To make sure certain people didn't rise from the grave to feast on the living, villagers in 17th- and 18th-century Poland buried them with sickles across their throats or rocks in their jaws, and researchers think they now know why. According to a study published in PLoS ONE, the suspected vampires were not immigrants to the area but locals who probably perished in the cholera epidemics that swept the region at the time. Ancient lore says being the first to perish in an epidemic is one of the things that can turn a person into a vampire, study co-author Lesley Gregoricka tells LiveScience. "People were up close and personal with death at this point, but didn't have a good way to explain what was happening," she says.
"People of the post-medieval period did not understand how disease was spread, and rather than a scientific explanation for these epidemics, cholera and the deaths that resulted from it were explained by the supernatural—in this case, vampires," says Gregoricka, a bioarchaeologist at the University of South Alabama, in a press release. Dying a violent death or being an outsider also put one at risk of becoming a vampire, according to lore, but the bodies bore no signs of violence and testing revealed they were from the area. The sickles were in place to decapitate the body if it tried to rise, and rocks or bricks were placed to prevent them from feeding, the study says—though strangely enough, the "vampires" weren't segregated in the cemetery but were buried among other villagers. (In this "vampire grave," the deceased had a stake driven through his heart.)