A new analysis of ancient leg and arm bones found in Chad in 2001 led researchers to conclude that one of our earliest known ancestors walked upright 7 million years ago.
A new study published Wednesday in the science journal Nature suggests that our ability to walk on two legs, or bipedalism, developed “soon after humans and chimpanzees diverged.”
About 20 years ago, researchers in Chad discovered the nearly complete skull of Sahelanthropus tchadensis, the ancient species of ape-man. They also found bones of arms and legs nearby. The skull found had an opening in the middle of the skull that was oriented downwards, suggesting that “like bipeds, Sahelanthropus balanced its head on a vertical neck,” writes human evolution expert Daniel Lieberman in Nature.
However, not all scientists agree that the skull provided sufficient evidence of bipedalism, according to the Associated Press. Some believe that similar traits between Sahelanthropus and humans may have developed independently.
Scientists Guillaume Daver and Franck Guy, authors of the study, used bones from the left thigh (femur) and forearm (ulnae) “not previously described” to confirm their original findings. They found that the femur bone had “human-like” features and looked “more like a bipedal hominid than a quadrupedal ape,” Lieberman explained.
On the other hand, the forearm bones looked “unquestionably chimpanzee-like”, with features of arms that could climb trees well.
Based on the evidence the researchers gathered while studying the skull and femur, they determined that the ape-man likely walked upright but could also climb well, Lieberman wrote.
Aside from that inference, scientists don’t really have a lot of information about what kind of walks this species had, he said.
“We know little else about the Sahelanthropus march,” Lieberman said. “A mixed repertoire of walking and climbing makes sense, as Sahelanthropus lived near a lake with woods adjacent to it.”
In addition, there are still many features that Sahelanthropus has in common with chimpanzees, he wrote.
“This similarity makes sense if the last common ancestor of humans and chimpanzees was chimpanzee-like and Sahelanthropus evolved shortly after the human-chimpanzee divergence,” Lieberman said.
The findings of this study are significant because the development of bipedalism is considered “a decisive step in human evolution,” according to a press release from Université de Poitiers in France, whose researchers were involved in the new study as well as a study previous. bone study in 2005.
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