Scientists have made a remarkable discovery hidden within the remains of mammoths that roamed Earth more than a million years ago.
An international team led by researchers at the Center for Paleogenetics in Sweden has uncovered microbial DNA preserved in both woolly and steppe mammoth fossils.
These traces represent the oldest host-associated bacterial DNA ever recovered and may shed light on diseases that once affected these Ice Age giants. The findings were recently published in Cell.
The Center for Paleogenetics, a collaboration between Stockholm University and the Swedish Museum of Natural History, analyzed microbial DNA from 483 mammoth specimens, with 440 of them sequenced for the very first time.
Among these samples was a steppe mammoth that lived about 1.1 million years ago.
Using advanced DNA sequencing and bioinformatics tools, the researchers were able to separate ancient microbes that lived in and on mammoths during their lifetimes from those that invaded their remains long after death.
“Imagine holding a million-year-old mammoth tooth and learning that it still contains traces of the ancient microbes that once lived with that animal,” says Benjamin Guinet, postdoctoral fellow at the Center for Paleogenetics and lead author of the study.
“Our results push the study of microbial DNA back beyond a million years, opening up new possibilities to explore how microbes evolved alongside their hosts.”
The analyses revealed six major groups of microbes that appeared repeatedly across time and geography. These included relatives of Actinobacillus, Pasteurella, Streptococcus, and Erysipelothrix.
Some of these bacteria may have been harmful. For example, a Pasteurella-like bacterium found in the study is closely related to a modern pathogen that causes deadly outbreaks in African elephants.
Since elephants are the closest living relatives of mammoths, this raises the possibility that mammoths may have suffered from similar infections.
The most extraordinary finding was the reconstruction of partial genomes of Erysipelothrix bacteria from the 1.1-million-year-old steppe mammoth specimen. This achievement marks the oldest known host-associated microbial DNA ever retrieved.
“Because microbes evolve so quickly, obtaining reliable DNA data across such immense timescales was like following a trail that kept changing,” explains Tom van der Valk, senior author of the study. “But our results show that ancient remains preserve more than just the host’s DNA—they can also tell us how microbes influenced adaptation, disease, and even extinction.”
Although it is difficult to know precisely how these microbes affected mammoth health, the research provides a rare glimpse into the ancient microbiomes of extinct species.
The evidence suggests that some microbial lineages coexisted with mammoths for hundreds of thousands of years, from the deep past until the final population of woolly mammoths disappeared from Wrangel Island only about 4,000 years ago.
“This work opens a new chapter in understanding extinct animals,” says Love Dalén, professor of evolutionary genomics at the Center for Paleogenetics. “We are no longer limited to studying the genomes of mammoths themselves—we can now begin to explore the microbial communities that shaped their lives.”
