Pheromones are chemical compounds that act as a form of invisible communication between members of a species. Insects, birds and mammals have all been found to release pheromones. These transmit information about an individual, such as their sex, their fertility, health, and even social status to other individuals, who detect the information via smell.
What's the buzz: Pheromones are a form of invisible communication within a species, says Professor Michael Gillings.
Contrary to popular belief, however, there is no really good evidence that human pheromones exist, or that they play a part in sexual attraction and reproduction – but more on that later.
In the animal world, some pheromones have immediate effects. For instance, virtually all insects use them to communicate about reproduction. The best examples come from moths. Female silkworm moths emit a pheromone called bombykol. A single molecule of female moth pheromone can be detected at enormous distances by a male moth, which then follows a trail of the molecules over many kilometres, all the way to the female.
Other pheromones may act more slowly. Male mice, for example, produce the pheromone alpha farnesene, which is reported to speed up the puberty of juvenile female mice that are exposed to it, with the result they become fertile more quickly. This same compound also functions as an alarm pheromone in termites.
Bees and wasps also release alarm pheromones when attacked or put under stress, thereby warning others of their species that something bad is happening. Pheromones are in play when dogs, wolves and many other mammals urinate to mark their territory. As well as alerting a strange animal that it is on someone else’s patch, they are giving information about their health and dominance status to the intruder, as well as the size of the population that’s occupying the territory.
On the human front, it is possible, but unproven, that pheromones play a part in mate choice and attraction; the evidence flips back and forth, with some researchers rejecting the very existence of human pheromones. There are two famous kinds of study: observations that menstrual cycles of co-habiting women eventually synchronise, supposedly driven by pheromone cues, and evidence that women can detect the genetic diversity of immune-response genes in men, again presumably by using pheromone cues. However, pheromone detection in mammals is done by the vomeronasal organ inside the nose, and there is little evidence that this organ is actually active in adult humans.
So, if you’re tempted by the body sprays, perfumes and pheromone wipes that marketers say will attract the opposite sex, just remember there is no guarantee you will be getting what you paid for.