Dental microwear evidence for a dietary shift between two nonmaize-reliant prehistoric human populations from Indiana

Several recent studies have demonstrated the efficacy of dental microwear analysis (DMA) for dietary reconstruction among nonhuman primates, early hominids, and prehistoric humans. The current study seeks microwear evidence for a paleobotanically suggested change in the types of foods that were consumed by two temporally distinct populations of the North American eastern woodlands. This particular dietary shift between the Late Archaic and the Early/Middle Woodland periods did not include the introduction of maize or any other tropical cultigen. In contrast, most dietary reconstructions from this area have compared later populations that consumed tropical cultigens (such as maize) with those that did not. High-resolution casts of adult mandibular second molar protoconid phase II wear facets were viewed via a scanning electron microscope at 500x. Photomicrographs of the microwear features were analyzed with specialized software, Microware 2.2 (Ungar [1995] Scanning 17:57-59). Analysis of variance statistical tests were performed, with one variable requiring rank-transformation. A dietary transition is evidenced by a statistically significant increase in the mean number of pits and concomitant decreases in scratch width and scratch length from the Late Archaic to the Early/Middle Woodland. Overall, the diet became harder and less abrasive. The implication here is that dental microwear analysis is able to discern relatively subtle dietary transitions in human populations that may not be as readily accessible by other means of dietary reconstruction.     

Art and Territoriality in the Lower Pecos Archaic

Abstract

The approximate prehistoric territorial limits of an Archaic belief system in the lower Pecos area of Texas is hypothesized on the basis of the geographic distribution of a distinctive pictograph style. It is proposed that these rock art localities functioned as ritual sites for a group of Archaic bands who shared a common ideology.     

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.     

The Adaptive Technology of the Prehistoric Inhabitants of Southwest Texas

Abstract

A model of the middle Archaic adaptations in the lower Pecos River area of southwest Texas is presented. Working within excellent temporal and spatial frameworks and using the results of ethnobotanical, ethnozoological and dietary studies, the adaptive efficiency of the ancient technology is examined. A basically unchanged adaptive continuum prevailed in the area for approximately 8000 years. The conservatism and longevity seen in the adaptation centered significantly on the early and conti11ued exploitation of perennial desert succulents such as sotol, lechuguilla and yucca both as food and raw material sources.     

Effect of taphonomic processes on dental microwear

Taphonomic processes have the potential to affect microscopic wear on teeth and to modify the wear patterns so as to confound dietary reconstructions based on dental microwear which was formed during the lifetime of an animal. This study describes a series of experiments which were conducted to simulate various taphonomic agents and to record their effect on dental microwear. Three types of experiment were carried out in order to explain anomalous microscopic wear that had been found on the dentition of several hominoid specimens from the 15 M.a. site of Pasalar in Turkey. The effect of two different acids-citric and hydrochloric acid-on dental microwear was investigated. Modification to microscopic wear caused by alkali (carbonatite ash) was examined in the second set of experiments. Lastly, the effect of abrasion by three different size classes of sediment from the site of Pasalar-quartz pebbles (grain size varied from 2,000-11,000 microm), coarse sand (grain size ranged from 500-1,000 microm), and medium-sized sand (grain diameters were between 250 and 500 microm)-was investigated. Results confirm previous findings that the taphonomic modification of dental microwear is readily identifiable and causes the obliteration rather than secondary alteration of microwear features. The experiments show that both citric and hydrochloric acid affect dental microwear but to varying degrees, whereas alkali did not cause any modification of microscopic features. The different size classes of sediment also had different effects on the dental microwear. The largest size sediment (quartz pebbles) polished the enamel and removed finer microwear features. The coarse sand, however, did not have any effect on the microwear. The greatest amount of abrasion was caused by the smallest sediment particles -the medium-sized sand. Several hominoid dental specimens from Pasalar display similar microscopic wear to the two types of acid erosion and the abrasion caused by the medium-sized sands.     

A Clay Figurine Cache From The Lower Pecos Region,Texas

Abstract

A cache of four clay figurines from a large rockshelter in the Lower Pecos region in Val Verde County, Texas, is described. A tentative date range of 2000 to 1200 B.C., which is within the Middle Archaic period of the local chronology, is proposed for the cache on the basis of artifact associations.     

植食性哺乳动物牙齿磨痕分析方法简介及其在古食性恢复中的应用前景

通过研究古哺乳动物的食性来探讨哺乳动物演化与古生态环境变化之间的关系是目前古生物学研究领域的一个热点,而牙齿磨痕分析是恢复古食性和重建古生态环境的重要手段。牙齿磨痕(dental wear)分析包括微痕(microwear)分析和中痕(mesowear)分析,两种方法均强调食性与牙齿磨痕模式的严格对应,即不同食性的动物具有不同的牙齿磨痕特征模式。近年来,牙齿磨痕分析方法以其简单、快捷和高效等优点已被广泛应用于奇蹄类、偶蹄类、啮齿类、长鼻类和食肉类等哺乳动物的食性研究。但哺乳动物的食性和摄食习性比较复杂,很可能会影响微痕和中痕分析对食性的分辨率。所以,为了获得更加详细的古食性信息和更高的食性分辨率,一方面要对微痕和中痕分析方法进行改进,增添稳定并具有食性识别意义的观测变量,另一方面,需要同时结合微痕和中痕分析,从而获得更加全面的食性信息。虽然牙齿磨痕分析目前主要应用于植食性哺乳动物的食性研究,但其原理对哺乳动物的其它类群也是适用的,随着磨痕分析方法的不断改进和其它类群磨痕数据库的建立,未来的牙齿磨痕分析将可以恢复更多类群的古食性,从而可以更加全面和准确地揭示古食性与古环境信息。     

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     

Dental microwear and diet in Venezuelan primates.

Recent microwear analyses have demonstrated that wear patterns can be correlated with dietary differences. However, much of this work has been based on analyses of museum material where dates and locations of collection are not well known. In view of these difficulties, it would be desirable to compare microwear patterns for different genera collected from the same area at the same time. The opportunity to do this was provided by the collections of the Smithsonian Venezuelan Project (Handley, 1976), in which multiple primate genera were collected from the same humid tropical forest sites within the same month. The monkeys represent a wide range of dietary preferences, and include Saimiri, Cebus, Chiropotes, Ateles, Aotus, Pithecia, and Alouatta. As in previous microwear analyses, epoxy replicas were prepared from dental impressions, as described by Rose (1983) and Teaford and Oyen (1989). Two micrographs were taken of facet 9 on an upper second molar of each specimen. Computations and analyses were the same as described by Teaford and Robinson (1989). Results reaffirm previously documented differences in dental microwear between primates that feed on hard objects versus those that do not--with Pithecia and Alouatta at the extremes of a range of microwear patterns including more subtle differences between species with intermediate diets. The subtle microwear differences are by no means easy to document in museum samples. However, additional results suggest that 1) the width of microscopic scratches may be a poor indicator of dietary differences, 2) large and small pits may be formed differently, and 3) there are very few seasonal differences in dental microwear in the primates at these humid tropical forest sites.     

Palaeoecology of cave bears as evidenced by dental wear analysis: a review of methods and recent findings

Abstract

The study of dental wear was first used years ago to infer the palaeoecology of fossil mammals and in particular their diet. Results depend predominantly on the scale of the analysis used. Analyses of dental macrowear, mesowear or microwear do not provide the same type of dietary information, be it about the seasonal, annual or lifetime diet. This contribution focuses on emblematic species, cave bears (Ursidae), in particular Ursus spelaeus spelaeus. Methods used by previous researchers to infer their dietary preferences and thus their palaeoecology are reviewed and compared. This review is complemented by an analysis of several specimens of cave bears from the Goyet cave in Belgium, using dental microwear texture analysis (DMTA), a methodology widely applied for reconstructing palaeodiets. Three main conclusions are drawn here: (1) DMTA is the method that provides the most precise palaeobiological inferences; (2) during the pre-dormancy period, cave bears show dietary flexibility; (3) dental wear alone might be not sufficient to provide a complete reconstruction of the cave bear palaeodiet.     

Do mandibular cross‐sectional properties and dental microwear give similar dietary signals?

Previous animal experimental work evaluating the effects of dietary consistency on mastication was generally limited to studies of either mandibular structure or rates and types of tooth wear. Control groups fed hard diets (HD) consistently exhibited increased cortical remodeling and/or bone strength when compared to groups fed soft diets (SD). Results of tooth-wear studies showed faster rates of tooth wear in HD animals. This study evaluates the effects of dietary differences on both mandibular structural morphology and postcanine dental microwear in the same animals. We examined mandibles and dentitions from eight miniature swine, raised from 4 weeks to 9 months of age on HD and SD (n = 4, each group). Mandibular structural properties were calculated from peripheral quantitative computed tomography slices at the dp3-dp4 and dp4-M1 junctions. Dental microwear analysis was performed on mandibular lingual crushing facets of dp4 and M1, using photomicrographs of high-resolution casts taken at 500x magnification in a scanning electron microscope. Our results suggest that between the dp3-dp4 contact, HD animals have mandibles that are stronger and more rigid mediolaterally than SD animals. At the dp4-M1 contact, HD animals have mandibles that are stronger and more rigid mediolaterally, dorsoventrally, and in torsion than SD animals. Dental microwear results indicate that SD pigs have higher incidences of pitting and more overall microwear features on their premolars than do HD pigs, yet there are no significant differences in molar microwear morphology between the dietary groups. Near-significant correlations exist between pit size and dorsoventral bending strength, but only for HD pigs. These results suggest that dietary consistency significantly affects both mandibular structure and dental microwear, yet direct correlations between the two are complicated by a number of factors.     

Dental microwear variability on buccal tooth enamel surfaces of extant Catarrhini and the Miocene fossil Dryopithecus laietanus (Hominoidea)

Analyses of buccal tooth microwear have been used to trace dietary habits of modern hunter-gatherer populations. In these populations, the average density and length of striations on the buccal surfaces of teeth are significantly cor-related with the abrasive potential of food items consumed. In non-human pri-mates, tooth microwear patterns on both occlusal and buccal wear facets have been thoroughly studied and the results applied to the characterization of dietary habits of fossil species. In this paper, we present inter- and intra-specific buccal microwear variability analyses in extant Cercopithecoidea (Cercopithecus mitis, C. neglectus, Chlorocebus aethiops, Colobus spp., Papio anubis) and Hominoidea (Gorilla gorilla, Pan troglodytes, Pongo pygmaeus). The results are tentatively compared to buccal microwear patterns of the Miocene fossils Dryopithecus and Oreopithecus. Significant differences in striation density and length are found among the fossil taxa studied and the extant primates, suggesting that buccal microwear can be used to identify dietary differences among taxa. The Dryopithecus buccal microwear pattern most closely resembles that of abrasive, tough plant foods consumers, such as the gorilla, in contrast to stud-ies of dental morphology that suggest a softer, frugivorous diet. Results for Oreopithecus were equivocal, but suggest a more abrasive diet than that previously thought.     

True grit: A microwear experiment

Recently we noted the effects of experimental diets on microscopic dental wear in the American opossum and concluded that it might prove difficult to distinguish the microwear produced by an insectivorous diet from that produced by some kinds of herbivorous ones. We also noted that wear caused by gritty diets and those containing plant opal, although they might be confused with one another, are easily distinguished from other sorts of dietary wear. Our conclusions have been challenged on the basis that possibly we did not allow sufficient time in the experiments for diagnostic wear patterns to emerge. Additional data reported here show that this is not so. Even in our n “control” animals, fed a relatively soft unabrasive diet, enough time elapsed to produce significant dental wear. A new technique is described which for the first time allows the study of changing patterns of microscopic wear in a living animal over a period of time, thus allowing each animal to serve as its own control. A solution containing a broad-spectrum proteolytic enzyme when applied to the teeth of an anesthetized animal removes the proteinaceous coat (pellicle) which will otherwise obscure wear scratches. Precision dental impressions can then be made which reveal the details of the pattern of microwear on the teeth.     

Phylogenetic signal in tooth wear dietary niche proxies

In the absence of independent observational data, ecologists and paleoecologists use proxies for the Eltonian niches of species (i.e., the resource or dietary axes of the niche). Some dietary proxies exploit the fact that mammalian teeth experience wear during mastication, due to both tooth‐on‐tooth and food‐on‐tooth interactions. The distribution and types of wear detectible at micro‐ and macroscales are highly correlated with the resource preferences of individuals and, in turn, species. Because methods that quantify the distribution of tooth wear (i.e., analytical tooth wear methods) do so by direct observation of facets and marks on the teeth of individual animals, dietary inferences derived from them are thought to be independent of the clade to which individuals belong. However, an assumption of clade or phylogenetic independence when making species‐level dietary inferences may be misleading if phylogenetic niche conservatism is widespread among mammals. Herein, we test for phylogenetic signal in data from numerous analytical tooth wear studies, incorporating macrowear (i.e., mesowear) and microwear (i.e., low‐magnification microwear and dental microwear texture analysis). Using two measures of phylogenetic signal, heritability (H²) and Pagel's λ, we find that analytical tooth wear data are not independent of phylogeny and failing to account for such nonindependence leads to overestimation of discriminability among species with different dietary preferences. We suggest that morphological traits inherited from ancestral clades (e.g., tooth shape) influence the ways in which the teeth wear during mastication and constrain the foods individuals of a species can effectively exploit. We do not suggest that tooth wear is simply phylogeny in disguise; the tooth wear of individuals and species likely varies within some range that is set by morphological constraints. We therefore recommend the use of phylogenetic comparative methods in studies of mammalian tooth wear, whenever possible.     

On the relationship of dental microwear to dental macrowear

Dental microwear analysts have demonstrated that hard diets leave numerous microscopic pits on occlusal surfaces. The relationship between occlusal pitting and gross macrowear, however, is not well known. The current study seeks to elucidate the relationship between dental microwear and macrowear by determining if microscopically pitted teeth are associated with greater expressions of macrowear. This study examined microwear and macrowear on mandibular second molars from 60 prehistoric adult Native Americans representing three dietary regimes (foraging, mixed economy, and agriculture). Initially, two dental microwear feature variables were studied: percentage of pits and mean scratch width. Standard macrowear scores ranged from 4 to 40. ANOVAs suggested that neither of the microwear variables was affected by age or sex, but age affected macrowear scores. Because of this, the sample had a balanced number of young and old adults (i.e., those below and above skeletal age 35). A Pearson's correlation showed no covariation between scratch width and the percentage of pits. Regression analysis indicated that macrowear was not a function of the percentage of pits. However, a significant positive relationship was found between dental macrowear and scratch width. A post priori test found a significant negative relationship between macrowear and the total number of scratches. It is concluded, then, that wide scratches remove more enamel and dentin than do numerous pits, although both cause dental wear. It is suggested here that the term “abrasive” be used to describe those microwear profiles that lead to heavy macrowear and have relatively wide scratches. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.     

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.     

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.     

Enamel structure and microwear: an experimental study of the response of enamel to shearing force.

The anisotropic fracturing and differential wear properties of enamel microstructure represent factors that can obscure the predictive relationship between dental microwear and diet. To assess the impact of enamel structure on microwear, this in vitro experimental study examines the relative contributions to wear of three factors: 1) species differences in microstructure, 2) direction of shearing force relative to enamel prisms and crystallites, and 3) size of abrasive particles. Teeth of Lemur, Ovis, Homo, and Crocodylus, representing, respectively, the structural categories of prismatic patterns 1, 2, and 3 and nonprismatic enamel, were abraded by shearing forces (forces having a component directed parallel to abraded surfaces) and examined by scanning electron microscopy. Striation width increased with particle size for nonprismatic, but not for prismatic, specimens. Direction of shear relative to prism and crystallite orientation had a significant influence on striation width in only some prismatic enamels. The different responses of prismatic and nonprismatic enamels to abrasion reflect the influence of structure, but at the level of organization of crystallites rather than prisms per se. Such interactions explain in part the inability of striation width to discriminate among animals with different dietary habits. Heteroscedasticity and deviations from normality also may confound parametric analyses of microwear variables. Variation in crystallite orientation in prismatic enamels may contribute to optimal dental function through the property of differential wear in functionally distinct regions of teeth.     

Preliminary examination of non-occlusal dental microwear in anthropoids: Implications for the study of fossil primates

Most studies of microscopic wear on non-human primate teeth have focused on the occlusal surfaces of molars. Recent analyses of the buccal surfaces of human cheek teeth have demonstrated an association between diet and dental microwear on the these surfaces as well. In the current study, we examine microwear on both the buccal and lingual surfaces of non-human primate molars to assess the potential of these surfaces to reveal information concerning anthropoid feeding behaviors. We compare frequency of microwear occurrence in 12 extant and 11 fossil anthropoid species. Among the living primates, the occurrence of microwear on non-occlusal surfaces appears to relate to both diet and degree of terrestriality. The implications of this research for the inference of feeding behaviors and substrate use in fossil cercopithecoids are discussed. © 1996 Wiley-Liss, Inc.     

Medicago truncatula-derived calcium oxalate crystals have a negative impact on chewing insect performance via their physical properties

Plant structural traits often act as defenses against herbivorous insects, causing them to avoid feeding on a given plant or tissue. Mineral crystals of calcium oxalate in Medicago truncatula Gaertn. (Fabaceae) leaves have previously been shown to be effective deterrents of lepidopteran insect feeding. They are also inhibitors of conversion of plant material into insect body mass during or after consumption. Growth of beet armyworm, Spodoptera exigua Hübner (Lepidoptera: Noctuidae), larvae was correspondingly greater on calcium oxalate‐defective (cod) mutants of M. truncatula with lower levels of crystal accumulation. Data presented here show that insects feeding on M. truncatula leaves with calcium oxalate crystals experience greater negative effects on growth and mandible wear than those feeding on artificial diet amended with smaller amorphous crystals from commercial preparations. Commercial calcium oxalate can be added to insect artificial diet at levels up to 7.5‐fold higher than levels found in wild‐type M. truncatula leaves with minimal effect on insect growth or lepidopteran mandibles. These data suggest that negative impacts of calcium oxalate in the diet of larvae are due to physical factors, and not toxicity of the compound, as high levels of the commercial crystals are readily tolerated. In contrast to the dramatic physical effects that M. truncatula‐derived crystals have on insect mandibles, we could detect no damage to insect peritrophic gut membranes due to consumption of these crystals. Taken together, the data indicate that the size and shape of prismatic M. truncatula oxalate crystals are important factors in determining effects on insect growth. If manipulation of calcium oxalate is to be used in developing improved insect resistance in plants, then our findings suggest that controlling not only the overall amount, but also the size and shape of crystals, could be valuable traits in selecting desirable plant lines.