In the book "Gulp: Adventures on the Alimentary Canal," author Mary Roach explores the fascinating intricacies of the human digestive system and how it parallels various animal behaviors. One intriguing aspect she highlights is the universal reaction to unwanted food stimuli, where individuals pull a "gape" by opening their mouths wide and sticking out their tongues to expel the offending substance. This reflex not only serves as a protective mechanism but also illustrates a shared behavioral trait among species.

Roach describes this reaction as the "disgust face," emphasizing its significance in the context of human evolution and survival. By examining the science behind these physical responses, she delves into how our reactions to food and disgust have developed over time, linking the physiological processes to broader themes of health and survival. Her engaging writing style makes complex biological concepts accessible and entertaining, offering readers a unique lens on something as routine yet vital as eating.