Mark F. Teaford

Dental microwear texture analysis shows within-species diet variability in fossil hominins.

Reconstructing the diets of extinct hominins is essential to understanding the paleobiology and evolutionary history of our lineage. Dental microwear, the study of microscopic tooth-wear resulting from use, provides direct evidence of what an individual ate in the past. Unfortunately, established methods of studying microwear are plagued with low repeatability and high observer error. Here we apply an objective, repeatable approach for studying three-dimensional microwear surface texture to extinct South African hominins. Scanning confocal microscopy together with scale-sensitive fractal analysis are used to characterize the complexity and anisotropy of microwear. Results for living primates show that this approach can distinguish among diets characterized by different fracture properties. When applied to hominins, microwear texture analysis indicates that Australopithecus africanus microwear is more anisotropic, but also more variable in anisotropy than Paranthropus robustus. This latter species has more complex microwear textures, but is also more variable in complexity than A. africanus. This suggests that A. africanus ate more tough foods and P. robustus consumed more hard and brittle items, but that both had variable and overlapping diets.

Diet in Early Homo: A Review of the Evidence and a New Model of Adaptive Versatility

Several recent studies have stressed the role of dietary change in the origin and early evolution of our genus in Africa. Resulting models have been based on nutrition research and analogy to living peoples and nonhuman primates or on archeological and paleoenvironmental evidence. Here we evaluate these models in the context of the hominin fossil record. Inference of diet from fossils is hampered by small samples, unclear form-function relationships, taphonomic factors, and interactions between cultural and natural selection. Nevertheless, craniodental remains of Homo habilis, H. rudolfensis, and H. erectus offer some clues. For example, there appears to be no simple transition from an australopith to a Homo grade of dietary adaptation, or from closed forest plant diets to reliance on more open-country plants or animals. Early Homo species more likely had adaptations for flexible, versatile subsistence strategies that would have served them well in the variable paleoenvironments of the African Plio-Pleistocene.

Dental microwear texture and anthropoid diets

Dental microwear has long been used as evidence concerning the diets of extinct species. Here, we present a comparative baseline series of dental microwear textures for a sample of 21 anthropoid primate species displaying interspecific and intraspecific dietary variability. Four dental microwear texture variables (complexity, anisotropy, textural fill volume, and heterogeneity) were computed based on scale-sensitive fractal analysis and high-resolution three-dimensional renderings of microwear surfaces collected using a white-light confocal profiler. The purpose of this analysis was to assess the extent to which these variables reflect variation in diet. Significant contrasts between species with diets known to include foods with differing material properties are clearly evident for all four microwear texture variables. In particular, species that consume more tough foods, such as leaves, tended to have high levels of anisotropy and low texture complexity. The converse was true for species including hard and brittle items in their diets either as staples or as fallback foods. These results reaffirm the utility of dental microwear texture analysis as an important tool in making dietary inferences based on fossil primate samples.

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 and stable isotopes inform the paleoecology of extinct hominins.

Determining the diet of an extinct species is paramount in any attempt to reconstruct its paleoecology. Because the distribution and mechanical properties of food items may impact postcranial, cranial, mandibular, and dental morphologies related to their procurement, ingestion, and mastication, these anatomical attributes have been studied intensively. However, while mechanical environments influence skeletal and dental features, it is not clear to what extent they dictate particular morphologies. Although biomechanical explanations have been widely applied to extinct hominins in attempts to retrodict dietary proclivities, morphology may say as much about what they were capable of eating, and perhaps more about phylogenetic history, than about the nature of the diet. Anatomical attributes may establish boundary limits, but direct evidence left by the foods that were actually (rather than hypothetically) consumed is required to reconstruct diet. Dental microwear and the stable light isotope chemistry of tooth enamel provide such evidence, and are especially powerful when used in tandem. We review the foundations for microwear and biogeochemistry in diet reconstruction, and discuss this evidence for six early hominin species (Ardipithecus ramidus, Australopithecus anamensis, Au. afarensis, Au. africanus, Paranthropus robustus, and P. boisei). The dietary signals derived from microwear and isotope chemistry are sometimes at odds with inferences from biomechanical approaches, a potentially disquieting conundrum that is particularly evident for several species.

Frontiers of Contact: Bioarchaeology of Spanish Florida

The arrival of Europeans in the New World had profound and long-lasting results for the native peoples. The record for the impact of this fundamental change in culture, society, and biology of Native Americans is well documented historically. This paper reviews the biological impact of the arrival of Europeans on native populations via the study of pre- and postcontact skeletal remains in Spanish Florida, the region today represented by coastal Georgia and northern Florida. The postcontact skeletal series, mostly drawn from Roman Catholic mission sites, are among the most comprehensive in the Americas, providing a compelling picture of adaptation and stress in this setting. Study of paleopathology, dental and skeletal indicators of physiological stress, stable isotope (carbon and nitrogen) analysis, tooth microwear, and skeletal morphology (cross-sectional geometry) reveals major alterations in quality of life and lifestyle. The bioarchaeological record indicates a general deterioration in health, declining dietary diversity and nutritional quality, and increasing workload in the contact period. The impact of contact in Spanish Florida appears to have been more dramatic in comparison with other regions, which likely reflects the different nature of contact relations in this setting versus other areas (e.g., New England, New France). The bioarchaeological record represents an important information source for understanding the dynamics of biocultural change resulting from colonization and conquest.

THE DIET OF WORMS: AN ANALYSIS OF MOLE DENTAL MICROWEAR

Abstract We compared microwear from shearing facets of lower molars from Parascalops breweri (the hairy-tailed mole) and Scapanus orarius (the coast mole) with that from other small mammal species including a tenrec, a hedgehog, 3 primates, and 2 bats. The 2 mole species exhibit a distinct microwear pattern that is characterized by many short, narrow scratches, and relatively few pits. Although the molars of the streaked tenrec (Hemicentetes nigriceps) differ profoundly in morphology from those of moles, they show a very similar pattern of microwear on their shearing facets. This common pattern (missing in the rest of the comparison sample) is likely a product of the importance of earthworms in the diets of both H. nigriceps and the moles and is plausibly explained by the interaction between teeth and soil from the inside and outside of earthworms. These results may be useful in interpreting microwear patterns in fossil mammals.

Viewpoints: Feeding mechanics, diet, and dietary adaptations in early hominins

Inference of feeding adaptation in extinct species is challenging, and reconstructions of the paleobiology of our ancestors have utilized an array of analytical approaches. Comparative anatomy and finite element analysis assist in bracketing the range of capabilities in taxa, while microwear and isotopic analyses give glimpses of individual behavior in the past. These myriad approaches have limitations, but each contributes incrementally toward the recognition of adaptation in the hominin fossil record. Microwear and stable isotope analysis together suggest that australopiths are not united by a single, increasingly specialized dietary adaptation. Their traditional (i.e., morphological) characterization as nutcrackers may only apply to a single taxon, Paranthropus robustus. These inferences can be rejected if interpretation of microwear and isotopic data can be shown to be misguided or altogether erroneous. Alternatively, if these sources of inference are valid, it merely indicates that there are phylogenetic and developmental constraints on morphology. Inherently, finite element analysis is limited in its ability to identify adaptation in paleobiological contexts. Its application to the hominin fossil record to date demonstrates only that under similar loading conditions, the form of the stress field in the australopith facial skeleton differs from that in living primates. This observation, by itself, does not reveal feeding adaptation. Ontogenetic studies indicate that functional and evolutionary adaptation need not be conceptually isolated phenomena. Such a perspective helps to inject consideration of mechanobiological principles of bone formation into paleontological inferences. Finite element analysis must employ such principles to become an effective research tool in this context.

A dental topographic analysis of chimpanzees

Molar tooth morphology is generally said to reflect a compromise between phylogenetic and functional influences. Chimpanzee subspecies have been reported to exhibit differences in molar dimensions and nonmetric traits, but these have not been related to differences in their diets. And in fact, observations to date of the diets of chimpanzees have not revealed consistent differences among subspecies. This study uses dental topographic analyses shown to reflect diet-related differences in occlusal morphology among primate species, to assess within-species variation among chimpanzee subspecies. High-resolution casts from museum collections were examined by laser scanning, and resulting data were analyzed using GIS algorithms and a two-factor ANOVA model. Although differences were noted between wear stages within subspecies in surface slope, relief, and angularity, none were found to distinguish the subspecies from one another in these attributes. This might reflect limitations in the ability of this method to detect diet-related differences, but is also consistent with a lack of differences in functionally relevant aspects of occlusal morphology among chimpanzee subspecies.

Are We Looking for Loads in All the Right Places? New Research Directions for Studying the Masticatory Apparatus of New World Monkeys

New World monkeys display a wide range of masticatory apparatus morphologies related to their diverse diets and feeding strategies. While primatologists have completed many studies of the platyrrhine masticatory apparatus, particularly morphometric analyses, we collectively acknowledge key shortcomings in our understanding of the function and evolution of the platyrrhine feeding apparatus. Our goal in this contribution is to review several recent, and in most cases ongoing, efforts to address some of the deficits in our knowledge of how the platyrrhine skull is loaded during feeding. We specifically consider three broad research areas: (1) in vivo physiological studies documenting mandibular bone strains during feeding, (2) metric analyses assessing musculoskeletal functional morphology and performance, as well as (3) the initiation of a physiological ecology of feeding that measures in vivo masticatory mechanics in a natural environment. We draw several conclusions from these brief reviews. First, we need better documentation of in vivo strain patterns in the platyrrhine skull during feeding given their empirical role in developing adaptive hypotheses explaining masticatory apparatus form. Second, the greater accuracy of new technologies, such as CT scanning, will allow us to better describe the functional consequences of jaw form. Third, performance studies are generally lacking for platyrrhine jaws, muscles, and teeth and offer exciting avenues for linking form to feeding behavior and diet. Finally, attempts to bridge distinct research agendas, such as collecting in vivo physiological data during feeding in natural environments, present some of the greatest opportunities for novel insights into platyrrhine feeding biology. Anat Rec, , 2011.