The dating of the oldest undisputed fossil ofHomo sapiens was estimated at 200,000 years ago. The radiometric dating of a volcanic layer in Ethiopia makes it possible to reassess the age of our species to several thousand years earlier.
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How old is the species Homo sapiens ? L’emergence of the species in Africa took place during the Pleistocene Late and the Omo Kibish Formation in southwestern Ethiopia contains the remains of Omo I which had so far been dated to less than 200,000 years ago. In study published in the journal Nature, a team of researchers is now reassessing the age of Omo I.
Older than 230,000 years
The Omo Kibish formation is located in the valley of the east african rift, which is an area that has known and still knows strong volcanic activity. However, the authors explain that each volcanic eruption has a kind ofdigital print, which makes its identity recognizable and unique. The remains of Omo I lay under a thick layer of volcanic ash whose dating was uncertain until then because the ash was too fine for a absolute dating be carried out.
However, the authors of the study used pumice stones from this same layer of ash in order to carry out a radiometric dating. They were thus able to determine that the age of the layer of ash located above the remains of Omo I was produced by the eruption of the Shala volcano, located 400 kilometers from the site, 230,000 years ago. The authors also indicate that fossils older ones are sometimes attributed to early stages of the lineage H. sapiens but that Omo I constitutes to date the oldest indisputable fossil ofHomo sapiens due to anatomical features such as a high, globular cranial vault, as well as a chin.
Homo sapiens is 35,000 years old
From paleontologists Australians and Americans have reviewed the dating of human fossils discovered along the Omo River in southern Ethiopia.
Article from France Sciences, published on February 28, 2005
Both skulls, baptized Omo I and II, were unearthed in 1967 and dated according to an initial estimate of about 130,000 years by analysis of the rate of thorium and D’uranium oysters found in the sediment (a controversial date because it was thought that modern man could not be more than 100,000 years old).
But the new methods available have led Francis Brown, of the University of Utah, John Fleagle, of Stony Brook University (New York), and Ian MacDougall, of the Australian National University, to another conclusion: the two fossils, contemporary despite morphological differences, would date back nearly 195,000 years (within 5,000 years).
The researchers focused in particular on the decay rate ofargon feldspar crystals from sediments just below the fossils and ashes taken from well above (about 50 meters); the former indicated an age of 196,000 years and the latter a lower limit of 104,000 years.
The speed from sedimentation of the Omo River being at the time very important, the age of the remains would therefore be closer to 196,000 years. Until then, the oldest human fossils were considered to be those discovered at Herto, also in Ethiopia, and estimated to be between 154,000 and 160,000 years old. This work confirms the recent paleogenetic analyzes situating the origin of theHomo sapiens between -150,000 and -200,000 years ago.
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