Tattooing has been a Eurasian practice at least since Neolithic times. Otzi the Iceman, dating from the fourth to fifth millennium BC, was found in the Otz valley in the Alps and had some 57 carbon tattoos consisting of simple dots and lines on his lower spine, behind his left knee, and on his right ankle. These tattoos were thought to be a form of healing because of their placement which resembles acupuncture. Other mummies bearing tattoos and dating from the end of the second millennium BC have been discovered, such as the Mummy of Amunet from ancient Egypt and the mummies at Pazyryk on the Ukok Plateau.
Pre-Christian Germanic, Celtic and other central and northern European tribes were often heavily tattooed, according to surviving accounts. The Picts were famously tattooed (or scarified) with elaborate, war-inspired black or dark blue woad (or possibly copper for the blue tone) designs. Julius Caesar described these tattoos in Book V of his Gallic Wars (54 BC). Various other cultures have had their own tattoo traditions, ranging from rubbing cuts and other wounds with ashes, to hand-pricking the skin to insert dyes.
Tattooing in the Western world today has its origins in the maritime expeditions, through the contact with amerindian tribes and Polynesia, by sixteenth - eighteenth century explorers. Especially the Polynesian practice became popular among European sailors, from them they took the Samoan word "tatau", to describe the actual tattoo. As sailors traveled abroad and returned home with tattoos inscribed on their bodies, they began to appear in mainstream European, and eventually North American, figurations.
People have also been forcibly tattooed. A well-known example is the identification system for inmates in Nazi concentration camps during the Holocaust. Tattoos have also been used for identification in other ways. For example, during the Roman Empire, Roman soldiers were required by law to have identifying tattoos on their hands in order to make it difficult to hide if they deserted. Gladiators and slaves were likewise tattooed, exported slaves were tattooed with the words "tax paid" and it was a common practice to tattoo "Stop me, I'm a runaway" on their foreheads. Emperor Constantine I banned tattooing the face around AD 330 and the Second Council of Nicaea banned all body markings as a pagan practice in AD 787.
Tattoos are forbidden in Judaism based on the Torah (Leviticus 19:28): "You shall not make gashes in your flesh for the dead, or incise any marks on yourselves: I am the Lord." The prohibition is explained by contemporary rabbis as part of a general prohibition on body modification (with the obvious exception of ritual circumcision) that does not serve a medical purpose (such as to correct a deformity). Maimonides, a leading 12th century scholar of Jewish law and thought, explains the prohibition against tattoos as a Jewish response to paganism. In modern times, the association of tattoos with Nazi concentration camps and the Holocaust has given an additional level for revulsion to the practice of tattooing, even among many otherwise fairly secular Jews. It is a common misconception that anyone bearing a tattoo is not permitted to be buried in a Jewish cemetery.
Tattooing involves the placement of pigment into the skin's dermis, the layer of dermal tissue underlying the epidermis. After initial injection, pigment is dispersed throughout a homogenized damaged layer down through the epidermis and upper dermis, in both of which the presence of foreign material activates the immune system's phagocytes to engulf the pigment particles. As healing proceeds, the damaged epidermis flakes away (eliminating surface pigment) while deeper in the skin granulation tissue forms, which is later converted to connective tissue by collagen growth. This mends the upper dermis, where pigment remains trapped within fibroblasts, ultimately concentrating in a layer just below the dermis/epidermis boundary. Its presence there is stable, but in the long term (decades) the pigment tends to migrate deeper into the dermis, accounting for the degraded detail of old tattoos.
