Some of the oldest fossils ever identified as belonging to Homo sapiens have been discovered to be even older than previously thought.
Known as the Omo I Remains, the fossils were found in the Omo Kibish Formation in southwest Ethiopia, in the East African Rift Valley between 1967 and 1974 – an area where one thinks humanity has evolved – and scientists have tried to date them all along. because.
Previous research suggested the fossils were less than 200,000 years old, but a new study confirmed they must have been older due to the discovery that a colossal volcanic eruption that took place 230,000 years ago flooded the sediments above the volcanic ash fossils.
An international team of scientists led by researchers at the University of Cambridge made the discovery by analyzing the “chemical fingerprint” in the layers of volcanic ash around bones.
To do this, they collected samples of pumice stone and then ground them to a submillimeter size.
“Each eruption has its own fingerprint – its own evolutionary history below the surface, which is determined by the route followed by the magma,” explained Dr Celine Vidal of the Cambridge Department of Geography.
“Once you crush the rock, you release the minerals inside, then you can date them and identify the chemical signature of the volcanic glass that holds the minerals together,” she added.
Their geochemical analysis linked the thick layer of volcanic ash to an eruption of the Shala volcano, more than 400 km (248 miles) away.
But they were not the age of Shala’s eruption, Dr Vidal said, so another team in Glasgow had to measure the age of the rocks.
“When I received the results and found out that the oldest Homo sapiens in the area was older than previously thought, I was really excited,” she added.
The oldest remains of what appear to be anatomically modern humans have been found in Morocco and are believed to be around 360,000 years old – but it’s unclear whether they actually belong to humans rather than a closely related species. related.
However, the Omo fossils possess “unmistakable modern human characteristics, such as a high, globular cranial vault and a chin,” explained co-author Dr Aurélien Mounier of the Musée de l’Homme in Paris.
“The new date estimate makes it de facto the undisputed oldest Homo sapiens in Africa,” added Dr Mounier.
“It is probably no coincidence that our earliest ancestors lived in such a geologically active Rift Valley – it collected precipitation in lakes, providing fresh water and attracting animals, and served as a natural migration corridor. ‘stretching for thousands of miles,’ said Professor Clive Oppenheimer, a vulcanologist at Cambridge.
“Volcanoes provided fantastic materials for making stone tools and every once in a while we had to develop our cognitive skills when large eruptions transformed the landscape,” the professor added.
“Our forensic approach provides for a new minimum age for Homo sapiens in East Africa, but the challenge remains to provide a ceiling, a maximum age, for their emergence, which is widely considered to have taken place in this region, ”explained co-author Professor Christine Lane, director of the Cambridge Tephra Laboratory which hosted most of the research.
“It is possible that new discoveries and new studies could push the age of our species even further back in time,” added Professor Lane.