THE plague epidemics They transformed history because they not only devastated human populations, but also altered entire ecosystems. The disease thrives in environments where animals live near and move with humans, which is common in breeding societies of Antiquity. Herds, as they moved between pastures and habitats, promoted cross-contact between humans, domestic animals, and wildlife. This mobility has created a invisible biological exchange network in which a simple transfer could carry bacteria hundreds of kilometers.
In this context, the plague behaved less like an isolated phenomenon than like a phenomenon inevitable consequence of the daily relationship between shepherds and animalswith movements that served as a bridge between regions. With this, the zoonotic diseases They could remain active for centuries, even before the existence of large cities or the urban fleas associated with the medieval plague.
The plague remained active for centuries thanks to the daily mobility of shepherds and animals
An international team has found the DNA of Yersinia pestis in a 4,000 year old sheep from the Arkaim siteproviding the first evidence of plague infection in a non-human host during the Bronze Age. The study, published in the journal cellshows that the plague was already circulating among domestic animals thousands of years before medieval pandemics and suggests that herds played a decisive role in the spread of the pathogen.
The research places the discovery in a period when the plague, before the Middle Ages, without being able to be transmitted by fleas, spread throughout Eurasia for more than 2,000 years. This primitive strain has intrigued scientists because of its persistence in such large areas with no known vector. The results of the study provide a key to understanding how it was able to remain active: the interaction between humans and animals in highly mobile livestock societies.
The archaeologist Taylor Hermesfrom the University of Arkansas, co-leads an ancient livestock DNA project that studies how domesticated species such as cows, goats and sheep spread from the Fertile Crescent. By analyzing samples from the Arkaim site, Hermes detected genetic remains of Y. pestis in a sheep bone discovered decades agoa finding he called a decisive sign. He explained that analyzing ancient DNA presents difficulties due to mixing with environmental and human material, but it also helps detect pathogens that have affected herds and their caretakers.
New excavations seek to clarify the role of livestock in the chain of contagion
The research continues with new excavations funded by the German Max Planck Society, which has awarded Hermès a €100,000 grant to continue collecting samples in the southern Urals. The objective is determine the true extent of infections and locate possible natural reservoirs of the bacteria. The team hopes to clarify the role of livestock in transmission and to verify whether the plague is sustained through a cycle more complex than that of humans.
The DNA found in the Arkaim sheep constitutes an essential piece of evidence for understanding the dynamics of the disease. The similarity between this strain and others detected in humans from distant cultures indicates that the the plague was part of a vast epidemiological network. This genetic coincidence reinforces the hypothesis according to which the movements of herds and shepherds were a channel of propagation fundamental to the Bronze Age.
The researchers propose that in addition to people, domestic animals served as intermediate hosts between wild reservoirs and human communities. This interaction would have maintained the circulation of the pathogen even without specialized vectors, extending its presence in Eurasia for millennia. This discovery also constitutes a warning applicable today: when human activities modify stable ecosystems, Conditions arise that can reactivate old illnesses or promote new ones.
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