Dental morphology and dental wear as ecological and alimentary indicatorssexual and intergroup variation in traditional human populations

Resumen

Sexual division of labour involving the use of teeth in non-masticatory activities in the Tigara population form Point Hope did not affect the wear of the upper and lower first molars and, therefore, food chewing was the main factor causing dental wear in this population. No sexual differences were found in the percentage of dentine exposure of the first molars, which is indicative that both sexes in the Tigara populations consumed very similar diets despite sex differences in the dental wear on the anterior dentition have been reported. The percentage of dentine exposure was positively correlated with the age group categories of the individual in the Tigara population, proving that dental wear is a cumulative process throughout lifespan. Crown relief of the first molars was negatively correlated with the percentage of dentine exposure, which shows that dental wear causes a decrease in cusp and crown heights. Crown relief is a continuous variable significantly correlated with age at death. Crown complexity, on the other hand, was greater in teeth with high levels of dentine exposure, showing that wear facets significantly contribute to food processing during mastication. No significant correlations were found between the percentage of dentine exposure and the density and average length of buccal scratches. However, a trend towards shorter scratches on buccal enamel surfaces was observed with decreasing values of crown relief, which demonstrates that the progressive accumulation of buccal scratches caused by enamel abrasion, which results in a reduction of their average length, is a parallel process with respect to the reduction of crown height. No significant differences on dentine exposure by sex were observed in any of the traditional modern human populations studied, which might be indicative that dental wear on molar teeth is not an adequate measure of the impact of sexual division of labour on the diet of both sexes. No significant differences in dental wear was found between the hunter-gatherer and agro-pastoral groups, despite they had very distinct diets and cultural practices in relation to food acquisition and processing. Such lack of significant wear differences among populations could be indicative that different diets may result in similar wear patterns and that the physical properties of chewed food particles might be more informative on dental wear processes than discrete classifications of dietary habits. First upper molar shape differences from all the modern human populations studied reflected the patterns of human migration and dispersal, although retaining a significant phylogenetic signal. The shape of the upper first molar in the Hutu population may be considered ancestral to the other groups compared that show a derived conditions consisting in more quadrangular and less oval shaped molars. Molar shape variability clearly discriminated the Sundadont and Sinodont populations. The Sinodont upper first molar would be characterized by more regular, rounded outlines, whereas the Sundadont would show more oval and irregular crown shapes.