A Plague of Plague

From Science News, courtesy my friend William Campbell:

A 5,000-year-old mass grave harbors the oldest plague bacteria ever found

A long-dead Scandinavian woman has yielded bacterial DNA showing that she contracted the earliest known case of the plague in humans.

DNA extracted from the woman’s teeth comes from a newly identified ancient strain of Yersinia pestis, the bacterium that causes plague, the oldest ever found. The woman’s bones, which date from 5,040 to 4,867 years ago, were found nearly 20 years ago in a mass grave at an ancient farming site in Sweden.

Teeth from an adult male in the same grave contain traces of the same plague variant, say evolutionary geneticist Simon Rasmussen of the University of Copenhagen and colleagues. But plague DNA from the woman is better preserved, the team reports online December 6 in Cell.

Comparisons of the newly found Y. pestis strain with other ancient and modern strains suggest that a plague epidemic emerged more than 5,000 years ago in densely populated farming communities in southeastern Europe. Then the plague spread elsewhere, including to Scandinavia, via trade routes, Rasmussen’s team concludes. That ancient epidemic apparently contributed to sharp population declines in Europe that began as early as 8,000 years ago.

In particular, the scientists suspect that an early form of plague developed among southeastern Europe’s Trypillia culture between 6,100 and 5,400 years ago. Trypillia settlements were the first to bring enough people into close contact to enable the evolution of a highly infectious version of Y. pestis, the team suggests. Trading networks then transmitted the plague from Trypillia population centers, home to as many as 10,000 to 20,000 people, to West Asian herders known as the Yamnaya, the researchers argue. In this scenario, herders infected by the Trypillia people probably spread what had become a new strain of the plague both eastward to Siberia and westward to the rest of Europe, including Scandinavia. Yamnaya migrations to Europe roughly coincided with the rapid abandonment and burning of large Trypillia settlements, which probably occurred as a result of plague outbreaks, the scientists say.

More at the link.

The End of the Aztecs

From The Independent (hat tip: Tim Furnish):

Mystery over death of 15 million Aztecs may be solved after nearly 500 years, study suggests

DNA analysis of skeletons reveals traces of disease

Judith Vonberg 

Scientists believe they may have discovered the cause of an epidemic that struck Mexico’s Aztec population in 1545, killing up to 15 million people.

In a paper published in Nature Ecology & Evolution, they describe how DNA extracted from the teeth of 29 skeletons buried in a cemetery in southern Mexico revealed previously unidentified traces of the salmonella enterica bacterium.

The bacterium is known to cause enteric fever, of which typhoid is an example. According to the study, the symptoms tally with those mentioned in records from the time, which describe victims developing red spots on the skin, vomiting, and bleeding from various body orifices.

The epidemic was one of several to hit the indigenous population soon after the arrival of Europeans in the early 16th century.

“When the Europeans arrived in Mexico, they brought with them lots of different diseases,” Ashild Vagene, co-author of the study, told The Independent. “There were dozens of epidemics across the New World and Mexico was particularly hard hit.”

“What we’re talking about is the devastating decimation of indigenous populations by previously unknown diseases,” Dr Caroline Dodds Pennock, lecturer in International History at the University of Sheffield, told The Independent.

“Mortality rates were maybe 80 or 90 per cent by 1600,” she said. “Imagine nine out of every 10 people dying – it’s almost unimaginable.”

The cause of the 1545-1550 epidemic has been debated for more than a century. Measles, pneumonic plague and influenza have all been suggested as possibilities, but historians have never reached a consensus.

More at the link.

The Black Death

From the BBC:

Rats were not to blame for the spread of plague during the Black Death, according to a study.

The rodents and their fleas were thought to have spread a series of outbreaks in 14th-19th Century Europe.

But a team from the universities of Oslo and Ferrara now says the first, the Black Death, can be “largely ascribed to human fleas and body lice”.

The study, in the Proceedings of the National Academy of Science, uses records of its pattern and scale.

The Black Death claimed an estimated 25 million lives, more than a third of Europe’s population, between 1347 and 1351.

More at the link.