Post-natal mandibular growth patterns in Neanderthal and Homo sapiens
Motifs de croissance mandibulaire post-natale de Néanderthal et Homo sapiens à travers une approche de morphométrie géométrique
Résumé
Research in hominid growth and development studies serves to understand species specific evolutionary patterns and phylogenetic relationships between species. A particular focus is put on the investigation of the emergence of modern patterns of growth and development. Neanderthals, due to their morphological and phylogenetic proximity with modern humans are often used in these comparative studies. Research questions have focused on the moment in developmental time when ontogenetical differences between the two species emerge as well as on the evolution of growth patterns between the two species, with the main question being whether and at what point in time they are parallel or divergent. In this study, we propose to test the different hypotheses regarding Neanderthal and H. sapiens growth velocity using the mandible as a proxy. In the specific, we want to see whether morphological differences between the two species arise during post-natal growth or whether growth and developmental patterns follow parallel pathways. For that, we use a geometric morphometric method evaluating overall mandible shape on a large reference collection of Neanderthal and H. sapiens mandibles of all dental age stages. Results shows that apomorphies are present in early dental stages (e.g. chin) which allow to distinguish the species. However, we observed that the antero-posterior elongation and augmentation in height follows parallel growth patterns in both species. Interestingly, during the eruption of the first permanent molar, modern humans show a specific morphology which could be related to a growth spurt, not observed in the Neanderthals from our reference collection. In general, this preliminary study has highlighted how mandibles of both Neanderthals and modern humans have the same velocity of maturation and follow an age-related gradient of overall growth.
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