August 25, 2008
Jamaican athletes and the 'sprinting gene'
In my new apartment, I've opted to go with a handful of fuzzy over-the-air TV channels. (Cable is both expensive and distracting, but oh, how I will miss it!) So I actually spent quite a bit of time watching NBC's coverage of the Beijing Olympics. I can't remember why I missed most of the '04 and '06 games, but it was somehow comforting to watch Bob Costas and the NBC crew covering the events in their usual, distorted way.
In sprinting, the Jamaicans were simply unbelievable. Usain Bolt's performances were superhuman and his teammates racked up a number of medals, too. Assuming they're not doping (a reasonably safe bet since they've apparently been tested frequently), why is it that Jamaicans are such great sprinters? Further, why do New Worlders of West African ancestry make up such a disproportionate number of champions in short-track events? Is it genetic?
Clearly, genes are a very significant factor in creating an Olympian. Olympic champions are probably all at the very far end of the bell curve for some trait or combination of traits. (Michael Phelps, for example, has disproportionately large hands, feet, and torso.) But of course there's much more to it. We all know phenotype isn't determined entirely by genotype, yet we hear about a "sprinting gene" and immediately forget about countless environmental factors (like culture, nutrition, scouts, trainers, etc. -- it's quite belittling to Jamaica's culture and running programs).
The popular press, in particular, loves to latch on to some piece of data from the very complicated and nonintuitive field of genetics and run with it. A number of simplistic stories have been circulating in the press declaring ACTN3 as the Jamaican sprinting gene. Some articles (like Slate's 'Jamaican Me Speedy'), to their credit, did try to point out that it's rather more complicated than figuring out who does or doesn't have one or two copies of a particular gene variant (allele) in their genome. There are, of course, countless interacting genes involved as well as countless environmental & cultural factors. (Read this article to learn about some of the social reasons Jamaica has such a great track program.)
The best explanation I've seen is over at the Genetic Future blog. Take a minute to read The gene for Jamaican sprinting success? No, not really. Some highlights:
So, how good is this scientific evidence? Does the "Actinen A" gene (whatever that is) actually influence sprinting performance? And if so, does it explain the difference in explosive power between Jamaicans and the rest of the world? The answers, as it turns out, are "probably" and "not really."
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So the absence of α-actinin-3 means very little to most of us, but to a young athlete craving 100 metre Olympic superstardom it could make all the difference in the world. The same could be said of many other genetic variants, of course; Olympic sprinters, essentially, are those unlikely individuals at the vanishing edge of the probability distribution for whom nearly every genetic coin has come up heads.
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It is almost certainly true that Usain Bolt carries at least one of the "sprint" variants of the ACTN3 gene, but then so do I (along with around five billion other humans worldwide). Indeed, I'm fortunate enough to be lugging around two "sprint" copies - but that doesn't mean you'll see me in the 100 metre final in London in 2012. Unfortunately for me, it takes a lot more than one lucky gene to create an Olympian.
None of this rules out the possibility that some genetic edge does play a significant role in Jamaican sprinting success. Maybe there really is a difference in the Jamaican gene pool (and it wouldn't have to be much because it would be magnified when you're looking at Olympics-level athletes). It could be stochastic, or it could be the result of something like artificial selection resulting from the slave trade. (I doubt this, but you never know...) More explanation can be found at Weird lands of the tails from the Gene Expression blog.
The bottom line is that we simply don't know. It's complicated and there are probably multiple explanations for the trends we see. It would behoove the press (and us, as individuals) to stop speculating and making simplified assumptions. (In this wild new 'genetic world' we're living in, I'm not sure that's going to happen. Frankly, I'm a little worried. But we'll see...)
25 Aug 13:31 | Link | Category: Current Events, Human/Primate Evolution & Behavior, Science