Dogs have a higher number of olfactory receptors than humans but that doesn't necessarily mean they smell better. For instance, humans are more sensitive than dogs to amyl acetate, the main odorant in bananas. Credit: Pixabay.

Our sense of smell is just as good as rodents’ or dogs’

Dogs have a higher number of olfactory receptors than humans but that doesn't necessarily mean they smell better. For instance, humans are more sensitive than dogs to amyl acetate, the main odorant in bananas. Credit: Pixabay.

Dogs have a higher number of olfactory receptors than humans but that doesn’t necessarily mean they smell better. For instance, humans are more sensitive than dogs to amyl acetate, the main odorant in bananas. Credit: Pixabay.

Without smell, life would be dull and lame. But most people are under the impression that this is the least developed of our senses. John McGann, a neuroscientist at Rutgers University-New Brunswick, says that we shouldn’t underestimate human olfaction. The scientist recently published an extensive review of the published literature in the field so far and found no evidence that human smell is inferior to that of most mammals like rodents or dogs.

The truth about smell

According to McGann, the myth of poor human smell can be traced back to the writings of a 19th-century brain surgeon named Paul Broca who concluded the human olfactory bulb is much smaller than that of other animals. It follows that our sense of smell must be inferior too, an assertion that even influenced Sigmund Freud to say poor smell is one of the root causes that makes us susceptible to mental illness. At the same time, poor smell was seen as a hallmark of overall human superiority. It meant humans had free will since they didn’t have to rely so much on smell to survey like dogs, for instance.

“It has been a long cultural belief that in order to be a reasonable or rational person you could not be dominated by a sense of smell,” said McGann in a statement. “Smell was linked to earthly animalistic tendencies.”

Nevertheless, the idea that we smell rather poorly compared to other mammals has stuck on for ages and McGann insists it’s all a myth. For instance, McGan says the common claim that humans can only detect about 10,000 different odors is not rooted in reality. Instead, your typical human should be able to distinguish up to a trillion different odors. 

Far from nimble, the human olfactory system is comprised of a large number of neurons or at least similar in number to other mammals. Even if the olfactory bulb might be smaller than that of other mammals, proportionately speaking, there’s no evidence so far to suggest its size increases or decreases the sense of smell. Moreover, as the human brain evolved to grow larger, the olfactory bulb did not become smaller.

“We can detect and discriminate an extraordinary range of odors; we are more sensitive than rodents and dogs for some odors; we are capable of tracking odor trails; and our behavioral and affective states are influenced by our sense of smell,” McGann wrote in his paper published in Science.

“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,” he added.

‘The idea that human smell is impoverished compared to other mammals is a 19th-century myth’

John P. McGann, Associate Professor of Psychology at Rutgers University.

John P. McGann, Associate Professor of Psychology at Rutgers University.

McGann cautions in his review that the myth of poor human smell is still propagated by science papers published in the 21st century, not just obscure 19th-century writings. He cites works that found rats and mice have genes that code for some 1,000 different receptors that are activated by odors while humans only have about 400. Some have seen these findings as confirmation of poor human smell. But “it has been too easy to get caught up in numbers,” says McGann, because there’s a confirmation bias even among scientists that humans have a poor sense of smell. In reality, even 400 receptors is an “awful lot”. A recent study found cows have 2,000 such genes, which is far more than both dogs and mice have but no one is claiming cows can smell splendidly.

Perpetuating this myth can even be dangerous, McGann says. Smell significantly influences our behaviour, memories, and emotions. And if some patients seem to lose their ability to detect odors, that may be a cause of concern — something which physicians should be very mindful of instead of retreating into a ‘humans smell poorly anyway’ mindset.

“Some research suggests that losing the sense of smell may be the start of memory problems and diseases like Alzheimer’s and Parkinson’s,” says McGann. “One hope is that the medical world will begin to understand the importance of smell and that losing it is a big deal.”

2 thoughts on “Our sense of smell is just as good as rodents’ or dogs’

  1. Cassandra Kavanagh

    How can anyone say such a sweepingly broad statement that "our sense of smell is as good as rodents or dogs ?" and then fail to provide any significant evidence . I was once involved with a search for a toddler in a picnic area . Despite the fact he was wearing a soiled nappy not one of the 234 people who began the search were able to pick up the scent ? I don't notice human beings being used at the airport to sniff out concealed drugs or incendiary devices or tracking lost people in the wilderness or being able to detect cancer by smell ! As much as I adore my husband at a crowded party filled with an overwhelming abundance of other odours ranging from sweat, beer, urine, cigarettes , hairspray, perfume, peanuts, sausages,old sofa, carpet , etc I can't find him by smell but if I ask my dog after a few snuffles he can locate him in seconds (If I ask)…as to being able to discriminate the odors of fine wines ? I believe that is a rare skill although perhaps this is because my budget only extends to what I cheerfully refer to as "plonk".However not to be sniffed it is the 4 years of results collected by Robert Hodgons in California that even so called professional wine taster when blind folded often failed to tell the difference between a fine white wine and a red :).

  2. agelbert

    Well said. Dogs can tell, at a distance far greater than we humans, whether a person is their friend or not. They can recognize specific humans by their smell, something we humans can only do, if we can do it all, at a distance of a foot or less. Dogs can smell even with doors between them and the animal or person producing that smell, as long as the door is not hermetically sealed. We have no such ability.

    A dog (and cats too!) can detect the sound of a car engine of his owner well before anyone in the same household hears approaching the house.

    My cat, could actually hear my pacemaker after I had it implanted. He kept trying to figure out what it was long before he was aware that I had a slight lump on my chest under my clothing. No human can hear an implanted pacemaker circuitry.

    All that said, I agree with the article that it is ridiculous to associate the ability to smell well with lower intelligence. The people you mentioned in regard to wine certainly are less talented than dogs. Perfume makers seek, hire and handsomely pay the really gifted individuals in regard to smelling ability. They even have a name for them. They are called "Noses" for their finely developed sense of smell.

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