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The science of why most marathon winners are from east Africa

The lead elite women's grouping, including first-place Rita Keptoo, arrives in Wellesley during the 118th Boston Marathon
The lead elite women's grouping, including first-place Rita Keptoo, arrives in Wellesley during the 118th Boston Marathon
Suzanne Kreiter/Boston Globe via Getty

Today's Boston Marathon set a major record: the first-place male runner is an American citizen for the first time since 1983. He is also an immigrant: Meb Keflezighi and his family moved to the US from the east African nation of Eritrea when he was 12. Meanwhile, the second- and third-place male runners are from nearby Kenya. Of the top five female finishers, two are Kenyan and three are Ethiopian.

All six winners in Boston today are originally from the same corner of the world: east Africa. And that's true of almost every major long-distance race, going back for years. So why is that? Why do runners from two or three medium-sized countries, none of which have much money or highly developed infrastructure, manage to outrun virtually the entire world —virtually every time they compete?

This is a question that scientists and journalists have been asking since the 1990s, when the trend began, a few years after African nutrition rates caught up with the rest of the world. But the question has never totally been answered, in part because merely asking it touches on some of the most sensitive issues in modern history: colonialism, slavery, and persistent racial inequality both in Africa and outside of it.

The most well-known theory for this may be the one that journalist Malcolm Gladwell proposed in his best-seller Outliers: that a combination of environmental factors (kids have to run to school because of poor infrastructure) and cultural values (running races is considered more prestigious) lead east Africans to just work harder and care more.

The scientific research into this, though, turns up something very different, and even more difficult to talk about sensitively: certain genetic traits common to this part of the world may help make people there naturally predisposed to be better runners. I looked into this question two years ago for The Atlantic; here's what I found:

Scientific research on the success of Kenyan runners has yet to discover a Cool Runnings gene that makes Kenyans biologically predisposed to reaching for the stars, or any scientific basis for Gladwell's argument that they just care more. Most of Kenya's Olympic medal winners come from a single tribe, the Kalenjin, of whom there are only 4.4 million. Sub-Saharan Africans have identified themselves by tribes such as this one for far longer than they've identified by nationality -- a system mostly imposed by the Western colonialism -- so the Kalenjin distinction is not just academic, and the tribe is probably genetically insular enough that common physical traits could inform their athletic success.

In 1990, the Copenhagen Muscle Research Center compared post-pubescent schoolboys there to Sweden's famed national track team (before Kenya and a few other African countries began dominating international racing events in the late 1980s, Scandinavians were the most reliable winners). The study found that boys on the high school track team in Iten, Kenya, consistently outperformed the professional Swedish runners. The researchers estimated that the average Kalenjin could outrun 90% of the global population, and that at least 500 amateur high school students in Iten alone could defeat Sweden's greatest professional runner at the 2,000-meter.

A 2000 Danish Sports Science Institute investigation reproduced the earlier study, giving a large group of Kalenjin boys three months of training and then comparing them to Thomas Nolan, a Danish track superstar. When the Kalenjin boys trounced him, the researchers -- who had also conducted a number of physical tests and compared them against established human averages -- concluded that Kalenjins must have an inborn, physical, genetic advantage. They observed a higher number of red blood cells (which lent new credence to the theory that elevation makes their bodies more effective oxygen-users) but, in their conclusions, emphasized the "bird-like legs" that make running less energy-intensive and give their stride exceptional efficiency.

This research was extremely controversial when it started to trickle out in the 1990s and 2000s. East African athletes saw it as trying to downplay or explain away their successes, which had come with tremendous work. Cultural critics saw it as a continuation of the racist, 19th-century idea that Africans were "specialized" for manual work. As I wrote:

Running, like any sport, is inherently physical, and physical traits inform athletic success. Just because Larry Bird and Michael Jordan are tall doesn't mean they aren't first and foremost great athletes. Part of Olympian Michael Phelps' record-breaking swimming is his unusual body shape, which is genetically inborn; you can't train for longer arms. All athletes owe some of their success to their own physical traits, but because Kalenjin runners share those traits across an ethnic group, and because that ethnic group is part of the story of colonialism and white exploitation of blacks for their physical labor, it's harder to talk about. But that doesn't make their athleticism any less amazing.

In other words, even if the explanation for east Africans' marathon domination as a group might have something to do with biology, that shouldn't take away one bit from the remarkable athleticism of the individual runners who actually go on to win.