Taking "Pandemic" Seriously: Making the Black Death Global

TL;DR

Monica H. Green argues that historians should abandon scientific agnosticism about plague and incorporate new genetics, phylogenetics, and aDNA evidence into Black Death history. She proposes a broader global narrative that includes animal hosts, the Indian Ocean basin, and sub-Saharan Africa, not just the Mediterranean and Western Europe.

Key findings

• New microbiological work has established that *Yersinia pestis* caused the Black Death; by 2011 the complete genome of *Y. pestis* from fourteenth-century remains had been sequenced, and the fourteenth-century genome fits a previously postulated branch of the phylogenetic tree.
• Cui et al. (2013) constructed a *Y. pestis* phylogeny from 133 complete genomes; it places a polytomy (“Big Bang”) at c. 1268 CE (95% CI: 1142–1339 CE), immediately before the Black Death, and places the Justinianic strain on Branch 0 between nodes 04 and 05.
• The African strain 1.ANT, found in Central and East Africa, is closely related to the London Black Death strain and is estimated by Cui et al. to have diverged from the main Branch 1 line at c. 1499 CE (95% CI: c. 1377–c. 1650), suggesting a late medieval or early modern history of plague in sub-Saharan Africa.
• The likely geographic origin of *Y. pestis* is the Tibetan-Qinghai Plateau; Green argues this requires revising plague geography to include overland routes into Western Eurasia and southern routes through the Indian Ocean basin.

Methods

• This is a synthetic essay, not a primary genetics or archaeological study; it reviews and interprets recent aDNA, phylogenetics, historical, archaeological, and climate scholarship on plague.
• It uses the phylogenetic tree adapted from Cui et al. (2013), which analyzed 133 complete *Y. pestis* genomes, including two medieval London Black Death samples and 131 modern samples.
• It combines genetics with historical trade evidence, including Indian Ocean commerce, Cairo Genizah documents, Marco Polo on coral and musk, and archaeological evidence for Asian commensal rodents in East Africa.

Limitations

• The paper states that little genetics work has been done on sub-Saharan Africa on a scale comparable to China and Mongolia, making its African speculations “tentative in the extreme.”
• It states that there is currently no paleogenetic work from East Africa and no clear evidence of a trail of human plague from the Tibetan highlands to Indian Ocean ports in the fourteenth or fifteenth centuries.
• It notes that molecular-clock dating is contested and that the “Angola” strain’s provenance is lost; more broadly, the essay is an interpretive synthesis that repeatedly frames its new geographic claims as hypotheses requiring further research.