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Africa in the genes of the Brazilian people

DNA analysis reveals regions that better fed the slave traffic into the country

eduardo cesarDuring a little more than three centuries of black slave traffic the stretch of Western Africa that runs from Senegal to Nigeria possibly provided many more slaves to Brazil than was imagined. The proportion of men to women captured in this region and sent by force of arms here may have been higher – and considerably – than the 10% of the total estimated years ago by the American historians, Herbert Klein and David Eltis, scholars of slave trafficking across the Atlantic. The arguments that now serve to support a revision of the calculations, especially for the Southeast of Brazil, are not only historic, but genetic. By analyzing the genetic make up of people who live in three Brazilian capital cities, the geneticists Sérgio Danilo Pena and Maria Cátira Bortolini are helping to rescue part of this history as yet not totally clarified about the origin of almost 5 million African slaves who arrived at the ports of Rio de Janeiro, Salvador and Recife and have contributed to the formation of the Brazilian people.

In two recently concluded studies the team led by Pena, from the Federal University of Minas Gerais (UFMG), and by professor Maria Cátira, from the Federal University of Rio Grande do Sul (UFRGS), compared the pattern of genetic alterations shared by Africans and Brazilians. In this manner, they managed to estimate the participation of the different African regions in sending slaves to Brazil, the last country in Latin America to abolish slavery with the signing of the Aurea Law on the 13th of May 1888.

The results confirmed that the regions of Africa were three – West, Central-West and Southeast – that exported the African workforce to the country until 1850, when the Minister of Justice of the Emperor Eusébio de Queirós formulated a law making it a crime to traffic slaves. Up until now, nothing very new, and the genetic results merely confirmed the historical information with respect to one of the cruelest situations that one human being could submit upon another. It was already known that Brazil was one of the few, if not the only one of the countries of the Americas to receive Africans of all origins.

The new revelation is the greater involvement of black slave trafficking from Western Africa, also known as the West Coast, the region where the peoples such as the Yoruba, Jeje and the Males came from, who exercised strong social and cultural influence on the Brazilian Northeast, especially Bahia.

During the three centuries in which the Portuguese controlled the slave traffic across the Atlantic – the oldest, of longest duration and greatest in numerical terms -, the proportion of slaves embarked from the West, the Central-West and the Southeast of Africa oscillated considerably. By evaluating the records of African crossings, Herbert Klein, from Columbia University, and David Eltis, from Emory University, calculated that, in total, 10% of the slaves had come from the West region of Africa and 17% from the Southeast.

The principal slave supplier would indeed have been the Central-West, where the Portuguese colony of Angola was located, which would have contributed some 73% of the Africans sent to Brazil piled up in the holds of small ships. “Data about slave trading is still incomplete and the historians accept that the greater part came from the region of Angola”, comments Marina Mello Souza, from the University of São Paulo (USP), a specialist in African history.

Aware that the records of voyages did not always reflect the past with precision, over the last few years historians have gone on to fall back on genetics in an attempt to better understand what in fact occurred. “Our previous estimates based themselves on partial samples”, said Klein to Pesquisa FAPESP.

“We’re reviewing these projections, based on the work of geneticists and on the revision of voyage data that David Eltis’ team has been investigating at Emory University.” And, on this point, the work of Pena and Maria Cátira could complement this historical re-examination. The analysis of the genetic material shared by Brazilians and Africans has revealed that the proportion of slaves originating from West Africa – between Senegal and Nigeria – may have been two to four times greater than that accounted for up until now, much closer to the numbers exported from Angola.

Origins and destinies
Superior to that expected, the West African contribution was probably not distributed equally through the country. Pena and his doctorate student Vanessa Gonçalves have analyzed blood samples of 120 São Paulo born people who classify themselves and their parents and grandparents as being black, following the nomenclature adopted by the Brazilian Geography and Statistics Institute (IBGE), which groups Brazilians into whites, blacks and mulattos – the Afro-descendent movements in general use the word Negro to refer to blacks and mulattos.

Four out of every ten São Paulo  blacks presented genetic material typical of West Africa. This proportion, however, was smaller Rio de Janeiro and in Rio Grande do Sul, according to the article from the UFRGS team to be published in the American Journal of Physical Anthropology. Of the 94 black Rio de Janeiro tested by Maria Cátira and Tábita Hünemeier, 31% carried in their blood the genetic signature of West Africa, presented by only 18% of the 107 black Gauchos. As well as indicating origins and destinies, this data perhaps explains the heterogenic penetration in the country of candomblé (Afro-Brazilian religion), a religion with important Yoruba and Jeje cultural traces.

MIGUEL BOYAYANIn the search for the origins of the Brazilian people, it is not only the historians who resort to genetic findings. Also the geneticists need, from time to time, to return to history, sociology or anthropology books in order to understand what the genetic characteristics show them. At least one historical fact helps to understand why the proportion of blacks with West African origin is higher in São Paulo than in Rio or Porto Alegre. During the 16th and 17th centuries the Africans coming from the West arrived in the ports of Salvador and Recife for thereafter to be sold to the sugar plantation owners of the Northeast.

Later, however, the decline of the sugar economy led to the displacement of the slave work force to the coffee plantations that flowered in the State of São Paulo. Before this internal migration, between the end of the 18th century and the beginning of the 19th century, São  Paulo had already presented a concentration of slaves from West Africa much higher than in the remainder of the country. According to Klein, the reasons for this difference are still not completely understood, but perhaps can be partially explained by the importing of the work force directly from West Africa.

Maria Cátira explained the lower proportion of genetic material typical of West Africa among the blacks of Porto Alegre by the fact that the slaves arrived in the south of the country by an indirect way: 80% of the African work force of Rio Grande do Sul came from Rio de Janeiro, where the presence of the West African peoples was smaller than that in the Brazilian Northeast. Even at that it appears in the genetic composition of the black Brazilians that the most intense traffic to the country was slaves from Angola, in the Central-West of Africa. A smaller proportion (12%), but still significant, came from the region of Mozambique, in the Southeast, mainly after England went on to control more rigidly the embarking ports on the Atlantic coast of Africa.

Female presence
The African contribution for the genetic composition of the Brazilian was not unequal only from the geographical point of view. While the African men were the arms and legs that moved the sugar economy in the Northeast, the women exercised a special charm, of a sexual nature, over the plantation owners of European origin, as the sociologist for the State of Pernambuco, Gilberto Freyre, recorded in 1933 in his book entitled, Casa-grande & senzala (The masters and the slaves), the classic essay about the country’s formation. For this reason the Brazilian black guards today in his genetic material a greater contribution from women than from African men, although the volume of male traffic had been greater.

This inequality, which the geneticists call sexual asymmetry, becomes evident when one compares the two types of genetic material. The first is the DNA found in the mitochondria, energy plants located on the periphery of the cells. Transmitted by the mothers to the children of both sexes, the so called mitochondrial DNA allows one to know the geographical origin of the person’s maternal lineage. The second type of genetic material studied is the Y chromosome, which fathers pass only to their male sons and serves as an indicator of paternal lineage.

Pena’s team verified that 85% of the blacks of São Paulo had African mitochondrial DNA, whilst only 48% had presented the Y chromosome characteristic of Africa. In a similar manner, the group coordinated by Maria Cátira noted that, in 90% of the Rio de Janeiro and 79% of the Porto Alegre blacks, the African genetic material was of maternal origin. On the paternal side, only 56% of the Rio de Janeiro and 36% of the Porto Alegre blacks had paternal genetic material typical of Africa. “These numbers prove the story of sexual exploration of slaves by the whites”, comments Pena, “a not very pretty picture because it was based on a relationship of power”.

MIGUEL BOYAYANThis sexual asymmetry confirmed by genetics had previously been documented and detailed by the historian Sérgio Buarque de Holanda, in his book entitled, Raízes do Brasil [Roots of Brazil]; by the anthropologist Darcy Ribeiro, in his work entitled, O povo brasileiro [The Brazilian People], as well as in the books of Gilberto Freyre. It became incontestable when Pena and Maria Cátira began some ten years ago, in parallel and complementing studies, their investigation into the genetic formation of Brazilian whites and blacks with the help of mitochondrial DNA and the Y chromosome.

The first evidence that the Brazilian had carried in his cells the genetic material of Indians, Africans and Europeans sprung up in April of 2000, when the country commemorated the five centuries of the arrival of the Portuguese colonizers to this side of the Atlantic Ocean or the 500 years of the discovery of Brazil. Making use of this opportune date, Pena published – first in the magazine Ciência Hoje, a scientific magazine, and afterwards in the academic periodical American Journal of Human Genetics – the study that was called “Molecular portrait of Brazi”?. In this study, with 200 Brazilians from the North, Northeast, Southeast and South regions, the UFMG geneticist verified that, in reality, 33% descend from Indians on the part of the mother and 28% from Africans. In another study, published in 2001, it was shown that 98% of the whites descended from Europeans on the paternal side. Obviously the collaboration of the Indians and Negroes varied in accordance with the country’s region.

This was the genetic demonstration that had already been known from the historical, sociological and anthropological points of view. The first groups of European colonizers who arrived in Brazil after 1500 were formed almost exclusively by men. Thousands of kilometers distant from home, they had children with the Indians. Much later, with the arrival of slaves during the sugarcane economic cycle, they went on to also make the Africans pregnant.

The analysis of the genetic material from blacks carried out by Pena and Maria Cátira reinforced these results: 85% of Brazilian blacks have a female African ancestor, but the African men are represented in only 47% of the blacks – the remainder have European ancestors in their paternal lineage. “This is the other side of the coin”, advised professor Pena.

Molecular portrait
But what in fact do the mitochondrial DNA and the Y chromosome truly reveal? This depends. They are genetic tools fundamental for determining the composition of a population because they are blocks of DNA that do not mix with other genes and pass unaltered from one generation to another. But this genetic material contains very little information about the physical characteristics of an individual. To have African mitochondrial DNA, for example, only indicates that at some moment in the past – recent or not – there was an African woman in the maternal lineage of that person. And it is for this reason that someone with blond hair and blue eyes could have among their ancestors a dark skinned African, and as well a dark skinned and curly haired man could be a descendant of Europeans.

In an attempt to detail out this situation, Pena decided to investigate a third type of genetic material: the so called autossomic DNA, which is found in the nucleus of almost all of the body’s cells. Professor Pena and researcher Flavia Parra selected ten strips of autossomic DNA typical of African populations and created a scale called the African Ancestral Index: the more of these strips a person possesses, the closer the person is to being an African. Next, they went to look for them in the Brazilian population. The researchers from Minas Gerais State tested this index on 173 white, black and mulatto men in the town of Queixadinha, in the interior of Minas Gerais, and found that, on average, the three groups presented similar proportions of ancestral African, which were intermediate between that of a Portuguese from Porto, in Portugal, and of an African from the Saint Thomas Island, on the west coast of Africa.

In another study, Pena and the biologist Luciana Bastos-Rodrigues analyzed 40 other strips of autossomic DNA and discovered that they are sufficient to distinguish an African individual from another European or indigenous native of the Americas. On comparing these same strips in 88 Brazilian whites and 100 blacks with those of Africans, Europeans and indigenous Indians, Pena and biologist Luciana observed high levels of genetic mixing: both the whites and the blacks presented genetic characteristics of the Europeans and Africans. This mixture was even more evident among the blacks, who, in the opinion of professor Pena, “result from a process of intensive miscegenation”.

Based on the results obtained over the ten years of investigation into Brazilian genetic characteristics, Pena and Maria Cátira have no doubt in saying that, at least in the Brazilian case, it does not make the slightest sense to talk about races, since skin color, determined by only 6 of the almost 30,000 human genes, does not permit one to know who were the ancestors of a person.

The Brazilian geneticist Marcelo Nóbrega, from the University of Chicago, in the United States, agrees, although he says that the genetic differences between populations on distinct continents can be useful in the medical area – as it can indicate different capabilities to metabolize medicines – and used to define race. “This does not mean that the races are profoundly different among each other nor is one superior to another”, he says. For him, the increase in miscegenation over the last few centuries has eroded the divisions between the groups, as in the Brazilian case, and should turn obsolete the genetic concept of races.

As already stated by Gilberto Freyre in Casa-grande & senzala [The masters and the slaves], “every Brazilian, even the white, with blond hair, brings in his soul, when not in the soul and in the body – there are lots of people from a ‘jenipap tree’ or with a Mongolian feature around Brazil -, the shadow, or at least some characteristics of an indigenous or black person”.