Attacks of Deadly Extinct Pathogens Possibly Wiped Out Ancient Civilizations, Claims Study

Highly-developed late Bronze Age civilizations suddenly slipped into decline between around 1200 – 1150 BCE, with many regions subsequently taking centuries to recover. Their collapse has intrigued scientist, who have been probing what might have happened and suggesting a plethora of factors.

Scientists have analyzed newly-found ancient bone remains, using sequencing of DNA, to make what they believe is a fascinating discovery.

Multiple Bronze Age civilizations, such as the Old Kingdom of Egypt and the Akkadian Empire, collapsed approximately at the same time thousands of years ago.

Declining populations, dwindling trade and cultural changes were also wrought across the Ancient Near East and the Aegean, claim historians, naming various possible factors, ranging from climate change to shifting allegiances leading to devastating raids.

However, in remains excavated from an ancient burial site on the island of Crete, in Hagios Charalambos cave, a team led by archaeogeneticist Gunnar Neumann of the Max Planck Institute for Evolutionary Anthropology, Germany, discovered genetic evidence of virulent pathogens.

Scanning electron micrograph depicting a mass of Yersinia pestis bacteria

© Wikimedia Commons

As the bacteria found is known to have been responsible for such historically deadly diseases as typhoid fever and plague, the team claimed that these pathogens - Y. pestis and S. enterica - may have been a lethal factor in the collapse of the ancient civilizations.

"The occurrence of these two virulent pathogens at the end of the Early Minoan period in Crete emphasizes the necessity to re-introduce infectious diseases as an additional factor possibly contributing to the transformation of early complex societies in the Aegean and beyond," the scientists wrote in their paper, published in Current Biology.

The plague bacterium Yersinia pestis was the culprit in some of the most destructive historical pandemics that wiped out tens of millions of people. However, prior to the Plague of Justinian in 541 CE, there was little proof of its impact, emphasized the research.

But scientific advances allowing the recovery and sequencing of ancient DNA have shed light on how the bacterium had been infecting people since at least the Neolithic period.

As genomic evidence recovered up until now had been from colder regions, Neumann and his team decided to remedy the lack of information regarding the pathogen’s impact on ancient societies in warmer climates, such as in the Eastern Mediterranean. They faced the additional challenge of the degradation of DNA in higher temperatures. But the cave on Crete is known for its cool and stable conditions, allowing the team to recover DNA in teeth from 32 individuals who died between 2290 and 1909 BCE.

The genetic data revealed the presence of Y. pestis in two individuals. Furthermore, in two other individuals, lineages were discovered of Salmonella enterica – a bacterium typically responsible for typhoid fever.The research suggests that both pathogens were possibly transmissible in Bronze Age Crete.

Many questions still remain regarding aspects of this research, as the lineages of the discovered pathogens are currently extinct.

The team believes that the lineage of Y. pestis they uncovered could not have been transmitted through fleas – as has been the case with the later evolved versions of the bacterium that was highly contagious in human populations. Fleas transmitted the bubonic version of the plague via a flea bite. However, in the case of the ancient pathogen the transmission route may have been totally different, the study claims. Pneumonic plague, transmitted via aerosols, is suggested as a likely scenario for that period.

The virulence and transmission routes of the S. enterica lineages discovered also remain a mystery.

"While it is unlikely that Y. pestis or S. enterica were the sole culprits responsible for the societal changes observed in the Mediterranean at the end of the 3rd millennium BCE, we propose that, given the [ancient] DNA evidence presented here, infectious diseases should be considered as an additional contributing factor; possibly in an interplay with climate and migration, which has been previously suggested," the researchers concluded in their paper.

The team is hoping that subsequent detailed genetic screening of more remains from the Eastern Mediterranean could help uncover more secrets about how the ancient civilizations had been impacted by the diseases.