A Study of Tri-Racial Isolates in Eastern United States

A Study of Tri-Racial Isolates in Eastern United States

Human Heredity
Volume 6, Number 3, 1956/1957
DOI: 10.1159/000150862
pages 410–412

C. J. Witkop
National Institute of Dental Research, National Institutes of Health, Public Health Service, U.S. Department of Health, Education and Welfare, Bethesda, Maryland, U.S.A.

There are known to exist in the eastern part of the United States some 28 well defined tri-racial isolates. These groups represent gene pools of various proportions of Caucasian, Negro, and American Indian races. These groups are known as mixed bloods in their own communities. They are not accepted into the white community and do not consider themselves Negroes. As a result, they maintain their racial integrity by in-marriage within a few family names. They all represent the remnants of eastern Indian tribes.

A preliminary survey of each group was made by a questionnaire letter to the county health officer in whose district these groups reside. On the basis of subsequent studies it has been shown that about 10% of the genetically determined conditions that actually exist in these groups are reported by this method. One of these groups was selected for a detailed genetic study.

Detailed Study

A detailed study of the medical, dental, mental health, and social aspects of one of these groups comprising 5 000 living members is in progress in southern Maryland. We are trying to determine all of the hereditary pathological traits present in the group. This group was selected for study for the following reasons:

1. This group marries for the most part within only 14 family surnames. 2. Records indicate that the group has in-married for nearly 250 years. 3. These people reside in a limited geographic area of 2 counties of…

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