The human nose is miraculous. It is a complex organ of smell. In fact, one percent of human genes are devoted to olfaction; smell was central to our evolution over the past seven million years.

The main role of smell is to protect humans from decaying foods and poisons. Foods that are indigestible tend to smell woody or musky and are made up of large molecules. Edible foods, on the other hand, have low molecular weights, which can be processed by our digestive enzymes.

The primary role of scent is not about sex.

Interestingly, the exact way the nose works, that is, the way we smell is not fully understood. Scientists know that there are receptor neurons continually shooting axons or neutral connecting wires up to the olfactory bulb — the brain’s control center for smell.

There are at least 1,000 different receptors in the human nose that are able to distinguish between some 10,000 different molecules.

There are 112 known types of atoms. The human nose can detect most scent molecules because they are made up of carbon, hydrogen, oxygen, nitrogen and sulfur.

Humans sneeze in order to shed viruses and things trying to get inside us.

When we breathe through our nose, we tend to breathe through only one side of it for a while, then for a while through the other side. The erectile tissue lining our nasal cavity only works one passage at a time. This is called the nasal cycle.

Smell information from the right side of the nasal passage is sent to the left side of the brain and vice versa. Incidentally, when you breathe from the left nasal passage your verbal skills increase significantly.

Women have a better sense of smell than men and it lasts longer. As humans age we experience a loss of smell. Epileptics show considerable smell loss. And loss of smell is one of the first symptoms of the onset of Parkinson’s disease.

The loss of the sense of smell is known as anosmic.

An atom is made up of a cloud of electrons frenetically orbiting a hard core of protons and neutrons. All molecules pulse with vibrations. Those vibrations are the result of the electron string holding them together. In essence, molecules act like a musical instrument. Each one emits its own unique set of vibration notes.

Until about 10 years ago, scientists believed that the human nose was able to discern the scent of a molecule based solely from its shape.

In the late 1990s a bio-physicist named Dr. Luca Turin put forward a theory on the way the human nose functions — it caused quite a buzz in the science community.

Turin used his obsession with perfume to redefine how the human nose functioned. He devised a scale of molecular vibration ranging between 0 and 4,000, or the number of times an electron bounced back and forth as it bonded one atom to another. Within just a few vibrations a molecule can either smell of shoe leather or rose tea or shrimp shells.

Turin proposed that as the molecules entered the nose, electrons are met by microscopic electrical protein receptors, embedded in nasal flesh, and that the receptor holds the molecule and reads its vibration, not its shape.

Years of experimentation, tens of thousands of smells later and about a decade since the theory was first presented, it’s finally starting to be accepted.

The scent of Tide laundry detergent, Clorox bleach, Calvin Klein, Channel, L’Oréal and Miyake all come from five huge corporations: International Flavors and Fragrances, Givaudan Roure, Firmenich, Takasago, and Symrise. It is a $25 billion per year industry.

Armies of organic chemists create between 500 and 2,000 different new molecules at each company per year. About 20 interesting and strong molecules per company are used each year for a host of new products.

To me there is nothing as remarkable as natural scents of wild forests. My favorite pungent scent comes from the peppermint leaves of colossal montane Eucalyptus delegatensis or woollybutts of the Australian Victorian Alps.


Dr. Reese Halter is a conservation biologist, public speaker and founder of the international conservation institute Global Forest Science. His most recent book is “The Incomparable Honeybee and the Economics of Pollination,” Rocky Mountain Books. He can be reached through

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