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The Nose Really Does Know, It Turns Out…

But we usually don’t notice. Our sense of smell may have declined in recent millennia but it is sharper than we think

Anthropologist Sarah Ives reflects on the experiences of people whose sense of smell fell victim to COVID-19:

Melissa, a New York–based podcaster, realized how crucial scent is for safety when she lost her sense of smell. “I kept burning stuff on the stove,” she says. “I’ve sent rotten turkey to school with my kid. I have thought, What if I end up dying because I can’t smell something dangerous, like knowing whether you are going to burn the house down? I’ve literally almost done it three times. There are flames, and I’m just sitting in the other room.”

Sarah Ives, “What the Anthropology of Smell Reveals About Humanity” at Sapiens (June 30, 2022)
Sick woman trying to sense smell of fresh tangerine orange, has symptoms of Covid-19, corona virus infection - loss of smell and taste, standing at home. One of the main signs of the disease.
A classic COVID system is loss of a sense of smell

Anosmia, the loss of a sense of smell, which affects up to 80 percent of COVID sufferers, is usually temporary but, however long it lasts, it is a health and safety issue. Science journalist Gaia Remerowski reports a similar experience:

One year, my dad came down with a terrible cold and a very high fever. As with many colds he’d had before, he lost his sense of smell. But this time, it didn’t come back.

By Christmas that year, we were all gathered in the kitchen as my dad cooked a big family dinner. My cousin, who was standing near the stove, said she smelled gas. It turned out one of the burners was no longer lit and gas was escaping quickly through the house. My dad, who had been at the stove the entire time, couldn’t smell it at all. – Office for Science and Society, 2021

Ives, author of Steeped in Heritage: The Racial Politics of South African Rooibos Tea (2017), notes that the human sense of smell is far more sensitive than we may think:

While many people can discriminate between several million colors and nearly half a million different auditory tones, we can smell more than a trillion odors.

Smell “has this infinite dimensionality,” says Matthew Cobb, an evolutionary neurobiologist at the University of Manchester. Yet smell remains distinctly enigmatic, he adds. “We understand how vision works, how hearing works, and more or less how taste works, how touch works, but not smell. We don’t know what the rules are.”

Sarah Ives, “What the Anthropology of Smell Reveals About Humanity” at Sapiens (June 30, 2022)
Dog looking for drugs in luggage storage

We do know that the human sense of smell is better than we used to think. Rutgers University-New Brunswick neuroscientist John McGann reports

“The fact is the sense of smell is just as good in humans as in other mammals, like rodents and dogs.” Humans can discriminate maybe one trillion different odors, he says, which is far more, than the claim by “folk wisdom and poorly sourced introductory psychology textbooks,” that insist humans could only detect about 10,000 different odors…

“Dogs may be better than humans at discriminating the urines on a fire hydrant and humans may be better than dogs at discriminating the odors of fine wine, but few such comparisons have actual experimental support,” McGann writes in Science.

The idea that humans don’t have the same sense of smell abilities as animals flourished over the years based on some genetic studies which discovered that rats and mice have genes for about 1000 different kinds of receptors that are activated by odors, compared to humans, who only have about 400.

Rutgers University, “The human sense of smell: It’s stronger than we think” at ScienceDaily (May 11, 2017) The paper requires a fee or subscription.

In direct comparisons, humans sometimes do better than other tested mammals, says Linköping University biologist Matthias Laska, who had studied the question for two decades:

Humans tested as generally more sensitive sniffers than monkeys and rats on a limited range of odors. In fact, humans detected certain scents at lower concentrations than the notoriously top-notch nostrils of mice and pigs.

Humans even beat the indomitable dog for at least a handful of scents. These include aromas produced by plants, a logical evolutionary advantage for our ancestors seeking fruits. The majority of the odors in which dogs bested us were the fatty acids, compounds associated with their own meaty prey. “Odors that are not relevant for you, you are usually not good at [smelling],” Laska says.

Marta Zaraska, “The Sense of Smell in Humans is More Powerful Than We Think” at Discover Magazine (October 10, 2017)

One factor we might be overlooking is that humans derive a great deal of information from symbolic language as well as from our senses. When a dog sees a visitor who is acting suspiciously, he may sniff him out and study his movements to determine if he poses a threat. A human can ask around about the man’s reputation — and maybe find out if he has a criminal record… Perhaps, over time, we have tended to discount our senses as “subjective” in comparison with, say, a rap sheet.

At any rate, our sense of smell is both better and more important to us than we may sometimes think.

You may also wish to read: Has the human sense of smell declined in recent millennia? Researchers found that people with “ancestral” genes perceived various odors as more intense. To be sure that our sense of smell has genetically declined, we would first need to see whether concerted efforts to improve it were successful.

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The Nose Really Does Know, It Turns Out…