A new study published in Nature Ecology & Evolution examines the remains of 132 individuals buried in a large megalithic tomb near Bury, about 50 kilometers north of Paris. The site was used during two separate time periods, with a significant population decline occurring around 3000 BC between them.
Genetic analysis shows that the people buried before and after this decline were not related, indicating a major population replacement.
“We see a clear genetic break between the two periods,” said Frederik Valeur Seersholm, assistant professor at the Globe Institute at the University of Copenhagen and one of the lead authors of the study.
“The earlier group resembles Stone Age farming populations from northern France and Germany, while the later group shows strong genetic links to southern France and the Iberian Peninsula.”
These results point to a sharp drop in the local population, followed by the arrival of new groups migrating from the south.
Evidence of Disease and High Mortality
To better understand what caused this decline, researchers used a DNA technique that captures all genetic material preserved in bone. This approach revealed traces of ancient pathogens, including the plague bacterium Yersinia pestis and the organism responsible for louse-borne relapsing fever, Borrelia recurrentis.
“We can confirm that plague was present, but the evidence does not support it as the sole cause of the population collapse,” said Martin Sikora, associate professor at the University of Copenhagen and senior author of the study. “The decline was likely driven by a combination of disease, environmental stress and other disruptive events.”
Examination of the skeletal remains also found unusually high death rates during the earlier burial period, especially among children and young people.
“The demographic pattern is a strong indicator of crisis,” said Laure Salanova, research director at France’s National Centre for Scientific Research (CNRS).
Social Structure Changed After the Collapse
The genetic findings also highlight a major shift in how these communities were organized.
During the earlier phase, people buried in the tomb were often members of the same extended families, suggesting close-knit groups spanning multiple generations. In contrast, the later burials were more selective and largely centered around a single male lineage.
“This indicates that the population change was accompanied by a shift in how society was structured,” Seersholm said.
Part of a Broader European Decline
The study adds to growing evidence that the so-called Neolithic decline affected large parts of northern and western Europe, extending beyond Scandinavia and northern Germany.
It may also help explain why the construction of megalithic tombs and other large stone monuments came to an end across Europe during this period.
“We now see that end of these monumental constructions coincides with the disappearance of the population that built them,” Seersholm said.
