When it comes to sprinting, we humans lag far behind the cheetah, a dog, even an elephant.
But we excel at distance running. In fact, we're the best distance runners in the animal kingdom. Why is this? Could it be that distance running made us human?
Imagine, if you will, the most important, highest-stakes marathon race of all time–a literal life-or-death struggle, like those two-person gladiator contests in the Roman Colisseum. The marathon winner will survive, the loser will die. This race might sound like a fictional event, or next season's newest Reality TV show, but it's not. It actually took place two million years ago.
The Evolution Marathon began at high noon on a sweltering day in east Africa. In an earlier epoch, this area had been covered by dense forest, where long-armed chimps gamboled through the branches, searching for sweet fruit. Then the climate turned drier, the trees receded, and grassy savannahs filled the gap. Some of the chimps adapted well, dropped down from the trees, and took their first awkward steps on two legs. Yet life was tenuous for these pre-humans. They lived on the brink of starvation.
On the day of the Evolution Marathon, two of these nearly identical pre-humans are desperately searching for a meal. Let's call them Sam and Dave. Glancing skyward, Sam and Dave spot a kettle of vultures circling in the distance. They know what this means: There's a weakened wildebeest below. A wildebeest represents the best food imaginable, chockablock with carbohydrates, protein, and fat–luscious, calorie-dense fat. The race is on!
Ordinarily, Sam and Dave would have no chance of reaching the wildebeest before Africa's powerful lions or pugnacious scavengers, but the Evolution Marathon begins at high noon, remember? Africa snoozes at noon; it's no time for exercise. Sam and Dave aren't fans of hot-weather marathons either–do you know anyone who is?–but they are the most highly motivated runners of all time. Each realizes that he must catch the wildebeest, or die from starvation.
As the two pre-humans began loping across the sandy grasslands, several physical differences become apparent. Sam has less hair than Dave, and more sweat glands; his body cools itself better. He has a bigger, more muscular butt than Dave. He has a developing Achilles tendon and a high arch in his foot; these provide more "energy return" with each stride. Sam's shoulders drop farther below the neck than Dave's, and his arms are shorter; this gives him a more efficient upper-body rotation to counterbalance the rapid rotation of his legs. Though these are small differences, they add up quickly. In the same way, a modern runner becomes an Olympic champion, while his one-percent-disadvantaged rival has nothing to show but a dusty scrapbook.
Sam beats Dave by a mile. He enjoys wildebeest steak for lunch, his belly grows full, and he lives for another day. Having proven himself a great hunter, he finds sexual partners, and passes his genes to future generations. Two million years in the future, one of them will cover a 26.2-mile marathon in two hours, four minutes.
Pity poor Sam, the second-place finisher. He starves and dies.
When Charles Darwin termed similar competitions a "survival of the fittest," he wasn't referring to vo2 max, lactate threshold, and running economy, the usual measures of a runner's ability. But in terms of human evolution, that's more or less what it amounts to, according to university professors Dennis Bramble and Daniel Lieberman. They believe that Running Made Us Human–that is, that early man's talent for endurance running led directly to our present, large-brained selves. That's the argument they made three years ago in a Nature magazine cover story, and it's a case they're still building.