NEW YORK – Investigators at the University of Pavia and other international centers used modern-day population genetic data to untangle the complex history of an Indigenous Ashaninka population found in Amazon rainforest regions of Peru and Brazil.
"There were only a few genetic studies about the Ashaninka and their origins [in the past], despite being the largest among the 51 Indigenous groups currently living in Amazonian Peru," first and co-corresponding author Marco Rosario Capodiferro, a genetics researcher affiliated with Trinity College Dublin and the University of Pavia, and senior author Alessandro Achilli, at the University of Pavia, said in an email.
Capodiferro and Achilli further noted that prior studies pointed to "significant isolation and genetic homogeneity within the group," as well as "genetic distance from other Peruvian Indigenous groups."
In contrast, the latest study, appearing in Current Biology on Thursday, pointed to unexpected genetic variation within the Ashaninka population. When the researchers used array-based genotyping to profile genetic patterns in 51 Ashaninka individuals living in the Amazon region of Peru, they identified two genetic clusters — dubbed Ashaninka1 and Ashaninka2 — that highlighted distinct population histories and relationships within the seemingly uniform Ashaninka population, who all speak a language from the Arawakan language family.
In particular, the team's results pointed to ancestry from Indigenous groups that migrated to the Amazonian rainforest region from more southerly sites near the Atlantic coast area and the so-called Southern Cone. That migration appears to have been followed by differential mixing with other Indigenous groups from the Andes or Pacific regions.
"The genetic structure of the Americas has been shaped by multiple waves of migration, leading to admixture events challenging our ability to reconstruct its genetic history," the authors noted, explaining that the current results are consistent with "gene flow from southeastern South America" as an initial ancestry source for the Ashaninka population.
Based on available historical documents, the team suspects that the Andean ancestry found in some of the Ashaninka individuals reflects trading between Ashaninka and Andean groups in the period leading up to the Inca Empire — interactions that may have led to genetic mixing and the adoption of some cultural materials and customs from the Andean group.
"We recognized that these trade exchanges also implied the movement of people and gene flow admixture, which probably took place … before the Inca Empire," Capodiferro and Achilli noted. "This exchange did not impact homogeneously the entire Ashaninka group, leading to the differentiation of subgroups based on the degree of interaction with other Peruvian populations."
More broadly, the team's genetic analyses provided a clearer look at the apparent genetic ties between Arawakan language-speaking Ashaninka ancestry groups and populations from Caribbean sites falling to the north of the Amazon.
"Genetic connections between the spread of the Arawakan family language and the Ceramic Indigenous group of the Caribbean islands have been proposed and dismissed in turn," Capodiferro and Achilli explained, noting that findings from the current study revealed "high proximity between the Peruvian Ashaninka and the Caribbean Ceramic groups."
Consequently, they said, "it is conceivable that the Ashaninka ancestors [who] took part in a south-north migration across South America were also involved in the transition from Archaic to Ceramic culture in the Caribbean Islands."