Three Is Not Enough

• Subjectivity:

If race is a valid biological concept, anyone in any culture should be able to look at any individual and say, Aha, you are a . . . It should not be the case, as French tennis star Yannick Noah said a few years ago, that "in Africa I am white, and in France I am black" (his mother is French and his father is from Cameroon). "While biological traits give the impression that race is a biological unit of nature," says anthropologist George Armelagos of Emory University, "it remains a cultural construct. The boundaries between races depends on the classifier's own cultural norms."

• Evolution:

Scholars who believe in the biological validity of race argue that the groupings reflect human pre-history. That is, populations that evolved together, and separately from others, constitute a race. This school of thought holds that blacks should all be in one race because they are descended from people who stayed on the continent where humanity began. Asians, epitomized by the Chinese, should be another race because they are the children of groups who walked north and east until they reached the Pacific. Whites of the pale, blond variety should be another because their ancestors filled Europe. Because of their appearance, these populations represent the extremes, the archetypes, of human diversity -- the reds, blues and yellows from which you can make every other hue. "But if you use these archetypes as your groups you have classified only a very tiny proportion of the world's people, which is not very useful," says Marks, whose incisive new book "Human Biodiversity" (321 pages. Walter de Gruyter. $23.95) deconstructs race. "Also, as people walked out of Africa, they were differentiating along the way. Equating 'extreme' with 'primordial' is not supported by history."

Often, shared traits are a sign of shared heritage -- racial heritage. "Shared traits are not random," says Alice Brues, an anthropologist at the University of Colorado. "Within a continent, you of course have a number of variants [on basic traits], but some are characteristic of the larger area, too. So it's natural to look for these major divisions. It simplifies your thinking." A wide distribution of traits, however, makes them suspect as evidence of a shared heritage. The dark skin of Somalis and Ghanaians, for instance, indicates that they evolved under the same selective force (a sunny climate). But that's all it shows. It does not show that they are any more closely related, in the sense of sharing more genes, than either is to Greeks. Calling Somalis and Ghanaians "black" therefore sheds no further light on their evolutionary history and implies -- wrongly -- that they are more closely related to each other than either is to someone of a different "race." Similarly, the long noses of North Africans and northern Europeans reveal that they evolved in dry or cold climates (the nose moistens air before the air reaches the lungs, and longer noses moisten more air). The tall, thin bodies of Kenya's Masai evolved to dissipate heat; Eskimos evolved short, squat bodies to retain it. Calling these peoples "different races" adds nothing to that understanding.