Researchers have long clashed over the circumstances of the 1495 European syphilis epidemic. The so-called Columbian theory posits that Columbus and his crew carried the bacterium, or an earlier progenitor of it, when they returned to Europe in 1493 after their American journey. Skeletons of Native Americans who died prior to Columbus's arrival show bone lesions from Treponemal diseases, including yaws and bejel, and some researchers suspect syphilis was also present. However, other researchers believe syphilis itself circulated in Europe for centuries and became more virulent in the late 1400s. They point to a growing body of archaeological evidence: skeletal...