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December 03, 2009

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Tattoos, piercings may advertise good health

Dec. 3, 2009
Special to World Science  

Tat­toos and body pierc­ings—com­mon world­wide since an­cient times—may ex­ist be­cause they ef­fec­tively ad­ver­tise ro­bust health and good genes to po­ten­tial mates, a study pro­poses.

Bi­ol­o­gists the­o­rize that many risky, costly and ap­par­ently use­less be­hav­iors per­sist am­ong ani­mals be­cause of what they com­mu­ni­cate to po­ten­tial mates, ri­vals and oth­ers. For ex­am­ple, an ex­pen­sive Rolex watch may be no more use­ful or pret­ti­er than a Timex, but for some peo­ple it serves a func­tion by cre­at­ing an au­ra of wealth. 

Tat­toos and body pierc­ings—com­mon world­wide since an­cient times—may per­sist be­cause they ef­fec­tively ad­ver­tise ro­bust health and good genes to po­ten­tial mates, a study pro­poses. (Im­age cour­tesy CDC)
A field of ev­o­lu­tion­ary bi­ol­o­gy called sig­nal­ing the­o­ry ex­am­ines such be­hav­iors.

“Hon­est sig­nals” are de­fined as sig­nals that are hard to fake and thus make bet­ter ad­ver­tisements. For in­stance, the Rolex may not show true fi­nan­cial sol­id­ity; you might have just over­drawn your cred­it card or be run­ning a Ponzi scheme. 

On the oth­er hand, if you stick a met­al pin through your cheek with­out suf­fer­ing any ill ef­fects, that may ac­tu­ally say some­thing about your im­mune sys­tem, es­pe­cially if dis­in­fec­tion has­n’t been in­vented yet. Thus, it could be an hon­est sig­nal of health, if per­haps not of the sharpest mind.

Sla­womir Koziel of the Pol­ish Acad­e­my of Sci­ences’ In­sti­tute of An­thro­po­l­ogy in Wro­claw, Po­land, and col­leagues de­cid­ed to ex­plore wheth­er body-de­cor­ated peo­ple ac­tu­ally do have bet­ter health than aver­age. 

They meas­ured lev­els of bodily sym­me­try in 200 peo­ple with and with­out tat­tooes and un­con­ven­tion­al pierc­ings. Many sci­en­tists con­sid­er such sym­me­try as an in­di­ca­tor of healthy de­vel­op­ment.

Sym­me­try was sig­nif­i­cantly high­er in the tat­tooed-and-pierced group, es­pe­cially in men, the re­search­ers found.

“High­er body sym­me­try of the men hav­ing tat­toos or pierc­ing in­di­cates that this type of body de­cora­t­ion in the West­ern so­ci­e­ty can be re­lat­ed to the hon­est sig­nal of bi­o­log­i­cal qual­ity only for men,” Koziel and col­leagues wrote, de­scrib­ing their find­ings in a pa­per slat­ed for pub­lica­t­ion in the re­search jour­nal Ev­o­lu­tion and Hu­man Be­hav­ior.

“Both tat­toos and pierc­ings can pre­s­ent health risks,” such as due to blood-borne dis­eases, they not­ed, and it’s the abil­ity to take such risks suc­cess­fully that of­fers the bi­o­log­i­cal sig­nal.

It has­n’t been clear to date why tat­tooes and pierc­ings are done, the re­search­ers said. Such de­cora­t­ions can mark mem­ber­ship in a group of some sort, yet of­ten only some group mem­bers opt for these badges of mem­ber­ship. One pos­si­ble ex­plana­t­ion was that peo­ple get tat­tooes and pierc­ings in or­der to dis­tract from some phys­i­cal short­com­ing, but the study re­sults seemed to con­tra­dict this view, Koziel and col­leagues re­marked.

They al­so found that among males in their stu­dy, the most com­mon tat­too loca­t­ions were arms and legs, where­as in fe­males it was back and stom­ach. Pierc­ing were most of­ten on the face (76 per­cent) of males and on the ab­do­men (46 per­cent) of fe­males.

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Tattoos and body piercings—common worldwide since ancient times—may persist because they effectively advertise robust health and good genes to potential mates, a study proposes. Biologists theorize that many risky, costly and apparently useless behaviors exist because of what they communicate to potential mates, rivals and others. For example, an expensive Rolex watch may be no more useful or prettier than a Timex, but for some people it serves a function by creating an aura of wealth. A field of evolutionary biology called signaling theory examines such behaviors. “Honest signals” are defined as signals that are hard to fake and thus make better advertisements. For instance, the Rolex may not show true financial solidity; you might have just overdrawn your credit card or be running a Ponzi scheme. On the other hand, if you stick a metal pin through your cheek without suffering any ill effects, that may actually say something about your immune system, especially if disinfection hasn’t been invented yet. Thus, it could be an honest signal of health, if perhaps not of the sharpest mind. Slawomir Koziel of the Polish Academy of Sciences’ Institute of Anthropology in Wroclaw, Poland, and colleagues decided to examine whether tattooed people actually do have better health than others. They measured levels of bodily symmetry in 200 people with and without tattooes and unconventional piercings. Many scientists consider such symmetry as an indicator of healthy development. Symmetry was significantly higher in the tattooed-and-pierced group, especially in men, they found. “Higher body symmetry of the men having tattoo or piercing indicates that this type of body decoration in the western society can be related to the honest signal of biological quality only for men,” Koziel and colleagues wrote, describing their findings in a paper slated for publication in the research journal Evolution and Human Behavior. “Both tattoos and piercings can present health risks,” such as due to blood-borne diseases, they noted, and it’s the ability to take such risks successfully that offers the biological signal. It hasn’t been clear to date why tattooes and piercings are so common, the researchers noted. Such decorations can mark membership in a group of some sort, yet often only some people in the group opt to get these badges of membership. One possible explanation was that people get tattooes and piercings in order to distract from some physical shortcoming, but the study results seemed to contradict this view, Koziel and colleagues remarked. They also found that among males in their study, the most common tattoo locations were arms and legs, whereas in females it was back and stomach. Piercing were most often placed on the face (76%) of males and on the abdomen (45.8%) of females.