Pheromones have long been credited (or blamed) for our behavioral choices, most notably our choice of sexual partners. The idea that we could base such a seemingly personal choice on a unconscious chemical signal is fascinating but, is it real?
The answer is probably not - despite it being a widely held belief that humans make pheromones that affect our behavior - there is no scientific evidence to support that this is the case. But, it is still a question that garners much attention. In fact, Science magazine's special 125th anniversary issue, included the question “Do pheromones influence human behavior?” on the list of 100 of the most interesting questions still remaining to be solved.
Despite the lack of evidence, the production of pheromones is widely regarded as true, mainly due to large amounts of anecdotal evidence. As any woman who ever lived in the dorms can tell you, it really does seem as though women’s menstrual cycles synchronize when large groups of women live together. This is termed "the dormitory effect" or “the McClintock effect” after the head researcher who performed a study to analyze the timing of college students cycles at Wellesley College. Although not well reported, major flaws in this study have since debunked this idea entirely, but the word has not reached the public and people still believe this effect to be true.
One of the reasons why the presence of human pheromones is easily assumed is because other animals use them all of the time. In many organisms, pheromones play a key role in their social behaviors. Insects and worms, for example, use pheromones to communicate everything from mating to important social behaviors such as aggregation (coming together in a group.) And, pheromones have been identified in mammals with much of the research being done in mice. However, we cannot simply extrapolate that to humans.
One area that adds to the confusion is that a smell does not equal a pheromone and a pheromone does not equal a smell. Pheromones, for any species, are defined as chemical signals. To peel back the layers even more, even if pheromones were identified in humans, we would also need to understand what senses them.
In order to really understand the complexity of pheromones in an animals, there are three parts to understand. The signal (pheromone,) the receptors on which it acts, and the behavioral response elicited.
Mammals that are known to use pheromones detect them through receptors found in the vomeronasal organ (VNO) - a part of the olfactory (smell) system. However, scientists agree that the VNO in humans is vestigial - a non-functional remnant of an organ that may have been used once but is no longer functioning.
The key to the answer of human pheromones may lie not in our choices of sexual partners, but rather in sleeping babies. Perhaps the most tantalizing evidence for the presence of pheromones lies in the experiments done that stimulate a sleeping baby to start sucking and searching for a nipple when the secretion from a lactating human mother’s areola skin gland (see figure below) is placed below the nose. A newborn's responses are inherently innate, and the response to a substance indicates the presence of a potential communication signal.
So, the questions surrounding the presence of pheromones in humans remain. And, although there is a possibility that we use them, it will be difficult to uncouple their role from the rest of our incredibly complex social mechanisms. We have so many other ways to get our messages across, perhaps, even if we did use pheromones at one time, they may not be superceded by conversation, body language..... and emojis.