Over at The Genetic Literacy Project Jon Entine has a post up, Usain Bolt’s Olympic gold proves again why no Asian, white–or East African–will ever be crowned world’s fastest human. Fifteen years ago Jon wrote Taboo: Why Black Athletes Dominate Sports And Why We’re Afraid To Talk About It, so he knows something about this topic.

Actually, I think Jon is wrong on this. Better drugs and biological engineering mean that I suspect at some point in the near future the fastest “human” alive is going to be non-African, and, if I had to bet, Chinese. But you know what Jon meant.

There is a lot of detail in Jon’s post because he knows a lot about this topic. But at the end of the day the specific details are less important than the general theoretical framework, which makes it unsurprising that a single group of humans who are genetically related dominate sprinting. Unlike figure skating, sprinting is entirely objective. All that matters are physical inputs. Second, unlike swimming, which is also objective, sprinting seems to have pushed very close to the boundaries of what non-modified or drug-enhanced individuals are capable of. To my knowledge there’s no expectation of a Fosbury Flop in sprinting.

Therefore, sprinting is selecting for raw ability. Training is not irrelevant, but the issue with training is that others can train too. What can’t be mimicked is raw ability due to one’s biological aptitudes and abilities (again, excepting bioengineering). Let’s assume that Olympic caliber sprinters are among the 10,000 fastest humans on the planet, because not all people with the aptitudes become sprinters. Assuming a normal distribution, that’s about five standard deviations above the human norm. I suspect I’m being conservative. Someone like Usain Bolt is probably a six standard deviation unit human. Google tells me that a fit human can run the 100 meter dash in 13.5 seconds. The world record is about 9.5 seconds. The absolute range here is not incredibly large. Small differences in the mean across populations suggest that when you select for extreme individuals those small differences will make all the difference.

If sprinting was less objective, then there would probably be more equality in outcome. I suspect judges would be biased for various reasons, and one set of nations or people of a particular ethnic background dominating a field can get quite embarrassing. But sprinting is rather objective, and the socioeconomic obstacles are low. Given basic nutrition, and the ability to huff it, you have a shot. What matters is the magnitude of your ability.

One peculiar thing population genetics teaches us that non-adaptive traits are more heritable. This is due to the fact that selection tends to remove variation, selecting for fitter individuals. Humans are good runners, there are entire evolutionary theories based around our biomechanical modifications and adaptations. But there’s really no benefit in running in bursts of 10.5 in the 100 meter dash vs. 9.5. We’re not that sort of ambush predator. There’s probably some heritable variation in burst ability, but it’s small, and not visible in any normal set of tasks among large groups of humans.

But modern competitive sports at the Olympic level is not selecting for normality, it’s selecting from outliers. It isn’t that West Africans were guaranteed to be the best sprinters, it’s just that a priori it shouldn’t be surprising that in such a non-adaptively beneficial trait as running a few seconds faster in the 100 meter dash some populations had the genetic die loaded in their direction.

Note that I’m not denying any sort of selective or adaptive argument. There’s a fair amount of evidence that there is some selection in favor of greater height in Northern Europeans vs. Southern Europeans, which probably explains why Lithuanians are more prominent in basketball in relation to their numbers than Italians. But the selection wasn’t for basketball, and the fact that there is heritable variation suggests that selection wasn’t that strong and unidirectional….

Humans vary. Populations vary too. When you select from the tails of the distribution, the differences between populations are going to be very noticeable. If a sport is objective, and pushing its limits, it will select from the tails of the distribution.