Others who have performed studies have come away convinced that there is a marked difference in performance between the black and white groups they examined. They just can't say why. Gladwell's New Yorker essay used as its foundation the work of Yale geneticist Kenneth Kidd, which found that the DNA of black Africans contains more genetic variation than is present in the peoples of all the other continents combined; from this finding Kidd theorized that a higher than expected percentage of black Africans—and their descendants in the Americas—would have rare genetic combinations of one sort or another, including the combinations that would endow them with exceptional athletic talent (or an exceptional lack of athletic talent). Swedish scientist Bengt Saltin, whose comparison of Kenyan and Swedish distance runners found the Kenyans' muscles better suited to that athletic test, believes the difference could be caused as much by the Kenyans' high-altitude environment as by genetic factors. Tim Noakes, the South African sports physician whose testing of black and white South African marathoners showed that the blacks possessed higher levels of energy-producing enzymes in their muscles, allowing them to train harder longer, isn't sure whether the cause of that difference is genetic or environmental.
Hunter performed studies that, in lab testing, showed no difference in anaerobic power between black and white children. His field testing of the same group showed that the black children jumped higher than the whites by an average of some 10%. "The phenomenon of African-Americans performing better than whites in certain areas does exist, and it is worth studying," Hunter says. "But we don't have the answers yet, and it would be irresponsible for us to make them up."
Sums up Malina: "The scientific basis is just not that extensive." Especially when you consider that black may be the most slippery term in the debate. West Africans and Kenyans are both black, yet the first are thought to have bodies perfect for sprinting, while the Kenyans are distance legends. That the African continent may hold more genetic variants than anywhere else in the world would help explain this divergence. But what about the differences between either of those groups and African-Americans?
Though most black Americans descend from slaves taken from western Africa, 90% have some white ancestry, which renders the terms black and while particularly imprecise when applied to African-Americans. Does the fact that an NBA player like the very light-skinned Doug Christie, who may well be more white than black, can leap just as high and with as much body control as the dark-skinned Dominique Wilkins prove that it's wrong to assume that blacks are inherently better jumpers than whites? Or does it suggest that even a small degree of black ancestry confers upon someone the genetic variation that can lead to exceptional athletic ability?
As is the case with so many other questions about race and athletic performance, scientists do not yet have definitive answers. Given the logistical difficulty of testing large groups of top athletes under laboratory conditions, and the complexity held within the 100,000 genes that shape a person's characteristics, the only safe conclusion is this: Sports' nature-versus-nurture debate is a long way from being resolved.