The nearly complete skeleton of the Australopithecus prometheus named Little Foot discovered in the Sterkfontein caves in South Africa is the oldest complete Australopithecus ever found, say anthropologists led by Dr Laurent Bruxelles of the French National Institute for Preventive Archaeological Research.
The Sterkfontein caves of Gauteng, South Africa have been world famous since 1936 for producing large numbers of Australopithecus fossils.
For about 60 years, these fossils consisted only of partial skulls and jaws, isolated teeth and fragments of limb bones. These were obtained by blasting or drilling and breaking of the calcified ancient cave infill or by pick and shovel excavation of the softer decalcified infills.
Questions arose about the age of these fossils, of how they came to be in the caves, and also of how a complete skeleton would appear.
In 1997, anthropologists discovered an almost complete Australopithecus skeleton with skull embedded in hard, calcified sediment in an underground chamber of the caves. This was the first time that such an excavation of an Australopithecus has taken place in an ancient calcified deposit.
During the course of the excavations, it became clear that the skeleton had been subjected to ancient disturbance and breakage through partial collapse into a lower cavity and that calcareous flowstone had subsequently filled voids formed around the displaced bones.
Some other researchers dated the flowstones and claimed that such dates represent the age of the skeleton. This has created a false impression that the skeleton is much younger than it actually is.
Now, Dr Bruxelles and his colleagues shown that the dated flowstones filled voids formed by ancient erosion and collapse and that the skeleton is therefore older, probably considerably older, than the dated flowstones. The results appear in the Journal of Human Evolution.
Little Foot is probably around 3 million years old, and not the 2.2 million years that has been wrongly claimed by other researchers.
The skeleton has been entirely excavated from the cave and the skull, arms, legs, pelvis and other bones have been largely cleaned of encasing rock.
The anthropologists concluded that the fossils belong to Australopithecus prometheus, a species named by Professor Raymond Dart in 1948 on fragmentary ape-man fossils from Makapansgat in what is now Limpopo Province. Thus at Sterkfontein, there existed two species of ape-man, Australopithecus africanus and Australopithecus prometheus.
Bruxelles L. et al. Stratigraphic analysis of the Sterkfontein StW 573 Australopithecus skeleton and implications for its age. Journal of Human Evolution, published online March 14, 2014