58 research outputs found
Stage de morphométrie géométrique (12-13/10/2020, MNHN, Paris)
No full textOrganisation : Dimitri Neaux (AASPE). Lieu : salle de conférence de géologie, 43 rue Buffon 75005 Paris. Dates et horaires : lundi 12 octobre (10-17h) et mardi 13 octobre (9-16h). Présence sur les 2 jours requise. La morphométrie géométrique est une méthode de plus en plus utilisée en bioarchéogie (os, dents, graines, artéfacts…), employée pour étudier et analyser la forme d'une structure. Elle permet la quantification des variations de forme et la mesure des similarités et des différenc..
Covariations of craniofacial structures in hominids
No full textCe travail de thèse porte sur l'intégration des structures craniofaciales au sein de la famille des hominidés. Au cours de l'évolution, une réduction du prognathisme et une diminution de la longueur de la face sont observées chez les taxons appartenant au rameau humaine. Cette réduction des structures faciales est associée à une base du crâne plus fléchie et à une mandibule plus gracile. L'objectif de ce travail est de définir le rôle joué par les changements basicrâniens et mandibulaires dans la mise en place de la face courte et droite des humains modernes. Dans ce contexte, les schémas d'intégration liant la face et les autres structures crâniennes (basicrâne et mandibule) ont été décrits et quantifiés dans ce mémoire. Ce travail a été effectué sur la base d'un échantillon de crânes incluant l'ensemble des genres d'hominidés actuels : les humains modernes, les chimpanzés, les gorilles et les orangs-outans. Les crânes ont été préalablement numérisés à l'aide d'un scanner médical. Les schémas d'intégration craniofaciaux ont alors été étudiés à l'aide d'outils statistiques et de méthodes d'analyses en morphométrie géométrique. Ce travail a permis de mettre en avant plusieurs mécanismes d'intégration craniofaciale, propres aux humains modernes. Ces schémas d'intégration spécifiques permettent d'expliquer en grande partie la mise en place de la face réduite des humains modernes. Ces résultats permettent donc d'éclairer les mécanismes d'évolution et de mise en place des structures faciales chez les hominidés et dans le rameau humain.This thesis dissertation is dedicated to the study of craniofacial structures within the hominid family. Throughout evolution, a reduction of facial prognathism and a diminution of the facial length are observed in the taxa which belong to the human lineage. This reduction of facial structures is associated to a more flexed cranial base and to a shorter mandible. The aim of this work is to define the role played by the basicranial and mandibular changes in the set up of the short and straight face of modern humans. In this context, the patterns of integration linking the face and the other cranial structures (basicranium and mandible) are decrypted and quantified in this thesis dissertation. This work has been done with a sample including all the extant hominid genera: modern humans, chimpanzees, gorillas, orang-utans. The skulls were first scanned using a medical scanner. Patterns of craniofacial integration were then studied using statistical tools and geometric morphometric analysis methods. This work underlined several mechanisms of craniofacial integration, unique to modern humans. These specific patterns of integration can explain an important part of the set up of modern humans reduced face. Thus, these results enlighten the evolution mechanisms and the set up of facial structures in hominids and in the human lineage
Facial Orientation and Facial Shape in Extant Great Apes: A Geometric Morphometric Analysis of Covariation
No full textThe organization of the bony face is complex, its morphology being influenced in part by the rest of the cranium. Characterizing the facial morphological variation and craniofacial covariation patterns in extant hominids is fundamental to the understanding of their evolutionary history. Numerous studies on hominid facial shape have proposed hypotheses concerning the relationship between the anterior facial shape, facial block orientation and basicranial flexion. In this study we test these hypotheses in a sample of adult specimens belonging to three extant hominid genera (Homo, Pan and Gorilla). Intraspecific variation and covariation patterns are analyzed using geometric morphometric methods and multivariate statistics, such as partial least squared on three-dimensional landmarks coordinates. Our results indicate significant intraspecific covariation between facial shape, facial block orientation and basicranial flexion. Hominids share similar characteristics in the relationship between anterior facial shape and facial block orientation. Modern humans exhibit a specific pattern in the covariation between anterior facial shape and basicranial flexion. This peculiar feature underscores the role of modern humans' highly-flexed basicranium in the overall integration of the cranium. Furthermore, our results are consistent with the hypothesis of a relationship between the reduction of the value of the cranial base angle and a downward rotation of the facial block in modern humans, and to a lesser extent in chimpanzees. © 2013 Neaux et al.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Experimental assessment of the relationship between diet and mandibular morphology using a pig model: New insights for paleodietary reconstructions
No full textInternational audienceDietary habits exert significant selective pressures on anatomical structures in animals, leading to substantial morphological adaptations. Yet, the relationships between the mandible and diet are still unclear, raising issues for paleodietary reconstructions notably. To assess the impact of food hardness and size on morphological structures, we used an experimental baseline using a model based on the domestic pig, an omnivorous mammal with bunodont, thick-enameled dentition, and chewing movements similar to hominids. We hypothesized that the consumption of different types of seeds would result in substantial differences in the morphology of the mandible despite similar overall diets. The experiment was conducted on four groups of juvenile pigs fed with mixed cereal and soy flours. The control group received only flours. We supplemented the four others with either 10 hazelnuts, 30 hazelnuts, 30% barley seeds, or 20% corn kernels per day. We investigated the shape differences between the controlled-fed groups using three-dimensional geometric morphometrics. Our results provide strong evidence that the supplemental consumption of a significant amount of seeds for a short period (95 days) substantially modify the mandibular morphology of pigs. Our analyses suggest that this shape differentiation is due to the size of the seeds, requiring high and repeated bite force, rather than their hardness. These results provide new perspectives for the use of mandibular morphology as a proxy in paleodietary reconstructions complementing dental microwear textures analyses
Implications of the Relationship Between Basicranial Flexion and Facial Orientation for the Evolution of Hominid Craniofacial Structures
No full textThe basicranium and face have been linked through genetic, developmental, and functional relationships throughout their evolution. As a result, basicranial morphology most likely plays a major role in the evolution of facial structures. We describe the relationships between basicranial flexion and the face in Homo, Pan, and Gorilla to determine the role of cranial base angle reduction in the setup of the short and orthognathic face of Homo. We test the hypotheses that cranial base flexion plays a significant part in variation in facial orientation, length, and projection at the intraspecific level. The sample comprised 125 crania of adult specimens including 66 Homo sapiens, 32 Pan troglodytes, and 27 Gorilla gorilla. We described the cranial base and face using landmarks placed on scans of the surfaces and computed correlations between the cranial base angle and facial orientation, length, and projection. Our results support the hypotheses that cranial base flexion plays a significant part in facial orientation for Homo and Pan and in facial length for Pan. The hypothesis that basicranial flexion is related to a reduction of facial projection is not supported. The findings suggest that basicranial flexion can explain several anatomical specificities of hominins, including the reduction of prognathism and the reduction of the length of the nasopharynx. We found different patterns in the different genera, highlighting the fact that changes in the relationship between craniofacial structures may have occurred during hominid evolution.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Integration between the face and the mandible of Pongo and the evolution of the craniofacial morphology of orangutans
No full textObjectives Extant Pongo diverges from other hominids by a series of craniofacial morphological features, such as a concave face, a reduced supraorbital torus, or an upwardly orientated palate. These traits are not independent because the skull is a complex integrated structure. The aim of this study is to describe the relationship between the face and mandible of Pongo, in order to examine the link between mandibular structures and the set-up of the unique facial features of orangutans. Materials and methods Using 3D geometric morphometrics, the morphological integration between face and mandible of Pongo is compared to that of the three extant hominids: Homo, Pan, and Gorilla. Pooled within-species partial least squares analyses are computed in order to quantify the patterns and levels of integration. Results The covariation analyses show unique patterns of integration and levels of correlation in Pongo when compared to other hominids. This study shows that the craniofacial features distinguishing Pongo from African great apes are related to differences in the patterns of integration and levels of correlation between facial and mandibular shape. Discussion Changes in important functions may play a part in these modifications of craniofacial integration. This study underlines the importance of the mandible and of the mandibular functions in the development of the unique craniofacial features of Pongo. Am J Phys Anthropol 158:475-486, 2015.SCOPUS: ar.jFLWINinfo:eu-repo/semantics/publishe
Captivity and cranial development in wild boar (Sus scrofa): exploration of new markers of the process of domestication
No full textInternational audienc
Exploring the impact of soil ingestion on dental microwear textures using a wild boar experimental model
No full textInternational audienceDental microwear has been widely used to reconstruct the diet of past mammals. However, understanding the respective impact of exogenous mineral particles on dental wear is an ongoing challenge. Among palaeontologists and evolutionary biologists, this topic is a key issue in the debate on the selective pressures driving dental phenotypes, such as molar hypsodonty in ruminants, molar lengthening in suids or enamel thickening in hominins. Among archaeologists, it can help better understand ancient herd-feeding systems. Particularly, few studies have shown that soil ingestion generates different microwear traces.To fill this gap, this study relies on the first large-scale controlled-food experiment on wild boars (Sus scrofa). It provides the opportunity to investigate the impact of natural soil ingestion over microwear traces by comparing penned wild boars that were able to root with stalled wild boars that were not. Dental microwear textures (DMT) variations were measured on 22 controlled-fed boars kept captive from 6 to 24 months old, either in an indoor stall with no soil ingestion (n=10), or in an outdoor wooded pen (n=12) with rooting behaviors and natural soil ingestion. We conducted particle size distribution analyses on two soil samples. They indicate that the soil is mainly composed of sand (38 %) and silt (43 %), with few clay fractions (19 %), which can be classified as a loam texture. We analyzed shearing and crushing facets of upper and lower first and second molars using two sets of texture parameters. In line with previous works, our results show that the consumption of exogenous abrasives in rooting boars leads to less rough and complex wear surfaces and more anisotropic than in stall-fed boars, even though they received the same diet. Thus, as previously stated, we highly recommend studying DMT when investigating ancient pig husbandry systems, particularly local changes in food management
Captivity and cranial development in wild boar (Sus scrofa): exploration of new markers of the process of domestication
No full textInternational audienc
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