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 successive generations of macrophages, 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.
Ancient tattooing traditions have also been documented among Papuans and Melanesians, with their use of distinctive obsidian skin piercers. Some archeological sites with these implements are associated with the Austronesian migration into Papua New Guinea and Melanesia. But other sites are older than the Austronesian expansion, being dated to around 1650 to 2000 BCE, suggesting that there was a preexisting tattooing tradition in the region.
In the Maori culture of New Zealand, the head was considered the most important part of the body, with the face embellished by incredibly elaborate tattoos or ‘moko,’ which were regarded as marks of high status. Each tattoo design was unique to that individual and since it conveyed specific information about their status, rank, ancestry and abilities, it has accurately been described as a form of id card or passport, a kind of aesthetic bar code for the face. After sharp bone chisels were used to cut the designs into the skin, a soot-based pigment would be tapped into the open wounds, which then healed over to seal in the design. With the tattoos of warriors given at various stages in their lives as a kind of rite of passage, the decorations were regarded as enhancing their features and making them more attractive to the opposite sex.