For many archaeologists, that might have been the end of the tusk's usefulness. Not for Deter-Wolf. He gathered several of the fragments and later turned them into tattoo needles, carving each with flint and smoothing it on sandstone. But when he tried tattooing a colleague with one of them, the result was disastrous.

A few years ago, a man walked into Aaron Deter-Wolf's office at the archaeology department in Nashville, Tennessee, carrying a two-meter fragment of a mastodon tusk. He had spotted the relic protruding from a riverbank and had sawed off the exposed section. Because the tusk had been removed in this way, its scientific value was greatly diminished -- so Deter-Wolf began using it as a teaching aid in elementary school lectures. That is, until a child accidentally dropped it, causing its outer layers to shatter.

For many archaeologists, that might have been the end of the tusk's usefulness. Not for Deter-Wolf. He gathered several of the fragments and later turned them into tattoo needles, carving each with flint and smoothing it on sandstone. But when he tried tattooing a colleague with one of them, the result was disastrous. Microscopic cracks in the ivory snagged the skin with every stroke. "It was a bloody mess," he recalls.

By day, Deter-Wolf surveys archaeological sites to assess the impact of new construction projects. But in his spare time, he is one of the world's leading experts on ancient tattooing -- a field that, until recently, was often dismissed but is now recognized as essential to understanding global cultures. Because the topic was once considered marginal, Deter-Wolf belongs to a new generation of researchers demonstrating that tattooing was far more widespread than archaeologists once believed, revealing new meaning in a historically suppressed art form.

The resistance to tattoo research has colonial roots: missionaries and colonial authorities once viewed it as barbaric. When archaeology emerged as a discipline in the 19th century, its practitioners inherited this bias, rarely mentioning tattoos except as marks of the "savage" or "deviant." Deter-Wolf discovered early in his career that this attitude persisted well into the 21st century.

Now 49, he began as a Mayanist before turning his focus to the precolonial Southeast of the United States. His personal connection to tattooing -- he has about a dozen himself -- fuels his side research. After organizing his first conference on ancient tattooing in 2009, an older attendee pulled him aside and quipped, "There are more tattooed grad students with ancient art than there were in the entire ancient world." "He was completely wrong," Deter-Wolf says. "The evidence wasn't hidden -- it just hadn't been taken seriously." This lack of engagement, he argues, has caused archaeologists to miss key insights about the people they study, since tattoos throughout history have marked group identity, rites of passage, and spiritual power.

One way Deter-Wolf sought to overcome academic skepticism was by investigating how to identify tattooing tools among archaeological finds. The challenge is that a sharp object unearthed at a dig could have been used to tattoo -- or merely to pierce leather or sew. To distinguish between them, Deter-Wolf assembled a group of like-minded archaeologists and researchers, and together they conducted a series of experiments over nearly a decade -- some tightly controlled, others spontaneous. For each experiment, he crafted tattooing implements from materials ancient cultures might have used: bird feathers, deer bone, fish teeth, cactus spines, and yes, shards of mastodon ivory. They applied either modern ink or a charcoal-and-water mixture, likely similar to what ancient peoples used. The tools were then tested on volunteers, on pigskin -- and on Deter-Wolf's own skin.

The feather proved too soft -- "like tattooing with a felt-tip pen," he says. The ivory was a failure. But the cactus spines and bone worked remarkably well; bone's porous texture held ink efficiently. Under microscopic examination, telltale wear patterns appeared: rounded tips, pitting, and embedded charcoal particles. Today, these findings help archaeologists distinguish ancient tattooing needles from other sharp artifacts.

Some revelations, however, come only from ancient bodies. Take the case of Ötzi the Iceman, a 5,300-year-old mummy discovered in the Alps in 1991. Initially, researchers thought his tattoos had been made by cutting the skin with sharp stones and rubbing charcoal into the wounds. Decades later, Deter-Wolf designed an experiment to test that theory, collaborating with traditional Inuit tattooist Maya Sialuk Kock Madson from Greenland and New Zealand tattooist Daniel Riday. Using eight different techniques -- including puncturing with a needle and the "cut and rub" method -- Riday created eight identical tattoos on his left leg. He recorded the pain and healing time for each. Some methods took only minutes; one Inuit technique using an ink-soaked thread lasted three grueling hours. Afterwards, his leg looked like "Swiss cheese."

Deter-Wolf compared magnified images of Ötzi's tattoos with Riday's. He saw that the "cut and rub" method produced lines tapering at the ends, while needle-punctured tattoos had rounded termini -- matching Ötzi's precisely. The conclusion: the Iceman's tattoos were made by careful puncturing, not cutting. This study not only illuminated Ötzi's culture but also produced the first published reference guide to the microscopic appearance of different tattooing techniques -- now used by archaeologists examining other mummies.

Egyptologist and Deter-Wolf's collaborator Anne Austin notes that tattoos can convey information about societies that written records cannot. "What you inscribe on skin is different from what you write on paper," she says.

Her findings among Egyptian mummies reveal women with more than 30 tattoos -- hieroglyphic symbols, musical instruments, serpentine deities -- evidence that these women held priestly roles and that their voices were imbued with sacred power.

To extract new data from ancient mummies and tools, tattoo archaeologists increasingly employ advanced imaging technology. Deter-Wolf and his Canadian colleague Benoît Robitaille used infrared cameras to detect hidden ink in a large collection of coastal Peruvian mummies, some 2,400 years old. The ink had been obscured by the skin's darkening over time. They found that the religious iconography in these tattoos remained remarkably consistent for nearly two millennia -- suggesting that local beliefs persisted even through invasions and turmoil.

Deter-Wolf says the potential for new discoveries is nearly limitless. In the past five years alone, more evidence of tattoos on mummies has been uncovered than in the previous 150 years.