Plague and the European Neolithic Decline: Population Discontinuity and Shifts in Societal Structure
Megaliths were ubiquitous across northwestern Europe during the late Neolithic but ceased to be built around 3,100 BCE. This cessation was part of a large-scale population decline at the end of the fourth millennium BCE, whose underlying causes remain debated. Recent studies suggest that this 'Neolithic decline' was caused by a plague outbreak accompanied by shifts in societal organisation and genetic ancestry. However, the magnitude of this claim is criticised, as so far evidence of Neolithic plaque is restricted to a handful of archaeological sites in northern Europe. Taking advantage of paleogenetics analyses of the French semi-megalith allée sépulcrale at Bury, for which 133 ancient genomes were sequenced, we test if plague initiated changes that could explain the Neolithic decline. The site covers two burial phases; one dated to the late fourth millennium BCE, the other to the early third millennium BCE, separated by a 100-200 year-long hiatus. We find evidence of changes in societal structure between the two phases, represented by two distinct genetic populations. Furthermore, we find four individuals to have been infected by Yersinia pestis, the causative agent of plague. These findings provide evidence that plague strains spread widely at the end of the fourth millennium BCE, and suggest an important role of infectious disease outbreaks in the population decline in multiple regions across Europe.