Shells and humans: molluscs and other coastal resources from the earliest human occupations at the Mesolithic shell midden of El Mazo (Asturias, Northern Spain)

Human populations exploited coastal areas with intensity during the Mesolithic in Atlantic Europe, resulting in the accumulation of large shell middens. Northern Spain is one of the most prolific regions, and especially the so-called Asturian area. Large accumulations of shellfish led some scholars to propose the existence of intensification in the exploitation of coastal resources in the region during the Mesolithic. In this paper, shell remains (molluscs, crustaceans and echinoderms) from stratigraphic units 114 and 115 (dated to the early Mesolithic c. 9 kys cal BP) at El Mazo cave (Asturias, northern Spain) were studied in order to establish resource exploitation patterns and environmental conditions. Species representation showed that limpets, top shells and sea urchins were preferentially exploited. One-millimetre mesh screens were crucial in establishing an accurate minimum number of individuals for sea urchins and to determine their importance in exploitation patterns. Environmental conditions deduced from shell assemblages indicated that temperate conditions prevailed at the time of the occupation and the morphology of the coastline was similar to today (rocky exposed shores). Information recovered relating to species representation, collection areas and shell biometry reflected some evidence of intensification (reduced shell size, collection in lower areas of exposed shores, no size selection in some units and species) in the exploitation of coastal resources through time. However, the results suggested the existence of changes in collection strategies and resource management, and periods of intense shell collection may have alternated with times of shell stock recovery throughout the Mesolithic.This research was performed as part of the project “The human response to the global climatic change in a littoral zone: the case of the transition to the Holocene in the Cantabrian coast (10,000–5000 cal BC) (HAR2010-22115-C02-01)” funded by the Spanish Ministry of Economy and Competitiveness. AGE was funded by the University of Cantabria through a predoctoral grant and IGZ was funded by the Spanish Ministry of Economy and Competitiveness through a Juan de la Cierva grant. We also would like to thank the University of Cantabria and the IIIPC for providing support, David Cuenca-Solana, Alejandro García Moreno and Lucia Agudo Pérez for their help. We also thank Jennifer Jones for correcting the English. Comments from two anonymous reviewers helped to improve the paper

East Asian monsoon variations directly recorded in the Greenlandic North-GRIP ice core

Ice cores from central Greenland are the temporally best resolved records of northern hemisphere climate of the last glacial period. Here we show that during the last glacial period (MIS 4 to MIS 2) East Asian Monsoon variations are directly recorded in the North-GRIP ice core (north-central Greenland). The East Asian Winter Monsoon (EAWM) strength as inferred from Chinese loess deposits correlates well with the concentration and size distribution of insoluble mineral particles in the North-GRIP core, and we infer that the ice core microparticle record can be taken as a proxy for EAWM. Further, variations of the East Asian Summer Monsoon (EASM) strength are coincident with changes of the Ca2+/particle ratio at North-GRIP. In light of these findings and taking d18O as a proxy for North Atlantic temperature we investigate the rapid climatic transitions during the last glacial period (Dansgaard-Oeschger events). We discuss differences between the changes of EAWM, EASM, and North Atlantic temperature regarding their timing at these rapid transitions; this can be done with unforeseen accuracy because all proxies are from the same archive and do not underlie relative dating uncertainties. Furthermore we find that before 75ka BP (i.e. before the MIS 4/5-transition) atmospheric circulation patterns in the northern hemisphere as well as teleconnections between North Atlantic circulation and the East Asian Monsoon system must have been substantially different. They underwent considerable reorganisation, which may be linked to the build up of large ice sheets in the northern hemisphere during this time