Why do some people get tattooed whereas others don’t? Is it due to variations of their genes?
Researchers from the University of Southern Denmark in Odense not too long ago addressed these questions. Their findings, reported in February within the journal Behavior Genetics, confirmed that variations in a person’s propensity to get tattooed have been not resulting from nature however due to nurture.
‘Nature’ right here refers to an intrinsic, genetically-determined predisposition that impacts one’s behaviour. ‘Nurture’ denotes extrinsic components resembling one’s schooling, tradition, household, and friends.
A tattoo is an indelible design registered on the pores and skin by injecting inks and dyes right into a pores and skin layer referred to as the dermis. There, the pigment particles turn into engulfed and subsequently saved in place by cells of the physique’s immune system, making them everlasting.
In 1991, hikers came across the naturally mummified stays of a person since named Ötzi the Iceman in northern Italy. Scientists discovered that he lived greater than 5,000 years in the past and had tattoos. Today, many sports activities and leisure celebrities additionally sport tattoos — as do their followers, and certainly anybody who needs to bear symbols they contemplate necessary or important to themselves on their particular person.
Since including any overseas substance to 1’s physique is a well being danger from a medical viewpoint, finding out the long-term results of tattooing on public well being has been an necessary analysis focus.
Sorting nature from nurture
If two offspring are born from the identical being pregnant, they’re referred to as twins. The offspring may be genetically equivalent or non-identical. Identical twins share all of their genes whereas non-identical twins share on common solely 50% of their genes.
After the daddy’s sperm fertilises the mom’s egg, the unified cell that’s shaped is known as the zygote. The zygote then develops into an embryo that in flip grows into the infant.
Sometimes two sperm can concurrently fertilise two eggs to provide two zygotes, and the zygotes can go on to kind non-identical twins. On the opposite hand, equivalent twins are shaped when an embryo from a single zygote splits at an early stage to turn into two embryos, and every then grows to turn into a child.
For this purpose, equivalent twins are also called monozygotic twins and non-identical twins are referred to as dizygotic twins. Monozygotic twins are all the time of the identical organic intercourse, whereas dizygotic twins — like some other pair of siblings — may be both of the identical or of various sexes.
If each members of a twin pair sport a tattoo, they’re additional stated to be concordant. They are additionally concordant if each don’t. But if one twin has a tattoo and the opposite doesn’t, they’re stated to be discordant.
The researchers behind the brand new study have been curious as as to if there was a ‘greater’ concordance at work in monozygotic twins than in dizygotic twins of the identical intercourse. Their search got here up empty, i.e. there was no larger concordance, even although monozygotic twins share twice as many genes as dizygotic ones.
The discovering instructed that genetic variations have little, if something, to do with a person eager to get tattooed.
Additional findings
The Danish Twin Register (DTR) is a database with particulars of greater than 175,000 twins born between 1870 and 2009. The researchers mailed out a questionnaire to twins recorded within the DTR. They obtained responses from 4,790 people, together with from each twins of 1,327 twin pairs.
Of these respondents, 1,058 (22%) have been monozygotic, 3,501 (73%) have been dizygotic, and the zygosity was unknown for 231 (4.8%). The researchers sorted the twins into three cohorts based mostly on their start years: oldest (1925-1960), center (1961-1980), and youngest (1981-2004).
Finally, the researchers requested the respondents if their co-twin additionally had a tattoo, in regards to the tattoos’ colors and sizes, and the age at which they have been first tattooed. The responses revealed that 22% had at the very least one tattoo. In the 1,327 pairs for which each twins responded, the self-reported tattoo standing matched the knowledge supplied by the co-twin in 98.5% of the circumstances.
The researchers reported a marked improve from the oldest to the youngest cohorts, from beneath 6% to above 30%, by way of the propensity for getting a tattoo. Evidently tattooing has turn into more and more in style in latest occasions.
The researchers additionally requested the respondents about their way of life components resembling schooling, smoking, quantity of bodily train, and alcohol consumption. They might correlate tattooing strongly solely with smoking. But additionally they acknowledged limitations of their potential to correlate with alcohol consumption and train “because the age at first tattoo and age at which the questionnaire was answered may vary up to several decades”.
More concordance for some defects
In 2021, researchers from the Seoul National University College of Medicine in South Korea reported within the journal BJOG the concordance charges for a number of totally different start defects present in 3,386 monozygotic and dizygotic twin pairs born between 2001 and 2019.
Birth defects affecting the nervous system, the circulatory system, cleft lip/palate, and the urinary system have been discovered to be considerably extra concordant in monozygotic than in dizygotic twins. The implication was that aberrant organic growth in these techniques is primarily resulting from one’s genes.
On the opposite hand, the concordance charges did not considerably differ for malformations of the attention, ear, face or neck, the genital organs, and the musculoskeletal system, that means that for these problems, extrinsic features of the uterine setting, resembling maternal diet, physiology, smoking, and infections, performed a extra important position.
The researchers ended their paper writing: “we have shown empirically that tattooing … is a cultural phenomenon with little to no evidence for genetic influences.”
D.P. Kasbekar is a retired scientist.
Published – March 24, 2025 05:30 am IST
