Palate Shape Offers Limited Utility in Population Affinity Estimation among Modern U.S. Groups

Abstract

Population affinity estimation remains an important but challenging component of biological profile analyses. Palate shape (PS) is a historically described macromorphoscopic trait now incorporated into updated statistical workflows, yet its discriminatory value in modern samples remains unclear. This study quantified PS variation using postmortem computed tomography scans of 150 Black, Hispanic, and White individuals from the New Mexico Decedent Image Database. Palate outlines were quantified using elliptical Fourier analysis and summarized with principal components analysis. Reconstructed contours were visualized for the combined sample, with exploratory population-sex subset reconstructions provided descriptively. PC scores from the combined sample alone were statistically analyzed using multivariate analysis of variance (MANOVA), type III analyses of variance (ANOVAs), Tukey-adjusted comparisons, and linear discriminant function analysis with leave-one-out cross-validation. Reconstructed contours showed broad variation in palate width, lateral arcade roundness, and anterior skew, with aspects of the historically described PS occurring across reference groups. MANOVA identified a significant population effect, and follow-up ANOVAs indicated a significant population effect for PC1; however, effect sizes were small. Discriminant function analysis produced 52.7% apparent accuracy and 44.0% cross-validated accuracy, only modestly above the 33.3% chance expectation. Sex and population-sex classification also performed poorly, with low Matthews correlation coefficients across models. These results indicate PS contains some population-associated variation but lacks sufficient discriminatory structure for reliable standalone classification. PS should therefore be interpreted cautiously, particularly in reduced-trait or fragmentary contexts, and its contribution within multi-trait statistical frameworks requires further empirical evaluation.