Differential contribution of indigenous men and women to the formation of an urban population in the Amazon region as revealed by mtDNA and Y-DNA

The human populations of the Brazilian Amazon were formed by interethnic cr osses between Europeans, Africans, and Amerindians. The relative contributi on of men and women of different ethnic groups was not homogeneous, since t he social policies of the first three centuries of Brazilian colonization e ncouraged mating between European men and indigenous women and, later on, A frican women. In order to test this model based on historical data, we comp ared the relative contribution of the Y-DNA and mtDNA of Amerindian and non -Amerindian populations to the formation of the urban population of the tow n of Belem, in the Amazon region, on the basis of a C-T mutation at locus D YS199 present in 90% of the Amerindian Y-DNA and of five markers that defin e 99% of the mitochondrial sequences of Amerindians. The contribution of in digenous men to the formation of this population was less than 5%, whereas the contribution of indigenous women was estimated at more than 50% of the mitochondrial sequences of the same population. Thus, the present results d emonstrate that the contribution of indigenous women to the formation of th e Belem population was 10 times higher than the contribution of indigenous men, a genetic consequence of social behavior and attitudes of the past; ou r results also help clarify the process of integration of indigenous commun ities into the urban societies in Brazil and possibly in other countries. ( C) 1999 Wiley-Liss, Inc.