Fossil jaw pushes human origins back 400,000 years

Chuck Bednar for – @BednarChuck

Researchers from the US, UK, and Africa have discovered a new lower jawbone in Ethiopia that pushes back the arrival of the genus Homo on that continent by nearly one-half million years, all but confirming that East Africa was the birthplace of our evolutionary lineage.

According to BBC News, the 2.8 million-year-old partial mandible is 400,000 years older than experts previously believed that our kind had emerged, and the discovery suggests that climate change was the catalyst that caused us to evolve from tree dweller to upright walkers.

University of Nevada-Las Vegas professor Brian Villmoare, lead author of a paper describing the research that was published Wednesday in the journal Science, said that the discovery offers new insight into “the most important transitions in human evolution”.

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He added that the find provides a clear link to “Lucy,” a 3.2 million-year-old human-like primate discovered in 1974.

Next-door neighbors

In fact, as National Geographic pointed out, the new specimen (dubbed LD 350-1) was found just a dozen miles from where Lucy has discovered. LD 350-1 was recovered from the Ledi-Geraru research area in the East African Rift Valley’s Afar Regional State in January 2013, and the authors note it is one of only a few Homo fossils from that period have been found.

“You could put them all into a small shoe box and still have room for a good pair of shoes,” Bill Kimbel, director of the Institute of Human Origins at Arizona State University, told Nat Geo. LD 350-1 shares several features with later members of the genus, including slim molar teeth and the shape of the mandible’s bony body, but has a primitive-looking front and a receding chin line.

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“This narrows the time period in which we can now focus our search for the emergence of the human lineage,” added Kimbel, who co-led the analysis of the new specimen. “It’s very much a transitional form, as would be expected at that age. The chin looks backwards in time. But the shape of the teeth looks forward.”

Evolutionary insight

The find could help provide new insights into the extremely essential but poorly understood part of human evolution that occurred between two and three million years ago, when our ancestors began the critical transformation from ape-like mammals into more advanced forms capable of tool use, The Guardian said. It helps close the gap from Australopithethus to Homo.

“By finding this jaw bone we’ve figured out where that trajectory started. This is the first Homo. It marks in all likelihood a major adaptive transition,” Villamoare told the newspaper, adding that dramatic changes in the environment may have been what let to the transformation. “It could be that there was some sort of ecological shift and humans had to evolve or go extinct.”

Handy man

A related study, published this week in the journal Nature, describes a reconstruction of an earlier specimen – a Homo fossil one million years younger than LD 350-1, according to Nat Geo. The jaw belonged to the original specimen of Homo habilis or “Handy Man,” which was discovered by Louis and Mary Leakey Tanzania’s Olduvai Gorge in 1964.

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Fred Spoor of University College, London and the Max Planck Institute for Evolutionary Anthropology and his colleagues used computed tomography (CT) and 3D imaging technology to digitally reconstruct what that specimen’s mandible would have looked like, and according to the website, it would have a narrow shape and parallel tooth rows similar to an australopithecine, the group of human ancestors that predates the Homo genus.


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