The surprising artifact could be evidence of fertility rituals—or just one of history’s strangest good luck charms.

Ellen Green, a postgraduate researcher with the University of Reading, analyzed “Quarry 1” from the Nescot site and found “it contained one of the largest assemblages of human and animal bone ever recorded from a single Romano-British feature,” according to the study.

A bio-archaeologist with the University of Reading, in the U.K., has found an ancient dog's red-painted penis bone along with a trove of other bones, in an ancient Roman era quarry shaft. In her paper published in the Oxford Journal of Archaeology,

In 2015, archaeologists working at a site called Nescot in the town of Ewell, roughly 12 miles (19 kilometers) south of London, discovered a 13-foot-deep (4 meters) shaft dug into the limestone. From it, they recovered a large mass of human and animal bones that date to between the late first and early second centuries.