French Paleontologists Claim Oldest Homo Ancestor Could Walk

The oldest known ancestor of humankind walked on two legs but could still climb trees like an ape, a study of some 7 million-year-old bones suggests. Researchers analyzed the fossil remains of Sahelanthropus tchadensis, unearthed 21 years ago in the deserts of Chad, central Africa.

Photo Insert: A replica of the skull of the Sahelanthropus tchadensis

At the time, the discovery was said to have had “the impact of a small nuclear bomb” as it pushed back the ancestral line of hominids – the line leading to Homo sapiens – by a million years, closer to the split with chimpanzees, Sascha Pare and Nicola Davis reported for Live Science.

The question as to whether the species walked upright remained unanswered. Now, a team in France say they are “pretty confident” that Sahelanthropus was indeed bipedal. But other experts have expressed doubts about the study, published in the journal Nature, sparking debate about the lifestyle of Sahelanthropus and even whether it sits on our evolutionary branch or not.

The researchers examined a thigh bone and two forearm bones from the site in the Toros-Menalla region of Chad’s Djurab Desert. They analyzed 23 features of the fossils that they say point to bipedalism and indicate a closer relationship to humankind.

“We can conclude from the evidence that we have habitual bipedalism, plus quadrupedal arborealism, which is what is observed for early hominids and then gradually turns into the obligate bipedalism in Homo,” said Jean-Renaud Boisserie, a co-author of the study from the University of Poitiers. Even the 3-million-year-old skeleton of Lucy, suggests bipedalism is a defining feature of our lineage.

“We are pretty confident,” said Franck Guy, also a co-author. “What we show is that the morphological pattern of the femur is more similar to what we know in humans, including fossil humans, than in apes.”

Prof. Bernard Wood, of George Washington University, who was a co-author of a previous study that concluded Sahelanthropus was not habitually bipedal, said: “These critically important fossils deserve better treatment than this shoddy paper provides. The study cherrypicks evidence, ignores recent studies that point to different conclusions than the ones the authors try to defend, and it fails to explore other equally, if not more likely, functional interpretations of these fossils. All of the three bones resemble chimpanzees more closely than any other living great ape, including modern humans. That does not mean Sahelanthropus was a chimpanzee, but it was likely closely related to chimpanzees, and its lifestyle was chimpanzee-like. It was not an upright, ground-living ape of the kind that were likely to have been our earliest ancestors.”

Prof. Fred Spoor, an expert in human origins at the Natural History Museum in London, who was not involved in the research, said the new study suggesting Sahelanthropus did walk on two legs appeared convincing.

“I think what is striking, in this case, is that as far back as 7m years ago, so close to the potential split with the line to chimpanzees, that even then there is a recognizable signal for bipedal behavior. It really looks like being two-legged, being bipedal, is the defining nature of our evolutionary tree,” he said.

Dr. Sandra Martelli, an associate professor at University College London, who was also not involved in the study, said: “The type of bipedal locomotion cannot be decided on the evidence presented, it could be arboreal or ground or both, and is mixed with climbing.”

WEEKLY FEATURE : MVP Group Keeps Lights On During Pandemic