Gunk from medieval bathrooms revealed people suffered from parasites

What could you possibly find in a toilet that’s been out of order for hundreds of years? Some ghastly things might be hiding in there, and it’s not what you might think.

There were obviously no porcelain seats or advanced plumbing in latrines 800 years ago. You went, and countless others went after you, unknowingly leaving behind evidence of what was crawling in an entire community’s guts. Think of all those TV commercials that relentlessly insist on probiotics for gut health. Probiotics might be trending, whether in pill or yogurt form, but they do help balance the intestinal microbiome—everything that lives in your guts. Scientists have now been able to find out what was lurking in the microbiomes of two cities during the 14th and 15th centuries, and it’s ugly.

Parasites thrive when you don’t have proper sanitation. The Middle Ages spawned the bubonic plague, so it has nowhere near the cleanest reputation in history. Cesspits from Jerusalem and Riga, Latvia are giving us a closer look the microbiomes of pre-industrial agricultural societies that might be able to provide insight into our own insides. While industrialization has been associated with inflammatory bowel disease, food allergies and obesity, microbial DNA in coprolites (fossilized feces) recovered from long-abandoned latrines has revealed that Medieval human microbiomes were plagued by parasites.

“Together, these findings provide a first glimpse into the rich prokaryotic and eukaryotic intestinal flora of pre-industrial agricultural populations, which may give a better context for interpreting the health of modern microbiomes,” said Kirsten Bos, a specialist in ancient bacterial DNA from the Max Planck Institute, who recently co-led a study published in Philosophical Transactions of the Royal Society B.

Gnarly things revealed themselves under the (literal) microscope. The eggs of parasitic worms were easily detected with microscopic analysis, but there were other

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