The skeleton was found in Latvia in the 19th century, but its genetic analysis has only just been performed. Scientists have found a new candidate for the role of “patient zero” with the plague: in the remains of a man who died over 5 thousand years ago in the territory of modern Latvia, the oldest known strain of the disease was discovered.
In the bones of a hunter-gatherer found at the Neolithic site of Rinnjukalns near the Salaca River in northern Latvia, traces of the causative agent of plague – Yersinia pestis bacteria – have been found. The remains of two people were discovered at this site in the 19th century, but were then lost in an anthropological collection in Germany until 2011. Subsequent excavations uncovered two more burials.
The DNA of ancient bacteria is missing a number of genes that later made plague a much more dangerous disease: 5,300 years ago, it could not be transmitted by fleas carried by rats and other rodents, whereas the bubonic plague that devastated countries in Eurasia in historical times and still occasionally occurs today spreads in exactly the same way.
A man from Rinnjukalns in his 20s or 30s, according to the analysis of his remains, died of the plague, but he was buried just like his fellow tribesmen, which means that they didn’t perceive what happened to him as anything out of the ordinary. “Most likely, he was bitten by a rodent, contracted a primary infection of Yersinia pestis, and died of septic shock within a few days, maybe a week,” says Dr. Ben Krause-Kjær of Kiel University in Germany. No traces of the plague were found in three other nearby skeletons.
Rinnyukalns on the banks of the Salatsa River in Latvia is a well-known ancient human settlement. Later, the plague mutated to become more contagious and deadly. Europe experienced several plague pandemics, one of which, known as the “Black Death” in the 14th century, wiped out half the continent’s population. Recurring waves of disease ravaged Europe for several centuries, claiming millions of lives. In our time, the plague is treated with antibiotics if diagnosed early.
The discovery of an early form of the plague pathogen has forced scientists to revise previous ideas about the evolution of the disease. Until now, the widely held hypothesis was that the plague was as contagious in prehistoric times as it is today, and was therefore the cause of a significant population decline in Western Europe at the end of the Neolithic period. However, scientists at the University of Kiel now suggest that plague was sporadically transmitted from animals to humans about 7000 years ago, when the first agricultural cultures appeared in central Europe. Because it was not as contagious at that time, there were no major disease outbreaks. The study was published in the journal Cell Reports.