The remains of Omo Kibish 1 were unearthed in 1967 by the team of the famous Kenyan paleoanthropologist, Richard Leakey, recently deceased, in the lower Omo valley (southern Ethiopia), a prehistoric site world famous for its numerous fossils. hominids.
Although badly damaged, the body bones and skull fragments exhibited a surprisingly modern morphology, making Omo 1 the oldest fossil inHomo sapiens known from East Africa. And even from all over the African continent, before being dethroned by the discovery in 2017 of remains ofHomo sapiens primitive in Morocco, dating back 300,000 years.
At Omo 1, very difficult to date in the absence of dentition, approximately 130,000 years have been given. A study published in 2005 then pushed back time to 195,000 years, based on analysis of the surrounding sediments – a much more reliable chronological marker in this case than direct dating on bones.
there was still a lot of uncertainty about his age, explains to AFP Céline Vidal, lead author of a new study published Wednesday in the journal Nature.
This volcanologist from the University of Cambridge therefore left to re-excavate the Omo Kibish sedimentary basin, fed by the Kibish river. Located in the Great Rift, the area underwent violent volcanic eruptions between 300,000 and 60,000 years BC.
Colossal volcanic eruption
The ashes, projected for hundreds of kilometers around, have over time become inserted between the sediments deposited by the Kibish River. Which, lowering its level, gradually revealed the geological past, making Omo Kibish a true
library, according to Céline Vidal.
It is indeed thanks to the examination of these different layers that scientists were able to assess the age of human remains – by a dating method called
argon-argon, rare gases contained in rocks.
In the early 2000s, the volcanic ash below the sediment containing the fossils was estimated to be around 195,000 years old. This meant that Omo 1 was at most that age –
he could only be younger than the ash level below him, decrypts the volcanologist.
To be more precise, it would have been necessary to examine the thick layer of ash located above, necessarily deposited after.
Alas, it was almost impossible as the ashes were fine, almost like flour, she emphasizes.
Thanks to more sophisticated methods, his team was able to examine the layer of ash covering the remains, and connect these volcanic deposits to a colossal explosion of the Shala volcano that occurred 233,000 years ago.
These analyzes have made it possible to date the Omo fossils under this layer, at about000 – with a margin of error of 22000years “,” text “:” 233000 – with a margin of error of 22000 years “}}”>233,000 – with a margin of error of 22,000 years, details the study.
And this is a minimum age, that is, these human remains could be even older.
Better time alignment
It’s a huge leap in time!, rejoices Aurélien Mounier, paleoanthropologist at the Musée de l’Homme, one of the authors. Most importantly, the timescale aligns more consistently with the latest models of human evolution.
000years that modern man has diverged from other human lineages “,” text “:” We are approaching the date put forward by genetics, according to which it is around 300,000 years that modern man has diverged from other human lineages “}}”>We are getting closer to the date put forward by genetics, according to which it was around 300,000 years ago that modern man diverged from other human lineages., develops this CNRS researcher.
Omo 1 also approaches the age of the Moroccan fossils of Jebel Irhoud – 300,000 years as well. But it is the Ethiopian skull which, in his eyes, now constitutes Sapiens“,” text “:” the most solid proof of the oldest presence of Sapiens “}} ‘>the strongest evidence of the oldest presence of Sapiens throughout its African cradle.
Because, when comparing the cranial vaults of the two specimens, Omo 1
is the only one to fully possess the morphological characteristics of modern man. The more elongated shape of Jebel Irhoud’s skull presupposes a more primitive form of our species.