Oldest ever plague genome found in Russia

Scientists discovered the bacterium Yersinia pestis in 3,800-year-old human remains in Samarra, Russia. This bacterium is known to have caused the bubonic plague. Researchers used genetic sequencing to analyze the samples and found that the presence of Yersinia pestis predates current estimates of the plague's lineage by about 1,000 years, placing it in the Bronze Age. The study suggests that there were at least two strains of the plague lineage at that time, challenging the previous belief of a single strain.

How much earlier do the findings predate current thinking on the plague's lineage?

What did researchers suggest about the strains of plague lineage present at the time?