Older than Lucy herself, called the ‘grandmother of humanity’ (whose remains are between 3.5 and 3.2 million years old).
The oldest australopithecus in the world has had competition. The Sterkfontein Caves in Johannesburg, South Africa contain more than a third of the world’s earliest hominin fossils, crucial links in the evolutionary chain of modern humans. Now new research has revealed that fossils of early human ancestors in the so-called ‘Cradle of Humankind’ could be more than a million years older than previously thought.
An international team of researchers has established a new clear time frame for all fossils from the Sterkfontein caves (UNESCO World Heritage Site known as the ‘Cradle of Humankind’), critical for understanding the early origins of our evolution , concluding that many of the remains are contemporaneous with ‘Little Foot’ , the nearly complete skeleton of an australopithecus child from 3.7 million years ago. This would therefore mean that they would be even larger than ‘Lucy’, the world’s most famous autralopithecus fossil.
New method of dating fossils
Scientists developed a new dating method that revealed that Australopithecines lived in the Sterkfontein cave nearly a million years before the appearance of the genera Homo and Paranthropus.
They used accelerator mass spectrometry to measure radioactive nuclides in the rocks, as well as geological mapping and a deep understanding of how cave sediments accumulate to determine the age of the Australopithecus -bearing sediments at Sterkfontein. Cosmogenic nuclides are extremely rare isotopes produced by cosmic rays, high-energy particles that constantly bombard the earth. Cosmic rays can cause nuclear reactions within rocks at the ground surface, which can generate new radioactive isotopes in mineral crystals. These radioactive isotopes can be used to date the sediments in the cave.
“The new ages range from 3.4 to 3.6 million years for Member 4, indicating that the Sterkfontein hominins were contemporaries of other early Australopithecus species, such as Australopithecus afarensis, in East Africa,” commented Dominic Stratford, director of cave research, in his study published in the journal Proceedings of the National Academy of Sciences.
Era ‘Australopithecus’
This new information would indicate that these fossils belong to the beginning of the Australopithecus era.
“This important new dating work pushes back a million years the age of some of the most exciting fossils in human evolution research, and one of the most iconic fossils from South Africa, Mrs. Ples , to a time when which, in East Africa, we find other iconic fossils. early hominids like Lucy,” Stratford said.
The study also dismisses the idea that Australopithecus from South Africa is a younger branch of East African Australopithecus Afarensis .
“The youngest hominins, including Paranthropus and our genus Homo, appeared between 2.8 and 2 million years ago,” Stratford explained. “Based on the dates suggested above, the South African Australopithecus species were too young to be their ancestors, so it has been considered more likely that Homo and Paranthropus evolved in East Africa.”
The importance of this discovery
The age of the fossils is important because it influences scientists’ understanding of the living landscape of the time. The study places Australopithecus ‘front and center’ in the story of early human evolution, experts say.
“The new dating of the Australopithecus fills in the Sterkfontein caves will undoubtedly revive the debate about the various characteristics of the Australopithecus at Sterkfontein, and whether there might be South African ancestors of later hominins,” they conclude.
We continue to unravel the evolutionary puzzle of how and where humans evolved.
Referencia: Darryl E. Granger, Dominic Stratford, Laurent Bruxelles, Ryan J. Gibbon, Ronald J. Clarke, Kathleen Kuman. Cosmogenic nuclide dating of Australopithecus at Sterkfontein, South Africa. Proceedings of the National Academy of Sciences, 2022; 119 (27) DOI: 10.1073/pnas.2123516119
