The Omo I (Kibish) and Omo II (Kibish) remains are currently the oldest-known fossils of anatomically-modern humans (Homo sapiens). They were recovered by Richard Leakey in 1967 from the base of Member I of the Kibish Formation near the Omo River in south-western Ethiopia. Both Omo I and Omo II comprise a braincase and some postcranial material. Omo I fully modern in appearance; Omo II is slightly more primitive with a long, low cranium. However both are believed to be about the same age.
Originally believed to be around 130,000 years old, the Omo remains have recently been assigned a date of 195,000 +/- 5,000 years old, based on argon-40/argon-39 dating of volcanic tuffs (ash) found within Member I at levels. This makes them substantially older than the Herto remains discovered in 1997, previously thought to be the earliest-known fossil remains of modern humans. What is curious is that the 156,000 year old Herto remains, despite being around 40,000 years more recent than the Omo remains, retain more primitive features and were originally assigned their own subspecies, Homo sapiens idaltu.
Reference:
McDougall I, Brown FH & Fleagle JG (2005): Stratigraphic placement and
age of modern humans from Kibish, Ethiopia, Nature 734 Vol 433 17 Feb 2005.
© Christopher Seddon 2008
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