Oetzi the Iceman, who was attacked one late spring or early summer around 3500 BCE and whose belongings and naturally mummified 5,300 year old body were found in a glacier in the Alps in 1991, was tattooed. His are amongst the oldest documented tattoos in the world, and the earliest direct evidence that tattooing was practiced in Europe by at least the Chalcolithic period. His skin naturally darkened from prolonged exposure to sub-zero temperatures, and some of his tattoos became faint or invisible to the naked eye. Previous studies have identified between 47 and 60 markings.
     Marco Samadelli, a scientist at the EURAC-Institute for Mummies and the Iceman, has developed a process to take multi-spectral photographs from different angles in wavelengths from infrared to ultraviolet, allowing tattoos which are no longer recognisable to the human eye to be seen with great precision. Researchers there have now revealed all of Oetzi's tattoos, including previously unknown marks on his lower right ribcage, bringing the total number to 61.
     The markings consist of 19 groups of lines from 1 to 3 millimetres in width and 7 to 40 millimetres in length, mostly arranged in groups of two, three or four parallel lines, plus two crosses. With the exception of the perpendicular crosses on the right knee and left ankle, and parallel lines around the left wrist, the lines all run parallel to one another and to the longitudinal axis of the body. The greatest concentration is on his legs, which together bear 12 groups of lines.
     The newly discovered marks consist of four parallel lines between 20 and 25 millimetres long, are the first detected on the front of his torso, and have reopened a debate about the role of tattoos in prehistoric times. They are striking because other markings are mostly on his lower back and legs, between the knee and the foot.
     In his 2012 book 'Spiritual Skin: Magical Tattoos and Scarification', anthropologist Dr Lars Krutak documents an experiment which determined that tattoos applied to acupuncture points using a bone needle "could produce a sustained therapeutic effect". While the lines may have held symbolic meaning, 80 percent correspond to classic Chinese acupuncture points used to treat rheumatism, while others are located along meridians used to treat other ailments from which Oetzi also suffered.

Edited from Discovery News (27 January 2015),  PhysOrg (28 January 2015)