Ancient Human Ancestor Walked on Two Legs 7 Million Years Ago, Scientists Find

The switch to walking on two legs is a major moment in the evolution of our species, which is why scientists are interested in knowing when it happened.

That is based on a detailed analysis of thigh and forearm fossils from the oldest species of humans. In 2001, these fossils were found in Chad.

If the species made the gradual shift from four legs to two legs, it's likely these early hominins did a fair bit of tree climbing.

New insights into bipedalism at the early stage of hominin evolutionary history were presented in the paper.

By comparing the thigh and forearm fossils with the equivalent bones from humans, Chimpanzees, and gorillas, the researchers were able to figure out how this species moved around.

The outer shape of the bones, as well as the internal structures, were used to determine if S. tchadensis walked on two legs or four.

Habitual bipedality is the most likely scenario.

There is a difference between the way the species climbed trees compared to today's Chimpanzees andGorillas, with firm hand grips, instead of leaning back on finger and toe bones.

The researchers say that the cross-sectional geometric properties of the ulna are indicative of arboreal behaviors, such as climbing andcautious climbing.

A skull fossil dug up at the same site is thought to belong to S. tchadensis, according to the research. There is more conclusive evidence that these ape-like creatures were not bipedal as previously thought.

It's a crucial stage, and one that has already attracted a lot of scientific debate, because the fossils date from around the time when humans split off from Chimpanzees and bonobo, which are our closest living relatives.

The early hominins are thought to have lived in an environment that mixed forests, palm groves and grassland, with both walking on two legs and climbing up trees as they looked for food and water.

According to the researchers, the most parsimonious hypothesis is that the postcranial morphology is indicative of bipedality and that any other hypothesis would have less explanatory power for the set of features presented by the material fromChad.

The research was published in a journal.