Fossils of early human ancestors from the Sterkfontein cave in South Africa were recently revealed to be more than a million years older than previously dated.
The Sterkfontein cave is the “most prolific single source of Australopithecus fossils,” according to a study published on Monday.
This discovery is consequential to anthropologists’ understanding of human evolution and its chronology.
The Australopithecus was a hominin — a member of the Hominini zoological tribe, which consists of species of primates that were related to or the ancestors of Homo sapiens, modern-day humans. The name Australopithecus means “southern ape,” as these primates “bore a combination of humanlike and apelike traits.”
Sterkfontein is a complex, deep cave system that was able to preserve these ancestral fossils for millions of years. The highest density of Australopithecus fossils was primarily found in “Member 4,” a part of the cave discovered during excavations.
Researchers originally dated the fossils between 2 and 2.6 million years old. The original dating process used “calcite flowstone deposits discovered in the cave fill.”
However, using the cosmogenic nuclide dating technique, researchers now estimate the fossils to be between 3.4 and 3.6 million years old. Cosmogenic nuclide dating allows scientists to use the decay of radioactive isotopes inside rocks found near fossils to help determine how long a surface has been exposed or how long an object has been buried.
Darryl Granger, a researcher from Purdue University and a lead author in the study, told EurekAlert, “The date of the radioactive decay is similar to that of the fossils because that is when they both fell at the cave entrance.”
According to research published in PNAS and directed by Dominic Stratford, “with the new age range, the fossils in Sterkfontein Caves belong to contemporaries of other Australopithecus.”
The theory of hominin evolution is likely to experience a shake-up if the new dating technology is employed to date other fossils. The young hominins, such as Paranthropus and Homosapiens, were dated between 2 and 2.8 million years under the earlier dating system.
According to the earlier dates, the Australopithecus in South Africa was too young to become their ancestor. This chronology becomes questionable, especially after the new dating pushed the South African fossil back a million years.
In the news release, Granger stated that their findings would “undoubtedly re-ignite the debate over the diverse characteristics of Australopithecus at Sterkfontein and whether there could have been South African ancestors to later hominins.”
