The Sterkfontein Caves at the Cradle of Humankind World Heritage Site southwest of Johannesburg have yielded more Australopithecus fossils than anywhere else in the world. Among them was “Mrs Ples”, the most complete skull of an Australopithecus africanus found in South Africa in 1947. Based on previous measurements, Ms. Ples and other fossils found at a similar depth in the cave were estimated to be between 2.1 and 2.6 million years old. But “chronologically it did not fit,” said French scientist Laurent Bruxelles, one of the authors of a study published Monday in the journal PNAS. “It was strange to see an Australopithecus last for so long,” the geologist told AFP. About 2.2 million years ago Homo habilis – the oldest species of the genus Homo including Homo sapiens – was already roaming the area. But there were no signs of Homo habilis at the bottom of the cave where Mrs. Plees was found. He also questioned the age of Ms Ples, a recent study which showed that the almost complete skeleton of an Australopithecus known as “Little Foot” was 3.67 million years old. Such a large age gap between Mrs. Ples and Little Foot seemed unlikely as they were separated by so few sedimentary layers. Because the fossils are too old and fragile to test, scientists are analyzing the sediment near where it was found. Earlier dates underestimated the age of the fossils because they measured the deposits of calcite ores, which were younger than the rest of the cave, the study said. For the latest study, the researchers used a technique called cosmogenic nucleid dating, which looked at the levels of rare isotopes created when quartz-containing rocks were struck by high-velocity particles coming from space. “Their radioactive decay dates back to when the rocks were buried in the cave when they fell at the entrance along with the fossils,” said study lead author Daryl Granger of Purdue University in the United States. The researchers found that Ms. Ples and other fossils near her were between 3.4 and 3.7 million years old. This means that members of Australopithecus africanus such as Mrs. Ples were “contemporaries” of East African Australopithecus afarensis, including 3.2-million-year-old Lucy found in Ethiopia, said Dominic Stratford, director of cave research and one of the authors. study. . It could also possibly change our understanding of the history of our ancestors. The South African ape had previously been considered “too young” to be the ancestor of the genus Homo, Stratford said. This meant that Lucy’s home in East Africa was considered to be the most likely place where the Homo genus evolved. But new research shows that the South African ape had almost a million years to evolve into our ancestor Homo. Or they could have worked it out together. “Over a period of millions of years, just 4,000 kilometers (2,500 miles) away, these species have had plenty of time to travel, to reproduce among themselves; so we can largely imagine a common evolution across Africa,” he said. Brussels. The research showed that the history of humans was “more complex than linear evolution,” he added. Our family tree is actually “more like a bush, to use the words of our late friend Yves Coppens,” said Bruxelles, referring to the French paleontologist believed to have discovered Lucy. Kopens died last week. “He had long understood the pan-African nature of evolution,” Brussels said.
