Andrew Miller: We take our olfactory system for granted but our sense of smell is a super power

Do you remember the one who wore that scent? When you catch that unmistakeable perfume or cologne from days gone by, do you still look up, to see if they are walking by? Does your heart beat harder, just for a minute? Whatever happened to them? We often take our olfactory system for granted, as it works under the radar. This most ancient of sensory systems connects the world and our memories like a magical, subconscious kaleidoscope. Our nose does not clamour for attention — not in the same way that our device-hungry eyes and ears do — but it is an essential environmental scanner. Even with headphones in and a screen reflecting blue on our too-close face, the smell of sizzling bacon will get through. Naphthalene, one of the active chemicals in mothballs, is a solid at room temperature that slowly ekes to gas, giving off insect-deterrent fumes for months, years and a life. They dissolve in wardrobes that used to open several times a day for outfit changes, but lately have fallen silent, dark and stagnant. Their powerful odour permeates cashmere cardigans and silk scarves now untouched, and hooks and eyes too small for failing fingers. As fat raindrops begin to splat on a warm humid evening, the petrichor rises into your nose and a combination of hot asphalt, bike tyres, and an almost-split tennis ball used for street cricket comes flooding back. The neighbourhood kids are yelling, the mozzies are biting and Mum is threatening to leave your unseasoned mince on toast to go cold. The pop of a cork begins a chain reaction — the splashing pour, the sight of a wave filling a clear glass and the first deep sniff of the bouquet. With training, some can distinguish impossible detail with their nose. Wine aficionados appropriate every adjective and metaphor, in an enthusiastic attempt to proselytise the experience for those of us who just drink what we like. “It has notes of rose, blackberry and saddlebags with various soft tannins.” “I’ll take your word for it — cheers!” we reply. The palate includes tastebuds, but the nose gives the finer information used to decode an unseen, unheard world of chemical knowledge. You may prefer the crack of a can and a stream of crowding bubbles making the perfect head in a tilted frosty glass. The hops and barley effervesce right up your nose. After we take that first best sip, exhaled breath floods all the volatile compounds through the upper nasal passages, where they dissolve in the moisture of the mucus membrane and bind with protein receptors on fine olfactory filaments. Our food experience is heavily infused with the complex aromas of thousands of chemicals — what is a good chef, if not a mad scientist? Their art is the curation of a sensory experience that leans heavily on what we smell, as well as textural feel and taste. Their little keys turn our olfactory neural locks just so, depending on chemical orientation. Like different Lego blocks, even a few simple carbon and hydrogen atoms can be constructed in many different volatile 3D patterns, and then mirrors of themselves. The signals ascend wispy-fine nerves through the cribriform plate of the skull to the olfactory bulbs, which are plugged directly into our primary sensory cortex. Smell is the only sense that is not regulated through our bossy, over-thinking thalamus. It is our most vulnerable brain with all its memories, in direct contact with the air. Those that lose their sense of smell through head injury, neurodegenerative disease or post-viral syndromes — including many now with long COVID — endure a profound disability. We are in the delivery room, there is antiseptic, and the warmth amplifies the unmistakeable fragrance of a fresh swaddled newborn baby — mewling and coddled at the breast of their tired mother — greasy vernix still adorning their crown. That baby smells like goodness, and we turn toward them.