The researchers published their findings in the journal Cell on Friday. Until recently, researchers didn’t think RNA could survive that long.
“RNA, according to the textbooks, is extremely unstable and basically degrades within minutes of being outside a living cell,” said Marc Friedländer, a computational biologist at Stockholm University, an author of the paper. “It’s amazing to find RNA that is 40,000 years old. No one really thought this was possible.”
The investigation could offer new windows into history. Erez Aiden, a professor of biochemistry and molecular biology at the University of Texas Medical Branch who did not work on the study, said scientists would continue to improve the methods used to interrogate ancient RNA, as they have done for decades with the analysis of ancient DNA.
Aiden said he believes incorporating RNA analysis techniques into ancient genetics work 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 a Rosetta stone… These are the hieroglyphs of ancient life.”
The discovery of RNA was made possible by the discovery of Yuka in 2010, when members of the Yukagir community discovered the mammoth in melting permafrost near the Arctic Ocean. Yuka was found hiding on a cliff, partially mummified and still covered in a shaggy mop of strawberry blonde hair and some flesh that had remained pink until her discovery.
Paleontologists believe that Yuka was hunted and killed. Some evidence suggests that the creature was chased by cave lions or perhaps slaughtered by modern humans; There is evidence for both theories and it is possible that each species contributed to the animal’s end.
The animal, as you can imagine in a world full of cave lions, was under a lot of stress when it died.
In fact, new RNA research shows that the RNA they profiled contained signs of physiological stress. The researchers used a sample of the animal’s slow-twitch muscle fibers.
“We discovered that there were stress genes that were active,” Friedländer said.
Mammoths are not the first ancient species to have their RNA analyzed. In 2019, researchers reported that they had profiled the RNA of a 14,300-year-old wolf or dog pup.
RNA is created from that DNA template during a process called transcription. During transcription, some genes are activated and others are silenced.
The process is dynamic and the genes that are expressed can change between day and night, Mármol Sánchez said.
The researchers also identified new forms of microRNA (a form of RNA that controls gene expression) in mammoths that are not known to exist in modern elephants.
The RNA technology under development could help efforts to de-extinct the woolly mammoth, said Aiden, who serves on the scientific advisory board for Colossal Biosciences, a company that plans to “resurrect” the woolly mammoth.
Friedländer said further research could also help researchers understand how some ancient viruses, such as those that do not contain DNA, developed over time.
“If we 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 basically find out how they have evolved,” Friedländer said.
Ebola, HIV and influenza are among the viruses with RNA genomes.
More research is needed. For this study, the researchers examined 10 mammoths, but only obtained a reliable RNA signal from three of them, including Yuka, which was the best preserved specimen.
Since 2010, scientists have thought that Yuka was a female mammoth, but researchers determined that she was actually a male mammoth, using RNA and DNA analysis.
Aiden said the RNA research highlights that scientists know surprisingly little about death and why some molecules degrade after an organism dies and why some, like Yuka’s, persist.
“Our theories for understanding what happens to the physical material of an organism after it dies are very poor,” Aiden said. “How much of that information still survives and can still be readable after long periods of time? I think those are some of the interesting questions.”
