Investigando a diversidade genética da África Subsaariana e sua influência em outras populações

Abstract

Investigations on African populations are essential for understanding their complexity and the consequences of the dispersal of African peoples across the globe. One of the most important and impactful migratory events that reflects this context is the African Diaspora. In order to understand such events and the origins of some Afro-descendant populations in South America, the present study aimed to make a parallel between the past and present of African diaspora populations. For this purpose, populations from opposite sides of the Atlantic were investigated including ethnic groups from Nigeria and Zimbabwe, and quilombola populations from Alagoas and urban populations from Colombia. Uniparental lineage markers, mitochondrial DNA and Y chromosome, were analyzed in all of the samples, as well as a new Massively Parallel Sequencing panel. Higher genetic diversity values were found in African populations (from Nigeria and Zimbabwe) compared to those of the diaspora (quilombola and urban populations from Colombia). Although located in opposite sides of the continent, the results obtained from Nigerian and Zimbabwean studies revealed a shared matrimonial practice that results in substructure only in the paternal component (patrilocality). Meanwhile, in both diaspora population datasets, the high representation of Native American lineages indicates a history of coexistence, influence, and genetic exchange with local Indigenous populations. In these populations, a predominance of African maternal lineages and European paternal lineages was detected. These results are consistent with historical records regarding the tri-hybrid formation of populations on the continent. Significant genetic distances were found in comparisons among all quilombos. However, haplotype sharing between quilombos was also detected, indicating genetic similarities among these communities. Overall, the scenario observed in these communities suggests the presence of founding lineages in the quilombos and subsequent differentiation due to genetic drift effects. Phylogeographic analyses of the African lineages in diaspora populations revealed that they are the result of multiple migratory waves from Central-West, Southeast, and Southwest African nations, refuting the hypothesis of an almost exclusive regional African origin for the populations of Northeastern Brazil and the Colombian Caribbean. Due to the lack of information about the linguistic affiliations of African populations in existing studies, many inferences about the ethnic origins of Afro-descendant populations in South America could not be made. This highlights the negative impact of existing knowledge gaps regarding Africa and their repercussions in other fields of study. Thus, the results point to the African populations that had a massive influence on the diaspora, enabling the reconstruction of the lost history of the origins of these communities. At the same time, this thesis contributes with new data to fill these gaps and positively impacting future investigations on African genetic (and ethnic) diversity.