Isotopic evidence of human adaptations to diverse island environments: the Canary Islands during the Amazigh period (1st to 15th century CE)

Abstract

This study investigates subsistence strategies and ecological adaptations among the Indigenous populations of the Canary Islands from the 1st to the 15th centuries CE, employing stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope analyses of human bone collagen. A total of 457 isotopic data points from all seven main islands of the archipelago were analyzed, supported by a robust chronological framework based on 155 radiocarbon dates and Bayesian modeling. Results reveal distinct dietary patterns shaped by ecological conditions: populations on the western islands (La Palma, La Gomera, and El Hierro) exhibited a diet predominantly reliant on C3 plants and wild terrestrial resources, with evidence for intensified wild plant utilization during periods of agricultural stress. In contrast, central islands (Tenerife and Gran Canaria) showed narrower isotopic variance, indicating stable agricultural production complemented by varying degrees of marine resource exploitation. The desert-like eastern islands (Lanzarote and Fuerteventura) demonstrated isotopic signatures indicative of diets heavily influenced by high-trophic-level marine foods, likely complicated by aridity and marine aerosol effects. Additionally, temporal analysis indicates isotopic values correspond closely with climatic fluctuations, notably warmer and drier conditions during the Roman Warm Period and Medieval Climate Anomaly, and cooler, moister conditions during the Little Ice Age. These environmental shifts appear to have driven subtle dietary adaptations over time. Overall, the findings highlight the Indigenous populations' resilience and adaptive capacity in response to insular ecological variability and climatic change, underscoring the importance of tailored isotopic baselines for accurate dietary reconstructions in diverse oceanic island settings.