Scientists have found a 2.8 million year old jawbone in the Ledi-Geraru research area, Afar Regional State in Ethiopia. They claim in the press release that this is one of the first human’s jaw bone and is almost 400,000 years old.

The head of the research team told BBC News that this was a significant discovery that provides a very important insight into the transitions in human evolution. The species belongs to the genus ‘homo’ just as human beings are but the bone belongs to the earliest phases of the human family, the Australopithecus afarensis species.

Rresearch team co-leader and study co-author Brian Villmoare, a paleoanthropologist at the University of Nevada in Las Vegas, told Live Science that up until now there was no record of the ancestors of Homo. A 3.2 million year old fossil of a homini, which is a human like primate was discovered in the same area and he states that the discovery makes a clear link between them. He explained to BBC that there was always a gap between this discovery of the homini and the emergence of the erect human form with properly proportioned, human like structures. This discovery bridges the one million year gap and provides huge insights into the evolution of man.

The fossil was found by team member Chalachew Seyoum in 2013. The fossil is of the left side of the lower jaw with five teeth. The molar were smaller to the homini discovered. The bone was dated by analysing the volcanic ash present above and below it. Villmoare explained, "When volcanoes erupt, they send out a layer of ash that contains radioactive isotopes and these isotopes start going through radioactive decay.” These layers were dated back to find out the age of the bone.

Villmoare however, told Live Science that the traits found in the bone are a mixture of Homo and Australopithecus. They are also not sure as to whether the fossil belongs to a new species or an old extinct human species like the Homo habilis.

"We can see the 2.8 million-year-old aridity signal in the Ledi-Geraru faunal community," Research team co-leader and study co-author Kaye Reed of Arizona State University said in a statement that climate change can be a possible reason behind the origin of Homo. He pointed that 2.8 million years ago the climate change had intensified. However, this is only a probable reason and a definite conclusion cannot be brought about just by this observation, he states.

Prof Chris Stringer from the Natural History Museum, London told BBC News that this is a big story but it leaves several questions unanswered and gives rise to several other questions. It does not even provide enough information to come to a conclusion that this was the first human, he states.

Prof Stringer added, "These new studies leave us with an even more complex picture of early humans than we thought, and they challenge us to consider the very definition of what it is to be human.”

The findings are detailed in their online paper, published in the journal Science.

View pictures of the fossil here.

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