14 DAY TRIAL // Modern humans, Homo sapiens, evolved from ape-like ancestors because they needed to run long distances, this ability shaping our anatomy, researchers Dennis Bramble and Daniel Lieberman announced.
This conclusion is contrary to the conventional theory that running simply was a byproduct of the human ability to walk.
Bipedalism evolved in the ape-like Australopithecus at least 4.5 million years ago while they also retained the ability to travel through the trees and the Homo genus with its "radically transformed body" did not evolve for another 3 million or more years. Because of this, the ability to walk cannot explain anatomy of the modern human body.
"There were 2.5 million to 3 million years of bipedal walking [by australopithecines] without ever looking like a human, so is walking going to be what suddenly transforms the hominid body?" biologist Dennis Bramble rhetorically asks.
Walking cannot explain most of the changes in body form that distinguish Homo from Australopithecus, which, when compared to Homo, had short legs, long forearms, high permanently "shrugged" shoulders, ankles that were not visibly apparent. He adds that if natural selection had not favored running, the human species would have looked a lot like apes.
Bramble and Lieberman examined 26 traits of the human body, many also seen in fossils of Homo erectus and some in Homo habilis that enhanced the ability to run. Only some of them were needed for walking. Traits that aided running include leg and foot tendons and ligaments that act like springs, foot and toe structure that allows efficient use of the feet to push off and shoulders that rotate independently of the head and neck to allow better balance.
An interesting proof supporting the theory launched by the two researchers is the large size of the human buttocks. Bramble compares them with those of monkeys.
"Have you ever looked at an ape? They have no buns," the researcher said. Bramble added that human buttocks "are muscles critical for stabilization in running".
Image credit: Laszlo Meszoly, Harvard University