Biomechanical strategies during Oldowan and Acheulean stone tool production Open Access
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Multiple hominin species used and/or produced stone tools (e.g., Australopithecus afarensis, Paranthropus robustus, Homo habilis), yet evidence suggests that only later Homo (i.e., H. erectus sensu lato) intensified and developed the behavior. This difference has been attributed to later Homo's ability to execute efficient tool production, to the exclusion of earlier hominin species. However, we lacked the data on upper limb motions needed to evaluate the biomechanical context of stone tool production. With this in mind, the goal of this dissertation was to investigate the kinematic strategies used by modern humans in the production of Early Stone Age stone tools in order to test the primary hypothesis that modern humans' upper limb condition contributes to efficiency and accuracy during stone tool production. My collaborators and I used high-speed 3-D motion capture technology and a high-speed manual pressure sensor system to capture some of the only quantitative data on knapping kinematics, and the only quantitative data on manual pressure distribution during stone tool production presently available. The data and conclusions produced during this dissertation document the upper limb motions employed during Oldowan and Acheulean stone tool production. In doing so, my collaborators and I have 1) provided evidence against hypotheses directly linking the derived pollical condition to stone tool manufacture; 2) demonstrated that knappers employ a common kinematic strategy that has proven to be energetically efficient in a variety of contemporary activities; 3) support the hypothesis that modern humans exploit the upper ranges of their wrist extension ranges during knapping and in doing so achieve greater accuracy and efficiency; and 4) provided evidence that large-scale motion sequences (e.g., sequence of force application) rather than small scale motion sequences (e.g., sequence of joint motions) contribute to greater right hemisphere activity during Acheulean handaxe manufacture compared with Oldowan flake production. This dissertation and the data collected in its course represent another step towards understanding the manner in which modern humans produce stone tools and the relationship of our upper limb anatomy to this developmentally significant behavior.