Human forager response to abrupt climate change at 8.2 ka on the Atlantic coast of Europe

The cooling and drying associated with the so-called '8.2 ka event' have long been hypothesized as having sweeping implications for human societies in the Early Holocene, including some of the last Mesolithic hunter-gatherers in Atlantic Europe. Nevertheless, detailed 'on-site' records with which the impacts of broader climate changes on human-relevant environments can be explored have been lacking. Here, we reconstruct sea surface temperatures (SST) from ?18O values measured on subfossil topshells Phorcus lineatus exploited by the Mesolithic human groups that lived at El Mazo cave (N Spain) between 9 and 7.4 ka. Bayesian modelling of 65 radiocarbon dates, in combination with this ?18O data, provide a high-resolution seasonal record of SST, revealing that colder SST during the 8.2 ka event led to changes in the availability of different shellfish species. Intensification in the exploitation of molluscs by humans indicates demographic growth in these Atlantic coastal settings which acted as refugia during this cold event.This research was performed as part of the projects HAR2016-75605-R and HAR2017-86262-P, funded by the Spanish Ministry of Economy and Competitiveness, MINECO. During the development of this research AGE was funded by the University of Cantabria through a predoctoral grant (no code available), by the Basque Country Postdoctoral Programme (Grant number POS_2020_2_0032), by the University of La Rioja through a posdoctoral grant (no code available) and he is currently supported by the Catalonia Postdoctoral Programme through a Beatriu de Pinos fellowship (grant number 2020 BP 00240). ABMA was funded by the SUBSILIENCE ERC-CoG project (Grant agreement No. 818299). This study has also been supported by the Prehistoric Research Consolidated Group of the Basque Country University (IT1223-19), funded by the Basque Country Government. We thank the Max Planck Institute for Science of Human History (MPI-SHH), University of Cantabria (UC), Instituto Internacional de Investigaciones Prehistoricas de Cantabria (IIIPC), Grupo de Ingenieria Fotonica (GIF), University of the Basque Country (UPV/EHU), University of La Rioja (UR) and Autonomous University of Barcelona (UAB) for providing support