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Body Odor Could Smell Worse Than Your Ancient Ancestors

When you understand something, odor molecules sailing inside your nose, where they bind to proteins – called olfactory receptors – on 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 the olfactory receptors for two common odor molecules: a musk found in soaps and perfumes and a compound prominent in smelly underarm sweat. The team also found that recent evolutionary changes to these olfactory receptors make humans less sensitive to those odors. So, if you’re one of those lucky people who aren’t overwhelmed by body odor, maybe you should thank evolution. The work has been published in PLoS Genetics on Thursday.

Olfactory receptors can date back hundreds of millions of years and are thought to exist in all vertebrates. Humans are around 800 olfactory receptor genes, but only about half of them are functional, meaning they will be translated into proteins that fly out in the nose and detect odor molecules. But in a functional gene, small variations can cause changes in its corresponding receptor protein, and those changes can have a big effect on how smell is perceived.

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

With that said, genetic changes aren’t the only thing that’s fundamental to explaining smell. “One is genetics and the other is experience, which includes things like the culture you grew up in,” says Hiroaki Matsunamia molecular biologist at Duke University, who was not involved in the research but whose work focuses on the sense of smell.

The study by Dr. Mainland and colleagues is a collaborative effort between scientists in the United States and China. They sequenced the genomes of 1,000 people in Tangshan, China, who belonged to the Han ethnic group. They did the same with an ethnically diverse cohort of 364 in New York City. Participants were asked to rate, on a 100-point scale, the intensity and pleasantness of a range of common odors. The researchers then looked for links between the olfactory and odor receptor genes and variations within those genes and their potential impact on odor perception.

By sampling a large diverse population, the researchers were able to learn about odors whose perception was based on genetic differences between people, rather than cultural or experiential factors. That leads them to molecules that include trans-3-methyl-2-hexenoic acid and galaxolide.

Trans-3-methyl-2-hexenoic acid is considered one of the most pungent odor compounds in underarm sweat. Galaxolide is a kind of synthetic musk Usually described as having a floral, woody scent used in perfumery and cosmetics, but also things like a kitten smell. The team was able to identify variations of the olfactory receptor for those odors, and in both cases, people with the more recently evolved gene variant noticed significantly less intense odors.

The galaxolide findings were particularly striking, with some participants being unable to smell musk. “It’s really rare to find an effect as large as what we’ve seen for this one receptor on the perception of musk odors,” says Marissa Kamarcka neuroscientist at the University of Pennsylvania who was the study’s author.

Dr. Matsunami sees this work as another example of how the human sense of smell is more complex than initially thought. He said that, although the main findings in the study involved only two scents, they add proof that “odor receptors as a group have a distinctive diversity.”

The authors argue that their findings support a hypothesis that was criticized that primates’ olfactory systems have degraded over evolutionary time. Kara HooverAn anthropologist at the University of Alaska Fairbanks, who was not involved in this study but who studies the evolution of human smell, was initially unconvinced by that hypothesis.

“Why is the magnitude of the decrease said to be attenuated?” she asked. “Maybe other things are becoming more acute or the ability to distinguish odors is improving. We know too little to draw these conclusions.”

For Dr. Hoover, these findings have stirred other evolutionary questions. “Our species is very young,” she said. “Why is there so much volatility in such a short period of time? Does it make sense to adapt? “

https://www.nytimes.com/2022/02/03/science/nose-odors-evolution.html Body Odor Could Smell Worse Than Your Ancient Ancestors

Fry Electronics Team

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