Regional climate change and the onset of farming in northern Germany and southern Scandinavia

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In Europe, the transition from hunter–gatherer–fisher-based communities into societies mainly relying on farming was spread from the southeast towards the north and west during the Holocene. In central Germany, farming was adopted at ~7500 cal. yr BP, whereas the shift is evident at ~6000–5500 cal. yr BP in northern Germany and southern Scandinavia. Consequently, farming techniques were available for more than a millennium. Some studies argue that climate change might have played a role in the onset of farming in those areas. The aim of this study is to reconstruct the mid- to late-Holocene sea surface temperature (SST) evolution in the Skagerrak to document potential regional climatic impacts on changes in human economy. We compare our results with a record of human settlement activity in northern Germany and southern Scandinavia. Prior to ~6300 cal. yr BP, warm SSTs are documented throughout the Skagerrak, suggesting dominance of North Atlantic sourced water inflow providing mild climatic conditions. Between ~6300 and 5400 cal. yr BP, that is, concomitant with the shift in human economy, SSTs in the NE Skagerrak dropped by ~5–6°C, as also documented in mean annual air temperatures in central South Sweden, although less pronounced. The regional cooling suggests outflow of colder Baltic Sea water only affecting the NE Skagerrak and central South Sweden. Probably, numerous severe winters reflecting a continental-dominated atmospheric circulation pattern prevailed over the region. These changes most likely caused a gradual restriction in natural food sources, in particular from the marine realm. We thus suggest that hunter–gatherer–fishers were forced to adopt farming strategies to counter-balance this environmental stress. Our results indicate that regional changes in oceanography probably amplifying North Atlantic climate change in the western Baltic were an important factor that played a role in the adoption of farming in northern Germany and southern Scandinavia.