Testing the ‘Laacher See hypothesis’: tephra as dental abrasive

In a series of recent studies, changes in material culture and settlement pattern in the Late Glacial of Northern Europe have been linked to the eruption of the Laacher See volcano. This eruption occurred c. 13,000 years ago towards the end of the Allerød chronozone. It is argued that the tephra fall-out from this eruption set in motion significant demographic fluctuations along the northern periphery of Late Glacial human settlement and that these led to a number of material culture transformations. In particular, the emergence of the regionally distinct techno-complexes with large tanged points – the Bromme culture in southern Scandinavia and the Perstunian culture in northeastern Europe – and the temporary abandonment of central European regions are thought to relate to this eruption. While numerous archaeological datasets are in accord with this ‘Laacher See hypothesis’, the forcing mechanism or mechanisms that brought about these archaeologically visible changes have remained largely unexplored. A particular challenge is to explain how some of the culture-historical effects of the Laacher See eruption seem to change or become more pronounced with distance from the eruptive centre. We here investigate one potential middle-range link between the Laacher See eruption and Late Glacial fauna and foragers: tephra as dental abrasive. We use instrumented nanoindentation to quantitatively investigate tephra from a number of sites covering the medial and distal fall-out zones as well as the dental enamel of Homo sapiens and key prey species of Late Glacial foragers. Our results show that the Laacher See tephra contained particles roughly twice as hard as even the hardest portions of any of the teeth investigated. We also suggest that fluoride-induced weakening of dental enamel may have further aggravated tooth wear. These mechanisms may have acted in concert to produce elevated levels of, in particular, animal mortality, which in turn may have led to an abandonment of the affected landscapes.     

The Laacher See-eruption (12,920 BP) and material culture change at the end of the Allerød in Northern Europe

A number of recent papers have argued that summed probability distributions of radiocarbon dates calibrated with the CALPAL software package can be used to identify population trends in prehistory. For instance, Gamble et al. (Gamble, C., Davies, W., Pettitt, P., Richards, M., 2004. Climate change and evolving human diversity in Europe during the last glacial. Philosophical Transactions of the Royal Society of London, Series B 359, 243–254; Gamble, C., Davies, W., Pettitt, P., Richards, M., 2005. The archaeological and genetic foundations of the European population during the Late Glacial: implications for 'agricultural thinking'. Cambridge Archaeological Journal 15, 193–223.) have demonstrated that during the European Late Glacial, demography was more variable than hitherto acknowledged. Building on this work, this paper presents evidence that the large, but so far largely ignored eruption of the Laacher See-volcano, located in present-day western Germany and dated to 12,920 BP, had a dramatic impact on forager demography all along the northern periphery of Late Glacial settlement and precipitated archaeologically visible cultural change. In Southern Scandinavia, these changes took the form of technological simplification, the loss of bow-and-arrow technology, and coincident with these changes, the emergence of the regionally distinct Bromme culture. Groups in north-eastern Europe appear to have responded to the eruption in similar ways, but on the British Isles and in the Thuringian Basin populations contracted or relocated, leaving these areas largely depopulated already before the onset of the Younger Dryas/GS-1 cooling. Demographic models are used to link these changes to the Laacher See-eruption and this research demonstrates that we cannot sideline catastrophic environmental change in our reconstructions of prehistoric culture history.     

Testing the ‘Laacher See hypothesis’: a health hazard perspective

It has recently been suggested that the Laacher See volcanic eruption, which occurred around 13,000 years ago, initiated significant demographic fluctuations along the northern periphery of Late Glacial human settlement and that these led to a number of material culture transformations. The origins of the Southern Scandinavian Bromme culture and the northeastern European Perstunian culture as well as the temporary abandonment of Central European regions have been linked to this eruption. However, it remains unclear precisely which aspects of the eruption stimulated Late Glacial foragers to abandon their traditional ways of life. Paradoxically, the culture–historical impact of the eruption appears greater further away from the eruptive centre. Here, we investigate one potential middle-range link between the Laacher See eruption and Late Glacial fauna and foragers: tephra as a health hazard. We use laser-diffraction particle-size analysis to quantitatively investigate tephra from one site with a secure Late Glacial archaeological deposit. In addition, we use values previously reported in the literature and a predictive model to calculate the hazard potential along a transect of two of the three major Laacher See tephra fans. Our results show that the Laacher See tephra may have posed a potential health hazard and that its hazard potential may have increased with distance from the vent. To our knowledge this is the only study that attempts to quantify the changing grain-size composition of tephra fall-out longitudinally in this way, at least with regard to a prehistoric eruption. We close by discussing, more speculatively, other possible health-pertinent effects of the Laacher See eruption and suggest ways in which future work can further evaluate the impact of this eruption on Late Glacial populations.