Lasers help you see the hidden details of ancient drawings on the body.
It all started with a Roman pot. A new laser imaging method revealed Greek inscriptions on the pot that had been hidden, much to the surprise of archaeologists. And when
Judita Buck, a Polish archaeologist from
Krakow, read the study, she wondered what would be revealed by shining a laser on 100 mummies. These remains she is studying in coastal Peru, with some of them more than a millennium old.
Buck contacted
Michael Pittman, who developed a laser technique known as laser-stimulated fluorescence, which excites molecules on or beneath the surface of an object and allows the detection of hidden soft tissue without destroying it. He has used the technique to study details of Roman wall paintings, glass mosaics and fossils of
dinosaurs. Buck invited Pittman to come to Huacho, a beach town on Peru's central coast, a region known for having the largest number of mummy tattoos on Earth.
Buck had already identified tattoo designs on the mummies' bodies, but they were blurred under standard white light due to ink leaking and decomposition. "We hypothesized that under laser light, the skin should glow but the tattoos should not," Pittman says. "We might be able to see more because of this contrast. That was the theory."
The researchers found what they were looking for. Under the laser beam, superbly detailed geometric patterns and animal figures, mostly
birds and monkeys, emerged from the mummified skin. The real surprise lay in the precision of the lines that the laser revealed, their filamentary quality.
Some of the lines were only 0.1 millimeters wide, which is the thickness of an ordinary sheet of paper. The mummies belong to the pre-Columbian culture known as Chancay, whose famous tapestries and pottery are decorated with designs similar to those on the mummy's skin. But the tattoos were much more intricate, indicating the great skill and attention to tattooing as an art form in the Chancay culture.
"This level of sophistication of tattoos suggests that they had an important place in the aesthetics of society," Pittman says. "The tattoos may have been a status marker, as only some mummies had them, but their significance remains unclear." Pittman and Buck published their findings in the journal Proceedings of the National Academy of Sciences.
"Tattooing is very widespread in South America both today and in the pre-colonial period," says Jose Oliver, an expert in Latin American archaeology at University College London. They serve multiple functions, he says: they demonstrate identity, ethnicity or social status, and serve as a ritual to "protect the person or the body." They can also serve to mark differences in age or gender.
All tattoos fade and flatten over time, causing the pattern to blur, but laser visualization showed what the pattern would look like when freshly applied.
"We were able to image a little deeper into the skin where you can get around the 'bleeding' from tattoos," Pittman says. By comparison, the width of the lines revealed by the laser were three times thinner than what is typically applied today with a No. 12 needle, a staple in tattoo parlors, popularly referred to as a "standard" needle.
Photo: nautil.us
Drawing on skin with this level of complexity requires a tremendous amount of effort. The authors of the study believe that because of the high level of detail, the artists used needle tattooing rather than cutting and filling the skin with ink.
They also speculate that tattoo artists likely used cactus needles or sharpened animal bone for their work - although no evidence of the exact technique has yet been found. They believe charcoal was used as ink.
The Chancay flourished between 500 and 1,300 years ago, but their coastal state was likely absorbed by the
Incan Empire. Today, there are no known descendants who identify themselves as Chancay, and the mummies Pittman studied are preserved in the Museo Archaeologico Arturo Ruiz Estrada in Huacho, Peru. They were buried alongside beautifully crafted dolls and other textile artifacts.
The oldest known tattoo belongs to
Etzi, a 5,300-year-old "ice man" whose body was perfectly preserved in the ice of a glacier in the Alps. There has been much speculation about the meaning of Otzi's tattoos, including the possibility that they were applied for medical purposes.
As a next step, Pittman wants to apply lasers to
Etzi's tattoos. "
I hope that over time we will be able to increase the level of detail in the tattoos," Pittman says.