Amidst the deep, dark secrets that we all have, there is always one that is so simple, yet strange that not all have the bravery to tell. Namely when things that should smell bad, sort of don’t smell bad. They low key smell incredible. Gasoline, sharpies, maybe even something more embarrassing smell ghastly to most people, but to some, it might as well be a vanilla pumpkin candle in the middle of fall. Why the heck does this even happen? Why do some things smell great and others absolutely repulsive?
Well you can thank natural selection and your great-great grandma and grandpa for your ability to distinguish good and bad smells. (If you need our refresher on how smelling happens, click here.) When smell particles travel from the outside world into your nose, some of your 40 million olfactory receptor cells associated with a particular smell will fire and tell your brain what’s you are smelling.
Back in the days before google or books, your great-great x100 grandma gave oranges a look over and a good sniff and thought, “I could probably eat that.” Voila! GMa discovered a new food, no one gets scurvy, and the “Oranges smell good” gene gets passed down eventually to you. Another gatherer came along, found some rotten eggs, and didn’t think they smelled too bad. After your grandmama gave them a hard pass, the rest of the clan went to nom-town, died, and couldn’t pass on their “rotten eggs smell good” gene and are gone forever.
Moreover, Rehan Khan, a neuroscientist, found that smells that come from lighter, tightly packed molecules are more likely to smell better than heavier, spread out molecules. For example, the smell that they add to natural gas is more dense than the smell added to perfumes to give it the smell of citrus. As to any rule there are exceptions, but in the big ol’ world of smells, this is a start.
So after throwing out that chunky milk and sensuously wrapping your hands around a hot, aromatic cup of cocoa, you can thank your ancestors for giving you the ability to distinguish safe from not. As for the gasoline, sharpies, or whatever, your secret is safe here, so long as you don’t eat them and stop your genes from passing on.