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Airdate: May 23, 2000
Scientist: Dr. Stuart Firestein

Smell: How

Smell: How
Human beings have more genes devoted to the sense of smell than to vision. A leading expert explains this and other little-known facts about the sense of smell.

The month of May, with the fragrance of spring flowers in the air, is a time when we notice what we're smelling. But often, the human sense of smell gets overlooked, so to speak. Scientists are now giving more credit to the powers of the human nose. I'm Jim Metzner and this is the Pulse of the Planet, presented by DuPont. Stuart Firestein of Columbia University is a leading expert on "olfaction", the scientific term for the sense of smell. He says that we have more genes related to smell than we have for virtually any other process.
"We know now from these human genome sequencing projects that we think the human genome has somewhere between eighty and a hundred thousand genes. A thousand of those genes, then, are devoted to olfaction. That's one percent of the entire genome devoted to your nose."
When the nerve cells in your nose perceive certain chemicals in the air, they send a message to your brain about what you're smelling. So smell, like taste, is a chemical reaction.
"But in fact the senses are quite different. Taste, by which we formally mean four primary tastes: salt, sour, bitter and sweet, work quite differently from the sense of smell. Now, there is something called flavor. Flavor is a little different. Flavor is a combination of the four primary tastes and odors as well. So you know if you have a cold or you lose your sense of smell, a great deal of the flavor world is gone. You can still taste the four primary tastes, but you no longer have a full sense of flavor. There are no primary odors in olfaction that are similar to that. What we have are many different kinds of chemical classes, all of which give these odors off."
More on what the nose knows, next time. Pulse of the Planet is presented by DuPont, bringing you the miracles of science, with additional support provided by the National Science Foundation. I'm Jim Metzner.