A functional analysis of molar morphometrics in living and fossil hominoids using 2-D digitized images

Diet is an important factor in the overall biology of animals. It is part of a number of complex phenomena involved in the anatomy, physiology and behaviour of the individual. Thus when fossil taxa are represented by dentitions, either principally or completely, a large amount of information regarding the biology of the taxon can be revealed by determining the diet as accurately as possible. This thesis examines the functional aspects of molar occlusal morphology among hominoids. The primary goal is to discover new or more detailed aspects of the diets of Miocene hominoids. The fossil remains of the dentitions of these animals are often badly preserved or extremely worn such that traditional analyses ('e.g.' simple observational techniques, microwear analysis, shearing quotient calculations or enamel thickness estimates) are not possible. At best they may include only a small percentage of the entire sample available. The technique of digitized morphometrics employed here can obtain functionally important information from the cusp areas of molars, including relatively worn teeth. This involves a new approach 'and' a larger sample size in the ongoing investigation into the function of hominoid teeth. Extant hominoids are used as an analogy for the fossil taxa. The diets of living hominoids have been extensively studied and are relatively well understood. A model of molar functional morphology based on known diets is developed here and applied to the fossil hominoids. It is more difficult to predict dietary strategies of fossil hominoids from the early Miocene, based on living taxa. This is either due to their remarkably different diets or due to the possibility that adaptation toward modern ape molar morphologies had not yet developed. Later Miocene hominoids are much easier to classify into diets similar to today's apes. The results indicate a greater diversity in diets was present among the hominoids of the Miocene in comparison to today. Many traditional diets similar to today's folivores, soft fruit frugivores and hard-object feeders were present as were a number of unique diets and some possibly involved seasonal supplementation greater than observed today. This thesis reinforces and sometimes calls into question much of what has been published to date. It also adds new information to this body of knowledge. New aspects of the diets of many Miocene taxa. are discussed, including seasonal supplementation. This enhances what has been revealed by previous techniques. Finally, the functional implications of differences in molar morphology among taxa are discussed. Differences in diet are shown to affect molar morphology which enhances food processing abilities. Each dietary group is separated from the others in the relative size of a set of cusp areas. Among each set of relative cusp areas there is often a functional complex. Thus as cusp areas change with diet, functional complexes such as shearing crest lengths, or molar basin areas change also. These changes are shown to be important in the efficient processing of different food textures incorporated within different dietary strategies.