Quantification of maxillary ontogenetic processes using surface histology and geometric morphometrics

• Main Author: Schuh, Alexandra
• Other Authors: Universität Leipzig
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2020
• Subjects: Bone modeling; ontogeny; facial evolution; info:eu-repo/classification/ddc/570; ddc:570; Greenland
• Online Access: https://nbn-resolving.org/urn:nbn:de:bsz:15-qucosa2-759133; https://ul.qucosa.de/id/qucosa%3A75913; https://ul.qucosa.de/api/qucosa%3A75913/attachment/ATT-0/

This thesis investigates the variability of ontogenetic maxillary bone modeling patterns in humans (Homo sapiens) and chimpanzees (Pan troglodytes). Along with sutural growth, bone modeling is the microscopic process by which bones grow in size and model their shape. It results from the simultaneous cellular activities of bone formation (produced by the osteoblasts) and bone resorption (produced by the osteoclasts) on bone surfaces. The study of these activities can bring new insights into our understanding of maxillary, and, more generally, facial ontogeny. However, bone modeling variability remains poorly understood. Using surface histology, we developed quantitative methods to objectively compare and visualize bone modeling patterns. In parallel, geometric morphometric methods were used to capture and quantify maxillary shape changes. Both methods were used for the first time together in an integrative approach. A large sample of H. sapiens individuals ranging from birth to adulthood, and originating from three geographically distinct areas (Greenland, Western Europe and South Africa), was used to infer the variation in maxillary bone modeling at the intraspecific level. We found that human populations express similar bone modeling patterns, with only subtle differences in the location of bone resorption. Moreover, differences in developmental trajectories were identified. This suggests that population differences in maxillary morphology stem from changes in timing and/or rates of the osteoblastic and osteoclastic activities. Adult individuals show similar maxillary bone modeling patterns to subadults, with both cellular activities expressed at reduced intensities. All human populations express high amounts of bone resorption throughout ontogeny, and high inter-individual variation. In contrast, we find low amounts of bone resorption and a low inter-individual variation in chimpanzees, which results in the anterior projection of their maxilla. In chimpanzees, resorption is predominant in the premaxilla, which ...