Quick recap for new visitors
Ok - I've gotten several emails/comments that suggest I should once again go over the evolutionary case for the
possiblity that human genetic differences exist and are important. Let's begin by making clear our points of agreement:
1) We agree that
races exist, and that genetic differences between ethnic groups go more than skin deep (as evidenced by organ transplants, medication responses, hormone levels, etc.)
2) We also agree that
some racial differences like melanin-rich/poor skin or the epicanthic fold of the Asian eye are responses to selection pressure. The epicanthic fold, or eyelid fold, of Asian people is believed to have evolved on freezing windswept plains of northern Asia, to protect the eye from extreme cold. At the equator, people came to be darkest--because darkness is and adaptation to intense sunlight. It was found years ago that among black sailors in the American navy (sailors were exposed to the sun for long hours), skin cancer was far less than among white sailors. As one travels north though Africa, away from the equator, skin becomes increasingly light. Continuing north, from southern Italy and France to northern Sweden and Finland, skin becomes still lighter, as does hair. The reason is this: is the north, where the sun is weaker and there is cloud, its rays cannot penetrate a darker skin to create vitamin D, without which a person many years ago would get rickets. So a light, transparent skin was an adaptation to weak sunlight.
Thus,
at least some of the genetic differences between people from different ancestral geographic regions
are due to differential selection pressures. Some, of course, are due to genetic drift (which is random-walk evolution in the absence of a directional "wind of selection").
3) So we have established that
there are differences that go more than skin-deep and they are sometimes important. A priori, then, we cannot do as Stephen J. Gould does and assert that "human equality is a contingent fact of history". Some features of all humans are in fact equal - we (mostly) all have two eyes, two ears, etc. But we agree that there are genetic differences in intelligence
between individuals, and that there are genetic differences in
other properties between groups, so
a priori we can't discount the existence of genetic differences in intelligence between groups. We need to use the methods of science to see whether such differences exist.