West Turkana

From the Middle Pleistocene to the early Holocene : modern human occupation of the Turkana Basin

The Turkana Basin (formerly known as Lake Rudolf) has yielded some of the most important hominin fossils known – from the earliest Australopithecines to the first members of our own genus Homo. It is also where the earliest known fossils of Homo sapiens have been found. Yet, the basin has hardly been explored for evidence for the origins and diversification of modern humans in the last 250,000 years. IN AFRICA targets this period, searching for sites and remains of early modern humans around Lake Turkana.

Geographical location of lake Turkana in relation to Kenya and Africa

The Turkana Basin has been the focus of research in human evolution since the late 1960s, particularly related to late Miocene, Pliocene and early Pleistocene hominins. Later Pleistocene material is rare. Only four fossils from the basin and its surround are of known or likely Middle Pleistocene age – the stratigraphically un-resolved fossils from Eliye Springs1 and Guomde2 and the two early modern humans from the Omo Kibish in southern Ethiopia, discovered by Richard Leakey in 19673-6. Information on the latter locality has been greatly enhanced by the recent work of Fleagle and his team7. These fossils indicate that hominins and the earliest humans lived, at least intermittently, around the lake in the Middle Pleistocene. The fossil and archaeological remains from Kabua, discovered by Whitworth in the late 1950s8-11, remain undated, as do the reported Middle Stone Age sites near Koobi Fora12-14, but together they add to the body of evidence for early human occupation of the basin.

The Holocene history of the area is better known. Some of its outstanding features, such as cairns and stone circles, were reported upon by early travellers to the area15-17. From the 1970s to the late 1980s, several researchers focused on the fascinating and often perplexing Holocene archaeological sites around the basin, which include the record of fishing traditions18, mineralised skeletal remains19, and a number of pillar sites – particularly the work of Robbins and Lynch on the West side20-33, and of Barthelme34-37, Nelson38-39 and others40 on the East, and of Sutton in the Suguta to the South41. More recently, Amanuel Beyin had a season of survey and excavation of early Holocene fishing sites in the area of Kalakol42, while Lisa Hildebrand and her team are carrying out comprehensive new studies of the Pastoralist record of West Turkana, including excavation of the pillar sites at Lothagam and Kalakol43-44. Towards the northern edge of the basin, in southern Ethiopia, Marcus Brittain and Timothy Clack are also studying and excavating exciting megalithic structures45,46.

Despite being central to the current record and models of modern human origins, comparatively little work has been carried out which targeted the Middle and Upper Pleistocene period in the area – Whitworth’s in the late 1950s, RE Leakey’s in the late 1960s, Kelly in the early 1990s and Fleagle in the early 2000s. The Turkana part of the project In Africa focuses on this period of human evolution on the West side of the basin. This study began in 2008 as an informal survey of an area to the southwest of the lake, near the predicted shores of the late Pleistocene/early Holocene lake PalaeoTurkana. It became subsequently formalised as the field project Late Quaternary Human Evolution in West Turkana, directed by Marta Mirazon Lahr and Robert Foley in collaboration Richard Leakey. This project ran three field seasons (LQWT09, LQWT10, LQWT11), as well as a broad field survey (WTFS) organised by RE Leakey in 2010. This work is being continued as part of the In Africa: Pleistocene Human Evolution in West Turkana (INA12/WT and future fieldseasons).

The fieldwork carried out so far has identified twelve new fossiliferous localities, besides the known ones at Eliye Springs, Lobolo, Kabua and Kangatosa north of the Turkwell and Lothagam to the south. The new localities are (from North to South): Nandopet, Nasiritei, and Kagkam between Eliye Springs and Kangatosa by the Turkwell River; Nakwaperiti, Nangorochoto, Kakmat, Nakwapo, Locher Akwan, Natome, Kalakoel, Nataruk and Kayimangin between the Turkwell and Kanapoi to the south. Five of these localities (Nakwapo, Locher Akwan, Natome, Kalakoel and Nataruk) are located within a 10 kmarea, and are being surveyed in some detail.

Location of studied new palaeoanthropological localities from SW Turkana in relation to the reconstructed palaeolake shores.

The project’s field surveys involve several phases: (a) remote sensing and imaging to reconstruct palaeolake margins, shorelines and palaeo-drainage systems; (b) field-based survey for archaeological and fossiliferous deposits using hand-held GPS coordinate recorders, Trimbles and digital photography; (c) geomorphological and stratigraphic survey, with particular focus on river and lake formation processes; (d) collection of informative surface material; (e) total station mapping and excavation of specific sites where particularly important and/or informative fossil/archaeological deposits of later Quaternary age are identified; (f) collection of palaeo-environmental proxies and dating samples. All data are entered into the project’s GIS and finds databases, including photographs. The finds database uses FileMaker Pro software to match the Turkana Fauna Database compiled by Rene Bobe for earlier mammals from the Turkana Basin.

Between 2009 and 2012, these surveys have revealed a large number of fossils and archaeological remains. The fossils range from small fragments (the majority) to complete skeletal elements (including crania) to complete skeletons, and the archaeology from single isolated artefacts to what appear to be living sites. This area includes patches of high density of fish (multiple species, including Nile Perch of different sizes), indicative of high lake transgressions. Exposed palaeolake beach shores show a fauna dominated by hippos, and crocodiles, and to a lesser extent turtles (>52%), while areas both to the west and east of the reconstructed late Pleistocene/early Holocene palaeolake shore contain a greater range of animal species – suids, porcupines, hyraxes, elephants, giraffes, equids, bovids of different sizes, rhinos, carnivores/hyaenas, ostriches, and many fragments of unidentified species. Behavioural evidence is also rich – both MSA and LSA sites have been found that complement those recently described by Shea & Hildebrand47, as well as a rich record of cut-marks on both animal and human remains. Finally, thinly stratified sequences of lake sediments highlight the potential of adding the Turkana Basin to late Pleistocene records of palaeoenvironmental change. The history of sedimentation in this area is extremely complicated; there are successive transgressions, each leaving deposits, but also scouring out older ones, while there is major aeolian erosion during periods of low lake levels. The result is a complex topography with considerable lateral variation.

Most of the finds are of late Pleistocene/early Holocene date (ranging in date between 12,000-7,000 BP), but also include fossil remains dated to the Middle Pleistocene from the site of Kalakoel 3, as well as several MSA assemblages. The material collected is housed at the Turkwell field station of the Turkana Basin Institute (TBI) in accordance with the MOU between the Institute and the National Museums of Kenya (NMK), and accessioned as part of the NMK collections provenanced from the western side of the Turkana Basin (KNM-WT…). Cataloguing and preliminary cleaning of finds is carried out by members of the LQWTIn Africa Project, while technical fossil preparation is carried out by Christopher Kiarie and his team at TBI.

The finds recorded in the 2008 to 2012 field seasons count >780 human remains (from small fragments to complete skeletons), c. 2000 animal remains (from fragments to complete elements and occasionally skeletons, but rare), >130 barbed bone points (mostly fragments), and a large number of lithic artefacts.