On the hominid masticatory complex: Biomechanical and evolutionary perspectives

Abstract

All too frequently evolutionary interpretations of the hominid fossil record are based on conclusions about the functioning of the oro-facial apparatus which seldom consider the interrelationships of the many variables of this complex anatomical region. This paper attempts to identify these variables and to apply them in an examination of the argument that worn occlusal surfaces of the dental arches represent a three-dimensional record of occlusal force distribution. It suggests that the pattern and extent of attritional contours should be a valuable tool for interpretation of the adaptive and survival value of the dentition of extinct hominids. In order to understand this force distribution over the dental arches a study must be made of the variables that govern the characteristics of the masticatory force system. Facial morphology and the masticatory musculature produce a particular load distribution for each chewing mode. The teeth upon which the resultant forces act give evidence of the force location and magnitude by the wear produced on the crown. Our studies have shown that occlusal loading patterns, cusp size and morphology, enamel thickness, dental eruption sequence, diet and masticatory manipulative behaviors interact to produce observed wear patterns. In reviewing the several recent reports which describe one or several of these factors in analysis of the hominid dental complex we have concluded that controlled experimental analysis will provide information on the interaction of those factors which produce dental wear. Such analysis should provide a necessary basis for evolutionary interpretation of the hominid dentition.