Intergenerational transmission of ancestry information in a mid-size city in Argentina

We examined the self-reported family trees of 288 adult Argentines from a mid-size city near Buenos Aires to evaluate how intergenerational transmission of ancestry information matched (or not) anonymized estimates of continental-level genetic ancestry. Intergenerational transmission of ancestry information was inferred from the content of the anonymized family trees, and continental-level ancestries were inferred from genomic information collected from the participants. We found a high degree of concordance between genetic ancestry estimates and the transmission of ancestry information in ancestors born in Europe, the Middle East, and Southeast Asia. We found the reverse in ancestors who were Indigenous American, sub-Saharan African, or their descendants. Yet, the existence of those ancestors was evident in the genetic ancestry estimates. We extrapolated the presence of such ancestries in family trees post hoc by deducing that some ancestors identified as ‘Argentine’ in family trees were likely of mixed Indigenous- and non-Indigenous-descent, and possibly also sub-Saharan African descent. We describe these findings as products of a process of attrition, in which some ancestries, but not others, have been forgotten (knowingly or unknowingly) over the course of generations, to the point that participants were unaware that ethno-racial mixing occurred within their own families.