Stone-age subsistence strategies at Lake Burtnieks, Latvia

Zvejnieki, on Lake Burtnieks in northeastern Latvia, is the largest known prehistoric cemetery in the eastern Baltic; > 300 inhumations, most dating to c.7000-3000 cal BC, have been excavated. Archaeozoological and artefactual evidence from graves and nearby settlement layers show that throughout this period, the community depended on wild resources for subsistence, with a particular emphasis on fishing. Dietary stable isotopes (δ15N and δ13C) from human remains show significant dietary variation within the Zvejnieki population, in terms of access to and dependence on freshwater and marine species (Eriksson 2006); we provide new stable isotope data for another 13 individuals. Elsewhere, we have proposed a method to correct the calibrated radiocarbon (14C) dates of prehistoric burials in the Lake Burtnieks region for dietary freshwater and marine reservoir effects (FRE/MRE) (Meadows et al. 2015). Here, we use this method to correct the dates of 40 individuals (including 3 from the nearby 4th millennium shell-midden site, Riņņukalns) for whom we now have both 14C and stable isotope data, and test whether there is any evidence that human diets changed over time, rather than simply varying between contemporaneous individuals. Three interesting transitions can be discerned: a shift away from high-trophic-level foods in the earlier 6th millennium cal BC, a diversification of diets in the late 5th millennium, with both more terrestrial and more coastal foods consumed, and a narrowing of diets in the mid-4th millennium, to concentrate on freshwater resources.