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Human fossils from Africa are 1 million years older than previously thought

A new study, published on Monday (27) in the scientific journal Proceedings of the National Academy of Sciences, revealed that fossils of Australopithecus found in South Africa’s Sterkfontein caves are a year older than previously thought — making them older than the famous fossil of Lucy (aka Dinkinesh) from Ethiopia.

Lucy was found in the 1970s and represents the species Australopithecus afarensis, that lived 3.2 million years ago.

Now, using a new technique to date sediments from the Sterkfontein caves, researchers at the University of the Witwatersrand in South Africa have found that the new fossils of the genus Australopithecus they are between 3.4 million and 3.6 million years old—and not between two and 2.6 million years old as dated earlier.

The caves are located about 50 kilometers northwest of the South African city Johannesburg and are considered the Cradle of Humankind.

The caves, included in this network called “Member 4”, have revealed details about human and environmental evolution spanning some four million years ago.

Radiation dating

Since research began at the site in 1936 with the discovery of the first adult hominid of the genus Australopithecus, made by Robert Broom, the region has become famous for the hundreds of fossils from excavations of ancient cave fills, including iconic specimens such as the skull known as Mrs. Ples and the Little Foot skeleton.

The dating of the fossils pointed, until then, to two or even three million years.

However, as Professor Dominic Stratford, director of cave research and one of the authors of the paper, explained in a statement, “the new ages range from 3.4 to 3.6 million years for the Member 4 network, indicating that the Sterkfontein hominids were contemporaries of other early species of Australopithecusas Australopithecus afarensis (Lucy’s skull, for example) in East Africa.

Previously earlier dating of the Member 4 region was based on dating of flowstone calcite deposits (other carbonate minerals) found within the cave fill.

Now, to arrive at the analysis that determined a new age, the research team used the technique of radioactive decay of the rare isotopes aluminum-26 and beryllium-10 in the mineral quartz.

Darryl Granger, a professor at Purdue University in the United States and lead author of the paper, said that “these radioactive isotopes, known as cosmogenic nuclides, are produced by high-energy cosmic ray reactions near the surface of the ground.”

With this radioactive decay, it is possible to date when the rocks were buried in the cave at the time they fell into the entrance along with the fossils, he continued.

A new look at paleoanthropology

According to the researchers, reassessing the age of fossils from Australopithecus has important implications for the role of South Africa in the stage of hominid evolution.

“Younger hominids, including Paranthropus and our genus Homo, appear between about 2.8 and two million years ago. Based on previously suggested dates, the species of Australopithecus from South Africa were too young to be their ancestors, so it is considered more likely that Homo and Paranthropus evolved in East Africa,” said Stratford.

The discovery shows that Australopithecus existed in Sterkfontein almost a million years before the appearance of the paranthropus It’s from Homoproviding more time for them to evolve “in the Cradle of Humanity”, and placing hominids from this location at the center of the story of early human evolution.

“One of South Africa’s most iconic fossils, Mrs Ples, goes back a million years to a time when, in East Africa, we find other iconic fossils of early hominids like Lucy,” Stratford said.

For Granger the dating of the fillings of Australopithecus in the caves of Sterkfontein will undoubtedly reignite the debate about the diverse characteristics of the genus in the region. In addition to raising the discussion about “whether there could have been South African ancestors of later hominids”, he asked.

Source: CNN Brasil

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