Coastal resource intensification across the Pleistocene–Holocene transition in Northern Spain: Evidence from shell size and age distributions of marine gastropods

Abstract

Evidence for the exploitation of marine resources has been identified throughout prehistory but its relative importance has varied. Knowledge for earlier periods is biased by low archaeological visibility, and so the majority of hypotheses support the occurrence of intensification in the exploitation of marine resources during the Holocene. In the Cantabrian region (northern Spain) intensification has been proposed by some authors and rejected by others and there is also debate over when it began. Marine molluscs have been one of the most studied resources to support or reject intensification, and these studies have been mainly focused on variations of shell size through time. The hypothesis supporting intensification suggests that the decrease in molluscan size during the Holocene was caused by human pressure, whilst the alternative hypothesis is that this was induced by climatic and environmental conditions. In this paper, I study change of shell size and age distributions in northern Spain leading up to and after the Pleistocene–Holocene transition (35,000–5700 cal BP) using samples of four gastropod species from 18 shell midden sites. The species studied are the most abundant in the regional shell middens: Patella vulgata Linnaeus 1758, Patella intermedia Murray in Knapp 1857, Osilinus lineatus (Da Costa, 1778) and Littorina littorea (Linnaeus, 1758). The trends observed in both shell size and age structures shows that changes during the Upper Paleolithic may be due to climatic factors, but the constant decrease in both variables during the Mesolithic and the early Neolithic was caused by human pressure.