From Edge.org, an insightful essay from the brilliant Freeman Dyson discussing biological and cultural evolution. This quote on how cultural evolution is affecting racism resonated:

"We see a small-scale example of this transition in the recent history of racism. Until recently, racism was a force of nature favoring the diversification of species. Humans traditionally hated and despised people of a different skin color. The natural evolutionary consequence would have been the division of our species into three new species, one pink, one black and one yellow. Only in the last few centuries, a strong reaction against racism has emerged, inter-racial marriage has become respectable, and the cultural unification of our species has pushed us toward biological unification. This is a small step in the long history of the transition of human societies from incessant warfare to brotherhood."

[edge.org]