Fossil in Ethopia pushes back human origins

Mar 04, 2015, 3:04 PM EST
Andrew Barr (L) and Amelia Villasenor study human environments in East Africa at the Center for the Advanced Study of Paleobiology at George Washington University's new science and engineering research center in Washington, DC on February, 26, 2015.
The Washington Post/Getty Images

A fossil of a jaw found in Ethiopia has been determined to be 400,000 years older than other specimens of human existence which date back 2.35 million years. This latest fossil dates back 2.8 million years, challenging the suspected dates of the origins of human existence. The BBC reports:

The discovery in Ethiopia suggests climate change spurred the transition from tree dweller to upright walker.
The head of the research team told BBC News that the find gives the first insight into "the most important transitions in human evolution".
Prof Brian Villmoare of the University of Nevada in Las Vegas said the discovery makes a clear link between an iconic 3.2 million-year-old hominin (human-like primate) discovered in the same area in 1974, called "Lucy".
Could Lucy's kind - which belonged to the species Australopithecus afarensis - have evolved into the very first primitive humans?
"That's what we are arguing," said Prof Villmoare.
But the fossil record between the time period when Lucy and her kin were alive and the emergence of Homo erectus (with its relatively large brain and humanlike body proportions) two million years ago is sparse.
Consistent with its early age, the jaw blends primitive and modern features. Its curve, the shape of the teeth and the arrangements of their cusps are all characteristically human. But the chin is decidedly not; it slopes backward, like that of an ape. “The anatomical characteristics are a very interesting mix that looks back toward Lucy and forward to more advanced species of Homo,” says study co-author William Kimbel, a paleoanthropologist at Arizona State University.
Positioned as it is in the fossil record, the find helps to fill in a chapter in human evolution that has long been relatively blank. Before about 3 million years ago, our hominid relatives bore a strong resemblance to apes. After about 2 million years ago, they look much more like modern humans. What happened in the middle is poorly understood, and only a handful of fossils from this time period have so far turned up.
Further excavations at Ledi-Geraru provided clues as to what might have driven this transition. Sandy sediments and the fossilized remains of animals indicate that the climate in the area started to shift as early as about 2.8 million years ago.