Archaeologists have discovered two knives that were fashioned from shark teeth about 7,000 years ago.

An international team of researchers uncovered the unique artifacts during excavations on the Indonesian island of Sulawesi. The island—the 11th-largest in the world—has a rich archaeological record dating back to prehistoric times, and it's home to some of the oldest known cave art in the world.

The modified shark teeth, described in a study published in the journal Antiquity, were found in archaeological contexts associated with the Toalean culture.

This enigmatic, foraging society is thought to have lived from around 8,000 years ago until an unknown period in the recent past.

One of the artifacts is a complete tooth with two holes drilled through the root, which was found at a cave site known as Leang Panninge. The other, uncovered at a cave called Leang Bulu' Sipong 1, features one hole, although it's broken and probably originally had perforations.

Both of the shark teeth are of similar size and came from tiger sharks that likely measured over 6 feet in length. Tiger sharks, found around the world in tropical to temperate latitudes, are named after the distinctive gray-striped pattern found on the sides of their bodies.

Tiger sharks can grow up to 18 feet long and weigh 2,000 pounds, making them the second-largest predatory shark in the world—behind great whites—and the fourth-largest overall, according to marine conservation advocacy organization Oceana.

Close examination of the ancient tiger shark tooth blades revealed that they had once been tightly fixed to a handle using plant-based threads and a glue-like substance. This adhesive was made from a combination of mineral, plant and animal materials.

The same method of attachment is seen in modern shark-tooth blades used by various cultures today throughout the Pacific region.

The ancient shark tooth blades were most likely used in warfare, or for ritual purposes, according to the study.

"Numerous societies across the globe have integrated shark teeth into their material culture. In particular, peoples living on coastlines (and actively fishing for sharks) are more likely to incorporate greater numbers of teeth into a wider range of tools," several authors of the study from Griffith University in Australia and Universitas Hasanuddin in Indonesia wrote in an article published by The Conversation.

"Observations of present-day communities indicate that, when not used to adorn the human body, shark teeth were almost universally used to create blades for conflict or ritual—including ritualized combat."

The latest finds represent some of the earliest archaeological evidence for the use of shark teeth in composite weapons—those made with multiple parts—anywhere in the world. Previously, the oldest known shark tooth blades dated back to less than 5,000 years ago.

Older modified shark teeth have been documented. For example, a solitary tiger shark tooth with a single perforation found in Buang Merabak in Papua New Guinea has been dated to around 39,500–28,000 years ago. But in such examples, the teeth were likely fashioned as personal ornaments, not weapons.

Finding shark teeth that have been modified and used by people is "not a very common" archaeological find, Michelle Langley, a professor of archaeology at Griffith University and one of the authors of the study, told Newsweek.

"We were able to collate all previous archaeological discoveries of utilized shark teeth into a single one-page table for our paper," Langley said. "And in the Pacific region, shark-tooth knives are very culturally significant in the recent and present day, so finding evidence that this form of tool is at least several thousand years old is incredible. It just goes to show how deep these traditions are in this region."

Update 11/06/23, 10:49 a.m. ET: This article was updated with comment from Michelle Langley.