Human Pheromone Myth

The idea that humans can subconsciously signal attraction or dominance through invisible chemical clouds is a staple of romance novels and cologne advertisements. We want to believe there is a secret biological channel that explains immediate chemistry between two people. However, rigorous biological studies challenge the existence of human pheromones. While animals definitely use these chemical signals, the evidence suggests humans rely on a completely different sensory system.

The Strict Definition of a Pheromone

To understand why the myth is crumbling, we must look at what a pheromone actually is. The term was coined in 1959 by Karlson and LĂĽscher. They defined it as a substance secreted by an animal that causes a specific, hardwired reaction in another individual of the same species.

The classic example is the silk moth (Bombyx mori). If a female releases the molecule bombykol, any male moth in range will immediately fly toward her. It is not a choice or a preference. It is a robotic, chemical reflex.

Tristram Wyatt, a zoologist at the University of Oxford, argues that humans misuse the word. We confuse “pheromones” with simply “smelling someone.” A pheromone must trigger a behavioral response that is innate and unavoidable. So far, no scientist has isolated a single human molecule that forces another human to mate or fight in the way bombykol controls moths.

The Failure of "Androstadienone" and "Estratetraenol"

For years, perfume companies and hopeful researchers focused on two specific steroid molecules:

  • Androstadienone: Found in male sweat and semen.
  • Estratetraenol: Found in female urine.

You can buy vials of these chemicals online, marketed as love potions. However, a landmark study published in Royal Society Open Science in 2017 dismantled the claims surrounding them.

Researchers at the University of Western Australia, led by Leigh Simmons, exposed participants to these two scents while asking them to rate the attractiveness of gender-neutral faces. The study involved strict double-blind controls. The results were conclusive: the chemicals had zero effect on how people perceived attractiveness. They did not increase perceived gender or desirability. This suggests that the two primary candidates for human pheromones are biologically insignificant regarding attraction.

The Missing Hardware: The Vomeronasal Organ

Another major blow to the pheromone theory is human anatomy. In mammals like mice, cats, and pigs, pheromones are detected by a specific piece of hardware called the vomeronasal organ, or VNO (also known as Jacobson’s organ).

The VNO is located inside the nose but is distinct from the regular sense of smell. It connects to the accessory olfactory bulb in the brain. Here is the problem for humans:

  1. No Connection: While human fetuses develop a VNO structure, it typically regresses before birth. In adults, it appears to be a vestigial pit with no nerve connection to the brain.
  2. Broken Genes: The genes responsible for the receptors in the VNO (specifically the TRP2 gene) are “pseudogenes” in humans. This means they are mutated and non-functional.

Without a working VNO or the genes to build the receptors, humans lack the biological machinery to process pheromones the way other mammals do.

Scent Signatures vs. Pheromones

Skeptics of the “myth” theory often point to the fact that body odor affects attraction. This is true, but it is not because of pheromones. It is because of the Major Histocompatibility Complex (MHC).

The MHC is a set of genes relevant to the immune system. A famous experiment led by Claus Wedekind in 1995 (often called the “Sweaty T-shirt Study”) showed that women preferred the smell of T-shirts worn by men with MHC genes different from their own.

This is a critical distinction:

  • Pheromone: A single molecule that triggers a universal robot-like response in everyone (e.g., “Attack” or “Mate”).
  • MHC Scent: A complex profile of odors that reveals individual genetic compatibility.

Richard Doty, the director of the Smell and Taste Center at the University of Pennsylvania and author of The Great Pheromone Myth, explains that mammals generally rely on learned, complex odors rather than simple chemical triggers. We smell the immune system and hygiene of a potential partner, but we are not being puppeted by a single molecule.

The Commercial Incentive

If the science is so shaky, why does the idea persist? The answer is largely financial. The global fragrance industry is worth billions of dollars. The promise that a spray containing synthetic androstenone can make a person irresistible is a powerful marketing tool.

Most “pheromone” products sold today are based on science from the 1970s that was heavily criticized for small sample sizes and lack of reproducibility. Modern rigor demands double-blind testing and large participant groups. Under these conditions, the magic molecules fail to perform.

Human attraction is complex. It involves sight, sound, memory, social context, and a general sense of smell. Reducing it to a single chemical signal ignores the complexity of human evolution. We traded the VNO for a massive visual cortex and complex decision-making abilities. We determine compatibility through conversation and observation, not just chemical reflexes.

Frequently Asked Questions

Do humans have a Vomeronasal Organ (VNO)? Most humans have a small pit in the nasal septum that looks like a VNO. However, it is considered vestigial. It lacks the sensory neurons and the connection to the brain required to transmit chemical signals.

Does menstrual synchronization prove pheromones exist? No. The “McClintock Effect” (1971), which claimed women living together synchronize their cycles via pheromones, has been debunked. Subsequent studies and statistical reviews found that any synchronization is likely due to chance or mathematical coincidence.

Are there any proven human pheromones? Currently, no chemical substance has been scientifically proven to meet the strict biological definition of a pheromone in humans. While we have distinct body odors, we have not identified a molecule that triggers a universal behavioral reflex.

Why do babies recognize their mothers by smell? This is learning, not pheromones. Infants learn their mother’s specific odor profile (amniotic fluid, breast milk, skin) rapidly after birth. This is an individual recognition process, similar to recognizing a face, rather than an innate reaction to a generic chemical.