Around 39,000 years ago, a woolly mammoth died in what is now Siberia, destined to be encased in ice and permafrost that would eventually preserve its body – down to its hair and muscles.
Now that mammoth, known as Yuka, is offering scientists a new look at the flow of genetic information in ancient creatures.
For the first time, scientists were able to extract and sequence woolly mammoth RNA from a sample taken from Yuka, giving researchers a window into when the extinct creature’s genes were turned on and off.
The mammoth samples are the oldest ancient RNA ever described by researchers. The researchers also profiled the animal’s DNA.
Unlike DNA, which contains Yuka’s genetic blueprint, RNA tells researchers which genes were being expressed on the day it died, providing a snapshot of what was happening in the animal’s cells at that particular moment.
“In this tissue, we are actually measuring the last minutes or hours of this mammoth’s life,” said study leader Emilio Mármolis Sánchez and a PhD student at the University of Copenhagen.
One of Yuka’s legs, illustrating the exceptional preservation of the lower leg after skin removal, which allowed the recovery of ancient RNA molecules. (Valery Plotnikov)
The researchers published their findings in the journal Cell on Friday. Until recently, scientists didn’t think RNA could survive that long.
“RNA, according to the textbooks, is very unstable and basically breaks down within minutes of being outside a living cell,” said the paper’s author Marc Friedländer, a computational biologist at Stockholm University. “It’s so amazingly surprising to find RNA that’s 40,000 years old. No one really thought that was possible.”
Research can offer new windows to the story. 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 will continue to improve methods for studying ancient RNA, just as they have been analyzing ancient DNA for decades.
Aiden said he believes that adding RNA analysis techniques to ancient genetic work could redefine our understanding of the history of the biological world.
“We will be able to paint a much more detailed and quantitative picture of the history of life on Earth,” Aiden said. “Suddenly we have the Rosetta Stone… It’s the hieroglyphics of ancient life.
The discovery of RNA was made possible by the discovery of Yuka in 2010, when members of the Yukagiri community discovered a mammoth in melting permafrost near the Arctic Ocean. Yuka was found hiding on a bluff, partially mummified and still covered in a shaggy mat of strawberry blonde hair and some flesh that remained pink until discovered.
Paleontologists believe that Yuka was chased and killed. Some evidence suggests that the creature was hunted by cave lions, or possibly carved up by modern humans—there is evidence for both theories, and it’s possible that each species contributed to the animal’s demise.
The animal, as you can imagine in a world full of cave lions, was under a lot of stress when it died.
In fact, the new RNA studies show that their profiled RNA contained signs of physiological stress. The researchers used a sample from the animal’s slow-twitch muscle fibers.
“We found that stress genes were active,” Friedländer said.
Laboratory work in ultra-clean laboratories at the Paleogenetics Center in Stockholm, where ancient RNA was extracted. (Courtesy of Jens Olof Lasthein)
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 in a process called transcription. During transcription, some genes are activated and some are silenced.
The process is dynamic and the genes expressed can change day and night, said Mármol Sánchez.
The researchers also identified new forms of microRNA — RNA that controls gene expression — in mammoths that are absent in modern elephants.
Emerging RNA technology could help eradicate woolly mammoths, said Aiden, who serves on the scientific advisory board for Colossal Biosciences, a company that plans to “resurrect” the woolly mammoth.
Friedländer said further studies could also help researchers understand how some ancient viruses, such as those without DNA, evolved over time.
“If you want to learn about the history of RNA viruses like SARS-CoV-2, we need to detect these RNA molecules in historical and ancient samples to basically learn how they evolved,” Friedländer said.
Ebola, HIV, and influenza are among the viruses that have an RNA genome.
More research is needed. For this study, the researchers examined 10 mammoths, but obtained a reliable RNA signal from only three of them, including Yuka, who was the best-preserved specimen.
Since 2010 scientists thought Yuka was a female mammoth, but using RNA and DNA analysis, researchers determined it was actually a male mammoth.
Aiden said RNA research shows scientists know surprisingly little about death and why some molecules break down after an organism dies and why some, like the one from Yuka, persist.
“Our theories about what happens to the body’s physical matter after it dies are very poor,” Aiden said. “How much of that information still survives and can still be read after a long time? I think those are some interesting questions.”
This article was originally published on NBCNews.com