The Omo bones were discovered between 1967 and 1974 at the Omo Kibish sites near the Omo River, in Omo National Park in south-western Ethiopia. First, anatomically modern humans are found in the Omo Valley region Africa and are dated at 195,000 years old.
The bones were recovered by a scientific team from the Kenya National Museums. The remains from Kamoya's Hominid Site (KHS) were called Omo I and those from Paul I. Abell's Hominid Site (PHS) Omo II. The bones include two partial skulls, four jaws, a legbone, around two hundred teeth, and several other parts.
Omo I and Omo II differ in morphological traits. The Omo II fossils indicate more archaic traits. In 2008, new bone remains were discovered from Awoke's Hominid Site (AHS). The AHS fossil's tibia and fibula were unearthed from Member I, the same layer from which the other Omo remains derive. About 30 years after the original finds, a detailed stratigraphic analysis of the area surrounding the fossils was done. The Member I layer was argon-dated to 195,000 years ago, and the (higher layer) Member III was dated to 105,000 years ago. Numerous recent lithic records verify the tool technology from Members I and III to the Middle Stone Age.
The lower layer, Member I, is considerably older than the 160,000-year-old Herto remains designated as Homo sapiens idaltu. The rainy conditions at that time—which are known from isotopic ages on the Kibish Formation corresponding to the ages of Mediterranean sapropels—suggest the increased flow of the Nile River and, therefore, increased flow of the Omo River. But the climates changed such that after 185,000 years ago conditions were so dry as to not allow speleothems to grow in the caverns in the Levantine land-bridge region, the vital inroad for migration to Eurasia.
Parts of the fossils are the earliest to have been classified by Leakey as Homo sapiens. In 2004, the geological layers around the fossils were dated, with the age of the "Kibish hominids" estimated at 195,000 years ago.
