We looked for signs of parasitic worm infection in people who lived in Cambridge, England during the Middle Ages. We compared two groups of people who had very different lifestyles: Augustinian friars and common laborers. The friars had better food and lived longer than the common people. They also were more likely to have access to running water and better toilets. Surprisingly, the friars had a higher worm infection rate! We think the reason might be that the friars used human poop to fertilize their vegetable gardens.