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It all started with a Roman pot. A new laser imaging technique revealed Greek inscriptions on the pot that had been hidden, which surprised archaeologists. But when Judyta Bak, a Polish archaeologist from Krakow, read the study, she didn’t care much about the pot. She wondered what would be revealed if she shone the laser on the 100 mummies she was studying in coastal Peru, some of which are more than a millennium old.
Bak got in touch with Michael Pittman, who developed the laser technique, known as laser-stimulated fluorescence, which excites molecules on or below the surface of an object and can reveal hidden soft tissues without destroying them. He had used the technique to study details of Roman wall paintings, glass mosaics, and dinosaur fossils. Bak invited Pittman to come out to Huacho, a beach city on the central coast of Peru, a region known for the greatest documented number of mummy tattoos on Earth.
Bak had already identified tattoo designs on the mummies’ bodies, but these were blurred under standard white light due to ink bleed and decomposition. “We came up with a hypothesis that the skin should glow,” under the laser light, but that the tattoos would not, Pittman says. “Perhaps with this contrast we could see more. That was the theory.”
They found what they were looking for: Under the laser’s beam, beautifully detailed geometric patterns and animal shapes, mostly birds and monkeys, popped from the mummified skin. The real surprise lay in the precision of the lines the lasers revealed, their threadlike quality: Some lines were just 0.1 millimeters wide, the thickness of a standard piece of paper. The mummies belong to a pre-Columbian culture known as the Chancay, whose celebrated tapestries and pottery featured designs similar to those inscribed on the mummy skin. But the tattoos were far more intricate, suggesting great skill and a special emphasis on tattooing as an artform in Chancay culture.
“This level of intricacy in the tattoos [suggests] that they were a focus in the society’s aesthetics,” says Pittman. The tattoos may have been a marker of status, as only some of the mummies had them, but their meaning remains uncertain. Pittman and Bak published their findings in the Proceedings of the National Academy of Sciences.
“Tattooing is very widespread in South America both today and in pre-colonial contexts,” says José Oliver, an expert in Latin American archaeology at University College London. It serves many functions: to showcase identity, ethnic affiliation, or social status, or as a ritual for the “protection of the person or body,” he says. They can also serve to mark differences in age or gender.
Under the laser’s beam, geometric patterns and animal shapes popped from the mummified skin.
All tattoos fade and flatten over time, which blurs the designs, but the laser imaging revealed the artwork as it would have appeared when freshly applied. “What we were able to do is image a bit deeper into the skin, where you can bypass the ‘bleed’ from tattoos,” says Pittman. For comparison, the width of the lines revealed by the lasers were three times as fine as what is usually applied today by a #12 needle, a staple in tattoo shops, colloquially referred to as the “standard” needle.
Painting on skin with this level of intricacy requires enormous effort. Because of the level of detail, the authors of the study believe that the artists used needle-based tattooing, rather than cutting and filling the skin with ink. They further speculate that tattoo artists likely relied on a cactus needle, or a sharpened animal bone for their artwork—although no evidence of the exact technique has been discovered yet. They believe charcoal was used for ink.
The Chancay thrived between 500 and 1,300 years ago, but their coastal state was likely absorbed by the Inca Empire. There are no known descendants today that identify as Chancay, and the mummies that Pittman studied are housed at the Archaeological Museum “Arturo Ruiz Estrada” in Huacho, Peru. They were buried alongside beautifully crafted dolls and other textile artifacts.
The oldest known tattoo belongs to Ötzi, a 5,300-year-old “Iceman,” whose body was perfectly preserved in glacier ice in the Alps. The significance of Ötzi’s tattoos has been much speculated upon, including the possibility that they were applied medicinally. As a next step, Pittman wants to use lasers on Ötzi’s tattoos.
“I’m hoping we can push the level of detail in tattoos back in time,” says Pittman. 
Lead photo courtesy of Michael Pittman
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