Earliest Human Fossils From East Africa Dated To At Least 233,000 Years Ago

The Omo-Kibish Formation in Ethiopia, near where the fossils of the oldest Homo sapiens in Eastern Africa were discovered. Image credit: Sarah Collins

The early history of our species, an unusual great ape known as Homo sapiens, has to be rewritten once again. 

The remains of the oldest confirmed fossils of Homo sapiens in eastern Africa have been re-dated with the help of a colossal volcanic eruption that rocked Ethiopia hundreds of thousands of years ago. As per the new findings, the minimum age of the remains is now confined to approximately 233,000 years old, some 36,000 years older than previously thought. 

“The new date estimate, de facto, makes it the oldest unchallenged Homo sapiens in Africa,” co-author Dr Aurélien Mounier, from the Musée de l’Homme in Paris, said in a statement sent to IFLScience. The findings were published today in the journal Nature.

Researchers led by the University of Cambridge recently took another look at the layers of volcanic ash where the remains of Omo I, widely thought to be one of the earliest Homo sapien fossils ever found, was first discovered in the Omo Kibish Formation of southwestern Ethiopia in the 1960s (by a team from the Kenya National Museums led by trailblazing fossil hunter Richard Leakey, who died earlier this month). By dating the sediment layers, scientists can get an idea of when fossils are from, and as this technique improves, so does the accuracy.

The dating of early Homo sapiens remains can be sketchy and, occasionally, deeply contentious. One of the most sensational developments of recent years was the surprise discovery of 300,000-year-old H. sapien remains in Morocco. However, not everyone agrees these remains are truly Homo sapien as they have a notably different skull shape to modern humans. Nevertheless, the remains of Omo I are certainly considered the oldest Homo sapien remains in East Africa, a key location in the emergence of our species often dubbed the cradle of humankind, and possibly the oldest unchallenged Homo sapien remains in Africa.

“Unlike other Middle Pleistocene fossils which are thought to belong to the early stages of the Homo sapiens lineage, Omo I possesses unequivocal modern human characteristics, such as a tall and globular cranial vault and a chin,” Dr Mounier explained.

Based on the surrounding volcanic layer of ash, previous attempts at dating Omo I suggested the remains were around 197,000 years old. However, there’s long been uncertainty around this date since the ash is too fine-grained to accurately date using conventional methods. 

For the new study, the team took a slightly different approach that linked the surrounding volcanic deposits to a major explosive eruption of the Shala volcano in the Main Ethiopian Rift that occurred in the late Middle Pleistocene, when H. sapiens started emerging. Geochemical analysis revealed the remains were found deeper than a layer of ash that came from the eruption that occurred 230,000 years ago, meaning the remains were likely older. The team puts them at around 233,000 years old, pushing back a new minimum age for Homo sapiens in eastern Africa. 

The team strongly suspects that this is not the end of the story and it’s likely the oldest Homo sapiens in eastern Africa are yet to be discovered or fully understood. 

“Our forensic approach provides a new minimum age for Homo sapiens in eastern Africa, but the challenge still remains to provide a cap, a maximum age, for their emergence, which is widely believed to have taken place in this region,” said Professor Christine Lane, study co-author and head of the Cambridge Tephra Laboratory. “It’s possible that new finds and new studies may extend the age of our species even further back in time.”

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