Paleontology: the australopithecines of South Africa are getting old



A million years in sight! International cooperation has raised the age ofAustralopithecus africanus, a species of Australopithecus that lived in southern Africa. Until then, sediment analyzes from the Sterkfontein excavation site in South Africa considered this distant cousin to have been present for a period of 2.1 to 2.6 million years. The new estimate pushes that range back to between 3.4 and 3.7 million years.

Blame it on the stalagmites, or rather the “flat” stalagmites. “The floors of these caves look like mille-feuilles”describes Laurent Bruxelles, geoarchaeologist from the University of Toulouse Jean-Jaurès and co-author of the study published in Pnas Monday, June 27. The first estimates had been made by dating limestone deposited by runoff in a sedimentary layer where fossils had been found. The technique is classic. But, in this specific case, the dating was distorted by runoff: the rocks analyzed infiltrated well after in the geological layer that contains the fossils.

For the new measurement, it is therefore quartz that was passed through the mill, in particular rare forms of certain chemical elements – aluminum and beryllium. “As long as the rocks are on the surface, these isotopes are going to be produced due to cosmic radiationexplains Laurent Brussels. Then, when the rock is covered or buried in a cave, these isotopes will gradually disappear, with a known rate of decay. » From the remaining isotopes, it is thus possible to know when the rock was buried and therefore when the bones fossilized.

A parallel coexistence of Australopithecines

This new dating would confirm that the South African Australopithecus lived at the same time as its East African neighbor Australopithecus afarensis. And therefore cannot be its descendant. A real revolution, which would have thrilled the paleoanthropologist Yves Coppens, who died last week and co-discoverer in 1974 of Lucy, the best known of the Australopithecus skeletons afarensis.

“This update shows a synchronous evolution, which invites us to reflect on the appearance of Australopithecines across the entire African continent, leaving the debate on the different cradles of humanity”, believes Laurent Brussels. For several decades, paleoanthropologists have abandoned the idea of ​​a single human lineage, to speak instead of a ” bush “several species cohabiting and evolving in parallel.

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