Doctoral Dissertation Improvement: Comparison of Human Population Distances Using Genetic and Craniometric Data

Arizona State University, Scottsdale AZ

Investigators

Abstract

Morphology is often used as an indicator of genetic relationships. However, our growing understanding of genetics suggests that the influences on anatomy are frequently not simple. Many factors including development, environment, and adaptation, are known to affect form and complicate the interpretation of relationships. Few studies have evaluated the nature of the complex relationship between morphological variation and genetic distances. The first goal of this study is to assess the association between skull morphology and genetic relationships in modern humans. This test will integrate an anatomical analysis of human cranial form with the growing database of information on human genetic diversity. Using three-dimensional cranial data and neutral genetic loci for seventeen human populations, depictions of population relationships will be statistically compared. The second goal of this research is to evaluate the extent to which different subsets of cranial data may vary in their correlation with genetic relationships in humans. Subsets include data separated by skull region or by mode of evolution (i.e., neutrally evolving through genetic drift vs. non-neutrally evolving through selection). It is likely that influences will vary for different regions of the cranium, suggesting that some regions may be more reliable indicators of genetic relationships than others. Through a comparison of molecular and anatomical data, this study will provide a rigorous test of the hypothesis that some aspects of skull form reflect genetic relationships more accurately than others for modern human populations. To address this hypothesis, several regions of the skull (the skull base, face, mandible, palate, teeth, temporal bone, and cranial vault) will be analyzed to determine which regions co-vary with genetic distances. An underlying assumption of many studies is that anatomical regions evolving by genetic drift are the most informative about relationships, because they are not affected by adaptation, which can result in superficial similarities among distantly related species. A subsidiary set of analyses will test the hypothesis that scenarios of relationships derived from neutrally evolving regions of the cranium will more closely match those based on genetic data than those obtained from cranial regions not evolving neutrally. It will address the question of whether skull morphology directly reflects genetic relationships. The broader impacts of this study include the investigation of the complex association between anatomical characteristics and genetic relationships generally, which is an interesting, broad biological issue, relevant beyond physical anthropology. The degree of concordance between anatomical and genetic data has been an issue of debate among biologists and geneticists for a wide range of species, and the question is relevant to research regarding the evolution and anatomy of many different species. This study's dataset will also be made available for other researchers on a webpage, thus contributing to future research. In addition, graduate student co-PI will receive training in conducting research.