Science Cover

A group of researchers, led by renowned Wits University professor, Lee Berger, has finally described, in this week’s issue of Science, a collection of fossils found during an expedition that began in the Cradle of Humankind in early 2008.

The fossils are of a young hominid male, estimated to have been between 11 and 13 years old, and an older female, believed to have been in her late twenties or early thirties.

Berger, who led the team that unearthed the impressive relics, believes the fossils are those of a new species, which they’ve named Australopithecus sediba. He avers in Science that the species may be the best candidate yet for the immediate ancestor of the Homo genus, to which humans, Homo sapiens, belong.

Two research articles and a news story on the discovery have been printed in this week’s edition, and an Australopithecus sediba cranium graces its cover. The research articles deal with the finds themselves and with the fossils’ age and geological setting.

The startling claims made by Berger and his team have prompted much debate; while they have been praised for making the find, they’ve been criticised for coming to hasty and non-credible conclusions. Science reports, “that last claim [that Australopithecus sediba is ancestral to Homo] is a big one, and few scientists are ready to believe it themselves just yet”.

The fossils were discovered in the Malapa cave, some 15km north-northeast of Sterkfontein, in the steep-sided valley of the spring-fed Grootvleispruit. They are estimated to be as old as 1.95-million years. The dating process that led the scientists to this conclusion was an intricate and painstaking one. They used a variety of methods, including Uranium-Lead, palaeomagnetic and faunal dating systems. Cosmogenic dating was used to interpret the landscape formation and to determine the depth of the cave at the time of deposition.

The academics argue that the fossils have a mixed bag of characteristics, with primitive features typical of australopithecines and some more advanced, human-like, qualities.

Australopithecus sediba has long, ape-like arms, short, powerful hands and long legs that the team believe would have allowed the species to take long strides and possibly run like a human. Berger says the brain size of the juvenile was between 420 and 450 cubic centimetres, small when compared to the human brain of about 1 200 to 1 600 cubic centimetres; but the shape of the brain seems to be more advanced than that of australopithecines. It’s estimated that both specimens were about 1.27m tall, although the child would certainly have grown taller. The female probably weighed about 33kg and the child about 27kg at the time of their deaths.

Berger and his team report in Science that “the skeletons were found close together and are directly associated with craniodental remains. Together they represent a new species of Australopithecus that is probably descended from Australopithecus africanus. Combined craniodental and postcranial evidence demonstrates that this new species shares more derived features with early Homo than any other australopith species and thus might help reveal the ancestor of that genus.”

The pre-eminent journal went on sale around the world today, its release coinciding with some of the fossils going on display at Maropeng. They were unveiled to the public yesterday; dignitaries including Deputy President Kgalema Motlanthe, Science and Technology Minister Naledi Pandor and Gauteng Premier Nomvula Mokonyane attended the event at the Maropeng Visitor Centre.

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