The discovery of the New World in the 15th century presented a novel opportunity for exchange of culture, society and biology between two geographically isolated worlds. It did not go particularly well. At the human level, it has been generally accepted that the New Worlders got the short end of the stick as Europeans rained genocide down on the aboriginal cultures of the Americas. This occurred either intentionally (Pizarro’s conquest of the Incas) or unintentionally (the decimation of Mississippian cultures by smallpox). However, it seems as if at least in one case, the American cultures got a little bit of revenge that has lasted for a long time.
The first reports of syphilis in Europe stem from the invasion of Italy by the French army of Charles VIII. The victorious French army brought a little more than they expected home from the south of Italy and subsequently spread syphilis throughout Europe. Most Europeans called it the French disease, the French called it the Italian disease, the Italians called it the African disease. The source of syphilis has been under contention since then, with European scholars tending toward the Columbian hypothesis – that crew of Columbus’ original voyage of discovery brought syphilis home with them. Late last century, a number of criticisms of the Columbian hypothesis were raised – most of them coming from social scientists and lacking any strong scientific evidence.
This week a collaborative effort between scientists at Emory University (USA) and the Universities of Toronto (Canada) and Oxford (UK) presents strong scientific evidence to support the Columbian hypothesis of syphilis’s origin. The groups, led by George Armelagos of Emory, present in PLOS Neglected Tropical Diseases (yes, a real journal) phylogenetic evidence that the ancestor of the bacteria that causes syphilis is endemic to South America. Because the Americas and the Old World were geographically isolated until the 15th century, their results imply that syphilis arose in the New World and spread to the old with returning European explorers.
Syphilis is caused by the pallidum subspecies of the bacterium Treponema pallidum. Kristin Harper, the student who would have done the bulk of the work, and her collaborators looked at 21 genetic regions from this and other related subspecies of Treponema. Phylogenetic analysis allows researchers to establish evolutionary relationships based on changes that occur in a species genome. The researchers found that the syphilis causing subspecies is most closely related to a strain of Treponema pallidum pertenue, a bug that causes a disease known as yaws and is endemic to Guyana in South America. Interestingly, related strains of the yaws causing subspecies did arise in Africa and a variant of syphilis that infects apes arose from these African strains, but human syphilis does appear to be derived from the South American bacterial strains.
Studies like this one are one of the reasons that phylogenetic analysis can prove quite powerful. It allows scientists to participate in the writing and reanalysis of history. Two other phylogenetic studies published this week shed light on other historical events. A recent paper in Genetics follows the spread of agriculture by analyzing the timing of the establishment of different barley strains across Europe and Asia. A second study, published this week in PLOS Genetics, involves an extensive analysis of Pacific Islanders which allows the researchers to pinpoint the origins of modern Polynesians. I think my friends in the History Department might should watch their backs.