Pheromones

For decades, researchers have known that animals secrete and detect chemical messengers known as pheromones. Originally discovered in insects, pheromones are best known for their role in attracting members of the opposite sex. In the 1930s, investigators reported that female moths were able to excite males even when the males could not see or hear them. The males apparently detected the “smell” with extraordinarily sensitive antennae. Fragrance concentrations of less than one 300-millionth of an ounce could stimulate millions of moths.

Subsequent research has indicated that pheromones can provide animals with information about each other’s identity and produce hormonal changes that stimulate ovulation, promote or inhibit sexual maturation, precipitate abortion, and even stop aggression. Most mammals seem to detect pheromones through their olfactory system as weel as the vomeronasal organ (VNO), a proposed organ located in the nose, which detects pheromones and communicates information about them to the hypothalamus, where certain pheromones might affect such things as an infant’s recognition of its mother or an adult’s choice of mates.

2 types of pheromones identified: Primer pheromones produce changes in the endocrine system of the receiving animals. – For example, young female mice exposed to chemical signals of adult males mature more quickly. Release pheromones elicit specific behavior patterns. – Male hamsters are attracted by a secretion females release in greatest amount just before they ovulate.

Are there human pheromones? The most promising evidence comes from researchers investigating the menstrual “synchrony” in women who live or work together. Nearly 30 years ago, Martha McClintock, than a Wellesley College undergraduate, noticed that women in her dormitory often developed remarkable similar menstrual patterns. For other species, this synchrony has survival value. “When you see others successfully rearing young, it means it’s a good time for you too.”

Now a psychologist at the University of Chicago, McClintock and colleague Kathleen Stern recruited a group of 29 women and asked nine of them to wear pads under their arms for several hours, either before or just after ovulation. When the pads were then wiped under the noses of the other women, the results were startling: Smelling preovulation pads shortened their menstrual cycles by as many as 14 days, while ovulation phase pads increased cycles by as many as 12 days.

McClintock is continuing her research with an eye on possible applications. Pheromone treatments designed to regulate ovulation could serve as fertility enhancers for couples who want to conceive and as contraceptives for those who don’t.

More recently, McClintock’s research team asked women to sniff boxes containing a single T-shirt. Each T-shirt was worn by one of six men of diverse backgrounds. No one man emerged as most pleasant- smelling. Rather, the women preferred men who had immune-system genes similar to their own. The analysis showed that these men possessed a gene that had been inherited from the women’s fathers.