The performance of the human nose is underestimated. It would be able to distinguish a trillion different smells, says a study published in the journal Science.
For decades, scientists have considered the human nose to be an organ capable of only smelling a few tens of thousands of odors. The dog’s nose is even considered a better tool than the human nose for spotting odors. Yet no one has ever provided concrete evidence that the human nose can only smell 10,000 different smells. Scientists suspected that this ridiculous figure was probably wrong. This study fixes an aberrant scientific error.
The human nose, an incredible organ
This study, carried out by Andreas Keller of Rockefeller’s Laboratory of Neurogenetics and Behavior and Leslie Vosshall of Howard Hughes Medical Institute, is a first of its kind.
Unlike the studies already carried out on odors, the two researchers were interested in the intensity of odors and not in how people perceive them.
The study of smell is extremely complex. For example, a rose has over 275 molecules that make up its scent, but only a tiny percentage outweighs all the others. Each scent is a complex mixture of molecules which makes it extremely difficult to study. To get around this difficulty, the two researchers only selected 128 molecules responsible for odors such as orange, anise or mint. Subsequently, they incorporated 10, 20, 30 molecules together, with some present in several mixtures. “We didn’t want them to be easily recognizable, so most of our mixes were weird and disgusting,” admits Leslie Voshall. Once the mixtures were completed, the researchers made the volunteers smell three mixtures: two with common scent molecules and a totally different one. Each time, participants had to say which of the three mixtures did not resemble the other two. They had to smell 264 different combinations. Of the 26 volunteers for the experiment, 51% managed to give the correct answer almost every time.
Using the results obtained and extrapolating them, the two researchers established that the human nose was able to distinguish a trillion different smells! Nothing to do with the 10,000 odors established in 1920. And again Leslie Voshall thinks that the number is even more important because “there are much more than 128 odorous molecules in the world”. The trillion figure is therefore probably an understatement.
Righting an injustice
The human nose has always been underestimated because of the 1920 figures. What seems surprising is that unlike the eyes and ears, very little experimentation has been done on the smell and the nose. “We know exactly how many sound frequencies people can hear, not because somebody invented it, but because there have been tests,” says Leslie Voshall. For example, the researchers estimated that the eye could distinguish between 2.3 and 7.5 million different colors. For its part, the ear can recognize 340,000 different tones.
For Andreas Keller, the disinterest that people have for the nose and the smell is explicable. Our ancestors had a better appreciation of smells. The use of the refrigerator and the daily showers also got rid of odors that existed even a hundred years ago.
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