The oldest fossil of the human genus Homo has been unearthed in Ethiopia, a groundbreaking discovery that pushes the history of human evolution 400,000 years further into the past.

Found at a site known as Ledi-Geraru, the fossil of a jaw with five teeth still intact predates the previously known fossils of the Homo lineage and shows that our ancestors lived amid grasslands, shrubs and forest some 2.8 million years ago.

"What is special about this jaw is not only the date, which is much older than any specimen of Homo known until now, but that is has a unique combination of traits, from the height of the mandible to the shape of the teeth, that makes it clearly transitional between Australopithecus and Homo," said Brian Villmoare, of the University Of Nevada Las Vegas and one of the co-authors on two studies announcing the discovery in Science.