Jamaican evolution

Paul Rodgers investigates if evolution might explain Jamaican athletes' impressive performance at th

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“Are we seeing evolution at work?” asked a colleague as the Beijing Olympics came to a close last month. I was stunned, but he had evidence: Usain Bolt’s 9.69 second 100m dash, no less. So superior was Bolt that he didn’t even tax his abilities to the limit while setting this new world record; he began to showboat as he neared the finish line, contemptuous of his rivals’ attempts to catch him. Was this not clear evidence of the emergence of Homo supernus, a species superior to mere H sapiens?

Bolt wasn’t alone. The tiny nation of Jamaica – with a population of 2.8 million, less than that of Wales – won 11 medals in Beijing, six gold, three silver and two bronze, all of them in athletics. It ended up 13th in the medal rankings, well ahead of bigger, richer countries. Nor was the success of Jamaica’s 2008 team unprecedented. In the 100m alone, it claimed silvers in 1952, 1968, 1976 and 1996, plus bronzes in 1972, 1984, 2000 and 2004.

And the statistics are misleading; several recent winners for other countries were in fact reflagged Jamaicans. Linford Christie, who won gold in Barcelona, was running for Britain, while Donovan Bailey represented Canada when he won in Atlanta, as did Ben Johnson, who was stripped of his victory in Seoul after failing a drugs test.

It’s an impressive record, but not nearly enough to show evolution at work. Complex behaviours such as running are governed by a host of genes influencing everything from the size and shape of bones to the microscopic structure of muscles and the efficiency of oxygen-carrying molecules in the blood.

To argue that the success of Jamaica’s athletics team was down to better genes, you would have to show that a new mutation emerging on the island in the past 500 years (assuming that the pre-Columbian Arawak and Taino were exterminated) conferred such a speed advantage that it drowned out other factors, both genetic and environmental.

And as if on cue, just such a mutation appeared in the press shortly before the Games opened in Beijing. Professor Errol Morrison, the president of Jamaica’s University of Technology, and a team from Glasgow University have found that Jamaica’s elite athletes had a particularly high incidence of a protein called α-actinin-3 (misnamed “actinin a” in most reports), which is produced by a gene called ACTN3 and has been linked to explosive releases of power in fast-twitch muscles. Of the Jamaican athletes studied by Morrison and his colleagues, 70 per cent had the gene for α-actinen-3, compared with just 30 per cent of Australians. This, it was claimed, was the genetic root of Jamaican’s superiority on the track. As The Daily Mail said on 6 August, it determines “whether humans are sprinters or plodders”.

Except that it doesn’t. Daniel MacArthur, a researcher at the Institute for Neuromuscular Research in Australia and member of the team that first linked the gene with elite athletes, notes that everyone has the ACTN3 gene, in one of two forms. As often happens, one of these forms is dominant, resulting in the production of α-actinin-3, the other recessive. People with a double dose of the recessive gene produce no α-actinen-3, produce less explosive power in their fast twitch muscles and are, not surprisingly, under represented among athletes the world over, since the difference in performance has been estimated at 2 to 3 per cent.

But a double dose of the dominant gene confers no special advantage. And when you count the people with one dominant and one recessive version of the gene as well as those with the double dominant version, the disparity between Jamaica and the rest of the world starts to disappear. Of Jamaicans, 98 per cent have at least one dominant version of the gene, compared to 82 per cent among Europeans. Around the world, an estimated 5 billion people have at least one copy of the dominant gene. It’s a fair bet that every runner at the Olympics had the dominant version of ACTN3.

Lots of other explanations have been put forward for the Jamaican team’s success, ranging from yams in the diet (as suggested by Bolt’s father) to the long distances that many Jamaican children run to get to school. Perhaps most significant though is the cultural importance of the track. Just as young British athletes are attracted by football and young Americans by basketball and baseball, Jamaicans have their own favourite sport, athletics. The Champs, the annual high-school athletics meet, is the country’s top sporting event. And for the past 30 years, the elite from those trials have gone on to Professor Morrison’s Utech, where their skills have been further honed.

Chances are, this is no more evidence of evolution than the lottery-backed success of Britain’s 2008 Olympic team.

Paul Rodgers is a freelance science, medicine and technology journalist. He was born in Derby, the son of a science teacher, and emigrated with his family to the Canadian prairies when he was nine. He began writing for a student newspaper in Winnipeg in 1982 and had staff positions on several Canadian dailies. Despite his return to these shores 15 years ago, he still talks with a funny accent.
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