RESEARCH ARTICLE Shirts or Skins?: Tattoos as Costly Honest Signals of Fitness and Affiliation among US Intercollegiate Athletes and Other Undergraduates Christopher D. Lynn 1 & Taylor Puckett 1 & Amanda Guitar 1 & Nicholas Roy 1 # Springer Nature Switzerland AG 2018 Abstract Body art that lesions the skin can result in infection, making tattoos and piercings inherently risky forms of expression. Evolutionary theorists have posited two complementary hypotheses for the popularity of tattooing and piercing in the face of less dangerous options. The Bhuman canvas hypothesis^ suggests that tattooing and piercing may be hard-to-fake conscious or unconscious advertisements of fitness or affiliations. The Bupping the ante hypothesis^ proposes that tattooing and piercing are costly honest signals of good genes in that they injure the body to show how well it heals. We sampled two student populations in the USA to test three related predictions: (1) intercollegiate athletes would be tattooed and pierced at higher rates than other undergraduates to signal fitness, (2) athletes would be more likely to get college- or pro sports-related tattoos than other students, and (3) tattooed or pierced intercollegiate athletes would have lower rates of tattoo- and piercing-related medical complications. We used chi-square and separate logistic regressions of athlete status on tattooing, piercing, and related complications. Study 1 (n = 524) did not find support for predictions but included only a small number of athletes with body modifications. Study 2 (n = 6004) found no main effect for athletes but did find an interaction effect for athletes-by-gender (p = .005). Athletes were also more likely to have college- and pro sports-related tattoos, and football players and male swimmers/divers were more likely to be tattooed in general than other undergraduates (p < .05). Finally, we found positive relationships between tattooing/BMI and BMI/ tattooing complications (p < .01), supporting a costly honest signaling function irrespective of athlete status. Both hypotheses were falsified for piercing. Our findings support tattooing as a fitness and affiliation signal that is highly context-dependent. Keywords Tattooing . Piercing . Costly honest signaling . Intercollegiate athletes . Undergraduates . BMI Introduction Tattooing and piercing are interesting forms of body decoration because they simultaneously draw attention to the body and injure it. Body decoration is ubiquitous in humans and appears among other organisms as well (Kohler 1925; MacKinnon 1978), which suggests body décor represents a phenotypic gambit (Lynn and Medeiros 2017), or behavior with underlying adaptive functions (Grafen 1991). The many uses and meanings of tattooing and piercing suggest social selection pressures may be operating to maintain their continued practice. Social selection is a type of natural selection that accounts for dynam- ics of cooperation that maximize reproductive fitness (Roughgarden 2009). As hypothesized for hunting (Hawkes and Bliege Bird 2002), tattooing and piercing may have been used to demonstrate social prestige and maximize fitness (Carmen et al. 2012; Koziel et al. 2010; Lynn and Medeiros 2017; Wohlrab et al. 2009a). We examine tattooing and piercing in a prestigious class of people in a contemporary US setting. By comparing tattooing and piercing in elite athletes to similar non-athletes, we may be able to determine if, indeed, such body modifications help more fit individuals show off their pheno- types and affiliations. Cultural tattooing and piercing practices go back thousands of years as indicated by these body modifications found on ancient mummies; jewelry and implements found at ancient sites; and sculptures, paintings, and other artifacts that attest to their antiq- uity (DeMello 2000, 2007; Deter-Wolf et al. 2016; Gilbert 2000). Anthropologists have long speculated that tattooing arose as an * Christopher D. Lynn cdlynn@ua.edu 1 Department of Anthropology, University of Alabama, Box 870210, Tuscaloosa, AL 35487, USA Evolutionary Psychological Science https://doi.org/10.1007/s40806-018-0174-4