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Early human ancestors one million years older than thought

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“Little Foot” one of several known fossils found in the Sterkfontein Caves in the Cradle of Humankind in South Africa.

The fossils of our earliest ancestors found in South Africa are a million years older than previously thought, meaning they orbited the Earth around the same time as their East African relatives like the famous “Lucy,” according to new research. .

The Sterkfontein Caves at the Cradle of Humankind World Heritage Site southwest of Johannesburg have yielded more Australopithecus fossils than any other site 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, Mrs. Ples and other fossils found at a similar depth of the cave were estimated to be between 2.1 and 2.6 million years old.

But “chronologically that was not correct,” says French scientist Laurent Bruxelles, one of the authors of a study published Monday in the PNAS scientific magazine.

“It was bizarre to see an Australopithecus survive for so long,” the geologist told AFP.

About 2.2 million years ago, Homo habilis – the earliest species of the Homo genus that includes Homo sapiens – already roamed the region.

But there were no signs of Homo habilis at the depth of the cave where Mrs. Ples was found.


Also questionable about Mrs. Ples’s age was recent research showing that the nearly complete skeleton of an Australopithecus known as “Little Foot” was 3.67 million years old.

Such a great gulf at times between Mrs Ples and Little Foot seemed unlikely, since they were separated from each other by so few sedimentary layers.

Because the fossils are too old and fragile to test, scientists are analyzing the sediment near where they were found.

The previous data underestimated the age of the fossils because they measured calcite flowstone mineral deposits, which were younger than the rest of that cavern section, the study said.

The Sterkfontein Caves southwest of Johannesburg have yielded more Australopithecus fossils than any other site in the world

The Sterkfontein Caves southwest of Johannesburg have yielded more Australopithecus fossils than any other site in the world.

For the latest study, the researchers used a technique called cosmogenic nuclide dating, which looked at levels of rare isotopes created when rocks containing quartz were hit by high-speed particles coming from space.

“Their radioactive decay dates back to when the rocks were buried in the cave as they fell into the entrance along with the fossils,” said the study’s lead author, Darryl Granger of Purdue University in the US.

The researchers found that Mrs. Ples and other fossils with her were between 3.4 and 3.7 million years old.

This means members of Australopithecus africanus like Ms. Ples were “contemporaries” of the Australopithecus afarensis in East Africa, including the 3.2-million-year-old Lucy found in Ethiopia, said Dominic Stratford, the caves research director and one of the researchers. authors of the study. †

Our ‘more like a bush’ family tree

It could also potentially change our understanding of our ancestral history.

The South African Australopithecus was previously considered “too young” to be the ancestor of the genus Homo, Stratford said. That meant Lucy’s home in East Africa was the most likely place where the genus Homo evolved.

But the new research shows that South African Australopithecus had nearly a million years to evolve into our Homo ancestor.

Or they could have worked on it together.

“Over the span of millions of years, just 4,000 kilometers (2,500 miles) away, these species had ample time to travel, to breed with each other … so we can largely envision a common evolution across Africa,” he said. Brussels .

The research showed that the history of hominins was “more complex than linear evolution,” he added.

Our family tree is, in fact, “more like a shrub, to use the words of our late friend Yves Coppens,” Bruxelles said, referring to the French paleontologist who helped discover Lucy. Coppens passed away last week.

“He had long understood the pan-African nature of evolution,” Bruxelles said.

Fossils in the ‘cradle of humanity’ may be more than a million years older than previously thought

More information:
Cosmogenic nuclide dating in Sterkfontein, South Africa, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2123516119

© 2022 AFP

Quote: Early human ancestors a million years older than thought (2022, July 2) retrieved July 2, 2022 from https://phys.org/news/2022-06-early-human-ancestors-million-years.html

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