Parasites found in 12th-century feces recovered from a castle latrine tell us why so many crusaders died on their way to the Holy Land.

It may sound like a bunch of BS, but two researchers have unlocked clues about medieval famine by recovering centuries-old, petrified poop from a castle latrine.

In a recent study published in the International Journal of Paleopathology, doctors Piers D. Mitchell and Evilena Anastasiou of the archaeology and anthropology department at the University of Cambridge in the UK explained how they discovered and analyzed preserved feces in the Frankish castle of Saranda Kolones on the island of Cyprus.

The castle was built in 1191 and was only used by the crusading armies of King Richard I of England for 30 years before being destroyed by an earthquake. Researchers took samples from the castle latrine, suspended them in water to make a solution, and then passed the solution through small strainers.

They discovered roundworm and whipworm eggs in the poo samples, bringing to light the poor hygienic conditions the crusaders experienced. Past research shows that crusaders faced malnutrition during times of siege and famine, and the new discovery tells us why: Parasites competed with the crusaders for their bodies’ own nutrients.

Mitchell said his ancient data mining is important because learning about human health and disease in medieval times helps us understand what life was like back then. “Showing the kind of diseases crusaders suffered with helps us to understand why so many of them died on crusade expeditions from malnutrition and infectious disease,” he told Healthline.

In modern times, roundworm and whipworm infections can be treated with medications and generally are not fatal. But in medieval times, when coupled with malnutrition on long journeys, the parasites did many of the crusaders in. In fact, 15 to 20 percent of crusaders died of either malnutrition or infectious disease while on expedition, aided by an abundance of intestinal creepy-crawlies.

“Once hatched in the human intestines, the immature roundworms undergo an incredible migration, with the first stage larvae penetrating the blood vessels and appearing as second stage larvae in the liver within six hours after the initial infection,” the study authors wrote. “In the liver, the larvae develop into their third stage and they then migrate to the heart and lungs. Eight to 10 days after the original infection, the larvae burrow their way from the heart and lungs back to the small intestine, where they reach maturity. The mature female then starts to lay about 200,000 eggs per day.”

Female whipworms can release 2,000 to 10,000 eggs per day, the researchers added.

Mitchell hopes that by studying the composition of these ancient parasites modern-day researchers can develop more effective medications to treat this type of infestation.

“When we study ancient parasites it has the potential to help us understand how parasites may change in the future,” Mitchell said. “For example, if we look at the DNA in past parasites and compare with modern parasites, it can help us to work out in what way they are evolving over time, and so how they may look in the future. This is important, as there is no point making drugs that act on parts of a parasite that are in the process of changing.”

“Some types of parasites have been present in humans right from the start of our evolution,” Mitchell added. “These we inherited from other primates in Africa. However, some parasites only started to infect humans when our ancestors left Africa and migrated around the planet, and this brought them into contact with new parasite species.”

As for the “ick factor” involved in this type of hands-on research, Mitchell said it was really no big deal. “Once hundreds of years have passed, there is no nasty smell,” he said. “It just looks like soil.”