A complexidade da mistura racial no Brasil: A hemoglobina S como marcador étnico nas suas populações

Abstract

Black people and mulattoes constitute circa 45% of the Brazilian population, and there exists quite a controversy concerning the correct use of the terms Negro, Negroid or Afro-descendant to name this ethnic category. Since the hemoglobin S gene comes predominantly from African descendants, the study of this genetic disorder contributes greatly to the discussion of such a polemic matter. Recently we studied a sample of 817 heterozygous non-consanguineous individuals for the hemoglobin S gene (513 males and 304 females), aged between 18 and 65 years, voluntarily detected in the population of Campinas, State of São Paulo, Brazil. An analysis of the subjects showed that only 53% of the individuals' African ancestry was revealed by his/her phenotype. The gene composition of the individuals in this sample estimated the Negroid gene stock contribution as 45%, the Caucasoid gene stock contribution as 41% and the remaining 14% due to Amerindian gene stock. These data demonstrate that the wide miscegenation that has occurred in Brazil, as well as many internal and external migration streams have dissociated the hemoglobin S from the color of the skin of its carriers. In face of the diversity of criteria used in ethnic classifications, we choose to adopt the term Negroid in our research, which has been well established in Population Genetics, and which is also based upon objective definition criteria.