We are all African...

THE GENETIC PLAYBOOK

AT THE CENTER of our every cell lies the twisting ladder of the double helix. A mere four molecules—adenine, cytosine, guanine and thymine—pair off three billion times to make up our DNA, the instruction manual for our bodies. Twenty-five thousand sections of each DNA ladder are especially important. They are genes, and it is they that actually tell the body how to build itself.

In April 2003 an international consortium of scientists announced the completion of the Human Genome Project. After 13 years of work (and 200,000 years of modern man), the project had mapped the human genome; all 25,000 regions of DNA that contain genes had been identified. Now researchers knew where to begin looking for the biological foundations of many of our traits, from hair color to hereditary disease to athleticism.

But even if scientists know where the most important parts of the manual are located, they don't necessarily know how to read them. In fact, the precise functions of most genes, including many so-called sports-performance genes, remain mysterious, and thus talk of splicing DNA to create the perfect athlete is a bit premature.

Already, though, scientific research gives us a fuller picture of how we evolved into athletes, and it suggests that some things that appear to be largely genetic (such as East African dominance of distance running) might not be, and that other things that seem entirely voluntary (such as an athlete's will to train) might in fact have an important genetic component.

Scientific studies that associate particular genes with athleticism are published literally every month. These genes exist, in differing versions, in all of us, from All-Pro to average Joe. As the study of performance genes accelerates, more assumptions about sports and genetics will no doubt prove false, and new answers will reshape our view of why and how some people become NFL running backs or Olympic swimmers while others struggle to pass phys ed.

The findings are already raising ethical, social and even economic questions. Yet even as the research explains many of our athletic differences, it may reveal more important biological truths about us as a single humanity.

WE ARE BECAUSE WE RUN

IN OUR GENES we are all distance runners. Let's start at the cusp, just before humans became the earth's marathoners. Two-and-a-half-million years ago, our ancestors lived in the trees of the East African woodland, foraging for fruit and digging up tubers. They were wide-hipped, hunched and hairy, and the giants among them were all of five feet tall. But their world was changing dramatically. Their forest home had begun to give way to hot, dry savanna, with few trees and with grass short enough to give sight lines that stretched until the earth curved away. Our forebears saw for the first time the hordes of wildebeest and antelope that filled the plain.

Gradually these ancient, mostly vegetarian primates dropped from the trees and went looking for steak. Initially they might have used vultures as their guides, racing hyenas to scavenge the leftover brains and bone marrow of dead antelopes. For the first time in history a two-legged mammal had reason to run long. Those who could jog in the punishing equatorial heat could beat the hyenas to a carcass. They could survive another day, perhaps long enough to have children.

The major changes that took hold in the body over the next half-million years were examined in 2004 by biologists Dennis Bramble of the University of Utah and Daniel Lieberman of Harvard. Their conclusion contradicted the common assumption that human running was simply a by-product of walking. Nearly every one of the major anatomical changes en route to modern man, the professors argued, conspired to make him the hot-weather endurance running champion of the savanna.

There is, for instance, the rubbery neck ligament that acts like a shock absorber for the head during running; the glut of sweat glands to help keep the body cool while running; the lack of body fur for the same reason; shoulders that move, unlike in apes, independently from the neck so that the arms can swing while the head remains still; long legs and narrow waists; larger surface areas in hip, knee and ankle joints, again for improved shock absorption; short toes, which are better for pushing off than for grasping tree branches; an arched foot, which acts as a spring; and big butt muscles to keep us upright. "Have you ever looked at an ape? They have no buns," Bramble says. "We think running is one of the most transforming events in human history."

No longer content merely to scavenge, our ancestors, despite having no greater weapons than sticks and stones, became deadly hunters. They overwhelmed their perspirationally challenged quarry with a methodical chase that lasted until the beasts, unable to pant sufficiently while fleeing, simply gave up from heat exhaustion.

Descartes said we are because we think, but consider that we thought only after we ran. Even our large brains developed because we ran, growing only once our endurance enabled us to gorge on animal fat and protein. We are who we are—the only sweating, largely hairless bipedal mammals—because we ran. As Lieberman puts it, "Endurance running is hardwired into our anatomy and physiology."

For decades running was considered an unimportant part of human evolution because we humans are such pathetic wimps at sprinting. In his world-record 200-meter dash, Usain Bolt averaged a little more than 23 mph for nearly 20 seconds. That would make him an abject failure as a savanna hunter because an antelope can double that clip for minutes at a time. But with the help of our upright stance (which exposes less of our bodies to the sun) and our profuse sweating, we can outrun just about any other animal on the planet if the race extends over hours in searing midday heat.

Sound far-fetched? Consider that humans have beaten horses in the 22-mile Man Versus Horse Marathon in Wales, and humans routinely win the 50-mile Man Against Horse Race in Prescott, Ariz. And note that in Southern Africa a small number of San Bushmen, the world's oldest community of modern humans, still hunt by separating an antelope from its pack and chasing it for hours in 105° heat, until the animal simply stops running and waits to be killed. Or note that any Tom, **** or Oprah can complete a marathon with proper training and sensible pacing.

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 AFRICAN of 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.

Run for the African in you!!

Go Ge' em!!

Research compliments of: www.americanscientist.org, www.moreintelligentlife.com, Human Genome Project and www.reuters.com