In the late 1990s, at a former Han Dynasty military base in China called Xuanquanzhi, archaeologists excavated wall inscriptions and writings on silk that had been buried underground for more than 2,000 years. But some of the artifacts on which ancient Silk Road travelers left their mark came not so much from their minds as from their rear ends. In a latrine used between 111 and 109 BC, researchers discovered a trove of bamboo “wipe sticks,” each wrapped at one end with a bit of cloth—the oldest bum fodder on…
