Cape Town - New research has shown that the Australopithecus fossil deposit in the famous Sterkfontein caves is now estimated to be a million years older than researchers had first thought.
Most of the Australopithecus fossils at Sterkfontein were excavated through the ancient cave infill called “Member 4”, which houses the richest deposit of Australopithecus fossils in the world.
For many years, research at the cave had led many to believe that the age of “Member 4” at Sterkfontein remained contested.
They believed that the age of Australopithecus dated back to 2 millions years ago, making it younger than the first appearance of our own genus, Homo, which dates back 3 million years.
Dominic Stratfrod, an associate professor at Wits University, director of research at Sterkfontein and one of the authors of the research paper, said they had re-evaluated the age of Austraolpitehcus in “Member 4” and in the Jacovec cavern to show more fossils deeper 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, like Australopithecus afarensis, in East Africa,” Stratford said.
The new dates show that Australopithecus existed at Sterkfontein almost a million years prior to the appearance of Paranthropus and Homo, providing more time for them to evolve here, in the Cradle of Humankind.
“This important new dating work pushes (back) the age of some of the most interesting fossils in human evolution research,” he said.
Stratford said the re-assessment of the Sterkfontein “Member 4” Australopithecus fossils has important implications for the role of South Africa on the hominin evolution stage – the pattern of adaptive change in response to changing ecological and selective conditions.
Professor Darryl Granger of Purdue University in the US and lead author on the paper, said the new ages are from radioactive decay in rare isotopes found in aluminium and beryllium quartz
“These radioactive isotopes, known as cosmogenic nuclides, are produced by high-energy cosmic ray reactions near the ground surface, and their radioactive decay dates when the rocks were buried in the cave when they fell in the entrance together with the fossils,” he said.
This new discovery puts the hominins at the forefront of human historical evolution and allows for greater depth to finding out more about it.
