Living in the shore: changes in coastal resource intensification during the Mesolithic in northern Iberia

Recent research on human exploitation of molluscs, echinoderms and crustaceans during the Mesolithic in the Cantabrian region (northern Iberia) has shown significant variability in the intensity of the use of coastal resources by the last hunter-fisher-gatherers throughout the 4000-year expanse of the Mesolithic (10,700 – 6,700 cal BP). Previous studies have proposed hypotheses related to demographic changes to explain intensification events. In this paper we aim to unravel whether climatic and environmental changes, or other social factors, such as demography, were involved in the increase in the use of marine resources at certain times. We employed species representation, quantification and biometric analysis of the shell assemblages from the El Toral III archaeological site (Asturias, northern Iberia) to identify patterns in shell exploitation throughout the stratigraphic sequence. To establish the chronology and distinguish occupation phases of the site, we employed Bayesian modelling of radiocarbon measurements. Faunal results show that marine gastropods such as limpets of the Patella genus and topshells Phorcus lineatus (da Costa, 1778) were the most exploited species, while bivalves, echinoids and crustaceans were present in smaller quantities. The comparison of the results for El Toral III with other Mesolithic sites in the region reveals significant temporal differences in the intensity of collection of marine shell species. Results showed that intensification processes are not clearly related to climate change but to other social factors, such as demography, suggesting that intensification and relaxation in shell collection events were strategies adopted depending on the needs of the human groups at different times.