When the University of Cambridge began renovating a museum in 2017, it uncovered the remains of dozens of medieval monks. Dating as far back as 1290, many skeletons still wore the weathered belt buckles—corroded remnants of the monk’s burial garb. They also had evidence of something much more insidious: the eggs of parasitic worms that were potentially wreaking havoc in the monks’ intestines while they were alive.
Although these men lived much more hygienically than the city’s citizens outside their community, they were much more likely to be riddled with parasites, a new study reveals. Their gardening practices may be to blame.
In medieval Cambridge, many citizens subsisted in squalor, living with livestock in cramped cottages and disposing of household excrement in communal holes in the ground called cesspools. By comparison, the Augustinian monks in the city lived a haughty life. Inside the monastery walls, gardens produced fresh produce and latrines were isolated. Many monasteries were even equipped with running water systems – a luxury lacking even in aristocratic households of the time – so that monks could wash their hands. Like many aspects of their lives, their focus on hygiene brought them closer to God.
This is perhaps why monks often outlive ordinary people. But no one had paid serious attention to whether monks were less susceptible to worms and other vermin, a common scourge of the time.
So Piers Mitchell, a palaeopathologist at Cambridge, and his colleagues turned to a find of monk skeletons that had turned up on their home turf. To determine whether the remains were affected by parasites such as roundworms and whipworms—which can cause severe damage to the digestive tract and even stunt growth in extreme cases—the researchers collected sediment around the pelvises of 19 skeletons dating from the 13th and 14th century.
As a control, they took samples from the monks’ skulls and legs, body parts that should have no signs of intestinal parasites. They also collected similar samples from 25 non-monastic skeletons buried around the same time in a rural parish about a kilometer from the monastery ruins. This parish cemetery served a predominantly lower-class congregation between the 12th and 14th centuries.
Back in the lab, the team put the samples under a microscope to look for remains of intestinal invaders. The parasitic worms themselves rotted away centuries ago. Instead, the researchers sifted the samples for microscopic worm eggs, which can linger in the sediment for centuries.
Nearly 60% of Cambridge monks were riddled with intestinal worms, the team reported today in International Journal of Paleopathology. They were almost twice as likely to be infected with parasites as their non-monastic neighbors.
Ironically, the monks’ better hygiene may be to blame, Mitchell believes. Because they collected their excrement in the toilet rather than dumping it in cesspools, the clergy may have recycled their own waste (or bought waste from townspeople) as fertilizer for their vegetable gardens.
Roundworms lay their eggs in human feces, Mitchell notes, so eggs in gardens can easily make their way to produce and then into the monks’ stomachs. As the worms hatched and wriggled their way through the monks’ digestive tract, they would cause abdominal pain and bowel movements. And as the worm-infested monks retreated to the toilet, they helped disperse the next generation of roundworm eggs into the monastery’s supply of fresh manure.
Less is known about the fertilization practices of the lower classes in the city. But without access to latrines, they may have been less likely to use human excrement for their gardens.
However, not all parasitologists understand that the structures in the monks’ pelvises are the eggs of medieval worms. Karl Reinhardt, an archaeoparasitologist at the University of Nebraska, Lincoln, who studies intestinal parasites preserved in the guts of mummies, noted that many eggs the team examined lacked the protective coats common to roundworms. “There are many oval structures in the fungal and botanical worlds that may be fakes of parasite eggs in the archaeological context.”
However, intestinal parasites predominated in medieval sites, according to the Cambridge researchers. Skeletons from this period show signs of having been ravaged by an array of tapeworms, flukes and single-celled protozoa that cause dysentery.
Although the monks’ remains are centuries old, Mitchell believes the take-home message from this find is timeless: “Don’t be the monk who fertilizes your lettuce with your own poop.”