Genetic and anthropological studies in the island of Itaparica, Bahia, Brazil.

The ongoing racial admixture was studied in the island of Itaparica off the coast of the State of Bahia, in Brazil. The following gene frequencies were observed: Hb S = 0.039; Hb C = 0.022; PGD C = 0.024; Gd A = 0.217 and Gd A = 0.052, among 293 mixed school children whose black phenotype index (medium mulatto + dark mulatto + black/total) was 0.457. Data on racial groups, obtained from 898 death certificates of three periods (1889-1890, 1934-1937 and 1975-1980) showed that in about 90 years (three generations) the proportion of mulattoes had doubled, the whites had decreased to one third, and the blacks showed no variation. Changes in the frequencies of surnames within the whites over the same 90 years indicated a growing proportion of individuals with black ancestry flowing into the white group. Higher reproductive rates among the more negroid individuals is probably the leading force directing the racial admixture in the island.