Journal of Archaeological Science (2001) 28, 1101–1114 doi:10.1006/jasc.2001.0658, available online at http://www.idealibrary.com on Intensive Mesolithic Exploitation of Coastal Resources? Evidence from a Shell Deposit on the Isle of Portland (Southern England) for the Impact of Human Foraging on Populations of Intertidal Rocky Shore Molluscs Marcello A. Mannino and Kenneth D. Thomas* Institute of Archaeology, University College London, 31–34 Gordon Square, London, WC1H 0PY, U.K. (Received 5 October 2000, revised manuscript accepted 8 February 2001) Recent research has indicated the importance of marine foods in the diet of some late Mesolithic (c. 5000–4000 cal ) populations in western Europe, but little is known of the role of such resources in the earlier Mesolithic. Analysis of assemblages of marine molluscs from the shell midden of Culverwell, Isle of Portland, showed changes in the absolute abundance of the three dominant species, as well as changes of mean shell size and age-class frequencies in the species Monodonta lineata (da Costa), through the midden. It is suggested that these changes result from the impact of human foraging on the populations of these molluscs, and that rocky-shore intertidal molluscs were exploited intensively and frequently (possibly annually) from the site in the earlier Mesolithic (c. 6000–5200 cal ).  2001 Academic Press Keywords: MESOLITHIC, MARINE RESOURCES, SHELL MIDDEN, INTERTIDAL MOLLUSCS, MONODONTA LINEATA, CULVERWELL, HUMAN IMPACT. Introduction T here has been much recent discussion of the role of marine resources, including shellfish, in Mesolithic subsistence strategies in north- western Europe. Seasonality evidence from late Mesolithic shell midden sites on Oronsay (southern Hebrides) suggests year-round exploitation of marine resources on the island (Mellars & Wilkinson, 1980). The stable isotope composition of human bones from sites on Oronsay led Richards & Mellars (1998) to infer that marine foods were a major component of the human diet. A compelling case could be made for coastal sedentism on Oronsay in the late Mesolithic. On a broader geographical scale, stable isotope evi- dence from late Mesolithic human remains from a range of sites along the Atlantic coast of Europe suggests that marine foods were a significant part of the diet of those individuals studied (Richards & Hedges, 1999a), in marked contrast to Neolithic indi- viduals who had fully terrestrial diets (Richards & Hedges, 1999b). The late Mesolithic individuals analysed were probably eating mostly fish, with marine molluscs constituting a relatively minor part of the food intake. Was this a continuation of pre-existing food exploitation patterns in the earlier Mesolithic, or did it represent a significant shift in environmental and resource exploitation associated with factors specific to the later Mesolithic, or even to the Mesolithic-to- Neolithic transition? Calibrated AMS dates on human bone from two sites on Oronsay (Richards & Sheridan, 2000) suggest that occupation there might overlap with the occurrence of the earliest Neolithic in Britain. Mithen (2000) showed that the late Mesolithic chronol- ogy of the Oronsay sites (Switsur & Mellars, 1987) fits into a chronological gap identified in a series of radiocarbon dates from other Mesolithic sites in the southern Hebrides. He suggested that this episode of specialized marine exploitation inferred from the Oronsay evidence could have been a short-term departure from the ‘‘normal’’ mixed terrestrial-marine subsistence economy, which lasted throughout the Mesolithic and into the Neolithic (Mithen, 2000: 303). What contribution marine resources made to earlier Mesolithic subsistence economies is difficult to assess because although late Mesolithic coastal sites (includ- ing shell middens) are relatively frequent in western Europe, the rise in relative sea-levels in the early- to mid-Holocene made earlier Mesolithic shell middens quite rare. A combination of rising sea levels and crustal down warping, submerging significant areas of coastline, has made southern Britain particularly deficient in stratified coastal Mesolithic sites, both early and late, but a notable exception to this is the well-stratified site of Culverwell on the Isle of Portland (Palmer, 1999). In this paper we analyse the assemblages of marine molluscs from Culverwell and suggest that human exploitation of shellfish resources at this site was both frequent and intensive. *Author for correspondence. 1101 0305–4403/01/1001101+14 $35.00/0  2001 Academic Press