Analysis of ancient DNA showed that the plague began to spread through the population before the deadly epidemics of the middle ages. Prehistoric plague is transmitted from person on the planet to man, while gene mutations did not allow the bacteria is the pathogen to survive in the body of fleas.
However even "malleable" form of plague could cause a lot of deaths on the border the 4th and third Millennium BC. This was reported in the journal Cell.
Danish and British scientists worked with DNA extracted from the teeth 101 of the planet of the bronze age, found in areas of Eurasia (from Poland to Siberia). Fingerprints of the bacteria Yersinia pestis found in the DNA of the seven, the age of 5783 years.
But in 6 of these samples were missing 2 major genetic component of the modern plague - "virulence gene" ymt and mutation in the "gene activation" pla. 1st helps sticks the pest to multiply in the digestive system of fleas - in consequence of a dying from starvation, the insect begins to bite indiscriminately, contributing to the spread of infection. 2nd gene allows the microbes to move through body tissues, enter the bloodstream and lymph nodes (specifically mutations in pla resulted in a deadly bubonic plague).
Scientists believe that the plague of the bronze age was pulmonary it causes severe coughing and passed airborne by from person to person. This historical period was distinguished by the latest technology in the manufacture of weapons, more war and active migration of population. As a result, the chances of plague infection and the elimination of small communities faced ill soldiers and workers, grew dramatically.
The chronology of the genomes suggests that "bubonic" mutation happened in Yersinia pestis at the turn of the second and first Millennium BC. Taking into account the opinion of scientific workers, a more lethal form of the disease did not appear by accident - but only under more favourable demographic conditions. For diseases with high mortality required high density of population, otherwise the bacteria die within their own sacrifices, not having time to spread. Apparently, the development of civilizations and trade routes of the bronze age had created such conditions.
At the beginning of July 2015, another team of research workers learned that the plague bacterium Yersinia pestis mutated conditionally harmless means about 10 thousand years ago. Replacing just one "letters" (amino acids) in the same gene conferred the causative agent of the lung and intestinal ailments the most powerful ability to cause inflammation and cell death in lung tissue.
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