Animal movements in the Kenya Rift and evidence for the earliest ambush hunting by hominins OPEN

International audienceAnimal movements in the Kenya Rift Valley today are influenced by a combination of topography and trace nutrient distribution. These patterns would have been the same in the past when hominins inhabited the area. We use this approach to create a landscape reconstruction of Olorgesailie, a key site in the East African Rift with abundant evidence of large-mammal butchery between ~1.2 and ~0.5 Ma BP. The site location in relation to limited animal routes through the area show that hominins were aware of animal movements and used the location for ambush hunting during the Lower to Middle Pleistocene. These features explain the importance of Olorgesailie as a preferred location of repeated hominin activity through multiple changes in climate and local environmental conditions, and provide insights into the cognitive and hunting abilities of Homo erectus while indicating that their activities at the site were aimed at hunting, rather than scavenging. Olorgesailie in the southern Kenya Rift is famous for its unusual abundance of hominin artefacts, fossil mammals and palaeoenvironmental indicators, preserved in sediments spanning ~1.2 to < 0.5 Ma and has been the subject of wide-ranging and intensive studies on hominins and their archeology 1–4 , butchery behaviour 5 and taphonomy 6 , dating and palaeoenvironmental and climatic changes and their impact on human evolution 4,7–13. The rich cultural assemblage is predominantly Acheulean and is found in several layers associated with a palaeolake environment (Supplementary Material Section-5, and Figure S11), alternating between slightly saline, fresh and wetland phases 4,12,13. The origin of artefact accumulation at the site has been the matter of debate ranging from in-situ deposition by hominins to minor fluvial reorganisation 1,14. One cranial specimen of Homo has been recovered 6 and the site preserves evidence of butchery by hominins 1,3. The number of butchered animals, combined with the types of prey, suggest that the hominins were skilful hunters, although their methods have not been previously understood, nor have remains of weapon technology of any kind been discovered 6,13. The first documented record of close encounter hunting of dangerous animals via wooden spears is from the Middle Palaeolithic of Europe, around 400 ka, at Schöningen, Germany 15. The site lies in the centre of the rift floor which is ~60 km wide with many sub-parallel, nearly vertical , fault escarpments 16 constraining east–west movement of large animals and humans (Figs 1 and 2). A large area of the rift floor is covered by trachyte flows that resist erosion while other volcanic rocks including basalts and tuffs are associated with two volcanic edifices (Mts Olorgesailie and Esayeti). Small areas are infilled with sediments carried from the north and the edges of the rift 17. Uplift and back tilting prevents the entry of sediments from outside the main rift. Saline Lake Magadi and associated sediments fill the lowest point in the region (Supplementary Material Section-1)