Accidental Fossil Discovery Throws New Light on Human Evolution

An analysis of fossils that are nearly two million years old suggests that they come from a species that may be a leading candidate as an ancient ancestor to humans, say paleontologists.

The new species is known as Australopithecus sediba.

The fossils were discovered by Lee Berger of the University of Witwatersrand from the Malapa site in South Africa in 2008. Berger's 9-yer-old son had been chasing their dog, Tau, when he stumbled upon a rock. He took it to his father. Lee immediately realized it was a fossil.

The analysis shows that from this vanished species, many human traits such as long thumbs, upright walking and wide hips have evolved.

It is known that Africa is the birthplace of humanity. It was in Africa that Australopithecine, who are the ancestors of humans and modern apes, originated over several million years ago. This has been shown by fossils and genetic evidence.

The fossils of Australopithecus sediba are about 4 feet tall.

The size of the brain is less than one-third the size of a modern human's. At the same time, the analysis team has reported that the features preserved on their inner skull resemble the specialized brain areas found in modern humans.

A. Sediba had hands capable of using tools. Also, they were strong enough for grasping tree branches.

A. Sediba had a more curved pelvis that would have theoretically accommodated a bigger brain on its way through the birth canal even though it still had small heads.

The variety of characteristics is indicating that A. sediba was at an evolutionary transition point between the tree-climbing australopithecines and upright-walking, often tool-using members of the genus Homo, including Homo sapiens.

Dr. Berger and his colleagues have presented this claim in five articles in the current issue of Science that describe various aspects of the new fossils.

The mix of primitive and modern features led Berger and colleagues to suggest that A. sediba could be an ancestor to the genus Homo.

At the same time the age of the fossils presents a problem. The researchers' isotopic and magnetic dating showed the fossils were 1.977 million years old, about 300,000 years younger than a Homo habilis fossil that should have been their junior.