March 4, 2015 9:17 PM EST

A handful of teeth and a partial jawbone unearthed in Ethiopia are now thought to be the oldest fossil ever found of the species that evolved into humans, researchers say in a new report.

The U.S.-led team that discovered the fossil a couple hundred miles away from the capital, Addis Ababa, believe the remains are some 2.8 million years old, making the fossil around 400,000 years older than other discovered remains thought to be from the Homo genus, which scientists believe to be our lineage.

The researchers reported their findings in the journal Science and said they have could help fill in some evolutionary gaps that are still uncertain. Prior to the genus Homo, there was the hominid Australopithecus afarensis. Researchers say the specifics of the evolution between the two during that time is still unknown.

“By finding this jaw bone we’ve figured out where that trajectory started. This is the first Homo,” study author Brian Villmoare of the University of Nevada in Las Vegas told The Guardian. “It marks in all likelihood a major adaptive transition.”

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