Craniofacial growth in olive baboons (Papio cynocephalus anubis): browridge formation.

The examination of a developmental series of skulls of olive baboons has led to the generation of a model for browridge formation. Evidence in support of the model comes from surface configuration of browridge bone as studied by scanning electron microscopy, histology of the bone by the analysis of thin sections and by measurements that reflect both depositional cycles in browridge bone and the biomechanics of mastication. The model relates sudden changes in the biomechanical system caused by the tooth eruption cycle to cyclical changes in the formation of browridge bone. We suggest that browridge bone is added during periods of peak stress caused by the positive response of the masticatory muscles to relatively sudden reduction of their biomechanical efficiency.