Eeeww! Ancient, unknown strain of plague found in 5,000-year-old tomb in Sweden

The discovery came about as the researchers were analyzing publicly available databases of ancient DNA for cases in which infections might have claimed prehistoric victims. They focused on the previously excavated site of Frälsegården in Sweden. Previous analysis of a limestone tomb at the site found that an estimated 78 people were buried there, and they all had died within a 200-year period. The fact that many people died in a relatively short time in one place suggested they might have perished together in an epidemic, lead study author Nicolás Rascovan, a biologist at Aix-Marseille University in Marseille, France, told Live Science. The limestone tomb was dated to the Neolithic, or New Stone Age, the period when farming began.

The researchers discovered the previously unknown strain of plague in the remains of a woman at the Frälsegården site. Carbon dating suggested she died about 4,900 years ago during a period known as the Neolithic Decline, when Neolithic cultures throughout Europe mysteriously dwindled.

researchers suggested that the plague emerged in so-called mega settlements of 10,000 to 20,000 inhabitants that existed in Europe between 6,100 and 5,400 years ago. These mega settlements — up to 10 times larger than previous European settlements — "had people, animals, and stored food close together, and, likely, very poor sanitation. That's the textbook example of what you need to evolve new pathogens," senior study author Simon Rasmussen, a computational biologist at the University of Copenhagen, said in a statement.

If plague evolved in these mega settlements, "then when people started dying from it, the settlements would have been abandoned and destroyed. This is exactly what was observed in these settlements after 5,500 years ago," Rasmussen said.