Olorgesailie

Landscape near Olorgesailie

Olorgesailie is a geological formation in East Africa containing a group of Lower Paleolithic archaeological sites.^[1] It is on the floor of the Eastern Rift Valley in southern Kenya, 40 miles (64 km) southwest of Nairobi along the road to Lake Magadi. Olorgesailie is noted for the large number of Acheulean hand axes, associated with animal butchering, discovered there.^[1] According to the National Museums of Kenya, the finds are internationally significant for archaeology, paleontology, and geology.^[2]

History

Hand axes

The artifacts were first discovered by the British geologist John Walter Gregory in 1919,^[3][4] but it was not until 1943 that excavation began in earnest under the direction of Mary and Louis Leakey, with the assistance of paroled Italian prisoners of war.^[5] Work continued there until 1947. Glynn Isaac took up the excavation in the 1960s^[6] for his dissertation. In the 1980s, research was continued by Richard Potts of the Smithsonian Institution in conjunction with the National Museums of Kenya.

Finds

Animal fossils from Olorgesailie

Human tools are the most prominent of all historic items in the area. The abundant hand axes are characteristic of the Acheulean period, made by hominids between about 600,000 and 900,000 years ago^[7]along what was then the shore of a now dried-up lake. Fossils of various animals have also been found, including those of extinct species of hippo, elephant, zebra, giraffe, and baboon, likely butchered using the hand axes.^[1][3]

In June 2003, a team led by Potts discovered a frontal bone in situ.^[8] Other parts of the small skull (designated KNM-OL 45500) were found in following months. It is 900,000-970,000 years old and probably belongs to Homo erectus, making it the first human fossil found on the site.^[9] The fossil remains were in the same stratigraphic level as two hand axes and several flakes, near dense deposits of hand axes.^[1]

Geology

Preservation of the Aechulean hand axe culture was made possible by heavy falls of alkaline ash from volcanoes around the site that were active at the time. Mounts Suswa and Longonot are volcanic in origin and their vents are likely to have contributed to the ash that accumulated in the Olorgesailie basin. Subsequent earth movements made the stratigraphy and fossils available for study.^[2] Existing temporary lakes and swamps are evidence of a humid climate during part of the middle Pleistocene. Sediments left by the lake cover an area of 50 square miles (about 130 square km).^[2] Of the artifacts, 99% were made from locally derived lavas, particularly trachyte, although small amounts of quartzite and obsidian have been found that required transport of 16-40 km.^[10]

References

Bibliography

• Isaac, Glynn Llywelyn; Isaac, Barbara (1977). Olorgesailie: Archeological Studies of a Middle Pleistocene Lake Basin in Kenya. Chicago: University of Chicago Press. ISBN 0-226-38483-7. 

Coordinates: 1°35′S 36°27′E / 1.58°S 36.45°E / -1.58; 36.45