A pair of tiger shark teeth uncovered in separate caves on the Indonesian island of Sulawesi are the oldest known examples of shark teeth employed as cutting implements. Based on the contexts in which the teeth were excavated, archaeologists Michelle Langley and Adam Brumm of Griffith University believe they are between 5,000 and 7,000 years old and were used by members of the hunter-gatherer Toalean culture, who lived in southwestern Sulawesi at the time.

Microscopic examination revealed that both artifacts are worn in ways consistent with piercing, cutting, and scraping flesh and bone. The team also detected traces of plant fiber in holes that had been drilled into the roots of the teeth as well as adhesive on the roots. They believe thread and glue secured the blades in hafts—a method used in recent times by people in the area to make shark-tooth blades. Given that shark teeth become blunt very quickly, the researchers suspect these knives were used for ritual conflict or warfare, not everyday cutting. “Such ritual and war knives are quite characteristic of this region,” says Langley. “Now we can scientifically demonstrate that this tradition has a history many thousands of years long.”