Olorgesailie
Encyclopedia
Olorgesailie is a geological formation in East Africa
containing a group of Lower Paleolithic
archaeological sites. It is on the floor of the Eastern Rift Valley in southern Kenya
, 40 miles (64.4 km) southwest of Nairobi
along the road to Lake Magadi
. Olorgesailie is noted for the large number of Acheulean
hand axe
s, associated with animal butchering, discovered there. According to the National Museums of Kenya
, the finds are internationally significant for archaeology, paleontology
, and geology.
were first discovered by the British geologist John Walter Gregory
in 1919, 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
. Work continued there until 1947. Glynn Isaac
took up the excavation in the 1960s for his dissertation. In the 1980s, research was continued by Richard Potts of the Smithsonian Institution
in conjunction with the National Museums of Kenya
.
In June 2003, a team led by Potts discovered a frontal bone
in situ. 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. The fossil remains were in the same stratigraphic
level as two hand axes and several flakes, near dense deposits of hand axes.
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. 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). Of the artifacts, 99% were made from locally derived lava
s, particularly trachyte
, although small amounts of quartzite
and obsidian
have been found that required transport of 16-40 km.
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
containing a group of Lower Paleolithic
Lower Paleolithic
The Lower Paleolithic is the earliest subdivision of the Paleolithic or Old Stone Age. It spans the time from around 2.5 million years ago when the first evidence of craft and use of stone tools by hominids appears in the current archaeological record, until around 300,000 years ago, spanning the...
archaeological sites. It is on the floor of the Eastern Rift Valley in southern Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
, 40 miles (64.4 km) southwest of Nairobi
Nairobi
Nairobi is the capital and largest city of Kenya. The city and its surrounding area also forms the Nairobi County. The name "Nairobi" comes from the Maasai phrase Enkare Nyirobi, which translates to "the place of cool waters". However, it is popularly known as the "Green City in the Sun" and is...
along the road to Lake Magadi
Lake Magadi
Lake Magadi is the southernmost lake in the Kenya Rift Valley, lying in a catchment of faulted volcanic rocks, north of Tanzania's Lake Natron. During the dry season, it is 80% covered by soda and is well known for its wading birds, including flamingos....
. Olorgesailie is noted for the large number of Acheulean
Acheulean
Acheulean is the name given to an archaeological industry of stone tool manufacture associated with early humans during the Lower Palaeolithic era across Africa and much of West Asia, South Asia and Europe. Acheulean tools are typically found with Homo erectus remains...
hand axe
Hand axe
A hand axe is a bifacial Stone tool typical of the lower and middle Palaeolithic , and is the longest-used tool of human history.-Distribution:...
s, associated with animal butchering, discovered there. According to the National Museums of Kenya
National Museums of Kenya
The National Museums of Kenya is a State Corporation that manages Museums, Sites and Monuments in Kenya. It also practices scientific research. Its headquarters and the National Museum are located on Museum Hill, near Uhuru Highway between Central Business District and Westlands in Nairobi...
, the finds are internationally significant for archaeology, paleontology
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
, and geology.
History
The artifactsArtifact (archaeology)
An artifact or artefact is "something made or given shape by man, such as a tool or a work of art, esp an object of archaeological interest"...
were first discovered by the British geologist John Walter Gregory
John Walter Gregory
John Walter Gregory, FRS, was a British geologist and explorer, known principally for his work on glacial geology and on the geography and geology of Australia and East Africa.-Early life:...
in 1919, but it was not until 1943 that excavation began in earnest under the direction of Mary
Mary Leakey
Mary Leakey was a British archaeologist and anthropologist, who discovered the first skull of a fossil ape on Rusinga Island and also a noted robust Australopithecine called Zinjanthropus at Olduvai. For much of her career she worked together with her husband, Louis Leakey, in Olduvai Gorge,...
and Louis Leakey
Louis Leakey
Louis Seymour Bazett Leakey was a British archaeologist and naturalist whose work was important in establishing human evolutionary development in Africa. He also played a major role in creating organizations for future research in Africa and for protecting wildlife there...
, with the assistance of paroled Italian prisoners of war
Prisoner of war
A prisoner of war or enemy prisoner of war is a person, whether civilian or combatant, who is held in custody by an enemy power during or immediately after an armed conflict...
. Work continued there until 1947. Glynn Isaac
Glynn Isaac
Glynn Llywelyn Isaac was a South African archaeologist who specialised in the very early prehistory of Africa...
took up the excavation in the 1960s for his dissertation. In the 1980s, research was continued by Richard Potts of the Smithsonian Institution
Smithsonian Institution
The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities, and magazines...
in conjunction with the National Museums of Kenya
National Museums of Kenya
The National Museums of Kenya is a State Corporation that manages Museums, Sites and Monuments in Kenya. It also practices scientific research. Its headquarters and the National Museum are located on Museum Hill, near Uhuru Highway between Central Business District and Westlands in Nairobi...
.
Finds
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 agoalong 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.In June 2003, a team led by Potts discovered a frontal bone
Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
in situ. 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
Homo erectus
Homo erectus is an extinct species of hominid that lived from the end of the Pliocene epoch to the later Pleistocene, about . The species originated in Africa and spread as far as India, China and Java. There is still disagreement on the subject of the classification, ancestry, and progeny of H...
, making it the first human fossil found on the site. The fossil remains were in the same stratigraphic
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
level as two hand axes and several flakes, near dense deposits of hand axes.
Geology
Preservation of the Aechulean hand axe culture was made possible by heavy falls of alkaline ash from volcanoesVolcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
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. 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). Of the artifacts, 99% were made from locally derived lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
s, particularly trachyte
Trachyte
Trachyte is an igneous volcanic rock with an aphanitic to porphyritic texture. The mineral assemblage consists of essential alkali feldspar; relatively minor plagioclase and quartz or a feldspathoid such as nepheline may also be present....
, although small amounts of quartzite
Quartzite
Quartzite is a hard metamorphic rock which was originally sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite is usually white to gray, though quartzites often occur in various shades of pink...
and obsidian
Obsidian
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock.It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth...
have been found that required transport of 16-40 km.