Some time ago, women in solitude cried into vials. Their tears were special. They held a chemical whisper that could rob desire from men….
Though this sounds like some kind of fairy tale, it’s in fact the description of a fascinating and important experiment by Noam Sobel’s lab at the Weizmann Institute of Science in Israel. Using a combination of brain scanning and other testing, these researchers have shown that women’s tears contain a compound that covertly inhibits sexual desire in men.
Unlike many other major findings, the significance of this one can be grasped immediately: humans secrete pheromones that can affect another’s thoughts, brain, and biochemistry.
The term ‘pheromone’ was coined in 1959 by Peter Karlson and Martin Luscher to help organize their thinking about certain intriguing biomolecules reminiscent of hormones. Although studies of the potent, specific, and sometimes evocative effects of blood-borne hormones were well underway, these investigators were chasing a slightly different question. In a foundational paper, the two scientists speculated that hormone-like compounds might travel from one animal to another via bodily secretions. With such a signaling mechanism, they reasoned, one animal could “release a specific behavior” in another. A mere whiff or lick of another’s secreted message could prompt defense, pursuit, reproduction, or many other possible behaviors.
It was a far-reaching idea, and one that’s now backed by a wonderful variety of colorful examples. Nest-building ants, suckling rabbit pups, and mating elephants are all impelled by specific chemicals that trigger and modify innate behaviors.
But what about us? Are there any behaviorally meaningful signals in the bodily secretions we usually try to mask or scrub away? This has been a lively (if contentious) research question, and studying it has resulted in some intriguing reports of candidate human pheromones. Smelling a male sweat component, for example, can raise levels of the hormone cortisol in women, and other sweat-derived compounds may synchronize the menstrual cycles of women living in close proximity.