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A RECENT PODCAST by CrowdScience, BBC World Service, June 28, 2021, was devoted to our sense of smell.

Here are tidbits gleaned from Anand Jagatia’s CrowdScience olfactory podcast, together with my Internet sleuthing. 

What Smells? What Doesn’t? Jagatia describes that an odor is generated by hundreds of different volatile molecules. Most things have an odor, even if barely perceptible. Some things don’t: Sugar, for example, is composed of non-volatile crystals; it has no vapor pressure to release molecules. 

The perception of odors can be subjective, associated with pleasant or unpleasant memories. In fact, our sense of smell is likely the most subjective of the five. 

Human Olfactory Hard- and Software. Our noses contain olfactory receptors, with proteins that are coded in our genes. Their inputs are sent to the brain’s olfactory bulb, where it initiates reaction of the brain’s neurons. Wikipedia says that the average human can distinguish more than one trillion unique odors. 

The Lady and the Unicorn, Flemish tapestry, 1484–1500. Five of the tapestry’s six scenes depict the five senses; this one, smell.

Can You Smell This Now? Andreas Keller is an olfactory  specialist at Rockefeller University. He explains that because there is genetic diversity among humans, likewise there’s diversity in perceptions of smells. 

For example, sulfur-containing molecules in asparagus cause a characteristic urine smell after eating this vegetable. Some people easily identify this odor; others aren’t sensitive to it.

A Stink With a Purpose. Eli Biondi is supervisor of the Princess of Wales Conservatory, Royal Botanic Gardens, Kew. She introduces Anand Jagatia to titan arum, Amorphophallus titanum, aka the corpse flower. This plant blooms for only two days every two years, which is quite enough for most people who have smelled it. 

A titan arum in bloom at the New York Botanical Garden, June 27, 2018. Image by Sailing moose from Wikipedia.

There’s good reason for the plant’s obnoxious odor: It evolved to be pollinated by carrion flies.  

Agreement About Titan Arum—and Others. Noam Sobel is a professor of neurobiology at the Weizmann Institute of Science in Rehovot, Israel. He says there’s general agreement about most scents. Given 1000 molecules, say, people will disagree on only 100 of the smells.

A Teenage Tidbit. Jagatia says, “…for most of us, smell is probably the sense we take most for granted…. A recent study of teenagers found over half of them would rather lose their sense of smell than their mobile phones.” 

Olfactory Matters and Covid. Alas, Jagatia notes, “One of the symptoms of Covid-19 infection is a loss or distortion of your sense of smell and taste.” For some, this has lasted for months after Covid recovery and may call for smell retraining to reinforce the brain’s association with particular odors. 

Image from

Professor Carl Philpott of Norwich Medical School says, “The current working theory around the damage it causes is that the virus is infecting the supporting cells around the smell receptors in the lining at the top of your nose. In effect, it’s squeezing the receptor neurons and making them ineffective.”  

Summary. Anand Jagatia says that without smell, “life seems less vivid. You can’t smell your loved ones, or fish and chips for that matter. And so while smell is quite an underrated sense, it’s really quite a precious one.” ds

© Dennis Simanaitis,, 2021 

2 comments on “OLFACTORY MATTERS

  1. Jack Albrecht
    July 2, 2021

    “Wikipedia says that the average human can distinguish more than one trillion unique odors.” The rest of that article says that roughly 90% of those trillion unique odors can be identified in a crowded European elevator in high summer.

    • simanaitissays
      July 2, 2021

      Er… Thanks for this tidbit, Jack. And let us be thankful too for HVAC.

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