Quantifying Cranial Shape Change with Age in Adult Modern Humans: Through a Geometric Morphometric Approach

Skeletal ontogenetic changes in shape have been closely examined and researched in modern humans during the prenatal to subadult stages of development. However cranial shape changes during adulthood are less notable and studied. This thesis used 35 three-dimensional landmarks from 13 cranial specimens of known age to estimate shape changes associated with age. Since research on this topic is less well known I hypothesized that the human cranium does undergo shape change during adulthood and that these changes will provide more information on cranial ontogeny. Three-dimensional surface models of the superior and inferior portions of crania were created by photogrammetry using Agisoft Photoscan. Geomagic Control was used to unite these parts into a single 3D model of each specimen. The 35 craniometric landmarks were digitized using Landmark Editor. The landmarks were superimposed through a Generalized Procrustes Analysis in MorphoJ. Variations due to size, position, and orientation were removed from the data leaving the variable of shape for each specimen. The resulting 13 configurations of Procrustes coordinates were regressed against chronological age. Results of the regression analysis demonstrated a correlation between cranial shape with age. Age has a subtle effect on cranial shape that accounts for approximately 5.7% of shape variance. Though minimal, as the cranium ages the position of the zygomaxillare anterior narrows resulting in a sunken or hollowed look of the craniofacial region of the skull