El Collado shell midden and the exploitation patterns of littoral resources during the Mesolithic in the Eastern Iberian Peninsula

The 1980s excavations at the El Collado, a large open-air Mesolithic site on the Eastern coast of Spain, revealed a sequence of human occupations consisting of a large shell midden and 14 human burials dated to the Mesolithic period. Human palaeodietary reconstructions based on bone collagen δ13C and δ15N isotope ratios, identified a variable contribution of marine proteins, ranging from fully terrestrial diets to a maximum input of 25%. Most subsequent research on Mediterranean coastal and dietary adaptations refers to the site's funerary record and palaeodietary study, but the composition of its shell midden has remained unstudied. This work reports the first systematic study of a representative sample of mollusc and a comparatively small assemblage of fish bone recovered from the different stratigraphic horizons of El Collado site. Results indicate a mixed marine–terrestrial mollusc composition of the shell midden. The edible land snail Sphincterochila candidissima and the marine bivalve Cerastoderma glaucum are the best represented species throughout the archaeological sequence. The pattern of intertidal resource exploitation is clearly dominated by bivalves (C. glaucum, Glycimeris violacescens, and Ruditapes decussatus) and gastropods (Cerithium vulgatum, Hexaplex trunculus) inhabiting mud and sand flats in coastal lagoon environments. The presence of rocky shore intertidal species is minimal, mostly related to the manufacture of pierced shell ornaments made from Columbella rustica. On the other hand, fish bone assemblages are overwhelmingly dominated by the gilthead sea bream (Sparus aurata) a coastal species frequent in brackish water coastal lagoons and estuaries, both on rocky and sandy grounds. The biometric analysis of C. glaucum records differences on shell size amongst the different layers, suggesting variations of marine productivity throughout the archaeological sequence.