1 Department of Physics and Astronomy, Faculty of Science, Aarhus University, Aarhus University2 Department of Physics and Astronomy, Science and Technology, Aarhus University3 Department of Physics and Astronomy, Science and Technology, Aarhus University
Reconstruction of ingredients and radiocarbon dating of Mesolithic pottery
Pottery was a remarkable innovation for the Terminal Mesolithic Ertebølle society of southern Scandinavia: Boiling in vessels over direct heat made food resources available that otherwise are indigestive, while preserving all nutrients in the liquid. Did this innovation occur contemporaneously throughout northern Germany, or were inland groups some hundreds of years ahead of those at the coast? Reliable dating is an important precondition for identifying the origin of pottery, as it has to be known which other cultural groups were contemporaneous with the Ertebølle culture. 14C-dating of pottery uses charred food remains (“food crusts”) that are frequently found on Ertebølle pottery. However, crusts made of freshwater food can result in radiocarbon ages that are too high. Freshwater systems with hard water, a high content of dissolved minerals, contain considerable amounts of “14C-dead” carbon. Those minerals originate from carbonate rocks, having infinite ages compared to the 14C time scale. This effect is called the “hardwater effect”. Thus the question of what Ertebølle people cooked in their pots is not only interesting in itself, but also helps in finding out whether the radiocarbon dating is affected by the hardwater effect. I used the stable isotopes of carbon and nitrogen, 13C and 15N, to identify the foodstuffs that formed the crust. Experiments with copies of stone age vessels were conducted to test the reliability of the method: Was it possible to retrieve the recipe of a food crust by stable isotope measurements? Is a fish’s reservoir age the same as that of the food crust made from this fish? In addition to recent materials, I examined archaeological remains from the two inland sites Kayhude and Schlamersdorf, where the presumably oldest Ertebølle pottery had been found. The fact that this pottery was much older than pottery from coastal Ertebølle sites, combined with the sites being located close to freshwater rivers, aroused suspicion: Is the oldest Ertebølle pottery really that old? Measurements of food crusts, terrestrial and fluvial samples from the same context gave the answer.
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Fourth International Symposium on Biomolecular Archaeology, 2010