Craniofacial biomechanics and functional and dietary inferences in hominin paleontology Frederick E. Grine a, * , Stefan Judex b , David J. Daegling c , Engin Ozcivici b , Peter S. Ungar d , Mark F. Teaford e , Matt Sponheimer f , Jessica Scott g , Robert S. Scott h , Alan Walker i a Departments of Anthropology and Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794-4364, USA b Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794-2580, USA c Department of Anthropology, University of Florida, Gainesville, FL 32611-7305, USA d Department of Anthropology, University of Arkansas, Fayetteville, AR 72701, USA e Center for Functional Anatomy and Evolution, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA f Department of Anthropology, University of Colorado, Boulder, CO 80309-0233, USA g Doctoral Program in Environmental Dynamics, University of Arkansas, Fayetteville, AR 72701, USA h Department of Anthropology, Rutgers University, New Brunswick, NJ 08901-1414, USA i Departments of Anthropology and Biology, Pennsylvania State University, University Park, PA 16802, USA article info Article history: Received 8 May 2009 Accepted 13 December 2009 Keywords: Finite element analysis Finite element model Biomechanics Australopithecus africanus Diet Premolar Molar Microwear texture analysis Enamel chipping Phylogenetic constraint Validation Adaptation abstract Finite element analysis (FEA) is a potentially powerful tool by which the mechanical behaviors of different skeletal and dental designs can be investigated, and, as such, has become increasingly popular for biomechanical modeling and inferring the behavior of extinct organisms. However, the use of FEA to extrapolate from characterization of the mechanical environment to questions of trophic or ecological adaptation in a fossil taxon is both challenging and perilous. Here, we consider the problems and prospects of FEA applications in paleoanthropology, and provide a critical examination of one such study of the trophic adaptations of Australopithecus africanus. This particular FEA is evaluated with regard to 1) the nature of the A. africanus cranial composite, 2) model validation, 3) decisions made with respect to model parameters, 4) adequacy of data presentation, and 5) interpretation of the results. Each suggests that the results reflect methodological decisions as much as any underlying biological significance. Notwithstanding these issues, this model yields predictions that follow from the posited emphasis on premolar use by A. africanus. These predictions are tested with data from the paleontological record, including a phylogenetically-informed consideration of relative premolar size, and postcanine microwear fabrics and antemortem enamel chipping. In each instance, the data fail to conform to predictions from the model. This model thus serves to emphasize the need for caution in the application of FEA in paleoanthropological enquiry. Theoretical models can be instrumental in the construction of testable hypotheses; but ultimately, the studies that serve to test these hypotheses – rather than data from the models – should remain the source of information pertaining to hominin paleobiology and evolution. Ó 2010 Elsevier Ltd. All rights reserved. Introduction Finite element analysis (FEA, interchangeably referred to as the finite element method or finite element modeling), has recently gained popularity as a technique for characterizing mechanical stresses, strains and forces in primate teeth and skeletons (Richmond et al., 2005; Panagiotopoulou, 2009). This mathematical technique, which was developed in the mid-20th century (Courant, 1943; Turner et al., 1956), has been employed for decades to investigate the mechanical behavior of biological tissues (Rybicki et al., 1972; Gupta et al., 1973; Thresher and Saito, 1973). Because FEA may be used to compare the mechanical behaviors of different designs of the same anatomical structure, it has become a powerful tool for testing biomechanical hypotheses with respect to postcranial bones, skulls and teeth (Richmond et al., 2005; Panagiotopoulou, 2009), and it has found increasing application in the biomechanical modeling and behavioral interpretation of extinct organisms (e.g., Macho et al., 2005; Rayfield, 2007; Wroe, 2008; Rayfield and Milner, 2008; Macho and Shimizu, 2010; Mazetta et al., 2009; Strait et al., 2009; Tseng, 2009). The promise of FEA is a comprehensive accounting of the stress (and strain) field under specified loading conditions in any biological * Corresponding author. E-mail address: frederick.grine@stonybrook.edu (F.E. Grine). Contents lists available at ScienceDirect Journal of Human Evolution journal homepage: www.elsevier.com/locate/jhevol 0047-2484/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jhevol.2009.12.001 Journal of Human Evolution 58 (2010) 293–308