Olorgesailie is a
geological formation
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...
in
East Africa, on the floor of the
Eastern Rift Valley
The Gregory Rift is the eastern branch of the East African Rift fracture system. The rift is being caused by the separation of the Somali plate from the Nubian plate, driven by a thermal plume. Although the term is sometimes used in the narrow s ...
in southern
Kenya
)
, national_anthem = " Ee Mungu Nguvu Yetu"()
, image_map =
, map_caption =
, image_map2 =
, capital = Nairobi
, coordinates =
, largest_city = Nairobi
...
, southwest of
Nairobi
Nairobi ( ) is the capital and largest city of Kenya. The name is derived from the Maasai phrase ''Enkare Nairobi'', which translates to "place of cool waters", a reference to the Nairobi River which flows through the city. The city proper h ...
along the road to
Lake Magadi
Lake Magadi is the southernmost lake in the Kenyan 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 f ...
. It contains a group of
Lower Paleolithic archaeological sites. Olorgesailie is noted for the large number of
Acheulean
Acheulean (; also Acheulian and Mode II), from the French ''acheuléen'' after the type site of Saint-Acheul, is an archaeological industry of stone tool manufacture characterized by the distinctive oval and pear-shaped "hand axes" associated ...
hand axe
A hand axe (or handaxe or Acheulean hand axe) is a prehistoric stone tool with two faces that is the longest-used tool in human history, yet there is no academic consensus on what they were used for. It is made from stone, usually flint or ch ...
s discovered there that are associated with animal butchering. According to the
National Museums of Kenya, the finds are internationally significant for archaeology,
palaeontology, and geology.
History
![Olorgesailie axes](https://upload.wikimedia.org/wikipedia/commons/9/99/Olorgesailie_axes.jpg)
The
artifacts were first discovered by the British geologist
John Walter Gregory
John Walter Gregory, , (27 January 1864 – 2 June 1932) 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.
The Gregory Rift in the Great Rift ...
in 1919, but it was not until 1943 that excavation began in earnest under the direction of
Mary
Mary may refer to:
People
* Mary (name), a feminine given name (includes a list of people with the name)
Religious contexts
* New Testament people named Mary, overview article linking to many of those below
* Mary, mother of Jesus, also calle ...
and
Louis Leakey, with the assistance of
paroled
Parole (also known as provisional release or supervised release) is a form of early release of a prison inmate where the prisoner agrees to abide by certain behavioral conditions, including checking-in with their designated parole officers, or ...
Italian
prisoners of war. Work continued there until 1947.
Glynn Isaac
Glynn Llywelyn Isaac (19 November 1937 – 5 October 1985) was a South African archaeologist who specialised in the very early prehistory of Africa, and was one of twin sons born to botanists William Edwyn Isaac and Frances Margaret Leighton ...
took up the excavation in the 1960s for his dissertation. In the 1980s, research was continued by
Richard Potts
Richard Potts (July 19, 1753November 26, 1808) was an American politician and jurist.
Early life and career
Potts was born in Upper Marlboro, Maryland, and lived there until he moved with his family to the Barbados Islands in 1757. He return ...
of the
Smithsonian Institution
The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums and education and research centers, the largest such complex in the world, created by the U.S. government "for the increase and diffusion of knowledge". Founded ...
in conjunction with the
National Museums of Kenya.
Finds
![Olorgesailie fossils](https://upload.wikimedia.org/wikipedia/commons/7/7b/Olorgesailie_fossils.jpg)
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
hominin
The Hominini form a taxonomic tribe of the subfamily Homininae ("hominines"). Hominini includes the extant genera ''Homo'' (humans) and '' Pan'' (chimpanzees and bonobos) and in standard usage excludes the genus ''Gorilla'' (gorillas).
The ...
s 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 to have been butchered with the aid of the hand axes.
In June 2003, a team led by Potts discovered a
frontal bone
The frontal bone is a bone in the human skull. The bone consists of two portions.'' Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bony part of the forehead, pa ...
''
in situ
''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...
''. Other parts of the small skull (designated KNM-OL 45500) were found in following months. The frontal bone is 900,000 to 970,000 years old and probably belonged to ''
Homo erectus'', thereby making it the first human fossil found on the site. The fossil remains were in the same
stratigraphic
Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks.
Stratigraphy has three related subfields: lithostra ...
level as two hand axes and several flakes, near dense deposits of hand axes.
In 2018, evidence dating to about 320,000 years ago was found at Olorgesailie of the early emergence of complex and modern behaviors, possibly associated with early ''
Homo sapiens
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
'', including: the trade and long-distance transportation of resources (such as obsidian), the use of pigments, and the possible making of projectile points. The emergence of these behaviors, it is observed by the authors of three 2018 studies on the site, approximately corresponds to the earliest known ''Homo sapiens'' fossil remains from Africa (such as at
Jebel Irhoud
Jebel Irhoud or Adrar n Ighoud ( zgh, ⴰⴷⵔⴰⵔ ⵏ ⵉⵖⵓⴷ, Adrar n Iɣud; ar, جبل إيغود, žbəl iġud), is an archaeological site located just north of the locality known as Tlet Ighoud, approximately south-east of the cit ...
, Morocco and
Florisbad
Florisbad is a health resort 45 km northwest of Bloemfontein and 47 km south-west of Brandfort
Brandfort, officially renamed Winnie Mandela in 2021, is a small agricultural town in the central Free State province of South Africa, about ...
, South Africa) dated to about the same period, and it is suggested that complex behaviors began in Africa around the time of the emergence of ''Homo sapiens''.
Geology
Preservation of the Aechulean hand axe culture was made possible by heavy falls of alkaline
ash from volcanoes near the site that were active at the time.
Mount Suswa
Mount Suswa is a shield volcano in the Great Rift Valley, Kenya. It is located between Narok and Nairobi, the capital of Kenya. The northwestern part of Mount Suswa is in Narok County, while the eastern and southern part are in Kajiado County. ...
and
Mount Longonot
Mount Longonot is a stratovolcano located southeast of Lake Naivasha in the Great Rift Valley of Kenya, Africa. It is thought to have last erupted in the 1860s. Its name is derived from the Maasai word ''Oloonong'ot'', meaning "mountains of man ...
are volcanoes, and their vents are likely to have contributed to the ash that accumulated in the Olorgesailie basin. Subsequent sedimentation covering the site has preserved the fossils and created a stratigraphy which helps in dating them. Existing temporary lakes and swamps give evidence of a humid climate during the middle Pleistocene. Sediments left by the lake cover an area of about . Of the artefacts, 99% were made from locally derived
lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...
s, particularly
trachyte
Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and al ...
, although small amounts of
quartzite
Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tec ...
and
obsidian have been found, indicating transportation over 16 to 40 km.
Olorgesailie Drilling Project
In the 21 October 2020 issue of the journal ''Science Advances'', an interdisciplinary team of scientists led by Richard Potts, director of the Human Origins Program at the Smithsonian’s National Museum of Natural History, described the prolonged period of instability across the landscape in this part of Africa (now Kenya) that occurred at the same time humans in the region were undergoing a major behavioral and cultural shift in their evolution. Erosion at Olorgesailie, a hilly area full of sedimentary outcrops, had removed the geologic layers representing some 180,000 years of time at exactly the period of this evolutionary transition. Due to this, his team had to drill for sediments. They arranged to have a Nairobi company drill in the nearby Koora basin, extracting sediment from as deep into the earth as they could. The drill site, about from the archaeological dig sites, was a flat, grassy plain, and the team had no clear idea what was beneath its surface. With the involvement and support from the National Museums of Kenya and the local Oldonyo Nyokie community, a 139-meter core was removed from the earth. That cylinder of earth, just four centimeters in diameter, turned out to represent 1 million years of environmental history. Colleagues in the National Museum of Natural History’s Human Origins Program and Department of Paleobiology and dozens of collaborators at institutions worldwide worked to analyze the environmental record they had obtained, which is now the most precisely dated African environmental record of the past 1 million years. They found that after a long period of stability, the environment in this part of Africa became more variable around 400,000 years ago, when tectonic activity fragmented the landscape. By integrating information from the drill core with knowledge gleaned from fossils and archeological artifacts, they determined that the entire ecosystem evolved in response.
References
Bibliography
*
{{Archaeological sites in Kenya
Archaeological sites in Kenya
Pleistocene paleontological sites of Africa
Prehistoric Kenya
Paleoanthropological sites
Archaeological sites of Eastern Africa