Sexual or sexist? Replication of human pheromones

Biology 202
2000 First Web Report
On Serendip

Sexual or sexist? Replication of human pheromones

Caitlin Costello

From the elixer in Love Potion Number Nine to the Orgasmatron in Orgazmo, the media reflect a popular fascination with the idea of an object that can control other people's sexual desires and behaviors. On a similar but dorkier note, I have occasionally heard at Haverford someone attribute a sexual "lucky streak" to the influence of pheromones. In our well-educated but socially awkward mind frame, we have hit on a more promising possibility than magic potions or radar guns. From the Greek for "excitement carrier", pheromones carry chemical messages between members of the same species (2). Present in many animals and often responsible for aspects of mating behavior, the idea of pheromones in humans has in recent years been a subject of interest. The idea of pheromone perception as a "sixth sense" is intriguing, as it means our behavior is influenced by input from outside stimuli that we cannot consciously perceive. Evidence points to the output by and influence on humans of natural pheromones, and these pheromones are under attempt at imitation by commercial products. What are the possible ramifications of such developments? Experimental evidence also shows differences in the way men and women respond to pheromones, and the possible implications of these differences on gender roles is the aspect of human pheromone research that interests me most.

These chemical signals are detected in the vomeronasal organ, or VNO, which is present in the noses of most species of vertebrates. In other mammals, the VNO is located in a longitudinal bulge at the base of either side of the nasal septum (4). Humans lack this bulge marking the position of the VNO, and although there are nerve bundles running from the human VNO to the brain, it is still unclear whether they contain actual sensory neurons or just autonomic nerves. Unlike that in animals, the human VNO does not have an obvious sensory epithelium; however, it contains cells that are considered to be bipolar receptor neurons. The human VNO is thought to be stimulated by airborne chemicals, as opposed to stimuli dissolved in mucus (3). Although most exploration of the possibilities of human pheromone perception has happened recently, scientists have known about the human VNO since 1703, when Dutch surgeon Roysch discovered it in the nose (2). Since then the VNO has been commonly thought to be present only in fetuses, disappearing over the course of prenatal development. In the 1980s, however, two studies found that the VNO actually was present in adults (3). The differences between the VNO of other animals that are known to produce and perceive pheromones and the VNO of humans leave open the question of whether the human VNO is today a functional organ or merely a vestigial one, a now useless relic of our ancestors.

Just as the evidence of a functional VNO in other animals is clearer than that in humans, the direct connection between pheromones and mating is clearer in simpler creatures. When sea urchins release pheromones, the chemical message triggers other urchins in the colony to eject their sex cells simultaneously (9). This cause and effect relationship between pheromones and sexual behavior leaves little question; in humans, however, the story is more complicated. As Martha McClintock of the University of Chicago says, "We're not as simple as a cockroach. It's not the case that we're going to have a single molecule that's going to compel us to cross the room" (1).

Although she pointed out that pheromones cannot work as simply and thoroughly on humans as on other animals, McClintock was the one who published the first definitive study showing that humans do produce and respond to pheromones (1). When she put samples of the underarm sweat of women at different menstrual changes under the noses of female subjects, the length of these subjects' own cycles was significantly altered (1). It has been questioned whether the women were responding to a smell instead of to chemical signals, but since the subjects were unaware of any odor of the sweat during the experiment, there is the distinct possibility that "the mechanism of [odor] transfer did not involve the nose at all, but diffusion of chemical compounds through the skin which may occur when the sample was placed on the subject's upper lip" (7). McClintock's finding should come as no surprise to any women who has lived in a college dorm and synchronized cycles with her roommates. What may be news to these women, however, is a finding reported by Charles Wysocki of the Monell Chemical Senses Center in Philadelphia that the smells from the underarms of men can also affect the menstrual cycle (3). To resolve the ambiguity of whether these influences come from the sense of smell or the perception of chemical signals, Wysocki is studying the effects of the destruction of the VNO in animals (3).

Beyond its perceivable odor, underarm sweat has been shown to have a pheromone component produced by the chemical androstenol. At University College, London, an experiment showed that after being briefly exposed to androstenol, females had more social interactions with males (6). Women seem to be more affected by underarm sweat than men; George Dodd of the University of Warwick, who claims to have discovered a possible progenitor of androstenone, a steroid called Osmone 1, a says that women are 1000 times more sensitive than men to these steroid musk molecules (6).

Although McClintock's study received great recent attention, there has been evidence for at least 30 years that humans are affected by chemical pheremones they definitely cannot smell. At that time David Berliner of the University of Utah noticed that extracts of skin cells left in open flasks in his lab left the lab workers who were exposed to them feeling warmer and friendlier. When he closed the flasks, these good feelings ceased. Since these cells gave off no odor, Berliner suspected that they contained pheromones, which he confirmed with further analysis of the extracts (5).

The perception of pheromones seems to have a greater effect on women than men; whether reacting to perceivable odors or chemical pheromones, "Women are more likely to use their sense of smell to decide whether or not they'll actually go through with a sexual encounter," according to psychologist Rachel Herz of the Monell Chemical Senses Center in Philadelphia (1). In a study in Switzerland, women preferred the smell of t-shirts belonging to men with immune systems different from their own. This perception may have an evolutionary advantage; according to Wayne Potts of the University of Utah, the genes of the immune system control odors, and different versions of these genes emit different smells (1). When two people with different immune systems reproduce, the resulting combination of immune system genes seems to better be able to fight of infections.

The increasing body of evidence that humans have a functional VNO and respond to sex-related pheromones has prompted a surge of commercial attempts at replicating natural pheromones. Although hardly a new development, foods that have for centuries been claimed to have aphrodisiac qualities, like truffles and shellfish, have recently been found to chemically correspond to human pheromones (8), and their supposed powers have gained a bit more validity. Again the emphasis is on the effect of these chemicals on women, especially that of the androstenone found in truffles, toward which women are drawn and men repulsed (8).

A leader in the market of pheremone based products is David Berliner himself, who now markets his own line of human pheremone perfume called Realm. Although he touts his its superiority over perfumes containing pig pheromone, he does not claim that his perfume acts as a "love potion" with any influence over those who smell it; rather, its benefit, he says, lies in its ability to make the wearer of the perfume feel "Self confident. Attractive. Romantic" (10). Other pheromone perfumes do make the claim to have a direct connection to increased sexual activity. Whether this effect comes from pheromonal influence over possible mates or increased attractiveness in the wearer due to greater confidence, there is some support that it "works." In one study, 74 percent of subjects testing Athena, a pheromonal perfume developed by Dr. Winnifred Cutler, "experienced an increase in hugging, kissing and sexual intercourse" (9).

If the popularity of pheromone based commercial products continues, they may develop to the point where they accurately imitate the effects of natural human pheromones, possibly even able to influence the behavior of those other than the users of the products. There is something inherently spooky about the idea that our behavior can be influenced by sensory input we have no idea we are even receiving. A deeper threat, however, comes from the implications that pheromone research might have on existing gender roles and relations, since women seem to be more sensitive to pheromonal messages. What does this mean for increased popularity and commercialism? If pheromone perception is indeed a "sixth sense," the advantage in the use of this sense belongs to woman. This is an interesting concept itself, although we talk, for example, of men having superior spatial abilities and women superior linguistic abilities, we don't usually associate an advantage to either gender in the basic sensory modalities. If this is a way in which women can use their bodies better than men, it might change some notions of male physical superiority. On the other hand, however, the "sixth sense" represents a power men have over women; we can't choose to ignore pheromonal input or change in any way how we receive it, but the possibilities are there to artificially increase how we produce it. Will a man one day put on a perfume that can cause any woman to have sex with him? Will men one day be able to control the menstrual cycles of women on a whim by pulling the trigger on a gun like the Orgasmatron? Given the complexities of the way humans transmit chemical signals, these scenarios probably lie outside of the realm of possibility, but the prospect of men gaining even a small amount of greater sexual control over women is nonetheless frightening.

WWW Sources

1) Sniffing out a Mate

2) Chemicals that cause excitement

3) The Science of Sex

4) The Vomeronasal Organ

5) A tale of two noses

6) Human Male Sweat Extract Sends Strong Message

7) Stinkin' Synchin'

8) Pheromol Factor

9) Pheromones: Potential participants in your sex life

10) Realm Fragrances' commercial site

 

 

Comments made prior to 2007

Good Morning Folks, While in PNG I caught a Brown Tree Snake in the AM,put it in my louvered window in the afternoon and about 9 PM another BTS appearred on the screen outside the first specimen. I assumed it was pheromone attraction.

 

Do snakes have a VNO?? Could their pheromone be synthesized? The BTS is really causung grief in many places and they need some new answers ... Fred Gibson, 10 January 2007