Changing perspectives on early hominin diets.

It is axiomatic that knowledge of the diets of extinct hominin species is central to any understanding of their ecology and our evolution. The importance of diet in the paleontological realm has led to the employment of multiple approaches in its elucidation. Some of these have deep historical roots, while others are dependent upon more recent technical and methodological advances. Historically, studies of tooth size, shape, and structure have been the gold standard for reconstructing diet. They focus on species-level adaptations, and as such, they can set theoretical brackets for dietary capabilities within the context of specific evolutionary moments. Other methods (e.g., analyses of dental calculus, biogeochemistry, and dental microwear) have only been developed within the past few decades, but are now beginning to yield evidence of the actual foods consumed by individuals represented by fossil remains. Here we begin by looking at these more "direct" forms of evidence of diet before showing that, when used in conjunction with other techniques, these "multi-proxy" approaches can raise questions about traditional interpretations of early hominin diets and change the nature of paleobiological interpretations.

Stubby versus stabby: A preliminary analysis of canine microwear in primates: Implication for inferring ingestive behaviors.

Molar and incisor microwear reflect aspects of food choice and ingestive behaviors in living primates and have both been used to infer the same for fossil samples. Canine microwear, however, has received less attention, perhaps because of the prominent role canines play in social display and because they are used as weapons-while outside of a few specialized cases, their involvement in diet related behaviors has not been obvious. Here, we posit that microwear can also provide glimpses into canine tooth use in ingestion. Canines of Sumatran long-tailed macaques (Macaca fascicularis), agile gibbons (Hylobates agilis), lar gibbons (Hylobates lar), Thomas' leaf monkeys (Presbytis thomasi), and orangutans (Pongo abelii), and two African great apes, bonobos (Pan paniscus) and common chimpanzees (Pan troglodytes schweinfurthii), were considered. The labial tips of maxillary canine replicas were scanned using a white-light confocal profiler, and both feature and texture analyses were used to characterize microwear surface patterning. The taxa exhibited significant differences in canine microwear. In some cases, these were consistent with variation in reported anterior tooth use such that, for example, the orangutans, known to use their front teeth extensively in ingestion, had the highest median number of microwear features on their canines, whereas the gibbons, reported to use their front teeth infrequently in food acquisition, had the lowest.

Grit your teeth and chew your food: Implications of food material properties and abrasives for rates of dental microwear formation in laboratory Sapajus apella (Primates).

Dental microwear analysis has been employed in studies of a wide range of modern and fossil animals, yielding insights into the biology/ecology of those taxa. Some researchers have suggested that dental microwear patterns ultimately relate back to the material properties of the foods being consumed, whereas others have suggested that, because exogenous grit is harder than organic materials in food, grit should have an overwhelming impact on dental microwear patterns. To shed light on this issue, laboratory-based feeding experiments were conducted on tufted capuchin monkeys [Sapajus apella] with dental impressions taken before and after consumption of different artificial foods. The foods were (1) brittle custom-made biscuits laced with either of two differently-sized aluminum silicate abrasives, and (2) ductile custom-made "gummies" laced with either of the two same abrasives. In both cases, animals were allowed to feed on the foods for 36 hours before follow-up dental impressions were taken. Resultant casts were analyzed using a scanning electron microscope. We asked five questions: (1) would the animals consume different amounts of each food item, (2) what types of dental microwear would be formed, (3) would rates of dental microwear differ between the consumption of biscuits (i.e., brittle) versus gummies (i.e., ductile), (4) would rates of dental microwear differ between foods including larger- versus smaller-grained abrasives, and (5) would rates of dental microwear differ between molar shearing and crushing facets in the animals in these experiments? Results indicated that (1) fewer biscuits were consumed when laced with larger-grained abrasives (as opposed to smaller-grained abrasives), but no such difference was observed in the consumption of gummies, (2) in all cases, a variety of dental microwear features was formed, (3) rates of dental microwear were higher when biscuits versus gummies were consumed, (4) biscuits laced with larger-grained abrasives caused a higher percentage of new features per item consumed, and (5) the only difference between facets occurred with the processing of biscuits, where crushing facets showed a faster rate of wear than shearing facets. These findings suggest that the impact of exogenous grit on dental microwear is the result of a dynamic, complex interaction between (at the very least) grit size, food material properties, and time spent feeding - which is further evidence of the multifactorial nature of dental microwear formation.

Objective assessment of simulated non-carious cervical lesion by tridimensional digital scanning.

OBJECTIVE: To explore the use of 3D intraoral scanner/image analysis for the detection and monitoring of simulated non-carious cervical lesions (NCCLs) in vitro. MATERIALS AND METHODS: A total of 288 NCCLs of different severities and simulated using a laboratorial model associating toothbrush stiffness (soft, medium, and hard) and toothpaste abrasivity (low, medium, high, and negative control) were analyzed. Dental impressions were taken from specimens before and after 35K and 65K brushing strokes, and then scanned with a CEREC Omnicam scanner. 3D models were analyzed for volumetric tooth loss. 3D optical profilometry was considered as the gold standard. Data were analyzed using ANOVA and Fisher's PLSD tests (alpha = 0.05), and agreement between methods by using intraclass correlation coefficient. RESULTS: Toothbrushes of hard and mid stiffness caused higher tooth loss than soft when associated with the highest abrasive, at 35K and 65K strokes (p < 0.001). Variation in slurry abrasivity led to differences in tooth loss (with control < low < medium < high, p < 0.0001) after both 35K and 65K strokes, regardless of the type of toothbrush used, except at 35K, wherein control = low (p = 0.55). 35K strokes caused less tooth loss than 65K for all abrasive slurries (p < 0.0001) except controls. The intraclass correlation coefficient for agreement between the test and gold standard methods was 0.85. CONCLUSIONS: Analysis of 3D images from intraoral scanner could detect and monitor NCCL progression, although this ability was limited on incipient lesions. Overall good agreement was found between the test method and optical profilometry. CLINICAL RELEVANCE: The suggested method may be applicable to detect and monitor NCCLs clinically.

Dental microwear and Pliocene paleocommunity ecology of bovids, primates, rodents, and suids at Kanapoi.

Reconstructions of habitat at sites like Kanapoi are key to understanding the environmental circumstances in which hominins evolved during the early Pliocene. While Australopithecus anamensis shows evidence of terrestrial bipedality traditionally associated with a more open setting, its enamel has low δ13C values consistent with consumption of C3 foods, which predominate in wooded areas of tropical Africa. Habitat proxies, ranging from paleosols and their carbonates to associated herbivore fauna and their carbon isotope ratios, suggest a heterogeneous setting with both grass and woody plant components, though the proportions of each have been difficult to pin down. Here we bring dental microwear texture analysis of herbivorous fauna to bear on the issue. We present texture data for fossil bovids, primates, rodents, and suids (n = 107 individuals in total) from the hominin bearing deposits at Kanapoi, and interpret these in the light of closely related extant mammals with known differences in diet. The Kanapoi bovid results, for example, are similar to those for extant variable grazers or graze-browse intermediate taxa. The Kanapoi suid data vary by taxon, with one similar to the pattern of extant grazers and the other more closely resembling mixed feeders. The Kanapoi primates and rodents are more difficult to associate with a specific environment, though it seems that grass was likely a component in the diets of both. All taxa evince microwear texture patterns consistent with a mosaic of discrete microhabitats or a heterogeneous setting including both tree and grass components.

The dental microwear of hard-object feeding in laboratory Sapajus apella and its implications for dental microwear formation.

OBJECTIVES: This study seeks to determine if (a) consumption of hard food items or a mixture of food items leads to the formation of premolar or molar microwear in laboratory capuchin monkeys (Sapajus apella) in one feeding session and (b) rates of microwear formation are associated with the number of food items consumed. MATERIALS AND METHODS: Five adult male capuchins were used in two experiments, one where they were fed unshelled Brazil nuts, and the other where they were fed a mixture of food items. Dental impressions were taken before and after each feeding session. Epoxy casts made from those impressions then were used in SEM analyses of rates of microwear formation. Upper and lower premolars and molars were analyzed. Qualitative comparisons were made and Spearman's rank-order correlations used to examine the relationship between rates of microwear formation and number of Brazil nuts consumed. RESULTS: Premolars and molars generally showed new microwear in the form of pits and scratches. However, the incidence of those features was low (0-6%). Rates of microwear formation were highest during the consumption of Brazil nuts. DISCUSSION: Variations in the rate of microwear formation on the premolars likely reflected patterns of ingestion whereas consistency in the rate of microwear on the molars likely reflected patterns of chewing. While dental microwear formation seemed to be correlated with the number of hard objects consumed, rates did differ between individuals. Differences in results between the two experiments demonstrate some of the limitations in our knowledge of dental microwear formation.

Dental microwear of living Hadza foragers.

OBJECTIVES: Studies of dental microwear of bioarchaeological assemblages and extant mammals from museum collections show that surface texture can provide a valuable proxy for reconstructing diets of past peoples and extinct species. However, no study to date has focused on occlusal surface microwear textures of living hunter-gatherers. Here we present the first such study of the Hadza foragers of Tanzania. METHODS: We took high-resolution dental impressions of occlusal surfaces for a total of 43 molds representing 25 men and women, 1-3 samples each, at different times during the rainy and dry seasons. Dental replicas were prepared and scanned by confocal profilometry and standard microwear texture parameters were calculated. Central tendencies and dispersions of variable scores were compared by season and by sex. RESULTS: We found no differences between sexes or seasons in texture attribute central tendency, but some for dispersion. Females had notably low microwear texture dispersion in the dry season while males had higher dispersion in some attributes, particularly in the dry season. These differences seem to be driven primarily by low variance among females in the dry season. CONCLUSIONS: This study demonstrates microwear texture data can be generated for living foragers. Given caveats of small samples available and consideration of foraging groups in transition, this study hints at variation in microwear texture dispersion between sexes and seasons for the Hadza, suggesting that such analyses might be of value for assessing hunter-gatherer diet.

Technical note: Comparing dental topography software using platyrrhine molars.

OBJECTIVES: There remain many idiosyncrasies among the values calculated for varying dental topography metrics arising from differences in software preferences among research groups. The aim of this work is to compare and provide potential conversion formulae for dental topography metrics calculated using differing software platforms. METHODS: Three software packages: ArcGIS, Surfer Manipulator, and molaR were used to calculate orientation patch count rotated (OPCR), Dirichlet normal energy (DNE), occlusal relief (OR), slope (m), and angularity (a) on platyrrhine second upper molars. Values derived from the various software packages were compared for distributional consistency and correlation. Where appropriate, formulae for conversion between like measures calculated on different software platforms were developed. RESULTS: When compared with the same measurement across software, OPCR, OR, and slope were all highly correlated. However, only OR demonstrated distributional consistency (i.e., nearly consistent mean, median, max, and min). Slope and OPCR were both higher when calculated by molaR as compared to Surfer Manipulator and ArcGIS calculations, conversion formulae are provided for these measures. DNE is only weakly correlated with angularity; but is correlated with orientation patch count across taxa. DISCUSSION: We explore why there is variation in the dental topography values calculated among the various software packages. The conversion formulae provided in this work will make possible direct comparisons among studies conducted across multiple research groups.

Microwear textures of Australopithecus africanus and Paranthropus robustus molars in relation to paleoenvironment and diet.

The importance of diet in primate ecology has motivated the use of a variety of methods to reconstruct dietary habits of extinct hominin taxa. Dental microwear is one such approach that preserves evidence from consumed food items. This study is based on 44 specimens of Australopithecus africanus from Makapansgat and Sterkfontein, and 66 specimens of Paranthropus robustus from Swartkrans, Kromdraai and Drimolen. These samples enable examination of potential differences between the two assemblages of A. africanus, and among the various assemblages of P. robustus in relation to the paleoenvironmental reconstructions that have been proffered for each fossil site. Sixteen microwear texture variables were recorded for each specimen from digital elevation models generated using a white-light confocal profiler. Only two of these differ significantly between the Makapansgat and Sterkfontein samples of A. africanus. None of the microwear texture variables differs significantly among the samples of P. robustus. On the other hand, P. robustus has significantly higher values than A. africanus for 11 variables related to feature complexity, size, and depth; P. robustus exhibits rougher surfaces that comprise larger, deeper features. In contrast, A. africanus has smoother, simpler wear surfaces with smaller, shallower and more anisotropic features. As for possible habitat differences among the various sites, only a relatively small number of subtle differences are evident between the specimens of A. africanus from Makapansgat and Sterkfontein, and there are none among the specimens of P. robustus from various deposits. As such, it is reasonable to conclude that, while subtle differences in microwear textures may reflect differences in background habitats, the wear fabric differences between P. robustus and A. africanus are most reasonably interpreted as having been driven by dietary differences.

The diet of Australopithecus sediba.

Specimens of Australopithecus sediba from the site of Malapa, South Africa (dating from approximately 2 million years (Myr) ago) present a mix of primitive and derived traits that align the taxon with other Australopithecus species and with early Homo. Although much of the available cranial and postcranial material of Au. sediba has been described, its feeding ecology has not been investigated. Here we present results from the first extraction of plant phytoliths from dental calculus of an early hominin. We also consider stable carbon isotope and dental microwear texture data for Au. sediba in light of new palaeoenvironmental evidence. The two individuals examined consumed an almost exclusive C(3) diet that probably included harder foods, and both dicotyledons (for example, tree leaves, fruits, wood and bark) and monocotyledons (for example, grasses and sedges). Like Ardipithecus ramidus (approximately 4.4 Myr ago) and modern savanna chimpanzees, Au. sediba consumed C(3) foods in preference to widely available C(4) resources. The inferred consumption of C(3) monocotyledons, and wood or bark, increases the known variety of early hominin foods. The overall dietary pattern of these two individuals contrasts with available data for other hominins in the region and elsewhere.

Brief communication: Dental microwear and diet of Homo naledi.

OBJECTIVES: A recent study of dental chipping suggested that Homo naledi teeth were exposed to "acute trauma" on a regular basis during life, presumably from the consumption of grit-laden foods. This follows debate concerning the etiology of dental chips in South African hominin teeth that dates back more than half a century. Some have argued that antemortem chips result from consumption of hard foods, such as nuts and seeds or bone, whereas others have claimed that exogenous grit on roots and tubers are responsible. Here we examine the dental microwear textures of H. naledi, both to reconstruct aspects of diet of these hominins and to assess the possibility that hard foods (gritty or otherwise) are the culprits for the unusually high antemortem chip incidence reported. METHODS: We made high-resolution replicas of original molars and found that ten individuals preserve antemortem wear. These were scanned by white-light scanning confocal profilometry and analyzed using scale-sensitive fractal analysis. Resulting data were compared with those published for other fossil hominins and extant non-human primates. RESULTS: Our results indicate that H. naledi had complex microwear textures dominated by large, deep pits. The only known fossil hominin with higher average texture complexity is Paranthropus robustus, and the closest extant primates in a comparative baseline series appear to be the hard-object feeder, Cercocebus atys, and the eurytopic generalist, Papio ursinus. CONCLUSIONS: This study suggests that H. naledi likely consumed hard and abrasive foods, such as nuts or tubers, at least on occasion, and that these might well be responsible for the pattern of chipping observed on their teeth.

New model to explain tooth wear with implications for microwear formation and diet reconstruction.

Paleoanthropologists and vertebrate paleontologists have for decades debated the etiology of tooth wear and its implications for understanding the diets of human ancestors and other extinct mammals. The debate has recently taken a twist, calling into question the efficacy of dental microwear to reveal diet. Some argue that endogenous abrasives in plants (opal phytoliths) are too soft to abrade enamel, and that tooth wear is caused principally by exogenous quartz grit on food. If so, variation in microwear among fossil species may relate more to habitat than diet. This has important implications for paleobiologists because microwear is a common proxy for diets of fossil species. Here we reexamine the notion that particles softer than enamel (e.g., silica phytoliths) do not wear teeth. We scored human enamel using a microfabrication instrument fitted with soft particles (aluminum and brass spheres) and an atomic force microscope (AFM) fitted with silica particles under fixed normal loads, sliding speeds, and spans. Resulting damage was measured by AFM, and morphology and composition of debris were determined by scanning electron microscopy with energy-dispersive X-ray spectroscopy. Enamel chips removed from the surface demonstrate that softer particles produce wear under conditions mimicking chewing. Previous models posited that such particles rub enamel and create ridges alongside indentations without tissue removal. We propose that although these models hold for deformable metal surfaces, enamel works differently. Hydroxyapatite crystallites are "glued" together by proteins, and tissue removal requires only that contact pressure be sufficient to break the bonds holding enamel together.

Anterior dental microwear textures show habitat-driven variability in Neandertal behavior.

The causes of Neandertal anterior tooth wear patterns, including labial rounding, labial scratches, and differential anterior-posterior wear, have been debated for decades. The most common explanation is the "stuff-and-cut" hypothesis, which describes Neandertals clamping down on a piece of meat and slicing a portion close to their lips. "Stuff-and-cut" has been accepted as a general aspect of Neandertal behavior without fully assessing its variability. This study analyzes anterior dental microwear textures across habitats, locations, and time intervals to discern possible variation in Neandertal anterior tooth-use behavior. Forty-five Neandertals from 24 sites were analyzed, represented by high-resolution replicas of permanent anterior teeth. The labial surface was scanned for antemortem microwear using a white-light confocal profiler. The resultant 3D-point clouds, representing 204 × 276 µm for each specimen, were uploaded into SSFA software packages for texture characterization. Statistical analyses, including MANOVAs, ANOVAs, and pairwise comparisons, were completed on ranked microwear data. Neandertal descriptive statistics were also compared to 10 bioarchaeological samples of known or inferred dietary and behavioral regimes. The Neandertal sample varied significantly by habitat, suggesting this factor was a principal driving force for differences in Neandertal anterior tooth-use behaviors. The Neandertals from open habitats showed significantly lower anisotropy and higher textural fill volume than those inhabiting more closed, forested environments. The texture signature from the open-habitat Neandertals was most similar to that of the Ipiutak and Nunavut, who used their anterior teeth for intense clamping and grasping behaviors related to hide preparation. Those in more closed habitats were most similar to the Arikara, who did not participate in non-dietary behaviors. These Neandertal individuals had a broad range of texture values consistent with non-dietary and dietary behaviors, suggesting they varied more in anterior tooth-use behaviors and exploited a wider variety of plant and animal resources than did those from open habitats.

A molar microwear texture analysis of pitheciid primates.

Dental microwear textures have been examined for a broad range of extant primates to assess their efficacy for reconstructing diets of fossil species. To date though, no dental microwear texture data have been published for pitheciid molars, despite reported variation in degree of sclerocarpy and, by extension, the fracture properties of foods these platyrrhines eat. While all pitheciids eat hard or tough seeds, Chiropotes and Pithecia have been documented to consume more than Callicebus. In this study, we explored whether measures of molar microwear texture complexity discriminate taxa following variation in reliance upon seeds, and whether dispersion among variables is greatest in Callicebus, which has the most variable diet. Here we report results for a study of microwear textures on M2 "Phase II" facets of Ch. satanas (N = 14), P. irrorata (N = 8), and Ca. moloch (N = 24) from the Brazilian Amazon (Oriximina, UHE Samuel, and Taperinha, respectively). Textures examined using a scanning confocal profiler showed significant differences in central tendencies for three measures: mean dale area (Sda), anisotropy (Str), and heterogeneity (HAsfc9 ). Ten measures showed significant differences in dispersion, with Callicebus being significantly more variable in eight of those ten. These results demonstrate that the pitheciids with different morphological adaptations and dietary reliance on seeds differ in their dental microwear textures, though less than initially hypothesized. Measures of dispersion, especially, show potential for identifying dietary variability.

Mechanical food properties and dental topography differentiate three populations of Lemur catta in southwest Madagascar.

Determining the proximate causes of tooth wear remains a major focus of dental study. Here we compare the diets of three ring-tailed lemur (Lemur catta) populations and examine how different dietary components may contribute to patterns of wear-related tooth shape. Casts were made from dental impressions collected between 2003 and 2010 from lemurs in the gallery and spiny/mixed forests of the Bezá Mahafaly Special Reserve (BMSR; Parcels 1 and 2) and the spiny/mixed forests of Tsimanampesotse National Park (TNP), Madagascar. Tooth shape variables (occlusal relief and slope, angularity) were analyzed using dental topographic analysis. Focal observations and food mechanical properties (FMPs: toughness, hardness, elastic modulus) were conducted and tested, respectively, during wet and dry seasons from 2008 to 2012. We found that FMPs correlate with patterns of dental topography in these three populations. Specifically, food toughness and elastic modulus correlate with the dental variables, but hardness does not. Average food toughness and elastic modulus, but not hardness, are highest in BMSR Parcel 2, followed by BMSR Parcel 1 and TNP. Occlusal relief and slope, which serve as proxies for tooth wear, show the greatest wear in Parcel 2 and the least in TNP. Angularity is also more pronounced in TNP. Further, dental topographic patterns correspond to reliance on Tamarindus indica (tamarind) fruit. Both BMSR populations consume tamarind at high frequencies in the dry season, but the fruits are rare at TNP and only occasionally consumed. Thus, high seasonal tamarind consumption and its mechanical values help explain the low dental relief and slope among BMSR lemurs. By investigating the ecology of a single widespread species across a variety of habitats, we have been able to link specific components of diet to patterns of dental topography in this species. This provides a context for interpreting wear-related tooth shape changes more generally, illustrating that populations can develop different dental wear patterns resulting from a mix of intrinsic factors (thin enamel) and local conditions (food properties, frequency of consumption).

Canine and incisor microwear in pitheciids and Ateles reflects documented patterns of tooth use.

OBJECTIVES: Platyrrhine species differ in the extent to and the manner in which they use their incisors and canines during food ingestion. For example, Ateles uses its anterior teeth to process mechanically nondemanding soft fruits, while the sclerocarp-harvesting pitheciids rely extensively on these teeth to acquire and process more demanding foods. Pitheciids themselves vary in anterior tooth use, with the pitheciines (Cacajao, Chiropotes, and Pithecia) noted to use their robust canines in a variety of ways to predate seeds, while Callicebus, which rarely predates seeds, uses its incisors and exceptionally short canines to scrape tough mesocarp from fruits. To investigate the relationship between tooth use and dental wear, microwear textures were investigated for the anterior teeth of these five genera of platyrrhine primates. METHODS: Using a white light confocal microscope, 12 microwear texture attributes that reflect feature size, anisotropy, density, and complexity were recorded from high-resolution epoxy casts of the incisors and canines of adult wild-collected Brazilian specimens of Ateles, Callicebus, Cacajao, Chiropotes, and Pithecia. RESULTS: Pitheciine canines tend to have deep microwear features and complex, anisotropic microwear textures, while Ateles anterior teeth tend to have very small features, low feature density, and less complex and anisotropic surfaces. Callicebus incisor and canine microwear is generally intermediate in size and complexity between those extremes. CONCLUSIONS: These findings align with expectations from reported field observations of tooth use and illustrate the potential for using microwear texture analysis to infer patterns of anterior tooth use in extinct primates. Am J Phys Anthropol 161:6-25, 2016. © 2016 Wiley Periodicals, Inc.

Dental microwear profilometry of African non-cercopithecoid catarrhines of the Early Miocene.

The Early Miocene of Kenya has yielded the remains of many important stem catarrhine species that provide a glimpse of the East African primate radiation at a time of major faunal turnover. These taxa have been subject to innumerable studies, yet there is still no consensus on their dietary niches. Here we report results of an analysis of dental microwear textures of non-cercopithecoid catarrhines from the Early Miocene of Kenya. Scanning confocal profilometry of all available molar specimens with undamaged occlusal surfaces revealed 82 individuals with unobscured antemortem microwear, representing Dendropithecus, Micropithecus, Limnopithecus, Proconsul, and Rangwapithecus. Scale-sensitive fractal analysis was used to generate microwear texture attributes for each individual, and the fossil taxa were compared with each other using conservative non-parametric statistical tests. This study revealed no discernible variation in microwear texture among the fossil taxa, which is consistent with results from a previous feature-based microwear study using smaller samples. Our results suggest that, despite their morphological differences, these taxa likely often consumed foods with similar abrasive and fracture properties. However, statistical analyses of microwear texture data indicate differences between the Miocene fossil sample and several extant anthropoid primate genera. This suggests that the African non-cercopithecoid catarrhines included in our study, despite variations in tooth form, had generalist diets that were not yet specialized to the degree of many modern taxa.

Technical note: An in vitro study of dental microwear formation using the BITE Master II chewing machine.

Dental microwear has been used for decades to reconstruct the diets of fossil hominins and bioarchaeological populations. The basic theory has been that hard-brittle foods (e.g., nuts, bone) require crushing and leave pits as they are pressed between opposing cheek-tooth surfaces, whereas soft-tough foods (e.g., grass blades, meat) require shearing and leave scratches as they are dragged along opposing surfaces that slide past one another. However, recent studies have called into question the efficacy of microwear as an indicator of diet. One issue has been the limited number of in vitro studies providing empirical evidence for associations between microwear pattern and chewing behavior. We here describe a new study using a chewing simulator, the BITE Master II, to examine the effects of angle of approach between opposing teeth and food consistency on microwear surface texture. Results indicate that opposing teeth that approach one another: 1) perpendicular to the occlusal plane (crushing) result in pits; 2) parallel to the occlusal plane (shearing) result in striations in the direction of movement; and 3) oblique to the occlusal plane (45°) result in both striations and pits. Results further suggest that different food types and abrasive loads affect the propensity to accumulate microwear features independent of feature shapes.

Environmental perturbations can be detected through microwear texture analysis in two platyrrhine species from Brazilian Amazonia.

Recent dental microwear studies have shown that fossil species differ from one another in texture attributes-both in terms of central tendency and dispersion. Most comparative studies used to interpret these results have relied on poorly provenienced museum samples that are not well-suited to consideration of within species variation in diet. Here we present a study of two species of platyrrhine monkeys, Alouatta belzebul (n = 60) and Sapajus apella (n = 28) from Pará State in the Brazilian Amazon in order to assess effects of habitat variation on microwear (each species was sampled from forests that differ in the degree of disturbance from highly disturbed to minimally disturbed). Results indicate that microwear texture values vary between habitats-more for the capuchins than the howler monkeys. This is consistent with the notion that diets of the more folivorous A. belzebul are less affected by habitat disturbance than those of the more frugivorous S. apella. It also suggests that microwear holds the potential to reflect comparatively subtle differences in within-species variation in fossil taxa if sample size and control over paleohabitat allow.