In most textbooks of physiology sexuality is put at the end of the book. Olfaction comes somewhat sooner, but is often near the end. As a consequence it is rarely given much importance by students. Every fifteen year old feels that he, or she knows all there is to know about sex. Yet it’s amazingly how much of this knowledge we “forget”as we pass into our twenties. Understanding sexual attraction requires some understanding of our sense of smell and how odors, as signals, works into the whole biological system.

Olfaction comes from the Latin word olfacere, meaning, to smell. It is a chemical sense, one of the most primitive of all communication mechanisms in biology, but a thread that runs through all of neurobiology, as well as biology in general.

Chemical sensing must have arisen as a means of detecting environmental conditions in the fluid matrix that spawned life.  Early soluble foodstuff was detected by chemical sense. As time progressed, upon leaving the sea the need to detect airborne signals, whether food, or enemy was required. This is the origin of the pheromone story.

There are four chemical senses in complex organisms: common chemical, internal chemicals, taste and smell. The sense of smell, or olfaction, relates to the type of pheromone that is the subject of this summary. Olfaction being a chemical sense requires receptors, a means of transporting the message to the brain, a means of identifying the signal and a means of reacting to the signal.