Washington, Apr 14 (ANI): A new study from Worcester State College in Massachusetts has revealed that our ancient human ancestors were poor climbers and they traded their ability of climbing trees for the power to walk on two legs.
According to anthropologist Jeremy DeSilva, early humans lacked the ankle structure that assists chimps- our closest living animal relatives - in climbing.
During the study, DeSilva videotaped wild chimpanzees in Uganda to study their bodies while climbing.
He measured the angle of dorsiflexion, or how far the ankle could rotate so that the toes point upward, and found that chimps can make much more extreme ankle rotations than modern humans.
He later analysed whether early hominins were more like modern humans or chimpanzees. He looked at the ankle bones in fossils of human ancestors at various times from 1.5 million to 4 million years ago.
DeSilva discovered that early humans during this span have dorsiflexion ranges similar to those of modern humans, and couldn't have climbed trees in quite the same way as chimps do, if they climbed at all.
"Frankly, I thought I was going to find that early humans would be quite capable, but their ankle morphology was decidedly maladaptive for the kind of climbing I was seeing in chimps," Live Science quoted DeSilva as saying.
"It kind of reinvented in my mind what they were doing and how they could have survived in an African savannah without the ability to go up in the trees," he added.
As tree climbing was useful both for foraging food and for hiding from predators, the benefits of walking upright, say researchers, must have made humans give up their ankles more suited for climbing.
"I think by 3 [million] to 4 million years ago that tradeoff was occurring," he said.
"Our ancestors were becoming very capable upright walkers, and it came at the expense to our ability to climb trees," he added.
Other research suggests that early humans at this time had limb proportions similar to other mammal species that are particularly aggressive. Perhaps early humans used aggression to discourage predators from targeting them.
Moreover, walking on two feet not only enabled travelling long distances, but also escaping more quickly on the ground from predators.
The findings appear in journal Proceedings of the National Academy of Sciences. (ANI)