High-resolution compound-specific δ15N isotope dietary study of humans from the Scottish Mesolithic and Neolithic

Numerous isotopic studies of Scottish Mesolithic and Neolithic diets suggest a shift from marine-based to terrestrial-based subsistence strategies. However, bulk collagen isotope analysis may overlook low-level marine food consumption. This study combines bulk collagen stable isotope data from four Neolithic sites (Quanterness, Rattar East, Ness of Brodgar, and Knap of Howar) with nitrogen compound-specific isotope analysis (CSIA-AA) from one Late Mesolithic and five Neolithic sites. CSIA-AA, applied here for the first time to Scottish material, reveals limited but detectable aquatic resource use by some Neolithic individuals in Orkney. These findings highlight the complexities in identifying marine contributions to diet and underscore the value of CSIA-AA in distinguishing direct marine consumption from other sources of elevated nitrogen isotope values, such as seaweed or animals with marine-influenced diets.