Mammoth Remains Yield the Oldest Host-Associated Microbial DNA Yet

An international team of scientists has recovered microbial DNA more than a million years old from the remains of woolly and steppe mammoths, the oldest host-associated microbial DNA ever identified. The findings, published in the journal Cell on September 5, 2025, were led by researchers at the Centre for Palaeogenetics, a joint venture of Stockholm University and the Swedish Museum of Natural History, with Benjamin Guinet as lead author and Tom van der Valk as senior author.

The team analyzed 483 mammoth specimens and sequenced 440 of them for the first time, hunting not for the animals’ own DNA but for the genetic traces of the bacteria that lived in and on them. They found relatives of microbes such as Actinobacillus, Pasteurella, Streptococcus, and Erysipelothrix, some of which can cause disease, and reconstructed partial genomes of Erysipelothrix from a specimen about 1.1 million years old. The results suggest these microbial lineages persisted alongside mammoths for hundreds of thousands of years across wide geographic ranges.

“The findings, published in the journal Cell on September 5, 2025, were led by researchers at the Centre for Palaeogenetics, a joint venture of Stockholm University and the Swedish Museum of Natural History, with Benjamin Guinet as lead author and Tom van der Valk as senior author.”

The significance lies in pushing back the frontier of what ancient DNA can reveal. Until now, recovering the genetic signatures of an extinct animal’s microbes from such deep time was largely out of reach. Being able to study the microbes that lived with mammoths opens a path to understanding the diseases they faced and how their microbial companions may have influenced their biology, adaptation, and even their eventual extinction.

The researchers are appropriately cautious. Distinguishing genuinely ancient, host-associated microbes from later environmental contamination is a major challenge, and the team used careful authentication methods to support their conclusions. Some interpretations will firm up only with further work. Still, the study marks a real expansion of paleogenetics, showing that the deep past holds not just the genomes of vanished giants but the ghostly genetic fingerprints of the tiny organisms that shared their world.