A new study has revealed that old skeleton "little foot" is 3.67 million years old, which places it as an older relative of "Lucy."
Little Foot is a rare, nearly complete skeleton of Australopithecus first discovered 21 years ago in a cave at Sterkfontein, in central South Africa. The new date placed Little Foot as an older relative of Lucy, a famous Australopithecus skeleton dated at 3.2 million years old that was found in Ethiopia. It was thought that Australopithecus was an evolutionary ancestor to humans that lived between 2 million and 4 million years ago.
Stone tools found at a different level of the Sterkfontein cave also were dated at 2.18 million years old, making them among the oldest known stone tools in South Africa.
A team of scientists from Purdue University; the University of the Witwatersrand, in South Africa; the University of New Brunswick, in Canada; and the University of Toulouse, in France, performed the research.
Ronald Clarke, a professor in the Evolutionary Studies Institute at the University of the Witwatersrand who discovered the Little Foot skeleton, said the fossil represents Australopithecus prometheus, a species very different from its contemporary, Australopithecus afarensis, and with more similarities to the Paranthropus lineage.
Like Lucy, Little Foot was female. The species was much bigger and taller than Lucy's, with gorilla-like facial features. Little Foot also stood fully upright and was very strong with powerful hands for climbing, according to paleoanthropologists Ron Clarke and Kathy Kuman of the University of the Witwatersrand in Johannesburg.
There had not been a consensus on the age of the Little Foot skeleton, named for four small foot bones found in a box of animal fossils that led to the skeleton's discovery.
Previous dates ranged from 2 million to 4 million years old, with an estimate of 3 million years old preferred by paleontologists familiar with the site, said Darryl Granger, a professor of earth, atmospheric and planetary sciences at Purdue, who in collaboration with Ryan Gibbon, a former postdoctoral researcher, led the team and performed the dating.
The dating relied on a radioisotopic dating technique pioneered by Granger coupled with a powerful detector originally intended to analyze solar wind samples from NASA's Genesis mission. The result was a relatively small margin of error of 160,000 years for Little Foot and 210,000 years for the stone tools.
This time the team used the PRIME Lab's powerful accelerator mass spectrometer and a new detector, called a gas-filled magnet detector, to measure the radioisotopes.
The tools from the site had earlier been determined to be Oldowan, a simple flaked stone tool technology considered the earliest stone tool industry in prehistory.
The new Sterkfontein date for the Oldowan artifacts shows that this industry is consistently present in South Africa by 2 million years ago, a much earlier age for tool-bearing hominids than previously anticipated in this part of Africa, Kathleen Kuman, a professor in earlier and middle stone age archaeology in the School of Geography, Archaeology and Environmentla Studies at the University of the Witwatersrand in Johannesburg, South Africa said.
The study is published in the journal Nature.
