Odontometric differentiation between Southwest Hispanics, Native Americans, and European Americans
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Ancestry estimation for Hispanic Americans is increasing in importance as this minority population increases in the United States. Hispanics are historically an admixture of various geographic populations including European, Native American, and African. This combination of genes has caused many intermediate skeletal features that make identification of Hispanics a complicated process, especially when compared to Native Americans. "Hispanic" cannot efficiently encompass, as a term, the genotypic composition of multiple populations, as Hispanics from the Southwestern United States are historically a combination of Native American and European genes, whereas those from the Caribbean are historically an admixture of Native American, European, and African genes. While each of these regions can exhibit a certain combination of all three of these ancestral populations, each region has experienced a characteristic frequency of admixture. Southwest Hispanic populations are genotypically and phenotypically primarily comprised of Native American and European genes, resulting in an intermediate skeletal composition that prevents the distinct ancestry discrimination attainable by broad geographic groups. Previous dental morphological studies (Edgar 2013) have also presented results of intermediacy and particular difficulty separating these individuals from Native American and Asian groups; however, metric studies of the dentition of this population have yet to be investigated. Data were collected from n=569 dental casts from the James K. Economides collection which is housed at the Maxwell Museum in Albuquerque, New Mexico. Measurements included were the mesiodistal and buccolingual dimensions of the polar teeth of the morphogenetic field theory and the width and depth of the mandibular and maxillary arches. The morphogenetic field theory, as developed by Butler (1939) and adapted by Dahlberg (1945), represent the most stable teeth of the four fields of the dentition - incisors, canines, premolars, and molars. These "polar" teeth exhibit the least variation in crown size and shape. Significant differences were identified between ancestry groups and these were subsequently used to identify allocation rates between all groups and between particular sets, or groups, of ancestries. Discriminant function equations were developed as a tool for ancestry estimation. Success was greatest when both dental crown and arcade variables were pooled together in an analysis. Results of this study indicate odontometric analyses are useful in differentiating between Native Americans and European Americans, with classification rates ranging between 75.2% and 86.3%; however, much work must be conducted before application on Hispanic populations is possible. The Southwest Hispanic population exhibited greater phenotypic similarity to the European American population and had significantly lower success in allocation than between Southwest Hispanics and Native Americans. In cases where sex was known, successful allocation decreased, although females generally exhibited greater success than males. Potential utility is observed in this study when sex is unknown, and the development of a statistical methodology utilizing the dentition is proposed.