The vomeronasal organ is a hidden sensory system that detects pheromones and chemical signals.

Nature · Published 29 September 2026 Swipe more like this →

In short: Beyond our standard sense of smell lies a specialized, tubular structure called the vomeronasal organ. Found in many tetrapods, this auxiliary system bypasses the main olfactory bulb to send signals directly to the hypothalamus, influencing critical behaviors like mating, aggression, and social recognition through the detection of non-volatile chemical cues.

The vomeronasal organ, also known as Jacobson's organ, is a paired structure located within the nasal septum. First identified by Frederik Ruysch before 1732 and later by Ludwig Jacobson in 1813, it functions as a dedicated chemosensory system. Unlike the main olfactory system, which processes airborne odors, this organ is primarily tuned to detect non-volatile organic compounds, including pheromones, through direct physical contact or specialized transport mechanisms.

The mechanism relies on a unique accessory olfactory system. Sensory neurons within the organ express specific G protein-coupled receptors—categorized as V1R, V2R, and FPR families—that trigger distinct signaling pathways. When activated, these neurons send signals via cranial nerve zero to the accessory olfactory bulb, which then communicates with the amygdala and the hypothalamus. This direct neural highway to the hypothalamus explains why these chemical cues are so potent in regulating reproductive physiology, body temperature, and complex social interactions in species ranging from snakes and lizards to cats and elephants.

While the organ is well-developed in many vertebrates, its status in humans remains a subject of intense scientific debate. Some researchers have identified structures in cadavers and living patients, with one 2016 study finding evidence of the organ in roughly 27% of a Bulgarian population sample. However, microanatomical investigations have failed to find active sensory neurons or the necessary neural connections to the brain in adults. Furthermore, the essential genes required for its function have become pseudogenes in humans. Consequently, most experts remain skeptical that humans possess a functional vomeronasal system, suggesting that while the anatomical remnants may persist, the biological capacity for vomerolfaction has likely been lost.

The organ's importance in the animal kingdom is undeniable. From the flehmen response in ungulates to the nose-tapping behavior of salamanders, animals have evolved diverse strategies to deliver chemical stimuli to the organ's lumen. Whether identifying predators, avoiding sick peers, or tracking prey, this system provides a sophisticated, honest signal of an individual's physiological state, operating entirely outside the realm of conventional olfaction.

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