Arroyo Seco II: Pampas Foragers

Along the flat horizons of the Argentine Pampas, Arroyo Seco II stands as a quiet archive of early Holocene life. Radiocarbon-dated contexts spanning roughly 7010–5350 BCE indicate repeated, seasonal occupations by mobile foragers. Archaeological data indicates hearths, flaked stone tools and fragmented faunal remains, suggesting a landscape of hunting, processing and transient camps rather than dense sedentary villages.

Geographically, these occupations belong to broader southern South American forager traditions that exploited open grasslands after the Late Pleistocene environmental shifts. Limited evidence suggests technological continuity in low-profile lithic toolkits adapted to a mixed diet of small and medium mammals and plants. The picture that emerges is one of small groups moving across the Pampas, occupying river margins and drainages such as Arroyo Seco II to exploit seasonal resources.

Because excavations at Arroyo Seco II produce a modest number of well-dated contexts, interpretations must remain cautious. The archaeological signal is consistent with dispersed, adaptable hunter–gatherers shaping a lifeway tuned to postglacial landscapes, but finer details of social organization and long-distance interaction remain incompletely resolved.

Arroyo Seco II contributes a small but valuable ancient DNA series (n=5) spanning the early to mid-Holocene. Four of the five male-line samples carry Y-chromosome haplogroup Q, a lineage widespread among Indigenous peoples of the Americas and consistent with deep Pleistocene–Holocene population histories across South and North America. On the maternal side, mitochondrial diversity includes C1b (2 individuals), D1 (1), A2 (1) and D1g (1), reflecting the broad palette of founding Native American maternal lineages.

These genetic signatures align with archaeological expectations for early South American foragers: continuity of founding American lineages rather than incoming Eurasian input. However, sample size is small (<10), so population-level inferences must be treated as preliminary. The predominance of Y haplogroup Q here (4/5) suggests paternal continuity within the local groups sampled, while multiple mtDNA haplogroups point to maternal diversity—patterns that could reflect marriage networks, patrilocal residence, or simply stochastic sampling.

When placed within regional datasets, Arroyo Seco II genomes help anchor a Pampas-specific genetic snapshot during the Holocene. Combined genetic and isotopic studies may further reveal diet, mobility and kinship, but current conclusions remain cautious pending larger samples and broader contextual data.