Knowing the genome of the Brazilian population helps to decipher its history

A study co-led by the Institute for Evolutionary Biology (IBE:CSIC-UPF) and the University of São Paulo within the ‘DNA do Brasil’ project has sequenced more than 2700 complete genomes of the Brazilian population. Unlike previous genomic studies, which presented information mainly from populations of European ancestry, this new study has emphasised the population variety of the country, including samples from different communities of the five regions of Brazil, from different origins.

The research, which has revealed more than 8 million previously unknown genetic variants, helps to decipher the country’s history. It makes it possible to trace, through genomic ancestries, the European colonisation of the 15th century, the forced migration of African communities as slaves to Brazil and the reduction of the native population. In this way, they have found that the north is dominated mainly by African ancestry, while the south is dominated by European ancestry.

They have also found that the majority of the mitochondrial lineage, inherited from the mother, is African or Aboriginal. In contrast, the Y chromosome lineage is predominantly European. This is explained by a historical asymmetric mating between communities, linked to violence during the colonisation by male European settlers, and a subjugation to colonial power in the 15^th century.

Of migration, genes and health

In addition, the team of Tábita Hünemeier, co-leader of the study, has focused on the implications for population health. The researchers have found more pathogenic (i.e. disease-linked) variants in native or African lineages, although they point out that this may be because the genomes of these populations are less well known as they are under-represented in global genetic databases. Indeed, Brazilian native populations are among the least studied in the world. On the other hand, the study describes the ‘founder effect’ as a possible cause for the higher prevalence of some diseases considered rare in Europe.

The research team has also identified 450 genes linked to heart disease and obesity and more than 800 to infectious diseases. Moreover, they have looked at genetic variants that promote fertility and that would have been favoured by natural selection during the mixture of populations. David Comas, researcher at IBE:CSIC-UPF and collaborator on the article, stresses that the great genetic diversity promoted by colonisation and the selective pressure of pathogens on the new inhabitants accelerated the processes of natural selection of the genome, which usually take thousands of years.

This new genomic database created within the framework of the ‘DNA do Brasil’ project is a major step towards deciphering the evolution of the population, its history and improving the health of the country’s inhabitants.