The fossil remains found in a cave in South Africa could represent an evolutionary link between tree-dwelling apes and our earliest human ancestors to walk upright
Fossil skull of Australopithecus sediba, a possible human ancestor found in cave deposits at Malapa, South Africa. Reconstruction courtesy of Paul Tafforeau, Lee Berger, the ESRF, Grenoble and the University of the Witwatersrand Link to this video
Fossilised skeletons recovered from a deep underground cave in South Africa belong to a previously unknown species of human ancestor, scientists claim.
The partial skeletons of an adult female and a young male, aged 11 or 12, were found lying side by side in sediments that first covered their remains an estimated 1.9m years ago.
The individuals are thought to have fallen into the cave network through a fissure before being carried a few metres by mud or water into a subterranean pool, where they were gradually encased in rock.
The extraordinary remains are thought to represent a period of evolutionary transition between tree-dwelling apes and the earliest human ancestors, or hominids, to take their first tentative steps on two feet. Their position at the very root of our family tree has led scientists to claim that the skeletons will help define what it means to be human.
The remains were recovered alongside the fossilised bones of at least 25 other animals, including sabre-toothed cats, a hyena, a wild dog, several antelope and a horse, according to two reports in the journal Science. At the time the creatures died, the region was dominated by a grassy plain crossed by wooded valleys.
The discovery of the mass grave has led researchers to suggest that the ancient animals and the hominids fell into the cave network through "death trap" holes in the surface and were unable to escape. The skeletons were so well preserved that palaeontologists believe the two individuals fell into the cave together and were dead and buried within days or weeks.
The remains, found in the Malapa cave network at the Cradle of Humankind World Heritage Site 40km outside Johannesburg, have already triggered a row over their identity, because they share anatomical features with both early humans from the genus, Homo, and their ancient predecessors, the Australopithecines, or southern apes.
The skeletons have long arms similar to those of orang-utans, a trait shared with Australopithecines, which suggests they were adept at living in trees. But unlike other Australopithecines, they have long legs and a pelvis that is well adapted to walking upright. Analysis of the male's skull revealed small teeth and facial characteristics seen in early members of the genus Homo. Their brains were exceptionally small, around a third the size of a modern human's.
Ian Sample, science correspondent guardian.co.uk, Thursday 8 April 2010
