No one has ever doubted that, in the beginning, primitive man learned to walk before he could run. But how about it taking three million years for that second part after the whole walking thing was already down? Or, when it finally happened, the idea that simply being able to run radically propelled our evolution as a species?
That's the conclusion from new research authored by University of Utah biology professor Dennis Bramble and Harvard anthropologist Daniel Lieberman and published in Thursday's edition of the journal Nature.
Their work suggests that primitive man's evolution from walking to running was an instrumental step in human evolution forsaking the capacity to live in trees, but vastly improving the species' ability to find food. They also hypothesize that running preceded brain enlargement and may have precipitated brain development by allowing primitive man to locate and consume more protein.
"The structure of specializations required for hunting are sort of counter to those that are useful for climbing," Bramble said. "We sort of favor the notion that humans may have evolved running initially to increase their intake. But not through hunting probably through scavenging."
Several anatomical changes enabled early man to run, according to the study, including a narrowed waist, shorter forearms, larger buttocks and skull modifications allowing the body to cool itself.
Previously, researchers hadn't much focused on running, instead considering it simply a byproduct of walking. But Bramble points to specific adaptations not used in walking like the Achilles tendon as evidence that man wasn't capable of running until evolution accommodated it.
"It turns out that that's a terrific spring, and it makes a huge difference in the economy of running, but it makes no difference in walking," he said of the Achilles.
Bramble said scientists might have overlooked the importance of running because humans aren't considered particularly fast especially in comparison with four-legged animals.
However, Bramble says endurance, more than speed, was the key for early man enabled by adaptations allowing the body to cool itself and function over long distances.
Furthermore, Bramble suggests that early runners could even have been faster than our contemporaries, perhaps in part because projectile hunting weapons made running less necessary as humans evolved.
"Some of our ancestors very likely could have been better runners than some of the best runners today," he said.