Fossilized Jaw Sheds Light on the Origins of Early Humans (VIDEO)

A fossilized jaw may tell scientists a bit more about early humans. The new jaw pushes back evidence for the human genus, Homo, to 2.8 million years ago, which pushes back the previous estimate by about 400,000 years.

Scientists have long searched for African fossils that document the earliest phases of the Homo lineage. However, specimens recovered that are dated between 3 and 2.5 million years ago have been few and poorly preserved. The new fossil, though, sheds some light on human evolution.

The jaw actually reveals advanced features; for example, it has slim molars, symmetrical premolars and an evenly proportioned jaw. This distinguished early species on the Homo lineage from the more apelike Australopithecus. However, the primitive, sloping chin links the jaw, known as the Ledi-Geraru jaw, to a Lucy-like ancestor.

"The Ledi jaw helps narrow the evolutionary gap between Australopithecus and early Homo," said William Kimbel, one of the researchers, in a news release. "It's an excellent case of a transitional fossil in a critical time period in human evolution."

The jaw doesn't just close a gap in human evolution. It also tells researchers a bit more about the time period in which this species existed. Global climate change led to increased African aridity after about 2.8 million years ago. This means that the change was contemporary with this jaw.

"We can see the 2.8 million year aridity signal in the Ledi-Geraru faunal community," said Key Reed, co-leader of the research team. "But it's still too soon to say that this means climate change is responsible for the origin of Homo. We need a larger sample of hominin fossils, and that's why we continue to come to the Ledi-Geraru area to search."

The findings are published in the journal Science.

Want to learn more? Check out the video below, courtesy of Vimeo.

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