Forget sliced bread or AI software. There is no greater marker of civilization, of just how far we have come from our primate ancestors, than the public restroom. All animals must answer the call of nature, but how many can claim to have created little spaces where everyone can do their business in a calm, private environment, where waste is discreetly flushed away, and the space is communally maintained? 

Public restrooms are primarily an urban phenomenon—there being less need for them out in the countryside, where calls of nature can be answered within nature itself. The Ancient Romans were big on communal latrines, where people would sit convivially along planks with holes that opened onto remarkable drainage systems. In China, meanwhile, evidence has been found of communal latrin...