Mitochondrial DNA mapping of social-biological interactions in Brazilian Amazonian African-descendant populations

Abstract

The formation of the Brazilian Amazonian population has historically involved three main ethnic groups, Amerindian, African and European. This has resulted in genetic investigations having been carried out using classical polymorphisms and molecular markers. To better understand the genetic variability and the micro-evolutionary processes acting in human groups in the Brazilian Amazon region we used mitochondrial DNA to investigate 159 maternally unrelated individuals from five Amazonian African-descendant communities. The mitochondrial lineage distribution indicated a contribution of 50.2% from Africans (L0, L1, L2, and L3), 46.6% from Amerindians (haplogroups A, B, C and D) and a small European contribution of 1.3%. These results indicated high genetic diversity in the Amerindian and African lineage groups, suggesting that the Brazilian Amazonian African-descendant populations reflect a possible population amalgamation of Amerindian women from different Amazonian indigenous tribes and African women from different geographic regions of Africa who had been brought to Brazil as slaves. The present study partially mapped the historical biological and social interactions that had occurred during the formation and expansion of Amazonian African-descendant communities.

Paleogenetic Studies in Guajajara Skeletal Remains, Maranhão State, Brazil

“…In the present study, the samples were aligned and subjected to phylogenetic analyses with other groups of samples from previous mitochondrial studies [24,25,[45][46][47]. An NJ tree (Figure 2) of this data set gives tenuous support for separation into seven clusters.…”

“…Of these, only the mutations in bold are consensually accepted as haplogroup motifs. In order to assign the haplogroups, scientific articles [24,25,45,46,[54][55][56] and databases specialized in mtDNA analysis HaploGrep (http://haplogrep.uibk.ac.at/) and Phylotree (http://www.phylotree.org/) were used.…”

Afro-Derived Amazonian Populations: Inferring Continental Ancestry and Population Substructure

“…These studies demonstrate that, depending on the genetic marker used, the contribution of African genes in different communities can vary greatly and that the contribution of European and Amerindian genes is significant (Schneider et al 1987;Guerreiro et al 1999;Ribeiro-dos-Santos et al 2002;Carvalho et al 2008), implying that population stratification may be present in all Afro-derived communities studied. Stratification occurs when a population is formed from a relatively recent admixture of subpopulations (European, African, and indigenous, for example) and when the proportion of this admixture varies between the individuals that make it up (Hoggart et al 2003).…”

“…In Brazil, various studies have been conducted on Afro-derived groups in an attempt to estimate the contribution of parental populations to the formation of these populations, using classic genetic polymorphisms (Bortolini et al 1995;Arpini-Sampaio et al 1999;Guerreiro et al 1999), polymorphisms of nuclear DNA Silva Jr. et al 1999;Cayres-Vallinoto et al 2003); mitochondrial DNA markers Ribeiro-dos-Santos et al 2002;Carvalho et al 2008) and Y chromosome markers Kiyoko et al 2004). …”

“…The researchers involved in this study have conducted parallel research in at least six of the seven communities investigated here, using uniparental Y-DNA markers (nine STR loci-data available on the site www.yhrd.org) and mtDNA markers (Ribeirodos- Santos et al 2002;Carvalho et al 2008). The estimates obtained show very high (mean of 47%) Native American mtDNA and very low (mean of 5%) Native American Y-DNA contributions in the studied populations.…”