A significant amount of blacks worldwide had sickle cell anemia. In the past when humans lived in more isolated and homogeneous societies this was the standard existence. In fact, it conferred a resistance against malaria. Today, we have better treatments for that disease that don't carry the same side effects.

A more prescient and present example is that almost all humans are subject to cognitive biases. A wise man known as Citizen G'Kar once said "In the past, we had little contact with other races. Evolution taught us that we must fight that which is different in order to secure land, food, and mates for ourselves. But we must reach a point where the nobility of intellect asserts itself and says no, we need not fear those who are different. We can embrace those differences and learn from them."