International researchers have discovered the oldest microorganisms' genes ever found in the teeth and bone fossils of a mammoth from 1.1 million years ago. These microorganisms lived on the mammoth during its lifetime. They also captured clues of pathogens that could have caused diseases in the mammoth.
Love Dalén, a professor at the University of Stockholm's Centre for Palaeogenetics in Sweden, reported on the 3rd that he found microbial deoxyribonucleic acid (DNA) in mammoth remains that are more than 1 million years old. The research findings were published that day in the international journal 'Cell.'
Earlier, Professor Dalén's research team extracted 1 million-year-old DNA from three molars of a woolly mammoth discovered in northeastern Siberia. This was the oldest DNA found in a fossil. Based on this, they revealed that ancient mammoths already had characteristics that allowed them to endure the cold of the Ice Age.
Subsequently, the research team analyzed a total of 483 mammoth specimens, of which they decoded the genes of 440 for the first time. Among these, they identified bacterial genes from a plain mammoth specimen that is over 1 million years old. The research team distinguished between microorganisms that lived alongside the mammoth during its lifetime and those that invaded after its death using bioinformatic techniques.
The analysis revealed that there were six groups of bacteria that coexisted with mammoths consistently. This includes Pasteurella and Streptococcus, which are known to cause diseases in livestock and elephants today. Some microbial lineages appeared to have coexisted with mammoths from about 1 million years ago until the woolly mammoth went extinct approximately 4,000 years ago on Wrangel Island.
The researchers noted that bacteria related to Pasteurella, which caused a deadly epidemic in African elephant populations, were also found in mammoths, suggesting that since African elephants are the closest living relatives of mammoths, the mammoths were likely vulnerable to similar epidemics.
However, it is still difficult to determine the exact impact of individual microorganisms on mammoth health. This is due to the partial preservation of DNA and the rapid evolution of microorganisms, with ancient DNA being easily damaged.
The research team also restored part of the gene of the pathogen Erysipelothrix from the 1.1 million-year-old plain mammoth. This is the oldest record reported so far of microbial DNA found in a host.
The research team emphasized that these results could assist not only in simply finding traces of ancient bacteria but also in understanding mammoths' health and extinction processes. This opens a new window into what microorganisms extinct animals lived with and how these affected their survival and extinction. Professor Dalén remarked, 'This study opens a new chapter in understanding the biology of extinct species.'
References
Cell (2025), DOI: https://doi.org/10.1016/j.cell.2025.08.003