Early human fossils found in cave are a million years older than expected

M4 montage: Four different Australopithecus crania that were found in the Sterkfontein caves, South Africa. The Sterkfontein cave fill containing this and other Australopithecus fossils was dated to 3.4 to 3.6 million years ago, far older than previously thought. The new date overturns the long-held concept that South African Australopithecus is a younger offshoot of East African Australopithecus afarensis.

(CNN)Fossils of early human ancestors from a South African cave are 3.4 million to 3.6 million years old -- making them a million years older than previously suspected and shaking up the way researchers understand human origins and evolution.

This new date makes the Sterkfontein Cave fossils older than the famed Lucy fossil (also known as Dinkinesh) from Ethiopia. Found in 1979, Lucy represented the species Australopithecus afarensis and lived 3.2 million years ago.
The freshly dated fossils also belong to the genus Australopithecus, an ancient hominin that was initially thought to live 2 million to 2.6 million years ago. Researchers used a new technique to date the sediments of the Sterkfontein Caves, which are part of the Cradle of Humankind UNESCO World Heritage Site, about 30 miles (50 kilometers) northwest of Johannesburg.
    The caves included in this network have revealed details about human and environmental evolution that span about 4 million years.
      The site is home to a treasure trove of fossils that help tell the story of human evolution -- a story that seems to shift with each discovery.
      A new study detailing the findings was published Monday in the Proceedings of the National Academy of Sciences.
      The importance of the Sterkfontein Caves came to light in 1936, when the discovery of the first adult Australopithecus fossil was made by paleontologist Dr. Robert Broom.
        Hundreds of Australopithecus fossils have been found there since, including the famous Little Foot, who lived 3.67 million years ago. Today, she represents the most complete Australopithecus skeleton and is helping researchers to learn more about our chimpanzee-like ancestors.
        "Sterkfontein has more Australopithecus fossils than anywhere else in the world," said lead study author Darryl Granger, professor of Earth, atmospheric and planetary sciences in Purdue University's College of Science, in a statement.
        "But it's hard to get a good date on them. People have looked at the animal fossils found near them and compared the ages of cave features like flowstones and gotten a range of different dates. What our data does is resolve these controversies. It shows that these fossils are old -- much older than we originally thought."

        A new look at ancient ancestors

        The researchers determined that all of the cave sediments including Australopithecus fossils date from 3.4 million to 3.6 million years old, which places them toward the beginning of the Australopithecus era, rather than the end of it. They now predate other hominins at nearby sites by over a million years.