Genetical-demographic data from two Amazonian populations composed of descendants of African slaves: Pacoval and Curiau

The Amazon region of Brazil includes communities founded by escaped slaves, some of which still remain relatively isolated. We studied two such Afro-B razilian communities (Pacoval and Curiau), in the rural area of Alenquer, P ara, and in the metropolitan region of Macapa, Amapa, respectively. Among 1 2 blood loci, alleles considered as markers of African ancestry, such as HB B*S, HBB*C, TF*D1, HP*2M ABO*B, RH*D-, and CA2*2 were found at frequencies that are expected for populations with a predominantly African origin. Esti mates of interethnic admixture indicated that the degree of the African com ponent in Curiau (74%) is higher than that of Pacoval (44%); an Amerindian contribution was not detected in Curiau. Estimated Values of African ancest ry fit well with the degree of isolation and mobility of the communities. P acoval exhibited a high proportion of immigrants among the parents and gran dparents of the individuals studied, whereas persons living in Curiau exhib ited a tow revel of mobility, despite its location in the metropolitan area of Macapa city, suggesting a relatively strong barrier against the interet hnic admixture in this population. In addition, analysis of genetic data in a sub-sample consisting of individuals whose parents and grandparents were born in the study site, and that probably represents the populations two g enerations ago, indicated that gene flow from non-black people is not a rec ent event in both populations.