Why do we get so grossed out by stuff?

By Casey Frye, CCNN Writer

muddy pup
Would you pet the cute puppy even if that wasn’t mud?

If you saw a stray dog covered in poop, would you scratch behind his ears? Probably not! In fact, I don’t think anyone would want to be around the pooch because… well, he’s kind of disgusting! Think about it though, if the dog was covered in mud, people probably wouldn’t be quite so reluctant to give him a quick belly rub, huh? I thought so. Well, both poop and mud get you dirty, so why is one way more gross than the other?

According to London School of Hygiene and Tropical Medicine director Valerie Curtis, disgust is an emotion, just like fear. However, while our “fight or flight” response evolved to protect us from large animals that want to eat us from the outside, disgust developed as as a defense against tiny organisms that eat us from the inside. It why we’re grossed out by materials like trash, poop, rotten food, and  – I can’t believe I’m saying this – people!

That’s right, our repulsion partially evolved to protect us from humans who can’t keep themselves clean. Can you imagine shaking a person’s hand after they just coughed into it? It’s gross, not to mention rude! In fact, Curtis – who thinks of herself as a “disgustologist” – says that human manners stem from our sense of squeamishness. “With disgust, you start with microbes, go on to manners and then on to morality,” she explains. “It’s an emotion that teaches you how to behave. It helps build the moral framework of society.”

When she says society, she means all aspects of it. According to Curtis our disgust emotion affects just about everything we do. It contributes to clothes we wear, people we hang out with, products we buy, and of course, food we eat! I always thought a number of different factors were behind my choices, but I guess not. “Disgust is fascinating because it’s a model emotion,” said Curtis. “It tells us a lot about how all the emotions work.”

Featured image courtesy of Tambako the Jaguar on Flickr. Image of muddy puppy courtesy of CavinB on Flickr.