Homo Sapiens: our species appeared more than 230,000 years ago
The age of the oldest fossils known to represent our species, Homo sapiens, in East Africa has always been debated. As part of a study based on the analysis of a massive volcanic eruption in Ethiopia, researchers were able to specify the dating of these bones. According to these works, they are much older than previously thought.
The first modern humans
Difficult to trace the rise of our own species as the course of human evolution will have been bushy. Even today, we still do not know precisely when and where the first Homo sapiens appeared. However, an archaeological site found in southwestern Ethiopia, in the Omo Kibish formation, might be one of the most credible starting points. It is indeed there that the paleoanthropologist Richard Leakey came across in the 1960s the first examples of fossils offering unquestionably modern human anatomy .
Over the past few decades, scientists have attempted to date these remains (known as Omo I) as accurately as possible using chemical fingerprints of volcanic ash layers found above and below the sediments in which the fossils have been found. Nevertheless, these estimates have always been discussed and disputed .
An international team, led by the University of Cambridge, recently reassessed the age of these remains. If we previously thought these fossils were less than 200,000 years old, this research shows that they are actually older than a colossal volcanic eruption that wiped out the region thousands of years ago.
“ The generally accepted age of the Omo fossils is less than 200,000 years, but there has been a lot of uncertainty around this date ,” points out Dr Céline Vidal, from the Cambridge Department of Geography. “ The fossils were found in sequence, under a thick layer of volcanic ash that no one had been able to date with radiometric techniques, because the ash is too fine-grained . »
Over 230,000 years old
In the work, published in the journal Nature , the researchers collected samples of pumice from volcanic deposits and then ground them down to sub-millimeter size.
“ Each eruption has its own fingerprint, its own evolutionary history below the surface that is determined by the path followed by the magma ,” continues the researcher. “ 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 . »
The team therefore carried out a new geochemical analysis to finally link the imprint of the site's thick layer of volcanic ash with an eruption of the Shala volcano over 400 kilometers away. The researchers then dated the pumice samples from the volcano to around 230,000 years old . Since these Homo Sapiens fossils were found deeper than this layer of ash, they must be over 230,000 years old .
If we are to believe this work, the appearance of our species could therefore have taken place during the Late Middle Pleistocene. On the other hand, the researchers point out that while this study proposes a new minimum age for the appearance of Homo sapiens in East Africa, it remains possible that new discoveries and new studies could push back the age of our species still further. more .
Source: websites