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 Allerod 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. (c) 2009 Elsevier Ltd. All rights reserved.