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Saturday, March 7, 2015

Jawbone found in Ethiopia set to rewrite history, push back origins of humans

6 March, 2015 - 22:17 lizleafloor
An extraordinary fossil find in the desert of Ethiopia is pushing back the dawn of humankind by approximately half a million years, and rewriting what we know about the evolutionary branching that eventually led to modern humans.

A fossilized lower jaw, with five small teeth, is reportedly connecting the dots between primitive ancestors and modern humans. The specimen is the bone of one of the very first humans – it represents the oldest known human genus Homo - and comes from a time when humans split from the more ape-like ancestors, Australopithecus, identified by the best known fossil skeleton “Lucy”, according to CBC News.
‘The Hidden Treasures of Ethiopa’ exhibit at Houston Museum of Natural Science featuring a model of “Lucy”, Australopithecus Afarensis. Jason Kuffer/Flickr

The find is more than 400,000 years older than the oldest fossils belonging to the early humans who eventually gave rise to Homo sapiens, our modern species.

The jawbone was found close to where Lucy was discovered in 1974. The specimen of Australopithecus afarensis, dubbed Lucy, is from 3.2 million years ago. The species walked upright, but only stood a meter tall and had a small brain. This contrasts with the species Homo,characterized by an upright, bipedal posture, sophisticated tool-making abilities and a relatively large braincase”, reports BBC News. The Ethiopian jawbone seems to share traits similar to both species, and may be a transitional fossil, filling in an evolutionary gap.
The Ledi-Geraru jawbone. Credit: William Kimbel/Arizona State University

Graduate student of Arizona State University in the U.S., Chalachew Seyoum pulled the 2.8 million-year-old jawbone from the earth at the Ledi-Geraru research area in Ethiopia in 2013. “The moment I found it, I realized that it was important, as this is the time period represented by few (human) fossils in Eastern Africa,” he tells BBC News.
Researchers examine soil at the Ledi-Geraru site in Ethiopia, where Homo jawbone, known as LD 350-1, was discovered. Credit: Brian Villmoare

Side view of Australopithecus afarensis (“Lucy”), replica. Wikimedia Commons

Paleoanthropologist Brian Villmoare of University of Nevada, and colleagues published a study in the journal Science on the research into the jawbone. 

Villmoare says, “In spite of a lot of searching, fossils on the Homo lineage older than two million years ago are very rare. To have a glimpse of the very earliest phase of our lineage’s evolution is particularly exciting.”
Field work is being done in the Ledi-Geraru site to see if more fossils can be recovered. More information could help determine if the jaw belongs to a known early species of Homo, or an entirely new species, and researchers are putting off definitively naming it for the time being.

Recent examinations of fossilized human teeth in China and a prehistoric jawbone from Taiwan have been raising questions about the established theories on the history of modern humans, suggesting there may be many species yet uncategorized.

The rare Ethiopian find may help scientists answer vital questions about what prompted the transition from primitive to modern humans. The Science study suggests that environmental changes may have caused a shift in the lives and diet of ancient ancestors. Fossilized plant and animal analysis indicates that lush forest transitioned to dry grassland, and early humans may have adapted according to the new survival needs. However, scientists wait on a larger sample of hominid fossils in order to prove this conclusively.
A mix of hominid (genus Homo) depictions; (from right to left) H. habilis, H. ergaster, H. erectus; H. antecessor - male, female, H. heidelbergensis; H. neanderthalensis - girl, male, H. sapiens sapiens. Public Domain

Prof Fred Spoor of University College London and the Max Planck Institute for Evolutionary Anthropology in Leipzig tells BBC News, “By discovering a new fossil and re-analysing an old one we have truly contributed to our knowledge of our own evolutionary period, stretching over a million years that had been shrouded in mystery.”

Featured Image: The 2.8 million-year-old fossilized jawbone with small teeth which may be a transitional fossil between primitive and modern man. Credit: Brian Villmoare