Fetal and neonatal maxillary ontogeny in extant humans and the utility of prenatal maxillary morphology in predicting ancestral affiliation.

OBJECTIVES: The midface of extant Homo sapiens is known to undergo shape changes through fetal and neo-natal ontogeny; however, little work has been done to quantify these shape changes. Further, while midfacial traits which vary in frequency between populations of extant humans are presumed to develop prenatally, patterns of population-specific variation maxillary shape across ontogeny are not well documented. Only one study of fetal ontogeny which included specific discussion of the midface has taken a three-dimensional geometric morphometric approach, and that study was limited to one population (Japanese). The present research project seeks to augment our understanding of fetal maxillary growth patterns, most especially in terms of intraspecific variation.
MATERIALS AND METHODS: Three-dimensional coordinate landmark data were collected on the right maxillae of 102 fetal and neo-natal individuals from three groups (Euro-American, African-American, "Mixed Ancestry").
RESULTS: Shape changes were seen mainly in the lateral wall of the piriform aperture, the anterior nasal spine, and the subnasal alveolar region. The greatest difference across age groups (second trimester, third trimester, neonates) was between the second and third trimester. Euro-Americans and African-Americans clustered by population and differences in midfacial morphology related to ancestry could be discerned as early as the second trimester (p = .002), indicating that population variation in maxillary morphology appears very early in ontogeny. DISCUSSION: The midface is a critical region of the skull for assessing ancestry and these results indicate that maxillary morphology may be useful for estimating ancestry for prenatal individuals as young as the second trimester.