DIET OF THE PREHISTORIC POPULATION OF RAPA NUI (EASTER ISLAND, CHILE) SHOWS ENVIRONMENTAL ADAPTATION AND RESILIENCE

Rapa Nui (Easter Island, Chile) is frequently used as an exemplar of human behavior and social competition leading to an avoidable ecological disaster, in which rapid destruction of the native palm forest had devastating consequences for the island’s environment and human population. Recent archaeological research has brought such Malthusian claims into question. The co-arrival of the Pacific rat (Rattus exulans) shortly after the island's colonization may have extensively contributed to the palm forest’s demise. Revised chronologies indicate settlement of Rapa Nui centuries later than previously supposed, with suggestions of a more balanced interaction with the environment than the ‘ecocide’ model purports. Knowing past diets is crucial for understanding the impacts of human occupation on Rapa Nui, yet prehistoric diets of the native islanders have received remarkably little attention. Here we examine prehistoric human and faunal bone using carbon and nitrogen compound-specific isotope analyses of amino acids, showing that around half of dietary protein in Rapa Nui palaeodiets came from marine resources. This is strikingly different from previous estimates that considered seafood a minor part of human diets. Our results also point to consumption of terrestrial plants with highly elevated δ¹⁵N values, which we suggest come from agricultural crops grown in substantially manipulated soils in lithic mulch gardens and manavai. These gardens required considerable effort in transporting the rocks required to construct and maintain manavai and mulched areas, attesting to the effort invested in cultivating terrestrial resources. Our finding suggest that the Rapa Nui prehistoric population adapted to the harsh conditions by efficiently using limited marine resources and developing refined horticultural skills to create a sustainable food supply. Further, our refined estimates for marine protein consumption show the considerable benefit of using amino acid isotopic data for marine reservoir corrections of radiocarbon dates.