Study on a Brazilian Isolate: I. Population Structure and Random Genetic Drift

A number of parameters were evaluated in order to determine the level of isolation of a small Brazilian community existing in partial geographic isolation and thereby evaluate the random genetic drift potential in the population. On a theoretical basis, it is concluded that the probability of genetic drift is low but cannot be excluded. The relatively small proportion of migrants (26%), the limited individual mobility, as given by marital distance (29 ± 7 km), the mean migrational distance (46 ±11 km), the small effective size (122), and the value of the product Nₑmₑ (26) agree with the possibility of genetic drift in this population. The observed coefficient of inbreeding (0.00239) is lower than that expected (0.0066) for random mating, suggesting some pressures against consanguineous marriage.