Why Did Humans Evolve?

It is pretty well known that humans evolved from ape-like ancestors. But let’s ask evolution study’s most important question: why?  What traits caused humans to diverge into a completely new species from our primate ancestors?

The answer, according to University of Utah biologist Dennis Bramble and Harvard University anthropologist Daniel Lieberman, is the ability to run. Bramble and Lieberman concluded that modern humans (Homos) evolved from ape-like ancestors called Australopithecus because they needed to run long distances. Two million years ago, natural selection favored the Australopithecus that could run – perhaps because they could outrun predators, or more efficiently hunt animals or scavenge carcasses. Over time, the body shape of the Australopithecus changed as new body features that favored long-distance running were selected, giving rise to the genus Homo.

Humans evolved from apes because of the advantageous ability to run long distances.

 

 This theory contradicts the popular theory that running arose as a by-product of bipedalism in our already human ancestors. However, bipedalism was a trait that evolved at least four and a half million years ago in our ape-like ancestors the Australopithecus. This species walked on two legs, but it also retained the ape-like ability to travel through trees. It was not until three millions years after the evolution of bipedalism that our ancestral species began to run. Learning to run came at the cost of no longer being able to travel through trees, and marked a significant transition of our ancestors from ape-like to human-like. 

Walking does not explain the radical transformation of the ape-like body that occurred and resulted in humans, since our first walking ancestors were still markedly ape-like. As Australopithecus began to run long distances, their features transformed, eventually giving rise to Homo species. For example, changes to the head such as a flatter face, smaller teeth, and a shorter snout shifted the center of mass back so that balancing the head became easier while bobbing up and down during running. The detaching of the shoulders from the head and neck allowed rotation of the body while the head looked forward during running.

If running had not arisen, these features would not have changed and we might still be very ape-like today (more so than we already are)! Therefore, the evolution of running marked a key event on the evolutionary timeline of modern man.

-Author: Nupur Jain

References:

Lieberman, Daniel E., and Dennis M. Bramble. 2007. The evolution of marathon running: Capabilities in humans. Sports Medicine 37(4-5): 288-290.

Photo from: http://coasthillsrunningclub.com/