The Black Death

DNA Studies and the Black Death

The application of molecular biology to ancient skeletal remains has revolutionised the study of the Black Death. The recovery and sequencing of Yersinia pestis DNA from medieval plague cemeteries has confirmed the identity of the pathogen, traced its evolutionary history, and resolved longstanding debates about the pandemic’s cause and character. DNA studies represent the most significant advance in Black Death scholarship in recent decades.

The First Recovery of Ancient Plague DNA

The first successful recovery of Y. pestis DNA from medieval remains was achieved in 2000, when a team led by Didier Raoult and Michel Drancourt reported the detection of plague DNA in teeth from a fourteenth-century cemetery in Montpellier, France. This result was controversial: some scholars questioned the reliability of the methods used and the possibility of contamination with modern DNA.

The debate was resolved in 2011, when a team led by Kirsten Bos and Johannes Krause published the complete genome sequence of Y. pestis recovered from teeth from the East Smithfield plague cemetery in London. The team used stringent methods to authenticate the ancient DNA, including the analysis of damage patterns characteristic of ancient molecules and the comparison of results across multiple independent laboratories. The genome confirmed beyond doubt that Y. pestis was the pathogen responsible for the Black Death.

The East Smithfield Genome

The East Smithfield genome revealed several important findings. First, the medieval strain of Y. pestis was ancestral to nearly all modern plague-causing bacteria. This finding established the Black Death as the source of the Second Pandemic and demonstrated that the medieval strain was the common ancestor of the plague lineages that persist today.

Second, the genome showed no obvious “hypervirulent” mutations that would explain the extraordinary mortality rates of the fourteenth century. The medieval strain was genetically very similar to modern strains that cause plague today, suggesting that the pandemic’s severity was driven by ecological and social factors — rat and flea densities, population susceptibility, the co-circulation of multiple clinical forms — rather than by the intrinsic properties of the bacterium.

Third, the genome provided a molecular clock for dating the divergence of plague lineages. The analysis suggested that the Black Death strain diverged from other known Y. pestis lineages shortly before the pandemic began, consistent with the hypothesis that the bacterium emerged from its Central Asian reservoir in the 1330s or 1340s.

The Issyk-Kul Discovery

A 2022 study led by Maria Spyrou achieved a further breakthrough by recovering Y. pestis DNA from teeth buried in cemeteries near Lake Issyk-Kul in Kyrgyzstan, dated to 1338–1339. Tombstones at these cemeteries attributed deaths to “pestilence” (mawtānā in Syriac), and the DNA analysis confirmed that the ancestral strain of the Black Death lineage was present in the region at precisely this time.

This finding located the pandemic’s origins in the Tian Shan region of Central Asia and provided the earliest known evidence of the specific lineage that would devastate Europe, the Middle East, and North Africa. The discovery confirmed the hypothesis, based on historical and ecological evidence, that the Black Death emerged from the rodent reservoirs of the Central Asian steppe.

Resolving Historical Debates

The molecular evidence has resolved several longstanding debates about the Black Death. The most fundamental question — whether the pandemic was caused by Yersinia pestis or by some other pathogen — has been answered definitively. The recovery of Y. pestis DNA from multiple medieval plague cemeteries across Europe has confirmed the bacterium’s identity and eliminated alternative pathogen hypotheses that had been proposed by some scholars.

The molecular evidence has also informed debates about the pandemic’s geography and chronology. By comparing the genomes of medieval and modern strains, researchers have reconstructed the evolutionary relationships between different plague lineages and traced their spread across time and space.

The Future of Ancient DNA Research

The field of ancient DNA research continues to advance rapidly. New techniques for extracting, sequencing, and analysing ancient molecules are making it possible to recover genetic information from increasingly degraded samples. The application of these techniques to plague cemeteries across Europe, Asia, and Africa promises to provide a more detailed and more comprehensive picture of the pandemic’s geography, chronology, and biological character.