Why are people getting tattoos? According to twin studies, it is nurture rather than nature.

• Researchers from the University of Southern Denmark found that differences in tattooing propensity are not due to nature but to nurture.

• Nature refers to an intrinsic, genetically-determined predisposition, while nurture includes extrinsic factors like education, culture, family, and peers.

Tattoos and Their Historical Significance

• Tattoos, an indelible design registered on the skin, are permanent and are engulfed by the body’s immune system cells.

• Ötzi the Iceman, a man who lived over 5,000 years ago, had tattoos.

• Today, many celebrities, fans, and anyone who wishes to bear significant symbols on their person also sport tattoos.

Sorting Nature from Nurture

• Twins, born from the same pregnancy, can be genetically identical or non-identical.

• Identical twins share all of their genes, while non-identical twins share on average only 50% of their genes.

• If both members of a twin pair sport a tattoo, they are concordant.

• If one twin has a tattoo and the other doesn’t, they are discordant.

Additional Findings

• A Danish Twin Register questionnaire revealed that 22% of twins had at least one tattoo.

• The propensity for getting a tattoo increased from the oldest to the youngest cohorts.

• Lifestyle factors such as education, smoking, physical exercise, and alcohol consumption were found to strongly correlate tattooing with smoking.

More Concordance for Birth Defects

• Birth defects affecting the nervous system, circulatory system, cleft lip/palate, and urinary system were found to be more concordant in monozygotic twins than in dizygotic twins.

• For malformations of the eye, ear, face or neck, the genital organs, and the musculoskeletal system, extrinsic aspects of the uterine environment played a more significant role.