1Département de Préhistoire, UMR 7194, MNHN Paris, 2Unité d'Anthropologie Bioculturelle, UMR 6578, EFS, Université de la Méditerranée, Marseille, 3Sezione di Antropologia, Soprintendenza al Museo Nazionale Preistorico Etnografico "Luigi Pigorini", Rome, 4Département Géosciences, Université de Poitiers
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Within the limits imposed by a variety of developmental and rheological constraints, bone tissues respond and adapt to the external and internal loads by partial alteration of their shape, mass, microstructure. As bone distribution/organization locally reflects the nature, direction, frequency, and magnitude of such loads, measures of topographic variation of the cortical shell can be used as a proxy for assessing the taxon-specific dynamic relationships individual-biomechanical environment.
Based on the assumption that variation of local morphometric properties along the femoral diaphysis relates to functional levels and patterns of habitual physical activity, primarily to locomotion, we characterized the human and chimpanzee conditions through virtual rendering of their respective endostructural signatures.
By using the CT-based record from 20 modern human and 12 chimpanzee adult femurs, we imaged the site-specific changes in cortical bone through standardized morphometric maps generated by virtually unzipping and vertically unrolling each shaft along the middle of its anterior aspect within the portion 20-80% of the biomechanical length. The analyses were coupled with the comparative assessment of cross-sectional geometric properties.
Compared to Pan, the human femoral diaphysis is more robust (CA and PCA) and presents a higher Ix/Iy ratio in the midshaft region. In both taxa, thickness distribution is not uniform, but widely and unequally changes vertically along the diaphysis and horizontally according to different projections. In chimpanzee, a strong medial and lateral reinforcement is found in the proximal part of the shaft, while in humans it occurs posteriorly. The proximal shaft portion (60-80%) is the most discriminant one.
Funded by MNHN Paris, French CNRS, Univ.ofPoitiers (Centre de Microtomographie)