The ancient Chinese practiced copromancy, the diagnosis of health based on the shape, size and texture of feces. So did the Egyptians, the Greeks and nearly every ancient culture. Even today, your doctor may ask when you last had a bowel movement and to describe it in exquisite detail. 
Sure, it’s uncomfortable to talk about. But that’s where science comes in, because what we don’t like to discuss can still cause harm. Irritable bowel syndrome, inflammatory bowel disease, gastrointestinal infections and other poop-related ailments cost Americans billions of dollars annually.
But trying to stem these problems was not our main motivation for trying to figure out some of the physics of defecation. It was something else, much more sinister.
