A devastating population collapse that destroyed Stone Age farming communities across the north Europe 5,000 years ago may have been driven by an outbreak of the plague, according to research.
The cause of the disaster, known as the Neolithic collapse, has long been a matter of debate.
Studies based on DNA from human bones and teeth excavated from ancient burial vaults in Scandinavia – seven from an area in Sweden called Falbygden, one from coastal Sweden near Gothenburg and one from Denmark – now suggests that disease played a central role.
The remains of 108 people – 62 men, 45 women and one undetermined – were studied. Eighteen of them, or 17%, were infected with plague at the time of death.
The researchers were able to map the family tree of 38 people from Falbygden over six generations, spanning about 120 years. Twelve of them, or 32%, were infected with plague. Genomic findings indicated that their community experienced three distinct waves of an early form of plague.
The researchers reconstructed full genomes of the different strains of the plague-causing bacterium Yersinia pestis that are responsible for these waves. They determined that the last one might have been more virulent than the others, and they identified characteristics that indicated the disease could have spread from person to person to cause an epidemic.
“We learned that the Neolithic plague is an ancestor of all later forms of plague,” said Frederik Seersholm, a geneticist at the University of Copenhagen and lead author of the research. published in the journal Science.
A later form of this same pathogen caused the Justinian Plague of the sixth century AD and the 14th century Black Death that ravaged Europe, North Africa and the Middle East. Because the strains circulating during the Neolithic decline were much earlier versions, the plague may have produced different symptoms than those in the epidemics millennia later.
The study showed that the pest was abundant and widespread in the area investigated.
Martin Sikora, who is also a geneticist at the University of Copenhagen and a co-author of the report, said: “This high prevalence of plague suggests that plague epidemics played a substantial role in the Neolithic decline in this region.
“Indeed it seems plausible that the decline seen in other parts of Europe was also affected in some way by plague. We already have evidence for plague in other megalithic sites in different parts of Northern Europe. And seeing how common it was in Scandinavia, I would expect a similar picture to emerge once we study these other megaliths at the same resolution.”
The Neolithic or New Stone Age involved the adoption of farming and animal domestication in place of a wandering hunter-gatherer lifestyle. The Neolithic population crash in Northern Europe occurred from about 3300 BC to 2900 BC. By that time, cities and sophisticated civilizations had already emerged in places like Egypt and Mesopotamia.
The populations of Scandinavia and northwestern Europe eventually disappeared entirely, replaced by people known as the Yamnaya migrating from a steppe region spanning parts of present-day Ukraine. They are the ancestors of modern Northern Europeans.
“Until now, several scenarios have been proposed that could explain the Neolithic decline: war or simple competition with steppe-related populations that became common after the Neolithic decline; an agricultural crisis leading to widespread famine; and various diseases, including plague,” Seersholm said. “The challenge was that only a single pest genome had previously been identified, and it was not known whether the disease could spread in a population of humans.”
The DNA evidence also provided insight into the social dynamics of these communities, showing that men often had children with multiple women and that the women were brought in from neighboring communities. The women appeared to be monogamous.
“Multiple reproductive partners can mean multiple wives. It could also mean that men are allowed to find a new partner if they become widowers or if they have mistresses,” said Seersholm.
