A person’s sense of smell may be stronger than was thought

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 the same smell, as do, for example, dogs. In the course of evolution, primates gradually lost sensitivity to smells, losing genes associated with smell. In the human genome, many genes associated with olfactory receptors eventually became pseudogenes – non-functional analogues of structural genes that have lost the ability to code proteins. With age, our already low sensitivity to smells is falling.
 
However, how weak can a man’s sense of smell be? John McGann, head of the laboratory of sensory perception neuroscience at Rutgers University, believes that people underestimate their ability to perceive and distinguish smells. In the article,
Published in the journal Science, he suggested that the source of this widespread opinion may be the views of scientists of the XIX century.
 
McGann drew attention to several new studies of human perception of odors and concluded that the “scent” of man is not as weak as is commonly believed. Researchers from the Rockefeller University in 2014 said that people are able to distinguish about a trillion fragrances. Students at the University of California at Berkeley not only learned to “take a trace”, but also found that this ability can be developed.
 
According to the scientist, ideas about the weakness of human sense of smell originate in the works of the French surgeon and one of the founders of physical anthropology Paul Brock. This scientist discovered that human olfactory bulbs are extremely small compared to 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 it is 0.31%, and in man it is only 0.01%. Also, Broca noted that in relation to the volume of frontal lobes to the total volume of the brain, man, on the contrary, surpasses many mammals.
 

Olfactory bulbs of man and mouse, Science
 
Frontal lobes are associated with the control of behavior, during Brock’s time this connection was already known. In the work of 1879 Broca divided all mammals into two categories: for the first, the sense of smell was the main, fundamentally important feeling, for the latter, vision or hearing was more important. Primates belonged to the second. Since the sense of smell plays an important role in the sexual behavior of the animals of the first group, Broca associated a relatively low importance of smell for people with developed ability for self-control, for which the volume frontal lobes of the human brain correspond. Brock’s work consolidated the notion of a weak sense of smell, and throughout the twentieth century this view was becoming more popular.
 
John McGann believes that the relatively small size of human olfactory bulbs does not indicate a weak perception of odors. The number of sensory cells associated with smell in humans is comparable to the number of such cells in many mammals. Further research will help to establish how much the human perception of odors differs from the perception of animals.
 
According to McGuinn, prejudice toward human perception of odors can affect modern medical practice. There are many smelling disorders that significantly impair a person’s quality of life. A person can completely lose his sense of smell (anosmia) or perceive natural odors as repulsive (parosmia). These disorders interfere with communication and can harm health – for example, with anosmia it is impossible to identify the smell of spoiled foods. However, according to McGann, modern medicine often underestimates the problems of such patients. Further research on human olfaction will help find new methods of treating these disorders.