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Iron Age Populations Ate Blue Cheese and Drank Beer, Their Feces Suggest

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Analysis of fecal samples from the Bronze Age, Iron Age and the Baroque period provide new insights into the diet and gut microbiomes of ancient populations. The study – published in Current Biology suggests that Iron Age populations enjoyed the consumption of blue cheese and beer.

Mining for ancient poop

Fecal samples can reveal a lot about a person. They can also reveal a lot about people from the past, if the samples are thousands of years old. While it may sound unlikely that poop could withstand the test of time, if the conditions are right, it can be perfectly persevered for thousands of years. This is known as a paleofeces.

The Hallstatt salt mines of the Austrian UNECSCO World Heritage area are an integral hub for researchers that want to study ancient populations. "The high salt concentrations and the constant annual temperature of ~8 °C inside the isolated Hallstatt mines have perfectly preserved organic archaeological artefacts, including clothing, mining tools and paleofeces material," Frank Maixner, coordinator at the Eurac Research Institute for Mummy Studies in Bolzano, told Technology Networks.

Maixner is the first author of a new study published in Current Biology that applied interdisciplinary methods to analyze ancient fecal samples obtained from the Hallstatt mines. The samples date back to the Bronze Age (1297-1122 BC), the Iron Age (650-544 and 694-542 BC) and the Baroque period (18th century AD).

The study rationale, Maixner explained, was influenced by a simple philosophy: you are what you eat. "Knowledge on our dietary history is very scarce and mainly provides insights into the main food components, providing limited information on culinary practices. It is fascinating to better understand the composition of historical meals since this provides major information on the life and health of ancient societies," he said.

Questions such as: How sophisticated were the meals consumed? Or, how much food was processed? are important to answer for past populations, as they can also be applied to modern culinary practises. This is especially relevant when you consider our growing knowledge of the link between diet, lifestyle and our gut microbiome. Maixner emphasized: "Our work with our partners was based on the conviction that paleofeces material harbors a huge potential to investigate our dietary past and to better understand the evolution of our gut microbiome."

A comprehensive analysis

The research team adopted microscopic, metagenomic and proteomic analyses to reconstruct the nutritional patterns of the individuals that left the samples behind, and their gut microbiomes. Discussing their choice of methods, Maixner said, "Earlier archaeological, archaeobotanical and archaeozoological research on the prehistoric paleofeces from the salt mines had already demonstrated the large potential for gaining insights into early human diet and health. Adding biomolecular research methods to this interdisciplinary approach promised new and fundamental insights. It was also clear from the start that substantially new insights could only be gained via thoroughly integrated interdisciplinary approaches combining DNA analysis and proteomics with archaeology, botany and zoology."

Reconstructing the diet of ancient populations

The analyses provided rich insights into the diets of the ancient populations. Their carbohydrate-rich plant-based diet was supplemented with blood-rich animal tissues – such as muscle and liver – from cattle. The most surprising finding, Maixner described, was the molecular trace of two fungi species in the Iron Age samples: Penicillium roqueforti and Saccharomyces cerevisiae. This indicates that there was consumption of fermented food and beverages – such as blue cheese and beer – in Iron Age Europe. "The Hallstatt miners seem to have intentionally applied food fermentation technologies with microorganisms which are still nowadays used in food industry," Maixner said.

How can the ancient population's utility of the fungi to ferment foods be deduced from the fecal samples? The fungi possess genomic traits that resemble cultivates used in the food industry today. "They seem to have undergone a selection process that makes them suitable [for] fermentation. Therefore, we assume that these fungi were part of an early fermentation culture," Maixner added.

The samples from the Baroque period revealed gut microbiome structures akin to modern non-Westernized individuals that eat a diet comprising fresh fruits, vegetables and unprocessed foods. This detail, Maixner noted, might indicate a shift in the gut composition of modern Westernized populations due to recent dietary and lifestyle changes.

There is a limitation to the work that the authors highlight in the paper, which is the small sample size that prevents generalizations from the findings. The team hope that, in the future, lipid and archaeological evidence (such as fermentation vessels) will be identified that further support their current findings.

"The Natural History Museum Vienna has been doing archaeological research in this fascinating World Heritage Area for decades and this has contributed substantial insights into working and living conditions in the Bronze Age and Iron Age and forms the basis for the current studies. From our archaeological point of view, we see these new results as vital. We now see that culinary practices were even more sophisticated than hitherto assumed and this hints at the substantial importance of processed foods already in prehistory," added Dr. Kerstin Kowarik, project researcher at the National History Museum, Vienna.

The next steps for Maixner and colleagues include analyzing additional Hallstatt paleofeces from a broader range of time periods to extend their initial observations.

Frank Maixner was speaking to Molly Campbell, Science Writer for Technology Networks.

Reference: Maixner F, Sarhan M, Huang K et al. Paleofeces analyses indicate blue cheese and beer consumption by Iron Age Hallstatt salt miners and a non-Westernized gut microbiome structure in Europe until the Baroque period. Current Biology. 2021. doi: 10.1016/j.cub.2021.09.031