| The nature of the relationship between cranial and molecular data in humans is currently poorly understood. As various regions of the skull respond to diverse pressures and develop at different times during ontogeny, it is likely that they will vary in the degree to which they reflect genetic distances. The knowledge of which cranial regions are reliable indicators of genetic relationships is crucial for studies of specimens for which DNA is unavailable and for the general understanding of the heritable component of cranial morphology.; This study assessed the correlations between molecular distances and morphology for several cranial datasets. Ninety-five three-dimensional cranial landmarks were digitized in fifteen human populations, and partitioned into groups based on anatomical region (basicranium, face, upper jaw, mandible, temporal bone, vault, and entire cranium), ossification type, and degree of masticatory strain. Linear dental dimensions were also collected. Matrices of population distances based on each dataset were statistically compared to molecular distance matrices. The morphology of the basicranium, entire cranium, face, mandible, temporal bone, and dentition were significantly correlated with molecular relationships, while the vault and upper jaw were not. The morphology of both endochondrally and intramembranously ossifying regions reflected molecular distances. Low and moderate strain regions were correlated with molecular distances, while high strain regions were not.; The microevolutionary forces impacting human skull morphology were identified, and the premise that neutrally evolving regions reflect genetic relationships more accurately than those under selection was tested. Within- and among-population variance-covariance matrices were statistically compared. Regions concluded to significantly reflect genetic distances in this study were not all evolving neutrally, suggesting a more complex association between adaptive and phylogenetic processes than is generally accepted.; This study helped elucidate the relationship between human cranial morphology and other factors, such as genetic distances. Patterns of cranial variation may reflect genetic distances in humans, even if skull morphology has been impacted to some degree by diversifying selection. As the entire cranium, temporal bone, basicranium, mandible, dentition, and upper face reflect genetic relationships, the morphology of these regions can be used as a proxy for molecular data, while high strain regions should be avoided. |
