Plague spread 3000 years earlier than believed

“Plague is maybe the most traumatic event that has ever been recorded in human written times of the past, [but] the earliest physical evidence [to date] is from the first pandemic in 540 AD”, said Dr Rasmussen. Scientists have found traces of the disease in the teeth of ancient people, although the Bronze Age plague revealed by the new study seems to have lacked the ability to spread over wide regions, so probably remained in local pockets of disease.

The plague ridden population from the Bronze Age may have been pneumonic, which directly affects the respiratory system and causes intense, hacking coughing fits just before death.

The horrific disease known as plague was likely began infecting humans earlier than previously thought.

However, there is evidence that a few past outbreaks of Yesinia pestis were caused by different strains which are now extinct today. This new finding conflicts with previous studies suggesting that the ymt gene was acquired early in Y. pestis evolution due to its importance in the pathogen’s life cycle. Researchers said that the economic and political collapses also contributed a lot in devastating the effects of the plague.

This discovery dates the existence of Y. pestis to nearly 3300 earlier than thought, and means that fleas, long regarded as the model carrier of plague, could not have been harboring this bacteria. In outbreaks of bubonic plague, infected fleas (often travelling on rodents) transmit the bacteria to humans living nearby.

This mutation wasn’t presnt in the oldest DNA samples, and in the youngest sample, the flagella defense system was still in the process of developing in Y. pestis.

Ancestral plague would have been mostly spread by human-to-human contact, it is believed.

Based on their recent work, Willerslev, Kristian Kristiansen of the University of Gothenburg, and their collaborators suspected that the plague could have shaped human populations much earlier than previously thought. They learned that the Bronze Age plague didn’t possess a gene called Yersinia murine toxin, which allows the disease to replicate in fleas and ultimately spread like wildfire. In the prior study, the team extracted DNA from 101 human bones discovered in Europe and Asia, which were 3,000 to 5,000 years old.

In this undated photo released by Cell journal, a Bronze Age human skull painted with red ochre, from the Yamnaya culture of Central Asia, one of the cultures that carried the early strains of plague.

The finding of earlier plague episodes suggests it may have been behind the mysterious epidemics that hit ancient Greece at the end of the Classical period and for one that decimated the Imperial Roman Army, the researchers say.

The plague has been known to have eradicated millions of people over the centuries. This gene is involved in protecting the bacterium when it is inside the guts of fleas, thus helping the insects spread the plague to humans. But these two epidemics may or may have not been caused by plague. The methods laid out by the study could also be useful for examining other ancient diseases.

It may have had other influences throughout history, driving Bronze Age movements and migrations of people, the researchers suggest.

“The underlying mechanisms that facilitated the evolution of Y. pestis are present even today”, he said. Named the Plague of Justinian (after emperor Justinian 1, who survived the deadly disease), the plague arrived in Constantinople, working its way from port city to port city.