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When you smell something, scent molecules Sail inside your nose, where they attach to proteins called olfactory receptors in the cells lining your nasal cavity. These receptors trigger signals that your brain interprets as one or more odors.

A team of scientists has identified olfactory receptors for two common odor molecules: a musk found in soaps and perfumes, and a compound featured in scented armpit sweat. The research team also discovered that more recent evolutionary changes in these olfactory receptors have altered people’s sensitivity to these scents. study published In PLoS Genetics Thursday.

Olfactory receptors can be traced back hundreds of millions of years and are believed to be present in these receptors. all vertebrates. people around 800 olfactory receptor geneshowever, only half of them are functional, meaning they will be translated into proteins that hang in the nose and detect odor molecules. But within a functional gene, minor variations can cause changes in the corresponding receptor protein, and these changes can greatly affect how an odor is perceived.

“There is a molecule called androstenone,” aforementioned Joel MainlandD., a neuroscientist at the Monell Chemical Senses Center and author of the new study. “And we know that some people smell this molecule as urine, some people smell this molecule in sandalwood, and some people don’t smell it at all.”

However, genetic changes are not the only thing underlying odor interpretation. “One is genetics and the other is experience, which involves things like the culture you grew up in,” he said. Hiroaki MatsunamiA molecular biologist at Duke University who was not involved in the research, but whose work focuses on olfaction.

The study by Mainland and colleagues was a collaborative effort between scientists in the United States and China. They sequenced the genomes of 1,000 people belonging to the Han ethnic group in Tangshan, China. They did the same with an ethnically diverse group of 364 people in New York. Participants were asked to rate the intensity and pleasantness of a range of common scents on a 100-point scale. The researchers then explored the associations between olfactory receptor genes and odors, as well as variations in these genes and their potential effects on odor perception.

By sampling a large, diverse population of humans, the researchers were able to host odors whose perceptions are based on genetic differences between people rather than cultural or experiential factors. This led them to molecules including: trans-3-methyl-2-hexenoic acid and galaxysolid.

Trans-3-methyl-2-hexenoic acid is considered one of the most pungent compounds in armpit sweat. galaxysolid a synthetic musk Described as having a floral, woody scent often used in perfumes and cosmetics, it is also used in things like cat litter. The research team was able to identify olfactory receptor variants for these scents. In the case of armpit odor, most people with the evolutionarily newer gene variant found it more intense. The opposite was true for Galaksolid.

The galaxolide findings were particularly striking, with some participants unable to smell musk at all. “It’s really rare to find an effect as large as we’ve seen for this single receptor on the perception of musk odor,” he said. Marissa KamarckA neuroscientist at the University of Pennsylvania who is the author of the study.

Dr. Matsunami cites this work as another example of how the human sense of smell is more complex than people originally thought. Although the main findings in the study included only two scents, their add to the evidence “As a group, olfactory receptors have extraordinary diversity.”

The authors think their findings support a hypothesis he criticized that the primate olfactory system degenerated over evolutionary time. Black HooverAn anthropologist at the University of Alaska Fairbanks, who was not involved in this research but studies the evolution of human scent, was not convinced at first.

“Why is reduced density assumed to be degradation?” she asked. “Maybe other things are getting more intense or odor discrimination is improving. We know too little to draw these conclusions.”

Dr. For Hoover, these findings raised other evolutionary questions. “Our species is really young,” he said. “Why so much diversity in such a short time? Does it have adaptive significance?”