The classification of modern humans into categories using phenotypic traits has experienced a lengthy and complex history in biological anthropology. While understanding the patterns of human biological variation is essential to revealing population structure, demographic history and the trajectory of modern human evolution, such categorization, even if based on biological differences, is contentious given its past association with concepts of "race" and related ideological agendas. Within physical anthropology, criticisms of the "race concept" and anxieties over scientific racism have generated concerns regarding the validity of any study that uses morphological variation as a way to explore evolutionary relationships among human groups. It is argued that any biological information captured by concepts of "race", "ethnicity" or "geographic ancestry" is necessarily confounded by personal beliefs and flawed methodologies and that, in turn, it is impossible to achieve an unbiased explanation of human variation. A tension exists, therefore, between those biological anthropologists who use craniometric variation as a means to access past population structure in phenotypic distance studies or to estimate individual ancestry in forensic contexts, and those who associate any discussions of group differentiation with racial typing. New genetic research on the interaction between culture and biology suggests, however, that there are alternative methods that can be explored in skeletal studies for scientifically detecting group differences and determining the statistical and practical significance of demographic information. Recent genomic work has successfully applied model based clustering to autosomal microsatellite loci in large, world-wide samples, and has identified clusters which closely corresponded to major geographic regions, ethno-culturally identifiable groups, and even admixed populations. These results show the feasibility of population classification by continental ancestry as well as the importance of "race", "ethnicity" and "ancestry" information to studies of population structure. The central question remains therefore: can similar nested hierarchical sub-structuring, or "population clusters", be revealed from phenotypic, and specifically, craniometric data using modern human samples? This project applies model based clustering, geometric morphometry, and traditional multivariate statistics to the W.W. Howells and T. Hanihara world-wide craniometric datasets and large Medieval Danish cemetery samples from the Anthropological Data Base Odense University (ADBOU) collection. Traditional linear measurements, trussed inter-landmark distance values, and three-dimensional coordinate data are used (1) to test the efficacy of these new and potentially more powerful quantitative approaches to understanding population-based differences in craniofacial shape and (2) to investigate the statistical significance of among and within-group discrimination using craniofacial measurements. This project also explores the evidentiary relevance of estimating "geographic ancestry" and its relationship to "race" using craniometrics in forensic and medico-legal contexts and the practical value of the classification results produced given current Daubert standards for expert testimony with the addition of modern American samples drawn from the University of Tennessee's Forensic Anthropology Data Bank (FDB) and demographics from the United States Census 2000.
The association of clusters with geographic regions, ethno-cultural groups, and admixed populations has significant disciplinary and socio-political implications. This research will demonstrate the potential of population classification by continental ancestry and weigh the importance of "race", "ethnicity" and "ancestry" information to studies of population structure. It will also provide recommendations for improved statistical methodologies for geographic ancestry estimation and for the evidentiary significance of estimating ancestry in forensic anthropological and medico-legal contexts given current Daubert standards for scientific evidence. The craniofacial measurements obtained for this study will offer an opportunity to address questions of human biological variation, and specifically the quantification of world-wide craniometric diversity. In testing the statistical effects of combining mixture modeling with traditional and geometric morphometrics and the applicability of clustering algorithms to questions of among and within-population classification, this research will contribute to quantitative applications in anthropology. Moreover, in making new three-dimensional craniometric information from the Anthropological Data Base Odense University (ADBOU) collection available for future morphometric research, this project will not only advance the broader study of "shape" but will also increase our knowledge of the life history of these past Danish peoples, thus facilitating studies in areas of concern to skeletal biologists, population geneticists, bioarchaeologists and demographers alike and supporting additional inter-collegiate collaborations. As the raw data and the statistical computer code written for this study will be made freely accessible to other scholars, this project will encourage future researchers to investigate the methodology here employed (therefore prompting refinements to the theories addressed by this project and improvements to our scientific methods) and bring new and different questions to bear on the resources that made this project possible.
