Modern humans appeared in eastern Africa at least 38,000 years earlier than scientists previously believed. This conclusion was drawn from the effects of a huge volcanic eruption used to date the earliest undisputed date sane man fossils.
The remains, called Omo I, were discovered at the Omo Kibish site near the Ethiopian Omo River in the 1960s. Previous estimates put human fossils back to about 195,000 years ago. Now, new research published January 12 in the journal temper nature, tells a different story – the remains are older than a massive volcanic eruption that rocked the area about 233,000 years ago.
The new estimate places the fossils more firmly among the oldest sane man The remains were ever discovered in Africa, only second to 300,000-year-old samples found at the Jebel Irhoud site in Morocco in 2017. However, the Jebel Irhud skulls differ enough in their physical characteristics from those of modern humans, which makes some Scholars challenge its classification. as sane man. This means that the new discovery represents the oldest undisputed dating of modern humans in Africa.
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“Unlike other East ice Age Fossils, which are believed to belong to the early stages of sane man pedigree, Omo I possesses unmistakable modern human characteristics, such as a long and spherical cranial vault and chin,” study co-author Aurélien Mounier, a human paleontologist at the Musée de l’Homme in Paris, He said in a statement, referring to the spherical vault of the skull as the space in which the brain sits within the skull. “Appreciation of the new history, de facto, makes it the undisputed oldest sane man In Africa.”
The remains were found in the East African Rift Valley, an active continental rift zone where the African tectonic plate works to split into two smaller plates, the Somali plate and the Nubian plate. Although the fossils were discovered more than 50 years ago, scientists have found it difficult to give the age of Omo I still definitive. The fossils lacked nearby stone artifacts or animals that could be dated, and the ash they buried beneath was too grainy for radiometric measurement – a method that quantifies the amounts of certain radioactive isotopes (versions of an element with a different number of neutrons in the nucleus) at known decay rates.
To get around these problems, the researchers collected samples of pumice from the Shala volcano more than 248 miles (400 kilometers) away, grinding them until they were less than a millimeter in size. By performing a chemical analysis on the pumice found in the volcano and comparing it to the ash layer in the sediments above where the fossils were found, the researchers were able to confirm that they both shared the same chemical composition, and thus came from the same eruption. It turns out that the pumice and ash bed samples are about 233,000 years old – which means the Omo I fossils below the ash are at least the same age or older.
“First, I found that there was a geochemical match, but we did not have the age of the Shalla eruption,” lead author Céline Vidal, a volcanologist at the University of Cambridge, said in the statement. “I immediately sent samples from the Shala volcano to our colleagues in Glasgow so they could measure the age of the rocks. When I received the results and discovered that the oldest Homo sapiens from the area was older than previously assumed, I was really excited.”
It’s no coincidence that some of humanity’s early ancestors lived in a geologically active rift valley, Cliff Oppenheimer, a volcanologist at the University of Cambridge, said in the statement. Tectonic activity has created lakes that collect rainwater, not only providing fresh water but also attracting animals to hunt; The 4,350-mile-wide (7,000 km) Great Rift Valley – of which the East African Rift Valley is just a small part – served as a massive migration corridor for humans and animals that stretched from Lebanon in the north all the way to Mozambique in the south.
Although a minimum age for Omo I specimens was found, researchers still need to find an upper bound on the age of both these fossils and the broader emergence of Homo sapiens in East Africa. They plan to do this by correlating more buried ash with more volcanic eruptions around the area, giving them a more stable geologic timeline of the sedimentary layers around which fossils are deposited in the area.
“Our forensic approach provides a new lower age limit for Homo sapiens in East Africa, but the challenge remains in providing an upper limit for their appearance, which is widely believed to have occurred in this region,” said Christine Lane, a chronogeologist at the University of Cambridge, in Statement. “It is possible that new discoveries and new studies may extend the lifespan of our species back in time.”
Originally published on Live Science.
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