Bones and teeth from the bodies of Stone Age people have indicated that the plague led to a decline in populations. Recent research shows the earlier suppositions were mistaken, and the plague was playing a prominent part in culling Europe’s populations long before it finally mounted the massive outbreaks of the Middle Ages.
On the other hand, when the ‘Black Death’ surged a wave of devastation through the 14th-century Europe, it swept away nearly a third of its population.
That has discovered, the plague happened to have its entry into Scandinavia several thousand years ago, according to new research from the University of Copenhagen. And, despite many theories putting it in a different role, it may have been caused by an acute epidemic.
DNA traces have been found in 108 teeth and bones belonging to individuals who died 5,000 years ago, according to research at the Globe Institute.
“The analyses show that 18 of these individuals, 17 percent, were infected with the plague when they died. Furthermore, our results suggest that the youngest plague strain we identify might have had epidemic potential,” says postdoc Frederik Seersholm, who led the DNA analysis.
Passage Grave, Frälsegården, Skulls
They are the crania of the two second-generation individuals in the right branch, FRA022 and FRA023, positioned alongside a limestone slab that covered the ancestral individual FRA021. Credit: Karl-Göran Sjögren
It would thus have contributed to the population collapse, known as the Neolithic decline, at the end of the Neolithic. The population bust caused large parts of the farming population in Scandinavia and northwestern Europe to disappear within just a few centuries—5,000 years ago.
‘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 important. The cause of this population decline, which we have known about for a long time, has always been subject to debate,’ said Seersholm.
The archaeological material investigated comes predominantly from the passage graves in Sweden, but one of the persons originates from a stone cist in Stevns, Denmark.
The ancient DNA provides the answer
The analyses were performed by a technique known as “deep shotgun sequencing”, which makes it possible to obtain some extremely refined information from archeological material, even though ancient DNA is quite often greatly damaged or destroyed. The researchers examined DNA from tooth and bone materials from the Neolithic time period to analyze familial relationships and diseases of the individuals involved.
“We have been able to carry out a full mapping of the lineages of plague and a detailed description of the other microbes in the DNA data.”. “At the same time, through these analyses, we were able to look at the human DNA from a broad perspective to a local one – and right down to the individual level, getting a picture of the social organization that existed back then,” Associate Professor Martin Sikora continues at the Globe Institute.
Analysis by researchers found that 17 percent of those tested harbored plague-causing bacteria in their genetic material, leading to the conclusion that the plague was widespread in Scandinavia during the late stone age. Among the relatives of one of the six generations mapped by researchers in the analyzed family, outward evidence of a minimum of three separate outbreaks by the plague was found to exist.
“It is 200 years since it became known that skulls and other human bones along megaliths in northwestern Spain were really dolmens and not abandoned piles of rocks. That has left a tantalizing unsolved question regarding probable kinship between these particular individuals, whose bones and teeth one found, in these megaliths. Many theories and speculations have been penned, but now we have data: from DNA,” says Karl-Göran Sjögren, Associate Professor of Archaeology at the University of Gothenburg, also involved in the new study.
Frederik Seersholm opines that a new series of results shows the previously thought theories, which suggested that plague could not have caused the population decline, are wrong.
“Regarding the decline of the population at the end of the Neolithic, both war and outbreaks of infectious diseases, including plague, have been put forward. There have been several theories involving the plague, and one of them suggested that the plague could not have caused an epidemic – but that assumption no longer holds, says Frederik Seersholm.
The impact of plague on ancient populations, in particular in the Neolithic of Europe, is being somewhat reconsidered following new research. In contradiction to precedented theory that people at the end of the Neolithic period mostly died out for other reasons—not plague, but mainly warfare—the study presents really compelling evidence that plague outbreaks did take place, and these outbreaks are almost certain to have played a major role in the demographic collapse. This discovery changes our perception of ancient diseases and their profound effects on humans and human societies millennia ago.
Underlying the methodological advances in the field of aDNA analyses, especially the use of “deep shotgun sequencing” combined with the methods applied here, is a revolution in the resolution possible during the extraction of highly informed genetic data from degraded archaeological remains. In fact, researchers traced plague bacteria in the 5,000-year-old DNA recovered from teeth and bones and even charted their family ties. In its turn, it permits the elaboration of detailed information about ancient societies in their social organization and, finally, about how diseases have been passed down the line within many generations.
It also strongly indicates that plague was endemic to Neolithic Scandinavia; plague outbreaks identified within the same family lineage date back over six generations. That is, it is not a single event but a recurring danger. Taken together, these types of data highlight how pathogen genetic history places present understanding of how a disease like plague might have affected human evolution and prehistoric societal resilience into context.
In this respect, therefore, the ripples this study makes have far-reaching implications across archaeology and genetics alike. They re-echo the stories of historic population demographics, disease outbreaks, and responses engineered by ancient cultures. Genetic data, archaeological and historical records, when used in concert, will continue to help researchers tease apart the interaction of humans and pathogens throughout history—drawing lessons that may well inform both contemporary public health strategy and responses to emerging infectious diseases.