Fossils of earliest ancestors a million years older than previously thought: scientists

Fossils of our earliest ancestors in the “cradle of mankind” are a million years older than previously thought, according to new research.

The Sterkfontein Caves in Johannesburg, South Africa, reveal nearly 4 million years of evolution, scientists say, and contain more than a third of the world’s early hominid bones – crucial links in the chain to modern humans.

Australopithecus crania from Sterkfontein Cave in Africa
Fossils of our earliest ancestors in the “cradle of mankind” are a million years older than previously thought, according to new research. This image shows four different Australopithecus crania found in the Sterkfontein Caves in South Africa.
Jason Heaton, Ronald Clarke/Ditsong Museum of Natural History

The UNESCO World Heritage Site has now been identified as the “global center” of our ancient past.

It was home to “Little Foot”, whose almost complete 3.67 million year old skeleton was excavated there.

A famous pre-human skull dating back 2.3 million years — affectionately “Mrs. called Ples” – was also excavated.

They belonged to a primitive species known as Australopithecus. Hundreds more people were found inside the network of underground tunnels.

The dolomitic hills where the caves are located are 2.6 billion years old – more than half the age of the earth itself.

Most of the Australopithecus fossils were unearthed in an ancient cave infill called “Member 4”. Its age has been a matter of debate for more than half a century, with estimates ranging from 2 million years younger than our genus Homo to as far back as about 3 million years.

The study refutes the long-held notion that the South African Australopithecus is a younger offshoot of the East African Australopithecus afarensis.

Co-author Professor Dominic Stratford from Wits University, Johannesburg, said: “The new age ranges from 3.4 to 3.6 million years for member 4 – indicating that the Sterkfontein hominins were contemporaneous with other early Australopithecus species , such as Australopithecus afarensisin East Africa.”

Darryl Granger of Purdue University
Purdue University’s Darryl Granger developed the technology that updated the age of an Australopithecus found in Sterkfontein Cave. New data pushes its age back by more than a million years to 3.67 million years.
Photo by Purdue University/Lena Kovalenko

The study in the journal PNAS is based on the radioactive decay of the rare isotopes aluminum-26 and beryllium-10 in the mineral quartz.

Lead author Professor Darryl Granger of Purdue University in Indiana said: “These radioactive isotopes, known as cosmogenic nuclides, are produced by high-energy cosmic ray reactions near the Earth’s surface, and their radioactive decay dates to when the rocks were buried in the Earth became cave when they fell into the entrance along with the fossils.”

Previous methods relied on analysis of travertine deposits, but observations showed these to be younger than the cave fill, underestimating the age of the fossils.

Stratford said: “This reassessment of the age of the Sterkfontein Member 4 Australopithecus fossils has important implications for the role of South Africa in the evolutionary phase of hominins.

“Younger hominins, including Paranthropus and our genus Homo, emerged about 2.8 to 2 million years ago.

“Based on previously proposed dates, the South African Australopithecus species were too young to be their ancestors, so it was considered more likely that Homo and Paranthropus evolved in East Africa.”

Hominid Australopithecus afarensis
A sculpted representation of the hominid Australopithecus afarensis is on display as part of an exhibit displaying the 3.2-million-year-old fossilized remains of “Lucy,” the most complete specimen of the species, at the Houston Museum of Natural Science, May 28, 2007 in Houston, Texas.
Dave Einsel/Getty Images

But Australopithecus existed in Sterkfontein almost a million years before Paranthropus and Homo appeared, giving them more time to evolve.

It puts the hominins at the center of the story of early human evolution, the researchers explained.

Stratford said: “This important new dating work pushes the age of some of the most interesting fossils in human evolutionary research and one of South Africa’s most famous fossils, Mrs. Ples, back a million years to a time when in East Africa we find other iconic early hominins like Lucy. “

Most Australopithecus species were small, typically 3 ft 11 in to 4 ft 7 in tall. Males were larger than females – like his descendants today.

The most famous Australopithecus was smaller – the 3.5 foot “Lucy” discovered in Ethiopia in 1974. she is a Australopithecus afarensis and lived 3.85 to 2.95 million years ago.

Granger said: “The re-dating of the Australopithecus-bearing fillings in the Sterkfontein Caves will no doubt reignite the debate over the various features of Australopithecus at Sterkfontein – and whether there might have been South African ancestors of later hominins.”

“Sterkfontein has more Australopithecus fossils than anywhere else in the world. But it’s hard to get a good date for her.

“People have looked at animal fossils found near them and compared the ages of cave features like river rocks and gotten a range of different dates.

“Our data resolves these controversies. They show that these fossils are old – much older than we originally thought.”

The results were published in Proceedings of the National Academy of Sciences.

This story was provided to Newsweek by Zenger News. Fossils of earliest ancestors a million years older than previously thought: scientists

Rick Schindler

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