The origin of the mediaeval Black Death pandemic (AD 1346–1353) has long been studied because of its massive impact on population and society. However, most studies have focused on surviving European records, but they provide little insight into the actual origin of this world-changing pandemic. A new study published in Nature reconstructs the DNA of Yersinia pestis from ancient burial sites, suggesting that 1338 was the date of the first outbreak which would later go on to ravage Eurasia.
Conventional thinking puts the onset of the Black Death at 1346 in the Black Sea region. Recent analysis of historical, genetic and ecological data led to the suggestion that the emergence of Y. pestis branches occurred more than a century before the beginning of the Black Death. According to the proposed model, this initial diversification was linked with territorial expansions of the Mongol Empire across Eurasia during the early thirteenth century. But in this study, the researched present ancient Y. pestis data from central Eurasia supporting a fourteenth-century emergence – putting the emergence a full century later, closer to the conventionally accepted 1346 date.
Until now, the most debated archaeological evidence on the pandemic’s initiation came from cemeteries located near Lake Issyk-Kul in modern-day Kyrgyzstan.
These sites are thought to have housed victims of a fourteenth-century epidemic as tombstone inscriptions directly dated to 1338–1339 state ‘pestilence’ as the cause of death for the buried individuals.
Researchers analysed ancient DNA data from seven individuals exhumed from two of these cemeteries, Kara-Djigach and Burana. The combination of archaeological, historical and ancient genomic data implicates Y. pestis in this epidemic event.
Two reconstructed ancient Y. pestis genomes represent a single strain and are identified as the most recent common ancestor of a major diversification commonly associated with the pandemic’s emergence, here dated to the first half of the fourteenth century. Comparing these ancient genomes present-day diversity from Y. pestis reservoirs in the Tian Shan area where China, Kazakhstan and Kyrgyzstan meet supports a local emergence of the recovered ancient strain.
Exactly how Y. pestis made it to western Eurasia is unknown, but previous research suggested that both warfare and/or trade networks were some of the main contributors in the spread of Y. pestis. However, the lack of any military campaigns in this period and the proximity of trans-Asian networks plus trade items at the site suggest trade playing a role in Y. pestis dissemination.
The authors conclude that “Although the ancient Y. pestis genomes reported in this Article offer biological evidence to settle an old debate, it is the unique historical and archaeological contexts that define our study’s scope and importance. As such, we envision that future synergies will continue to reveal important insights for a detailed reconstruction of the processes that triggered the second plague pandemic.”
