Abstract
The UNESCO World Heritage region Hallstatt-Dachstein/Salzkammergut represents one of Europe’s oldest cultural and industrial landscapes with salt mines in the Hallstatt mountain dating back at least to the 14th century BC. The site gave name to the Hallstatt Period (800 to 400 BC) of the Early Iron Age in Europe. The high salt concentrations and the constant annual temperature at around 8°C inside the isolated mine workings perfectly preserved organic archaeological artefacts (e.g. clothing, mining tools) that provide unique insights into the daily life of a progressive community in Hallstatt.
In order to reconstruct the diet of the former population and gain insights into the ancient gut microbiome composition, we subjected human paleofeces from the mining system to in-depth microscopic and metagenomic analysis. The microscopic survey identified bran and glumes of the Triticum/Hordeum type as one of the most prevalent dietary plant fragments. This highly fibrous, carbohydrate-rich diet was supplemented with proteins from broad beans and occasionally with fruits and nuts. The metagenomic analyses supported and further extended the microscopic results by identifying additional plant (walnut) and animal (bovine) diets. Furthermore, the metagenomic analysis allowed the reconstruction of ancient intestinal microbiomes and comparative analysis with modern gut microbiomes provided insights into the genetic diversity of selected gut bacteria (e.g. Prevotella copri). The observed decline in microbial diversity within millennia could be possibly due to dietary changes. Our observations will allow to establish hypotheses on the rise of modern diseases such as obesity that we can investigate in modern clinical studies.