Climate and oceanic condition changes influence subsistence economic adaptation through intensification on the Central Andean coasts

Abstract

Understanding the causes of subsistence economic adaptation remains a critical topic in archaeology. Here we explore one potential causal phenomenon, climate change, to understand how shifting ecological conditions incentivized adaptation through subsistence economic intensification along the Central Andean coasts. To do so we couple 775 archaeological individuals that have dietary stable isotope data (collagen δ13C and δ15N, hydroxyapatite δ13C) with spatio-temporal core-based proxies of oceanic sea surface temperature and El Niño Southern Oscillation frequency estimates. Using an ensemble machine learning model, we evaluate hypotheses that changes in ocean conditions resulting in decreased marine productivity correspond with isotopic signals of increasing terrestrial resource reliance over the past ∼7000 years. Results support the hypotheses, and prior work, showing isotopic signatures of diet across the coastal Central Andes reflect greater incorporation of resources indicative of intensification during times when marine productivity was likely depressed. As near-shore marine productivity declined, people adapted in manners that may have both increased their resiliency to climate change and improved their overall subsistence returns, but at higher investment costs. The overall findings support theoretical intensification expectations, suggesting adaptation through intensification represents one of the key factors in understanding broader behavioral transformation in the face of climate change.