The query of whether or not a 7-million-year-old primate, nicknamed ‘Toumai,’ walked on two or 4 legs has whipped up drama amongst palaeontologists – full with a vanishing femur.
Since the invention of Sahelanthropus tchadensis’s first fossil again in 2001, it has typically been cited as our earliest known hominin ancestor. Initial analysis urged that Sahelanthropus usually walked upright and had a mix of ape-like and human-like options.
These conclusions, nevertheless, have been based mostly on a single cranium.
The cranium has anatomical options that doubtlessly point out this primate had an erect backbone, and subsequently spent a few of its time strolling on two legs solely. Its small tooth additionally seem extra human than ape-like. A later reconstruction supported these findings.
But different researchers have since argued that this alone is just not sufficient proof to class Sahelanthropus as a hominin biped – a primate straight ancestral to people – reasonably than a associated, however circuitously ancestral hominid.
Around the identical time and on the identical location the place the cranium was discovered, in Toros-Menalla in Chad, a partial left femur was additionally recovered. The femur vanished after one other researcher began to look at it in 2004, having come across it supposedly by chance.
Aude Bergeret-Medina and her supervisor, palaeoanthropologist Roberto Macchiarelli from the University of Poitiers in France, ultimately continued their evaluation based mostly on measurements and photographs. They have just published their findings, which solid doubt on Sahelanthropus’s place in our household tree.
“Based on our analyses, the partial femur lacks any feature consistent with regular bouts of terrestrial bipedal travel,” Macchiarelli and crew write in their paper.
“Thus, if there’s compelling proof that S. tchadensis is a stem hominin, then bipedalism can not be seen as a requirement for inclusion within the hominin clade.”
Meanwhile, one other palaeontologist, Martin Pickford from the French National Museum of Natural History, wonders if the femur even belongs to Toumai, or at the least one other Sahelanthropus.
Still, others agree with Macchiarelli’s evaluation of the femur.
“I saw the pictures 10 or 12 years ago, and it was clear to me that it’s more similar to a chimp than to any other hominin,” University of Tübingen palaeontologist Madelaine Böhme, who was not concerned in any of the research, told New Scientist.
Analysis of molecular variations in our DNA means that people parted methods with chimpanzees and bonobos (our closest nonetheless residing relations), round 6-Eight million years in the past. The solely different fossil proof of a doable hominin from that point is from Orrorin tugenensis.
Macchiarelli and crew in contrast the femur with one from O. tugenensis and decided that there is at the least species-level distinction between them.
fter additionally evaluating them with Australopithecus, gorillas, and trendy people, they imagine these variations recommend the mode of locomotion of the 2 oldest species was additionally completely different.
They suspect Sahelanthropus could also be an ancestral relative with no remaining residing descendants – a primate lineage that went extinct.
They additionally level out others have urged the small tooth discovered within the original study might simply point out the primate is feminine. But the crew agrees that fascinating questions nonetheless stay, notably across the traces that we use to outline what precisely makes a primate a human, quoting a 2017 paper of their conclusion:
“Exactly where in Africa, and under what circumstances, the ape-human demarcation began, and when, how and why the ape-human boundary became irrevocably established, are important research challenges that are still unresolved.”
We’ll want many extra fossils earlier than we all know the solutions.
This analysis was revealed within the Journal of Human Evolution.