Dental microwear and Paleoanthropology: Cautions and possibilities

Abstract

Fifty years ago, investigators realized they could gain insights into jaw movement and tooth-use through light-microscope analyses of wear patterns on teeth. Since then, numerous analyses of modern and fossil material have yielded insights into the evolution of tooth use and diet in a wide variety of animals. However, analyses of fossils and archeological material are ultimately dependent on data from three sources, museum samples of modern animals, living animals (in the wild or in the lab), and in vitro studies of microwear formation. These analyses are not without their problems. Thus, we are only beginning to get a clearer picture of the dental microwear of the early hominins. Initial work suggested qualitative differences in dental microwear between early hominids, but it wasn’t until Grine’s analyses of the South African australopithecines that we began to see quantitative, statistical evidence of such differences. Recent analyses have (1) reaffirmed earlier suggestions that Australopithecus afarensis shows microwear patterns indistinguishable from those of the modern gorilla, and (2) shown that the earliest members of our genus may also be distinguishable from each other on the basis of their molar microwear patterns. While this work hints at the possibilities of moving beyond standard evolutionary-morphological inferences, into inferences of actual differences in tooth use, we still know far too little about the causes of specific microwear patterns, and we know surprisingly little about variations in dental microwear patterns (e.g., between sexes, populations, and species). In the face of such challenges, SEM-analyses may be reaching the limits of their usefulness. Thus, two methods are beginning to catch attention as possible ‘‘next steps’’ in the evolution of dental microwear analyses. One technique involves a return to lower magnification analyses, using qualitative assessments of microwear patterns viewed under a light microscope. The advantages of these analyses are that they are cheap and fast, and may easily distinguish animals with extremely different diets. The disadvantages are that they are still subjective and may not be able to detect subtle dietary differences or artifacts on tooth surfaces. Another technique involves the use of scale-sensitive fractal analyses of data from a confocal microscope. Advantages include the ability to quickly and objectively characterize wear surfaces in 3D over entire wear facets. The main disadvantage lies in the newness of the technique and challenges imposed by developing such cutting edge technology. With the development of new approaches, we may be able to take dental microwear analyses to a new level of inference.