This article first appeared in the St. Louis Beacon, Feb. 24, 2010 - On Valentine's Day last week I sensed a subtle chemistry afoot.
I can remember with great clarity the first time I noticed a girl. I was 14 years old, and her name was Karen Hutchens. The puppy love of a raw adolescent boy is a powerful force and gave me no peace that year. I used to bicycle past her house, more than a mile from mine, simply on the off chance she would see me.
But she never did.
I didn't exist for her, all that long year. And I couldn't do anything about it. I was a helpless prisoner of the awkwardness of youth. What I desperately needed, what I couldn't figure out, was a way to get her attention.
The following year, in my 9th grade biology book, I stumbled across what seemed like the answer to my problem. Biology is like that, full of unexpected surprises. I was reading about moths.
Imagine for a moment you were a moth, eager for a sexual escapade -- how do you get the attention of a partner? The nearest moth is likely thousands of meters away, so yelling isn't going to get it done. Nor can they see you -- moths fly at night, and do not glow in the dark like fireflies. As I began to fully appreciate the moth's quandary, I couldn't help feel a kinship. I knew, that year my childhood ended, just how the moth felt.
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But moths make little moths all the time, so clearly they have solved the problem of getting each other's attention. How do they do it?
It turns out the female moth secretes a chemical, called a pheromone, that is a powerful sex attractant (in moths its the female that makes the first move). This stuff is incredibly powerful. A male responds to concentrations as low as one molecule per 100,000,000,000,000,000 molecules of air.
When a lusty female releases a tiny dab of the stuff into the air, about one hundredth of a microgram, it is carried away by the wind and will get the attention of a male 4,000 meters downwind. That's two and a half MILES! Any male moth that gets a wiff flies upwind toward higher concentrations of the pheromone, ever closer to the female, until the lovers meet. Boy, was this ever what I was looking for!
That was 52 years ago, and I've never gotten over my interest in pheromones.
However, humans are not moths; and, for me, age not chemistry solved the riddle of how to attract the attention of females. But over the years I have wondered: Do humans have sex pheromones? There is an abundance of anecdote, but no clear experimental evidence, that human body odors affect sexual behavior.
Musk-smelling compounds are particularly notorious. The musky synthetic perfume exaltolide15-pentadecanolide, for example, is perceived clearly only by sexually mature women, and their sensitivity is heightened at ovulation. Could there have been an ancestral musk-like male sex pheromone that stimulated sexually receptive women?
Something is definitely going on. There is clear evidence that sweat and vaginal secretions affect other people's sexual physiology, if not their behavior, even when the odors cannot be consciously smelled. Three cases in point:
- The so-called dormitory effect. There is a strong tendency for the menstrual cycles of female roommates to synchronize. Apparently a woman's sweat influences the timing of other women's cycles.
- Men's beards grow significantly faster in the presence of women than in all-male settings.
- The presence of men seems to influence the timing of female ovulation.
The possibility of attracting members of the opposite sex with body odor (or the lack of it) is, of course, hardly a novel idea. The whole deodorant and perfume industries depend on this hope. Last week, on Valentine's Day, I'm sure perfume as well as candy and flowers graced many a man's attempt to attract his chosen female's interest.
Might I have attracted Karen Hutchen's attention with scent? A raft of comic possibilities present themselves to my imagination, but I know as a scientist that it is quite unlikely that human females respond like moths to powerful sexual attractant chemicals. Practically alone among mammals, humans do not have an acute sense of smell: The olfactory portions of our brains are far less pronounced than those of a cat or dog. Love among humans is not a chemical reaction. For better or worse, we humans are visual critters, responding far more to what we see than what we smell. Love for us is in the eyes of the beholder, not his nose.
Luckily, a wonderful woman named Barbara was attracted to me despite my lack of female-attracting pheromones. We were married shortly before Valentine's Day, on the same day St. Louis won the Super Bowl, but 18 years earlier, in a blizzard.
How did I succeed in capturing so desirable a woman without the help of pheromones?
I had a heck of a head of hair then, a red "afro" that sprouted out from my head alarmingly. I'd like to think it was the first kiss that snared her attention, but I suspect it was the visual cue of all that hair. I've a lot less of it now, and Barbara's with me still, so maybe I should attribute my mate-attracting success to blind luck.
'On science'
George B. Johnson's "On Science" column looks at scientific issues and explains them in an accessible manner. There is no dumbing down in Johnson's writing; rather he uses analogy and precise terms to open the world of science to others.
Johnson, Ph.D., professor emeritus of Biology at Washington University, has taught biology and genetics to undergraduates for more than 30 years. Also professor of genetics at Washington University’s School of Medicine, Johnson is a student of population genetics and evolution, renowned for his pioneering studies of genetic variability.
He has authored more than 50 scientific publications and seven texts, including "BIOLOGY" (with botanist Peter Raven), "THE LIVING WORLD" and a widely used high school biology textbook, "HOLT BIOLOGY."
As the founding director of The Living World, the education center at the St Louis Zoo, from 1987 to 1990, he was responsible for developing innovative high-tech exhibits and new educational programs.