Toumaï, the oldest known representative of humanity, walked well on two feet seven million years ago

Was Toumaï bipedal? The question has been hovering since the discovery, in 2001, of a skull seven million years in northern Chad. For the team from the Franco-Chadian paleoanthropological mission that brought it to light, Sahelanthropus tchadensis – better known under the name of Toumaï – then ousts Orrorin tugenensissix million years old, discovered in Kenya, as the oldest known representative of mankind.

The position of the foramen magnum in the skull of Toumaï, which supposes a vertebral column located under the skull and not behind as in a quadruped, designates him indeed as a bipedal primate. Rare specialists have however disputed this conclusion, arguing the incomplete state of the fossil.

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A study, published Wednesday August 24 in Nature, which rests on three bones belonging to an individual of the species to which Toumaï belonged, makes a decisive contribution to this discovery. It shows that the latter walked well on both feet seven million years ago.

“The skull tells us that Sahelanthropus is part of the human line”, explained Tuesday the paleoanthropologist Franck Guy, one of the authors of the study carried out by researchers of Palevoprim – the laboratory of the evolution of the university of Poitiers -, of the CNRS, as well as Chadian academics. This study demonstrates that “bipedalism was his preferred mode of locomotion, depending on the situation”he added during a press conference.

Biped, but not only

This bipedalism was “usual, but not only, with also a little bit of arborealism”, in other words the ability to move in the trees. A legacy of the hypothetical common ancestor of the human line and that of chimpanzees.

The team demonstrates this with the detailed study of a femur and two bones of the forearm, the ulna. Remains of which we will never know if they were those of the individual Toumaï, but which were found on the site where it was discovered and belong to those of a hominin, the human line.

The individual whose bones were thus studied weighed between 43 and 50 kilos. The bare desert landscape that today hosts his remains mixed forests with palm groves and humid savannah in his time. A framework that promotes both walking and quadrupeds “careful” in the foliage.

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Scientists from the Franco-Chadian mission studied his bones for several years. They identified twenty-three morphological and functional traits, which they compared with those of other extant and fossil hominins and great apes.

Their conclusion is that “All of these character traits are much closer to what we would see in a hominin than in any other primate”, said Guillaume Daver, paleoanthropologist of the Palevoprim team and first author of the study, during the press conference. For example, using quadrupedism, a gorilla or a chimpanzee, man’s closest cousin, advances by leaning on the back of the phalanges of the hand, which is not observed in Sahelanthropus.

“A more complete picture of Toumaï”

The study thus provides “a more complete picture of Toumaï, and ultimately of the first humans”noted the paleoanthropologist Antoine Balzeau, of the National Museum of Natural History, welcoming a work “extremely substantial”.

This study brings additional arguments to the proponents of an evolution “bushy” of the human line, with multiple branches, going against a “simplistic image of humans succeeding each other, with abilities improving over time”remarks Mr. Balzeau.

which made Sahelanthropus human was his ability to adapt to a given environment, according to the Palevoprim researchers, who stressed the importance of not seeing bipedalism as a “magical character” strictly defining humanity.

In an article accompanying the study, Daniel Lieberman, professor of evolutionary biology at Harvard, believes that it does not yet offer ” final solution “ to the question of the nature of Toumaï.

The Palevoprim team intends to resume its research in Chad next spring, “if security permits”, Mr. Guy said. As indicated by the Chadian paleontologist Clarisse Nekoulnang, of the National Center for Research and Development, the teams on site “try to find sites older than Toumaï”.

The World with AFP