Everyone recognizes race. Africans, Europeans, and Asians can be distinguished at a glance because the races differ so obviously from each other. Although the differences are popularly referred to as “skin color,” as if this were where they began and ended, color is one of the least important ways in which the races differ.
Although many physiological differences are well established and easy to measure, they are often completely unknown to the general public. Perhaps this is because the cumulative effect of a list of physical differences can give an impression of alienness even more powerful than do assertions about mental differences.
Just as it was once universally accepted that races differ in intelligence, so the study of physical differences was once entirely respectable. Some 19th century investigators, however, hoped to find justifications for slavery and not all were good scientists. Therefore, in the revolt against “racism,” good data from the past has been thrown out along with the bad, and the study of physical differences has languished.
The modern data now becoming available confirm many 19th century views. The best evidence suggests that races differ markedly in such things as maturation rate, brain size, bone density, susceptibility to disease, and perhaps even personality.
The races differ in skin color because of different levels of melanin production. All races have approximately the same number of melanocytes, or melanin-making cells, but they differ in how actively the cells make melanin.
Anyone who has seen an albino African knows how trivial a racial difference skin color really is. The albino may actually seem more strange to a European than a normal African, because negroid features and tightly curled hair seem incongruous in a light-skinned person. No one would mistake the albino for a European. Likewise, West Africans, Dravidian Indians, and Australian aborigines are all “black,” but they are racially very different.
Color does have one physiological effect: three and a half times as much ultraviolet light from the sun passes through the skin of whites as through that of blacks. Light skin is beneficial in the northern regions where whites evolved, since ultraviolet light converts ergosterol in the body into vitamin D. Dark skin protects against the tropical sun.
Adaptation to Climate
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