Análise hierárquica de marcadores bialélicos do Cromossomo Y e demografia histórica de populações quilombolas de Alagoas, Brasil

Abstract

The slave trade across the Atlantic brought an estimated four million Africans to Brazil since the beginning of the XVI century until mid-XIX century, thus contributing to the significant miscegenation of Brazil’s population. The current genetic condition is a result of the interbreeding process between the Native American (Amerindian), European populations and the African population. Presently, despite this population’s elevated heterogeneity, small isolated groups can still be found, as is the case of the Quilombolas, who are the product of the resistant movement against slavery imposed by Portuguese colonization. With the objective of conducting research of the genetic composition and the origin of paternal lineages in nine Afro-descendent communities of Alagoas, Brazil, 15 Y-SNP markers were analyzed by applying the SNaPshot (Applied Biosystems) method. Utilizing the updated nomenclature of the Y-Chromosome Phylogenetic Tree, it was possible to identify nine haplogroups of the Y-Chromosome in a total of 209 individuals. The calculated genetic diversity ranged from 0.2000 to 0.7190, thus evidencing against a standardized composition of this population. As a result of patriarchal domination of the Portuguese economic model of colonization in Brazil, haplogroup R1b1b2*-M269, of European origin, was observed in all populations at a frequency of 5.26 - 79.17%. Haplogroup F*(xK)-M213 was found at a rate of 4.17% and 36.84%, suggesting an origin of European male ancestry in these individuals. Seven populations corresponded to haplogroup E1b1a1*-M2, of Sub-Saharan African descent, which presented a frequency above Alagoas’ population diversity, varying from 13.3% to 90.0%. However, Q1a3a*-M3, of the Amerindian group was observed in only 2 chromosomes. Sub-clades of Haplogroup E, of African descent, including E1b1b1b1*M81, E1b1b1a1*-M78 and E1b1b1c*-M123 were considerably frequent among the Portuguese. Applying AMOVA test, occurrences of heterogeneity among Alagoas’ Quilombola population (FST=0.23964, P=0,00000±0,00000) were verified, had a genetic intrapopulation variation of 23.96%. The study revealed no significant genetic variances between populations from Alagoas, Rio de Janeiro, Portugal and the Quilombola populations of Jacu, Palmeira dos Negros, Paus Pretos, Poços do Lunga and Carrasco. However, Cajá dos Negros, Muquém, Filus and Povoado Cruz presented distinct genetic constituents, thereby highlighting the hypothesis that the aforementioned communities were originally places of refuge for slaves. An analysis of hierarchies pertaining to Y-SNP markers improved the basis of knowledge of Afro-descendant populations in Alagoas, and in union with historical and anthropological facts and demographics, establishes itself as an important instrument in the field of population genetics.