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Isolate breakdown in Amazonia - the blacks of the trombetas river

H. Schneider^I; J.F. Guerreiro^I; S.E.B. Santos^I; Tania A. Weimer^II; Maria P.C. Schneider^I; F.M. Salzano^II

^IDepartamento de Genética, Centro de Ciências Biológicas, Universidade Federal do Pará, 66059 Belém, PA, BrasiL Send correspondence to H.S.
^IIDepartamento de Genética, Instituto de Biociências, Universidade Federal do Rio,Grande do Sul, Caixa Postal 1953, 90001 Porto Alegre, RS, Brasil

ABSTRACT

A total of 201 individuals, descendents of African slaves who escaped and formed an independent community at the margins of the Trombetas and Cuminá rivers, were studied in relation to 16 genetic systems (two blood groups, hemoglobin, eight erythrocyte enzymes and five serum proteins). Sixteen (59%;) of the 27 genetic markers studied showed frequencies that are typical of populations of African ancestry, with some admixture. The presence ofHB*S, CA2*2, ACP*R, GD*A, GD*A- and HP* 2M also pointed to a largely African gene pool. The quantitative estimate of admixture, using 11 of the systems which provided less heterogeneity, yielded 62%; Black, 11%; Indian and 27%; White ancestry. Previous estimates of African mixture in populations of the Amazon region have provided much lower (13%; to 24%;) numbers. It is concluded that this community still keeps much of its ancestral characteristics, despite the process of racial admixture that is occurring there and almost everywhere else in Brazil.

Keywords: breakdown; Amazonia.

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