The results of a new fossil dating technique developed by Darryl Granger, a professor of earth, atmospheric, and planetary sciences at Purdue University, have shown that several fossil remains of early human ancestors were discovered near the site of the Sterkfontein Caves, which might be even more,mucholder than previously assumed.
A group of scientists used space particles to investigate bones in the Sterkfontein Caves, part of a major fossil site in northern South Africa known as the "Cradle of Humankind."
The age of some of these fossils was cut back by more than a million years as a result of their research. Dinkinesh, also known as Lucy, is the world's most famous Australopithecus fossil.
Paleoanthropologists and other specialists have studied Sterkfontein and other cave sites near the Cradle of Humankind in order to uncover human and environmental evolution over the previous four million years.
Professor Robert Burns Young of Buxton Limeworks in South Africa's Taung area sent two crates of fossils from Professor Raymond Dart of the University of the Witwatersrand in Johannesburg in 1924.
Dart immediately recognized the significance of a small fossil skill that arose from a creature that was neither fully ape nor man. It represented one of our ancestors - anextincthominclosely related to humans - which he dubbed Australopithecus africanus, which means "southern ape of Africa."
Thousands of fossils, including hominid fossils, have been discovered at the "Cradle of Humankind," a UNESCO World Heritage Site that includes a number of fossil-bearing cave deposits, including at the Sterkfontein Caves in 1936. There have been discoveries of the first adult Australopithecus, an ancient hominin, and a thenearly complete skeleton known as Little Foot.
The fossils are considerably older than we assumed.
Granger and a team of researchers, including researchers from the University of Johannesburg, South Africa, and the University of Toulouse Jean Jauresin France, have discovered that not only Little Foot, but all of the Australopithecus-bearing cave sediments date back to about 3.4 to 3.7 million years, rather than 2-2.5 million years as previously thought.
Dinkinesh, who hails from Ethiopia, is 3.2 million years old, and her species, Australopithecus africanus, is thought to have arrived at some 3.9 million years earlier.
"Sterkfontein has more Australopithecus fossils than anywhere else in the world," Granger said in a statement. "People have looked at the animal fossils near them and compared the ages of cave features like flowstones and gotten a variety of different dates." What our data does is resolve these issues. It shows that these fossils are much older than we originally assumed."
Radioactive nuclides in the rocks were measured using accelerator mass spectrometry.
The Great Rift Valley volcanoes in East Africa deposit layers of ash. Scientists then use these layers to determine the age of a fossil. In the South African caves, researchers typically employ other animal fossils found around the bones to determine their age.
Granger and his colleagues examine the concrete-like matrix that embeds the fossil.
Granger and his colleagues studied accelerator mass spectrometry to measure radioactive nuclides in the rocks as well as geologic mapping and a better understanding of how cave sediments accumulate to determine the age of the Australopithecus-bearing sediments at Sterkfontein.
The dating method provides "reliable" results.
Moreover, the team created detailed maps of the cave deposits and revealed how animal fossils of different ages might have been intermixed during excavations in the 1930s and 1940s, which, in all likelihood, would have sparked decades of debate about the previous ages.
"I hope that this will convince people that this proven dating technique is reliable," Granger said. "Using this technique, we can more precisely place ancient humans and their descendants in the correct seasons, in Africa, and elsewhere in the world."
The age of fossils has an influence on scientists' understanding of the living landscape of that time. It may answer several complex and pressing questions, including the evolution of humans in a given location, their participation in the ecosystem, and who their closest relatives are and were.
Dating the fossils at Sterkfontein back to their proper age is a significant step towards unraveling the whole picture.
The majority of Australopithecusfossils found at Member 4 have been recovered from subterranean deposits [T. C. Partridgeet al.,Science300, 607612 (2015); R. J. Clarke, K. Kuman,J. Hum. Evol.134, 102634 (2018)]; these results support an earlier isochron burial date of ca. 2.1 to 2.6 My for the whole Australopithecusassemblage at Sterkfontein.