A new report challenges the theory that Sahelanthropus tchadensis, a hominid that lived more than 6 million years ago, was our earliest known human ancestor.
French paleontologists uncovered a Sahelanthropus in Chad almost two decades ago.
Calling it ‘Toumai’, they heralded the creature as an early biped – with a skull indicating that it had an upright spine.
But a new report suggests that Toumai is just an ancient primate, more closely related to a chimpanzee than a human.
Researchers base their claims on the shape of the femur, which they say belongs to Toumi.
They maintain the femur, curved like a monkey, was deliberately left unexamined because it would have discredited the theory he walked on two feet.
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The French paleontologist Michel Brunet discovered the remains of Sahelanthropus tchadensis in northern Chad in 2001. Brunet maintains the creature, called ‘Toumai’, walked on two legs more than 6 million years ago and is humanity’s oldest known ancestor
The French paleontologist Michel Brunet first discovered the remains of a Sahelanthropus in the Djurab desert of northern Chad in 2001.
Brunet, a researcher at the University of Poitiers in France, was nicknamed the specimen ‘Toumai’ and maintained in a 2002 nature report that it was divided into two parts.
His main evidence was that the base of the skull would have been connected by an upright spine.
Using radiometric dating, his team decided that Toumai was between 6.8 and 7.2 million years old and lived at some point in the Miocene era.
The brunette holding the bottom of the Tumai’s skull shows that it would have rested on an upright spine. But doubts about whether the Sahelanthropus was bipedal have only grown with the release of a new report suggesting that the creature’s femur shows that it walked on all fours, like a monkey
This makes Toumai more than twice as old as mankind’s oldest known ancestor, ‘Lucy’, discovered in Ethiopia in 1974 and dated to about 3.2 million years ago.
A left femur and two forearms were also discovered, but for some reason Brunet never published anything about them, and few other researchers had access to the bones.
In 2004, Aude Bergeret-Medina, a researcher at Poitiers, identified an unmarked bone as a femur – probably theorizing from a primate.
Eventually, she and her mentor, paleoanthropologist Roberto Macchiarelli, came to believe that they had fallen over Toumai’s femur.
Aude Bergeret-Medina, a researcher at Poitiers, identified an unmarked bone as Tumai’s femur. The femur is not straight but curved, which Bergeret-Medina said is more typical of a monkey
But after Bergeret-Medina took measurements and photographs, the leg disappeared and no scientist saw it again.
When Brunet’s team could not publish anything about the femur, she and Macchiarelli used her notes and prepared their own report.
They tried to present their findings at a conference held by the Anthropological Society in Paris, but were rejected.
Their hypothesis that Toumai did not stand upright was finally published in the December 2020 issue of the Journal of Human Evolution.
Photos of the femur were examined by Bergeret-Medina and her mentor, Roberto Macchiarelli. Macchiarelli claims that Brunet blocked access to the femur itself because it would discredit the theory that Toumai went on two legs
According to the report, the femur is not straight but curved, which is more typical of a monkey.
Others have doubted that Toumai has been a human father in the past.
Shortly after Brunet’s initial findings were published, Milford Wolpoff, a professor of anthropology at the University of Michigan, questioned them.
‘Toumai may be a common ancestor of apes and humans, but it is not on the line that directly leads to humans,’ Wolpoff wrote in a letter to Nature. ‘We think Toumai is a monkey and we think it’s probably a woman because of her dog’s teeth.’
The teeth were small, he said, but they could still easily belong to a female gorilla or a chimpanzee.
Wolpoff also pointed to scars on the skull left by the neck muscles, claiming that they suggest Toumai walked on all fours with his head horizontal to the spine.
A rendering of what Sahelanthropus tchadensis may have looked like when it was alive
Geographer Alain Beauvilain, who helped excavate Toumai, has even raised questions about where and when the bones were found – suggesting they were disturbed by locals at some point in the past.
In September, paleontologist Franck Guy, a co-author of the original Sahelanthropus paper, released a separate study that doubled the bipedal theory.
He claimed that the femur has a hard back near the top, which supports an upright body.
But his report was sent on a preprint server, which means it has not yet been peer reviewed.
Brunet still believes that his Sahelanthropus is a missing link in the family tree of mankind.
‘Toumai’s skull is essentially a hominid skull,’ he told China’s state Xinhua News Agency in 2019. It has a ‘very small’ dog tooth, like a human. ‘Only dogs can prove that it’s not a big monkey.’
Macchiarelli claims that Brunet and his colleagues have blocked access to the femur and had his presentation blackballed because it would discredit their theory that Toumai walked on two feet.
But Brunet insists that ‘there is no controversy.’
‘No one can scientifically say that femur belongs to Toumai.’