YOU may think you can mask it with a shower and a bit of deodorant, but every time you walk into a room, a whiff of your body odour drifts in your wake. It might be – these are just a few words that trained perfumers have used to classify the different “flavours” of natural BO.
While it is clear that odour and perfumes can alter the moods of those around you, it remains a mystery whether there are any unique agents produced by the human body, namely pheromones, that specifically alter other people’s mood, behaviour or physiological arousal.
The idea makes sense. We know that and that they play an important role in mating. But after a flurry of studies hinted that humans shared this trait, researchers started to pick holes in the data and the idea seemed to be left to rest. Quietly, though, a handful of researchers are still digging away, with some tantalising findings suggesting that the pursuit isn’t in vain.
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Do human pheromones exist?
The hunt for human pheromones began in the 1950s. Over the decades, researchers focused their attention on two steroid molecules, and . These chemicals are closely related to male and female sex hormones and can be found in bodily fluids like human sweat. A flurry of experiments in the early 2000s seemed to suggest that they sway people’s judgements of qualities like dominance or fertility – both of which might have been important for sexual success in our evolutionary past.
Definitive evidence of human pheromones is still lacking, with many conflicting findings. That is partly a result of science’s “replication crisis” – whereby it was discovered that the results of many experiments were impossible to reproduce. Many of the studies on human pheromones had used small numbers of people, for example, which could have created false positive results that disappear under further scrutiny. Such concerns make it hard to draw strong conclusions from historic research, but newer findings seem to be resurrecting the case.
In 2014, for instance, at the Chinese Academy of Sciences and his colleagues devised a clever experiment to test the effects of androstadienone and estratetraenol on perceptions of gender. The participants watched videos of moving dots arranged to look like a human walking, then were asked to say whether they thought it was masculine or feminine. Zhou found that , while heterosexual women were more likely to identify it as male when they smelt androstadienone. Interestingly, gay men responded in much the same way as straight women. (The pattern for gay or bisexual women was less clear-cut, and there was no data available for bisexual men.)
Pheromones and attraction
Meanwhile, at the Hong Kong Polytechnic University and his team recently asked 76 heterosexual men to take part in a “delayed gratification” task, in which they could either choose to see a sexually explicit picture of an attractive woman (as judged by an independent group of heterosexual men) immediately, for a small amount of time, or wait and see the image for longer. They completed 10 trials in total. Exposure to low concentrations of estratetraenol seemed to . Wu considers this to be a sign that estratetraenol increases sexual motivation among straight men.
Seventy-six participants may not seem like a large sample, but it has enough statistical power to make a false positive unlikely, which should give us more confidence in the result. Given the field’s history, however, some caution is necessary. “We need more studies to replicate these findings,” says Wu. He would also like to see more brain imaging experiments showing the effects of these chemicals on neural activity.
How would humans sense pheromones?
We don’t know for certain whether we even have a working vomeronasal organ (VMO), which is a part of the olfactory system responsible for sensing and processing pheromones in animals. The VMO has been documented in many animals, but in humans, it isn’t clear whether a rudimentary version can communicate directly with the brain through olfactory sensory neurons. There is, however, some evidence that may have connections with underlying capillaries, which could be used . If proved true, the researchers claim it would be the first evidence of an alternative use of the VMO and could account for potential pheromone effects on human behaviour despite the absence of any sensory neurons.
For now, the jury is still out on these putative sexual pheromones. “We need more rigorous research,” says at the University of Stirling, UK. He is interested in investigating other forms of chemosensory signalling, describing our focus on sexual pheromones as a false trail. Roberts hopes to investigate whether mothers produce a chemical that helps babies find lactating breasts, for instance – which could have been far more important to the survival of our species, he says.
Whether or not pheromones exist and influence behaviour, it would seem unwise to abandon your soaps and deodorants just yet. The malodorous miasma of stale sweat will speak volumes about your personal hygiene – and that’s unlikely to send many pulses racing.
