Early hominid diets from quantitative image analysis of dental microwear.
ABSTRACT The dietary habits of the early hominids Australopithecus and Paranthropus have long been debated. Robinson argued that the two species differed in the proportions of meat and vegetables consumed. More recently it has been suggested that Paranthropus, with its presumably larger body size, simply processed greater amounts of the same foods eaten by Australopithecus to maintain 'functional equivalence'. Microscopic dental wear patterns are related to the dietary habits of extant mammals, and quantification of these patterns is useful in distinguishing among primates with different diets. Nevertheless, few attempts have been made to use microwear in the reconstruction of early hominid diets, and only very recently has the quantification of such data been initiated. While microwear fabrics can be reduced to individual elements (for example, scratches and pits), there is some disagreement over exactly how they should be defined and measured. Fourier transforms have been applied successfully in the study of a variety of physical and biological patterns, and recently they have been used to characterize and distinguish different tooth wear patterns more objectively. Here we report the first combined use of image processing and other quantitative techniques to analyse the dental microwear of early hominids. Our results suggest that Paranthropus ate substantially more hard food items than Australopithecus.
Full-textDOI: · Available from: Richard F. Kay, Apr 18, 2015
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ABSTRACT: We hypothesize that microwear traces in natural tooth enamel can be simulated and quantified using microindentation mechanics. Microcontacts associated with particulates in the oral wear medium are modeled as sharp indenters with fixed semi-apical angle. Distinction is made between markings from static contacts ('pits') and translational contacts ('scratches'). Relations for the forces required to produce contacts of given dimensions are derived, with particle angularity and compliance specifically taken into account so as to distinguish between different abrasives in food sources. Images of patterns made on human enamel with sharp indenters in axial and sliding loading are correlated with theoretical predictions. Special attention is given to threshold conditions for transition from a microplasticity to a microcracking mode, corresponding to 'mild' and 'severe' wear domains. It is demonstrated that the typical microwear trace is generated at loads on the order of 1 N-i.e. much less than the forces exerted in normal biting-attesting to the susceptibility of teeth to wear in everyday mastication, especially in diets with sharp, hard, and large inclusive intrinsic or extraneous particulates. Copyright © 2014. Published by Elsevier Ltd.Acta Biomaterialia 12/2014; 14. DOI:10.1016/j.actbio.2014.11.047 · 5.68 Impact Factor
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ABSTRACT: 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.Journal of Human Evolution 10/2014; 78. DOI:10.1016/j.jhevol.2014.08.011 · 3.87 Impact Factor
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ABSTRACT: Evolution in isolated island has shaped a variety of endemic taxa with outstanding characteristics. Amongst them is the extinct bovid genus Myotragus, endemic to Mallorca and Menorca Island, for which six succeeding species have been described: M. palomboi, M. pepgonellae, M. antiquus, M. kopperi, M. batei and M. balearicus. Myotragus has developed special cranial and post-cranial adaptations to meet the specific ecological demands of its insular habitat, like progressive dwarfing and fused limb elements. During its evolution, the dentition of Myotragus underwent subsequent changes: firstly a reduction in the number of teeth, and secondly an increase in hypsodonty. The ecological conditions inducing this dental evolution, especially Myotragus’ diet, remain unknown. In this study, methods of 3D-dental topometry, enamel surface texture analysis according to ISO/FDIS 25178-2, and Scale-Sensitive Fractal Analysis (SSFA) are applied in order to infer palaeodiets of M. pepgonellae, M. kopperi, M. batei and M. balearicus, and to test the hypothesis that a dietary change may have occurred in the Myotragus lineage which relates to gradual morphological changes on upper second molars. We detect changes in the enamel/dentin ratio, enamel ridge length and enamel surface area within the lineage. Furthermore, Myotragus balearicus has enamel surface texture characteristics also present in extant browsing ungulates, while the three antecedent Myotragus species show an enamel surface texture signal similar to extant grazers. These results suggest a dietary change and are interpreted as a successive adaptation to limited resources in an isolated, insular environment. They can either be a consequence of a change in plant community structure or a successive expansion of Myotragus’ dietary range due to increased intraspecific competition.Geobios 01/2013; 46:143-150. DOI:10.1016/j.geobios.2012.10.010 · 1.01 Impact Factor