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The support of genetics for the history of the Brazilian people

The study of DNA Shows the scope of miscegenation and brings together specialists from different fields

Genetics did not make its mark in history just by sequencing the genome of agricultural pests and the ongoing elucidation of the molecular structure of animals and plants. It also earned its place in history by explaining or confirming phenomena whose origins remained obscure, the composition and the migratory movements of the Brazilian and world populations. At the 46th National Genetics Congress held from September 19 to 23 in Águas de Lindóia (SP) specialists in various fields relinquished the specialized languages of their disciplines and, together, they decided to find answers to common problems. Besides geneticists and historians, geographers, linguists, agronomic engineers, ecologists, botanists, medical doctors, archeologists and even architects were all present. But it worked.

The geneticist Lynn Jorde, of the University of Utah, in the United States, exemplified the scope of this interaction between scientific fields in the first conference of the Congress. “Humankind’s origin really is in Africa”, he pronounced, as a result of his analyses of the Y chromosomes (associated with paternal descent) and of the mitochondrial DNA (associated with the maternal line) of Asians, Europeans, and Africans. Naturally, there was no shortage of debate and talks on the state-of-the-art of genetics itself, molecular biology, evolution, conservation of forests, ethics in research and patents.

At the opening of the Congress, José Fernando Perez – a physicist with a doctorate in electronic engineering, who was kindly awarded the title (although informally) of geneticist – recounted the international repercussions of the Xylella Genome Project, of which he was one of the leading protagonists, as the scientific director of the FAPESP. It was an experience, which in his opinion, consolidated Brazilian scientific competence and confirmed an old impression: the best way of training researchers really is in Brazilian institutions. “Training doctors abroad is expensive and lengthy”, he said.

Two days later, the oncologist José Cláudio da Rocha, of the A.C. Camargo Cancer Hospital, sister institution of the Ludwig Institute, announced an advance in knowledge of the human genome: the discovery of four genetic mutations associated with hereditary breast cancer. In his view, it is not enough to examine specific regions of the three genes associated with the disease BRCA 1, BRCA 2 and P53. Practice has shown that the whole gene needs to be examined to find alterations. In his opinion, the study of the genetic characteristics of the Brazilian population, marked by intense miscegenation, should facilitate the prevention and treatment of health problems in general.

Under the topic of 500 Years of Genetic Mixing, the congress benefited from the participation of around 3,000 students, who brought a little more excitement  to this hill town of 18,000 inhabitants. This year, tribute was paid to the geneticist Warwick Estevam Kerr, for his scientific contribution and for his ability to set up teams (see interview on page 36).

In a demonstration that the biologists were ready to broaden their interpretations, not confining themselves to looking through the microscope alone, the geneticist Sérgio Danilo Pena, of the Federal University of Minas Gerais (UFMG), recognized, “When we do not understand some result in research, we turn to the history books”. Pena considers himself one of the first readers of O Povo Brasileiro (The Brazilian People), which came out in 1995 – not just because he is from the same part of Brazil as the author, the ethnologist Darcy Ribeiro (both are from Minas Gerais), but because the book offers an interpretation of the mixture of races in this country, on which he too is working. Last year, Pena completed a study of 200 white Brazilians showing that their paternal ancestral pattern was predominantly European, while the maternal was African or Amerindian (see Pesquisa FAPESP nº 52).

At the Congress, Pena announced that the results his team had obtained – previously confined to the middle and upper-middle classes – were confirmed by a study carried out this year with 180 rural dwellers in the Jequitinhonha Valley, one of the poorest regions of Brazil, located in the north of Minas Gerais and previously occupied by Aimoré Indians. “Skin color, in Brazil, says very little about genomes”, said Pena, who is himself a descendent of Indians.

The country’s first official census, carried out in 1872, clearly reflects this miscegenation. Out of a total population of 9.9 million people, mixed race people were in the majority (4.2 million). They were followed by whites (3.8 million), blacks (1.9 million), and Amerindians (440,000). The genetic mixture – or hybridization, as the geneticists would say – continues unabated. In the 1991 census, mixed race people represented 42% and blacks 5% of the population so that the self-described whites were only slightly in the majority (52%). But what are the consequences of this? The original genetic constitution of whites, blacks, and Indians tends to be lost. “From the genetic point of view, there simply are no more blacks like the Africans that arrived in Brazil”, noted the hematologist Marco Antonio Zago of the University of São Paulo (USP) at Ribeirão Preto. Since 1992, Zago has been running a team analyzing the genetic inheritance of a group of more than 400 blacks. An initial study involved urban blacks from Ribeirão Preto, using genetic markers associated with the origin of the mutation of one of the globulin genes, a protein formed in the region of chromosome 11 and leading to sickle cell anemia.

This study confirmed what historians already knew: Brazilian blacks are mostly Bantu (from the south and west of Africa). But initially some data did not tie up. In Belém do Pará, for example, there were fewer Bantus than expected. So Zago was one more who had to look up the history books to discover that many slaves from elsewhere were bought at the ports of Rio de Janeiro and taken to north. Another conclusion: Brazilian blacks have their own genetic characteristics, different from those in other parts of the Americas.

Genetics also picked out the invisible traces of miscegenation. “Even urban blacks who assured us that all four of their grandparents were black had a considerable contribution form other peoples”, commented Zago, based on the data of the surveys conducted by Wilson Araújo Silva Junior and Kiyoko Abe Sandes, under his guidance. There were genetic marks of Europeans (22% and Amerindians (6%). A study in progress in Serra and São Gonçalo (BA) more closed communities than the urban blacks, also recorded this type of genetic mixture. “We see signs of miscegenation even when selecting blacks at random”, says Zago.

Now history supports his theory. “Miscegenation was much more common in Brazil than in the United States”, said the US historian Herbert Klein, of Columbia University, whose talk on the slave trade kept the biologists in the audience on the edge of their seats. “Genetics”, he observed, “is a good starting point for history, because it shows the origins and mixture of the races”. It remains true, however, that at least two precautions have to be taken in overlapping specialties. The first is to remember that genetics has limits. It can only study present-day populations and is unable to analyze extinct ones. Another cautionary factor is the approach adopted. “Any attempt to find genetic norms based in European or US standards will not work”, warned Francisco Mauro Salzano, of the Federal University of Rio Grande do Sul (UFRGS), who is studying the origins and risks of genetic diseases in the native peoples of the Americas. In his view, a lot of effort still needs to be expended to establish clearly, what can be called the genetic portrait of Brazilians. “Ideally”, he recommended, “the portrayers should be Brazilian”.

From a broader standpoint, genetics has enabled us to reconstitute the movement of living beings on earth. “A billion years were needed before single cell organisms emerged and developed and another 3 billion years before the first traces of multicellular organisms appeared”, announced Antonio Rodrigues Cordeiro, of the Federal University of Rio de Janeiro (UFRJ). A specialist in evolution, he gave a striking example to illustrate his ideas: eyes developed independently in different animal species. “Four hundred million stages would be required for light sensitive cells to develop into a complete organ, assuming progress of 1% from one generation to the next”, he said.

According to Cordeiro, the similarity between the structure of the eyes of, let us say, a squid and a vertebrate “is extraordinary”. “The genes that go to make eyes are the same”, he pointed out. In other words, the nature of the proteins is the same; it is the function that is different. An example is the crystalline lens, as the crystalline proteins, the white part of the eye, are called. With their original functions modified, they do not attract and serve as inert and transparent filler for eye – the result of the transcription of genetic promoters and inhibitors. In microorganisms, the same proteins are related to the formation of reproductive structures, the spores. In crocodiles, they act as enzymes. The accumulated evidence led Cordeiro to develop a complementary theory to Darwinism. “The organism is not a plaything of natural evolution; it has its own rules and restrictions”, he said. “We are no longer governed by the same original evolutionary forces”.

At the Federal University of Viçosa (UFV), the veterinarians Simone Guimarães and Paulo Sávio Lopes are developing the Genome Identification in Pigs Program (Pigs). By next year, they intend to identify the genes responsible for growth, the tenderness of the meat and resistance to disease. They also intend to speed up genetic improvement and raise productivity.

But if there is a piece of research that in a way sums up the tendencies of the congress this year, it is the doctorate being undertaken by Fábio de Oliveira Freitas at USP’s Luiz de Queiroz College of Agriculture (Esalq). He worked with archeological samples of corn (Zea mays mays), found in the caves of the Vale do Peruaçu, between the towns of Januária and Itacarambi, in the northwest of Minas Gerais. These caves were used as human shelters from 10,000 years ago to the coming of the Europeans.

There inside, corncobs and grains – between 500 and 1,100 years old – were buried inside baskets together with beans (Phaseolus sp), cassava (Manihot esculenta), cotton (Gossypium), peanuts (Arachis hypogea), and peppers (Capsicum).To understand how this material got there, Freitas obtained samples of modern corn from Embrapa’s germ plasm bank at Sete Lagoas (MG), and collected varieties still used by Waura, in the Xingu National Park and Xavantes Indians (MT). Last year he went to the University of Manchester, in England, to extract and examine the DNA of all of them.

Freitas identified a region with three distinct sections (alleles) that enabled him to trace the route of the corn to Januária. Until then, it was thought that Brazilian corn probably came from the Andes. But he saw that this plant must have left the highlands of Mexico and Guatemala and arrived in the Andes around 5,000 years ago, without having spread to the lowlands of South America. It must have come to Januária only two thousand years ago directly from Central America.

Reading Archeology, undertaken since graduation, clarified things. The flow of seeds can be explained by human migratory movement, by the exchange of varieties between the ancient peoples of the Americas or by wars and territorial conquests. “There was little contact between the people of the north of Bolivia and Peru and the ancient people of Brazil, at least with regard to corn”, says the researcher.

The genetic standards of the past have remained. In most present-day samples, the genetic markers of the varieties from the highlands and the lowlands remain quite distant from one another. The result is now explained by the colonization of South America, with one side being colonized by the Spanish and the other side by the Portuguese, who kept this isolation. One concern remains with regard to genetic studies, expressed by João Stenghel Morgante, president of the Brazilian Genetics Society and the organizer of the event, “The discoveries of genetics, properly applied in an ethical and fair society, should remain one of humankind’s primary objectives”.