Human ancestors could stand on two legs before they even descended from the trees

(ORDO NEWS) — Traditionally, scientists believe that our distant ancestors switched to a bipedal lifestyle when their forest habitats began to give way to open spaces.

However, observations of wild chimpanzees have shown that in order to stand on two legs, it is not necessary to descend from the trees.

For a long time, anthropologists believed that the need to move between separate patches of forest scattered across the open savanna contributed to the emergence of the habit of rising on two hind legs among our distant ancestors.

In tall grass, at the risk of becoming prey to predators, these ancient primates had to constantly look around and, in addition, not expose their backs to the scorching sun, which forced them to tear their forelimbs off the ground.

Some of our closest biological relatives still live in similar environments: for example, chimpanzees from the Issa Valley in western Tanzania inhabit small patches of forest punctuated by dry savannah.

And although these monkeys often rise on two legs, the researchers were surprised to find that most often they do this not at all on the ground.

To find out, scientists from the University of California (USA) analyzed about 2,850 videos of the locomotor behavior of 13 adult chimpanzees (six males and seven females), especially noting where the action took place – on the ground or in trees.

Although the researchers expected to see Tanzanian chimpanzees on the ground more often, they actually spent as much time in the trees as their relatives from other, more forested parts of Africa.

What’s more, the majority of bipedal walking about 85 percent was recorded in trees as monkeys walked along branches.

In other words, it is quite possible that it was not the drying up of the habitat and the replacement of forests by the savannah that forced human ancestors to become bipedal: they rose on both hind limbs, while still being a purely arboreal species.

Thus, one of the main characteristics of modern man – the ability to move on its hind limbs – most likely did not develop due to climate change, because chimpanzees in a similar habitat are in no hurry to descend from trees and successfully master bipedal walking, standing on branches.

Now scientists have to conduct additional observations of monkeys in different parts of the range to try to solve this evolutionary puzzle.


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