Greeks were not and to this day arent white. Romans, illyrians, greeks, egyptians and the countless types of semites would all be lumped within the same race in the modern day. The existence of a sharply defined "european" race is the result of european Christianity being severed from the rest of the Mediterranean by islam. Christians are not allowed to marry non-christians (2nd Corinthians 6:14)

The colonization of the new world made it so europeans ruled over massive swathes of newly converted people, and now they had to actively justify their rule over, so categories of races as ones more developed than others emerged.

In summary; No race defines itself sharply against the other unless made to do so artifically, either because of religion or politics. People have sex with whomever they can and that has applied everywhere that isnt an apartheid shithole like amerikkka. The very existence of blacks as a distinct ethnicity is a failure of american reconstruction