Ancient origins of the black death: Plague's hidden history revealed

In the Middle Ages, the plague, known as the "black death," had a tragic impact, killing one-third of the European population. The latest findings by scientists suggest that the 14th-century epidemic might not have been the first. It turns out that the pathogen showed its destructive power thousands of years earlier.

The plague epidemic in the 14th century decimated the European population. Today, it is considered one of the most devastating epidemics in world history. The latest findings by scientists indicate that the pathogen might have contributed to the "collapse of the Neolithic era" when the population of Scandinavia drastically declined.

The Neolithic era was a period during which agriculture began to spread intensively. This caused people to organise into larger groups than in hunter-gatherer populations, which facilitated the spread of infectious diseases. As reported by iflscience.com, as early as 2019, the plague-causing bacterium Yersinia pestis was shown in Scandinavia 5000 years ago.

Not all strains of the virus or bacteria are equally infectious and deadly. Dr. Frederik Seersholm from the University of Copenhagen and his colleagues wanted to check how common the plague was among Neolithic farmers 5300–4900 years ago. To this end, he examined the teeth and bones of 107 people from Sweden and one from Denmark.

The analyses show that 18 of these individuals, 17%, were infected with the plague when they died. Furthermore, our results suggests that the youngest plague strain we identify might have had epidemic potential — indicates Seersholm.

According to the scientists, the fact that these individuals were infected with the plague at the time of their deaths does not necessarily mean that it caused their deaths. The bacterium can be carried long until death occurs from other causes. Nevertheless, there is potential in this.

If 17% of people dying in a given year were victims of the plague, it would mean that the plague contributed only a small part of any population catastrophe. However, the remains from which the samples were taken did not come from a single period. Most of them came from before the plague arrived or between its waves.

Scientists indicate that the dramatic decline in the population of Scandinavia and north-western Europe results from something truly significant. There is no evidence that massive climate changes contributed to this, hence the suspicion that diseases are to blame.

We cannot—yet—prove that this was exactly how it happened. But the fact that we can now show that it could have happened this way is significant. The cause of this population decline, which we have known about for a long time, has always been subject of debate — said Seersholm.

The research allowed scientists to rule out that there was a single devastating wave of plague. They tracked the fate of one family over six generations, during which at least three epidemics caused by clearly different plague strains occurred. This pattern is familiar because, after the black death of 1347-53, there were periodic resurgences until the 17th century.

The question remains: How did the disease spread? It is known that fleas were not responsible, as was the case in the Middle Ages. All the strains lacked the mutation that allowed Y. pestis to survive in an insect's digestive tract, unlike the species from which it evolved.