by Barbara Casassus
Little Foot, the world’s most complete hominin fossil, dates back much further than the widely thought 2.2 million years, and should help scientists narrow down the identity of the first human ancestor, according to new research published today in the Journal of Human Evolution*. The findings were announced at simultaneous press conferences in Paris and Johannesburg.
The first analysis of sediments in the Silberberg Grotto at the Sterkfontein site in South Africa where Little Foot was discovered, shows the fossil Australopithecus is likely to be 3 million years old or more, according to Laurent Bruxelles, a geomorphologist at the archeology agency Inrap (Institut National de Recherches Archéologiques Péventives) in Paris. This would make Little Foot, officially named StW 573, a contemporary of the more scant Lucy, a fossil Australopithecus afarensis discovered in Ethiopia in 1974.
Ron Clarke, a retired professor of South Africa’s Witwatersrand University, discovered four foot bones of Little Foot in a box of animal fossils from the site in 1994, 16 years before the skeleton was fully unearthed. In contrast to other Australopithecines found in the area, which was classified by UNESCO as the “Cradle of Humankind” in 1999, Little Foot fell 20 metres to his or her death instead of being devoured by a predator, says Bruxelles, the paper’s lead author.
Attempts to date Little Foot’s 95%-plus complete skeleton have been dogged by controversy. Clarke first thought it was about 3 million years old, and belonged to the prometheus rather than the better known africanus species of the pre-human Australopithecus group. And several subsequent studies produced dating estimates ranging from 1.5 to 4 million years ago.
“Geologically, Little Foot could even be 4 million years old, but that will be up to the paleontologists to say,” Bruxelles says. The significance of the latest findings is that one of the two lineages “might have been a close ancestor of the first humans, while the other probably left no descendants”, he adds.
* Bruxelles, L., et al., Stratigraphic analysis of the Sterkfontein StW 573 Australopithecus skeleton and
implications for its age, Journal of Human Evolution (2014), http://dx.doi.org/10.1016/j.jhevol.2014.02.014