Researchers published their findings in the journal Cell on Friday.. Until recently, researchers didn't think RNA could survive this long.
“According to the textbooks, RNA is extremely unstable and mostly degrades within a few minutes of leaving a living cell,” said Mark Friedlander, a computational biologist at Stockholm University and author of the paper. “It's so amazing to find RNA that's 40,000 years old. Nobody really thought it was possible.”
Research can open new windows into history. Erez Eiden, a professor of biochemistry and molecular biology at the University of Texas Medical Branch who was not involved in the study, said scientists will continue to refine the methods used to study ancient RNA, as they have done for decades with ancient DNA analysis.
Aiden said he believes adding RNA analysis techniques to work on ancient genetics could redefine our understanding of the history of the biological world.
“We will be able to paint a much more complete and quantitative picture of the history of life on Earth,” Aiden said. “Suddenly we have the Rosetta Stone… These are hieroglyphs of ancient life.”
The discovery of RNA was made possible by Yuka's discovery in 2010, when members of the Yukaghir community discovered a mammoth in thawing permafrost near the Arctic Ocean. Yuka was found hidden on a cliff, partially mummified and still covered in a shaggy tangle of strawberry-blonde hair and bits of flesh that had remained pink until her discovery.
Paleontologists believe that Yuka was pursued and killed. Some evidence suggests that the creature was pursued by cave lions or maybe stabbed to death by modern people — there is evidence for both theories, and it is possible that each species contributed to the death of the animal.
The animal, as you might imagine in a world filled with cave lions, died under severe stress.
In fact, the new RNA study shows that signatures of physiological stress were contained in the RNA they profiled. The researchers used a sample of slow-twitch muscle fibers from the animal.
“We found that stress genes were active,” Friedlander said.
Mammoths are not the first ancient species to have their RNA analyzed. Researchers in 2019 reported that they profiled the RNA of a 14,300-year-old wolf or dog pup..
RNA is created from this DNA template during a process called transcription. During transcription, some genes are activated and some remain silent.
“This process is dynamic, and the genes expressed can change day and night,” Marmol Sanchez said.
The researchers also identified new forms of microRNAs—forms of RNA that control gene expression—in mammoths that are not known to exist in modern elephants.
Emerging RNA technology could help efforts to resurrect the woolly mammoth, said Aiden, who serves on the scientific advisory board of Colossal Biosciences, the company that plans to “resurrect” the woolly mammoth.
Friedlander said further research could also help researchers understand how some ancient viruses, such as those without DNA, evolved over time.
“If you want to know the history of RNA viruses like SARS-CoV-2, then we need to detect these RNA molecules in historical and ancient samples to understand how they evolved,” Friedlander said.
Ebola, HIV and influenza are viruses with RNA genomes.
More research is needed. For this study, the scientists examined 10 mammoths, but obtained a reliable RNA signal from only three of them, including Yuka, which turned out to be the best preserved specimen.
Since 2010, scientists believed Yuka was a female mammoth, but through RNA and DNA analysis, researchers determined that it was in fact a male mammoth.
Aiden said the RNA study highlights that scientists know surprisingly little about death and why some molecules degrade after an organism dies while others, like Yuki's, persist.
“Our theories about what happens to the physical material of an organism after it dies are very poor,” Aiden said. “How much of this information is still preserved and can remain legible after a long period of time? I think those are some of the most interesting questions.”
