Deciphering ancient diets from parasite DNA in people’s poop

Hopefully you’re not eating as you read this. If you are, however, future researchers may be able to figure out what you munching on, assuming you had some other organisms enjoying the meal with you. While not as widespread today, many meals can be unknowingly shared with parasitic worms in people’s digestive tracts. Those worms’ eggs are then… deposited in toilets, creating quite the treasure trove of data for researchers. A recent study of various ancient European latrines has even been able to recover DNA from digested food and eggs, adding a new level of detail to our understand of historical diets.

Deciphering dining habits from people’s dung

Researchers dug through toilets from the Middle East to Scandinavia, spanning not just geography, but time periods as well. From the 2500-year-old samples from Bahrain to more recent, 300-year-old poop from the Netherlands, they found that the majority of the parasitic eggs came from species that were transmitted directly between humans, such as pinworms. This wasn’t a huge surprise, as these parasites have specifically evolved to be easily passed between one person’s… unwashed hands to food very easily.

Knowing that people were in contact with other people wasn’t a huge insight, of course. More revealing was the number of eggs from parasites that don’t specialize in human infections. It’s suspected that these eggs were more likely picked up from eating under-cooked pork and fish that had been carrying parasites when they were alive. DNA tests also found revealed the non-worm portions of people’s meals, which generally supported notions of geographic trends in cuisine. For instance, cabbage and buckwheat turned up in northern Europe, while fin whales were apparently on the menu in medieval Denmark.

Tracking worms’ travel between towns

This isn’t the first study to dig through ancient people’s poop to identify components of their diets, but the use of so-called ‘shotgun’ DNA sequencing may open up new avenues of research. In many samples, the mitochondrial DNA was recovered from parasites’ eggs, in addition the nuclear DNA. Because mitochondrial DNA is (almost) only inherited from an organism’s mother, it can be used to trace specific family relationships over time. This means that researchers may soon be able to not only find parasites, but map out how and when they spread from one town to another. This can then help us understand a how people traveled long before they could meticulously document every moment and meal themselves.

Source: Parasite eggs from ancient latrines hint at people's past diets by Public Library of Science, Phys.org