My Evolutionarily Adaptive Response to Dog Poop

Any dog owners out there who (like me) don’t have their own yard in which to let their dog run wild, will probably agree that picking up after your dog is the most unpleasant daily aspect of having one. Every time I lean down to scoop up a pile of my dog Zooey’s regular gift to me, my nose wrinkles up, my eyes squint—and occasionally I may gag a little bit.

This expression of disgust is a common one. Charles Darwin, in The Expression of the Emotions in Man and Animals, noticed that some expressions like this occur throughout the world in many different cultures, and even in some animals. Thus, he hypothesized, they may have a biological rather than environmental origin. If so, Darwin suggested, they probably also have an adaptive purpose.

Recently a group of researchers from the University of Toronto investigated this 130-year-old hypothesis. They took two expressions that are widely considered to be universal: the wrinkled nose, raised lip, and narrowed eyes of disgust, and the wide eyes and flared nostrils of fear. They developed computer-generated images of faces displaying a typical rendition of each of these visages, then asked volunteers to recreate them while they underwent breathing and vision tests.

They found that each expression had specific effects on breathing and vision that could be considered adaptive. The look of disgust limited air flow and vision, a reaction which could be beneficial in keeping potentially noxious substances out of the eyes and mouth. The fearful expression improved peripheral vision, made eye movement quicker, and increased air flow—all responses that could theoretically make someone more prepared to face danger.

While these results may seem obvious in hindsight, I must admit it’s not something I ever thought about before when I picked up after Zooey.