University of Bordeaux - Ph.D. Candidate position in Facial Skeleton Variation, Adaptation, and Evolution
Ideal candidate will have majored in Biology and later on specialized in Biological Anthropology (Master or equivalent). The candidate will have knowledge in evolution, gross anatomy, and be a user of tools such as 3D images analyses, and multivariate statistics.
The question of the adaptation to changing environments is a key issue in the study of human evolution. Many traits characterizing the genus Homo (e.g., bipedalism) have been interpreted as adaptations to environmental changes. Researchers still debate the number of skeletal traits in anatomically modern Homo and Neanderthals exposed to cold environments that are the consequence of cold adaptation.
Several studies focusing on anatomical collections or archaeological material (dry skulls) demonstrate that nasal cavity (NC) morphology varies according to ecogeographic factors (e.g. temperature, humidity), leading some authors to argue that the morphology of the facial skeleton of Neanderthal is cold-adapted. However, the functional negative space primarily responsible for air conditioning is represented by the nasal airways (NA) which are delimited by mucosa. The morphology (i.e., shape and size) of NA are defined by the mucosa and not directly by the NC. Consequently, a better quantification of the morphological variation and co-variation of NC, NA, and the paranasal sinuses (for which the exact function is still debated) is crucial. Recent studies demonstrate that the degree of covariation between NA and NC morphologies is much lower than initially thought, which questions the robusticity of physiologic interpretations based on the study of dry skulls alone.
Furthermore, the mechanisms that produce the hypothesized cold-adapted phenotypes remain poorly understood. For a long time, these phenotypes were interpreted as purely hereditary. However, several recent studies based on animal models (mostly rats and mice) demonstrated that some of these phenotypes (cranial and postcranial) could be explained by specific responses of the organism to cold. In other words, that phenotypic plasticity is a key mechanism in the production of these cold adapted phenotypes.
The objectives of this PhD thesis in Biological Anthropology will be:
- To quantify the morphological variation of NC, NA, and the paranasal sinuses and the morphological co-variation between these different anatomical units among modern human populations from different regions of the world (in vivo CT images) in order to better characterize the intra- and inter-population variation (e.g. sexual dimorphism, geographic origin);
- To quantify the influence of temperature on cranial bone and cartilage growth, particularly in the region of NC, in mouse models exposed to different temperature conditions;
- To determine the evolutionary implications of the produced results, especially regarding the tradeoff between phenotypic plasticity and heritability.