Fossil study reveals human ancestors 1 million years older than previously thought

Latest research sheds new light on age of predecessors found in South Africa

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The fossils of our early ancestors found in South Africa are a million years older than previously thought.

A study of hominin remains from the Australopithecus genus found at the Sterkfontein caves north of Johannesburg — including the famed Mrs Ples fossil — puts their ages at between 3.4 million and 3.6 million years, Johannesburg’s University of the Witwatersrand said in statement on Monday.

Mrs Ples and other fossils found at a similar depth of the cave were previously estimated to be between 2.1 million and 2.6 million years old. But the latest study found that they are actually older than the Lucy fossil found in Ethiopia in 1979, which is 3.2 million years old.

The find puts South Africa back in contention as the site where humankind may have originated.

The Sterkfontein caves at the Cradle of Humankind world heritage site near 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, which was found in South Africa in 1947.

“This important new dating work pushes the age of some of the most interesting fossils in human evolution research, and one of South Africa’s most iconic fossils, Mrs Ples, back a million years to a time when, in East Africa, we find other iconic early hominins like Lucy,” said Dominic Stratford, director of research at the caves and one of the authors of a paper published in the Proceedings of the National Academy of Sciences journal.

Research at Sterkfontein began in 1936 when paleontologist Robert Broom discovered the first adult hominin fossil. Since then hundreds of similar finds have been made at the site, many originally thought to have lived 2 million to 3 million years ago.

Those finds, and an earlier one in 1924, came before of the discoveries in East Africa, which began in 1959.

The new age estimation was made using the radioactive decay of aluminium and beryllium isotopes in the rocks buried at the same time as the fossils, according to the researchers.

Earlier estimates were based on calcite flowstone deposits that are now believed to be younger than the rest of the rocks found in the cave. East African fossils were easier to date because of the presence of volcanic material.

“South Africa was largely ignored because it was so difficult to date the fossils. They were largely dismissed as not being relevant to the story of human evolution,” said Ronald Clarke, a professor at the University of Witwatersrand and an author of the paper.

“It’s a big deal, this does confirm that these primitive ancestors were all over Africa.”

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Updated: June 29, 2022, 11:48 AM