A study has revealed exceptionally high levels of genetic diversity in Brazil and uncovered millions of previously unknown genetic variants not found in current databases, which are predominantly European.
The findings, outlined in , strengthen calls for more diverse inclusion into genetic databases and biobanks.
This would help in the design of future studies into personalized medicine, as some genetic variants can have a substantial impact on medically relevant traits such as drug metabolism.
The research revealed that, on average, the ancestry of Brazilians is approximately 59% European, 27% African, and 13% Indigenous.
It identified nearly 9 million previously unknown genetic variants, more than 36,000 of which were rare and potentially damaging. The variants that could be potentially harmful to health were more common among people with African ancestry.
“Brazil has the greatest African diversity on the American continent, with a high level of admixture, and studying this can shed light on the health of the Brazilian population,” said researcher Tábita Hünemeier, PhD, a population geneticist at the University of São Paulo.
Fellow author Marcos Araújo Castro e Silva, PhD, from the same institution, added: “Exploring these genetic variants can help us understand why some people are more likely to get certain diseases, and how to improve Brazil's public health.”
The genomic map reveals Brazil's history since the 15th century, during which time around 5 million European settlers arrived and at least 5 million Africans were brought in as slaves into an area that already had more than 10 million Indigenous inhabitants.
To discover more about the current genetic makeup of the country's population, Hünemeier and team generated whole-genome sequence data from 2,723 individuals across Brazil from a wide range of ethnic, geographic, and cultural backgrounds.
This revealed more than 8.7 million previously undocumented genetic variants, which represented more than 11% of all variants in the dataset. Some of these lay in regulatory and protein-coding regions that could influence traits such as fertility, metabolism, and immunity.
The team also unveiled 36,637 rare and potentially harmful variants, including those in 450 genes linked to heart diseases and obesity in the Brazilian population. There were also genetic variants in 815 genes relating to infectious diseases such as malaria, hepatitis, flu, tuberculosis, salmonellosis, and leishmaniasis.
There also appeared to be a historical asymmetrical mating pattern between European men—who most likely formed the majority of settlers— and Indigenous American and African women that could relate to the history of colonization.
The researchers found that most of Y-chromosome lineages in the study (71%) which are inherited from men, were of European origin. By contrast, the mitochondrial lineages—which are inherited from women—were African (42%) or native American (35%).
The investigators conclude: “We show that this genetic landscape finds its roots in the evolutionary history of Brazilian Indigenous communities and the intricate demographic interplay stemming from both coerced and voluntary historical immigration to Brazil.”