Mid-Holocene SPD records from the Baltic Region in relation to climatic changes. (A) Population proxy using a summed probability distribution (SPD) of archaeological radiocarbon dates within the polygon indicated in Fig. 1. Y-axis represents the probability density, on a relative scale. (B) Cultural composition (%) based on the subset of the radiocarbon dates with cultural affiliations assigned by the original excavator (58% of full dataset used in (A)). Note the rapid change at the boundary between the Meso- and Neolithic, coincides with a substantial increase of the population. Dotted lines show the complete time series, solid lines show a 200 yr rolling mean, to dissuade overinterpretation of small scale wiggles from the calibration curve. (C) Summer SST record based on TEX86 palaeothermometry. The red line plots the 5-point rolling mean. June insolation at 60°N (in W m−2) is plotted as a grey dashed line. The population levels increased synchronously with a period of warming after 6,000 cal. yr BP.