Early human ancestors one million years older than thought

The fossils of our earliest ancestors found in South Africa are a million years older than previously thought, meaning they walked the Earth around the same time as their East African relatives like the famous "Lucy," according to new research.

The Sterkfontein caves at the Cradle of Humankind world heritage site southwest of Johannesburg have yielded more Australopithecus fossils than any other site in the world.

Among them was "Mrs Ples," the most complete skull of an Australopithecus africanus found in South Africa in 1947.

Based on previous measurements, Mrs Ples and other fossils found at a similar depth of the cave were estimated to be between 2.1 and 2.6 million years old.

But "chronologically that didn't fit," said French scientist Laurent Bruxelles, one of the authors of a study published on June 27 in the PNAS science journal.

"It was bizarre to see some Australopithecus lasting for such a long time," the geologist told AFP.

Around 2.2 million years ago the Homo habilis, the earliest species of the Homo genus that includes Homo sapiens, was already roaming the region. But there were no signs of Homo habilis at the depth of the cave where Mrs Ples was found.

Also casting doubt on Mrs Ples's age was recent research showing that the almost-complete skeleton of an Australopithecus known as "Little Foot" was 3.67 million years old.

Such a big gap in ages between Mrs Ples and Little Foot seemed unlikely given they were separated by so few sedimentary layers.

Because the fossils are too old and fragile to test, scientists analyze the sediment near where they were found.

The previous dates underestimated the age of the fossils because they measured calcite flowstone mineral deposits, which...