Medieval Latrines Hold Clues About Intestinal Health in Europe and Middle East

(CN) — Researchers digging through the contents of two medieval latrines have turned up new information about the intestinal health of ancient communities in what is now Europe and the Middle East, according to a new study released Sunday. 

The findings provide rare insight into the microbiomes of pre-industrial, agriculture-based communities and could help contemporary scientists better interpret the microbial diversity in nations around the world, researcher Piers Mitchell of Cambridge University said in a statement attached to the study.

"These latrines gave us much more representative information about the wider pre-industrial population of these regions than an individual faecal sample would have," Mitchell said. "Combining evidence from light microscopy and ancient DNA analysis allows us to identify the amazing variety of organisms present in the intestines of our ancestors who lived centuries ago."

Prior research has established that microbiomes — the communities of bacteria, fungi and parasites in our bodies — of industrial societies differ greatly from those of hunter-gatherer communities.

Scientists have linked these differences to the rise of modern diseases such as obesity, various allergies and inflammatory bowel syndrome. 

Ancient latrines and their desiccated excrement contents have become bio-molecular goldmines for scientists seeking to learn about the intestinal parasites carried by our ancestors. 

"Microscopic analysis can show the eggs of parasitic worms that lived in the intestines, but many microbes in the gut are simply too small to see," Mitchell said. "If we are to determine what constitutes a healthy microbiome for modern people, we should start looking at the microbiomes of our ancestors who lived before antibiotic use, fast food, and the other trappings of industrialisation."

Researchers combed through the contents of latrines in both Jerusalem and Latvia, according to the study published Sunday in the journal Philosophical Transactions of the Royal Society B.

The latrine in Jerusalem examined by researchers is located in the Christian Quarter of the Old City and dates back to the 15th century, according to the study.

“The city had been continuously inhabited for several thousand years,” the study said. “The cesspit was fed by two separate chutes from separate latrines, suggesting multiple different users from more than one household.”

A challenge for scientists was separating ancient feces from the gut contents normally found in soil.

Study co-author Kirsten Bos of the Max Planck Institute for the Science of Human History said in the statement she was initially concerned the desiccated contents of ancient latrines would reveal too little information.

"At the outset we weren't sure if molecular signatures of gut contents would survive in the latrines over hundreds of years,” she said. “Many of our successes in ancient bacterial retrieval thus far have come from calcified tissues like bones and dental calculus, which offer very different preservation conditions. Nevertheless, I was really hoping the data here would change my perspective."

An analysis of the gut content of a medieval latrine in Riga, Latvia revealed a host of bacteria including a microscopic fish tapeworm egg, according to the study. 

Researchers also identified a range of fungi, parasitic worms, bacteria, archaea, protozoa and other organisms from the latrines, including some that are found in the intestines of contemporary humans. 

"It seems latrines are indeed valuable sources for both microscopic and molecular information," Bos said.

Susanna Sabin of the Max Planck Institute, co-leader of the study, said in the statement researchers compared the DNA retrieved from latrines with microbiomes of industrial and hunter-gatherer communities.

"We found that the microbiome at Jerusalem and Riga had some common characteristics — they did show similarity to modern hunter gatherer microbiomes and modern industrial microbiomes, but were different enough that they formed their own unique group,” Sabin said. “We don't know of a modern source that harbours the microbial content we see here."

Bos said in the statement researchers have remaining questions about the diverse spectrum of microbiomes.

"We'll need many more studies at other archaeological sites and time periods to fully understand how the microbiome changed in human groups over time," Bos said. "However, we have taken a key step in showing that DNA recovery of ancient intestinal contents from past latrines can work."

Researchers did not immediately respond to a request for further comment on the study.

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