In the Bronze Age, domestic livestock could have acted as a link between wild animals and humans.
The plague of the Bronze Age, which struck Eurasia at the turn of the fourth and third millennia BC, may not have been carried by fleas, as in later periods, but by sheep.
This conclusion was reached by scientists who discovered DNA of the ancient plague pathogen - the bacterium Yersinia pestis - in the remains of a domestic sheep found in Arkaim, a settlement that existed during the Bronze Age in the southern Ural region. The DNA was extracted from the animal's tooth, whereas similar traces had previously only been found in human remains.
Genetic analysis showed that the sheep was infected with the same type of pathogen that affected humans in Eurasia thousands of years ago. However, the strains of plague from the Bronze Age differed from those that caused the medieval pandemic known as the "Black Death." They lacked a gene that allows the bacteria to survive inside fleas. Because of this, the authors of the study questioned the classic infection transmission model of "rodent - flea - human."
The new discovery suggests that in the Bronze Age, domestic livestock could have acted as a link between wild animals and humans. At that time, shepherds drove sheep, cows, and horses across vast pastures where they regularly came into contact with rodents, birds, and animal carcasses. Under such conditions, infection could occur through water, animal remains, or direct contact with representatives of the wild fauna.
However, the domestic animals themselves, according to scientists, were not a permanent "habitat" for the bacteria – this role was still played by wild rodents, which can carry pathogens for long periods in natural populations.
Research in modern plague foci shows that sheep can become infected with plague from marmots and then transmit the infection to humans.
