim conquest of Rome, the remnant of Christianity became European civilization. These “white” folks … aka Europeans or Christians even depicted Jesus to look .. well .. Caucasian. The Crusades were fought to liberate Palestine and Constantinople from the Muslims.
The descendants of the immigrants from the Caucuses became the new Romans. Their technology became capable of world domination. The Caucasians saw it as their burden to spread white civilization (aka Christianity).
This came ot be called the “Age of Discovery” … as if Hindu, Aztecs, Iorquois, Incas, Han and other dark skinned peoples needed discovery. In Spain, the the “white folks ” decided that civilization (aka Christianity) had arisen in Europe because of racial superiority. They made lkaws defining citizenship by race. The Spanish explained the evil of the Jews by the “drop of blood,” that is the Jews were genetically defective and, even if we converted, could nto have full rights of an authentic Christian.
Later the same idea was used to justify enslavement of Africans, These children of Ham needed “white” man’s help to become civilized.