RELATIONSHIP BETWEEN EARLY HOLOCENE CLIMATE CHANGE AND CAPSIAN TECHNOLOGICAL AND SUBSISTENCE CHANGES IN NW AFRICA AS INFERRED FROM ARCHEOLOGICAL LAND SNAILS

During the early Holocene, NW Africa experienced several cultural transitions. One of these was a technological change within the Capsian complex in eastern Algeria which was accompanied by a minor shift in subsistence regime. Published work has hypothesized that the observed cultural changes may have been related to local climate change. This hypothesis is tested here using the oxygen (δ¹⁸O) and carbon (δ¹³C) stable isotope composition of terrestrial gastropod shells recovered from well-constrained layers at the Aïn Misteheyia open-air Capsian escargotière in the Tebessa region of eastern Algeria. Several well-preserved terrestrial gastropod shells of the dominant edible-size species Helix melanostoma were selected for intra-shell isotopic analysis along shell growth direction. Shells were sampled using a manual Dremel drill to mill carbonate powder every ~1 mm along shell growth direction, from shell lip to embryonic shell. This high-resolution sampling design allows reconstruction of seasonal variations in humidity (δ¹⁸O) and vegetation (δ¹³C) throughout the snails’ lifespan (~2-3 yrs). Archeological shells were also radiocarbon dated at the shell lip region to further constrain the age of the analyzed samples. Shell δ¹⁸O values of early Holocene shells were, on average, ~1‰ lower than modern shells, pointing to wetter conditions at ~10.7 cal ka BP than at present. The magnitude of seasonality was smaller during the early Holocene than today. After the Suess effect correction, shell δ¹³C values of archeological shells were comparable to living specimens, suggesting relatively stable vegetation throughout the Holocene in eastern Algeria, which is dominated by C₃ plants. The snail results illustrate that local climate change occurred in eastern Algeria during the early Holocene and this could have influenced cultural transitions in the region.