Omo Kibish (Ethiopia) - Oldest Known Example of Early Modern Humans

Omo Kibish is the name of an archaeological site in Ethiopia, where was found the earliest examples of our own hominin species, about 195,000 years old. Omo is one of several sites found within the ancient rock formation called Kibish, itself along the Lower Omo River at the base of the Nkalabong Range in southern Ethiopia.

Two hundred thousand years ago, the habitat of the lower Omo River basin was similar to what it is today, although moister and less arid away from the river. Vegetation was dense and a regular supply of water created a mix of grassland and woodland vegetation.

Omo I Skeleton

Omo Kibish I, or simply Omo I, is the partial skeleton found from Kamoya’s Hominid Site (KHS), named after the Kenyan archaeologist who discovered Omo I, Kamoya Kimeu. The human fossils recovered in the 1960's and in the early 21st century include a skull, several pieces from the upper limbs and shoulder bones, several bones of the right hand, the lower end of the right leg, a piece of the left pelvis, fragments of both lower legs and the right foot, and some rib and vertebrae fragments.

The body mass for the hominin has been estimated at approximately 70 kilograms (150 pounds), and although it is not certain, most evidence indicates Omo was female. The hominin stood somewhere between 162-182 centimeters (64-72 inches) tall--the leg bones are not sufficiently intact enough to give a closer estimate. The bones suggest Omo was a young adult at the time of her death. Omo is currently classified as anatomically modern human.

Artifacts with Omo I

Stone and bone artifacts were found in association with Omo I. They included a variety of vertebrate fossils, dominated by birds and bovids. Nearly 300 pieces of flaked stone were found in the vicinity, predominantly fine-grained crypto-crystalline silicate rocks, such as jasper, chalcedony, and chert. The most common artifacts are debris (44%) and flakes and flake fragments (43%).

A total of 24 cores was found; half the cores are Levallois cores. Primary stone tool making methods used at KHS produced Levallois flakes, blades, core-trimming elements, and pseudo-Levallois points. There are 20 retouched artifacts, including an ovate handaxe, two basalt hammerstones, sidescrapers, and backed knives. Over the area a total of 27 artifact refits have been found, suggesting a potential slope wash or north-trending sediment slump before the site's burial or some purposeful stone knapping/tool discard behaviors.

Excavation History

Excavations in the Kibish formation were first conducted by the International Palaeontological Research Expedition to the Omo Valley in the 1960's led by Richard Leakey. They found several ancient anatomically modern human remains, one of them the Omo Kibish skeleton.

In the early 21st century, a new international team of researchers returned to Omo and found additional bone fragments, including a femur fragment which conjoined with a piece collected in 1967. This team also conducted Argon isotope dating and modern geological studies that identified the age of the Omo I fossils as 195,000 +/- 5,000 years old. The Lower Valley of the Omo was inscribed to the World Heritage List in 1980.

Dating Omo

The earliest dates on the Omo I skeleton were quite controversial--they were uranium-series age estimates on Etheria freshwater mollusk shells that provided a date of 130,000 years ago, which in the 1960's was deemed too early for Homo sapiens. Serious questions arose in the latter half of the 20th century about the reliability of any dates on mollusks; but in the early 21st century Argon dates on the strata in which Omo lay returned ages between 172,000 and 195,000, with the most likely date nearer 195,000 years ago. A possibility then arose that Omo I had been an intrusive burial into an older layer.

Omo I was finally direct-dated by laser ablation elemental Uranium, Thorium, and Uranium-series isotope analysis (Aubert et al. 2012), and that date confirms its age as 195,000+/- 5000. In addition, a correlation of the makeup of the KHS volcanic tuff to the Kulkuletti Tuff in the Ethiopian Rift Valley indicates the skeleton is likely aged 183,000 or older: even that is 20,000 years older than the next oldest AMH representative in the Herto formation also in Ethiopia (154,000-160,000).

Sources

This definition is part of the Thoughtco Guide to the Middle Paleolithic.

• _{Assefa Z, Yirga S, and Reed KE. 2008. The large-mammal fauna from the Kibish Formation. Journal of Human Evolution 55(3):501-512.}
• _{Aubert M, Pike AWG, Stringer C, Bartsiokas A, Kinsley L, Eggins S, Day M, and Grün R. 2012. Confirmation of a late middle Pleistocene age for the Omo Kibish 1 cranium by direct uranium-series dating. Journal of Human Evolution 63(5):704-710.}
• _{Brown FH, McDougall I, and Fleagle JG. 2012. Correlation of the KHS Tuff of the Kibish Formation to volcanic ash layers at other sites, and the age of early Homo sapiens (Omo I and Omo II). Journal of Human Evolution 63(4):577-585.}
• _{de la Torre I. 2004. Omo Revisited: Evaluating the Technological Skills of Pliocene Hominids. Current Anthropology 45(4):439-466.}
• _{McDougall I, Brown FH, and Fleagle JG. 2005. Stratigraphic placement and age of modern humans from Kibish, Ethiopia. Nature 433:733-736.}
• _{McDougall I, Brown FH, and Fleagle JG. 2008. Sapropels and the age of hominins Omo I and II, Kibish, Ethiopia. Journal of Human Evolution 55(3):409-420.}
• _{Pearson OM, Royer DF, Grine FE, and Fleagle JG. 2008. A description of the Omo I postcranial skeleton, including newly discovered fossils. Journal of Human Evolution 55(3):421-437.}
• _{Rightmire GP. 2008. Homo in the Middle Pleistocene: Hypodigms, variation, and species recognition. Evolutionary Anthropology 17(1):8-21.}
• _{Shea JJ. 2008. The Middle Stone Age archaeology of the Lower Omo Valley Kibish Formation: excavations, lithic assemblages, and inferred patterns of early Homo sapiens behavior. Journal of Human Evolution 55(3):448-485.}
• _{Sisk ML, and Shea JJ. 2008. Intrasite spatial variation of the Omo Kibish Middle Stone Age assemblages: Artifact refitting and distribution patterns. Journal of Human Evolution 55(3):486-500.}