Experimental approach to the study of the hand-held percussion in the early Acheulean of Casablanca (Morocco)

Knapping techniques in the early technologies have been analysed thanks to experimental researches. Unfortunately, this approach lacks usually a strict comparison with archaeological data, mostly due to the difficulty to recognise indisputable percussion marks or to the paucity of hammerstones. In addition, scarce attention has been paid to the percussion gestures both in technical and motor skill perspectives. The Thomas I-unit L1 site in Casablanca (~1.0 Ma) yielded a rich early North African Acheulean assemblage. A considerable number of cobbles display battering marks, belonging to their use as active hammerstones for knapping. Our hypothesis is that the extension and location of these impact damages demonstrate 1) the adoption of an orthogonal vs. tangential gesture in the hand-held percussion and 2) stable motor habits allowing a repetitive striking precision. An experimental program, coupled with a technological study of the artefacts, was carried out to test this hypothesis combining technical, behavioural, morphological, and biomechanical approaches. The use of 3D morphometric analyses on both archaeological and experimental material allow a quantification of the life-time of the hammerstones. The results allow a careful investigation of the knapping percussion in the early North African Acheulean providing a methodological tool for interpreting early technology percussion behaviours.