Arroyo Seco II — Voices of the Pampas

Arroyo Seco II sits like a time capsule in the windswept Pampas of central Argentina. Archaeological data indicates repeated human presence in the early Holocene, with materials dated between c. 7010 and 5350 BCE. Excavations have recovered burials and associated lithic artefacts that speak to long-lived foraging lifeways on open grasslands and river margins.

Geographically this site occupies a key corridor between the southern cone's interior plains and coastal systems, hinting at mobility and resource flexibility among its inhabitants. Paleoenvironments reconstructed from pollen and sediment (regional studies) suggest a cooler, drier interval early in the sequence with increasing humidity over time, which would have altered resource distribution and settlement patterns.

Genetically, the recovered individuals belong to lineages common across the Americas, which supports archaeological interpretations of early pan-American dispersals and subsequent regional differentiation. However, the total sample count is five; limited evidence suggests caution in broad generalizations about population structure or continuity. Archaeology and DNA together illuminate a portrait of resilient hunter-gatherer communities adapting to shifting Holocene landscapes.

Five ancient individuals from Arroyo Seco II provide a rare genetic window into early Holocene South America. The Y-chromosome profile is dominated by haplogroup Q (4 of 5 males), a lineage widely associated with Native American paternal ancestry and inferred to descend from the Beringian-derived founding population(s). On the maternal side, mitochondrial haplogroups include C1b (2), D1 (1), A2 (1) and D1g (1). These mtDNA clades are among the canonical founding lineages observed across the Americas.

Together, the paternal and maternal signals are consistent with ancestry that traces to the initial peopling of the continents, followed by regional diversification in South America. Genetic affinities to other early South American individuals point toward broad relatedness rather than extreme isolation. Yet with only five samples, statistical power is low: patterns of substructure, sex-biased migration, and long-term continuity cannot be robustly resolved.

Archaeogenetic analyses can test hypotheses raised by material culture—such as whether mobility corridors inferred from artifacts correlate with gene flow—but for Arroyo Seco II conclusions must remain tentative. Future sampling, particularly larger numbers and comparisons across neighboring sites, will be essential to move from suggestive patterns to confident reconstructions of demographic history.