Endostructural characterisation of the regourdou 1 neanderthal proximal arm: Bilateral asymmetry and handedness

Abstract

Cross-sectional properties of long bones are commonly used for reconstructing mechanical loading histories related to locomotion, subsistence strategies, manipulative behavior. In this respect, a significant degree of functional bilateral asymmetry of the proximal arm, likely related to unilateral activity levels, has been reported for Neanderthals. Previous external analysis of the upper limb bones of the Regourdou 1 adult partial skeleton from Montignac-sur-Vézère, France, showed right side hypertrophy (Vander­meersch and Trinkaus 1995). In order to precise the amount of functional asymmetry and handedness characterizing this individual, we have investigated at 35%, 44%, 50%, and 65% of the shaft length the cross-sectional geometric properties of its humeri by means of synchrotron radiation microtomography (SR-μCT). Present results support previous conclusion that Regourdou 1 was right-handed. Nonetheless, while a greater strength to compression, flexion, and torsion is shown by the right humerus, only a modest degree of right dominance characterizes this individual with respect to the available Neanderthal figures. Interestingly, the high-resolution three-dimensional-mapping of the humeral cortical bone volume documents a heterogeneous topographic pattern of structural asymmetry along the shaft.