A demographic genetics and historical study of a culturally isolated endogamous population indigenous to southwestern Louisiana
After a brief review of the literature on inbreeding in human populations, the historical and political circumstances that led to the formation of a unique, isolated demographic unit indigenous to southwestern Louisiana are described. Details of the frontier boundary disputes in western Louisiana and east Texas, first between the French and Spanish (1715-1762) and later between the United States and the Spanish (1803-1821), are reviewed with special attention given to the events associated with the establishment of the Neutral Ground and the make-up of the first settlers to that region. Specifically, the history of the settlers of the former Cherry Winche country, known by the nickname Ten Milers, is updated and consolidated from widely scattered sources. As unbiased assessment of the possible origins of this alledged tri-racial isolate leads to the conclusion that there is no objective evidence that this population is of tri-racial ancestry Demographic and genetic data were compiled from censuses of local cemeteries and marriage records for this area. Inbreeding in this population was quantified using Crow and Mange's (1965) isonymy technique. The average inbreeding coefficient was estimated to be 7.938 x 10('-3), which is much higher than the average inbreeding estimates for the United States (9.0 x 10('-5); Freire-Maia, 1968) and is comparable with other human isolates. As part of a descriptive demographic profile, lifetable analyses were performed on the cumulative survival distribution in this population and various sub-populations (males vs. females, Ten Milers vs. non Ten Milers, etc.) are compared. Overall childhood mortality was high with 16% of the population failing to reach age one and 20% failing to reach age five. Relative measures of endogamy and migration confirm the endogamous nature of this population Investigation of the possible adverse effects of inbreeding, through the analysis of mortality distributions across sub-populations in different time intervals and in different seasons, suggests that differences in mortality distributions among sub-populations are the result of cultural rather than biological circumstances. Data on the relative age of marriage partners is also suggestive of a confounding influence on childhood mortality. Certain types of cancer show anomalous incidence levels in the region. No unique genetic diseases were found in association with this population