Mention The Bell Curve in polite company these days, and it may not be polite for long. Critics have pummeled the best-selling book by Charles Murray and the late Richard Herrnstein, which blames genetics for the gap between the average I.Q. of whites and blacks. But most of the assailants haven't noticed that perhaps their best weapon lies almost unused right under their noses. At about the same time that Murray threw his Curve, Princeton University Press put out The History and Geography of Human Genes by population geneticists Luca Cavalli-Sforza, Paolo Menozzi and Alberto Piazza. Not only is the tome physically hefty (1,000 pages, 7 1/2 lbs.), but the evidence it contains may carry enough weight to flatten Murray's thesis once and for all.
While not exactly best-seller material, The History and Geography of Human Genes is a remarkable synthesis of more than 50 years of research in population genetics. It stands as the most extensive survey to date on how humans vary at the level of their chromosomes. The book's firm conclusion: once the genes for surface traits such as coloration and stature are ) discounted, the human "races" are remarkably alike under the skin. The variation among individuals is much greater than the differences among groups. In fact, the diversity among individuals is so enormous that the whole concept of race becomes meaningless at the genetic level. The authors say there is "no scientific basis" for theories touting the genetic superiority of any one population over another.
The book, however, is much more than a refutation of the latest pseudoscientific pronouncement. The prime mover behind the project, Cavalli- Sforza, 72, a Stanford professor, labored with his colleagues for 16 years to create nothing less than the first genetic atlas of the world. The book features more than 500 maps that show areas of genetic similarity -- much as contour maps match up places of equal altitude. By measuring how closely current populations are related, the authors trace the pathways by which early humans migrated around the earth. Result: the closest thing we have to a global family tree.
The information needed to draw that tree is found in human blood: the antigens, antibodies and other proteins that serve as markers to reveal a person's genetic makeup. Using data collected by scientists over decades, the authors compiled profiles of hundreds of thousands of individuals from almost 2,000 communities and tribes. And to ensure a degree of "purity," the study was confined to groups that were in their present locations as of 1492, before the first major migrations from Europe began -- in effect, a genetic snapshot of the world when Columbus sailed for America.
Collecting blood, particularly from ancient tribes in remote areas, was not always easy; potential donors were often afraid to cooperate, or raised religious taboos. On one occasion, when Cavalli-Sforza was taking blood samples from schoolchildren in a rural region of the Central African Republic, he was confronted by an angry farmer brandishing an ax. Recalls the scientist: "I remember him saying, 'If you take the blood of the children, I'll take yours.' He was worried that we might want to do some magic with the blood."