Scientists have succeeded in extracting the world's oldest ribonucleic acid (RNA) from the extinct woolly mammoth (Mammuthus primigenius). RNA is genetic material that copies the information contained in deoxyribonucleic acid (DNA) and is used to synthesize proteins. It is expected to help reveal what actually synthesized proteins in the mammoth's genes. In particular, the possibility has been raised that traces of viral infection remaining in extinct animals could also be found using the same method.
A research team led by Professor Love Dalén of the Center for Palaeogenetics at Stockholm University said it had "for the first time successfully isolated and sequenced 40,000-year-old RNA molecules from Yuka, an Ice Age woolly mammoth," in Cell on the 14th (local time). The team said the study shows that RNA, as well as DNA and proteins, can be preserved for a very long time.
◇ RNA, whose lifespan is only a few hours, confirmed after 40,000 years
Yuka was discovered in 2010, frozen as if in life in the Siberian permafrost. This specimen is considered the most perfectly preserved of all woolly mammoths found to date. Yuka was thought to be a young female, about 6 to 8 years old, that died after being attacked by a cave lion about 40,000 years ago.
Dalén's team succeeded in extracting RNA from Yuka's leg. This achievement nearly triples the previous record. The oldest RNA previously discovered was extracted from a wolf preserved in Siberian permafrost 14,000 years ago.
Emilio Mármol-Sánchez, the first author of the paper, said, "With RNA we can obtain direct evidence of which genes were active, allowing us to glimpse the final moments in the life of a mammoth that walked the Earth during the last Ice Age," adding, "This is information that cannot be obtained from DNA alone."
Living organisms copy part of the genetic information in DNA in the cell nucleus into RNA to make proteins that govern all desired life processes. In other words, if DNA is the overall blueprint of a building, RNA corresponds to the detailed blueprints that make the stairs or walls as needed. Knowing RNA means you can tell which among the genes the organism expressed.
Scientists have extracted DNA and proteins from mammoths frozen as in life in permafrost, but they had not properly confirmed RNA. DNA has a stable structure that can be extracted even from fossils more than 1 million years old, but RNA is not and breaks down quickly. Earlier, in 2023, Dalén extracted RNA from a specimen of the extinct thylacine (Thylacinus cynocephalus) and succeeded in reconstructing millions of bases, but that specimen was from 132 years ago.
◇ Gene regulation by microRNA also confirmed
The team also decoded the genetic information of the RNA. DNA and RNA have a backbone of sugar and phosphate to which four types of bases are connected. In this order they synthesize proteins and govern life processes. Decoding genes is the process of checking these base sequences.
The team identified a distinctive gene-expression pattern in the frozen muscle remnants of the leg. Not all of the more than 20,000 genes that actually synthesize proteins in the mammoth genome were expressed. The RNA molecules detected this time encoded proteins with key functions in muscle contraction and metabolic regulation under stress conditions. The team said, "We found traces of cellular stress, which is not surprising considering previous research indicating that Yuka was attacked by cave lions just before death."
The team also found numerous RNA molecules that regulate gene activity in the mammoth muscle sample. MicroRNAs, short-stranded RNAs, do not synthesize proteins; they attach to other RNAs and block protein synthesis. They are, in a sense, a gene-regulatory device.
Marc Friedländer, a co-corresponding author and professor in the Department of Molecular Biosciences at Stockholm University, said, "MicroRNA, an RNA that does not encode proteins, was among the most intriguing findings we obtained," adding, "Muscle-specific microRNAs found in mammoth tissue are direct evidence of gene regulation occurring in real time at an ancient point."
In addition, this study also corrected Yuka's sex identity. Combining DNA and RNA analyses, the team said it was confident that Yuka was actually male. Dalén said, "Although Yuka is well preserved for a 40,000-year-old fossil, it is not complete, so it is not easy to determine an individual's sex based on morphology alone."
◇ Hopes for contributions to ancient virus research
The woolly mammoth once roamed the glacial plains of Eurasia and North America, perfectly adapted to life during the last Ice Age (about 115,000 years ago to 11,500 years ago). With thick fur, curved tusks, and imposing size, they grazed on the vast steppe spanning the Northern Hemisphere. However, they gradually disappeared due to climate change as temperatures rose, and the last small herd survived on an isolated Arctic island until 4,000 years ago.
Finding genetic material from extinct animals could also help overcome today's infectious diseases. This is because we can identify bacteria or viruses that infected animals in the past, retrace their evolutionary paths, and predict what mutations might occur in the future.
Indeed, in September, Dalén reported in Cell that DNA from bacteria had been found in tooth and bone fossils of a 1.1 million-year-old mammoth. Analysis showed that there were six bacterial groups that consistently coexisted with mammoths, including Pasteurella and Streptococcus, which today are known to cause diseases in livestock or elephants.
This study expanded ancient pathogen analysis targets to RNA viruses. Dalén said, "Our findings show that RNA molecules can survive far longer than previously thought," adding, "This means that not only can we study which genes are activated in extinct animals going forward, but we can also sequence RNA viruses such as influenza or coronaviruses preserved in Ice Age remains."
However, the study did not detect viral RNA. Dalén said, "There will be several studies on Ice Age RNA viruses going forward," adding, "For example, there are a few Paleolithic bird carcasses that would be very interesting for avian influenza research."
References
Cell (2025), DOI: https://doi.org/10.1016/j.cell.2025.10.025
Cell (2025), DOI: https://doi.org/10.1016/j.cell.2025.08.003