The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


Trabecular bone architecture in the thumb of recent Homo sapiens, Pan, and Late Pleistocene Homo: taxonomic differences and evidence for handedness

NICHOLAS B. STEPHENS1, TRACY KIVELL2, N. HUYNH NGUYEN2, DIETER H. PAHR3, THOMAS GROSS3, JEAN-JACQUES HUBLIN2 and MATTHEW M. SKINNER1,2.

1Skinner Lab, Department of Anthropology, University College London, 2Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, 3Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology

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Evidence for species-wide handedness in non-human apes and when during the Pleistocene the right-hand bias of humans evolved are unresolved issues in paleoanthropology. External skeletal asymmetry is often used as a proxy for hand preference in humans. However, in non-human primates or fossil taxa where samples are small and handedness data are ambiguous or absent, more accurate measures of bone loading are required. Trabecular bone remodels during life and in vivo studies demonstrate that trabecular structure reflects changes in loading.

Therefore, to investigate handedness we quantify the trabecular structure in the first metacarpal (MC1).We compare paired (left/right) metacarpals of Pan troglodytes (n=7), P. paniscus (n=2), modern H. sapiens (n=14) and Late Pleistocene H. neanderthalensis (n=1) and H. sapiens (n=1). All metacarpals were micro-CT scanned at a resolution of ≤ 30 microns and relative bone volume, anisotropy and stiffness of the complete trabecular structure in the metacarpal head and base were quantified using MedTool®. We investigate (1) species differences between Pan and Homo and (2) intra-individual asymmetry in trabecular structure within each species.

Our results indicate that Pan is characterized by significantly greater bone volume but decreased trabecular organization compared to recent and fossil humans. Average absolute asymmetry in relative bone volume is 4.1% and 3.7% in human MC1 heads and bases, respectively; and 1.5% and 1.6% in Pan heads and bases, respectively. Pan displays a leftward bias, while humans and fossil humans confirm a rightward bias. The implications for interpreting behavioral loading in the hominine clade are discussed.

This research was supported by the Max Planck Society.

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