Ancient Hominid Fossil Dated to 3 Million Years
After more than a decade of excavation work, the nearly complete skeleton of the Australopithecus fossil called Little Foot, so named for the diminutive size of the bones, has been convincingly dated to 3 million years old, making it the oldest nearly complete Australopithecus skeleton ever found.
In 1997 Ron Clarke, Stephen Motsumi and Nkwane Molefe of the University of the Witwatersrand discovered an almost complete Australopithecus skeleton with skull embedded in hard, calcified sediment in an underground chamber of the Sterkfontein caves of Gauteng, South Africa. The caves have been world famous since 1936 for producing large numbers of fossils of the hominid Australopithecus, which some scientists claim is an extinct potential ancestor of humans.
The left hand and forearm of Little Foot, partially embedded in matrix. Image: University of the Witwatersrand
Soon after the initial find, a magnetic study suggested the bones were 3.3 million years old. However, a 2006 study published in Science started an anthropological controversy when it suggested Little Foot’s bones were 2.2 million years old, based on the age of calcium-rich rocks surrounding the fossils. Two other later studies dated the skeleton to 2.35 and 2.58 million years ago, using a technique known as uranium-lead decay dating.
However, in a paper published in the Journal of Human Evolution, Professor Ron Clarke from the University of the Witwatersrand and his colleagues refute previous dating claims that suggested Little Foot is younger.
The team of South African and French scientists have stated that a partial collapse of the fossil-bearing stones into a lower cavity of the cave led to a confusing geological position and confounded the estimates of Little Foot’s age. After the collapse, a calcium carbonate rock, known as flowstone, formed in the spaces around the fossils. This led to a mix-up millions of years later when scientists dated the younger rock and believed it had formed at nearly the same time as the fossils.
The dated flowstones filled voids formed by ancient erosion and collapse,” said a statement from the University of the Witwatersrand. “The skeleton is therefore older, probably considerably older, than the dated flowstones.
Barely a metre tall, Little Foot fell into a 20-metre hole and died, possibly while running from a predator. The body rolled down a steep slope and came to land with its left arm stretched out over its head. Over the years, the remains, naturally mummified, were buried under more than 10 metres of sediment and rock.
According to the researchers, the finding bolsters the status of South Africa’s Sterkfontein cave complex as part of the “Cradle of Humankind”, a UN-recognised World Heritage Site.
Featured image: Little Foot found in the Sterkfontein caves of Gauteng, South Africa. Image: Laurent Bruxelles/INRAP