Where and when did the Black Death originate? The question has been asked for centuries and has led to heated debates among historians.
Now a group of researchers report they found the answer in the dental pulp of people buried in the 14th century.
Based on their analysis of the preserved genetic material, the researchers report that the Black Death arrived in 1338 or 1339 near Issyk-Kul, a lake in a mountainous area west of China in present-day Kyrgyzstan. The plague first infected people in a small nearby merchant settlement eight years before devastating Eurasia, killing 60 percent of its victims.
The research was led by Wolfgang Haak and Johannes Krause of the Max Planck Institutes for Evolutionary Anthropology and Human History in Germany and Philip Slavin of the University of Stirling in Scotland, who described their findings in Nature on Wednesday.
What was known as the Black Death — named for black spots that appeared on victims’ bodies — is caused by a bacterium, Yersinia pestis, transmitted by fleas that live on rodents. The disease is still present today and is transmitted by rodents on every continent except Australia. But infections are rare because hygiene is better. Infections are easily cured with antibiotics.
The 14th-century plague was actually the second major Y. pestis epidemic — the first being the sixth-century plague of Justinian, said Mary Fissell, a medical historian at Johns Hopkins University. But the Black Death is the best known and is considered one of the deadliest epidemics in human history.
Its terrors were recorded by Giovanni Boccaccio, an Italian writer and poet who witnessed the plague as it struck Florence. The disease, he wrote, “showed its first signs in men and women alike by swellings either in the groin or under the armpits, some reaching the size of a common apple and others the size of an egg, which people called bumps.” known as the “Sign of Impending Death”.
Historians traced the path of the epidemic – apparently starting in China or near China’s western border and spreading along trade routes to Europe, North Africa and the Middle East.
But Monica H. Green, a medical historian and independent scientist who wasn’t involved with the new paper, noted that historians would never be able to answer the question they posed: Was it really Yersinia pestis that caused this massive caused the pandemic?
“We hit a wall. We are historians and deal with documents,” said Dr. Green.
She vividly recalls meeting a paleopathologist 20 years ago who was studying leprosy, which leaves visible marks on skeletons.
“When are you going to make the plague?” asked Dr. Green. She said the paleopathologist replied that they couldn’t study the plague because a disease that kills people so quickly leaves no mark on bones.
Now this impasse has been overcome.
The search for the origin of the plague “is like a detective story,” said Dr. Fissell, who was not involved in the new study. “Now they have really good evidence of the crime scene.”
The hunt dates back more than a decade, when the group leading the latest study stunned archaeologists with their report that they could find plague bacteria DNA in the teeth of skeletons.
This study included plague victims in London.
Fourteenth-century Londoners knew the Black Death was coming, so they dedicated a cemetery in advance to be prepared for its victims. The bodies were exhumed and are now kept in the Museum of London. The situation was ideal because not only were these victims from a plague graveyard, but the date of their deaths was known.
“As an epidemiological case study, it’s perfect,” said Dr. Green.
“The technical skill that went into this work was just incredible,” she added.
Since the London study, the group has analyzed genetic material from plague victims at other sites and created a DNA family tree of plague bacterial variants. It and other researchers reported that the tree had one trunk and then appeared to suddenly explode into four branches of Y. pestis strains, descendants of which are now found in rodents. They dubbed the event the Big Bang and began searching to find out when and where it happened.
Historians have proposed various dates ranging from the 10th to the 14th centuries.
dr Slavin, a latecomer to the group analyzing plague victims in Kyrgyzstan, said one of his dreams is to solve the mystery of the Black Death’s origins.
“I was aware of two Christian cemeteries in Kyrgyzstan and started researching,” he said.
To his astonished delight, he found that hundreds of tombstones were accurately dated. Some had inscriptions stating in an ancient language, Syriac, that the person died of “plague.” And the death rate of the population had skyrocketed the year these people died.
“That brought it to my attention because it wasn’t just any year,” said Dr. Slavin. It was 1338, “only seven or eight years before the Black Death came to Europe.”
“We can’t ask for much more than to have headstones with the year,” he said.
Researchers found plague DNA in the teeth of three people whose gravestones said they died of “plague.”
The group also reports that the rodents that passed the bacteria to these victims were marmots. Marmots in this area today have fleas that carry a species of Y. pestis that appears to be descended directly from the ancestral strain.
And the researchers report that the trunk in Kyrgyzstan comes from the trunk that exploded into four trunks. It’s the beginning of the Big Bang, the group suggests.
If they are correct, said Dr. Fissell, the Big Bang appears to have occurred in Eurasia just before the Black Death, suggesting that the spread of the plague was most likely through trade routes and not, as some historians suggest, through military action a century earlier.
dr Green and other historians have suggested that the Big Bang happened when Mongolians spread the bacteria in the early 13th century. But if that had been the case, the bacteria in Kyrgyzstan would have been from one of the branches and not from the ancestral trunk.
“These battles in the 12th century are pretty irrelevant,” said Dr. fissel.
dr Green said she is convinced the group found plague victims in Kyrgyzstan. But she said the evidence now available was insufficient to justify her bold claims.
“Hold on,” said Dr. Green, adding that she expects more evidence to emerge.
For now, she said, the detective work has uncovered an important lead.
The work, she added, “puts a pin in the map with a date.”