A couple of psychiatrists from the University of Utah claimed to have found two sex pheromones in humans. A study from , written by McClintock, supported their findings and pushed the use of human pheromones into vogue. However, there is no evidence that old world monkeys and great apes, including humans, have the ability to detect such chemical cues in the same way as mice.
It is a vestigial organ, a hopeless hangover from our deep mammalian ancestry. Odours can trigger attraction, especially if familiar, but that's not the same as pheromones Credit: Getty Images. And yet, the same putative pheromones are still sold today. In fact, some researchers, including Doty, believe that no mammals are strongly influenced by pheromones. This viewpoint reached its apotheosis in the s, with Doty commonly at the vanguard.
Mammals, many argued, were far too complex to be at the whims of such simple molecules. Take copulin, a collection of molecules discovered in the late s in laboratory-kept rhesus monkeys. Secreted from the vagina of females, a waft of this supposed pheromone could beget sexual arousal, masturbation, and mounting from males.
That much is true. The handful of males used in the study had met the females before, learnt their distinctive smell, and were simply getting turned on. Copulin was more akin to a perfume than a pheromone. Which is apt — copulin is also used as an ingredient in the perfume industry. Are pheromones real? Credit: Getty Images.
Many so-called pheromones contain so many chemicals that they defy the definition of simplicity. Others only work on certain test subjects, and not others. And, just like copulin, the majority can be explained by prior learning to distinctive odour cues.
Mammals, and humans, were simply too complex for pheromones, she thought. Then, in , she discovered darcin , a single protein found in the urine of male mice. To find darcin, Hurst and her colleagues went back to basics. Using the same formula as the original study on Bombykol, the active molecule was isolated from urine and tested again on mice, in isolation. Importantly, darcin alone elicited the same response as when using pure urine.
And to remove any possibility that the mice learnt the smell of choice males, the females were reared in girl-only clubs, away from the sight, sound, or smell of male mice. The question is, can we do the same for humans? It seems highly unlikely. Years of learning, personal preferences, and a lack of reflexive responses can break down any carefully controlled trial.
There could be any number of extraneous factors not taken into account, too many other explanations for conclusions drawn.
Testing the supposed impact of pheromones may only be possible in newborn babies Credit: Alamy. But that might not be true for newborns. However, most proper, well-controlled scientific studies have failed to show any compelling evidence. Lipophilic compounds are those that tend to combine with, or are capable of dissolving in lipids, or fats. When exposing a group of women to a scent of sweat from other women, their menstrual cycles either accelerated or slowed down, depending on whether the sweat was collected before, during, or after ovulation.
The scientists said that the pheromone collected before ovulation shortened the ovarian cycle, while the pheromone collected during ovulation lengthened it. There are four main types of pheromones:. Releaser pheromones : These elicit an immediate response, and the response is rapid and reliable. They are usually linked to sexual attraction. Primer pheromones : These take longer to get a response.
They can, for example, influence the development or reproduction physiology , including menstrual cycles in females, puberty , and the success or failure of pregnancy. They can alter hormone levels in other beings. In some mammals, scientists found that females who had become pregnant and were exposed to primer pheromones from another male could spontaneously abort the fetus.
Signaler pheromones : These provide information. They may help the mother to recognize her newborn by scent. Fathers cannot usually do this. Signaler pheromones give out our genetic odor print. Modulator pheromones : They can either alter or synchronize bodily functions. They are usually found in sweat. In animal experiments, scientists found that when placed on the upper lip of females, they became less tense and more relaxed. A study, published in Respirology in January , showed that a substance called AND progesterone derivative 4,androstadienone caused swelling in the erectile tissue of female noses.
This was taken as evidence that AND might be a functioning pheromone. Another contender for the role of human pheromone is androstadienone. There is some evidence that androstadienone, a component of male sweat, increases attraction, affects mood and cortisol levels and activates brain areas linked to social cognition.
One study found that androstadienone increased cooperative behavior in males. Androstenone, secreted only by males, has also been tested for its potential role as a pheromone. Olfactory research can be extremely tricky to conduct: smells are invisible and hard to control, there is no real standardised system for labelling and evaluating odours, and a wealth of potentially confounding variables need to be controlled for. In the s and s, there was a strong focus on testosterone-derived androstenone and androstenol , possible pheromones in pigs also found in human armpits.
A number of studies have investigated the effect of these substances on human behaviour, focusing on social interactions and the evaluation of sexual partners. Despite a general pattern for these substances to increase social contact between males and females, findings are extremely inconsistent. In the s the focus shifted to the similar androstadienone and oestratraenol, an oestrogen-derived substance produced in pregnant women.
These were the compounds studied in several experiments that examined the vomeronasal organ VNO — a tubular structure located in the nasal cavity which, in some species, is involved in processing pheromones.
This suggested the existence of human pheromones, as a functioning VNO would provide humans the ability to process pheromones. Research into these four pheromone candidates suffers from all sorts of problems. The substances are used in concentrations between several and millions of times higher than they occur naturally in humans.
Experiments tend to be beset with methodological and statistical issues, leading to a contradictory or inconclusive findings. Publication bias leaves it likely that only positive results are published, artificially increasing the amount of supposedly supportive evidence, and findings have often not been independently replicable.
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