The estimation of Japanese and Native American ancestry using dental metric measurements and morphological trait frequencies
Green, Madelyn K.
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Ancestry assessments in bioarchaeology and forensic anthropology are best analyzed with population-specific methods. Through population-specific ancestry methods, the generalized Native American/Asian ancestry category can be better refined to reflect the diversity of Native American and Asiatic people. Individuals from modern (~1900 to present) Seminole Native American and Japanese populations, housed at The Ohio State University and Jikei University in Tokyo, respectively, reflect a relatively unbiased population sample, as demographics range from juveniles to adults, with both sexes being equally represented. This broad sampling of individuals from the Florida Seminole group and the greater Tokyo region enables researchers to explore the degree of variation between the Seminole and Japanese groups, as can be demonstrated osteologically. Dentitions are an ideal candidate to measure intra-population variability due to heritabilities of both their tooth size and dental morphological characteristics within populations. In an attempt to better understand the variation between Native American and Asian populations, observations of Seminole and Japanese-specific dental morphology and tooth dimensions were recorded from 281 individuals using the Arizona State University Dental Anthropology System (ASUDAS) and mesiodistal and buccolingual measurements, respectively. Significant differences, indicated by a p-value ≤ 0.05, were identified between the Seminole and Japanese groups in the analysis of morphological dental traits and odontometrics. Nineteen statistically significant morphological traits that differed in expression between the two sampled groups were identified, with eight traits being more present in the Seminole group than the Japanese group, whereas eleven traits being more present in the Japanese group than the Seminole group. Linear regression (LRA) and discriminant function analyses equations were developed from three sets of odontometric datasets; the raw, unaltered collected data, the general measurement mean dataset which supplements missing variables, and the ancestry-specific measurement mean data set which supplements missing variables. Both the linear regression and discriminant function models demonstrated success in classifying the Seminole and Japanese groups. The LRA equations presented classification rates higher than chance (81.5-90.4%). Twenty-three DFA equations were developed, ranging in successful classification rates of 61.5% to 100.0%. The ancestry-specific measurement mean dataset performed the best in both the LRA and DFA models. The results of this study indicate that morphological trait observations and odontometric analyses can be useful tools in the differentiation of Native American and Asian populations, as differences between subgroups of these populations (Seminole and Japanese) were identified. These differences are likely due to the homogeneous and insular composition of both sampled populations. Further analysis of the statistically significant morphological traits identified in the current study and continued testing of more subpopulations of Native American and Asian populations will not only aid in ancestry estimations in forensic and bioarchaeology research, but also in the cessation of grouping Native American and Asian individuals under one category.