Long bone shafts (diaphyses) serve as load-bearing structures during
locomotion, implying a close relationship between diaphyseal form and its
locomotor function. Diaphyseal form-function relationships, however, are
complex, as they are mediated by various factors such as developmental
programs, evolutionary adaptation, and functional adaptation through
bone remodeling during an individual’s lifetime. The effects of the latter
process (‘‘Wolff ’s Law’’) are best assessed by comparing diaphyseal morphologies
of conspecific individuals under different locomotor regimes.
Here we use morphometric mapping (MM) to analyze the morphology of
entire femoral diaphyses in an ontogenetic series of wild and captive common
chimpanzees (Pan troglodytes troglodytes). MM reveals patterns of
variation of diaphyseal structural and functional properties, which cannot
be recognized with conventional cross-sectional analysis and/or geometric
morphometric methods. Our data show that diaphyseal shape, cortical
bone distribution and inferred cross-sectional biomechanical properties
vary both along ontogenetic trajectories and independent of ontogeny.
Mean ontogenetic trajectories of wild and captive chimpanzees, however,
were found to be statistically identical. This indicates that the basic developmental
program of the diaphysis is not altered by different loading
conditions. Significant differences in diaphyseal shape between groups
could only be identified in the distal diaphysis, where wild chimpanzees
exhibit higher mediolateral relative to anteroposterior cortical bone thickness.
Overall, thus, the hypothesis that Wolff ’s Law predominantly governs
long bone diaphyseal morphology is rejected.