Plague Train: The Black Death was not the first plague epidemic, but perhaps its master

Madagascar is notorious for new outbreaks of plague.

The plague made its way there towards the end of the 19th century and continues to cause new death reports year after year.

For this island, Africa, South and North America, it is a fairly recent, still existing plague - but it once developed in Eurasia.

In the late Middle Ages, the so-called Black Death was rampant here.

In less than a decade it is said to have killed 50 million people;

Entire regions were depopulated, and the city of London lost an estimated half of its inhabitants.

It is known who brought him to Europe and by what route: In the autumn of 1347, Death docked in the port of Messina.

Genoese who had to abandon their fortress on the Crimean peninsula had the plague on board,

Sonya Kastilan

Editor in the "Science" department of the Frankfurter Allgemeine Sunday newspaper.

• Follow I follow

Important seaports such as Naples, Pisa, Marseille and Florence were the next gateways, followed by trade routes upriver and overland.

In 1349 the plague attacked Germany from several directions.

At that time, viruses or, as in this case, bacteria, were unknown as triggers; instead, unfavorable planetary constellations, poisonous vapors, the so-called miasms, the work of the devil or the wrath of God were suspected.

Historians and epidemiologists have long argued with microbiologists about the actual cause, but it has been known for a good decade: Yersinia pestis

was found at several sites in Europe, i.e. cemeteries with typical graves, including the cities of Augsburg, Parma and London.

Paleogeneticists had finally succeeded in isolating the telltale bacterial genes from the remains of victims of various outbreaks.

No doubt Yersinia was the Black Death, then, but where did this fast-killing plague, which covers its victims with conspicuous black or bluish spots all over their bodies, begin?

The oldest evidence of bubonic plague so far comes from graves in Eastern Europe. The pathogen must have undergone a change a few millennia ago that made this line zero a greater danger for humans - and fleas its carriers.

"What was circulating in the Stone Age was something completely different, but after the splitting up 4,000 to 5,000 years ago, all the genes are actually present in the pathogen, with the same contagion potential as we know from the bubonic plague today," explains Johannes Krause Max Planck Institute for Evolutionary Anthropology in Leipzig.

The Justinian plague of antiquity arose from this lineage of bacteria, but when

swept through Europe again in the late Middle Ages, the pathogens belonged to a new lineage from afar.

China and Mongolia came under suspicion early on because a large variety of Yersinia can still be found there in the natural "plague reservoir", i.e. in rodents.

Perhaps famine was conducive, and Genghis Khan could have driven the Black Death westward with his horsemen?

However, the previous theses do not match the "Big Bang" that is emerging in the molecular genetic data: "At a certain point something happens, the family tree splits up like a bouquet of flowers," explains Krause, which is referred to in technical jargon as a polytomy.

The genetic trace found, for example, in plague victims in London is counted as line 1 today.

While it was close to the genetic split, it was a few mutations past the crucial node in the family tree,

which could mean at most decades—not centuries.

"Eighty percent of all current plague pathogens go back to this point, we wanted to find the time and place." Wanted: a common ancestor.