Out of the East (or North or South): A Response to Philip Slavin

Abstract This article responds to Philip Slavin’s ‘Out of the West: Formation of a Permanent Plague Reservoir in South-Central Germany (1349–1356) and Its Implications’. Genetics has transformed the study of plague, one of the most lethal diseases in human history. But this technically demanding science raises questions of what constitutes valid evidence and supportable argument when examining historical phenomena at a microscopic level. Slavin argues that two new lineages of Yersinia pestis, the causative organism of plague, were seeded in central Germany following the Black Death; appearing sequentially, one lineage caused plague outbreaks in the 1350s and early 1360s, only to retreat and be replaced by a second lineage. Here, evidence is adduced to support the early central European proliferation of one lineage of Y. pestis, but also to suggest that the second lineage arose simultaneously in a different locale, outside Europe and within different epidemiological parameters. Because of the inherent rarity of biological evidence, the reconstruction of epidemiological phenomena will always require consilience with archaeological and documentary sources. Establishing ‘best practices’ of analysis and verification in this emerging multidisciplinary field has implications not only for Europe’s four hundred-year experience with plague, but for all fields of global health history.