A new discovery has shed light on the mysterious past of the plague bacterium, Yersinia pestis, which has been wreaking havoc on human populations for thousands of years. An international team of researchers has recovered the first ancient genome from a Bronze Age domesticated sheep, providing crucial insights into the transmission and ecology of the disease in the ancient past.
The study, published in the journal Cell, reveals that the plague bacterium was transmitted to humans through infected fleas on rats during its most infamous form, the Black Death. However, scientists have long been baffled by how the illness persisted during the Bronze Age, when the genetic tool kit for later strains had not yet developed.
The researchers found the ancient Yersinia pestis genome in a 4,000-year-old sheep’s tooth at an archaeological site in Russia. This discovery allowed them to better understand the role of livestock in the spread of the disease throughout Eurasia. The study suggests that domesticated sheep served as a bridge between humans and infected wild animals, facilitating the transmission of the disease.
The findings have significant implications for understanding modern diseases and their evolution. The researchers believe that finding similar genetic tools in modern pathogens could provide insights into how they developed their current form. The discovery also highlights the importance of considering animal vectors in the spread of human diseases.
While the plague lineage from the Bronze Age is extinct, the bacterium still exists today in parts of Africa, Asia, and the western United States. However, cases are rare, with only 1,000 to 2,000 reported annually worldwide. The study serves as a reminder that animals can carry diseases transmissible to humans and emphasizes the need for caution when interacting with livestock and pets.
The researchers hope that further studies will uncover more animal hosts infected with ancient Yersinia pestis strains, providing a deeper understanding of the disease’s evolution and transmission. This breakthrough highlights the complex relationship between humans and animals in shaping the course of diseases throughout history.
Source: https://edition.cnn.com/2025/08/12/science/plague-livestock-transmission-black-death