Jessica R. Scott

Technique and Application in Dental Anthropology: Dental microwear analysis: historical perspectives and new approaches

Introduction Diet is widely recognized as the single most important parameter underlying behavioral and ecological differences among living animals. Bioarchaeologists and paleontologists reconstruct diets of past peoples and extinct animals for what they can teach us about matters ranging from the health status of individuals to adaptations and evolution of species. Dental microwear analysis is among the most effective ways of inferring diets of past peoples and fossil species. This approach involves the study of microscopic patterns of use-wear on teeth and is applicable to a broad range of species, giving a direct record of what an individual ate during its lifetime. Researchers have recognized for decades that foods with given material properties leave characteristic patterns of scratches and pits in the molar teeth of humans and other animals. Foods requiring distinct types or levels of ingestive behavior also leave characteristic microscopic wear patterns in incisor teeth. Our understandings of relationships between dental microwear and diet/subsistence is improving with each passing year as new methods of analysis are developed and investigators continue to expand the number and variety of samples examined. In this chapter we summarize one new method, dental microwear texture analysis, and offer some new data to illustrate the potential of this approach. We also briefly review some of the seminal microwear studies conducted over the past half century that put this and other work into historical context.

Dental microwear texture analysis of extant African Bovidae

Abstract Bovids are often used as paleoenvironmental proxies because they are among the most commonly recovered large mammals at many fossil hominin sites and because modern African bovids occupy a wide range of dietary and environmental niches. This study uses dental microwear texture analysis to examine 25 species of extant African bovids, representing six dietary categories and with an emphasis on various levels of mixed feeding. The results show significant differences among the dietary classifications and confirm previous work suggesting that grazing taxa have less complex, more anisotropic surfaces with smaller features than browsing taxa. The results also indicate that dental microwear texture analysis can distinguish beyond the classic grazer-browser-mixed feeder trichotomy and accurately separate variable grazers, generalists, browser-grazer intermediates and frugivores from obligate grazers and browsers, as well as from one another. Some differences among taxa within dietary categories were also found, probably reflecting seasonal and/or geographic differences in diet. In addition to demonstrating the effectiveness of the technique at differentiating between different levels of mixed feeding in bovids, this study also provides a comprehensive comparative dataset of extant bovid microwear textures that can be applied to fossil taxa from sites and time periods across Africa.

Dental microwear texture analysis of two families of subfossil lemurs from Madagascar

This study employs dental microwear texture analysis to reconstruct the diets of two families of subfossil lemurs from Madagascar, the archaeolemurids and megaladapids. This technique is based on three-dimensional surface measurements utilizing a white-light confocal profiler and scale-sensitive fractal analysis. Data were recorded for six texture variables previously used successfully to distinguish between living primates with known dietary differences. Statistical analyses revealed that the archaeolemurids and megaladapids have overlapping microwear texture signatures, suggesting that the two families occasionally depended on resources with similar mechanical properties. Even so, moderate variation in most attributes is evident, and results suggest potential differences in the foods consumed by the two families. The microwear pattern for the megaladapids indicates a preference for tougher foods, such as many leaves, while that of the archaeolemurids is consistent with the consumption of harder foods. The results also indicate some intraspecific differences among taxa within each family. This evidence suggests that the archaeolemurids and megaladapids, like many living primates, likely consumed a variety of food types.

Craniofacial biomechanics and functional and dietary inferences in hominin paleontology

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.

Carnivoran dental microwear textures: comparability of carnassial facets and functional differentiation of postcanine teeth

No abstract available

Folivory or fruit/seed predation for Mesopithecus, an earliest colobine from the late Miocene of Eurasia?

Here we compare dental microwear textures from specimens of the fossil genus Mesopithecus (Cercopithecidae, Colobinae) from the late Miocene of Eastern Europe with dental microwear textures from four extant primate species with known dietary differences. Results indicate that the dental microwear textures of Mesopithecus differ from those of extant leaf eaters Alouatta palliata and Trachypithecus cristatus and instead resemble more closely those of the occasional hard-object feeders Cebus apella and Lophocebus albigena. Microwear texture data presented here in combination with results from previous analyses suggest that Mesopithecus was a widespread, opportunistic feeder that often consumed hard seeds. These data are consistent with the hypothesis that early colobines may have preferred hard seeds to leaves.

A Dental Microwear Texture Analysis of the Mio-Pliocene Hyaenids from Langebaanweg, South Africa

Hyaenids reached their peak diversity during the Mio-Pliocene, when an array of carnivorous species emerged alongside dwindling civet-like and mongoose-like insectivorous/omnivorous taxa. Significantly, bone-cracking morphological adaptations were poorly developed in these newly-emerged species. This, their general canid-like morphology, and the absence/rarity of canids in Eurasia and Africa at the time, has led researchers to hypothesise that these carnivorous Mio-Pliocene hyaenas were ecological vicars to modern canids. To shed further light on their diets and foraging strategies, we examine and compare the dental microwear textures of Hyaenictitherium namaquensis, Ikelohyaena abronia, Chasmaporthetes australls, and Hyaenictis hendeyi from the South African Mio-Pliocene site of Langebaanweg with those of the extant feliforms Crocuta crocuta, Acinonyx jubatus, and Panthera leo (caniforms are not included because homologous wear facets are not directly comparable between the suborders). Sample sizes for individual fossil species are small, which limits confidence in assessments of variation between the extinct taxa; however, these Mio-Pliocene hyaenas exhibit surface complexity and textural fill volume values that are considerably lower than those exhibited by the living hyaena, Crocuta crocuta. Dental microwear texture analysis thus supports interpretations of craniodental evidence suggesting low bone consumption in carnivorous Mio-Pliocene hyaenas.

Dental microwear texture analysis and diet in the Dmanisi hominins

Reconstructions of foraging behavior and diet are central to our understanding of fossil hominin ecology and evolution. Current hypotheses for the evolution of the genus Homo invoke a change in foraging behavior to include higher quality foods. Recent microwear texture analyses of fossil hominin teeth have suggested that the evolution of Homo erectus may have been marked by a transition to a more variable diet. In this study, we used microwear texture analysis to examine the occlusal surface of 2 molars from Dmanisi, a 1.8 million year old fossil hominin site in the Republic of Georgia. The Dmanisi molars were characterized by a moderate degree of surface complexity (Asfc), low textural fill volume (Tfv), and a relatively low scale of maximum complexity (Smc), similar to specimens of early African H. erectus. While caution must be used in drawing conclusions from this small sample (n = 2), these results are consistent with continuity in diet as H. erectus expanded into Eurasia.