european civilization suffered several devastating bouts of plague. the one in the 1300s was particularly brutal, killing more than a third of the population in certain regions. it happens to be that this was also the period when european civilization was under it's greatest threat of invasion from both the south and the east.

it is actually not at all outlandish to consider an alternate history where the closest ancestors of the ancestral native american populations - turks, mongols - could have swept into europe and utterly decimated the civilization there. there is even ample historical evidence as to what this would have been like, in the advances of genghis khan into afghanistan, iran and syria.

once again: the best argument against racism is history.