THURSDAY, Nov. 18, 2004 (HealthDayNews) -- Millions of years before headphone-wearing joggers clotted the streets of America, the development of the ability to run played a crucial role in the evolution of early humans, according to new research.
Without running, our bodies might have turned out looking like those of apes, said Harvard University anthropology professor Daniel Lieberman, co-author of a new study in the Nov. 18 issue of Nature. "This ability of ours to run incredibly long distances rather efficiently is incredibly rare. It's unique," he said. "No other primates like to run, or are even good at it."
By developing bodies that allow for running, humans may have boosted their ability to both hunt and scavenge for food, Lieberman said. And that could have helped humans gain dominance in the world with one major cost: the ability to easily climb trees, which apparently disappeared as human bodies developed bodies designed for running instead.
Lieberman and a colleague, biology professor Dennis Bramble of the University of Utah, became interested in the development of running several years ago when they watched a pig run on a treadmill. "He looked at that pig and said, 'That pig can't hold its head still,' and sure enough, the pig was wobbling its head around from side to side," Lieberman recalled. By contrast, "when you look at a human running, they're terrific. We're like pogo sticks. If you watch someone running, particularly someone who has a ponytail, that ponytail will be bobbing up and down, but the eyes of the runner will be stable like a missile. We wondered how on earth we do that."
Lieberman and Bramble began studying early humans and found that the Homo erectus species seemed to have developed bodies that tolerated running, much like horses and dogs. By contrast, our chimp ancestors can sprint for short distances, "but they're terrible runners," Lieberman said. "They can't go for very long, and they get exhausted quickly."
The researchers found numerous physical traits that evolved in humans and appear to be critical to the ability to run: head designs that prevent overheating and allow humans to see the world as they run without too much jiggling; a ligament in the back that acts as a kind of shock absorber; shorter forearms that allow for better counterbalancing of the upper and lower bodies; and huge buttocks that provide stabilization.
As they evolved to run instead of just walk, humans lost their ability to scamper around trees. Why run instead of climb? "We think it had to do with getting protein, scavenging," Lieberman said. "Imagine you're a hungry Homo erectus," an early form of human. "You wonder how you're going to feed yourself, and you see some vultures in the distance. When the lions leave it, there will be the rest of the skeleton full of marrow, fat, protein, and also brains. The lions don't eat that. If you just walk over there and get it, the hyenas will be there before you."
Hence the need to run, which also helped early humans hunt, Lieberman said.
What about now? Will humans continue to evolve the ability to run? Lieberman doesn't think so. "We've paid a price," he said, "for sedentism."
More information
To learn more about evolution, try this PBS documentary.
