Allometry of facial mobility in anthropoid primates: Implications for the evolution of facial expression
Version of Record online: 18 AUG 2008
Copyright © 2008 Wiley-Liss, Inc.
American Journal of Physical Anthropology
Volume 138, Issue 1, pages 70–81, January 2009
How to Cite
Dobson, S. D. (2009), Allometry of facial mobility in anthropoid primates: Implications for the evolution of facial expression. Am. J. Phys. Anthropol., 138: 70–81. doi: 10.1002/ajpa.20902
- Issue online: 1 DEC 2008
- Version of Record online: 18 AUG 2008
- Manuscript Accepted: 16 JUN 2008
- Manuscript Received: 25 AUG 2007
- National Science Foundation (Dissertation Improvement Grant). Grant Number: BCS 0424160
- Sigma Xi (Grant-in-Aid of Research)
- facial movement;
Body size may be an important factor influencing the evolution of facial expression in anthropoid primates due to allometric constraints on the perception of facial movements. Given this hypothesis, I tested the prediction that observed facial mobility is positively correlated with body size in a comparative sample of nonhuman anthropoids. Facial mobility, or the variety of facial movements a species can produce, was estimated using a novel application of the Facial Action Coding System (FACS). I used FACS to estimate facial mobility in 12 nonhuman anthropoid species, based on video recordings of facial activity in zoo animals. Body mass data were taken from the literature. I used phylogenetic generalized least squares (PGLS) to perform a multiple regression analysis with facial mobility as the dependent variable and two independent variables: log body mass and dummy-coded infraorder. Together, body mass and infraorder explain 92% of the variance in facial mobility. However, the partial effect of body mass is much stronger than for infraorder. The results of my study suggest that allometry is an important constraint on the evolution of facial mobility, which may limit the complexity of facial expression in smaller species. More work is needed to clarify the perceptual bases of this allometric pattern. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc.