Heterogeneity in Genetic Admixture across Different Regions of Argentina

TLDR

Argentina’s population is the result of intermixing Indigenous American, European, and African groups, and studies show that admixture has shaped the entire population, contrary to the common belief of predominantly European ancestry. This study aimed to map Indigenous American, European, and African ancestry across Argentine regions and assess discrepancies between self‑reported grandparental origins and genetic ancestry estimates. Researchers genotyped 99 autosomal ancestry‑informative markers in 441 individuals and applied non‑parametric tests to evaluate statistical significance. The sample averaged 65 % European, 31 % Indigenous American, and 4 % African ancestry, with marked regional variation in European ancestry and a strong mismatch between self‑reported European grandparents and genetic estimates, underscoring the need to account for this heterogeneity in genetic studies.

Abstract

The population of Argentina is the result of the intermixing between several groups, including Indigenous American, European and African populations. Despite the commonly held idea that the population of Argentina is of mostly European origin, multiple studies have shown that this process of admixture had an impact in the entire Argentine population. In the present study we characterized the distribution of Indigenous American, European and African ancestry among individuals from different regions of Argentina and evaluated the level of discrepancy between self-reported grandparental origin and genetic ancestry estimates. A set of 99 autosomal ancestry informative markers (AIMs) was genotyped in a sample of 441 Argentine individuals to estimate genetic ancestry. We used non-parametric tests to evaluate statistical significance. The average ancestry for the Argentine sample overall was 65% European (95%CI: 63-68%), 31% Indigenous American (28-33%) and 4% African (3-4%). We observed statistically significant differences in European ancestry across Argentine regions [Buenos Aires province (BA) 76%, 95%CI: 73-79%; Northeast (NEA) 54%, 95%CI: 49-58%; Northwest (NWA) 33%, 95%CI: 21-41%; South 54%, 95%CI: 49-59%; p<0.0001] as well as between the capital and immediate suburbs of Buenos Aires city compared to more distant suburbs [80% (95%CI: 75-86%) versus 68% (95%CI: 58-77%), p = 0.01]. European ancestry among individuals that declared all grandparents born in Europe was 91% (95%CI: 88-94%) compared to 54% (95%CI: 51-57%) among those with no European grandparents (p<0.001). Our results demonstrate the range of variation in genetic ancestry among Argentine individuals from different regions in the country, highlighting the importance of taking this variation into account in genetic association and admixture mapping studies in this population.