The myth of human's poor sense of smell

[grampahol]

I didn't explain it very well so here's the original.. In no way is it claiming we are going to be dog sniffers, but we can likely interpret what we smell better than we imagined. Some, quite a bit is thought to be at the sub conscious level such as fear, illness, mate selection, etc..

Quote:By Joanna Klein

• May 11, 2017
  

By shoving her nose against a fire hydrant, your terrier may be able to decipher which pit bull in the neighborhood marked it before her. But that doesn’t necessarily mean she’s a superior sniffer.
Still, it’s conventional wisdom that humans’ sense of smell is worse than that of other animals — dogs, mice, moles and even sharks.
This belief isn’t based on empirical evidence, but on a 19th-century hypothesis about free will that has more in common with phrenology than with our modern understanding of how brains work. In a review published Thursday in Science, John P. McGann, a neuroscientist who studies olfaction at Rutgers University, reveals how we ended up with this myth. The truth is, humans are actually pretty good at smelling our world.
“We’re discovering, to our delight, that the human smell system is much better than we were led to believe,” he said. It may be different than other mammals’ “but actually in ways that suggest that it could be more powerful than mice and rats and dogs.



This is how the human nose works. All day long special cells inside the nose capture chemicals from the sensory environment around us, sending signals to a squished blob of brain called the olfactory bulb. The bulb then sends information about what odor is in the nose to other parts of the brain that work together to make sense of it all, associating these smells with other stimuli in our environments or with memories or emotions we have experienced before.
The myth that trivializes this complex process began with Paul Broca, a 19th-century French physician who studied the human brain to understand what made us different from other animals. He compared its large frontal lobe and, below it, the squished region for smelling with the plump olfactory bulbs situated in front of the brains of other mammals. Then he categorized animals into what were basically called the smellers (most mammals) and the non-smellers (including humans).
Dr. Broca argued that big olfactory bulbs compelled animals to succumb to earthly desires, while humans had free will nestled within big frontal lobes, which helped them overcome the urges caused by sensing odors. Other scientists simplified his findings without testing any animal’s actual abilities. Sigmund Freud even suggested that mental illness arose from the weakened or unused human sense of smell. By 1924, a major textbook described human olfactory bulbs almost as if evolution of higher thought had shrunken them to near useless, atrophied blobs.
Today many of us learn that our pancake of an olfactory bulb isn’t of much value because other animals have relatively bigger systems to process odors. We may think that our ability to see the world trumps our need to smell it. And introductory psychology and biology textbooks still say we can discern only about 10,000 odors. But smell influences our behavior, memories and emotions. There’s little or nothing to prove it any less important than vision, and we can actually sift through billions, possibly trillions of odors.
So it’s true that your dog is so good at sniffing partly because she has an extrasensory organ, around 50 times more receptors, and 40 times more space in her brain, relatively speaking, to process scents. But it’s also true that you can smell a banana just as well as she can.



“Different animals in different ecological niches have different problems they need to solve,” Dr. McGann said.
What matters may not be the size or the space in the brain devoted to smelling, but other things like the ways our smell or brain systems are wired or used. Mice and humans’ olfactory bulbs, for example, differ in relative size, but the number of neurons inside them are pretty similar.
“We’re all trying to understand the same sensory world, so if you’re a really big animal you might need to have more neurons devoted to touch because there are a lot of spaces you can touch on,” Dr. McGann said. “But you don’t necessarily need to smell more smells because you’re bigger.”
And there’s a lot we can do with our noses. Like our dog, we can follow a scent trail if we try. We can detect the sour ping of vomit and decide to move from an otherwise empty subway car to the packed one next door. We can tell by a person’s odor if he works in a coffee shop. And though the evidence isn’t solid, some scientists think we can select mates, detect fear or stress, or find out if someone is sick by smelling another person’s sweat, blood or urine.
“There’s a true underappreciation for the way we use our sense of smell that contributes quite significantly to our overall well-being, the way we appreciate food and the way we interact with our environment,” said Johannes Reisert, who studies olfaction in rodents at the Monell Chemical Senses Center and was not involved in the review.
And a better appreciation of the powers of human olfaction could be important, Dr. McCann said. We could forge new paths to solving problems in medicine, social communication and emotional processing, like the consequences of a malfunctioning sense of smell.