The ridge itself is an outcrop of mainly Pliocene/Pleistocene sediments. It is comprised of claystones, siltstones, and sandstones that preserve numerous fossils of terrestrial mammals, including early hominin species. Presently, the ridge is being eroded into a badlands terrain by a series of ephemeral rivers that drain into the northeast portion of modern Lake Turkana. In 1968 Richard Leakey established the Koobi Fora Base Camp on a large sandspit projecting into the lake near the ridge, which he called the Koobi Fora Spit.
A subsequent survey and numerous excavations at multiple sites established the region as a source of hominin fossils shedding light on the evolution of man over the previous 4.2 million years. Far exceeding the number of humanoid fossils are the non-humanoid fossils giving a detailed look at the fauna and flora as far back as the Miocene.
Consequently the government of Kenya in 1973 reserved the region as Sibiloi National Park, establishing a headquarters for the National Museums of Kenya on Koobi Fora Spit. The reserve is well-maintained and is well-guarded by friendly but armed park police. Protection of sites and especially of wildlife are of prime concern. Exploration and excavation continue under the auspices of the Koobi Fora Research Project (KFRP), which collaborates with a number of interested universities and individuals across the world.
Formerly the term, Koobi Fora, has been used to mean one or two initial sites, or the sand spit. Today it can mean any or all points in Sibiloi National Park. The term East Turkana also has come into use with the larger meaning.
Locating and referencing the hundreds of sites in the Koobi Fora region has been an ongoing process. The entire reservation was divided into somewhat over 100 numbered areas. When there were only a relatively few sites it sufficed to locate them with pinpricks on aerial photos and reference them by stating the area. The archaeologists, such as Glynn Isaac, developed a coordinate system. A site acquired a tag consisting of a 4-letter coordinate identifier, such as FxJj, which refers to a small section at the intersection of x and j within a larger section at the intersection of F and J, followed by the number of the site: FxJj 82 refers to the 82nd site within FxJj. In the year 2000 the KFRP went over to a GPS system and has been trying to correlate the pinpricks to its data.
Fossils are labeled with a KNM (Kenya National Museums) accession number, assigned on no other basis than the order in which it was assigned. The number may be preceded in scholarly literature by KNM, KNM ET or KNM ER, where ET and ER stand for East Turkana and East Rudolf, respectively, or just plain ER. Some notable areas are as follows.
The first archaeological site, i.e., FxJj 1, was found in Area 105. It is knicknamed the KBS site for Kay Behrensmeyer Site, after the researcher who first found stone tools there. This site is also the place where the first tuff was found, i.e., the KBS Tuff.
It is known as the location of skull 1470, discovered by Bernard Ngeneo in 1972, reconstructed by Meave Leakey, later reconstructed and named Homo habilis by Richard Leakey, as possibly the first of the genus Homo, and finally Homo rudolfensis. Richard Leakey found it 45 m below the 1.89 my KBS tuff; thus, it is older than that date, but is conventionally dated to it.
|''Representative Fossils||Notes |
|Australopithecus anamensis||4.2-3.9 mya||30731, -44, -45, -50, 35228, -31, -32, -33, -35, -36, -38||Found at Allia Bay. Earliest evidence of bipedal gait.|
|Australopithecus boisei||2.1-1.1 mya.||406, 729, 13750, 23000, 732.|
|Homo habilis||1.9-1.6 mya||1813, 1501, 1502, 1805, 1808.||Called "habilines" or "hablines". Others have been reclassified from this species to Homo rudolfensis. Habilis is considered the earliest or among the earliest of Homo.|
|Homo rudolfensis||1.9-1.6 mya||1470, 1912, 1590, 3732, 1801, 1802, 1472.||Rudolfensis may split again to place some fossils, such as 1470, with Kenyanthropus platyops. Rudolfensis also shares the name, "habline."|
|Homo ergaster||1.8-1.4 mya||992, 730, 731, 819, 820, 3733, 3883.||Considered a sort of pre-erectus if not early Homo erectus, from which it was split. Some refer to ergaster as the African erectus.|
Australopithecus and Homo seem to have coexisted in the region for about one million years. One possible explanation is different food sources. Eventually Australopithecus became exinct and Homo went on to generate later species.
|Industry Name||Dates||Representative Sites||Notes |
|KBS Olduwan||1.89-1.65 mya (KBS Member)||FxJj1, FxJj3, FxJj10.||Comparable to Bed I Olduwan at Olduvai. Low ratio of flake scrapers to choppers.|
|Karari, named after the Karari/Abergaya Ridge.||1.65-1.39 mya (Okote Member)||FxJj16, FxJj18GL, FxJj20M||Comparable to Bed II Olduwan at Olduvai. High ratio of scrapers to choppers.|
The initial archaeology, experimental archaeology, and scientific analysis of the tools were performed by J. W. K. Harris, Nicholas Toth and Glynn Isaac. Harris and Braun report their line of investigation:
Most early human fossils and archaeological remains derive from the upper portion of the Burgi Member, the KBS Member, and the Okote Member. The members reflect changing environments in the Turkana Basin, from lake and delta ones during Burgi Member times to rivers and floodplains in Okote Member times.
The stratigraphy of the Koobi Fora Formation is one of the best studied and calibrated in East Africa. Controversial dating of the KBS Tuff during the 1970's helped to spearhead the development of modern potassium/argon and argon/argon geological dating methods. In addition, the unique fusion between geochronology and mammal evolutionary studies has made the Koobi Fora Formation a standard for interpreting biochronology, environmental change, and ecology for all of Pliocene-Pleistocene Africa.