Tribal tattoos have been practiced for thousands of years. Modern people still get them done for many reasons such as to belong to a modern 'tribe' even if they do it on a subconscious level. Getting tattooed was also seen as a rite of passage into adulthood.
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A belief goes that if a girl can't take the pain of tattooing, she is un-marriageable, because she will never be able to deal with the pain of child birth. If a boy can't deal with the pain he is considered to be a bad risk as a warrior, and could become isolated from the tribe.