Early human ancestors one million years older than earlier thought

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.

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 2.6m years old.

But there were no signs of Homo habilis at the depth of the cave where Mrs Ples was found.

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 analyse the sediment near where they were found.

The previous dates underestimated the age of the fossils because they measured calcite flowstone mineral deposits, which were younger than the rest of that cave section, the study said.

For the latest study, the researchers used a technique called cosmogenic nuclide dating, which looked at levels of rare isotopes created when rocks containing quartz were hit by high-speed particles that arrived from outer space.

The researchers found that Mrs Ples and other fossils near her were between 3.4 and 3.7m years old.

It could also possibly alter our understanding of our ancestral history.

But the new research shows that the South African Australopithecus had almost a million years to evolve into our Homo ancestor.

Or they could have worked on it together.