Three-dimensional endocranial shape variation in the modern Japanese population

Quantifying variation in human endocranial shape is important for interpreting the morphogenetic mechanisms of endocranial morphologies, as endocranial morphology has emerged from modification of the ontogenetic processes in the course of human evolution. We therefore analyzed patterns of morphological variability in endocranial shape among the modern Japanese population using landmark-based geometric morphometrics. After generating virtual endocasts of cranial specimens based on computed tomography scans, we defined a total of 171 conventional anatomical and sliding semi-landmarks on the endocranial surface. The brachycephalic/dolichocephalic tendency was the most frequently identified endocranial shape variation. In addition, we found that a smaller endocranium tended to be associated with a relatively larger cerebellar region accompanied by a flat, depressed parietal region and a more superiorly located frontal pole. Asymmetric shape variability possibly resulting from petalia was also observed, indicating that global brain asymmetry is related to endocranial shape. The present description of endocranial shape variability may contribute to the comparative understanding of the evolution of the endocast morphology of fossil hominins.