The Silk Road was a network of ancient commerce, connecting China with central Asia, the Middle East and the Mediterranean. It was established by the Han Dynasty in 130 B.C. and operated until 1453 when the Ottoman Empire blocked its main routes. During its heyday, the road's travelers shuttled not only silk, spices, gunpowder and paper, but also religions, new technologies and science into Europe.
Despite its many benefits, researchers have long thought that the Silk Road also spread illnesses, including anthrax and leprosy. Now, scientists finally have some proof that traders may have spread diseases along the route, reports Maev Kennedy at The Guardian.
Cambridge researchers Hui-Yuan Yeh and Piers Mitchell examined fecal material found on “hygiene sticks” in a latrine excavated at Xuanquanzhi, a large station on the Silk Road used between 111 BC and 109 AD. These hygiene sticks were made from bamboo and wrapped in cloth at one end and served as the ancients' solution to defecating in a pre-toilet paper era.
The scientists identified eggs from four species of parasitic worms in the material including roundworm, whipworm, tapeworm, and Chinese liver fluke, which they describe in The Journal of Archeological Science: Reports. The fluke is of particular interest. It requires marshy areas to properly develop and reproduce. But Xuanquanzhi is in the arid Tamrin basin of northwest China—nearly 1,000 miles from the closest suitable habitat. This means that the fluke's host had to have traveled some distance to reach the station.
“When I first saw the Chinese liver fluke egg down the microscope I knew that we had made a momentous discovery,” study co-author Hui-Yuan Yeh says in the press release. “Our study is the first to use archaeological evidence from a site on the Silk Road to demonstrate that travelers were taking infectious diseases with them over these huge distances.”
Notably, these hygiene sticks were actually excavated 20 years ago, Kennedy reports. While documents discovered during the dig—some even written on silk or walls—were celebrated, scientists largely ignored the sticks. But Hui-Yuan Yeh was excited to learn about the sticks and soon sent samples to Mitchell, a biological anthropologist and medical historian who studies the parasites found in feces.
There is already some strong evidence for other diseases spreading along the route. For instance, in 2013 National Institutes of Health researchers determined that Behcet’s disease, a genetic autoimmune disease, clusters in communities along the ancient Silk Road. Another study suggests that fleas on wild gerbils in Central Asia likely passed plague bacteria to Silk Road traders, which led to plague outbreaks in Europe years later.
Yet this latest find provides direct evidence for the presence of parasites. “Our finding suggests that we now know for sure that the Silk Road was responsible for spreading infectious diseases in ancient times,” Mitchell writes at The Conversation. “This makes more likely previous proposals that bubonic plague, leprosy and anthrax could also have been spread along it.”