Jawbone fossil in Ethiopia sheds light on human origins

A piece of jawbone with teeth attached, uncovered in Ethiopia, is the earliest known fossil of the genus Homo, to which humans belong, researchers have said.

The discovery suggests that humankind's ancestors were living in what is now the Ledi-Geraru research area of Afar Regional State, Ethiopia, in open grassland environments, near lakes, rivers, and active volcanoes, about 2.8 million years ago, or 400,000 years earlier than previously thought.

"It is the first fossil we have on the branch that leads toward us," said Brian Villmoare, assistant professor at the University of Nevada in the US, who is lead author of the study in the journal Science.

The jawbone, known as LD 350-1, is the lower left side of a mandible with five teeth, and was found in fine sediment near the surface of the research site in 2013. The fossil has not yet been assigned to a particular species, but its slim molars and dental arch proportions indicate an advancement that is not seen in the more ape-like Australopithecus afarensis, dating just a few hundred thousand years earlier.

Experts described the fossil as a very early representative of the species that led to modern humans, though not a direct ancestor of our particular species, known as Homo sapiens.

Researchers are particularly intrigued because the fossil dates to a period when few such artefacts have been found and sheds light on the time when early hominids diverged, as the ancestors of Homo sapiens split from the more ape-like Australopithecus, which walked upright but had smaller brains.