White on the father’s side, black on the mother’s side

Researchers have retrieved the genetic history of people who live in quilombo remnants in São Paulo State, Brazil.

By Peter Moon  |  Agência FAPESP – The largest number of quilombo remnants in São Paulo State, Brazil, are found in the Ribeira Valley. Quilombos were communities founded by runaway or abandoned African slaves. Relics of dozens of these communities established during the first half of the nineteenth century still exist.

The former quilombos in São Paulo are now neighborhoods of Eldorado and Iporanga, cities located approximately 220 km southwest of the state capital. One of the most comprehensive population genetics surveys ever conducted in Brazil began in these communities in the year 2000.

“The communities we studied are true relicts of the Brazilian miscegenation process. We succeeded in retrieving the genetic history of four to five generations living in these quilombo remnants,” said geneticist Lilian Kimura.

The study has resulted in the publication of several scientific articles, the most recent of which describes a genetic investigation of the pool of quilombo Y chromosomes. The Y chromosome is unique to males and can be used to trace paternal ancestry.

Kimura is first author of the article, which was published in the American Journal of Human Biology. The principal investigator was Regina Célia Mingroni-Netto, a professor in the University of São Paulo’s Bioscience Institute (IB-USP) and supervisor of Kimura’s master’s, PhD and postdoctoral research, all of which was funded by scholarships from FAPESP.

Samples from 289 individuals living in quilombo remnants were genotyped using a set of 17 markers on the Y chromosome. The researchers identified 95 Y chromosome haplotypes, gene sets inherited together from a single parent. These were grouped together into 15 haplogroups.

They found that approximately 65% of the Y chromosomes in the communities studied were of European origin, 32% were of African origin, and 6% were of Native American origin. This means that most of the men are the descendants of male slaves born to female slaves impregnated by their owners.

In other words, European ancestry accounts for two-thirds of the quilombo paternal line. These findings match the pattern observed in other populations derived from African slaves in Brazil and the United States, where the European patrilineal origin is predominant. 

Inferring the origin of Y chromosomes in former quilombos is only the tip of the iceberg for this research project, which has revealed much more. The results of the Y chromosome analysis differ from those presented in studies of matrilineal ancestry in the ex-quilombo communities of the Ribeira Valley, which will also be published. Maternal genetic heritage is investigated by analyzing mitochondrial DNA, which is passed down from mothers to both sons and daughters.

“These communities’ mitochondrial DNA is predominantly African, although a significant percentage is Native American,” Mingroni-Netto said. Practically no European mitochondrial DNA was detected. None of the mothers of the slaves who founded these quilombos were white.

“Genetics, genealogy and interviews enabled us to detect five main male founding haplotypes, which explain 27.7% of the ancestry of the Y chromosomes in the Ribeira Valley quilombo remnants,” Kimura said.

The study was conducted under the aegis of the Human Genome and Stem Cell Research Center (HUG-CELL), one of the Research, Innovation and Dissemination Centers supported by FAPESP.

Founders of the quilombos

The five main haplotypes originated with the men who founded the quilombos and whose descendants are still alive. Any haplotypes of other founders who do not have surviving descendants have been lost.

The main founders of the quilombos were five men who lived during the first half of the nineteenth century. They are assumed to have been runaway or freed slaves who settled in the region and may or may not have been accompanied by women who were also African slaves, although in some cases the women would have been Native Americans.

Over time, the quilombos grew and were joined by more runaway or freed slaves. There was also a small amount of miscegenation with Native Americans who inhabited the Ribeira Valley, hence their 6% share of the patrilineal ancestry.

Haplotype H16A appears most frequently in two communities. It occurs in 61.9% of the Y chromosome samples from the Galvão neighborhood and 22.7% in samples from São Pedro. This concentration accords with genealogical and historical surveys using data from church baptism records and land title deeds in registries. 

By combining genetic data, historical data and individuals’ oral narratives, the researchers were able to infer that the haplotype H16A very probably corresponded to a Y chromosome inherited from Bernardo Furquim.

A study of black neighborhoods in the Ribeira Valley region found that Furquim was a runaway slave whose true name was Bernardo Machado dos Santos. He changed his name to conceal his identity from his pursuers.

The first record of land in his name dates from 1856. Baptism records in Eldorado show Bernardo baptizing children born to two women between 1856 and 1871. In these documents, both he and the women are called ‘freed blacks’.

“Bernardo Furquim is the most emblematic figure for these communities. Most of the inhabitants of Galvão and São Pedro are his descendants. He’s said to have sired 24 children. Some accounts refer to more than 100,” Kimura said.

“Furquim had families with several women and registered land in his name. He put each wife in a different house. The ruins can still be seen there.”

As in the case of Furquim, the genetic investigation conducted in parallel with historical research enabled the scientists to identify four other founders of quilombos, each with higher frequencies in a specific neighborhood.

“The initial aim of the project in 2000 was to study genetic disease inheritance and dynamics among the populations of former quilombo,” Mingroni-Netto said. “We expected to find in these isolated communities a higher frequency of genetic disorders as well as rare diseases caused by genetic mutations that only existed there.”

Genealogical details and clinical patient records for 1,500 individuals were surveyed between 2000 and 2003. The researchers then selected between 660 and 700 men and women to provide blood samples for the genetic study.

The genetic analysis did not produce any evidence of unknown genetic anomalies. “On the other hand, increased frequencies were detected for modern diseases, such as obesity and hypertension,” Mingroni-Netto said.

The individuals with detected diseases were given health counseling. “We explained to these people that they had asymptomatic high blood pressure or alerted mothers to the fact that their children were anemic,” she explained.

The main type of anemia found in quilombo remnants is sickle cell anemia, a hereditary disease that most frequently afflicts people of African heritage, although it can also occur in descendants of Europeans. A mutated form of hemoglobin distorts the red blood cells, normally rounded and elastic, into a crescent shape similar to a sickle and hardens them, hindering their passage through the small blood vessels and, hence, impairing tissue oxygenation.

Sickle cell anemia is caused by a genetic mutation. The disease only occurs if the individual is homozygous, i.e. if the altered gene is transmitted by both the father and the mother. If it is transmitted by only one parent, the offspring will have the sickle cell trait, which they can pass on to their own descendants, but will not develop the disease.

“All individuals found to have the sickle cell trait or full-blown sickle cell anemia were given medical and genetic guidance by the team,” Mingroni-Netto said. 

Heterozygous individuals, who have only one copy of the defective gene, never develop the disease but can pass on the genetic mutation to their children. “In these cases, we told the person they had the defective gene,” she added.

Articles:

“Inferring paternal history of rural African-derived Brazilian populations from Y chromosomes” (doi: 10.1002/ajhb.22930) by Lilian Kimura, Kelly Nunes, Lúcia Inês Macedo-Souza, Jorge Rocha, Diogo Meyer & Regina Célia Mingroni-Netto, American Journal of Human Biology, 2017: onlinelibrary.wiley.com/doi/10.1002/ajhb.22930/abstract.

“Genomic ancestry of rural African-derived populations from Southeastern Brazil” (doi: 10.1002/ajhb.22335) by Lilian Kimura, Elzemar Martins Ribeiro-Rodrigues, Maria Teresa Balester de Mello Auricchio, João Pedro Vicente, Sidney Emanuel Batista Santos & Regina Célia Mingroni-Netto, American Journal of Human Biology, 2013: onlinelibrary.wiley.com/doi/10.1002/ajhb.22335/abstract.

“Frequency and origins of hemoglobin S mutation in African-derived Brazilian populations”, by De Mello Auricchio MT, Vicente JP, Meyer D & Mingroni-Netto RC, Human Biology, 2007: ncbi.nlm.nih.gov/pubmed/18494376.