Dental morphology and dental wear as dietary and ecological indicators: sexual and inter-group differences in traditional human populations

Abstract

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.

Los dientes constituyen un material de estudio multidisciplinar y son usados en varias áreas de la ciencia: odontología, anatomía comparativa, paleontología, paleoantropología, genética y ciencias forenses, entre otras. La presente tesis tiene como objetivo principal investigar la variabilidad dental en populaciones de humanos modernos desde una perspectiva multi-metodológica. El enfoque principal fue el desgaste dental, aunque también se analizaron otras características, como la variabilidad métrica, la forma dental, el microdesgaste, el relieve o la complejidad de la corona. Objetivos: Valorar si la división sexual del trabajo presente en los esquimales de Point Hope puede afectar al desgaste del primer molar; Analizar las correlaciones entre marcadores del macrodesgaste, microdesgaste, relieve y complejidad de la corona dental para explorar las diferentes líneas de estudio de la pérdida del esmalte y sus correlaciones; Investigar la posible influencia de la división sexual del trabajo sobre la dienta en diferentes poblaciones de cazadores-recolectores y agricultores; Analizar la forma de los primeros molares en varios grupos de poblaciones humanas modernas mediante la innovadora técnica de la morfología geométrica tridimensional. La investigación ha sido realizada únicamente con el material disponible en las colecciones dentales de la Universidad de Barcelona y la Universidad de Alicante. Se analizaron 251 primeros molares procedentes de 188 individuos de 9 poblaciones diferentes de humanas modernas (Agta, Aborígenes Australianos, Batéké-Balali, Esquimo, Hutu, Javaneses, Khoe, Navajo y San). Al examinar las posibles influencias de la división sexual del trabajo en la dieta en otras poblaciones de economía tradicional, no se ha encontrado tampoco diferencias significativas entre hombres y mujeres en ningún de los grupos analizados. Tampoco se han encontrado variaciones en el desgaste entre los patrones de subsistencia cazador-recolector y agricultor. El estudio de la forma dental muestra una importante variación de la forma del primer molar superior entre los grupos.