Ancient plague: New findings reveal early outbreaks in Scandinavia

In the Middle Ages, the plague, known as the "Black Death," took a tragic toll, killing one-third of Europe's population. The latest findings by scientists suggest that the 14th-century epidemic might not have been the first. The pathogen had shown its destructive power thousands of years earlier.

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

The Neolithic was a period when agriculture began to spread intensively, causing people to organize into larger groups than in hunter-gatherer populations. However, this also favored the spread of infectious diseases. As indicated by the portal iflscience.com, in 2019, the presence of the bacteria causing plague, Yersinia pestis, was shown in Scandinavia 5,000 years ago.

Not all strains of the virus or bacteria are equally contagious and deadly. Dr. Frederik Seersholm from the University of Copenhagen and his colleagues wanted to see how common the plague was among Neolithic farmers 5,300–4,900 years ago. To this end, they 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 — indicated Seersholm.

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

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

Scientists point out that the dramatic population decline of Scandinavia and northwestern Europe results from something truly significant. There is no evidence that massive climate changes contributed to this, hence the assumption 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 one destructive wave of the plague. The fate of one family was tracked over six generations, during which at least three epidemics caused by distinctly different strains of the plague occurred. This pattern is familiar because, after the Black Death of 1347-53, periodic resurgences occurred until the 17th century.

The mystery remains how the disease spread. It is known that fleas were not responsible for this, as was the case in the Middle Ages. Unlike the species from which it evolved, all strains lacked the mutation that allowed Y. pestis to survive in the insect's digestive tract.