The story begins in Toros-Ménalla, in northern Chad, when in 2001 a team from the Franco-Chadian paleoanthropological mission unearthed a skull. Sahelanthropus tchadensisToumaï for those close to him, then ousts Orrorin tugenensis6 million years old and discovered in Kenya, as the oldest known representative of humanity.
The position of the foramen magnum in the skull of Toumaï, with a vertebral column located under the skull and not behind as in a quadruped, places it as a bipedal primate. A few specialists have disputed this conclusion, arguing that the fossil is incomplete.
The study by researchers from PALEVOPRIM, the evolution laboratory of the University of Poitiers, the CNRS as well as Chadian academics makes a decisive contribution to this discovery.
bipedalism was his preferred mode of locomotion, depending on the situationhe added during a press conference.
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. Bones which we will never know if they were those corresponding to the individual Toumaï, but found on the same site and belonging like him to those of a hominin, the human line.
The scientists of the Franco-Chadian mission studied them, over several years, with an exhaustive battery of tests and measurements. They identified 23 morphological and functional traits, before comparing them with those of other living 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 primatesaid Guillaume Daver, paleoanthropologist of the PALEVOPRIM team and first author of the study, during the press conference.
For example, whereas in quadruped mode a gorilla or a chimpanzee, the closest cousin of man, advances by leaning on the back of the phalanges of his hand, this behavior is not observed with Sahelanthropus.
Moist forests and savannah
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
cautious in the foliage.
The study thus provides
a more complete picture of Toumaï and eventually the first humansremarked to AFP the paleoanthropologist Antoine Balzeau, of the National Museum of Natural History, welcoming a work
It 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 timeremarks Mr. Balzeau.
which made Sahelanthropus human, it was his ability to adapt to a given environment, according to the PALEVOPRIM researchers, who insisted on the importance of not seeing bipedalism as a
magic character strictly defining humanity.
In an article accompanying the study, Daniel Lieberman, professor of evolutionary biology at Harvard, believes that the study 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. Because 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.