The idea of the weak sense of smell of people called the myth of the XIX century
According to popular belief, the sense of smell is not the strongest side of Homo sapiens. People are not able to perceive thousands of shades of one odor, as dogs, for example, do. Over the course of evolution, primates gradually lost their sensitivity to odors, losing genes associated with smell. In the human genome, many genes associated with olfactory receptors eventually became pseudogenes - non-functional analogs of structural genes that have lost the ability to encode proteins. With age, our already low sensitivity to odors decreases.
However, how weak can a person's sense of smell be considered? John McGann, head of the Laboratory for the Neurobiology of Sensory Perception at Rutgers University, believes that people underestimate their ability to perceive and distinguish between smells. In an article published in the journal Science, he suggested that the source of this widespread opinion may be the views of scientists of the 19th century.
McGann drew attention to several new studies of human perception of odors and concluded that a person's "sense of smell" is not as weak as it is commonly believed. Researchers at Rockefeller University said in 2014 that humans are capable of distinguishing about a trillion scents. Not only did Paul Brock's students at the University of California at Berkeley "take the trail," they found that this ability could be developed.
According to the scientist, the idea of the weakness of the human sense of smell originates in the works of the French surgeon and one of the founders of physical anthropology Paul Broca. This scientist discovered that a person's olfactory bulbs are extremely small in comparison with his brain. In other mammals, the relative size of the bulbs is much larger: for example, in mice this structure occupies 2% of the brain volume, in dogs - 0.31%, and in humans only 0.01%. Broca also noted that in terms of the ratio of the volume of the frontal lobes to the total volume of the brain, humans, on the contrary, are superior to many mammals.
Human and mouse olfactory bulbs, Science
The frontal lobes have been linked to behavioral control, a link already known in Brock's time. In the work of 1879, Broca divided all mammals into two categories: for the former, the sense of smell served as the main, fundamentally important sense, for the latter, sight or hearing was more important. Primates belonged to the latter. Since the sense of smell plays an important role in the sexual behavior of animals of the first group, Broca linked the relatively low significance of smell for people with a developed ability for self-control, for which the voluminous frontal lobes of the human brain are responsible. Brock's work consolidated the concept of a weak sense of smell in humans, and throughout the twentieth century, this point of view became more and more popular.
John McGann believes that the relatively small size of human olfactory bulbs does not indicate a poor perception of odors. The number of neurosensory cells associated with the sense of smell in humans is comparable to the number of such cells in many mammals. Further research will help establish how human perception of odors differs from that of animals.
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According to McGann, the bias against the human perception of odors can be reflected in modern medical practice. There are many olfactory disorders that significantly impair a person's quality of life. A person may completely lose their sense of smell (anosmia) or perceive natural odors as repulsive (parosmia). These disorders interfere with communication and can be harmful to health - for example, with anosmia, it is impossible to smell spoiled food. However, according to McGann, modern medicine often underestimates the problems of such patients. Further research into the human sense of smell will help find new treatments for these disorders.
Natalia Pelezneva