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2015-08-22 13:32:25   •   ID: 1247

Olorgesailie : Paleo-Landscapes in your mind

Figure 1
This is a 25 cm long lanceolate handaxe from Olorgesailie, a geological formation in East Africa containing a group of ESA (990-500 k.a.) and MSA archaeological sites. It is on the floor of the Eastern Rift Valley in southern Kenya, 64 km southwest of Nairobi.

Olorgesailie is most noted for the numerous Acheulian artifacts, defining one of the largest single assemblages of handaxes in the world. The Olorgesailie basin contains sediments divided into two main geological units, the oldest of which is the Olorgesailie Formation, approximately 80m thick. The basin area is 300 km2, and an abundance of archaeological remains is exposed near the northern base of Mt. Olorgesailie.

Paleolithic artifacts at Olorgesailie were first discovered by JW Gregory in 1919 but excavations under the direction of Mary and Louis Leakey did not start until 1943. Work continued there until 1947. Glynn Isaac took up the excavation in the 1960ies. This eminent scientist was one of the founders of modern landscape archeology. 

At Olorgesailie, he made any attempt to characterize landscapes over geographically intermediate scales to a focus on the palaeoenvironmental and geochronological analysis of valley-floor sediments and palaeosols in the immediate vicinity of the site.

He also published on the effect of social networks, gathering, meat eating and other factors on human evolution, and proposed a series of models to examine how groups of humans in the ESA would have engaged in acquiring the necessities of life, and interacting with each other.

Isaac’s models focused on a “home base” and the importance of sexual division of labor on hominid social organization. Since the 1980ies, research was continued by the Smithsonian Institution in conjunction with the National Museums of Kenya. This work established a secure geological and archeological chronology for the Olorgesailie formation.

Current research uses a GIS-based advanced  landscape archaeological approach for investigation and excavation, providing a means to place their site finds within a much broader context so that they can be understood and interpreted more meaningfully within the geologic and climatological environment within which they existed. Extended excavations follow defined layers across long distances up to 1 km to target where to excavate for fossils and artifacts.

Olorgesailie is best known for an abundance of Acheulean handaxes, associated with several episodes of animal butchering dated to ca 950 k.a. ago. Recent investigations have recovered fossil hominin remains at the site, including a partial cranium KNM-OL 45500 (H. erectus), in the same stratigraphic level with two Acheulean handaxes and several flakes, and adjacent to dense deposits of handaxes.

The Acheulian of East Africa during 1 My and 600 k.a. seems to be more refined than the Acheulian between 1,75 My and 1 My. Important sites are the Kariandusi archaeological site and Kilombe (ca 900 k.a.) in Kenya, the classic site of Olduvai  Bed IV in Tanzania, Olorgesailie (Kenya) , Daka, Buia, Gombore II (Ethiopia) and Gesher Benot Ya’aqov (GBY) in Israel.

During “Middle Acheulian” times there are first attempts for the soft hammer technique  and several prepared core techniques were invented (for example the Victoria west technique).

New excavations at Olorgesailie since 2001 have revealed that Acheulean occupations were followed by a long sequence of Middle Stone Age occupations without handaxes, beginning well before 315 k. a and ending before 64 k.a.

Levallois technology was present already in the later Acheulean horizons of Members 11 and 13 of the Olorgesailie formation (between 625 and 550 k.a), which further may substantiate the claims for a “long Levallois chronology” in Africa, first suggested from the Kathu Pan 1 site in S-Africa, well before its appearance in the Middle East or Europe.

Archeologists also found evidence that obsidian during the MSA was obtained from at least 95 km away.

The excavators conclude that obsidian over such distances was most probably traded over social networks. Again, comparable to other very old MSA sites, red and black pigments were used, maybe for symbolic reasons.

Suggested Reading: (very informative for any reader!)

Melson, W.G., Potts, R., 2002. Origin of reddened and melted zones in Pleistocene sediments of the Olorgesailie basin, southern Kenya Rift. Journal of Archaeological Science 29, 307-316.

Owen, R.B., Potts, R., et al., 2008. Diatomaceous sediments and environmental change in the Pleistocene Olorgesailie Formation, southern Kenya Rift Valley. Palaeogeography, Palaeoclimatology, Palaeoecology 269(1-2), 17-37.

Owen, R.B., Renaut, R.W,, et al., 2009. Wetland sedimentation and associated diatoms in the Pleistocene Olorgesailie Basin, southern Kenya Rift Valley. Sedimentary Geology 222, 124-137.

Potts, R., 1989. Olorgesailie: new excavations and findings in Early and Middle Pleistocene contexts, southern Kenya rift valley. Journal of Human Evolution 18, 477-484.

Potts, R., 1994. Variables versus models of early Pleistocene hominid land use. Journal of Human Evolution 27, 7-24.

Potts, R., 1998. Variability Selection in Hominid Evolution. Evolutionary Anthropology 7(3), 81-96.

Potts, R., Behrensmeyer, A.K., et al., 1999. Paleolandscape variation and Early Pleistocene hominid activities: Members 1 and 7, Olorgesailie Formation, Kenya. Journal of Human Evolution 37, 747- 788.

Potts, R., Behrensmeyer, A.K., et al., 2004. Small Mid-Pleistocene hominin associated with East African Acheulean technology. Science 305, 75-78.

Sikes, N.E., Potts, R., Behrensmeyer, A.K., 1999. Early Pleistocene habitat in Member 1 Olorgesailie based on paleosol stable isotopes. Journal of Human Evolution 37, 721-746.

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