Early Pleistocene hominid foraging strategies along the ancestral Omo River at Koobi Fora, Kenya

Abstract

Abstract Reconstructions of hominid foraging activities at Koobi Fora must account for an uneven distribution of Plio-Pleistocene archaeological sites and hominid fossils. Near the 1·64 million year old stratigraphic level of the Okote Tuff complex, stone raw materials and tools are abundant in fluvial contexts at the Karari Ridge. In contrast, hominid fossils are abundant but stone raw materials are absent and tools are rare in fluvial and shallow, ephemeral lake margin contexts at Ileret and at the Koobi Fora Ridge. As the distance to the nearest source of stone raw materials increases, from local abundance at the Karari Ridge to 5 km at Ileret and to at least 15 km at the Koobi Fora Ridge, the archaeological visibility of hominid activities, as defined by sites with stone tools, decreases to essentially zero. Cut marks made with large stone tools during Butchery occur on more than 66 fossil bones from Ileret and especially from the Koobi Fora Ridge. In the absence of associated stone tools, those define a new kind of stone age site. The fossils with cut marks represent diverse skeletal parts and taxa, especially hippopotamus, and occur over several square km as isolated specimens, as associated elements of one carcass, and as concentrations of conjoining pieces and multiple carcasses. Some of the defleshing cut marks occur on intact limb elements that were not utilized for marrow. Early Homo erectus probably carried large stone tools during their foraging visits to these sub-regions, using the tools in butchery but rarely discarding them. Alternative hominid foraging strategies along the ancestral Omo River and taphonomic processes of site formation are discussed.