Tattooing Primes the Immune System

Watching a Jerry Coyne video seemed to influence enhanced evolution knowledge but also increased misconceptions relative to a Baba Brinkman video (Lynn, Friel, Evans, & Brinkman 2015).

…But First, a Test of the “Rap Guide to Evolution”…

A few weeks ago I presented a poster at the Human Biology Association annual scientific meeting about the roles of emotions in learning about evolution via a performance of Baba Brinkman’s “Rap Guide to Evolution.” We found that emotions matter, but the kind of emotions influence WHAT you learn. We looked at skin conductance as a proxy of emotional salience & compared it to the differences between pre- & posttests on the Evolutionary Attitudes & Literacy Survey (EALS) & compared those to the comments of the participants.

What we found is that if you’re a white intellectual who is already inclined favorably toward evolution, your knowledge & attitudes seem to be positively influenced. (Actually, we didn’t control for white intellectualism, but that’s my demographic suspicion.) To participants not already biased toward evolution, Baba seems to come off as unfairly snarky about religion & that’s what they tend to remember.

This is, in retrospect, not rocket science, but then I’m not a rocket scientist. For some reason (read: from my superficial listening to some audiobooks by Antonio Damasio), I thought emotions might have a more generalized salience in improving knowledge & acceptance. Like going to a horror movie to scare yourself actually can influence liking the person you’re with because the boundary between the meaning of the feeling you have slips or is indistinct. If you’re interested, here is a link to our poster, & we will be writing up these data more systematically as we continue to poke at them.

Tattooing outside in a vacant lot in Guayaquil, Ecuador, January 2002 (Photo by author, all rights reserved).

Tattoos as Costly Honest Signaling

However, I was actually more excited at the time about the presentation on our Ink and Immunity Study of one of my master’s students, Johnna Dominguez. Several years ago, I hypothesized that tattooing should signal gene quality by providing an opportunity for people to see visible healing. The idea is that, much like the coloring of bird feathers is believed to signal resistance to parasites (though not empirically demonstrated, as far as I can tell—e.g., as this study of Steller’s jays by Zirpoli et al suggests), a well-done tattoo that is vibrant, heals quickly, & maintains form or color tells me that you have a good immune system.

If you’ve ever gotten a big tattoo, you know they can knock the piss out of you. I have a decent-sized back piece that took 12ish hours over two sittings. One of those sittings lasted 9 hours because I had driven from NY to GA to get it done & wasn’t going to be getting back down South anytime soon. Another one by the same tattooist took over 5 hours to get the outlining & shading of a half-sleeve (still unfinished 15 years later—see why it’s sometimes worth doing a 9-hour sit?). In both cases, I felt like I’d fallen off a moving motorcycle & skidded down the concrete on the respective body part. For days after, I felt rundown afterward, like recovering from a flu or other nasty respiratory virus. In my case, the tats healed up & have been emblematic of my otherwise good health, still bright & shiny after many years. Others I have seen ooze & scab & show patchy signs of having been infected. The sanitation of the tattooist is certainly an issue, as is her or his skill with the tattoo gun. But some people hold ink & heal better than others, according to tattoo lore.

Johnna Dominguez presenting her talk on tattooing & SIgA at the Human Biology Association meeting, St. Louis, MO, March 26, 2015 (Photo by author).

Yet very little has been written about tattooing as a signal of health. Most of the research conducted links tattooing to dermatological problems, skin cancer, lesions, & risk factors merely correlated with the ‘type’ of person who would get a tattoo. (I did a big review/theory paper on this that I’ve been sending around for a while seeking a good home, which is in revise & resubmit or I’d share it—email if you’re interested in reading—one reader called it the “Rosetta Stone of tattoo background.”) So there’s a lot of data about tattoo & associations with drug & alcohol use, promiscuity, teen pregnancy, etc. Of course, those factors are not inconsequential. It is probably true that many people who are heavily tattooed are also more likely to enjoy lifestyles that are otherwise beyond the ken of mainstream models (realistic or not) of chastity & moderation.

Several studies out of Europe a few years ago (notably, the dissertation of Silke Wohlrab,which was published as a series of journal articles but can be read in its entirety here) found that, indeed, despite the increasingly mainstream nature of tattooing in Euroamerica, most males AND females still perceive tattooed females as more likely to engage in promiscuous sex or be drinkers. On the other hand, most males AND females perceived tattooed males as more attractive. Interesting, right? Another study from Poland found an association between tattooing & fluctuating asymmetry (FA) but NOT between piercing & FA. FA refers to deviations from bilateral symmetry, which many studies have found to be associated with attractiveness. We have many small deviations from absolute symmetry across our bodies, which seem to be related to our immunological resistance to developmental insults. So, back to the pathogens & feathers. Good looking tattoos may signal health.

Testing the Inoculation Hypothesis

So, we tested that. Johnna was also interested in retesting this idea that tattooed men are still viewed as more attractive & females as more promiscuous, since the aforementioned Wohlrab study was conducted in Germany, while we are in the U.S. Deep South. Instead of the questionnaire & WEIRD psych lab approach used in the Euro studies, Johnna went out & sat in hair salons & tattoo studios, talking to women & developing cultural consensus models of attraction relating to tattooing. A few things emerged that I won’t go into a tremendous amount of detail about here because she’s still hammering away at her interpretations, but what became clear is that (1) cultural attitudes have shifted but (2) they haven’t shifted that much yet. Variables that matter when determining attractiveness, which are obvious but must be considered: (a) tattoo location on the body, (b) tattoo content, (c) attitudes of the tattooed, & (d) attitudes of the tattooeds’ friends and family. These attitudes make a difference in self-esteem but didn’t seem to be related to generalized perceived stress or the immunological response to getting tattooed, but there is certainly more there to explore.

A taster from this tattoo study, showing that greater tattoo experience is associated with a smaller decrease in SIgA. The difference is significant with an effect size that knocked me out of my chair.

However, Johnna also collected saliva samples before & after the tattooing sessions & quantified the number of tattoo sittings, hours tattooed, & number of tattoos people had. She compared salivary immunoglobulin A (SIgA) to these indices of lifetime tattoo experience & found a robust effect. IgA is a metabolically expensive, highly conserved frontline defense against gastrointestinal & respiratory infections. Because it is produced continually, somatic energy depletions should result in drops in IgA production. We predicted that the immune systems of people with more tattoo experience would have adjusted over time, allostatically, & be less negatively effected—that it would provide an inoculation-like effect. And that is exactly what we found.

We reason that people who don’t heal up well after tattooing aren’t likely to get a lot of tattoos, so tattoo experience should be a good signal of something like that. That warrants testing, of course, & we also collected handgrip strength & FA measures to compare vis-a-vis these quality-signaling hypotheses but have not analyzed those data yet.

In the Q&A at HBA, Ines Varela-Silva pointed out that we should replicate the study in Latin America, where tattoo infections happen much more often due to poor tattoo hygiene. That caused me to recall the time I saw tattooing in a vacant lot on a street corner in Guayaquil, Ecuador. The tattooist was getting power from a long extension cord run into a neighboring business, & there was a long line of people waiting to be tattooed. I should have been rather horrified, but I must admit I’ve been tattooed several times under similar circumstances. Perhaps I wasn’t outside in the elements, but there was nothing legal, sanitary, or sober about the tattoo parties I went to when I was young.

I remember one in Bloomington, IN, when a squatter-punk friend of mine had organized a party. He invited a tattoo artist from South Bend, IN to come down to Bloomington & tattoo a bunch of folks over the course of a night. For giving her so much business, he got a free tattoo. The artist was an older woman who arrived in an RV with her husband & son. About an hour or two into the evening, before I’d got my tattoo, the party was raided by cops because one underage kid who the artist refused to tattoo without permission tried to get his older brother to pose as his parent. His brother called the police instead. The police had us all line up, present our IDs, &, for those of us not legal to drink, breath in his face (I was 20 at the time). Somehow he couldn’t tell I’d just drunk a 40 ozer. We moved the party out of town to place in the boonies I’d barely be able to drive back from, continued our revelry, & finished our tattooing. I healed up but later needed that tattoo touched up when the outlining faded…

Barry Bogin asked a question about the height (I think) of Johnna’s participants, which puzzled us all. He was referencing a paper by Charles Super & Beatrice Whiting about height variation in tattooing & painful rituals practice. There’s some other signaling studies out there that I’ve run across & written about in previous posts or that mysterious review paper I reference above, but the Super/Whiting one doesn’t ring a bell. We’re trying to track it down & may have to shoot Barry an email, but if it anyone knows it, drop us a comment below.

And if you wanna know more about this tattoo study, Johnna is wrapping up her thesis now & would likely be happy to share more info. Contact me if you want to get in touch with her or know more about our future plans with this project.