Mechanical Impact of Incisor Loading on the Primate Midfacial Skeleton and its Relevance to Human Evolution
Version of Record online: 16 MAR 2010
Copyright © 2010 Wiley-Liss, Inc.
The Anatomical Record
Special Issue: From Head to Tail: New Models and Approaches in Primate Functional Anatomy and Biomechanics
Volume 293, Issue 4, pages 607–617, April 2010
How to Cite
Wang, Q., Wright, B. W., Smith, A., Chalk, J. and Byron, C. D. (2010), Mechanical Impact of Incisor Loading on the Primate Midfacial Skeleton and its Relevance to Human Evolution. Anat Rec, 293: 607–617. doi: 10.1002/ar.21123
- Issue online: 16 MAR 2010
- Version of Record online: 16 MAR 2010
- Manuscript Accepted: 11 JAN 2010
- Manuscript Received: 7 JAN 2010
- National Science Foundation HOMINID and Mercer Seed Fund. Grant Numbers: BCS -0725183, BCS -0725136
- facial projection;
- paramasticatory behavior;
The midfacial skeleton in the human lineage demonstrates a wide spectrum of variation that may be the consequence of different environmental and mechanical selective pressures. However, different facial configurations may develop under comparable selective regimes. For example, the Neanderthal high and projected face and the Inuit broad and flat face are hypothesized to be the consequence of (1) life in a cold climate, and (2) excessive paramasticatory stresses focused on the anterior dentition. In this study, the second of these two hypotheses is tested using finite element analyses of a monkey skull. Results indicate that incisor loading induces heavy stress in the anterior midface of macaques. Additional analyses using incremental increases in the anteroinferior tilt of the skull to simulate different magnitudes of facial projection revealed that comparable muscular force generates less stress in a less-projected face. However, the findings of our final analyses, which attempted to combine biting with the incisors and pulling with the hands, differed from the analyses that mimicked only incisor loading (without any sort of anterior pulling component). These findings suggest that shortening the face may be the most effective way to compensate for anterior dental loading but not necessarily offset the forces incurred when using the anterior dentition as a vice for various paramasticatory behaviors. Although Neanderthals may have frequently loaded their anterior dentition, countervailing selection pressures, such as the inclusion of tough foods in the diet that demanded molar grinding, may have selected for a longer face with a lower load- to lever-arm ratio. Anat Rec, 293:607–617, 2010. © 2010 Wiley-Liss, Inc.