20-Million-Year-Old “Black Death” Ancestor Found In Flea In Amber

The oldest yet evidence of the presence in the world of the “Black Death” bacteria was recently isolated from a flea that was entombed in Amber around 20 million years ago, according to recent reports.

The “fossil” bacteria found is thought to be rather closely related to the bacteria thought to be responsible for the Black Death — Yersinia pestis. So, an ancient relative of the bubonic plague, in other words.


Interesting to consider the thought that the bacteria, responsible for wiping out half the population of Europe in the 14th century, and countless others elsewhere and at other times, has been around in fairly unchanged form for at least 20 million years. However old the ancestral line actually is, it certainly appears that it considerably predates the emergence of humans.

Here are some details on the finding:

Findings on this extraordinary amber fossil have been published in the Journal of Medical Entomology by George Poinar, Jr., an entomology researcher in the College of Science at Oregon State University, and a leading expert on plant and animal life forms found preserved in this semi-precious stone.

It can’t be determined with certainty that these bacteria, which were attached to the flea’s proboscis in a dried droplet and compacted in its rectum, are related to Yersinia pestis, scientists say. But their size, shape and characteristics are consistent with modern forms of those bacteria. They are a coccobacillus bacteria; they are seen in both rod and nearly spherical shapes; and are similar to those of Yersinia pestis. Of the pathogenic bacteria transmitted by fleas today, only Yersinia has such shapes.

“Aside from physical characteristics of the fossil bacteria that are similar to plague bacteria, their location in the rectum of the flea is known to occur in modern plague bacteria,” stated Poinar. “And in this fossil, the presence of similar bacteria in a dried droplet on the proboscis of the flea is consistent with the method of transmission of plague bacteria by modern fleas.”

Very notably, these findings are at odds with genomic research (as many archaeological records are…) — which suggests that flea-plague-vertebrate cycle evolved only arose in the past 20,000 years. This is microbial life that we’re talking about here though — an area that despite the bluster of some modern researchers is still quite hard to accurately model/predict.

Here’s more:

However, today there are several strains of Yersinia pestis, and there is evidence that past outbreaks of this disease were caused by still different strains, some of which are extinct today.

While human strains of Yersinia could well have evolved some 10,000 to 20,000 years ago, Poinar said, ancient Yersinia strains that evolved as rodent parasites could have appeared long before humans existed. These ancient strains would certainly be extinct by now, he said.

The complex mode of transmission of plague is also reflected in the flea seen in this fossil. When a flea feeds on a plague-infected animal, the Yersinia pestis bacteria taken up with the blood often form a viscous mass in the flea’s proventriculus, located between the stomach and esophagus. When this happens, the fleas can’t obtain enough blood, and as they attempt to feed again, bacteria are often forced back out through the proboscis and into the wound.

This blockage is in part what makes them effective vectors of the plague, and the dried droplets on the proboscis of the fossil flea could represent a sample of the sticky bacterial mass that was regurgitated.

“If this is an ancient strain of Yersinia, it would be extraordinary,” Poinar noted. “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.”

A couple of final notes here:

  • The Amber fossil containing the flea in question was mined in what’s now the Dominican Republic.
  • The flea species in question is of course long extinct, and very few of its type have been found in amber.
  • Rodent hair was also recovered from the same amber mine source.
  • Flea-like creatures date back to at least the time of the dinosaurs, and may have played a part in the mass extinction on the branch, according to some researchers.
  • The emergence of malaria and leishmaniasis very clearly dates to around the time that dinosaurs were beginning to decline.

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