If you’ve ever visited a museum like New York's American Museum of Natural History, you may have noticed a strange—yet oddly fascinating—relic on display: a shrunken human head. Artifacts like these may appear to be bloody battle trophies, but as the Smithsonian Channel explains, they once served as protective talismans for the Shuar people of Ecuador.

The Shuar are an indigenous people who live in the remote jungles of the Amazon. Long ago, they beheaded their enemies, and shrunk their over-the-shoulder remains by defleshing, simmering, and searing them with hot stones and sand. They also sewed the eyes closed, and pegged or sewed the mouth and nostrils shut. These creations were known as tsantsas.

“The Shuar believe in spirits,” explains Anna Dhody, a forensic anthropologist and curator of the Mütter Museum in Philadelphia, in the video below. “They believed that the spirit of their enemy could still harm them after death, and that they had to take preventative measures. So by taking the head of their enemy and creating these very special tsantsas, they could actually, effectively seal the spirit of their defeated enemy in the head.”

Learn more about the history of the practice below.