If you can smell the person sitting next to you, that’s not usually a good thing. Unless of course, it’s somebody that you find attractive. Then suddenly the secretions of the human body don’t smell quite so bad, do they?
Studies of pheromones have investigated how they work in the human world, and evidence of this is all over the World Wide Web. A simple search of “pheromones” brings up all sorts of products that are “scientifically proven” to increase your attractiveness to the opposite sex. These claims, however, are not supported by the real scientific literature and to date, no magical chemical attractant for humans has been identified.
In the natural world, there is a basic understanding of how pheromones work, especially in insects, but scientists are discovering that there are more complexities than initially thought, especially as you enter the world of vertebrates. In insects such as ants, in which pheromones have been studied at length, two categories of pheromones have been identified. For problems that require an immediate response, like an alarm call, ants excrete pheromones that have a “releaser effect”. A releaser effect results in an immediate change in behavior. In other cases, the pheromone creates a “primer effect,” which essentially primes the receiver for a specific action. In insects, these are typically related to mating behaviors.
While these pheromone-induced behaviors may sound like fairly simple cause-and-effect situations, in reality, there is a complex set of chemicals involved that induce varied and intricate responses in other individuals. For example, in fruit flies, the male emits a specific pheromone as part of the courtship ritual. The chemical is an aphrodisiac for females, but it causes male fruit flies to become aggressive, and any of the chemical left on a female from a previous male will repel future suitors. This interaction only hints at the complexity of pheromone responses in nature, opening the door just a crack to reveal a world that is completely invisible to human beings.
Studies of pheromones in mammals reveal even more uncertainties. The neural pathways identified in simpler animals, like the fruit fly, are complicated by the highly evolved nervous system, and the pheromone responses in mammals are even more difficult to decode and understand. Mammalian responses to pheromones typically induce the “primer effects” described earlier, but these also appear to be dependent upon experience and the environment. For example, female mice respond differently to a compound found in the urine of male mice depending on whether they are in estrus, or have just given birth. Responses also varied depending on whether the female mice were living with other females or in a co-ed group.
On the range of animal communication, humans appear to have a fairly highly developed system, with over 6,000 different languages, music, perfumes and, of course, cell phones. But as it turns out, the highway of scents and smells available to the animal world is largely invisible to us. We might notice strong scents, like rotting fruit or carrion, but the more subtle smells just wash over us, influencing us subconsciously through our primal senses. Just imagining how we might perceive the planet if we could tap into this world of smells on a more conscious level opens up a whole new level of possibilities. And while this level of sensory perception might be impossible, it broadens our horizons a little bit to recognize that there is a whole lot that happens right under our noses that we never notice.
Jaymee Squires is the director of graduate studies at Walking Mountains Science Center. She is busy these days trying to soak in as many of the sights and smells of the springtime before it turns into the lazy days of summer.
Just imagining how we might perceive the planet if we could tap into this world of smells on a more conscious level opens up a whole new level of possibilities.