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

Analyzing handedness using metacarpal cross-sectional geometry in archaic human populations


Department of Anthropology, California State University, Chico

March 27, 2015 , Archview Ballroom Add to calendar

Hand laterality, or the tendency of a population to use one hand over the other in a variety of actions, is a unique, panspecies trait in humans, argued to indicate a more profound structural asymmetry that extends to cerebral function. Previous investigations of morphological and biomechanical asymmetries demonstrate that humans show a strong right-hand bias and greater overall asymmetry in the upper limb, including in the hands themselves. In pre-industrial populations especially, males tend to exhibit greater asymmetry. However, studies of the laterality of hand bones themselves have been primarily limited to the second metacarpal. This study evaluated directional bilateral asymmetry of the hand using the second through fifth metacarpals. These were measured from a sample of 50 adult male and female skeletons from Middle and Late Archaic forager groups excavated from three sites in western central Tennessee. Cross-sectional properties obtained for these individuals were analyzed for magnitude and direction of asymmetry—given by percent directional asymmetry (%DA) and percent absolute asymmetry (%AA)—as well as for the overall shape of the cross-section. Although nonparametric statistical comparisons of asymmetry between the sexes and among metacarpals did not produce significant p-values (p <0.01), the trends of increasing asymmetry in the medial palm caution against using the cross-sectional properties of a single metacarpal to estimate those of the rest. This study highlights the need for further research in this area to establish and understand not only the patterns of asymmetry across the metacarpals, but also the activities that engender them.