Sediba human ancestor could shift our origins to South Africa

08 September 2011

At almost 2 million years old, a human-like species from caves at Malapa in South Africa may be the ancestor to the first humans, and may shift the likely location of early human origins from East Africa to South Africa, scientists report in the journal Science today.

Reconstruction of the Australopithecus sediba skull. Berger's team detected many human features.

Reconstruction of the Australopithecus sediba skull. Berger's team detected many human features although the brain cavity was small and ape-sized. Scans were made at the European Synchrotron Radiation Facility in Grenoble, France. © Dr Kristian Carlson/ Wits University

Two fossil skeletons belonging to a new species Australopithecus sediba were first unveiled in April 2010 by Professor Lee Berger of the University of Witwatersrand, South Africa, and his colleagues.

Australopithecines, known as ‘southern apes’, shared similarities with both apes and humans and lived around 1.5 to 4.2 million years ago.

Australopithecus sediba is the most human-like australopithecine ever discovered and now Berger’s team have carried out further research on the same fossils.

New date for Sediba

They obtained a new and more accurate date for the age of A. sediba of 1.98 million years, which corresponds to the time when the first humans (genus Homo) began to evolve.

More human features

Analysis of the 2 well-preserved fossil skeletons revealed even more human features than the last study.

Professor Chris Stringer, human origins expert at the Natural History Museum and author of the new book The Origin of Our Species, comments on this new research, ‘Australopithecus sediba resembles its presumed local ancestor Australopithecus africanus in its ape-sized brain, ape-like body shape, and the form of the shoulders and arms.

Fossil bones of A. sediba's hand that showed more human-like features as well as a powerful grip

Fossil bones of Australopithecus sediba's hand show human-like features as well as an ape-like powerful grip. © Peter Schmid 1/ Wits University

‘Yet despite the fact that the hands had a powerful grip, they show more human proportions, suggesting greater dexterity.

‘The shape of the front of the brain cavity, the face, teeth, pelvis and legs also show more human characteristics, confirming that A. sediba is the most human-like australopithecine yet discovered, providing valuable clues to the evolutionary changes that led to the genus Homo.’

The results mean A. sediba could be a transitional species, providing a snapshot of Australopithecus to Homo evolution in action.

Shift to South Africa?

For the last 30 years, most scientists have put East Africa as the place where the first humans (genus Homo) evolved, around 2 million years ago. 

This is where fossil evidence, such as from Homo erectus, Homo habilis, and the famous 'Lucy', Australopithecus afarensis, were uncovered.

‘In that view, the South African australopithecines were side-branches in human evolution, leading only to extinction.’ says Stringer.

Pelvis of Australopithecus sediba adult female

Pelvis of A. sediba adult female © Peter Schmid/ Wits University

‘However, the new and detailed descriptions of the skeletons of 2 individuals from the Malapa site return the spotlight to South Africa as the possible location for the postulated transition from Australopithecus to Homo.

‘Nevertheless, it is possible that australopithecines in different parts of Africa were taking up tool making, meat eating and travelling longer distances overground, which could have driven the parallel evolution of human-like features.'

Modern humans, Homo sapiens, evolved in Africa around 200,000 years ago, and are thought to be descendants of these first humans.

Rare human skeletons

The A. sediba fossils are among the most complete ancient human finds ever (Sediba means fountain or natural spring in the seSotho language). 

Professor Lee Berger of the University of Witwatersrand, South Africa,

Professor Lee Berger of the University of Witwatersrand, South Africa, with the A. sediba skull. © Wits University

One skeleton belongs to a child of about 12 years of age and includes a near-complete skull and jaw, teeth, parts of the pelvis, ribs, upper and lower legs and upper arms. The other belongs to an adult female and includes a near-complete wrist and hand.

Other fossils of early human relatives have been discovered, but often only as fragments of bones or teeth.

The most complete ancient hominin (human-like) skeleton, from 4.4 million years ago, was Ardipithecus ramidus, or 'Ardi', revealed in October 2009. Ardi had a brain and body the size of a chimpanzee's as well as human-like small canine teeth and flexible hands and wrists.

And, perhaps the most famous skeleton of an early human relative belonged to the 3.2-million-year-old 'Lucy', Australopithecus afarensis, uncovered in 1974.

Sediba cast display and event at the Museum this year

On the 16th November 2011 the Museum will be lucky enough to receive its own cast of the A. sediba skull, which will go on display in the public galleries.

And on the same date, Chris Stringer and Lee Berger will be taking part in a free Museum Nature Live event about A. sediba at 2:30pm in the Darwin Centre.

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