Ancient RNA Reveals Yuka the Mammoth Was Male

For many years, researchers assumed RNA would by no means survive the Ice Age.

Now, a group at Stockholm University has recovered authentic RNA from woolly mammoth tissues preserved in Siberian permafrost. The examine reveals that gene exercise could be learn from animals that died almost 40,000 years in the past.

Why does historical RNA from a woolly mammoth matter?

Ancient DNA has reshaped how researchers examine extinct animals. Genome knowledge from specimens as much as two million years outdated has helped reconstruct evolutionary relationships, inhabitants adjustments and previous environments. However, DNA solely reveals which genes an organism carried; it doesn’t present which genes have been energetic on the time of dying. That info is encoded in RNA, a molecule that displays gene exercise inside cells.

RNA was thought-about past attain for Ice Age analysis. It breaks down rapidly after dying and is delicate to enzymes that degrade it. The area has relied primarily on uncommon circumstances the place historic samples have been preserved in formalin or different fixatives, and makes an attempt to get well RNA from historical animals have produced restricted or low-quality knowledge.

The assumption was easy: RNA recovered from animals that lived tens of 1000’s of years in the past ought to now not exist.

Yet gene exercise knowledge would add an informative layer to paleogenomics. It can point out tissue sort, metabolic state and the stresses an animal skilled close to the top of its life. It might even reveal traces of historical RNA viruses in the identical tissue. Until now, this kind of proof has been lacking from Ice Age mammals as a result of researchers lacked each assured RNA restoration and a transparent technique to substantiate that any fragments have been genuine.

“We have previously pushed the limits of DNA recovery past a million years. Now, we wanted to explore whether we could expand RNA sequencing further back in time than done in previous studies,” stated senior writer of the brand new examine, Dr. Love Dalén, a professor in evolutionary genomics on the Centre for Paleogenomics in Stockholm University.

“We gained access to exceptionally well-preserved mammoth tissues unearthed from the Siberian permafrost, which we hoped would still contain RNA molecules frozen in time,” added lead writer Dr. Emilio Mármol, a postdoctoral researcher on the Centre for Paleogenomics in Stockholm University.

Recovering historical RNA from woolly mammoth tissue

Dalén and the group labored with 10 Pleistocene woolly mammoth samples. The set included pores and skin and muscle taken from animals, dated between 10,000–50,000 years outdated.

RNA portions have been low, however nonetheless measurable, and three people stood out for high quality: the well-known juvenile “Yuka” (dated to ~39,000 years outdated), the Oymyakon calf and a specimen nicknamed “Chris Waddle”.

Before inspecting gene exercise, the researchers confirmed the indicators have been genuine. The RNA matched mammoth and elephant sequences, confirmed the anticipated shortening with age and carried chemical harm patterns typical of historical RNA. Human contamination was additionally beneath 0.1%.

Yuka produced probably the most full transcriptome. The group detected 342 protein-coding RNAs and 902 noncoding RNAs, linked to muscle construction and power use.

“We found signs of cell stress, which is perhaps not surprising since previous research suggested that Yuka was attacked by cave lions shortly before his death,” stated Mármol.

Small RNAs gave much more perception.

“RNAs that do not encode for proteins, such as microRNAs, were among the most exciting findings we got,” stated co-author Dr. Marc Friedländer, a college lecturer at Stockholm University. “The muscle-specific microRNAs we found in mammoth tissues are direct evidence of gene regulation happening in real time in ancient times. It is the first time something like this has been achieved.”

“We found rare mutations in certain microRNAs that provided a smoking-gun demonstration of their mammoth origin. We even detected novel genes solely based on RNA evidence, something never before attempted in such ancient remains,” added co-author Dr. Bastian Fromm, an affiliate professor on the Arctic University of Norway.

One sudden end result got here from intercourse willpower. Earlier morphological descriptions labeled Yuka as feminine, but DNA and RNA reads from the Y chromosome confirmed that the animal was biologically male.

What historical RNA reveals about extinct animals

The outcomes present that RNA can persist for almost 40,000 years underneath extraordinarily steady situations, difficult the long-held view that RNA disappears quickly after dying.

“With RNA, we can obtain direct evidence of which genes are ‘turned on’, offering a glimpse into the final moments of life of a mammoth that walked the Earth during the last Ice Age. This is information that cannot be obtained from DNA alone,” stated Mármol.

“Our results demonstrate that RNA molecules can survive much longer than previously thought. This means it will also be possible to sequence RNA viruses, such as influenza and coronaviruses, preserved in Ice Age remains,” stated Dalén.

Not each specimen within the examine produced usable knowledge, suggesting that RNA preservation depends on uncommon situations and won’t be attainable in most historical samples. Some of the smallest fragments additionally stay tough to categorise with full confidence.

However, the examine gives a framework for validating historical RNA and coping with extremely fragmented knowledge, which will likely be helpful for future initiatives.

“Such studies could fundamentally reshape our understanding of extinct megafauna as well as other species, revealing the many hidden layers of biology that have remained frozen in time until now,” stated Mármol.

Reference: Mármol-Sánchez E, Fromm B, Oskolkov N, et al. Ancient RNA expression profiles from the extinct woolly mammoth. Cell. 2025:S0092867425012310. doi: 10.1016/j.cell.2025.10.025

This article is a rework of a press release issued by Stockholm University. Material has been edited for size and content material.