So I made it through Fire School. Here I was, a 47-year-old rookie, running around with teens and twenty-somethings, struggling to hold fire hoses on target [1], crawling on hands and knees in heavy turnout gear, my fire-resistant balaclava pulled over my face to simulate zero-visibility smoke, straining to control my breathing so I didn’t suck all the air out of my SCBA tank …
Man, was I sore on Monday. But I held my own, did better than some, and kept up with my pre-18 junior firefighter partner — a solid kid, by the way, I definitely want him there on a real call. We determined to volunteer to be the first to do everything, and damned near did.
Thanks to my joining Harmony Volunteer Fire Company a couple of weeks after last year’s Fire School, I’d been in the company for nearly a year before I had the opportunity, and so most of it turned out be a review of stuff I’d already been taught. But they had one exercise that was new to me: how to recover a runaway fire hose.
You see, at the end of an already-heavy fire hose is a metal coupling that can really hurt somebody if the hose gets loose, either from a break in a coupling, someone not following proper procedure and allowing a charged hose to turn itself on, or merely somebody taking a fall and losing control of the hose. Remember, the stream of water coming out of fire hose can be between 100 and 300 pounds per square inch — that’s a lot of specific impulse, and can make a hose end into a deadly projectile.
The safe way to wrangle a runaway hose is to straddle the hose, well upstream of the offending end, on your hands and knees, crawling as fast as you can while keeping the hose down with your hands. You dampen the erratic pendulum of the hose gradually, lessening its amplitude, and thus its potential for mayhem, finally getting hold of the coupling itself.
Only trick was, if the hose was behaving itself a little too much as we got toward the coupling, the instructor kicked it to send it moving. Thanks, dude; but I guess I did OK, all the same.
Today I thought I’d take on a scientific/ethical/moral quandary that is more complex, more like a runaway fire hose, than the many discussions you can find on the web often seem to fathom.
Was Josef Mengele a bad scientist, or merely an evil scientist?
It seems like you can’t take two steps without tripping over a gratuitous comparison of someone to Hitler. My own take, I think, is that Jon Stewart got it exactly right [2]. And as the Better Half has pointed out, comparing someone to the closest thing this world has ever seen to Sauron is tantamount to admitting you have nothing intelligent to say about them. It’s the ultimate ad-hominem attack; you don’t get many people in a generation, worldwide, whose evil is so profound and powerful that the reference isn’t, as bad as the person in question may be, a slur.
A few years back I had the opportunity, at a seminar connected with a major medical school’s graduation ceremonies, to watch a physician-turned-historian [3] give a talk on Nazi medicine that was spectacular. His argument was not the standard — that the Nazis subverted science — but that their entire belief system was, at the time, a logically justified, if undeniably evil, extrapolation of the best science of the day. His point was that science carries no moral polarity of itself; that no proper scientific knowledge is immune to being harnessed to the purposes of evil.
Eugenics — the narrow end of the wedge that led from the Nazis initially sounding, to some people anyway, as beneficent, to the practice of unapologetic mass murder — is exhibit A. Based on the evolutionary and genetic science of today, it’s a joke. Today we know it’s a fundamental misunderstanding, which failed because it didn’t account for the then-unknown phenomenon of genetic drift. The latter makes it impossible to improve or enhance the human race by weeding out the “unfit,” even if you had a morally defensible definition of that concept, as slippery as a runaway fire hose.
But scientifically, that’s hindsight. Based on the scientific understanding of the late 1930s, eugenics wasn’t a fringe belief: it was the mainstream of medical thought. And it was not uniquely Nazi or even German [4]; its leadership, arguably, hailed a generation earlier from America, where much eugenic legislation got its start, though thankfully it didn’t take hold (more about that in a moment).
Here’s the bitter pill that those of us trained to be researchers in liberal democracies have tremendous trouble swallowing: whether it is correct or incorrect, what we think we understand scientifically will not civilize people, will not necessarily help the Good Guys. And conversely, unpleasant, dangerous, and made-for-evil scientific discoveries are not, by definition, bad science. Evil, yes; not bad, in the sense of necessarily being improperly performed or producing incorrect discoveries.
Two observations along these lines. The first, though I’ve gotten to it late in the discussion, is the paper that launched me onto this topic in the first place: a treatise on the senses by Sir Kenelm Digby, and published in 1644. Amidst the archaic spellings, get a load of the following, regarding the sense of smell [5]:
“So that thofe mafters, who will teach vs that the impreffions vpon fenfe are made by fpirituall or fpiritelike thinges or qualities; which they call intentionall fpeciefes, muft labour at two workes: the one to make it appeare that there are in nature fusch thinges as they would perfuade us, the other to proue that thefe materiall actions we fpeake of are not able to performe thofe effects, for which the fenfes are giuen vnto livuing creatures. And vntill they haue done that, I conceiue we should be much too blame to admit fuch thinges, as we neyther haue ground for in reafon, nor can vnderftand what they are. And therefore, we muft refolue to reft in this beliefe, which experience breedeth in vs: that thefe bodies worke vpon our fenfes no other wayes then by a corporeall operation; and that fuch a one is fufficient for all the effects we fee proceede from them: as in the proceffe of this difcourfe we shall more amply declare.”
Get that? He’s refuting the theory that we smell things through a fairy-like transmission of qualities in favor of a corporeal contact between the object being smelled and the nose. He’s anticipating the concept of airborne chemicals constituting scent by at least a couple of centuries.
When I first read the above, it made me think of the Nazi eugenics movement — and its uncomfortable origins in science that has now been refuted, but was cutting-edge in its day — and made me want to set Digby and Mengele up as opposite ends of the spectrum: the former coming to the right conclusions despite the fact that he was using an unscientific method, the latter going so very wrong, morally at the very least, while following the scientific method, including peer review, experimental design, all nine yards. In retrospect, though, I’m going to give Digby a pass, as the standards of his day did uphold his work as scientifically valid.
We want to dismiss Mengele as an anomaly, and certainly we would be spurious to take the logical leap of blaming Nazism on genetic and evolutionary science, as some do [6]. But we can’t get off the hook that much of the laudable science of today will turn out to be just as incorrect as the eugenic beliefs of then. What matters is not whether we’re wrong or right — I can’t tell you how many PR bosses I’ve had who didn’t understand the critical fact that much of science is wrong for perfectly valid reasons — but how we apply the knowledge we think we’ve learned. And that’s not science; it’s morality.
Which brings me to eugenics in America, and one of the shimmering events that helped prevent the insidious practice from gaining a permanent (or more extended than it was, anyway) foothold here.
In 1905, both houses of my own Pennsylvania’s legislature voted in favor of a measure to force sterilization of “idiots” [7]. The state was poised, I believe, to become the first in the nation to enact a radical eugenic agenda.
Enter Governor Samuel Pennypacker, who vetoed the bill with words that continue to ring with all the right stuff a century later:
“Scientists, like all other men whose experience has been limited to one pursuit … are prone … to lose sight of broad principles outside of their domain … To admit such an operation would be to inflict cruelty upon a helpless class … which the state has undertaken to protect.”
Go, boy.
Though the legislature failed to override Pennypacker’s veto, he did not kill politically sanctioned eugenics in the U.S. — two years later, Indiana enacted a similar bill, and of course there’s the gut-wrenching, if not strictly eugenic, Tuskegee study, which shamefully didn’t end until 1972 [8]. But Pennypacker’s stand, seeing past the scientific question to the moral imperative beyond, put the eugenicists on notice that there would be resistance. And it set the stage.
Some of us, you see, know how to ride a runaway fire hose.
[1] In some ways, the 1.75-inch hose is a bigger beast than the 2.5-inch hose — for the latter, you tend to use a four-man rather than two-man team, and of course the former has a higher operating pressure (I’m afraid I can’t remember the respective pressures at the moment, and they depend on what kind of nozzle you’re using as well; I’ll have to ask).
[2] Stop reading my blog and watch this video right now.
[3] It’s a shame, I can’t find this guy on the web, can’t recall his name; all I remember was that he was of Asian descent, and that he made a damned good case.
[4] Richard Evans makes a case that the Nazis dominated the medicine of the age, but that’s a distinct issue.
[5] Remember, the “fs” have an “S” sound, not an “F” sound.
[6] I haven’t bothered to give a link here, because if you Google “Nazi evolution” you’ll get a craw full of people making gratuitous Hitler and Nazi accusations (along with treatises trying to convince us that Nazi science was fundamentally flawed).
[7] Whistling in the dark, if you know anything about the Pennsylvania legislature.
[8] Nineteen-fucking-seventy two. Makes you want to puke.
Saturday, June 27, 2009
Saturday, June 20, 2009
What We Know for Sure
“It ain’t what you don’t know that gets you into trouble. It’s what you know for sure that just ain’t so.”
– Mark Twain (maybe)
I think my favorite thing about that quote is that I’ve seen it attributed, with utter certainty, to a number of people. Will Rogers supposedly said it about Herbert Hoover — but then, maybe he was unapologetically quoting Clemens [1]. I’ve also seen claims it originated earlier, with Franklin, but it doesn’t really sound either like Big Ben or his insipid (by his own admission, I think) alter ego, Poor Richard [2].
Anyhow, sorry for the two-week absence — I was indeed busy, first with Fire School and then with helping provide medical coverage for the 24 Hours of Big Bear mountain bike race.
We were busy at the latter event, but thankfully not too busy. They camped us out a little short of mile 7 — the course itself is 12 miles long, and either relay teams or a few hardy solo bikers do indeed pedal it for 24 hours, the highest number of laps winning each category — at the bottom of a ferocious hill.
I’d had a chance to ride that hill, along with about six miles of the course, on the Friday before the race, and can attest that it’s a tricky son of a bitch. It isn’t so much that it’s steep, though a couple of sections were steep, as that it’s rocky — rocks big enough that you need to keep your speed up, for fear of one stopping you cold, but also big enough that staying on top of them is non-trivial. You basically have to aim for the biggest rocks and pedal as fast as you dare, to make sure you bounce along the top. An earlier series of downhill hairpin turns don’t help either, nor does the fact that the downhill section is so long.
I pedaled into camp Friday night, trashed, just as the sun was setting: thankful I hadn’t had to do it in the dark, or as fast as I could, like the racers. The race itself began noon Saturday, and we had a steady but slow stream of patients throughout the ensuing 24, though again we only had one who scared me — but that’s a story for another day.
We did have time to see to the betterment of our trainees; in fact I was called upon to whip up a quick navigational course for them to practice map and compass skills.
I hate doing navs courses on the fly like that; you almost always get a cluster fuck. But in the event, our newbies gave us a different kind of cluster than I was expecting — looking for their first flag, they lost a radio belonging to another search team.
Now, I want to make this clear: to the extent that they didn’t take proper care of another team’s equipment, I blame that squarely on us experienced members. We never should have let them leave camp with something that expensive — I think they’re going for $500 list — improperly secured. So in addition to the obligation of needing to recover that radio for the team’s honor, I also felt a lot of personal responsibility. When the newbies headed out to look for it, accompanied by Carl, an experienced member of the other team, as a matter of course I grabbed my pack and went with them.
Carl and the recruit who’d been carrying the aforementioned radio were trying to retrace the latter’s steps, but in literally trackless West Virginia mountain terrain, covered in greenbriar and, in some spots, rhododendron with boughs as thick as a tree’s, I was dubious that it could be done by eye. Instead, I took the right flank, started at their original jumpoff point, and tried to duplicate the compass bearing they’d been walking.
When I couldn’t get a straight answer from them about what that bearing had been, it told me something. When, as we climbed, we hit an overgrown wood road and they said they’d broken their bearing to follow it uphill, it told me something more.
We stress a very practical style of navigation in search and rescue: we seldom expect people to walk compass bearings, instead teaching them to locate their target on the map and then piece together a path from “travel routes” — trails, ravines, ridgetops, gas lines, whatever is easy to walk — that may be less direct but gets you there faster and with less fatigue, by virtue of being easier to walk than a compass bearing. But when you’re taking travel routes, you take travel routes; when you walk a bearing, you have to walk an accurate bearing. Mixing and matching doesn’t work so well.
What I figured out, by the time we climbed near the ridgetop, was that they’d been veering steadily to the right as they ascended. So that “left flank” that Carl and the newbie were still trying to reconstruct was likely to be a lot farther in my direction than theirs.
If you want to lose something, by the way, a radio isn’t such a bad choice, because for a while at least, if you call it, it will call back to you. Fair is fair, Carl’s invaluable contribution to the exercise was a low-power tone he had his personal radio programmed to deliver, making the nearby (hopefully) lost radio beep at us, but not the other radios on the net, which at that point were still in use by the medical support teams.
We’d been moving, stopping, straining to hear, then repeating for a few iterations when, as faint as you can imagine, I thought I heard beeping.
“I think I hear it,” I said.
Carl: “What direction?”
“I’m not sure; it’s too faint.”
“Let’s move uphill a bit.”
Lather, rinse, repeat.
“Still not sure, but it’s louder now.” Now the second newbie, in line to my left, also thought he heard it.
Another iteration. Much louder now, and to my right. They’d drifted so far to the right that, even adding in my guesstimation of their error to the bearing they should have walked, I’d still undershot by more than the width of our little picket line. I moved toward the noise; lying on the ground in front of me, in a thankfully clear spot of ground, was the errant radio.
“I’ve got it!”
Basically, I rock.
The whole exercise, as it turned out, was emblematic of the Twain quote: the surer we’d been about the path our beginning navigators had walked, the wider the margin by which we’d have missed our mark.
Today’s entry is an exercise in taking stock of what we know and what we don’t about how the MHC genes determine humans’ choice of mates, courtesy of Jan Havlicek and S. Craig Roberts at Charles University in Prague and the University of Liverpool, respectively.
Briefly, the proteins made by the MHC genes are master actors in the vertebrate body’s defense against infection. They help identify infected cells, among other related functions, by grabbing hold of fragments of the invading microbe and displaying those fragments on the cells’ surfaces. This “antigen presentation” both alerts the immune system to the microbe’s presence and marks the infected cells for destruction.
Over the last couple of decades, researchers have been shedding light on another, surprisingly different function of the MHC: in most vertebrates, it seems to dictate an individual odor that somehow influences mate choice. In rodents — the best-studied specie for this phenomenon — females definitely choose mates whose MHC genes are different from theirs, and the effect takes place via a more- or less-attractive odor to that particular female. One girl’s Romeo is another’s Norman Bates [3].
Havlicek’s and Roberts’ concern, though, was whether this phenomenon reaches higher up the evolutionary tree — namely, to human beings. A growing body of research indicates that MHC genes — called HLA in humans — may actually play a role in our choice of mates. “Animal magnetism” may have a very aromatic cause, and one that comes literally through the nose.
The two investigators reviewed the current literature, and found a decidedly mixed bag, with studies showing that people pick HLA-dissimilar mates, that they pick HLA-similar mates, or no HLA effect at all. But the former outnumber the latter, and our hosts believe that there really is an effect there, though one that’s maybe a bit more complicated than we’d initially expected.
One of the more interesting sets of experiments are those in which subjects are given a piece of clothing worn by members of the opposite sex and asked which ones smell the most attractive. The results vary somewhat, but tend toward the conclusion that men with HLA genes that are different than a woman’s smell better to her than men with similar HLA genes.
But thereby hangs the tale: the researchers in the different studies asked their subjects different questions, ranging from “which smells best” to “which smells ‘sexiest’” to “which smells like someone you’d want a long term relationship with.” Those are very different questions!
An interesting exception — though not one that shows up in every study — is that women who are on birth control pills reverse the trend: they pick men whose HLA genes are more similar to theirs. It’s tempting to think that the pill, which basically prevents ovulation by tricking a woman’s body into thinking she’s pregnant, is uncovering a powerful set of biological imperatives: when you mate, outbreed; but when you’re pregnant, seek out relatives, who are more likely to help you raise the child [4]. But pregnancy is a heck of a lot more complicated than the two hormones present in most pills, and post-facto evolutionary arguments can be as slippery as they are compelling.
One series of experiments I hadn’t heard of before reading this paper was those studying the HLA effects on perfume preference: it turns out that people tend to prefer similar perfumes when they have similar genes, and some researchers think that’s because we use perfumes to enhance and complement, rather than simply hide, our natural body smells.
Of course, preference is all well and good, but it doesn’t always wind up at the altar: there’s a body of evidence suggesting women like rugged he-men faces for one-night stands, but gentler faces for long-term relationships [5]. When our Euro Reviewers surveyed studies of actual mate choice, the picture got murkier, with two studies suggesting people choose dissimilar mates, one similar, and a whopping seven showing no statistically significant effect at all.
This isn’t particularly surprising, though: as I’ve said before, higher mammals don’t do anything for just one reason. It may well be that HLA-associated body odor plays an important role in mate selection, but that a number of other factors also enter into it, and they’ll tend to obscure the odor effect.
H & R raise a very interesting possibility along these lines, which comes from a study of facial preference: When you show women pictures of men’s faces, they tend to pick those more HLA-similar to them as potential long-term mates. The authors don’t mention whether this study controlled for pregnancy or birth-control use, but there’s more straightforward way in which this result can make sense: maybe we’re looking for a Goldilocks level of difference with our mates, rather than just maximizing difference.
Though we know that inbreeding can be very bad, we’ve never nailed down the idea that maximal outbreeding is necessarily good. In fact, our authors map out no fewer than four possible reasons that we may seek HLA differences, or general outbreeding, with our mates, any or all of which may be true — or not. They cite research that suggests an intermediate level of outbreeding may be best.
What emerges from the murk of insufficient data is that we may have battling preferences: our eyes tell us to seek similarity, our noses to seek difference. As in many other biological systems, the struggle between two opposed systems pushes us toward an equilibrium that maximizes benefit.
To be fair, though my account of the Affair of the Missing Handheld above is writ from a singular perspective, in retrospect I can see the friction between the contradictory set of tactics we were following may indeed have put us closer to the target than either one alone could have. I don’t think the two searchers on my left flank could have realistically retraced the newbie’s steps; but by the same token, if I’d simply tried to reproduce the bearing they were supposed to have walked I would have wound up far to the left of where we needed to be.
“All things in moderation, including moderation” — but even so, sometimes, despite what we want, what we need is a nice medium.
[1] As an interesting side note, there’s a common phenomenon of historical figures apparently, from our modern-day vantage, trying to rip off earlier writers, when in fact they were just making quotes that were so obvious to their listeners that an attribution wasn’t necessary. I’ve often wondered whether Roosevelt’s “my crowded hour” wasn’t such a quote, since it sounds very Shakespearian — but I don’t know where it appears in the Bard, if at all.
[2] Dick may have been a pratt, but Ben was the original Buckaroo Banzai — maybe not so much with the gun- and swordplay, but show me any scientist in history who was such a fucking dangerous enemy to make. He’s a hero of mine; so is Roosevelt, for that matter.
[3] I exaggerate — the effect is more subtle than that, but very real.
[4] Scary possibility: some studies suggest that women who met their mates while on birth control are more likely to be unfaithful than those who aren’t. One possibility is that the pill undermines natural mate choice, sticking you with a guy you’re less thrilled with in the long term. The other, formal mind you, possibility is that girls on the pill are tramps — not that there’s anything wrong with that, some of my best friends in grad school were tramps. God bless ’em.
[5] On the average, ladies; and I’m sure that many, many guys wouldn’t turn down a roll in the hay with, say, a Tara Reid — I’m just picking a name off the top of my head, mind you — but want a girl with more existential substance for the long haul.
– Mark Twain (maybe)
I think my favorite thing about that quote is that I’ve seen it attributed, with utter certainty, to a number of people. Will Rogers supposedly said it about Herbert Hoover — but then, maybe he was unapologetically quoting Clemens [1]. I’ve also seen claims it originated earlier, with Franklin, but it doesn’t really sound either like Big Ben or his insipid (by his own admission, I think) alter ego, Poor Richard [2].
Anyhow, sorry for the two-week absence — I was indeed busy, first with Fire School and then with helping provide medical coverage for the 24 Hours of Big Bear mountain bike race.
We were busy at the latter event, but thankfully not too busy. They camped us out a little short of mile 7 — the course itself is 12 miles long, and either relay teams or a few hardy solo bikers do indeed pedal it for 24 hours, the highest number of laps winning each category — at the bottom of a ferocious hill.
I’d had a chance to ride that hill, along with about six miles of the course, on the Friday before the race, and can attest that it’s a tricky son of a bitch. It isn’t so much that it’s steep, though a couple of sections were steep, as that it’s rocky — rocks big enough that you need to keep your speed up, for fear of one stopping you cold, but also big enough that staying on top of them is non-trivial. You basically have to aim for the biggest rocks and pedal as fast as you dare, to make sure you bounce along the top. An earlier series of downhill hairpin turns don’t help either, nor does the fact that the downhill section is so long.
I pedaled into camp Friday night, trashed, just as the sun was setting: thankful I hadn’t had to do it in the dark, or as fast as I could, like the racers. The race itself began noon Saturday, and we had a steady but slow stream of patients throughout the ensuing 24, though again we only had one who scared me — but that’s a story for another day.
We did have time to see to the betterment of our trainees; in fact I was called upon to whip up a quick navigational course for them to practice map and compass skills.
I hate doing navs courses on the fly like that; you almost always get a cluster fuck. But in the event, our newbies gave us a different kind of cluster than I was expecting — looking for their first flag, they lost a radio belonging to another search team.
Now, I want to make this clear: to the extent that they didn’t take proper care of another team’s equipment, I blame that squarely on us experienced members. We never should have let them leave camp with something that expensive — I think they’re going for $500 list — improperly secured. So in addition to the obligation of needing to recover that radio for the team’s honor, I also felt a lot of personal responsibility. When the newbies headed out to look for it, accompanied by Carl, an experienced member of the other team, as a matter of course I grabbed my pack and went with them.
Carl and the recruit who’d been carrying the aforementioned radio were trying to retrace the latter’s steps, but in literally trackless West Virginia mountain terrain, covered in greenbriar and, in some spots, rhododendron with boughs as thick as a tree’s, I was dubious that it could be done by eye. Instead, I took the right flank, started at their original jumpoff point, and tried to duplicate the compass bearing they’d been walking.
When I couldn’t get a straight answer from them about what that bearing had been, it told me something. When, as we climbed, we hit an overgrown wood road and they said they’d broken their bearing to follow it uphill, it told me something more.
We stress a very practical style of navigation in search and rescue: we seldom expect people to walk compass bearings, instead teaching them to locate their target on the map and then piece together a path from “travel routes” — trails, ravines, ridgetops, gas lines, whatever is easy to walk — that may be less direct but gets you there faster and with less fatigue, by virtue of being easier to walk than a compass bearing. But when you’re taking travel routes, you take travel routes; when you walk a bearing, you have to walk an accurate bearing. Mixing and matching doesn’t work so well.
What I figured out, by the time we climbed near the ridgetop, was that they’d been veering steadily to the right as they ascended. So that “left flank” that Carl and the newbie were still trying to reconstruct was likely to be a lot farther in my direction than theirs.
If you want to lose something, by the way, a radio isn’t such a bad choice, because for a while at least, if you call it, it will call back to you. Fair is fair, Carl’s invaluable contribution to the exercise was a low-power tone he had his personal radio programmed to deliver, making the nearby (hopefully) lost radio beep at us, but not the other radios on the net, which at that point were still in use by the medical support teams.
We’d been moving, stopping, straining to hear, then repeating for a few iterations when, as faint as you can imagine, I thought I heard beeping.
“I think I hear it,” I said.
Carl: “What direction?”
“I’m not sure; it’s too faint.”
“Let’s move uphill a bit.”
Lather, rinse, repeat.
“Still not sure, but it’s louder now.” Now the second newbie, in line to my left, also thought he heard it.
Another iteration. Much louder now, and to my right. They’d drifted so far to the right that, even adding in my guesstimation of their error to the bearing they should have walked, I’d still undershot by more than the width of our little picket line. I moved toward the noise; lying on the ground in front of me, in a thankfully clear spot of ground, was the errant radio.
“I’ve got it!”
Basically, I rock.
The whole exercise, as it turned out, was emblematic of the Twain quote: the surer we’d been about the path our beginning navigators had walked, the wider the margin by which we’d have missed our mark.
Today’s entry is an exercise in taking stock of what we know and what we don’t about how the MHC genes determine humans’ choice of mates, courtesy of Jan Havlicek and S. Craig Roberts at Charles University in Prague and the University of Liverpool, respectively.
Briefly, the proteins made by the MHC genes are master actors in the vertebrate body’s defense against infection. They help identify infected cells, among other related functions, by grabbing hold of fragments of the invading microbe and displaying those fragments on the cells’ surfaces. This “antigen presentation” both alerts the immune system to the microbe’s presence and marks the infected cells for destruction.
Over the last couple of decades, researchers have been shedding light on another, surprisingly different function of the MHC: in most vertebrates, it seems to dictate an individual odor that somehow influences mate choice. In rodents — the best-studied specie for this phenomenon — females definitely choose mates whose MHC genes are different from theirs, and the effect takes place via a more- or less-attractive odor to that particular female. One girl’s Romeo is another’s Norman Bates [3].
Havlicek’s and Roberts’ concern, though, was whether this phenomenon reaches higher up the evolutionary tree — namely, to human beings. A growing body of research indicates that MHC genes — called HLA in humans — may actually play a role in our choice of mates. “Animal magnetism” may have a very aromatic cause, and one that comes literally through the nose.
The two investigators reviewed the current literature, and found a decidedly mixed bag, with studies showing that people pick HLA-dissimilar mates, that they pick HLA-similar mates, or no HLA effect at all. But the former outnumber the latter, and our hosts believe that there really is an effect there, though one that’s maybe a bit more complicated than we’d initially expected.
One of the more interesting sets of experiments are those in which subjects are given a piece of clothing worn by members of the opposite sex and asked which ones smell the most attractive. The results vary somewhat, but tend toward the conclusion that men with HLA genes that are different than a woman’s smell better to her than men with similar HLA genes.
But thereby hangs the tale: the researchers in the different studies asked their subjects different questions, ranging from “which smells best” to “which smells ‘sexiest’” to “which smells like someone you’d want a long term relationship with.” Those are very different questions!
An interesting exception — though not one that shows up in every study — is that women who are on birth control pills reverse the trend: they pick men whose HLA genes are more similar to theirs. It’s tempting to think that the pill, which basically prevents ovulation by tricking a woman’s body into thinking she’s pregnant, is uncovering a powerful set of biological imperatives: when you mate, outbreed; but when you’re pregnant, seek out relatives, who are more likely to help you raise the child [4]. But pregnancy is a heck of a lot more complicated than the two hormones present in most pills, and post-facto evolutionary arguments can be as slippery as they are compelling.
One series of experiments I hadn’t heard of before reading this paper was those studying the HLA effects on perfume preference: it turns out that people tend to prefer similar perfumes when they have similar genes, and some researchers think that’s because we use perfumes to enhance and complement, rather than simply hide, our natural body smells.
Of course, preference is all well and good, but it doesn’t always wind up at the altar: there’s a body of evidence suggesting women like rugged he-men faces for one-night stands, but gentler faces for long-term relationships [5]. When our Euro Reviewers surveyed studies of actual mate choice, the picture got murkier, with two studies suggesting people choose dissimilar mates, one similar, and a whopping seven showing no statistically significant effect at all.
This isn’t particularly surprising, though: as I’ve said before, higher mammals don’t do anything for just one reason. It may well be that HLA-associated body odor plays an important role in mate selection, but that a number of other factors also enter into it, and they’ll tend to obscure the odor effect.
H & R raise a very interesting possibility along these lines, which comes from a study of facial preference: When you show women pictures of men’s faces, they tend to pick those more HLA-similar to them as potential long-term mates. The authors don’t mention whether this study controlled for pregnancy or birth-control use, but there’s more straightforward way in which this result can make sense: maybe we’re looking for a Goldilocks level of difference with our mates, rather than just maximizing difference.
Though we know that inbreeding can be very bad, we’ve never nailed down the idea that maximal outbreeding is necessarily good. In fact, our authors map out no fewer than four possible reasons that we may seek HLA differences, or general outbreeding, with our mates, any or all of which may be true — or not. They cite research that suggests an intermediate level of outbreeding may be best.
What emerges from the murk of insufficient data is that we may have battling preferences: our eyes tell us to seek similarity, our noses to seek difference. As in many other biological systems, the struggle between two opposed systems pushes us toward an equilibrium that maximizes benefit.
To be fair, though my account of the Affair of the Missing Handheld above is writ from a singular perspective, in retrospect I can see the friction between the contradictory set of tactics we were following may indeed have put us closer to the target than either one alone could have. I don’t think the two searchers on my left flank could have realistically retraced the newbie’s steps; but by the same token, if I’d simply tried to reproduce the bearing they were supposed to have walked I would have wound up far to the left of where we needed to be.
“All things in moderation, including moderation” — but even so, sometimes, despite what we want, what we need is a nice medium.
[1] As an interesting side note, there’s a common phenomenon of historical figures apparently, from our modern-day vantage, trying to rip off earlier writers, when in fact they were just making quotes that were so obvious to their listeners that an attribution wasn’t necessary. I’ve often wondered whether Roosevelt’s “my crowded hour” wasn’t such a quote, since it sounds very Shakespearian — but I don’t know where it appears in the Bard, if at all.
[2] Dick may have been a pratt, but Ben was the original Buckaroo Banzai — maybe not so much with the gun- and swordplay, but show me any scientist in history who was such a fucking dangerous enemy to make. He’s a hero of mine; so is Roosevelt, for that matter.
[3] I exaggerate — the effect is more subtle than that, but very real.
[4] Scary possibility: some studies suggest that women who met their mates while on birth control are more likely to be unfaithful than those who aren’t. One possibility is that the pill undermines natural mate choice, sticking you with a guy you’re less thrilled with in the long term. The other, formal mind you, possibility is that girls on the pill are tramps — not that there’s anything wrong with that, some of my best friends in grad school were tramps. God bless ’em.
[5] On the average, ladies; and I’m sure that many, many guys wouldn’t turn down a roll in the hay with, say, a Tara Reid — I’m just picking a name off the top of my head, mind you — but want a girl with more existential substance for the long haul.
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