Most of us remember the Black Death, the Plague that ravaged the European continent and wiped out 60 million people. Recent studies found, however, that the ancestors of the pathogens that caused the plague go back way into the ancient times, through ancient Rome, Greece and Asia, through the earlier stages of human evolution, and it has affected the history of humanity more than we thought of. It was traced back around 3000 BC, and has spread through Eurasia.
The Black Death has been believed to have spread by fleas and rats that infected the humans and caused sinister death. But a study through the remains of humans from the Bronze Age discovered that even then, the Yersinia pestis, the strain that cause the said plague have been found in the DNA, giving a new insight that the Plague has affected our ancient ancestors.
However, certain observation shows that the virulent factor that was found in the bacteria that caused the Bubonic Plague was not exactly flea borne. This goes to show that the bacteria probably have evolved with mutations and is not exactly the same bacteria.
"Our data suggest that Y. pestis did not fully adapt as a flea-borne mammalian pathogen until the beginning of the 1st millennium BC, which precipitated the historically recorded plagues," The study authors of the article "Early Divergent Strains of Yersinia pestis in Eurasia 5,000 Years Ago" wrote. The said mutations are allegedly what enable the bacteria to somehow adapt themselves to fleas and had released the wrath of the epidemic to humans rather than between humans themselves.
The historical archives let us see that the human populations have seen through three major pandemics: the Plague of Justinian (541-544 AD to 750 AD), the Black Death (1347 to 1351 AD, 1700s) and the Pandemic in China (1850s through 1894, and the mid-1900s). It has greatly influenced the flow of history by wiping out waves of human population.
"Economic and political collapses have also been in part attributed to the devastating effects of the plague," the authors wrote. "The Plague of Justinian is thought to have played a major role in weakening the Byzantine Empire, and the earlier putative plagues have been associated with the decline of Classical Greece and likely undermined the strength of the Roman army."
Although several varieties of the disease occurred caused by the same bacteria Yersina Pestis such as the Bubonic, Pneumonic, and Septicemic plagues, the last one is the fatal disease with a mortality rate of 100%
