Scientists dated one of the oldest-known hominid skeletons, "Little Foot," and found he walked the Earth about 3.67 million years ago.
The new findings suggest Little Foot was an older relative of "Lucy," the famous Australopithecus skeleton dated at 3.2 million years old that was found in Ethiopia, Purdue University reported. Little Foot was first discovered about two decades ago in a South African cave; it is believed to represent Australopithecus Prometheus lineage.
"It demonstrates that the later hominids, for example, Australopithecus africanus and Paranthropus did not all have to have derived from Australopithecus afarensis," said Ronald Clarke, a professor in the Evolutionary Studies Institute at the University of the Witwatersrand, who discovered the skeleton. "We have only a small number of sites and we tend to base our evolutionary scenarios on the few fossils we have from those sites. This new date is a reminder that there could well have been many species of Australopithecus extending over a much wider area of Africa."
The team of scientists dated the mysterious bones using a radioisotopic dating technique created by Darryl Granger, a professor of earth, atmospheric and planetary sciences at Purdue. The method, dubbed isochron burial dating, measures levels of isotopes (specifically aluminum-26 and beryllium-10) found in rocks surrounding a fossil. A graph of the isotope ratios, called an isochron, is then created for the rock samples to demonstrate whether or not they have been compromised and are good candidates for dating.
"If we had only one sample and that rock happened to have been buried, then re-exposed and buried again, the date would be off because the amount of radioisotopes would have increased during its second exposure," Granger said. "With this method we can tell if that has happened or if the sample has remained undisturbed since burial with the fossil. It is expensive and a lot of work to take and run multiple samples, but I think this is the future of burial dating because of the confidence one can have in the results."
The findings were published in a recent edition of the journal Nature.
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