Exploring femoral diaphyseal shape variation in wild and captive chimpanzees by means of morphometric mapping: A test of Wolff's law

摘要

Long bone shafts (diaphyses) serve as load-bearing structures during\udlocomotion, implying a close relationship between diaphyseal form and its\udlocomotor function. Diaphyseal form-function relationships, however, are\udcomplex, as they are mediated by various factors such as developmental\udprograms, evolutionary adaptation, and functional adaptation through\udbone remodeling during an individual’s lifetime. The effects of the latter\udprocess (‘‘Wolff ’s Law’’) are best assessed by comparing diaphyseal morphologies\udof conspecific individuals under different locomotor regimes.\udHere we use morphometric mapping (MM) to analyze the morphology of\udentire femoral diaphyses in an ontogenetic series of wild and captive common\udchimpanzees (Pan troglodytes troglodytes). MM reveals patterns of\udvariation of diaphyseal structural and functional properties, which cannot\udbe recognized with conventional cross-sectional analysis and/or geometric\udmorphometric methods. Our data show that diaphyseal shape, cortical\udbone distribution and inferred cross-sectional biomechanical properties\udvary both along ontogenetic trajectories and independent of ontogeny.\udMean ontogenetic trajectories of wild and captive chimpanzees, however,\udwere found to be statistically identical. This indicates that the basic developmental\udprogram of the diaphysis is not altered by different loading\udconditions. Significant differences in diaphyseal shape between groups\udcould only be identified in the distal diaphysis, where wild chimpanzees\udexhibit higher mediolateral relative to anteroposterior cortical bone thickness.\udOverall, thus, the hypothesis that Wolff ’s Law predominantly governs\udlong bone diaphyseal morphology is rejected.