A new study published in the journal Nature shows that our ancestors already walked upright 7 million years ago.

In 2001, researchers found fossils at an archaeological site in the Djurab desert in Chad, a country in north-central Africa. In 2002, these bones were described as a new human species, Sahelanthropus tchadensis Since then, the ossada receives disputes from scientists, since it is the first human species - as soon as it separated from the rest of the primates.

"In most respects, it looks like an ape," Harvard University paleoanthropologist Daniel Lerberman, who was not involved with the study, told Smithsonian Magazine, "but there are some really important features that make it look like it's in the human lineage."

Lieberman points out that the "most important of these features is that it looks like a biped.

This fossil may be the earliest known hominid, and possibly the first line of humans to separate from the Chimpanzee lineage. Although possibly bipedal, it also had similarities with Chimpanzees. The arms of the skeletons found, for example, indicate that they lived for quite some time in trees. By sharing these similarities, it is believed to beof the branch of humans and chimpanzees, the most recent branch of the primate family.

Djurab Desert, where researchers found the bones in 2001. Image: MPFT, PALEVOPRIM / CNRS - University of Poitiers

Did our ancestors walk upright as early as 7 million years ago?

Initial studies, in 2005, had first shown evidence of bipedism in the Sahelanthropus. As Smithsonian Magazine reports, the passage connecting the spinal cord to the brain points downward in the skulls of animals that walk upright, like humans. In quadrupeds, on the other hand, this connection points backward.

Therefore, as a rule, this connection is vertical in bipeds and horizontal in quadrupeds. This already brought the initial evidence of this point. However, this point as evidence was not consensual among scientists. The question if our ancestors already walked upright 7 million years ago was done, but how to enter this point?

At first, the discovery of the animal's skull, forearm bones, and femur bones were not listed as a single discovery. Then, later, the pieces were all attributed to a single individual.

Twenty years after the discovery of the bones, scientists have completed the extremely detailed descriptions.The femur of the Sahelanthropus was essential to establish whether our ancestors were already walking upright seven million years ago.

Analyzing the femur

The task of actually determining whether our ancestors already walked upright 7 million years ago started to get a little challenging, since it would not be that simple to analyze that femur. The bone no longer had joints at its ends - points that would bring the main clues to put an end to this debate. An analysis of the neck of the femur or the knees would shed light on the question.

Scientists work on the ossada that brought the debate whether our ancestors already walked upright 7 million years ago. Image: Franck Guy / PALEVOPRIM / CNRS - University of Poitiers

"It was very challenging, too, because the bone was gnawed probably by a porcupine," study co-author Jean-Renaud Boisserie told Smithsonian Magazine.

So the scientists had to resort to a bit of technology.

As Boisserie reports, "a great deal of information has been preserved in both the external morphology and internal structures that we access using computed microtomography."

To seek the result, scientists needed to compare more than twenty traces of femur and forearm bones, with those of living chimpanzees, gorillas and orangutans, as well as some fossils of apes and bipedal hominids.

However, the bottom line on whether ancestors were already walking upright 7 million years ago has yet to be put in place. A 2020 study looking at the same bones says the individual was not habitually bipedal.

"The two teams that collected data from the femur seem to disagree entirely on what the femur shows," said researcher John Hawks of the University of Wisconsin-Madison. "They're looking at the same piece of bone, I don't understand how they disagree on that."

Hawks argues that they should release the data for examination. That way, academia could put an end to the story - did our ancestors walk upright as early as 7 million years ago, or not? This ossada is important because it may be one of the first species since the lineage of humans separated from chimpanzees.