ZAP // James H. / Flickr; Didier Descouens / Wikipedia
Reconstruction (left) and replica (right) of the skull of the holotype of Sahelanthropus tchadensis TM 266-01-060-1, called Toumaï, in faciolateral view
According to a new analysis of its fossilized bones, a controversial hominid that lived 7 million years ago may after all have walked on two legs — making it a direct ancestor of humans.
After its discovery in 2001, the Sahelanthropus tchadensisor Toumaïwas considered human, but some scientists argue that would rather be a distant cousin and not a direct human ancestor.
Much of the debate focuses on whether this primate, one of the lost species of , habitually moved on two legsor if he walked with the help of his hands, as the chimpanzees and current gorillas.
Now, a new study, led by scientists at New York University and published this Friday in Science Advances, may have resolved the issue: o S. tchadensis is our direct ancestor.
“Our analysis of these fossils offers direct evidence that the Sahelanthropus tchadensis could walk on two legsdemonstrating that bipedalism evolved early in our lineage and from an ancestor similar to today’s chimpanzees and bonobos”, he states Scott Williamsanthropologist at New York University, in a statement published on .
The researchers reached this conclusion through 3D geometric analysis of the bones of the creature’s arms and legs, comparing them with the same bones in related species, both current and extinct.
The study authors say they identified three key characteristics indicators of bipedalism.
On the one hand, they found a torsion in the femur which helps the legs point forward and makes walking easier. Secondly, the S. tchadensis seems to have had gluteal muscles well developed, important for stabilizing the basin.
Both characteristics had previously been identified by other scientists. But, according to the team, “irrefutable proof” of this new work was the discovery of a femoral tubercle — a type of anchor point for a robust ligament that connects the pelvis to the femur, fundamental for bipedalism and until now only known in hominids.
Williams et al. / Sciences Advances
Fossils of Sahelanthropus tchadensis (TM 266) compared with a chimpanzee and a human
This does not mean, however, that the S. tchadensis had completely abandoned the habits of climbing trees.
“O Sahelanthropus tchadensis was, essentially, a bipedal apewith a brain the size of a chimpanzee, and which probably spent much of its time in trees, looking for food and safety”, explains Williams. “Despite its superficial appearance, Sahelanthropus was adapted to posture and bipedal locomotion on the ground”.
There is still no definitive consensus that allows us to establish that the S. tchadensis is a hominid, as opposed to an apeo, because there is not enough evidence. “More fossils would be welcome”, explains Williams, quoted by . But the S. tchadensis appears to have been our most remote ancestor.
