Do pheromones influence human behavior?

Abstract

Social communication via airborne chemicals is ubiquitous in the animal kingdom. Such active substances were designated as “pheromones” by Karlson and Luscher in 1959. As specified by the original definition, pheromones refer to substances that are secreted to the outside by an individual and received by a second individual of the same species, in which they release a specific reaction, for example, a definite behavior or a developmental process. Over the past fifty years, a number of pheromones with distinct functions have been identified in invertebrates as well as in mammals. In the case of mammalian pheromones, recent findings reveal that some of them are processed in the main olfactory system, contrary to the traditional belief that mammalian pheromones are exclusively encoded by the vomeronasal organ and act through the accessory olfactory system. Humans are thought as the most highly scented ape of all in terms of numbers and sizes of sebaceous and apocrine glands. The search for human pheromones, however, has met with less success. The challenges lie in several aspects: (i) Human behavior is highly complex and multifaceted; (ii) Human secretions contain an enormous number of components with changeable concentrations; and (iii) Unlike most mammals, humans do not have a functional accessory olfactory system and rely solely on the main olfactory system to process airborne chemical compounds. Nonetheless, humans possess at least one functional V1r-like gene, a counterpart of the V1r genes that express pheromone receptors in rodents. Moreover, there has been accumulating evidence indicating that human body odors exert a range of pheromone-like effects on odor recipients. These include triggering innate behavioral responses, modulating endocrine levels, signaling social information, and affecting moods and cognition, in line with the roles of releaser, primer, signaler, and modulator pheromones, respectively. In particular, two human steroids—androsta-4,16,- dien-3-one, the most prominent androstene present in male semen, in axillary hair, and on axillary skin surface, and estra-1,3,5(10),16-tetraen-3-ol, first identified in female urine, are considered “putative human sex pheromones”. They have been shown to convey sexual information, modulate mood state, alter autonomic responses, and activate the hypothalamus in manners contingent on the recipient’s gender and sexual orientation yet below his or her awareness. The findings to date have furthered our understandings of human chemosignaling and interpersonal communication, and have paved the way for future investigations of human pheromones. Identifying the mechanisms underlying the release and detection of human pheromones and molecularly characterizing them represent important directions for future work.