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Say it ain't so, Joe
You've probably noticed that until now we've accepted the hypothesis that people actually have a vomeronasal organ (VNO) -- the sniffer that other animals use to detect pheromones. After all, the discovery of small pits in human noses during the 1980s is what reinvigorated the possibility that pheromones actually affect humans. |
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But skeptics say it's too soon to conclude that those little pits-in-the-snout are indeed VNOs. Charles Wysocki, an expert on the animal VNO at the Monell Chemical Senses Center in Philadelphia, says there are "gaping chasms" in the claim that humans have a VNO that responds to human pheromones. Say we saunter down skeptics' street? |
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It ain't so, Joe
Recall that until the 1980s, the accepted wisdom was that the human VNO appeared briefly during fetal development, and then disappeared (this exact "now-you-see-the-VNO-and-now-you-don't" occurs, as we mentioned, in birds). Then, for a while at least, people began finding organs that looked suspiciously like a VNO in people. But the pendulum could be swinging back again: Wysocki says recent evidence shows that the human VNO indeed does develop -- and then disappears -- in the fetus (see "Luteinizing Hormone-releasing Hormone" in the bibliography).
Monkey business
Three separate researchers, Wysocki says, have recently found this negative result, although none has published the results. If they're correct, the implication is clear: we are closer evolutionarily to Old World than New World primates, and if apes and chimps lack the organ, Wysocki says, "One would be hard pressed to generate an argument that this structure reemerged with the advent of Homo sapiens." |
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A question of wiring
Even if those ubiquitous pits in the human nasal septum are VNOs (remember, they could be something entirely different), who's to say they can send signals to the brain? "This connection has never been demonstrated," says Wysocki. "To my knowledge, nobody has ever looked." Proving this proposition would require an anatomist to put a special stain (defined) on a cadaver's suspected VNO, and then wait several months for the stain to creep up nerve cells toward the brain. Until this experiment is done, Wysocki says, we won't know whether the VNO is really wired. And without wiring, it can't function as a VNO. |
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Still, says VNO specialist Michael Meredith, of Florida State University in Tallahassee, the electrical measurements of apparent VNO activity produced by Berliner's colleagues do carry some weight. "Looking at the way they describe the experiment, it seems reasonable to me" that the signals represent nerve impulses from the VNO to the brain. "It's not very easy to imagine what could be producing those electrical signals, if it's not what they say." But in the next sentence, Meredith's skepticism returns. "This fits in beautifully with their [Berliner's] commercial interests."
Here's the weird part...
Yes, says Wysocki, it could. Recall that the nose has many tricks when it comes to detecting chemicals. Everybody knows about the smell receptors in a tissue called the olfactory epithelium. But the nose can also detect chemicals with nerves connected to the trigeminal nerve, AKA the fifth cranial nerve. It's already known that the trigeminal nerve can detect chemicals in the mouth and nose, Wysocki says. Bless its neuronal heart, the nerve also conveys the burning taste of chili peppers and the welcome blast of horseradish. Still, despite its role in the culinary arts, the trigeminal is not part of the sense of smell -- nor is it part of the VNO system, if one exists. And recently scientists have found another nerve, called nervus terminalis, that independently connects the nose and the basal forebrain, and could also be carrying signals to the brain. One thing is sure: something is going on with chemical communication between men and women, at least if you put any faith in the stinky tee shirts hypothesis. |
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