…but lean a little bit closer, see, roses really smell like…stinky tee-shirts?
Biology is complicated, but most experimental design isn’t. Thanks to the t-test and its descendants, we scientists end up telling a lot of binary “less vs. more” stories and it ends up being hard to tell what really matters in the grand scheme of stuff. (Flu from animals? Hate on food from animals.)
So I was delighted this weekend when one of my favorite “less vs. more” laboratory results—interesting but of questionable relative importance—turned out to be substantiated by surveys of the larger human population, and was therefore applicable to my everyday life of not eating meat, waiting for football season, and judging things by how they smell.
The major histocompatibility complex (“It’s just major right here, y’all know what I’m sayin’?”) is a region of human chromosome 6 that codes for a bunch of cell-cell recognition capabilities involved in reproduction and immunity (finding cells that your cells like, or don’t like, and responding accordingly). I’ve long been a fan of what came to be known as “The Sweaty T-Shirt Study,” which demonstrated that women prefer the smell of sweat from men whose MHC regions are least similar to theirs, the implication being that the resultant offspring from such a scent-match would have the most “go-getta” immune systems. To me, the study approach—”Here, smell.”—seemed kind of anachronistic, but the conclusions were revolutionary enough to start a whole field of sniff-and-tell research. Scientists later showed that there was no significant preference (p>0.05 = T-Pain) for the smell of outcast-MHCs among women using hormonal birth control; they preferred the smell of men with the most similar MHC.
I love these studies for their place in science history. (“It was right under our, uh, noses.”) Arguing about whether humans have the working anatomical structures for pheromone-based communication has been popular for a long time. It was only recently that we actually bothered to study the kinds of information humans subconsciously receive through the air, be it through pheromone receptors in the vomeronasal organ or just in, like, parts of the nose.
Now, I know more than one woman who actually uses the “Does he smell good and am I on birth control?” rubric to score how her relationship is going. But that’s sort of a special case; most single ladies aren’t reading scientific literature and then making dating decisions according to p-values therein. So for me, the question remained: is the the sniff-test informative, compared to, say, whether a guy can dance, or whether he’s in the running for the Heisman?
Imagine my delight to read that the speculation about mate preference from the original stinky tee-test is actually reflected in human population data (not that I’m dropping the other criteria). On Sunday, scientists reported that married couples in Brazil were more likely to have differences in the MHC region than would be expected in randomly-paired couples. Yeah, your boyfriend may smell (tee-pain), but it’s useful information.
I wonder if the utility of the stinky tee-test helps explain why women can still detect sweat when it’s masked by a number of other scents, while the same is not true for men. Whatever the mechanism, it seems my college roommate’s advice after a long game day but before a night out—”grrl, just change shirts and put some perfume on”—was exactly the right call, but only for us girls. (I guess I should expect that kind of efficiency from an engineering school…well, that and the Heisman.) The guys can’t smell us, but we can definitely smell them, and we’re judging their MHC polymorphisms along with their fancy footwork. So, guys, show us your moves and how good you smell doing them. Wait, what’s that you say? You have season tickets? Yeah, that’ll work.