Jason Williams, the flashy guard of the NBA's Sacramento Kings, is affectionately called "The Thrilla in Vanilla" by his black teammates. His catlike schoolyard aesthetic, long the signature of elite black stars, has stirred considerable gee-whizzing, as in: "Wow, maybe some white guys can jump and run."

But only some. Black players have redefined modern sports in both quality and quantity. Black North Americans make up 87% of the NBA and 75% of the NFL. Blacks dominate boxing and are significantly over-represented in soccer--for example, in Britain, 2% of the population but 20% of the players are black. And while only 800 million people in the world are of African ancestry or one in eight, every major world running record is held by a black athlete.

West African-descended blacks hold the 200 fastest, 100-metre times, all under 10 seconds, which no white, Asian or East African runner has ever broken. All 32 finalists in the last four Olympic men's 100-metre races trace from this region, a statistical likelihood of 0.0000000000000000000000000000000001%.

While West Africans monopolize sprinting, they are hapless at longer distances, which demand endurance more than speed – the forte of North and East Africans. Kalenjins of the Great Rift Valley, who represent 1/2000th of Earth's population, win 40% of top international distance-running honours. One tiny district, the Nandi, with only 500,000 people, sweeps an unfathomable 20% of major international distance events -- by almost any measure, the greatest concentration of raw athletic talent in the history of sports.

Now, the politically acceptable reaction to this staggering trend is silence, a harshly enforced taboo (which, not coincidentally, is also the name of my just-published book). Moreover, it is considered a "white obsession" to marvel over the fact that over the past 30 years, as the social and economic barriers in sport have fallen, the playing field has some increasingly segregated as the athletic cream, or natural athleticism, rises to the top.

An obsession? "I've been asked many times how an academic can waste time studying the differences between black and white people," comments Kathy Myburgh, an African exercise physiologist. "I said, 'Well, if you're a scientist and you're studying obesity, who do you compare obese people with? You compare them with thin people. But if you are a physiologist and you want to compare your best runners with those not quite as good, you compare the black ones with the white ones, because the blacks clearly are performing better.'"

Yet rational discourse is invariably the loser when nature and nurture are at issue. As a consequence, the politically acceptable explanation for such utter dominance is the wholly unconvincing (and I believe racist) suggestion that blacks succeed to escape the clutches of the ghetto. In other words, they are merely products of their environment.

Tell that to Donovan Bailey, a recent Olympic 100-metre gold medal champion, who quit his job on the Toronto Stock Exchange and put his Porsche in hock to pursue his dream to become the world's fastest human. Or tell that to the utterly middle-class Michael Jordan; Kobe Bryant who speaks fluent Italian; or Grant Hill, the son of a Yale father and a Wellesley mother. Anyone who knows a whit about sports knows the success of any individual athlete results from dedication, drive and intelligence – in tandem with whatever "natural" gifts he may have. But if the roulette wheel of genetics did not land on your number hard work would come to naught. So while the success of any individual athlete can be attributed to the athlete himself, the pattern of success in sports – in this case, the international emergence of the black athlete – is almost wholly a product of genetics and driven by evolution.

"If you can believe that individuals of recent African ancestry are not genetically advantaged in certain athletic endeavours," says University of California-Berkeley biologist Vincent Sarich, "then you probably could be led to believe just about anything. But such dominance will never convince those whose minds are made up that genetics plays no role in shaping the racial patterns we see in human behaviour. When we discuss issues such as race, it pushes buttons and the cortex just shuts down."

Evidence spilling forth from the "Human Genome Project shows that although humans are mostly the same functional characteristics differentiate populations clusters. DNA research has revolutionzed our understanding of disease, more than 3,000 of which are genetically linked. Many, such as Tay-Sachs and breast cancer, which disproportionately affect Ashkenazi Jews, or sickle cell, which afflicts blacks, are population specific. So why do we accept that evolution has turned out populations with a genetic predisposition to certain diseases yet find it racist to suggest blacks of West African ancestry have evolved into the world's best sprinters and jumpers?

To the degree that the issue is the sciencs of human biodiversity, the case is closed – there exist identifiable, if fuzzy-edged, populations, popularly called races, with a range of functional differences. The so-called controversy is wholly political. The cant, in vogue since the early 1960s, that humans are a tabula rasa and that "race" or other biologically grounded facets of human nature such as sexual identity or gender-orientation are social constructs is an ideological simplism – a political belief.

How have such differences evolved? Significant differences have resulted from any number of genetic and environmental forces including mutations, disease, genocidal pogroms, volcanic eruptions and ice ages, migrations and mating patterns. This is the biological elimination tournament known as evolution.

Sports is an elegantly simple laboratory to test this emerging consensus about human biodiversity for it offers a definitiveness that eludes other aspects of life. Muscle fibres, reflex capabilities, metabolic efficiency lung capacity and a host of other variables that shape great athletes are not evenly distributed among populations. The endless feedback loop that binds nature to nurture turns out athletes with extraordinary and distinct skills: Dominican baseball stars; Asian gymnasts; Eurasian wrestlers and weightlifters; and ultra-long-distance runners from the Tarahumara tribe in the Copper Canyons of Mexico are all examples of the interplay of population genetics and culture. Tiny genetic differences are exaggerated by culture and imbedded in stereotype

"Differences among athletes of elite calibre are so small," notes Robert Malina, a Michigan State anthropologist and editor of the Journal of Human Biology, "that if you have a physique or the ability to fire muscle fibres more efficiently that might be genetically based it might be very, very significant. The fraction of a second is the difference between the gold medal and fourth place."

The stereotype that blacks make better athletes than whites is neither wrong nor racist. But popular thinking understandably lags the genetic revolution. White fascination with black physicality is part of a dark historical undercurrent. That should never be far from anyone's mind. Science is not an assertion of inalterable facts, but a method of interrogating reality. The challenge is in whether we can conduct the debate so that human diversity might be cause for celebration of our individuality rather than serving as fodder for the demagogues of the left and right. After all, in the end, for all our differences, we are far, far more similar. That's Taboo's only real message.

Jon Entine is a journalist end Emmy-winning producer formerly with NBC and ABC news who lives in southern California.