Possible freshwater resource consumption by the earliest directly dated European modern humans: Implications for direct radiometric dating

Abstract

Richards and Trinkaus (1) infer from bone collagen carbon and nitrogen stable isotopic composition a significant contribution of freshwater resources in the diet of early European modern humans, especially for the oldest directly dated specimen from Pestera cu Oase, Romania. Although the confirmation of such diet still requires direct comparison of contemporaneous fauna from the same region (2), such a claim raises the question of a possible increase of radiocarbon ages due to freshwater reservoir effect. It has been documented that freshwater resources and their consumers exhibit lower 14C amounts in their organic matter than terrestrial resources at a given time, which makes them look significantly older, up to 1,200 years (e.g., ref. 3). Such an increase of apparent age has also been documented in some archaeological sites, such as the Iron Gates Gorge along the Danube River at the Serbian–Romanian border (3, 4). Therefore, a precise and quantitative dietary reconstruction is necessary to estimate this possible age increase due to freshwater consumption, especially as this Romanian directly dated modern human specimen overlaps in age with the latest Neandertals outside the Iberian peninsula (5). Therefore the possible incorporation of freshwater resources in the diet of the earliest European modern humans is not only an issue in the scenario of competition between Neandertals and modern humans but also an issue in the actual chronology of modern human migration in Europe and overlap duration between the two hominid forms.