What Will It Take To Find a Human Pheromone?

In 1991, at a conference sponsored by a fragrance company called the Erox Corporation, two University of Utah scientists presented research on a tantalizing pair of chemical compounds provided by the company. They reported that in a few dozen human volunteers, the molecules androstadienone and estratetraenol activated the vomeronasal organ (VNO)an olfactory organ that senses pheromones in many animalsin a sex-specific manner. The company patented these molecules as putative human pheromones. About ten years later, University of Chicago biopsychologist Martha K. McClintock and a colleague tested the molecules’ ability to affect the emotional states of men and women. The results, when published in 2000, did not support Erox’s claim: “It is premature to call these steroids human pheromones”, the authors concluded. But the paper brought the compounds to the attention of the scientific community. The human body naturally produces androstadienone and estratetraenol, but the compounds’, activity as pheromonessubstances produced and emitted by one individual of a species as signals affecting the behavior or physiology of another individual of the same specieshas never been rigorously demonstrated. Also, most researchers today agree that the VNO in humans, located just behind the nasal septum, is vestigial, an organ that’s no longer of use to today’s Homo sapiens. Even so, these molecules pop up in studies to this day. Tristram Wyatt, a zoologist at the University of Oxford, has tracked every mention of them in the scientific literature, following their trail either to McClintock’s 2000 paper or the 1991 symposium paper in which they were first presented. “It’s as if the company just plucked these molecules from the air”, Wyatt says. “And people simply took them on trust, so the idea of doing proper chemistry and experiments was short circuited.” Wyatt and other researchers have long tried to address a thorny question: Do human pheromones actually exist? Despite more than half a century of vigorous debate on the topic, there’s still no answer in sight. Indirect evidence suggests they might. For Wyatt, one strong indicator is that humans develop a permanently strong body odor during puberty; it’s at least possible that such odors act as chemical signals, as they do in some other sexually mature mammals at breeding times. The fact that other mammals have pheromones suggests that we may, too. Knowing either way would shed light on this primal and poorly understood communication system. To date, though, no actual molecules that serve as human pheromones have ever been identifiedin part because molecules falsely called pheromones diverted the search, but also because identifying the molecular basis of human behaviors is exceedingly complicated. A close look at the history of research on pheromones in other mammals reveals some of the challenges in the search and why settling the question will be no easy matter.