38. Origins of the Black Death
The Black Death first erupted in Mongol-ruled China and Central Asia in the 1330s. Traveling along the Silk Road with merchants and Mongol armies, the disease took about fifteen years to reach Europe in 1347. However, although the plague itself first erupted in China, the culprit bacteria might have originated in Europe, thousands of years before the Black Death.
Research in 2018 found evidence of Yersinia pestis in a Swedish tomb dating back to 3000 BC. It may have caused a devastating plague thousands of years ago that led to the Neolithic Decline around 3000 BC, when Europe’s population took a nosedive. It also caused Justinian’s Plague, a sixth-century disease that, as seen further down this list, rivaled the Black Death in lethality and devastation.