why these humans mutilate themselves?

WorldScience | 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.

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.