The best athletes on the planet are black. Stop the conversation right there and few will argue the point. It's always the next comment that burns down the house. For if there were no want or need to decide why blacks have come to dominate the sporting scene, a lot of old white men would not have disgraced themselves. Jimmy (the Greek) Snyder wouldn't have been fired by CBS in 1988 for proffering a half-baked theory based on the breeding practices of slave owners. Dale Lick, whose hope for the presidency of Michigan State sank in 1993, might be in East Lansing today had he not once said, "The muscle structure of the black athlete typically is more suited for certain positions in football and basketball." And Jack Nicklaus, who dismissed the absence of blacks in golf by saying, "Blacks have different muscles that react in different ways," wouldn't cringe each time he sees Tiger Woods tee off.

The urge to explain the black domination of sports has stained so many careers that it's a topic few want to touch. "Most people are afraid of dealing with the subject, afraid of being labeled," says David Hunter, an exercise physiologist and head of the department of health and physical education at Hampton (Va.) University, who recently completed a survey of studies of race and sports in this century. But, Hunter notes, "if we say, 'This might cause problems, let's not study it,' we simply perpetuate whatever thoughts we've had."

The "problems" Hunter speaks of stem from the longstanding fear that casual theorizing about black physical superiority will inevitably--if illogically--lead to the kind of negative stereotyping found in the 1994 book The Bell Curve, by Richard J. Herrnstein and Charles Murray, which suggested that blacks aren't as smart as whites. But scientists such as Hunter argue that if we're willing to concede a genetic predisposition to sickle-cell anemia or the early onset of adolescence among black girls, then we should at least discuss the possibility that blacks have physical traits that give them an advantage over whites in sports.

As blacks, who constitute 13% of the U.S. population, have become the overwhelming majority in the NBA and the NFL and at the elite levels of some other sports, the issue has reached the mainstream press. In 1992 Runner's World magazine printed a story titled "White Men Can't Run" that cited a variety of scientific studies--most of which found physiological differences between racial groups--that may explain why blacks dominate both sprinting and long-distance running. In 1995 Roger Bannister, a respected physician and the first man to run a sub-four-minute mile, helped bring the debate further into the open. "As a scientist rather than a sociologist," Bannister said, "I am prepared to risk political incorrectness by drawing attention to the seemingly obvious but understressed fact that black sprinters and black athletes in general all seem to have certain natural anatomical advantages. Perhaps there are anatomical advantages in the length of the Achilles' tendon, the longest tendon in the body." He also mentioned blacks' "relative lack of subcutaneous fatty insulating tissue in the skin" as a possible physiological advantage. Then last May, in The New Yorker, writer Malcolm Gladwell advanced a genetic argument in support of the notion that blacks are athletically superior. Clearly, the genie is out of the bottle.

Most scientists who study the subject, however, reject the simplistic reasoning that if blacks dominate sports, they must inherently be better athletes. "You've got to be very careful generalizing from the athletic population to the broader population," says Robert Malina, director of the Institute for the Study of Youth Sports at Michigan State. "Athletes are probably the most rigorously selected segment of our population, the cream of the crop. They are statistically aberrant."

Hunter, who is black, is a practitioner of hard science who believes what social scientists believe: that social forces--the emphasis on certain sports in black communities, the conviction that sports offer one of the few avenues to success for America's racial underclass--play the major role in the development of athletic excellence. But Hunter also has one foot planted in the other, more controversial camp. He knows that there are observable and quantifiable physical differences between black and white Americans, and he wonders if they provide an advantage in sports.

Generally accepted research has shown that African-American children tend to have denser bones, narrower hips, bigger thighs, lower percentages of body fat, and longer legs in relation to their upper bodies than white kids, and tests have also shown that they run faster and jump higher. That a combination of narrow hips, powerful thighs, low body fat and long legs seems perfect for sprinting and jumping has been lost on no one looking to explain black excellence at those skills.

Top athletes, however, don't always conform to laboratory theories. The physical differences found between black and white Americans are interesting--and perhaps telling--but until large numbers of elite athletes are studied, it is irresponsible to declare that one physical trait accounts for the minute margin that separates the sprinter who sets a world record from the one who finishes 10th. Carl Lewis may be tall, long-legged and narrow-hipped, but in his prime he was beaten four times by Ron Brown, who was noticeably shorter and stockier.

"It's that logic--Aha! We found a difference! African-Americans have narrower pelvic girdles!--that most people fall into," Hunter says. "But if you test whether, independent of race, a narrower pelvic girdle is a predictor of speed, even though it's a tremendous theoretical model, it doesn't hold true. Not everyone in the NBA, whether he's African-American or Caucasian, is 6'6", and not everyone has a certain percentage of fat. There's not a single characteristic that is unique and always present and responsible for the performance. If there were, I'd be able to predict at an early age who should go into certain [sports]. I'd be a billionaire." At the same time, Hunter acknowledges that a variety of physiological factors contribute to an athlete's success, and that the lack of one of those characteristics in a successful athlete does not disprove its importance.

The study of race and athletic performance is best described as intriguing but immature. Geneticist Claude Bouchard of Laval University in Quebec has determined that certain human athletic traits, such as anaerobic power and training capacity, have a powerful genetic component, suggesting that, to a significant extent, athletes are born, not made. One Bouchard study that compared black West Africans with white French Canadians found a higher percentage of fast-twitch muscle fibers and anaerobic enzymes--both thought to be essential to explosive sprinting--in the West Africans, but Bouchard is the first to point out that he was not studying athletes. Until he does, he can only speculate about how the differences he found relate to athletic performance.

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 white 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.