Sense of Smell

In the Science and Faith column of the Catholic Peace Weekly, we find some interesting insights into the sense of smell. One of the five senses, and often considered the weakest and least important.

This year, the rainy season has come, and we carry an umbrella because we don’t know when it will rain. When rain starts to fall from a cloudy sky, we see the rain with our eyes and hear the sound of the rain with our ears. And sometimes, we feel the rain not with our eyes or ears but with the smell that enters our nose. It smells like grass or the smell of the earth, and that is the smell of rain. 

This smell that comes when it rains is not the smell that comes from the rainwater itself. When raindrops fall on the soil, the oil components produced by plants are dispersed into the air in the form of aerosols (small water droplets suspended in the air) along with the raindrops. These aerosols contain chemicals produced by bacteria in the soil, creating a distinctive, earthy smell similar to the scent of the soil itself. Scientists call this rainy smell petrichor.

Although people can sense rain with their senses, such as their eyes (sight), ears (hearing), and nose (smell), in the past, the sense of smell was looked down upon more than sight or hearing. Plato believed that the world of ideas could be accessed through the senses of sight and hearing, so he considered the sense of smell unimportant. His disciple Aristotle, who valued the senses, also said that the sense of smell in humans was inferior to other senses. Even Immanuel Kant considered the sense of smell to be the “most superficial and unnecessary sense,” and it has been underestimated.

In 1991, Richard Axel and Linda Buck of Columbia University in the United States discovered a group of olfactory genes, comprising approximately 1,000 genes, which led to a deeper understanding of the human olfactory perception mechanism and marked the beginning of the solution to the mystery of olfaction, the most complex of the human senses. They were awarded the 2004 Nobel Prize in Physiology— Medicine in recognition of this achievement. 

In addition, scientists in the fields of neurology and brain science have discovered that olfaction, unlike other senses, not only accepts stimulus information analytically, but also emotionally. Olfactory information is sent to the limbic system of the brain, which includes parts responsible for not only olfaction but also human memory and emotions. Therefore, if a particular smell is associated with a person or event, when you have that smell again, the memory of that time comes to mind, and emotions are revived. In other words, olfaction plays a role in memory. This phenomenon is known as the ‘Proust effect’, originating from the French novelist Marcel Proust’s novel In Search of Lost Time, where he recalled memories from his childhood while smelling a madeleine soaked in black tea.

Fragrance comes not only from flowers or food, but also from people. It is not a chemical substance that stimulates the brain through the olfactory cells of the nose, but a fragrance of life that is remembered in our hearts through the words, actions, facial expressions, and personality of that person. To the columnist, Cardinal Kim Soo-hwan and Monk Beopjeong, a Buddhist born in South  Jeolla Province, South Korea, who died in 2010 (77 years old), are two persons remembered with such fragrances. The deep and resonant fragrances they left behind in the world will be remembered by the columnist for a long time. He wants to live a fragrant life like them.

But what is my fragrance, what is your fragrance right now? Are we emitting an attractive fragrance, a humane scent that makes people smile and miss what they remember just thinking about it? I must now examine myself to see what kind of fragrance I will be remembered by others. “We are the fragrance of Christ, rising to God.” (2 Corinthians 2:15)