'Little Foot' Fossil Pre-Dates the Famed 'Lucy' at 3.7 Million Years

A skeleton by the name of "Little Foot" may just be the oldest hominid skeleton ever discovered. Dated at 3.67 million years old, it actually pre-dates the famous "Lucy."

Little Foot is a rare and nearly complete skeleton of Australopithecus and was first discovered 21 years ago in a cave at Sterkfontein in central South Africa. Australopithecus is thought to be an evolutionary ancestor of humans that lived between two million and four million years ago.

That said, the fossil is actually Australopithecus prometheus, which is a species that's different from its contemporary Australopithecus afarensis, and with more similarities to the Paranthropus lineage. Lucy, in contrast, is an example of Australopithecus afarensis.

"It demonstrates that the later hominids, for example, Australopithecus africanus and Paranthropus did not all have to have derived from Autralopithecus afarensis," said Ronald Clarke, one of the researchers, in a news 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."

Little Foot was named for four small foot bones found in a box of animal fossils that led to the skeleton's discovery. Its age has long been debated, and estimates have ranged from two to four million years old with an estimate of three million years. Now, though, researchers have used a new technique called isochron burial dating, which uses radioisotopes within several rock samples surrounding a fossil to date when the rock and the fossil were first buried underground. This revealed that the fossil was more around 3.67 million years old.

Currently, the researchers hope to apply the new technique to more fossils at Sterfontein and elsewhere. This could mean a new way to date artifacts and give scientists a more accurate timeline of human evolution.

The findings are published in the journal Nature.

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