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South African fossil 'Little Foot' gets new origin date

Previously, scientists offered estimates for Little Foot's age ranging from 1.7 million to more than 4 million years.

By Brooks Hays

WEST LAFAYETTE, Ind., April 1 (UPI) -- The age of an ancient South African proto-human fossil called Little Foot has finally been agreed upon. New dating techniques place the Australopithecus specimen at 3.67 million years old, a contemporary of world-famous Lucy -- Ethiopia's fossilized female Australopithecus afarensis specimen.

Little Foot has yet to be classified, as its long-debated birthday confused scientists' understanding of the specimen's place on the evolutionary timeline. The newfound agreement might offer clarity on who exactly Little Foot is, and what it all means for the story of humanity.

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Upon its initial discovery, Little Foot was misidentified as an Old World monkey. But in 1994, paleoanthropologist Ronald J. Clarke recognized the specimen as a hominid. And follow-up digs revealed other body parts, eventually recovering Little Foot's near-complete skeleton.

Still, confusion reigned. Scientists offered estimates for Little Foot's age ranging from 1.7 million to more than 4 million years.

"Dating cave sediments and their fossils is difficult," Purdue researcher Darryl Granger, co-author of the new study on Little Foot, told the Christian Science Monitor. "We know so much about the timing of hominid evolution in East Africa because there are many datable volcanic ashes associated with the fossil sites. In places like South Africa there are no volcanic ashes to date."

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"The cave sediments themselves can also be very complicated, with sediment falling into multiple entrances, collapsing into lower sections, and overlapping each other," Granger added.

The confusion and disagreement mostly originated from the fact that Little Foot was found in a deposit with two differently aged sediments.

New analysis, however, confirms the younger sediment formed within cavities left when portions of the old rock dissolved. And a new technique called isochron burial dating confirmed that the old deposit had been buried all at once, roughly 3. 67 million years ago.

"They showed that the flowstone was formed inside cavities that were dissolved in the sediment after it was cemented," Granger explained, "and so the flowstone must be younger than the sediment around it."

Granger's new study, published this week in the journal Nature, sticks mostly to the science of sediment. But Little Foot's original discoverer, Clarke, says the new evidence proves he was right when he claimed the fossil an example of Australopithecus prometheus. Instead of coming after Lucy and her A. afarensis brethren, Little Foot was a contemporary of Lucy and another lineage called A. africanus -- proof that Australopithecus was a more diverse group than previously thought.

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"It demonstrates that the later hominids, for example, Australopithecus africanus and Paranthropus did not all have to have derived from Australopithecus afarensis," Clarke argued in a recent press release. "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."

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