Function of the supraorbital region of primates.

The purpose of this study was to test the hypothesis that the functional significance of well-developed brow-ridges in primates is to counter powerful masticatory forces during chewing and biting. This was done by measuring and analysing patterns of in vivo bone strain recorded from rosette strain gauges bonded to the supraorbital region of Macaca fascicularis (the crab-eating or long-tailed monkey) and Papio anubis (the olive baboon) during mastication and incision. It was found that the supraorbital region is strained relatively little during mastication and incision. This indicates that in macaques and baboons there is much more supraorbital bone than is needed to counter masticatory loads, which in turn suggests that their brow-ridges could be considerably smaller yet still counter masticatory stress without structural failure. Therefore, there is no good reason to believe that enlarged brow-ridges in living and/or fossil primates are structural adaptations to counter powerful masticatory forces.