Pheromone

When you watch ants march in a line, it looks as if an invisible road has been laid out for them. And in a way it has. When an ant finds tasty food, it brushes the tip of its abdomen along the ground and leaves a guiding signal. Other ants pick up this chemical with their antennae and follow it straight to the food.

The power of a signal spreading through the air is beyond what you might imagine. The attractant that a female silkworm moth gives off (bombykol) was the first pheromone whose chemical structure was worked out. A male reacts so sensitively that he can detect just a few drifting molecules and flutter his wings toward the female. Some moths, like the spongy moth, can even call males from far away.

So wild animals use chemical molecules, not sight or shouting, to announce where food is, find mates, and sound the alarm for the whole group to run when an enemy shows up.

The names sound alike, so it is easy to mix pheromones up with the hormones inside your body. But they work on completely different stages. A hormone travels through your own blood and sends signals to your own cells. A pheromone, on the other hand, is released outside the body and delivers a message to another individual of the same species.

For example, insulin, the hormone that controls blood sugar, works quietly only inside your body. A queen bee's pheromone, by contrast, spreads through the whole hive. It keeps worker bees from laying eggs on their own and holds the order of the hive together.

Because of this difference, before the name "pheromone" existed, some people suggested calling it an "ectohormone," meaning a hormone that works outside the body. If hormones are the regulators inside your body, pheromones are the chemical language that regulates groups and societies.

You can easily find ads for "pheromone perfume" that promises to win over the person you like. But modern science has not clearly proven that humans have any pheromone that acts on us in a definite way. Even the candidate chemicals have not shown clearly repeatable effects in strict experiments.

Animals have a special sensory organ inside the nose called the vomeronasal organ (Jacobson's organ), which is dedicated to reading faint chemical signals in the air. In humans, though, the nerve connections of this organ have shrunk over evolution, so only a trace of it is left.

Of course, people can still faintly sense closeness or stress in each other through sweat or body odor. But there is no magic pheromone, like those in insects, that controls someone's mind or makes them fall in love with one smell alone.