Researchers have discovered an ancient flea entombed in amber along with what may be a 20 million-year-old-ancestor to the Bubonic plague, which pushes back the deadly disease's origins much earlier than we used to think.
The bacteria called Yersinia pestis earned its notoriety in the 14th century when its arrival in Europe heralded the Black Death that would eliminate half the continent's population. Even after that initial outbreak subsided, the bacteria continued to ravage Europe with periodic epidemics of plague for over 400 years. Plague still exists today — the World Health Organization receives reports of hundreds of cases each year, although the disease isn't nearly as deadly as it once was.
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Based on modern genomic studies, scientists used to believe that plague bacteria only evolved in the past 20,000 years, but the discovery of a flea preserved in amber casts doubt on that assumption. The flea is 20 million years old, which means the bacteria clinging to its proboscis are equally ancient. While scientists can't determine with certainty what species the bacteria are, they bear a remarkable resemblance to modern strains of Yersinia pestis. Of the flea-transmitted bacteria that exist today, only Yersinia shares the "coccobacillus," or rod and sphere shapes, possessed by these ancient bacteria.
"If this is an ancient strain of Yersinia, it would be extraordinary," said George Poinar, Jr., an entomology researcher in the College of Science at Oregon State University and author of the paper. "It would show that plague is actually an ancient disease that no doubt was infecting and possibly causing some extinction of animals long before any humans existed. Plague may have played a larger role in the past than we imagined."