Masters Theses

Date of Award

12-1974

Degree Type

Thesis

Degree Name

Master of Arts

Major

Anthropology

Major Professor

Richard L. Jantz

Committee Members

Harry M. Lindquist, William M. Bass

Abstract

A study of the population structure of Hancock County, Tennessee, was conducted in order to determine the degree of genetic isolation, and the likelihood of random genetic drift, experienced by the county population. Genealogical information for the study was obtained from a random sample of the population utilizing two series of questionnaires. In all, data were obtained for 275 couples from all areas of Hancock County.

Four main analytical steps were taken with these data to determine: (1) the amount of inbreeding, through a surname isonymy study, (2) the effective population size, (3) the patterns of human movement, primarily marital movement, and its main components--distribution, orientation, and diffusion, and (4) the coefficient of breeding isolation, the indicator of human genetic isolation.

The surname isonymy study indicated a much greater amount of inbreeding in the population in the past with a tendency toward breakdown during the last generation due to increased mobility of the population. This increased movement, moreover, was found to exhibit distinct orientations corresponding closely to the main avenues into and out of the county, and also to be limited somewhat in space to an area of approximately 20 miles around Hancock County.

The coefficient of breeding isolation, the product of the effective population size and the effective immigration rate, was found to be in agreement with the indications of the inbreeding study. Although it was found to be of too great a magnitude during the last generation for the degree of isolation necessary for the development of genetic diversification, all indications are that as recently as only one generation back genetic isolation experienced by the county population was much greater.

When the gene frequencies of the Melungeons, one segment of the Hancock County population, were compared with those of other populations of the United States and England they were found to fall outside the range of these other populations in all but one case. From this it can be concluded that a degree of genetic isolation necessary for random genetic drift was almost assuredly experienced by the Hancock County population in the past, and that this isolation has resulted in altered gene frequencies for this population.

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