Thousands of years ago, in the Eastern Mediterranean, several Bronze Age civilizations at about the same time
According to the traditional scientific vision, climate change was to blame, but the remains of those times shed light on another aspect of the fall of powerful civilizations.
In the remains excavated in an ancient burial onCrete, in a cave called Agios Charalambos, a team led by archaeogeneticist Gunnar Neumann of the Max Planck Institute for Evolutionary Anthropology in Germany has discovered genetic evidence for the existence of bacteria responsible for two of the most serious diseases in history - typhoid fever, fever and plague.
Therefore, according to the researchers,the widespread diseases caused by these pathogens cannot be discounted as a contributing factor to the social change so widespread from about 2200 to 2000 BC.
“The emergence of these two virulent pathogens inthe end of the early Minoan period in Crete, the scientists write in their paper, “highlights the need to re-examine infectious diseases as an additional factor that may have contributed to the transformation of early complex societies into the Aegean and beyond.”
Yersinia pestis is the bacterium responsible fortens of millions of deaths, most of which occurred during three devastating global pandemics. As catastrophic as this disease has been in the past centuries, its impact before the Plague of Justinian, which began in 541 CE e., it was difficult to assess. But recent technological and scientific advances, especially the recovery and sequencing of ancient DNA from old bones, are revealing part of this lost history.
It turned out that this bacterium has been infecting people since at least Neolithic times.
Last year, scientists discovered that the Stone Age hunter-gatherer likely died from the plague thousands of years before there was evidence that the disease had reached epidemic proportions.
However, the recovered genomic data is stillwere from colder regions. Little is known about its impact on ancient societies in warmer climates, such as those in the Eastern Mediterranean, primarily due to DNA degradation at higher temperatures.
So Neumann and his team went to study the bones recovered from a place in Crete known for its cool and stable climate.
They restored DNA in the teeth of 32 people who diedbetween 2290 and 1909 BC. The genetic data revealed the presence of quite a few common oral bacteria, as expected. Less expected was the presence of Y. pestis in two people and two lines of Salmonella enterica, the bacteria commonly responsible for typhoid fever, in two others. This discovery suggests that both pathogens were present and may have been transmitted in Bronze Age Crete.
But each of the discovered lineages is now extinct, making it difficult to determine how their infections may have affected communities.
The line of Y. pestis scientists discovered likely could not be transmitted by fleas—one of the traits that has made other lineages of bacteria so infectious among humans.
The flea is a carrier of the bubonic version of the plague;people become infected when the bacterium enters the lymphatic system through an insect bite. Therefore, the route of transmission for this ancient form of the bacterium may have been different and caused a different form of plague; pneumonic plague, which is transmitted, for example, by airborne droplets.
The researchers said that in the lineages of S.enterica also lacks key traits that contribute to the development of severe disease in humans, and the virulence and transmission routes of both pathogens remain unknown.
However, the discovery suggests that both pathogens were circulating; in regions of Crete with a high population density, they could have been somewhat rampant.
“Although it is unlikely that Y. pestis or S.enterica were the only agents of social change observed in the Mediterranean at the end of the 3rd millennium BC. e., the researchers write in their paper, “we suggest that, given the [ancient] DNA data presented here, infectious diseases should be considered as an additional factor; perhaps in interaction with climate and migration, as previously suggested.”
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