The evolution and cultural transmission of percussive technology: integrating evidence from palaeoanthropology and primatology.

We bring together the quite different kinds of evidence available from palaeoanthropology and primatology to better understand the origins of Plio-Pleistocene percussive technology. Accumulated palaeoanthropological discoveries now document the Oldowan Complex as the dominant stone tool making culture between 2.6-1.4 Ma, the earlier part of this contemporaneous with pre-Homo hominins. The principal types of artefacts and other remains from 20 Early Stone Age (Oldowan and earliest Acheulean) localities in Africa and elsewhere are reviewed and described. To better understand the ancestral behavioural foundations of this early lithic culture, we examine a range of recent findings from primatology. In particular, we attempt to identify key shared characteristics of Homo and Pan that support inferences about the preparedness of our common ancestor for the innovation of stone tool culture. Findings of particular relevance include: (i) the discovery of an expanding repertoire of percussive and other tool use based on directed use of force among wild chimpanzees, implicating capacities that include significant innovatory potential and appreciation of relevant causal factors; (ii) evidence of material cultural diversity among wild chimpanzees, indicating a readiness to acquire and transmit tool use innovations; and (iii) experimental studies of social learning in chimpanzees and bonobos that now encompass the acquisition of nut cracking through observation of skilled use of hammers and anvils by conspecifics, the diffusion within and between groups of alternative styles of tool use, and the adoption of free-hand stone-to-stone percussion to create useful flakes for cutting to gain access to food resources. We use the distributions of the inferred cultural traits in the wild to assess how diffusion relates to geographic distances, and find that shared traits drop by 50% from the approximately eight characteristic of close neighbours over a distance of approximately 700 km. This pattern is used to explore the implications of analogous processes operating in relation to Early Stone Age sites.