Developmental mechanics determine long bone allometry.

Evolutionary and developmental factors responsible for the scaling relationships observed in animal skeletons are poorly understood. We have created a mathematical model for long bone cross-sectional development which incorporates both intrinsic growth and extrinsic, adaptive bone modeling in response to changes in bone mechanical strains during ontogeny. The model successfully simulates the developing morphology in individual animals and the bone geometric allometric relationships among adults across many species (range from mouse to elephant in size). Our results suggest that long bone scaling characteristics are not a result of intrinsic genetic factors but are the results of highly conserved, extrinsic biophysical processes whereby bone tissue strains modulate skeletal morphogenesis.