How Powerful are Pheromones?

It depends on who you ask.

If bees or ants-or any one of more than 1500 species of insects-could talk, they'd tell you that the chemical message of pheromones is absolutely irresistible. Insects do exactly what the scent signal tells them to, because, in insects, pheromones are the sole basis for many kinds of social behavior.

For instance, worker bees are powerless against the pheromones of queen bees. Ants follow each other, single file, to food sources because they're following a chemical trail laid by another ant. Some flying insects-moths, beetles, and flies-use pheromones to keep other insects away when laying their eggs so their offspring have less competition for scarce resources. They can signal alarm among aphids, and honeybees use pheromones to incite their nest mates to attack intruders. Male moths attract females with pheromones. One researcher who spilled male moth pheromones on his clothing had to beat the female moths off with a stick, so to speak.

Small amounts of pheromones can be extremely effective in insects. For instance, thirty molecules can trigger a response-in other cockroaches. And one female sawfly in a cage attracted more than 2,000 males a day. Insect pheromones are so powerful because insects lack other sensory input and because the behavior of insects isn't very complex. There are only so many ways to wiggle your antennae.

In animals, pheromones also trigger a variety of social behaviors related to defense and alarm, foraging for food, nest creation, and reproduction. But, in animals and especially in mammals, communication occurs through a combination of chemical, visual, and auditory signals-which makes it more challenging to sort out the relative impact of each type.

However, researchers agree that pheromones play the primary role in sexual behavior in all species. In all mammals, for instance, they cause changes in female hormones that affect pregnancy, the onset of puberty, the timing of female fertility cycles, and reproductive behavior. Humans have become quite skilled at manipulating animal pheromones, because pheromones make managing the reproduction of domestic animals easier. In pigs, cows, and sheep, they're used to speed up the timing of sexual maturity and synchronize fertility cycles, rendering commercial breeding programs more predictable and more profitable.

In humans, communication between males and females is even more complicated. In addition to visual and auditory signals-your appearance and the sound of your voice-humans add verbal signals into the mix of messages that result in sexual attraction.

Much of the inaccurate hype about the power of human male pheromones comes from equating them to insect pheromones: a sensory tractor beam that leaves women no choice but to be drawn inexorably toward you. While this is an accurate way of thinking about the sexual behavior of female moths, it's only true of female humans if they have no other sources of sensory input.

Instead, it's more accurate to consider pheromones as one of a complex set of sexual signals. Along with auditory, visual, and verbal clues, their chemical message sends important information to women. Male pheromones are a powerful part of the whole package of sexual attraction.