NEW YORK ( Associated Press) — Twenty years ago, scientists discovered a 7-million-year-old skull that they concluded belonged to an upright creature that was our earliest known ancestor. Not everyone was convinced. Now, the researchers provide more evidence that they say strengthens their hypothesis.
In a new study published Wednesday, they analyzed hand and foot fossils found near skulls in Africa to show that they walked on two legs instead of four. Upright walking was a pivotal moment in the separation between early humans and apes.
In the report published in the journal Nature, researchers again place the organism on the human side of that evolutionary divide. The fossil species, called Sahelanthropus tchadensis, walked upright and was able to climb trees, he noted.
The species is dated to about seven million years ago, making it the oldest known human ancestor to date. It is about a million years older than any other known hominin.
It has been a source of intense debate since the discovery of the fossils in Chad in 2001.
First, researchers led by scientists from the University of Poitiers in France looked at the creature’s skull, teeth and jaws. He argued that it should walk on two legs and keep its head upright based on the location of the hole in the skull where the spinal cord connects to the brain.
Other experts weren’t convinced by the first evidence.
The latest research involves a thigh bone that was initially found in S. tachadensis and was not studied for years. Other researchers from a French university found the bone in the laboratory catalog and felt it probably belonged to a fossil species.
According to the study, compared to the bones of other species, the femur resembles that of humans, who walk more upright than apes that walk on knuckles.
“There is not a single feature. There is a whole pattern of features,” said one of the co-authors, Frank Guy, of the analysis during a press conference.
Nevertheless, the debate around the species may continue.
Ashley Hammond, a scientist at the American Museum of Natural History in New York, said more research is needed to find the creature’s location on the evolutionary tree.
“I’m still not completely convinced,” Hammond said. “It could even be a fossil of an ape.”
Roberto Macchiarelli, another researcher at the French center, had previously examined the bone and determined that the species was likely an ape. In light of the new study, Macciarelli said he still didn’t believe it was a hominid, even though it may have walked on two legs at times.
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