NEW YORK — Miners in Iron Age Austria ate blue cheese and drank beer, according to a microbiome analysis of ancient feces.
Though human feces tend to deteriorate quickly, certain conditions like that of a salt mine in Austria lend themselves to their preservation. Mining at the Hallstatt salt mountains — now a UNESCO World Heritage area — dates back to the late Bronze Age and has provided scientists a glimpse into daily life during the Bronze and Iron Ages.
Examining the gut microbiome of paleofecal samples dating back to those eras, an international team of researchers found that ancient individuals living then likely ate carbohydrate-rich diets and had gut microbiomes more similar to those of modern, non-westernized individuals up through the Baroque Period. As they also reported in Current Biology on Wednesday, the researchers spotted fungi in one sample from the Iron Age that are associated with food fermentation, in particular blue cheese and beer, providing the earliest evidence of their consumption in Iron Age Europe.
"These results shed substantial new light on the life of the prehistoric salt miners in Hallstatt and allow an understanding of ancient culinary practices in general on a whole new level," first author Frank Maixner from the Institute for Mummy Studies at EURAC Research in Italy wrote in an email. "It is becoming increasingly clear that not only prehistoric culinary practices were sophisticated, but also that complex processed foodstuffs as well as the technique of fermentation have held a prominent role in our early food history."
The researchers focused their analyses on four paleofecal samples from the mine. Radiocarbon dating indicated that one was from the Bronze Age, two were from the Iron Age, and one was from about 1720 to 1783 A.D., which falls around the Baroque Period. A protein analysis of the samples uncovered enzymes involved in digestion, supporting the idea that endogenous biomolecules were present.
Further, shotgun DNA sequencing of the samples generated millions of reads that belonged to bacteria, typically members of the Firmicutes and Bacteroidetes phyla. Common species included Bifidobacterium angulatum, Lactobacillus ruminis, and Catenibacterium mitsuokai.
In a comparison with more than 820 contemporary microbiomes, the paleofecal samples, including the Baroque Period samples, clustered with stool samples from modern, non-westernized individuals whose diets largely include unprocessed food and fresh fruit and vegetables.
"This may indicate a shift in the gut community composition of modern westernized populations due to quite recent dietary and lifestyle changes," Maixner said.
Both microscopic and genomic analyses of the paleofeces indicated that the miners consumed millet, barley, and wheat, as well as wild fruit and some meat.
One Iron Age sample also included a high level of Penicillium roqueforti and Saccharomyces cerevisiae proteins, which prompted the researchers to map that sample's reads against the reference genomes of those two fungi.
By comparing these putative P. roqueforti and S. cerevisiae strains to sequences from other, modern strains, the researchers found that the P. roqueforti strain was most similar to strains used in blue cheese production, while the S. cerevisiae strain was involved in beer fermentation, which the researchers suspected was likely a pale beer.
"Genome-wide analysis indicates that both fungi were involved in food fermentation and provide the first molecular evidence for blue cheese and beer consumption during Iron Age Europe," Maixner added.
The researchers plan to next analyze additional paleofecal samples from Hallstatt to investigate whether other fermented foods might have been consumed as well as to examine the effects of nutrition on the makeup of the gut microbiome at different points in history.