La réduction des dents humaines à la transition Pléistocène-Holocène dans le sud-ouest de la France : réévaluation et apports de l’analyse de la structure interne par imagerie 3D

Une réduction de la taille des dents humaines et une simplification de leur forme ont été observées en Europe et débattues en lien avec des changements culturels et environnementaux de la fin du Pléistocène et du début de l’Holocène. Entre autres facteurs, les techniques de cuisson ou la pression démographique ont été proposées comme causes de ces modifications biologiques. Cependant, ces modèles sont toujours débattus et les mécanismes qui ont contribué à la réduction des couronnes ne sont pas entièrement compris à ce jour. Grâce à de nouvelles découvertes et la révision des contextes chronologiques et archéologiques de certains gisements du sud-ouest de la France, une réévaluation la nature des variations des dimensions dentaires a été effectuée pour les individus datés du Magdalénien supérieur, de l’Azilien et du Mésolithique ancien. Des acquisitions microtomographiques d’une partie de l’échantillon ont été réalisées afin de caractériser de manière non invasive la structure interne des dents (épaisseur de l’émail, proportions des tissus dentaires). Si une réduction globale des dimensions dentaires est constatée pour tous les types de dents, elle est plus marquée entre l’Azilien et le Mésolithique ancien. Cette réduction est principalement liée aux changements de volume et d’épaisseur de l’émail, paramètre plastique et écosensible témoignant de variations dans la biomécanique de la mastication. Ces résultats soulignent l’impact des changements environnementaux et culturels du début de l’Holocène. Une révision des modèles impliqués dans ce phénomène de réduction dentaire est proposée. Ainsi, cette approche intégrée, combinant les aspects externe et interne des dents, a permis de dégager des facteurs potentiellement responsables de la variation dentaire observée à la transition Pléistocène-Holocène

Évolution dentaire dans les populations humaines de la fin du Pléistocène et du début de l’Holocène (19000 – 5500 cal. BP) : une approche intégrée des structures externe et interne des couronnes pour le Bassin aquitain et ses marges / Dental evolution in Late Pleistocene and Early Holocene human populations (19000 – 5500 cal. BP) : a whole crown perspective in the Aquitaine Basin, southwest France, and its margins

Since the Late Pleistocene, a reduction in size and a morphological simplification of human teeth have been observed and arguably linked to cultural and environmental changes. Following new discoveries along with the revision of key archaeological contexts, a re-assessment of the nature of crown variations on more than 1900 teeth is proposed for 176 Late Paleolithic, Mesolithic and Early Neolithic individuals from the Aquitaine Basin and its margins. In particular, a non-invasive assessment of internal tooth structure variability (enamel thickness, dental tissue proportions, enamel-dentine junction morphology) has been performed using 3D imaging methods (microtomography) and geometric morphometrics in order to characterize and interpret dental evolution from a whole crown perspective. Results from the morphometric analyses show a discontinuity between Late Pleistocene and Early Holocene populations. External dimensions, enamel thicknesses and tissue proportions are reduced in Mesolithic individuals compared to those of the Late Paleolithic, while major differences are observed in occlusal wear patterns and enamel distribution between Mesolithic and Early Neolithic samples. These data suggest that environmentally-driven modifications during the Early Holocene had a major impact on dental reduction in human populations and that Neolithic cultural changes had mostly affected enamel distribution. Finally, a correlation between occlusal wear pattern and enamel thickness distribution is observed and associated with dietary changes. In particular, enamel thickness may have rapidly evolved as a selective response to functional changes in masticatory biomechanics

Microevolution of outer and inner structures of upper molars in Late Pleistocene and Early Holocene humans

In this study, we investigate outer and inner variations of upper second molars (UM2) for Late Pleistocene and Early Holocene modern humans, at a key-period in our evolutionary history associated with major sociocultural, economic and environmental changes. Non-metric traits have been recorded on 89 UM2 of 66 Upper Paleolithic, Mesolithic and Neolithic individuals, and 40 UM2 have been microscanned to assess variations in enamel thickness (ET) distribution and enamel-dentine junction (EDJ) shape. Major changes are found between Mesolithic and Neolithic periods: a decrease of the metacone expression combined with an increase of the hypocone development; an increase of the heterogeneity of ET distribution between lingual and buccal cusps; and an increase of the development of the dentine horn tips corresponding to the hypocone and, to a lesser extent, to the metacone. These morphological modifications could be linked to the masticatory functional changes associated with the transition to agriculture

3D models related to the publication: Internal tooth structure and burial practices: insights into the Neolithic necropolis of Gurgy (France, 5100-4000 cal. BC)

The present 3D Dataset contains the 3D models of external and internal aspects of human upper permanent second molars from the Neolithic necropolis analyzed in the following publication: Le Luyer M., Coquerelle M., Rottier S., Bayle P.: Internal tooth structure and burial practices: insights into the Neolithic necropolis of Gurgy (France, 5100-4000 cal. BC)

Au-delà de l’apport nutritionnel : l’analyse combinée de la macro-/micro-usure dentaire et des isotopes stables révèle des comportements alimentaires néo-lithiques genrés

L’approche structurale des ensembles funéraire Cerny (Ve millénaire BC, Bassin parisien) conduit à distinguer différentes catégories de défunts, notamment liées au sexe. Dans ce contexte économique agro-pastoral, l’accent mis sur la figure masculine du « chasseur » (hommes accompagnés de flèches) pose la question du lien entre statut funéraire, identité sexuelle et alimentation. Afin d’obtenir une vision la plus complète possible des comportements alimentaires Cerny, nous combinons ici l’étud..

Altérations taphonomiques et micro-usures dentaires : impact sur la caractérisation des régimes alimentaires

L’étude de la micro-usure dentaire participe à la reconstruction des comportements alimentaires des populations du passé, humaines et animales. En contexte archéologique et paléontologique, les processus taphonomiques peuvent influencer la qualité des surfaces dentaires et entraîner la réduction du nombre d’échantillons observables. Ceci est particulièrement notable dans notre corpus de 19 molaires humaines Cerny (Néolithique, Bassin parisien), où 7 dents présentent des altérations réparties ..

Is the deciduous/permanent molar enamel thickness ratio a taxon-specific indicator in extant and extinct hominids?

In Primates, enamel thickness variation stems from an evolutionary interplay between functional/adaptive constraints (ecology) and the strict control mechanisms of the morphogenetic program. Most studies on primate enamel thickness have primarily considered the permanent teeth, while the extent of covariation in tooth enamel thickness distribution between deciduous and permanent counterparts remains poorly investigated. In this test study on nine extant and fossil hominids we investigated the degree of covariation in enamel proportions between 25 pairs of mandibular dm2 and M1 by a so-called “lateral enamel thickness diphyodontic index”. The results did not provide an unambiguous picture, but rather suggest complex patterns likely resulting from the influence of many interactive factors. Future research should test the congruence of the “diphyodontic signal” between the anterior and the postcanine dentition, as well as between enamel and the enamel-dentine junction topography

A Neanderthal from the Central Western Zagros, Iran. Structural reassessment of the Wezmeh 1 maxillary premolar

Wezmeh Cave, in the Kermanshah region of Central Western Zagros, Iran, produced a Late Pleistocene faunal assemblage rich in carnivorans along with a human right maxillary premolar, Wezmeh 1, an unerupted tooth from an 8 ± 2 year-old individual. Uranium-series analyses of the fauna by alpha spectrometry provided age estimates between 70 and 11 ka. Crown dimensions place the tooth specimen at the upper limits of Late Pleistocene human ranges of variation. Wezmeh 1 metameric position (most likely a P3) remains uncertain and only its surficial morphology has been described so far. Accordingly, we used micro-focus X-ray tomography (12.5 μm isotropic voxel size) to reassess the metameric position and taxonomic attribution of this specimen. We investigated its endostructural features and quantified crown tissue proportions. Topographic maps of enamel thickness (ET) distribution were also generated, and semilandmark-based geometric morphometric analyses of the enamel-dentine junction (EDJ) were performed. We compared Wezmeh 1 with unworn/slightly-moderately worn P3 and P4 of European Neanderthals, Middle Paleolithic modern humans from Qafzeh, an Upper Paleolithic premolar, and Holocene humans. The results confirm that Wezmeh 1 represents a P3. Based on its internal conformation and especially EDJ shape, Wezmeh 1 aligns closely with Neanderthals and is distinct from the fossil and extant modern human pattern of our comparative samples. Wezmeh 1 is thus the first direct evidence of Neanderthal presence on the western margin of the Iranian Plateau

Evaluation of age, sex, and ancestry-related variation in cortical bone and dentine volumes in modern humans, and a preliminary assessment of cortical bone-dentine covariation in later Homo.

Cortical bone and dentine share similarities in their embryological origin, development, and genetic background. Few analyses have combined the study of cortical bone and dentine to quantify their covariation relative to endogenous and exogenous factors. However, knowing how these tissues relate in individuals is of great importance to decipher the factors acting on their evolution, and ultimately to understand the mechanisms responsible for the different patterns of tissue proportions shown in hominins. The aims of this study are to examine age-, sex-, and ancestry-related variation in cortical bone and dentine volumes, and to preliminary assess the possible covariation between these tissues in modern humans and in five composite Neandertals. The modern analytical sample includes 12 immature individuals from France and 49 adults from France and South Africa. Three-dimensional tissue proportions were assessed from microtomographic records of radii and permanent maxillary canines. Results suggest ontogenic differences and a strong sexual dimorphism in cortical bone and dentine developments. The developmental pattern of dentine also seems to vary according to individual's ancestry. We measure a stronger covariation signal between cortical bone and dentine volumes than with any other dental tissue. A more complex covariation pattern is shown when splitting the modern sample by age, sex, and ancestry, as no signal is found in some subsamples while others show a covariation between cortical bone and either crown or radicular dentine. Finally, no difference in cortical bone volume is noticed between the modern young adults and the five young adult composite Neandertals from Marine Isotopic Stages (MIS) 5 and 3. Greater dentine Cortical bone and dentine (co)variation volumes are measured in the MIS 5 chimeric Neandertals whereas a strong interpopulation variation in dentine thickness is noticed in the MIS 3 chimeric Neandertals. Further research on the cortical bonedentine covariation will increase understanding of the impact of endogenous and exogenous factors on the development of the mineralized tissues

Les vestiges humains gravettiens dans le Sud-Ouest de la France : bilan du projet Gravett’os

Cette communication présente les principaux résultats du projet Gravett’Os, qui porte sur du matériel anthropologique du Sud-Ouest de la France (découvertes récentes et reprises des collections anciennes) associé au Gravettien (34-24 000 cal BP). Ce projet a permis l’identification de 32 individus provenant de 5 sites (Cussac, Fournol, Gargas, Abri Pataud, Cro-Magnon). Nos études confortent les analyses précédentes sur les comportements au Gravettien : extrême mobilité et division sexuelle du..