Early evidence of earthquake management through mobility and social network adjustments at Vale Boi (SW Iberia)

Abstract

Tectonic processes profoundly influenced the dispersal, evolution, and archaeological record of our Paleolithic ancestors. However, in-depth reconstructions of human resilience against seismic events come mostly from contexts dating to the last 13,000 years. Here, we present geophysical, geological, geochronological, and archaeological data from the open-air site of Vale Boi in southwestern Iberia, revealing how foragers mitigated earthquake impacts between ~30,000 and 24,000 years ago. At Vale Boi, faulting formed sedimentary traps that were recurrently exploited by hunter-gatherers and periodically buried by rockfalls, likely triggered by ≥5.7 Mw earthquakes. Despite seismic destruction, hunter-gatherers repeatedly returned to the site, drawn by its strategic access to key resources. They mitigated seismic risks by increasing their mobility and even abandoning Vale Boi, as seen during the Gravettian and at the early/late Proto-Solutrean transition. When seismic and climatic stressors co-occurred (Heinrich Event 2), they did not abandon the site. Instead, they adopted strategies to limit their exposure to rockfall hazard while securing access to increasingly vital coastal and estuarine resources. Until the early Proto-Solutrean, tightly knit social networks supported the survival of Vale Boi foragers during periods of high stress, such as the aftermath of seismic rockfalls. During the late Proto-Solutrean, an expansion of super-regional connections might have functioned as a proactive buffer against future tectonic shocks. Our findings demonstrate that forager resilience to seismic events relied on flexible adjustments in mobility and social connectivity. Despite limitations deriving from its single-site focus, this study underscores the value of deep archaeological sequences for disentangling human responses to intertwined geological and ecological pressures.