Tumai walked well 7 million years ago, but not only

Toomai, the oldest known member of mankind, walked well on two legs seven million years ago but retained the ability to climb trees, according to a study published Wednesday in the journal Nature and based on three bones belonging to a member of his species. , Sahelanthropus chadensis.

The story begins in Toros Menalla, in northern Chad, when the skull was discovered by a French-Chadian paleoanthropological mission team in 2001. Sahelanthropus tchadensis, Toumaï for those close to him, then supplants Orrorin tugenensis, six million years old and found in Kenya, as the oldest known human species.

The position of the foramen magnum in Tumai’s skull, with the vertebrae positioned under the skull rather than behind it as in a quadruped, makes it a bipedal primate. Several experts have disputed this conclusion, arguing that the fossil is incomplete.

A study by scientists from PALEVOPRIM, the evolution laboratory of the University of Poitiers, CNRS and scientists from Chad makes a decisive contribution to this discovery.

“The skull tells us that Sahelanthropus is part of the human race,” Frank Guy, a paleoanthropologist and one of the study’s authors, explained on Tuesday. The latter demonstrates that “upright walking was his preferred mode of transportation depending on the situation,” he added during a press conference.

This bipedalism was “common, but not exclusive, with a bit of arboreal realism”, in other words, the ability to move through trees. Legacy of a hypothetical common ancestor of humans and chimpanzees.

The team demonstrates this with a detailed study of the femur and two bones of the forearm, the ulna. Bones that we will never know if they were consistent with the individual Tumai, but found in the same place and belong, like him, to the bones of the hominin, the human line.

Scientists at the Franco-Chadian mission have been studying them for several years, conducting an exhaustive set of tests and measurements. They identified 23 morphological and functional characters before comparing them with those of other living and fossil hominids and great apes.

Their conclusion is that “the set of these traits is much closer to what would be seen in a hominin than in any other primate,” said Guillaume Daver, paleoanthropologist of the PALEVOPRIM team and first author of the study, during a press conference. . .

For example, while the gorilla or chimpanzee, the closest relative of man, moves forward by leaning on the back of the phalanges of the hand, this is not observed in Sahelanthropus.

– forests and wet savanna –

The person whose bones were studied in this way weighed between 43 and 50 kg. The bare desert landscape in which his house stands today was in his time a mixed forest with palm groves and humid savannah. A structure conducive to both walking and “cautious” quadruped in foliage.

In doing so, the study provides “a fuller picture of Toumai and finally the first humans,” paleoanthropologist Antoine Balzot of the National Museum of Natural History told AFP, applauding the “extremely informative” work.

This provides additional arguments for supporters of the “dense” evolution of the human lineage with many branches, contrary to the “simplified idea of ​​​​people following one another, with abilities that improve over time,” notes Mr. Balzo. .

What made Sahelanthropus human was its ability to adapt to a given environment, according to the PALEVOPRIM researchers, who stressed the importance of not viewing bipedalism as a “magical trait” that strictly defines humanity.

In an article accompanying the study, Daniel Lieberman, professor of evolutionary biology at Harvard, said the study does not yet offer a “final answer” to the question of Tumai’s nature.

The PALEVOPRIM team intends to resume its research in Chad next spring, “security permitting,” Mr Guy said. Because, as Chadian palaeontologist Clarissa Nekulnang of the National Center for Research and Development has pointed out, teams on site are “trying to find sites older than Tumai.”

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