<P> Tattoos have also been used for identification in other ways . As early as the Zhou, Chinese authorities would employ facial tattoos as a punishment for certain crimes or to mark prisoners or slaves . During the Roman Empire, Roman soldiers were required by law to have identifying tattoos on their hands in order to make desertion difficult . 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 . Owing to the Biblical strictures against the practice, 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 . </P> <P> In the period of early contact between the Māori and Europeans, the Maori people hunted and decapitated each other for their moko tattoos, which they traded for European items including axes and firearms . Moko tattoos were facial designs worn to indicate lineage, social position, and status within the tribe . The tattoo art was a sacred marker of identity among the Maori and also referred to as a vehicle for storing one's tapu, or spiritual being, in the afterlife . </P> <P> Tattoos are sometimes used by forensic pathologists to help them identify burned, putrefied, or mutilated bodies . As tattoo pigment lies encapsulated deep in the skin, tattoos are not easily destroyed even when the skin is burned . </P> <P> Tattoos are also placed on animals, though rarely for decorative reasons . Pets, show animals, thoroughbred horses, and livestock are sometimes tattooed with identification and other marks . Tattooing with a' slap mark' on the shoulder or on the ear is the standard identification method in commercial pig farming . Branding is used for similar reasons and is often performed without anesthesia, but is different from tattooing as no ink or dye is inserted during the process, the mark instead being caused by permanent scarring of the skin . Pet dogs and cats are sometimes tattooed with a serial number (usually in the ear, or on the inner thigh) via which their owners can be identified . However, the use of a microchip has become an increasingly popular choice and since 2016 is a legal requirement for all 8.5 million pet dogs in the UK . </P>

Where did the idea of tattoos come from