Study: Fossil Bones Add to Evidence about Earliest Ancestor

2022-09-03

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  • Researchers say new examinations of arm and leg fossils support existing evidence that an identified species could be our earliest known ancestor.
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  • The fossil bones were found near a skull that was discovered in 2001 in the African nation of Chad.
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  • The scientists who found the skull have suggested that it belonged to a being who walked upright and could be our earliest known ancestor.
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  • Now, researchers say a study involving the arm and leg fossils strengthens that argument.
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  • The team looked for signs that the species walked on two feet instead of four.
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  • The move toward upright walking is a main division between human and ape development.
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  • The fossil species, called Sahelanthropus tchadensis, walked upright while still being able to climb and move around in trees, the team said.
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  • The species dates back to around seven million years ago, which makes it by far the oldest known human ancestor.
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  • That is about a million years older than other early known hominins.
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  • Hominin is a group that includes modern humans and species closely related to humans.
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  • Researchers - including scientists at the University of Poitiers in France - closely examined the fossil skull, teeth and jaw.
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  • They argued that the animal must have walked on two feet and held its head upright.
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  • This argument was based on the placement of a hole in the skull where the spinal cord connects to the brain.
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  • Other experts, however, have not been persuaded, or convinced, by the early evidence.
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  • The latest work includes a thigh bone that was not linked to S. tchadensis at first and went unstudied for years.
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  • Other researchers at the French university found the bone in the laboratory's collection and realized it probably belonged to the fossil species.
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  • Compared to bones from other species, the thigh was linked closer to upright-walking humans than apes who used their feet and arms, the study found.
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  • The new findings were recently reported in the publication Nature.
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  • Study co-writer Franck Guy recently spoke about the fossil examinations to reporters. "There is not one feature.
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  • There is just a total pattern of features," he said.
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  • The debate over the species is likely to continue.
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  • Ashley Hammond is a scientist at the American Museum of Natural History in New York.
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  • She said more research is needed to find the being's rightful place on the evolutionary tree.
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  • "I'm not fully convinced yet," Hammond told The Associated Press. "This could still also be a fossil ape."
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  • Another researcher at the University of Poitiers, Roberto Macchiarelli, examined the thigh bone in the past and decided the species was probably an ape.
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  • Looking at the new study, Macchiarelli said he still does not believe the species was a hominin, though it might have walked on two legs at times.
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  • Rick Potts is with the Smithsonian's National Museum of Natural History and directs the organization's Human Origins Program.
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  • He said the thigh bone puts the species on "better footing" as a possible early human ancestor.
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  • But he added that the real confirmation will come down to a common saying in the field: "Show me more fossils."
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  • I'm Bryan Lynn.