Middle Stone Age (MSA) shellfish remains were studied for indications of changes in subsistence adaptations. Optimal Foraging Theory was applied to the MSA shellfish species from Blombos Cave and Klasies River, South Africa, to model which shellfish would be most profitable to collect in terms of meat yield and handling costs. This ranking is compared to the composition of the archaeological shellfish assemblages. Several developments are considered to be the result of changes in prey choice. It appears that at Klasies River, MSA people mainly collected high ranked mid-intertidal shellfish, and that their foraging strategy was strongly influenced by changes in the coastal environment. At Blombos Cave, when the sea was further from the cave, a revaluation of the prey ranking caused an increase in . Perna perna densities in the M2 and M1 phases, compared to the older M3 phase. . P. perna was not only selected because, as a bivalve it preserves better during transport, but also because it can easily be mass collected. At Blombos Cave there are changes in species representation and a decrease in average . Turbo sarmaticus opercula weight. This tentatively suggests that shellfish collection may have intensified during later phases. In general, MSA collecting trips were optimized according to the available shellfish, taking into account the distance to the resource and their yield.@en

We explore if taxonomic analysis of archaeological mollusc assemblages can be used to reconstruct Late Pleistocene (MIS 5–3) coastal environments at Klasies River in South Africa. To obtain a balanced reconstruction, we analyse the large molluscs separately from the so-called incidentals, the small mollusc species. Based on modern mollusc habitat preferences and tolerances we identify four different eco-profiles to help characterise sea surface temperatures and the character of the shore: temperature profile; geographical distribution; substrate; wave interaction. We hypothesise that changes in the Klasies River mollusc community/eco-profiles can be linked to global glacial and interglacial events and we define several testable assumptions. We found that in response to global warming and cooling events, the Klasies River mollusc communities change slightly, yet significantly. Other sources of marine environmental data confirm that average sea surface temperatures gradually decreased, but probably remained within the modern southern east coast range of variation. It appears that coastal sea surface temperatures of the warm Agulhas current were not particularly depressed during the occupation sequence. The character of the coastal topography does change more apparently during the occupation sequence of the sites and with it the mollusc assemblages: from an interglacial rocky shore in the Klasies and two Mossel Bay phases to a more glacial sandy environment during the Howiesons Poort and the MSA III. In conclusion, the temperature tolerance levels of many Klasies River mollusc species are too broad to reflect small changes in sea surface temperatures. However, in conjunction with other eco-profiles and environmental proxies, such as substrate requirements and oxygen isotopes, the temperature approximations are useful, particularly when evaluating large scale sea surface temperature fluctuations. For the characterisation of the shore and substrate we found the eco-profile approach very useful.@en