A meta-analysis of stable isotope data from early Pacific Island colonisation to complex chiefdoms

The Pacific Islands offer a singular setting to examine how human populations adapted to conditions of extreme isolation and ecological variability over millennia. Yet key questions persist about the pace of initial colonization, the development of social inequalities, and the varying roles of marine and terrestrial resources in these processes. Stable isotope analysis of human remains provides a direct means to investigate subsistence, mobility, and social differentiation, complementing archaeological proxies that may be absent or ambiguous. Here we present the first large-scale meta-analysis of human collagen δ13C and δ15N values across the Pacific, synthesized from the newly compiled Oceanian Archaeological and Palaeontological Isotope Database (OAPID). Results reveal regionally distinct isotopic signatures shaped by insularity and biogeography, heavy marine reliance during early colonisation, and increasingly pronounced biological sex-based dietary differentiation through time. Geographic and methodological biases, coupled with limited baseline data, continue to challenge inter-regional comparison. Despite these constraints, expanding isotopic coverage is transforming understandings of Pacific lifeways across the vast and remote region. This synthesis highlights the growing potential of isotopic research to address fundamental questions about the timing of colonisation, the development of social differentiation, and human adaptation to complex island ecosystems and social landscapes.