text: Woodworking activities by early humans: a plant residue analysis on Acheulian stone tools from Peninj (Tanzania).
  The emergence of the Acheulian stone tool industry, between 1.7 and 1.5 m.y.a., constitutes one of the earliest evidences of complex behavior in the process of human evolution. The major technological breakthrough with the Acheulian industry was the beginning of the manufacture of bifacially shaped heavy-duty tools. Handaxes made with a predetermined form and a high degree of symmetry are the main characteristic of the Acheulian tradition. The tools are shaped through a long knapping sequence with a remarkable increase in the technical skills of the makers, compared with the older Oldowan tradition, implying a high degree of planning and foresight. Until recently, the function of these early bifacial tools remained unknown. A large number of these artefacts were found at Peninj in Tanzania, and phytolith analyses on handaxes have yielded for the first time unambiguous evidence of their function as woodworking tools.