Dental macrowear and cortical bone thickness analyses of the Neanderthal mandible from Regourdou (Dordogne Southwestern France)

Tooth wear is one of the most studied features in archaeology and anthropology for reconstructing diet, food processing and cultural habits of ancient human populations and extinct human groups. In particular, occlusal wear facets (those areas visible macroscopically, and characterised by polished surfaces with well-delineated margins, that are created by the contact of opposing dental arches during mastication) can be extremely useful to detect information about diet and non-masticatory behaviours [1]. The aim of this study is to analyse the macrowear pattern of the complete Neanderthal mandible of Regourdou 1 (Dordogne, Southern France), using a sophisticated and well-established method known as Occlusal Fingerprint Analysis [2]. In addition, because asymmetric masticatory loads in the mandible could generate local variation in cortical bone thickness [3], we will explore whether there is any correlation between dental macrowear, cortical bone distribution and root dentine thickness in the mandible of Regourdou 1.
The anterior dentition of Regourdou 1 shows a more advanced degree of wear than the postcanine teeth, with large dentine exposure and rounded labial wear, a typical pattern found in many Neanderthal specimens. The posterior dentition is characterised by an asymmetric wear pattern, with the right side significantly more worn than the left half [4]. In contrast, the left lower P3 shows a more advanced degree of wear than the right premolar, with a mesio-distally elongated dentine exposure and semicircular enamel facets. The analysis of this unique pattern excludes the possibility that this type of wear is created by normal chewing behaviours, but it rather indicates tooth-tool uses for food processing and/or manufacturing of objects during daily task activities. The occlusal macrowear analysis also suggests that Regourdou 1 had a mixed-diet, typical of those populations living in temperate deciduous woodlands, with an intake of animal and plant foods [5].
Moreover, although there are no major differences in lingual cortical bone distribution between the left and right sides, the left buccal aspect of the mandible is substantially thicker than its right counterpart. Similarly, the virtual unrolled root of the left P3 has a thicker dentine layer than measured on the opposite right third premolar. These results show a certain degree of asymmetry in cortical bone topography and dentine tissue in Regourdou 1, that seems to be correlated with its dental macrowear pattern. Although this study is limited to one individual, future analyses based on a larger sample size may further assist us to better understand the existing relationship between mandibular architecture, occlusal wear and the masticatory system in humans.