Afro-Brazilian - Genetic Studies

Genetic Studies

A recent genetic study of Black Brazilians made for BBC Brasil analysed the DNA of self-reported Blacks from São Paulo.

The research analyzed the mitochondrial DNA (mtDNA), that is present in all human beings and passed down with only minor mutations through the maternal line. The other is the Y chromosome, that is present only in males and passed down with only minor mutations through the paternal line. Both can show from what part of the world a matrilineal or patrilineal ancestor of a person came from, but one can have in mind that they are only a fraction of the human genome, and reading ancestry from Y chromosome and mtDNA only tells 1/23rd the story, since humans have 23 chromosome pairs in the cellular DNA.

Analyzing the Y chromosome, which comes from male ancestors through paternal line, it was concluded that half (50%) of Brazilian black population have at least one male ancestor who came from Europe, 48% have at least on male ancestor who came from Africa and 1.6% have at least one male ancestor who was a Native American. Analyzing their mitochondrial DNA, that comes from female ancestors though maternal line, 85% of them have at least one female ancestor who came from Africa, 12.5% have at least one female ancestor who was Native American and 2.5% have at least one female ancestor who came from Europe.

The high level of European ancestry in black Brazilians through paternal line exists because, for much of Brazil's History, there were more Caucasian males than Caucasian females. So inter-racial relationships between Caucasian males and Sub-Saharan African or Native American females were widespread.

Over 75% of Caucasians from North, Northeast and Southeast Brazil would have over 10% Sub-Saharan African genes, according to this particular study. Even Southern Brazil that received a large group of European immigration, 49% of the Caucasian population would have over 10% Sub-Saharan African genes, according to that study. Thus, 86% of Brazilians would have at least 10% of genes that came from Africa. The researchers however were cautious about its conclusions: "Obviously these estimates were made by extrapolation of experimental results with relatively small samples and, therefore, their confidence limits are very ample". A new autosomal study from 2011, also led by Sérgio Pena, but with nearly 1000 samples this time, from all over the country, shows that in most Brazilian regions most Brazilians "whites" are less than 10% African in ancestry, and it also shows that the "pardos" are predominantly European in ancestry, the European ancestry being therefore the main component in the Brazilian population, in spite of a very high degree of African ancestry and significant Native American contribution. Other autosomal studies (see some of them below) show a European predominance in the Brazilian population.

Another study (based on blood polymorphisms, from 1981) carried out in one thousand individuals from Porto Alegre city, Southern Brazil, and 760 from Natal city, Northeastern Brazil, found whites of Porto Alegre had 8% of African alleles and in Natal the ancestry of the samples total was characterized as 58% White, 25% Black, and 17% Amerindian". This study found that persons identified as White or Pardo in Natal have similar ancestries, a dominant European ancestry, while persons identified as White in Porto Alegre have an overwhelming majority of European ancestry.

According to an autosomal DNA genetic study from 2011, both "whites" and "pardos" from Fortaleza have a predominantly degree of European ancestry (>70%), with minor but important African and Native American contributions. "Whites" and "pardos" from Belém and Ilhéus also were found to be pred. European in ancestry, with minor Native American and African contributions.

According to another study conducted on a school in the poor periphery of Rio de Janeiro, autosomal DNA study (from 2009), the "pardos" there were found to be on average over 80% European, and the "whites" (who thought of themselves as "very mixed") were found out to carry very little Amerindian and/or African admixtures. "The results of the tests of genomic ancestry are quite different from the self made estimates of European ancestry", say the researchers. In general, the test results showed that European ancestry is far more important than the students thought it would be. The "pardos" for example thought of themselves as 1/3 European, 1/3 African and 1/3 Amerindian before the tests, and yet their ancestry was determined to be at over 80% European. The "blacks" (pretos) of the periphery of Rio de Janeiro, according to this study, thought of themselves as predominantly African before the study and yet they turned out predominantly European (at 52%), the African contribution at 41% and the Native American 7%.

According to another autosomal DNA study (see table), those who identified as Whites in Rio de Janeiro turned out to have 86.4% – and self identified pardos 68.1% – European ancestry on average (autosomal). Pretos were found out to have on average 41.8% European ancestry

Another study (autosomal DNA study from 2010) found out that that European ancestry predominates in the Brazilian population as a whole ("whites", "pardos" and "blacks" altogether). European ancestry is dominant throughout Brazil at nearly 80%, except for the Southern part of Brazil, where the European heritage reaches 90%. "A new portrayal of each ethnicity contribution to the DNA of Brazilians, obtained with samples from the five regions of the country, has indicated that, on average, European ancestors are responsible for nearly 80% of the genetic heritage of the population. The variation between the regions is small, with the possible exception of the South, where the European contribution reaches nearly 90%. The results, published by the scientific magazine 'American Journal of Human Biology' by a team of the Catholic University of Brasília, show that, in Brazil, physical indicators such as skin colour, colour of the eyes and colour of the hair have little to do with the genetic ancestry of each person, which has been shown in previous studies"(regardless of census classification) "Ancestry informative SNPs can be useful to estimate individual and population biogeographical ancestry. Brazilian population is characterized by a genetic background of three parental populations (European, African, and Brazilian Native Amerindians) with a wide degree and diverse patterns of admixture. In this work we analyzed the information content of 28 ancestry-informative SNPs into multiplexed panels using three parental population sources (African, Amerindian, and European) to infer the genetic admixture in an urban sample of the five Brazilian geopolitical regions. The SNPs assigned apart the parental populations from each other and thus can be applied for ancestry estimation in a three hybrid admixed population. Data was used to infer genetic ancestry in Brazilians with an admixture model. Pairwise estimates of F(st) among the five Brazilian geopolitical regions suggested little genetic differentiation only between the South and the remaining regions. Estimates of ancestry results are consistent with the heterogeneous genetic profile of Brazilian population, with a major contribution of European ancestry (0.771) followed by African (0.143) and Amerindian contributions (0.085). The described multiplexed SNP panels can be useful tool for bioanthropological studies but it can be mainly valuable to control for spurious results in genetic association studies in admixed populations." It is important to note that "the samples came from free of charge paternity test takers, thus as the researchers made it explicit: "the paternity tests were free of charge, the population samples involved people of variable socioeconomic strata, although likely to be leaning slightly towards the ‘‘pardo’’ group". According to it the total European, African and Native American contributions to the Brazilian population are:

In support of the dominant European heritage of Brazil, according to another autosomal DNA study (from 2009) conducted on a school in the poor periphery of Rio de Janeiro the "pardos" there were found to be on average over 80% European, and the "whites" (who thought of themselves as "very mixed") were found out to carry very little Amerindian and/or African admixtures. "The results of the tests of genomic ancestry are quite different from the self made estimates of European ancestry", say the researchers. In general, the test results showed that European ancestry is far more important than the students thought it would be. The "pardos" for example thought of themselves as 1/3 European, 1/3 African and 1/3 Amerindian before the tests, and yet their ancestry was determined to be at over 80% European. The "blacks" (pretos) of the periphery of Rio de Janeiro, according to this study, thought of themselves as predominantly African before the study and yet they turned out predominantly European (at 52%), the African contribution at 41% and the Native American 7%.

According to another autosomal DNA study from 2009, the Brazilian population, in all regions of the country, was also found out to be predominantly European: "all the Brazilian samples (regions) lie more closely to the European group than to the African populations or to the Mestizos from Mexico". According to it European ancestry was the main component in all regions of Brazil: Northeast of Brazil (66.7% European 23.3% African 10.0% Amerindian) Northern Brazil (60.6% European 21.3% African 18.1% Amerindian) Central West (66,3% European 21.7% African 12.0% Amerindian) Southeast Brazil (60.7% European 32.0% African 7.3% Amerindian) Southern Brazil (81.5% European 9.3% African 9.2% Amerindian). According to it the total European, African and Native American contributions to the Brazilian population are:

An autosomal study from 2011 (with nearly almost 1000 samples from all over the country, "whites", "pardos" and "blacks" included) has also concluded that European ancestry is the predominant ancestry in Brazil, accounting for nearly 70% of the ancestry of the population: "In all regions studied, the European ancestry was predominant, with proportions ranging from 60.6% in the Northeast to 77.7% in the South". The 2011 autosomal study samples came from blood donors (the lowest classes constitute the great majority of blood donors in Brazil), and also public health institutions personnel and health students. In all Brazilian regions European, African and Amerindian genetic markers are found in the local populations, even though the proportion of each varies from region to region and from individual to individual. However most regions showed basically the same structure, a greater European contribution to the population, followed by African and Native American contributions: “Some people had the vision Brazil was a heterogeneous mosaic Our study proves Brazil is a lot more integrated than some expected". Brazilian homogeneity is, therefore, greater within regions than between them:

According to another study from 2008, by the University of Brasília (UnB), European ancestry dominates in the whole of Brazil (in all regions), accounting for 65,90% of the heritage of the population, followed by the African contribution (24,80%) and the Native American (9,3%).

According to an autosomal DNA study (from 2003) focused on the composition of the Brazilian population as a whole, "European contribution is highest in the South (81% to 82%), and lowest in the North (68% to 71%). The African component is lowest in the South (11%), while the highest values are found in the Southeast (18%-20%). Extreme values for the Amerindian fraction were found in the South and Southeast (7%-8%) and North (17%-18%)". The researchers were cautious with the results as their samples came from paternity test takers which may have skewed the results partly.

Several other older studies have suggested that European ancestry is the main component in all Brazilian regions. Several other older studies have suggested that European ancestry is the main component in all Brazilian regions. A study from 1965, Methods of Analysis of a Hybrid Population (Human Biology, vol 37, number 1), led by the geneticists D. F. Roberts e R. W. Hiorns, found out the average the Northeastern Brazilian to be predominantly European in ancestry (65%), with minor but important African and Native American contributions (25% and 9%). A study from 2002 quoted previous and older studies (28. Salzano F M. Interciêência. 1997;22:221––227. 29. Santos S E B, Guerreiro J F. Braz J Genet. 1995;18:311––315. 30. Dornelles C L, Callegari-Jacques S M, Robinson W M, Weimer T A, Franco M H L P, Hickmann A C, Geiger C J, Salzamo F M. Genet Mol Biol. 1999;22:151––161. 31. Krieger H, Morton N E, Mi M P, Azevedo E, Freire-Maia A, Yasuda N. Ann Hum Genet. 1965;29:113––125. ), saying that: "Salzano (28, a study from 1997) calculated for the Northeastern population as a whole, 51% European, 36% African, and 13% Amerindian ancestries whereas in the north, Santos and Guerreiro (29, a study from 1995) obtained 47% European, 12% African, and 41% Amerindian descent, and in the southernmost state of Rio Grande do Sul, Dornelles et al. (30, a study from 1999) calculated 82% European, 7% African, and 11% Amerindian ancestries. Krieger et al. (31, a study from 1965) studied a population of Brazilian northeastern origin living in São Paulo with blood groups and electrophoretic markers and showed that whites presented 18% of African and 12% of Amerindian genetic contribution and that blacks presented 28% of European and 5% of Amerindian genetic contribution (31). Of course, all of these Amerindian admixture estimates are subject to the caveat mentioned in the previous paragraph. At any rate, compared with these previous studies, our estimates showed higher levels of bidirectional admixture between Africans and non-Africans."

• Crioulo (Brazilian born) slaves
• Slave women from various African regions wearing European-style hairdressing
• African slaves from Monjolo, Elmina, Mozambique, Benguela e Calava

In 2007 BBC Brasil launched the project Raízes Afro-Brasileiras (Afro-Brazilian Roots), in which they analyzed the genetic ancestry of nine famous Brazilian blacks and "pardos". Three tests were based on analysis of different parts of their DNA: an examination of paternal ancestry, maternal ancestry and the genomic ancestry, allowing to estimate the percentage of African, European and Amerindian genes in the composition of an individual.

Of the 9 people analyzed, 3 of them had more European ancestry than African one, while the other 6 people had more African ancestry, with varying degrees of European and Amerindian admixture. The African admixture varied from 19.5% in actress Ildi Silva to 99.3% in singer Milton Nascimento. The European admixture varied from 0.4% in Nascimento to 70% in Silva. The Amerindian admixture from 0.3% in Nascimento to 25.4% in soccer player Obina.

• Sandra de Sá is: 96.7% African, 2.1% European and 1.1% Amerindian
• Seu Jorge is: 85.1% African, 12.9% European and 2% Amerindian
• Djavan is: 65% African, 30.1% European and 4.9% Amerindian
• Obina is: 61.4% African, 25.4% Amerindian and 13.2% European
• Daiane dos Santos is: 40.8% European, 39.7% African and 19.6% Amerindian
• Neguinho da Beija-Flor is: 67.1% European, 31.5% African and 1.4% Amerindian