The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

The biomechanics and functional anatomy of stone tool production


1Division of Anthropology, American Museum of Natural History, 2Center for the Advanced Study of Hominid Paleobiology, The George Washington University, 3Department of Biology, Chatham University, 4Department of Mechanical and Materials Engineering, Queen’s University

March 26, 2015 3:45, Grand Ballroom E/F/G Add to calendar

Recent archaeological finds show that stone tools predate Homo by more than half a million years. However, early lithic assemblages are rare and often have low numbers of tools and flakes. Only after the appearance of Homo are increases in site and artifact density evident. While these archaeological data indirectly support the hypothesis that efficient tool production and use are linked to adaptive changes seen in the genus Homo, these links remain tenuous. Understanding the functional consequences of shifts in hominin forelimb anatomy on knapping performance may provide a means of evaluating this hypothesis.

This study tests a biomechanical model of how power is generated during knapping. Kinematic data were collected from ten experienced knappers making simple Oldowan flakes from fine-grained basalt. These knappers were also fitted with motion-limiting braces on their shoulder and wrist to mimic aspects of the ancestral condition. Inverse dynamics analyses were performed to calculate angular velocities, torques and power at each major joint in the forelimb. Results show that modern knappers generate power using either an elbow or a shoulder-dominated strategy. While both produced usable flakes, the elbow-dominated strategy was more efficient, requiring fewer strikes per flake and less mechanical work. These efficiency data suggest that elbow-dominated knapping mechanics may have been favored by our tool-making ancestors. Further, we suggest that knapping behavior does not explain the anatomical shifts in humeral torsion and shoulder orientation between Australopithecus and Homo, but may have influenced selection for increased wrist hyperextension.

Acknowledgements: Funded by the National Science Foundation (CNS-1337722, SBE-1103470), L’Oreal USA for Women in Science Foundation, GW Office of the Provost, GW Centers and Institute Facilitating Fund, and the AMNH.