Granted, most of us are a bit out of practice, but even you who walked the mile in high school gym class have the genetic stuff of an endurance hero. Lieberman suggests that our love of sports is partly an outgrowth of our running past. "Animals play at things that are important to them," he says, "and we play at running."
Yet there are massive differences in ability among individual humans even in running, a simple and global sport in which lack of access to equipment does not inhibit achievement. There is, for instance, an undeniable trend in elite running. The 18 fastest marathon times in history belong to East Africans—Ethiopians or Kenyans—and the top 10 sprinters ever in the 100 meters are men of West African descent. In short, they are all black.
ALL GENES ARE AFRICAN
WE ARE ALL black. Not in the sense that our skin is of a shade that protects against equatorial sunlight, but in the sense that Africa is contained in our every cell.
It starts with our brown-eyed, many-times-great-grandmother, the woman scientists call Mitochondrial Eve. Mitochondrial DNA is a genetic material that is inherited from one's mother, and as it happens, every one of us shares some of it with Mitochondrial Eve, a woman who lived in sub-Saharan Africa around 150,000 years ago, when the entire human population consisted of a few tens of thousands.
Since the mid-1990s scientists have been following the path of mankind's genes away from Mitochondrial Eve by collecting genetic data throughout Africa and beyond. Geneticists Kenneth Kidd of Yale and Sarah Tishkoff of Penn have been among the leaders in this endeavor. Some of their work supports the "recent African origin" model, which suggests that all modern humans can trace their ancestry to a single population in east-central Africa as recently as 100,000 years ago. Since humans branched off from our common ancestor with chimps about six million years ago, that means we're about a one-minute drill out of Africa.
What Kidd, Tishkoff and others have found is that genetic variability—differences in DNA among people—is greater among Africans within a single population than among people from different continents outside Africa. This is because all human genetic information was contained in Africa not so terribly long ago, and our ancestors who left Africa—most likely a single group of no more than a few hundred people—took only a small portion of it with them en route to populating the world. All of us outside Africa are genetic subsets of the subset that left Africa. So despite the fact that black Africans may share certain obvious features, such as dark skin, when it comes to an African's entire genome, there might be more difference between him and his next-door neighbor than between Dirk Nowitzki and Ichiro Suzuki. In fact, the farther a group of native people is from Africa, the less genetically diverse it tends to be. In some sections of DNA, Kidd says, there is more variation within a single African Pygmy population than in the entire rest of the world combined. "In that sense," Kidd says, "I like to say that all Europeans look alike."
This has tremendous implications. In some cases, for example, classifying people solely according to their dark skin will impart no genetically based knowledge about the group's members other than that they have dark skin. Take, for another example, sports. Kidd suggests that for any activity that has a genetic component, the world's most naturally gifted person is likely to be African (or recently removed from Africa, as are African-Americans and Afro-Caribbeans), as is the world's least naturally gifted individual. So both the fastest and slowest runners might well be of recent African descent.
That's not to say that scouts should be looking for the next MJ or Usain among African Pygmies. "There are some anatomical features that would intervene," says Kidd, referring to the Pygmies' short legs, but he adds that "you might find the most naturally gifted basketball players in some of those populations in Africa where height and coordination are on average very high, and where you have a lot of other genetic variation within that group."
Of course, the only real way to test this idea would be to know which genes influence athleticism, and then to look for them in the genomes of the world's best athletes.