The human sense of smell is as good as that of other mammals, such as dogs and rodents, according to new research. This shocking conclusion is entirely different from the usual assumption that humans have a weak sense of smell as a tradeoff for their great vision.

The investigation was driven by Rutgers University neurobiologist John McGann. He has been working for years to prove wrong the long-believed myth that discredits human sense of smell, and apparently, he has done so. He says that humans have as many functional odor receptors as other mammals that are considered to have a keen sense of smell, but sometimes people diminish the importance of smell.

Human Nose
“We’re like lots of mammals with a perfectly good sense of smell, and if we paid more attention to it, I think we’d realize how important it is to us,” said John McGann. Image credit: Austin Fit.

McGann wants to debunk the misconception about human sense of smell

McGann explained in his paper where this misconception about a poor human sense of smell began. He said that today people believe they don’t have a good sense of smell because of a wrong hypothesis made in the 19th century when French Anatomist Paul Broca stated that the part of the brain that is responsible for processing smell, was quite small if compared to the size of the human body. He said that other mammals have a clearly better sense of smell because their olfactory bulb was bigger in relation to their bodies.

Human Sense of Smell
Even Aristotle made a reference to the human sense of smell saying that men generally “smell poorly.” Image credit: iStock.

“Through a chain of misunderstandings and exaggerations beginning with Broca himself, this conclusion warped into the modern misapprehension that humans have a poor sense of smell,” wrote McGann. “Broca viewed smell as an animalistic sense that drove irrational behavior and thus must be diminished in importance in a rational being with free will.”

This misconception was passed from one generation to another, and now people still believe it. Other scientists have made other studies about the issue, following Broca’s idea. Even Charles Darwin said that the sense of smell was “extremely slight service” to civilized people, meaning that he believed that human’s sense of smell was atrophied as a mark of evolutionary advancement.

Human sense of smell is as good as that of mice

John McGann decided to prove wrong these theories beginning this research 14 years ago. According to his work, humans have about 1,000 odor receptor genes, which is similar to the number of odor receptor genes of mice, which have 1,100. However, some scientists say that counting and making assumption only based on odor receptor genes is not a solid indicator of the capacity to smell something. For instance, cows have nearly 2,000 odor receptor genes, and that would mean they smell better than dogs.

Another thing, which according to McGann is misconceived, is the fact that it is believed that two-thirds of human’s odor receptor genes are not functional and that they are now “evolutionary relics” that were needed and used by ancestors, but that now are useless for modern homo sapiens.

Little girl smelling a white gerber
“Human smell is not the same and dogs or rodents, but it’s clearly not notably worse,” says McGann. “If you restrict testing to traditional, volatile odors, then dogs and humans stack up pretty well against each other.” Image credit: Getty Images.

McGann says that even modern human use more their sense of smell than it is thought. What we use it for varies in relation with other mammals. For example, a dog’s sense of smell is more sensitive to the scent of explosives; while humans’ sense of smell is more sensitive than dogs’ to the smell of amyl acetate, which is what gives bananas their distinctive odor. That may be because humans have a greater need to determine when a fruit is ripe.

All mammals, even if the olfactory bulb-body relation varies, have approximately the same number of neurons. However, McGann said that maybe dogs have some advantage because they devote more of their attention and behavior to investigating and analyzing smells. The ability to smell for a trained tracker dog might be hard for humans to match.

Nonetheless, Broca wasn’t entirely wrong because the repositioning of the olfactory lobe enables animals to integrate smell in mental processes, not just to sense it, but to think about it too.

Humans tend to neglect their sense of smell in many ways. For example, McGann says that it helps people to make decisions, such as knowing if they should eat leftover food. As well, people tend to smell each other when they meet. Smell is an unexpected component of social interaction.

John McGann’s paper was published in the Journal Science, earlier this week.

Source: The Inquisitr