The Sense Of Smell In Humans: Characteristics And Functioning
The human sense of smell can be truly amazing despite the fact that the idea that it is a sense that is not very useful, vestigial, atrophied and more typical of animals than of Homo sapiens, a species that is too rational to be guided by it, continues to be widespread and deep-rooted.
Since ancient times, and especially since the 19th century, smell has been seen as a sense that gives us little information, but thanks to the most recent research in cognitive sciences we know that this is not the case. Furthermore, cross-cultural studies have shown that there are many languages where smell is very relevant.
Next we will talk about the sense of smell, the anatomical structures that make it possible, why the belief is rooted that it is poorly developed in humans and we will also see cases of cultures where it does acquire great importance.
Many people still believe that human beings have an underdeveloped sense of smell and that in no way can we compete against other animals, such as dogs or mice, when it comes to identifying odors. For a long time it has been thought that this sense was vestigial in our species and that throughout evolution it has ended up being relegated, especially due to the improvement of our sight and hearing.
This has been a very common belief but, thanks to cognitive science and taking a cross-cultural perspective, it has been shown to be false. The idea (Western, by the way) that humans cannot smell very well is an old myth, whose origins date back to the 19th century and which has greatly influenced both science and popular culture.
Although it is true that there are many species that are better than us at identifying odors, our sense of smell is as good as that of many other mammals. Humans we can discriminate around a billion different smells (it was previously believed there were only 10,000) and, despite having a relatively small olfactory bulb, our abilities to recognize odors are better than the scientific community originally thought.
How does it work?
Before we talk further about how the sense of smell has been discredited, let’s talk about how it works in humans. Basically, this sense serves to identify chemical substances that swarm through the air and that, upon contact with the chemoreceptors found in the nose a nervous signal is sent to the brain where they are identified as odors.
Inside the human nose you can find three nasal conchae, one for each of the three nostrils. These turbinates are surrounded by the pituitary, a mucosal structure that is responsible for warming the air before it reaches the lungs. The pituitary gland secretes mucus, the pituitary gland, which moistens and protects the nasal walls. In the pituitary there are cilia which contain thousands of olfactory receptors cells that are responsible for capturing chemical substances that enter the nose.
When chemical substances come into contact with the cilia, a nervous signal is produced, emitted by the receptors found therein. This signal will be sent through nerve fibers to the olfactory bulb from which the information will end up in different regions of the brain where the interpretation of these stimuli will be made and they will be recognized as odors.
Smell and taste are closely related, for this reason when we suffer from a disease in which the nose is affected, it also affects our way of tasting food This is clear when we have a cold and produce a lot of mucus, a fluid that blocks our olfactory receptors, preventing us from detecting odors and flavors, which are chemically the same.
When did this sense begin to be underestimated?
According to John McGrann, who in 2017 conducted research delving into when we began to give little importance to smells, we owe the origins of the myth that smell is an underdeveloped and vestigial sense in humans to Paul Broca himself. , a 19th-century French brain surgeon and anthropologist. It is he who is credited with spreading the belief that human beings have an underdeveloped olfactory system compared to other species.
In his documents dated 1879, Broca, based on the fact that the human olfactory area had a smaller volume compared to the rest of the brain, He interpreted this to mean that human beings did not depend as much on smell to survive as other animals did, such as dogs and rodents Thus, he indicated that this was what made us have free will and that instead of being guided by smells, we made use of our mental abilities, especially our reason.
This statement came to influence great figures in psychology, including Sigmund Freud, who stated that due to the lack of smell in human beings this made us more prone to mental disorders. This statement is partly right, but it is not applicable to the entire human species. What has been seen is that People with damaged or reduced sense of smell are more likely to suffer from psychiatric disorders not because the human species has this “reduced” sense.
These “findings” and interpretations made by both Broca and Freud and many other thinkers of the 19th century further fueled the deep-rooted belief that the sense of smell was poorly adaptive and did not serve much purpose in the human species. In the Western world there was (and still is) the idea that those who allow themselves to be dominated by their sense of smell are allowing their animal instinct to dominate them, an instinct that is always perceived as something irrational and illogical, thus further discrediting this sense.
However, Modern, cross-cultural scientific evidence denies that we are bad at detecting odors It is true that, compared to other species, our olfactory bulb is a little smaller, but this smallness is rather relative. This brain structure sends signals to other areas of the brain to help identify odors and, in fact, it is quite large and similar in size and number of neurons to other mammals that no one has doubted are good at recognizing and guiding themselves by smells. smells.
Smell is important, since it plays an important role when choosing food, avoiding harm and deciding who our partner is. In addition to these more “animal” functions, we must add to this that human beings are the only species that use odors for religious purposes (e.g. incense in churches), medicinal (e.g. aromatherapy) and aesthetics (e.g., air fresheners and deodorants). Smelling does not seem to be just an individual act, but rather an interactional one
We differ from other animals not because we have atrophied it, but because we give it a different use. For example, dogs are able to differentiate the smells of different urine for territorial and dominance purposes, an ability that is of no use to us as humans. On the other hand, we are able to differentiate between the smells of wine, those of cheese or even between varieties of cocoa and coffee, this being a useful skill that we use to recognize which foods are best for us or have more caloric and lipid content.
cross-cultural view
Many studies have tried to delve deeper into the importance of smell by analyzing the wide repertoire of vocabulary that languages could have to encode smells , based on the idea that if a concept, feeling or meaning is important for the human species, several languages must refer to it. That is, if smells are important to human beings, more than one linguistic community must have a wide repertoire in the form of words and grammatical structures to reference them.
When this question began to be addressed, many studies focused on English, a language that was found to have a fairly small vocabulary related to odors and their properties. This same lack of vocabulary about smells was found in other European languages, which led many to rush to believe that this sense actually had little weight in the human species.
Smell-related language is rarer in English compared to other perceptual modalities For example, in this language, words related to vision are 13 times more used than the most common words related to smells. A study that analyzed 40,000 words of this language found that there were about 136 times more words related to vision compared to those related to smell.
However, when analyzing the vocabulary of other languages it was seen that what was found in Europe could not be extrapolated to a global level at all. There were many languages in which smells were represented in a wide variety of words and, not only that, but there were also languages in which smells and their properties were grammaticalized or used as metaphors.
Each language has a frequency use and a number of words associated with different smells, with the languages of Africa, the Amazon and Asia being the ones that have the most words in this sense. Some examples of this are Cha’palaa, ǃxóõ, Wanzi, Yombe, Maniq and Jahai to name a few, although the languages in which smell is of great importance number up to a thousand.
Many of these languages are spoken by hunter-gatherer communities , which makes sense that they have extensive vocabularies related to smell. For them, knowing how to recognize, identify, position and orient themselves based on what they find in nature is essential for their survival. Knowing how lions smell, how far away a fruit tree is, or how areas close to your home smell are aspects of your daily routine and therefore smells are as important as any other perceptual modality.
Loss of smell as a sign of illness
The loss of smell can be synonymous with something going wrong in our brain. Yes, it can be due to a problem directly associated with the nose, such as having too much mucus or a sinus infection, but it can also be due to the brain structure that is responsible for recognizing odors failing due to illness. neurodegenerative.
Smell can deteriorate as part of the aging process and may be a warning sign of a possible case of dementia If a patient indicates that he is feeling that things don’t smell like they used to, doctors should start to worry. The sense of smell should not be treated as if it were inferior, since in the same way that if a person is becoming blind or deaf it arouses great concern, the fact that they also lose their sense of smell and taste should also be frightening.
Among the diseases in which the loss of smell can be found as an early symptom of the pathology, we have memory problems and dementias such as Alzheimer’s and Parkinson’s. Loss of the sense of smell has also been seen to predict COVID-19. And even if the patient does not present dementia or any illness, losing the sense of smell can lead him to commit more accidents, such as cooking, burning something and starting a fire that he will realize when it is too late. late.
Besides, loss of smell has been associated with depression and obesity , health conditions that apparently do not seem to be related to the sense of smell. All these pathologies seem to show that yes, the sense of smell is important for human beings beyond the “instinctively animal” or as a vestigial sense and that, in fact, it has importance at a health and social level.
