A demographic crisis similar to those caused by major historical epidemics such as the Black Death was caused by a combination of factors around five thousand years ago.
There are about 5,000 yearsa huge demographic crash in northwestern Europe drastically altered the composition of the region’s populations, and new human groups took their place. It was not known how this population collapse happened — until now.
According to new research into the megalithic tomb of Burysituated about 50 kilometers north of Paris, a combination of infectious disease, environmental stress and demographic contraction had lasting effects on the genetic and cultural distribution of the continent, 3100 B.C.
The stone funerary monument that was under investigation contains the remains of around 300 people and revealed that there was an approximately 200-year break in burial practices, between about 3100 and 2900 BC. According to the study in Nature Ecology & Evolution, this gap coincides with a period of broader population decline in northern Europe, until now very poorly understood.
The study analyzed DNA and demographic data from 132 individuals buried in Bury. The researchers concluded that the tomb corresponds to two distinct phases of funerary occupation. The first occurred between about 3200 and 3100 BC; the second began only around 2900 BC there is no genetic continuity significant difference between both phases.
According to the results, individuals from the first phase showed broad genetic diversity, linked to agricultural populations spread across several European regions. Those in the second phase formed a much more homogeneous group, with more than 80% of their ancestry associated with Neolithic of the Iberian Peninsulacorresponding to what is now Spain and southern France. This indicates that, after the population collapse, the Paris Basin was repopulated by groups from the south.
In addition to genetic differences, burials from the first phase show multigenerational family communities and evidence that women coming from abroad married and joined these groupsadvance the . In the second phase of burials, the tombs include smaller families and even individuals with no apparent ties buried side by side. Y chromosome lineages also change markedly: there has been an abrupt population replacement rather than a gradual cultural evolution.
At the end of the fourth millennium BC, construction of megalithic tombs suddenly ceased in several regions of northwestern continental Europe, including the Paris Basin, central Germany, and southern Scandinavia. For more than a thousand years, these structures had been a common, landmark burial practice. Everything points to a large-scale crisis — and other data support this interpretation.
Pollen records show that during the interval without burials, forests grew again, a sign that agricultural fields and pastures were abandoned. Changes in subsequent agricultural practices are also observed. For researchers, this evidence points to the emptying of entire towns, in a pattern comparable to that observed after major historical epidemics, such as the Justinian Plague or the Black Death.
Ancient pathogens were also identified in the human remains from Bury, including plague and relapsing fever transmitted by lice. Although it is not possible to attribute the crisis to a single cause, the team argues that the combination of disease, environmental pressure and population decline will have created a demographic void.
The sudden “empty” opened doors to the arrival of neighboring groups. Researchers say these groups were made up of steppe pastoralists in Scandinavia and Iberian farmers in the Paris Basin.
