Sickle cell anemia is a genetic disease that kills those who inherit the gene from both parents, but in those who inherit the gene from only one parent, it protects them from malaria. Great advances have been made worldwide in reducing death rates through advances in nutrition, medicine, and sanitation. But the human population evolved through millenia of combat with these diseases. For hundreds of thousands of years the human race has been in dynamic equilibrium, balancing between the forces of reproduction and death. Dark skin color reflects the location of the source population in an equatorial region of intense sunlight.
Melanin protects the tissues from the effects of excessive UV radiation.
Populations of people from Africa, India, and Australia have equally dark skin, yet are related no more closely to each other than they are with light skinned Europeans. Yet skin color has been used for millenia as a mark of quality, with darker skinned individuals and families unable to gain access to the same resources and opportunities as others. The framers of the U.S. Constitution debated this issue, but in the end the moneyed interests of the Southern colonies prevailed so as to permit the continuation of slavery. Racial tesions that still exist relative to the descendants of African ethnic groups in The United States are directly related to the entire history of ethnic relations in America. The epicanthic fold characterizing the oriental eye shape is a tiny variance of morphology that has significance only because it occurs on the face.