Biological Distance and the African American Dentition

Biological Distance and the African American Dentition

Ohio State University
229 pages

Heather Joy Hecht Edgar

A DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

Gene flow occurs whenever two human populations come in contact. African Americans are the result of gene flow between two biologically disparate groups: West Africans and Americans of European descent. This project utilized characteristics of dental morphology to trace genetic relationships among these three groups. Dental morphological traits are useful for this purpose because they are heritable, do not remodel during life (although they can be lost to wear or pathology), and can be compared equally among samples from past and present populations. The results of this research provide new knowledge about human microevolution in a biocultural setting. By analyzing observations from a variety of samples from African Americans, European Americans, West Africans, and western Europeans, conclusions were made on patterns of genetic change through time and space.

The specific hypothesis addressed is that since gene flow has been continuous among West Africans, African Americans, and European Americans in the American colonies and subsequently in the United States, the more recent a sample of African Americans observed, the more they tend toward the average, genetically, of West Africans and Europeans. Dental characteristics reflect this heritage and the pattern of temporally limited genetic similarities. In addition to testing this hypothesis, several predictions were made and tested regarding the historical patterns of admixture in African Americans. These predictions involved whether gene flow has occurred at a constant rate, whether African Americans with greater admixture were more likely to take part in the Great Migration, and whether the dental morphology of the Gullah of South Carolina is especially like their West African ancestors.

The results of this research indicate that while admixture of European American genes into the African American gene pool has been continuous over the last 350 years, it has not occurred at a constant rate. Cultural trends and historical events such as the Civil War and the Jim Crow era affected the rate of admixture. A final product of the current research is a series of probability tables that can be used to determine the likely racial affiliation of an unknown individual. These tables are useful in historic archaeological and forensic settings.

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