Allometry of facial mobility in anthropoid primates: Implications for the evolution of facial expression (pages 70–81)

摘要

Body size may be an important factorninfluencing the evolution of facial expression in anthropoidnprimates due to allometric constraints on the perceptionnof facial movements. Given this hypothesis, Intested the prediction that observed facial mobility is positivelyncorrelated with body size in a comparative samplenof nonhuman anthropoids. Facial mobility, or the varietynof facial movements a species can produce, was estimatednusing a novel application of the Facial ActionnCoding System (FACS). I used FACS to estimate facialnmobility in 12 nonhuman anthropoid species, based onnvideo recordings of facial activity in zoo animals. Bodynmass data were taken from the literature. I used phylogeneticngeneralized least squares (PGLS) to perform anmultiple regression analysis with facial mobility as thendependent variable and two independent variables: lognbody mass and dummy-coded infraorder. Together, bodynmass and infraorder explain 92% of the variance innfacial mobility. However, the partial effect of body massnis much stronger than for infraorder. The results of mynstudy suggest that allometry is an important constraintnon the evolution of facial mobility, which may limit thencomplexity of facial expression in smaller species. Morenwork is needed to clarify the perceptual bases of thisnallometric pattern. Am J Phys Anthropol 138:70–81,n2009. VVC 2008 Wiley-Liss, Inc.