Findings from the toilet: how archaeologists tracked down a medieval traveler

Fascinating what archaeologists find out even after centuries: For example, Ötzi knows that he did not tolerate milk, that he had a penchant for tattoos and that he ate a poisonous fern shortly before his death. The man died from the ice more than 5,000 years ago. Now archaeologists have tracked down a traveler from the Middle Ages, only on the basis of his excrement - and they contained a surprising detail about the man.

His legacies were discovered in a 700-year-old latrine in Lübeck. Archaeologists had extensively studied the so-called foundation district between 2009 and 2016 and dug up more than 200 buildings and about a hundred latrines. The evaluations run until today.

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"The latrines provide us with intimate details about life in medieval Lübeck," says archaeologist Dirk Rieger, who led the excavations. The examined sewers belong roughly to the period around 1200 to 1350 and compromise above all the wealthy merchants who used them: In their toilets it was swarming with parasites, as microscopic photographs show.

The chance hit

"We have found millions of eggs of thread and tapeworms," ​​says Rieger. And that's exactly what the archaeologists put on the track of the traveler. Because the cell walls of the worm eggs are so robust, DNA molecules are often retained in them. And the genetic material analyzed came not only from the parasites, but also from their host. In this case, by the people who used the latrines.

In cooperation with Patrik Flammer and Adrian Smith of the University of Oxford, the researchers from Lübeck compared the DNA samples with those from other sites in Great Britain, the Czech Republic and Switzerland. "And that's where the chance hit us," says Rieger. The DNA residues from Lübeck fit perfectly with a sample from the English Bristol.

For the archaeologists it was clear: The same person must have gone around the year 1300 both in Lübeck and in Bristol to the toilet. While it is theoretically possible that a human DNA trace would fit different individuals, archaeologists also believe that coincidence is out of the question as they also found the genome of the parasite in Bristol.

Businessman traveling

The traveler from the Middle Ages did not suspect that a fish tapeworm had lodged in his intestine. Although the parasites can survive decades in a human being and can grow up to twenty meters long, those affected often do not notice the unwanted roommate.

The researchers suspect that the man was traveling as a merchant. Lübeck was then considered the most influential trading power in the Baltic Sea and was part of the powerful Hanseatic League. "Unfortunately, we can not say whether it is a Lübeck, who traveled to Bristol or vice versa, or whether he comes from another city," says Rieger.

In any case, the finds from the latrine proved that Lübeck and Bristol had contacts with each other. "And we were able to prove that alone with the samples from the latrines, without any written sources," emphasizes Rieger.

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The parasites in the sewers also reveal what the people of Lübeck liked to eat. "We now know, for example, that the Lübeck merchants changed their diet between 1300 and 1325," says Rieger. Instead of fish, humans have increasingly eaten beef, as the analysis of the prevailing parasites shows. In the period before 1300, therefore, fish tapeworms dominated, in the aftermath then beef tapeworms, write the researchers in a study that was recently published in the journal "Proceedings B" of the British Royal Society.

"The Lübeck must have eaten raw fish and beef," says Rieger. After all, humans can only get infected with tapeworms by eating meat heated to less than 70 degrees. Why the people of Lübeck first preferred fish and later beef is unclear. In any case, it is more a matter of food of the richer population. "In the founding district, where the excavations took place, lived mainly wealthy merchants," says Rieger.

Compare with plague mass grave

The researchers are now hoping for further insights into life in medieval Lübeck. "The DNA samples could, for example, answer the question of how many people had to share a latrine, which diseases were rampant and how the viruses and bacteria changed by mutations," says Rieger.

In addition, the researchers want to compare the DNA samples from the latrines with those from a mass grave complex that belongs to about the same time. "Maybe we can even reconstruct family relationships," says Rieger. Since the mass burials were found with around a thousand dead in the Lübeck Holy Spirit Hospital, the researchers suspect that there were buried pest mortals.

Incidentally, the excavations in the medieval sewers were not exactly appetizing for archaeologists. "They were real stink bombs," says Rieger. He had quickly got used to the smell. The consistency of the soil is reminiscent of brownish watt. There was no risk of infection in the work, the many pathogens in the sewers had long since died.