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.     

Ecogeographic variation in Neandertal dietary habits: evidence from occlusal molar microwear texture analysis

In the late Middle and early Late Pleistocene, Neandertals inhabited a wide variety of ecological zones across western Eurasia during both glacial and interglacial times. To elucidate the still poorly understood effects of climatic change on Neandertal subsistence patterns, this study employs dental microwear texture analysis to reconstruct the diets of Neandertal individuals from various sites across their wide temporal and geographic ranges. The results of this study reveal environmentally-driven differences in the diets of Neandertal groups. Significant differences in microwear signatures, correlated with paleoecological conditions, were found among Neandertal groups that lived in open, mixed, and wooded environments. In comparison to recent hunter-gatherer populations with known, yet diverse diets, the occlusal molar microwear signatures of all the Neandertal groups indicate that their diet consisted predominantly of meat. However, the results of this study suggest that plant foods did form an important part of the diet of at least some Neandertal groups (i.e., those that lived in mixed and wooded habitats). Overall, the proportion of plant foods in the Neandertal diet appears to have increased with the increase in tree cover.     

In vivo and in vitro turnover in dental microwear

Given the potential usefulness of dental microwear analyses in interpretations of archaeological and paleontological material, it is surprising how little we know about changes in individual microwear features through time. The purpose of this study was to document the turnover in primate dental microwear through in vivo dental studies of monkeys raised on different diets, and through in vitro studies of the abrasive effects of monkey chow biscuits on isolated monkey teeth. As in previous studies, epoxy replicas were prepared from dental impressions and examined under a scanning electron microscope. Results indicate that, under certain conditions, the turnover in primate dental microwear can be on the order of days, hours, or even minutes. Individual microscopic wear features can be obliterated within 24 hours on the molars of laboratory monkeys, and monkey chow biscuits can easily scratch the enamel of isolated monkey teeth. Monkeys raised on a hard diet showed more rapid turnover in dental microwear than monkeys raised on a soft diet. However, paired-sample tests revealed that, for all animals, the molar shearing facets were being abraded at a significantly slower rate than molar crushing/grinding facets. In light of these results, investigators should make every effort to use large samples in interspecific comparisons of dental microwear involving species with variable diets. Another implication of these results is that changes in dental microwear might be useful indicators of changes in oral behavior over relatively short periods of time.     

Technical note: Dental microwear textures of "Phase I" and "Phase II" facets

The power stroke of mastication has been traditionally divided into two parts, one which precedes centric occlusion, and the other which follows it-"Phase I" and "Phase II," respectively. Recent studies of primate mastication have called into question the role of Phase II in food processing, as they have found little muscle activity or accompanying bone strain following centric occlusion. That said, many researchers today look to Phase II facets to relate diet to patterns of dental microwear. This suggests the need to reevaluate microwear patterns on Phase I facets. Here we use texture analysis to compare and contrast microwear on facets representing both phases in three primate species with differing diets (Alouatta palliata, Cebus apella, and Lophocebus albigena). Results reaffirm that microwear patterns on Phase II facets better distinguish taxa with differing diets than do those on Phase I facets. Further, differences in microwear textures between facet types for a given taxon may themselves reflect diet. Some possible explanations for differences in microwear textures between facet types are proposed.     

A study of microwear on chimpanzee molars: Implications for dental microwear analysis

Recent investigations of dental microwear have shown that such analyses may ultimately provide valuable information about the diets of fossil species. However, no background information about intraspecific variability of microwear patterns has been available until now. This study presents the results of an SEM survey of microwear patterns found on occlusal enamel of chimpanzee molars. Methods of pattern analysis are described. Selected sites on the occlusal surface included shearing, grinding, and puncture-crushing surfaces formed by both phases of the power stroke of mastication. The microwear patterns found in this sample of chimpanzees showed a high degree of regularity. However, certain parameters such as relative pit-to-striation frequencies, feature density, striation length, and pit diameter were significantly affected by facet type and molar position. Sex and age of individuals also influenced some microwear parameters, but due to the small sample size these findings are considered to be preliminary. These results show that microwear within a single species may vary because of factors that are due more to biomechanics than to diet. The study also supplies some metrical estimates of “normal” pattern variability due to functional and morphological influences. These estimates should provide a useful baseline for assessing the significance of microwear pattern differences that may be found between species of differing diets.     

Dental microwear texture analysis: technical considerations

Dental microwear analysis is commonly used to infer aspects of diet in extinct primates. Conventional methods of microwear analysis have usually been limited to two-dimensional imaging studies using a scanning electron microscope and the identification of apparent individual features. These methods have proved time-consuming and prone to subjectivity and observer error. Here we describe a new methodological approach to microwear: dental microwear texture analysis, based on three-dimensional surface measurements taken using white-light confocal microscopy and scale-sensitive fractal analysis. Surface parameters for complexity, scale of maximum complexity, anisotropy, heterogeneity, and textural fill volume offer repeatable, quantitative characterizations of three-dimensional surfaces, free of observer measurement error. Some results are presented to illustrate how these parameters distinguish extant primates with different diets. In this case, microwear surfaces of Cebus apella and Lophocebus albigena, which consume some harder food items, have higher average values for complexity than do folivores or soft fruit eaters.     

Molar microwear textures and the diets of Australopithecus anamensis and Australopithecus afarensis

Many researchers have suggested that Australopithecus anamensis and Australopithecus afarensis were among the earliest hominins to have diets that included hard, brittle items. Here we examine dental microwear textures of these hominins for evidence of this. The molars of three Au. anamensis and 19 Au. afarensis specimens examined preserve unobscured antemortem microwear. Microwear textures of these individuals closely resemble those of Paranthropus boisei, having lower complexity values than Australopithecus africanus and especially Paranthropus robustus. The microwear texture complexity values for Au. anamensis and Au. afarensis are similar to those of the grass-eating Theropithecus gelada and folivorous Alouatta palliata and Trachypithecus cristatus. This implies that these Au. anamensis and Au. afarensis individuals did not have diets dominated by hard, brittle foods shortly before their deaths. On the other hand, microwear texture anisotropy values for these taxa are lower on average than those of Theropithecus, Alouatta or Trachypithecus. This suggests that the fossil taxa did not have diets dominated by tough foods either, or if they did that directions of tooth–tooth movement were less constrained than in higher cusped and sharper crested extant primate grass eaters and folivores.     

牙齿微痕研究在古食性重建中应用的简述

在古食性研究中,牙齿微痕是指动物在咀嚼食物的过程中在牙齿咬合面上产生的微观磨损痕迹。不同食性的动物具有不同的牙齿微痕特征,因此可以通过研究牙齿微痕特征来重建灭绝动物的古食性,为探讨动物演化和古生态环境变化提供重要信息。本文主要介绍牙齿微痕作为一种简单而高效的古食性重建方法在古生物领域中的应用。本文主要内容包括牙齿微痕的发展历史,形成机理与应用,以及近年来被广泛应用的牙齿微痕定量化分析——表面纹理分析法,并在最后浅谈了牙齿微痕研究未来可能研究的方向。     

Buccal dental microwear variability in extant African Hominoidea: taxonomy versus ecology

Buccal microwear patterns on teeth are good indicators of the abrasiveness of foodstuffs and have been used to trace the dietary habits of fossil species, including primates and hominids. However, few studies have addressed the variability of this microwear. The abrasiveness of dietary components depends not only on the hardness of the particles ingested, but also on the presence of dust and other exogenous elements introduced during food processing. These elements are responsible for the microwear typology observed on the enamel surfaces of primate teeth. Here we analyzed the variability of buccal microwear patterns in African Great Apes (Gorilla gorilla and Pan troglodytes), using tooth molds obtained from the original specimens held in several osteological collections. Our results suggest that ecological adaptations at subspecies or population level account for differences in microwear patterns, which are attributed to habitat and ecological conditions within populations rather than differences between species. The findings from studies on the variability of buccal dental microwear in extant species will contribute to a better understanding of extinct hominids’ diet and ecology.     

Direct Comparisons of 2D and 3D Dental Microwear Proxies in Extant Herbivorous and Carnivorous Mammals

The analysis of dental microwear is commonly used by paleontologists and anthropologists to clarify the diets of extinct species, including herbivorous and carnivorous mammals. Currently, there are numerous methods employed to quantify dental microwear, varying in the types of microscopes used, magnifications, and the characterization of wear in both two dimensions and three dimensions. Results from dental microwear studies utilizing different methods are not directly comparable and human quantification of wear features (e.g., pits and scratches) introduces interobserver error, with higher error being produced by less experienced individuals. Dental microwear texture analysis (DMTA), which analyzes microwear features in three dimensions, alleviates some of the problems surrounding two-dimensional microwear methods by reducing observer bias. Here, we assess the accuracy and comparability within and between 2D and 3D dental microwear analyses in herbivorous and carnivorous mammals at the same magnification. Specifically, we compare observer-generated 2D microwear data from photosimulations of the identical scanned areas of DMTA in extant African bovids and carnivorans using a scanning white light confocal microscope at 100x magnification. Using this magnification, dental microwear features quantified in 2D were able to separate grazing and frugivorous bovids using scratch frequency; however, DMTA variables were better able to discriminate between disparate dietary niches in both carnivorous and herbivorous mammals. Further, results demonstrate significant interobserver differences in 2D microwear data, with the microwear index remaining the least variable between experienced observers, consistent with prior research. Overall, our results highlight the importance of reducing observer error and analyzing dental microwear in three dimensions in order to consistently interpret diets accurately.     

Technical note: Artificial Resynthesis Technology for the experimental formation of dental microwear textures

Dental microwear formation on the posterior dentition is largely attributed to an organism's diet. However, some have suggested that dietary and environmental abrasives contribute more to the formation process than food, calling into question the applicability of dental microwear to the reconstruction of diet in the fossil record. Creating microwear under controlled conditions would benefit this debate, but requires accurately replicating the oral environment. This study tests the applicability of Artificial Resynthesis Technology (ART 5) to create microwear textures while mitigating the challenges of past research. ART 5 is a simulator that replicates the chewing cycle, responds to changes in food texture, and simulates the actions of the oral cavity. Surgically extracted, occluding pairs of third molars (n = 2 pairs) were used in two chewing experiments: one with dried beef and another with sand added to the dried beef. High-resolution molds were taken at 0, 50, 100, 2500, and 5000 simulated chewing cycles, which equates to approximately 1 week of chewing. Preliminary results show that ART 5 produces microwear textures. Meat alone may produce enamel prism rod exposure at 5000 cycles, although attrition cannot be ruled out. Meat with sand accelerates the wear formation process, with enamel prism rods quickly obliterated and “pit-and-scratch” microwear forming at approximately 2500 cycles. Future work with ART 5 will incorporate a more thorough experimental protocol with improved controls, pH of the simulated oral environment, and grit measurements; however, these results indicate the potential of ART 5 in untangling the complex variables of dental microwear formation.     

Diet of upper paleolithic modern humans: Evidence from microwear texture analysis

This article presents the results of the occlusal molar microwear texture analysis of 32 adult Upper Paleolithic modern humans from a total of 21 European sites dating to marine isotope stages 3 and 2. The occlusal molar microwear textures of these specimens were analyzed with the aim of examining the effects of the climatic, as well as the cultural, changes on the diets of the Upper Paleolithic modern humans. The results of this analysis do not reveal any environmentally driven dietary shifts for the Upper Paleolithic hominins indicating that the climatic and their associated paleoecological changes did not force these humans to significantly alter their diets in order to survive. However, the microwear texture analysis does detect culturally related changes in the Upper Paleolithic humans' diets. Specifically, significant differences in diet were found between the earlier Upper Paleolithic individuals, i.e., those belonging to the Aurignacian and Gravettian contexts, and the later Magdalenian ones, such that the diet of the latter group was more varied and included more abrasive foods compared with those of the former. Am J Phys Anthropol 153:570–581, 2014. © 2014 Wiley Periodicals, Inc.     

Seasonal Mortality Patterns in Primates: Implications for the Interpretation of Dental Microwear

The microscopic traces of use wear on teeth have been extensively studied to provide information that will assist in elucidating the dietary habits of extinct hominin species. 1 - 13 It has been amply documented that dental microwear provides information pertaining to diet for living animals, where there is a strong and consistent association between dental microwear patterns and different types of foods that are chewed. The details of occlusal surface wear patterns are capable of distinguishing among diets when the constituent food items differ in their fracture properties. 14 - 20 For example, the microwear traces left on the teeth of mammals that crush hard, brittle foods such as nuts are generally dominated by pits, whereas traces left on the teeth of mammals that shear tough items such as leaves tend to be characterized by scratches. These microwear features result from and thus record actual chewing events. As such, microwear patterns are expected to be variably ephemeral, as individual features are worn away and replaced or overprinted by others as the tooth wears down in subsequent bouts of mastication. Indeed, it has been demonstrated, both in the laboratory and the wild, that short‐term dietary variation can result in the turnover of microwear. 17 , 21 - 23 Because occlusal microwear potentially reflects an individual's diet for a short time (days, weeks, or months, depending on the nature of the foods being masticated), tooth surfaces sampled at different times will display differences that relate to temporal (for example, seasonal) differences in diet. 24     

Quantitative differences in dental microwear between primate species with different diets and a comment on the presumed diet of Sivapithecus

Studies of dental microwear have been used to relate tooth form to function in a variety of recent and extinct mammals. Probably the most important aspect of microwear analysis is the possibility of using it to deduce the diet of extinct animals. Such deductions must be based on comparative studies of modern species with known diets, but to date, only qualitative studies have been attempted and all have been based on small samples. Here we report quantitative differences in dental microwear between primate species that are known to have different diets. Occlusal facets with different functions have previously been shown to exhibit different microwear patterns. However, the differences between facets of one species are shown to be far less than those between homologous facets of different species. Study of seven species of extant primates shows that enamel microwear can be used to distinguish between those with a mainly frugivorous diet and those with a mainly folivorous one. Microwear can also distinguish hard-object feeders from soft-fruit eaters. The microwear of Miocene Sivapithecus indicus cannot be distinguished statistically from that of the chimpanzee, but it is different from that of the other species. On this evidence S. indicus was not a hard-object feeder and the adaptive significance of its thick molar enamel is at present unknown.     

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. Am J Phys Anthropol 158:769–775, 2015. © 2015 Wiley Periodicals, Inc.     

Seeds,browse, and tooth wear: a sheep perspective

While grazing as a selective factor towards hypsodont dentition on mammals has gained a lot of attention, the importance of fruits and seeds as fallback resources for many browsing ungulates has caught much less attention. Controlled‐food experiments, by reducing the dietary range, allow for a direct quantification of the effect of each type of items separately on enamel abrasion. We present the results of a dental microwear texture analysis on 40 ewes clustered into four different controlled diets: clover alone, and then three diets composed of clover together with either barley, corn, or chestnuts. Among the seed‐eating groups, only the barley one shows higher complexity than the seed‐free group. Canonical discriminant analysis is successful at correctly classifying the majority of clover‐ and seed‐fed ewes. Although this study focuses on diets which all fall within a single dietary category (browse), the groups show variations in dental microwear textures in relation with the presence and the type of seeds. More than a matter of seed size and hardness, a high amount of kernels ingested per day is found to be correlated with high complexity on enamel molar facets. This highlights the high variability of the physical properties of the foods falling under the browsing umbrella.     

Deciduous dental microwear of prehistoric juveniles from the lower Illinois River valley

Scanning electron microscopy was used to study age-related changes in the dental microwear of 36 prehistoric juveniles ranging from 6 to 27 months of age. Juveniles from horticultural (Middle Woodland) and agricultural (Mississippian) groups were studied to allow an investigation of the impact of diet on deciduous microwear. Inclusion of both molars and incisors in the sample permitted identification of age at earliest appearance of wear and comparisons between the age-related microwear characterizing different tooth types. Data on feature frequency and enamel surface characteristics were analyzed. Microwear feature frequencies generally increase with age and/or exposure to wear. Enamel surface characteristics show consistent qualitative changes associated with both age and exposure to wear. Molars and incisors differ for such surface characteristics in a way that make biomechanical sense, given the relative bite forces characterizing these teeth. Dietary reconstruction based on deciduous microwear is complex because of the effects of both age and exposure to wear on feature frequencies and enamel surface characteristics. Nonetheless, the present analyses suggest that 1) diets differed for younger and older juveniles within each cultural group and 2) the Middle Woodland juvenile diet was both harder and more varied in physical consistency than the Mississippian juvenile diet.     

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.     

The Microflora and Concentrations of Volatile Fatty Acids in The Rumen of Cattle Fed on Single Component Rations

The composition of the rumen microflora and the volatile fatty acids were examined in cattle free-grazing on grass or stall-fed on hay, grass pellets, oats or dried beet pulp with molasses. Total and viable counts of anaerobic bacteria were highest on the grass feeding, but viable counts as a percentage of total counts were highest when oats or beet pulp with molasses were fed. Counts of cellulolytic bacteria were lowest on these latter 2 diets, and highest on grass or grass pellet diets. Studies of the anaerobic flora showed that the composition in animals fed on grass pellets resembled more that found in animals free-grazing on grass than in those fed on hay. Counts of aerotolerant bacteria were only a small percentage of the total count, but were highest on the hay diet. On this latter diet and on grass-feeding the streptococci (identified as Streptococcus bovis) were predominant, but contrary to expectation, streptococci were found only in small numbers on the oats diet, where coryneform rods were the major type present. Although a period of 4–6 weeks was allowed for the animals to adapt to the feeds, the 2 periods of feeding on oats and dried beet pulp with molasses markedly affected the composition of the rumen flora in the subsequent periods of feeding grass pellets and hay. Ruinen volatile fatty acid analysis showed a propionogenic effect of oats and the highest percentage of butyric acid when beet pulp with molasses was fed. The expected propionogenic effect of grass pellets was not observed.