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Stone Age Site in Kenya


Gelada Baboon (Theropithecus gelada) at the Colchester Zoo

The gelada baboon (Theropithecus gelada) is the only surviving member of the theropithecus species of baboon.


Olorgesailie is the name of a geological formation in southern Kenya, East Africa where a group of Lower Paleolithic archaeological sites have been discovered. Olorgesailie is best known for an abundance of Acheulean handaxes, associated with several episodes of animal butchering.

Originally thought to be about a half a million years old, the site has recently been redated using potassium-argon methods to between 900,000-990,000 years ago.

Several butchering localities have been discovered at Olorgesailie. They are marked by concentrations of bone fragments of extinct animals and hand axes and other stone tools deposited over about 100,000 years on the shifting shoreline of a now-extinct lake. Animals in evidence at Olorgesailie include extinct forms of hippo, elephant, zebra, giraffe, and baboon (theropithecus).

Recent investigations have recovered fossil hominin remains at the site, including a partial cranium KNM-OL 45500, in the same stratigraphic level with two Acheulean handaxes and several flakes, and adjacent to dense deposits of handaxes. This cranium represents an adult Homo erectus, although somewhat smaller than most others of that species.

Olorgesailie and Archaeology

Discovered and tested by Louis and Mary Leakey in the 1940s, Olorgesailie was excavated by Glynn Isaac as his dissertation research during the 1960s. Research resumed Olorgesailie in the early 1980s, led by Richard Potts of the Smithsonian Institution.

Common Misspellings: Olorgesaillie, Olorgesaile


This glossary entry is a part of the About.com Guide to the Lower Paleolithic, and part of the Dictionary of Archaeology.

See Rick Potts' page on Olorgesailie for more information about the 2004 expedition.

New Fossil Ape May Shake Human Family Tree, 2004 news story by Nick Wadhams in the National Geographic.

Isaac, Glynn L. 1977 Olorgesailie: Archeological Studies of a Middle Pleistocene Lake Basin in Kenya. Chicago: University of Chicago Press.

Isaac, Glynn L. 1967 Towards the interpretation of occupation debris: Some experiments and observations. Kroeber Anthropological Society Papers 37:31-57.

Kleindienst, Maxine R. 1961 Variability within the Late Acheulean assemblage in Eastern Africa. South African Archaeological Bulletin 16:35-52.

Potts, Richard, Anna K. Behrensmeyer, and Peter Ditchfield 1999 Paleolandscape variation and Early Pleistocene hominid activities: Members 1 and 7, Olorgesailie Formation, Kenya. Journal of Human Evolution 37(5):747-788.

Potts, Richard, et al. 2004 Small Mid-Pleistocene Hominin Associated with East African Acheulean Technology. Science 305(5680):75-78.

Shipman, Pat, Wendy Bosler, and Karen L. Davis 1981 Butchering of giant geladas at an Acheulian site. Current Anthropology 22(3):257-267.

Sikes, Nancy E., Richard Potts, and A. K. Behrensmeyer 1999 Early Pleistocene habitat in Member 1 Olorgesailie based on paleosol stable isotopes. Journal of Human Evolution 37(5):721-746.

This glossary entry is part of the Dictionary of Archaeology.

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