In order to test the feasibility of using geochemical fingerprints like Sr- and Pb-isotopes and trace element systematics to trace the original living area of historic and possibly prehistoric humans we have analysed high quality bone material from geochemically contrasting areas.
A collection of skulls, collected from ossuaries from cemeteries in North- and South Tirol, in Austria and Italy, at the end of the last century, preserved at the Natural History Museum in Vienna satisfied our basic requirements for a possible success:
1-The skulls come from an area with high contrast in geochemical background (limestone, high grade metamorphic- and igneous rocks).
2-Inhabitants of mountainous regions tend to stick to their valleys during lifetime (and thereafter!) which should constrain the variation in the tracer composition.
3-The collection of bones is pre-industrial which is especially important for Pb isotopes (e.g. contamination with petrol lead).
4-The skulls have been buried for only limited time thus lowering the risk of contamination by the soil during the period the skull was buried at the cemetery.
Methods employed: TIMS (Sr isotopes), ICP-MS (Pb isotopes, trace elements and REE), IR spec., Xray Diff. (all at BFPZ Arsenal) and thin section histological analysis (at Nat. Hist. Museum).
The results from our pilot study of ten skulls from five geological different locations show a remarkable contrast in geochemical parameters in the skulls coming from each of the different areas.
Skulls from people living in limestone areas in the Northern and Southern Alps have Sr isotopic ratios clustering around 0.71 which resembles seawater whereas skulls from inhabitants of the high grade metamorphic terrains show elevated Sr isotopic ratios from 0.713 to 0.735. Pb has very specific concentrations in the skulls for each of the five different areas ranging from 6 to 60 ppm dry weight. The Pb isotopic ratios are very constant however which indicates a source with comparable composition in the study area. The light rare earth elements (e.g. La an Ce) exhibit relatively low values in the limestone areas ( around 100 ppt) and up to 500 ppt in the high grade metamorphic terrains.
On the promising results of this study we will analyse more skulls from Tirol which will provide us with a geochemical-skull reference map of the Tyrolean area which may enable us to trace the origin of older human remains in the area. Another spinoff of this study is that it provides a pre-industrial reference for environmental toxicologists for the impact of anthropogenically produced heavy metals in industrially exposed bone material.