What exactly do you think "makes no sense"? That two groups could evolve different traits over time? If so, how would you explain differences in skin color between West Africans and Northern Europeans? Or differences in lactose tolerance between different ethnic groups [1]?
Because I live in a western liberal democracy and have been indoctrinated to believe that differences between cultures have no qualitative bearing, they are merely choices among equal values, and as such I cannot possibly comprehend such blatant facts.
[1] http://www.foodreactions.org/intolerance/lactose/prevalence....