Researchers have mapped all 61 tattoos of Ötzi, the 5,300-year-old glacier mummy discovered by hikers in the Ötztal Alps near the Italian-Austrian border in 1991.

Previous studies have already detected fifty or so tattoos, but because they’re difficult to spot—since his skin has darkened over time—researchers haven’t agreed on the final count. Now, an Italian team led by Marco Samadelli of EURAC Research has turned to a non-invasive imaging technique, borrowed from the art world, that can capture light at different wavelengths, ranging from infrared to the ultraviolet. Their technique revealed never-before-seen tattoos.

The 45-year-old male’s 61 tattoos, some of the world’s most ancient examples, take on the form of crosses (or plus signs) and groupings of parallel lines that look like tallies of two to four. They’re all black, and some were as long as four centimeters. Unlike modern tattooing methods that use needles, these were made by rubbing charcoal into fine incisions.

The tattoos were divided into 19 groups across his body, including groups of lines to the left and right of the spinal column, the left calf, the right instep, on the inner and outer ankle joint, and on the chest at the height of the lowermost right rib. (This last one is the newest one discovered.) Two lines lie across his left wrist, and a cross appears on the back of his right knee and next to the left Achilles tendon.

Furthermore, many of his tattoos are located on parts (such as the lower back and joints) that may have caused him pain due to degeneration or disease—suggesting how the tattoos may have been therapeutic, and not symbolic.

“Many people think that it was a kind of treatment because most of the tattoos are very close to areas where he probably suffered from pain," study co-author Albert Zink of EURAC Research tells Live Science. And many of these inked spots even seem to correspond to skin acupuncture lines, the consequence of a form of healing that originated in Asia thousands of years after Ötzi’s time.

A few years ago, researchers sequenced Ötzi’s genome and found that he had O-type blood and was lactose intolerant. Then, last summer, a team analyzing the non-human sequences on the remains found evidence of an oral pathogen involved in gum disease. Additionally, his arteries were hardened, he had healed rib fractures, a cyst-like growth on his toe, and based on his fingernails, his immune system had been subjected to multiple attacks of severe stress. He’s believed to have died from an arrowhead wound in his left shoulder.

Ötzi is housed at the South Tyrol Museum of Archaeology in Italy. The findings were published in Journal of Cultural Heritage last week.

Images: South Tyrol Museum of Archaeology/Eurac/Samadelli/Staschitz (top), South Tyrol Museum of Archaeology (middle), EURAC/M.Samadelli/M.Melis (bottom)