Camelids in the hyperarid core of the Atacama desert 12,000–11,000 years ago? A stable isotope study and its consequences for early human settlement

How did hunter-gatherers initially settle and move across extreme environments? We conducted a multi-disciplinary study to tackle this question, focusing on how Paleoindigenous populations inhabited the hyperarid core of the Atacama Desert. Particularly, we examined the stable isotopic values of ∼12,000–11,200-year-old camelid and rodent bones and hair samples retrieved from low-elevation archaeological sites (Pampa del Tamarugal basin - PdT, 800–1200 masl). By integrating novel and existing data into a regional stable isotope ecology, we offer a baseline for interpreting our results. δ¹³C and δ¹⁵N values on archaeological remains show animals with different geographical origins. A first group includes camelids and rodents with lower δ¹⁵N values and δ¹³C values indicating a dominantly C₃ diet, corresponding to animals either local to the PdT or from the Andean Steppe, at least ∼80 km away and between 4000 and 4500 masl. Most of these remains, however, come from residential sites and belong to young camelids, indicating a local origin. A second group presents a higher δ¹⁵N signal and δ¹³C values indicative of a mixed C₃–C₄ based diet. These animals were not local but source to the Puna at least ∼60 km away between 3200 - 4000 masl. We hypothesize that the first would correspond to animals associated with hunter-gatherer bands settled around a wetland and grove environment in the PdT. The second group could correspond to remains brought by humans from the Puna to the PdT. Our results demonstrate that during the Late Pleistocene/Early Holocene the Atacama was very different than today, supporting life that included large and mid-size game. These results also show that the core of the Atacama attracted animals and people and counters the notion of this ecosystem as a barren passageway from the Andes to the coast.