A partial jawbone found in Ethiopia is the oldest human-related fossil, scientists say.

NPR's Christopher Joyce, who is reporting on the story, tells our Newscast unit that the discovery fills in an important gap in human evolution. He says:

"The fossil consists of a partial jawbone and several teeth. It dates to about 2.8 million years ago."The team says the fossil appears to belong to an individual from the beginning of the ancestral line that led to humans. That would make it the earliest known Homo — the human genus."Writing in the journal Science, the researchers say the jaw and teeth are different from more ancient human ancestors, known as Australopithecus. Those apelike creatures had broad teeth for grinding and deep jaws."The new fossil has smaller teeth and a more rounded jaw. It's 400,000 years older than the previous record for human-related fossils. The scientists say it comes from the earliest period of human evolution."

The fossil was discovered two years ago at a location in Ethiopia close to where Lucy— the skeleton of the sort of half-ape, half-human that lived a couple of million years before humans evolved — was discovered.

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