What really grosses you out? Snakes or spiders, perhaps. Or putrid, rotting, stinky food. Or people who hurt, take advantage of, or exploit other people.

Each of these trigger our sense of disgust, defined in the dictionary as “profound aversion or repugnance excited by something offensive.”

You might think that the disgust we feel toward rotten food—ignited by a reaction to the chemicals emitted—is different from the moral disgust we feel about things like slavery or incest. Maybe not, at least according to a collaborative research effort from the University of Pennsylvania and the University of Virginia.

Writing in Science these investigators compared detailed facial expressions in subjects experiencing either unpleasant liquids or unfair treatment in a money game (323 [27 February 2009], 1222–1226). They conclude that both types of disgust result in the same facial motor activity, and offer this as “evidence for the oral origins of disgust.”

It is intriguing to think that an ancient chemical-sensing mechanism that exists to avoid toxic substances could evolve into a more modern system of moral judgment. It’s a parsimonious argument—and evolutionarily favored if different types of disgust use the same biological machinery.

Still, I’m not convinced. Just because different inputs result in a common output doesn’t necessarily mean that the same processing occurred in between, or even that other collateral outputs (behaviors, in this case) might not be more pertinent. So I’ll wait for a more molecular mechanistic explanation before I conclude that holding my nose in disgust is the same reaction no matter what the offense.