The Young Turks

More social economic, than bone density or body fat? Here's a Financial Times story on this topic:

But Goodhew said something else that gave me pause for thought: a few years back there was a theory going around suggesting that the paucity of top black swimmers “was to do with bone density and muscle density. Some black people are very muscular and very dense in their structure.

He made clear at once that this was not a line he bought into. “I think the major issue is socio-economic: a swimming pool is expensive; coaching is expensive.” It seemed to me, though, that if this was the full story, we could reasonably have expected the occasional aquatic Linford Christie or Venus Williams to have emerged over the years - and not just Eric the Eel. I decide to probe further.

Google turned up an array of references to a book, Taboo: Why Black Athletes Dominate Sports and Why We're Afraid to Talk About It by Jon Entine, scholar in residence at Miami University in Ohio. I fired off an e-mail to runjonrun@earthlink.net and minutes later he was on the line.

"I don't think there's any question that there are physiological factors [that help to explain why swimming is such a white sport],” he said. “It has been known for hundreds of years that blacks are ‘sinkers' because they don't have natural buoyancy. Black skeletons are, on average, heavier than white. We also know that blacks have on average less natural body fat for no other reason than that they evolved near the equator.”

However, he cautioned, “what complicates the matter is that, unlike running or football, the barrier to entry for competing at elite swimming is among the highest of any sport because, besides needing a swimming pool, you need sophisticated coaching. Teasing out the degree to which success is based on genetics, as opposed to social or cultural issues, is impossible.”

I unearthed references to several of them in an article - “Measures of body composition in blacks and whites: a comparative review” - co-authored by Dale R. Wagner and Vivian H. Heyward. When I spoke to him, Wagner, an exercise physiologist at Utah State University, had no hesitation in supporting Entine's remarks on bone density. “From all the research that has been done, black people overwhelmingly tend to have greater bone density than white people on average,” he said - although he added: “I don't necessarily know how that would translate into being a world-class swimmer.”

However there was “no conclusive evidence” that black people had less body fat than whites. “A lot of studies have used a two-component model separating the body into fat and fat-free tissue,” he said. “The problem is that you have to make the assumption that everybody's fat-free body density is essentially the same.” Since black people's bones were on average denser than whites, such studies would tend to underestimate their body fat levels.

So that was that, or so it seemed. Elite black swimmers were thin on the ground for a variety of economic and sociological reasons that tended to drive them towards other sports, coupled with their denser than average skeletons. Given how well-established this physiological detail appeared to be, however, I was surprised at how difficult some of those I spoke to, even scientists, seemed to find it to accept. One UK-based lecturer in bioethics seemed to think it better to leave such unpalatable hypotheses unacknowledged. “Even if it's true, where does that leave us?” he asked of the supposed difference in bone density between blacks and whites. “It does lead towards separating people out by race.”

It was then that I spoke to Simon Underdown, a lecturer in biological anthropology at Oxford Brookes University. What he told me appeared to undermine the theory I had developed. His argument, in essence, was that the human skeleton is more dynamic than I had previously supposed, changing in structure in line with the nature of our lifestyles. If you led the life of a hunter-gatherer, for example, your skeleton would become denser. And this would happen within your lifetime; it would not require the passage of generations for the change to become apparent. Citing the now extinct indigenous inhabitants of Tierra del Fuego, he said the relative harshness of their living conditions was reflected in their “enormously dense skeletons”.

If Underdown was correct, then of course those studies of comparative bone density that I had taken as proof that black swimmers laboured under a physiological disadvantage reflected only the difference in the respective lifestyles that the owners of the tested skeletons led. His conclusion, therefore, came as no surprise: “I cannot think of a skeletal reason why black people should be handicapped as elite swimmers.”