World's Oldest RNA Extracted From Woolly Mammoth

Scientists have taken an important step closer to understanding the mythical mammoths that roamed the Earth thousands of years ago.

For the first time ever, a research team has succeeded in isolating and sequencing RNA molecules from woolly mammoths dating back to the Ice Age. These RNA sequences are the oldest ever recovered and come from mammoth tissue preserved in the Siberian permafrost for nearly 40,000 years. The study, published in the journal Cell, shows that not only DNA and proteins, but also RNA, can be preserved for very long periods of time, and provide new insights into the biology of species that have long since become extinct.

"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," says the study's lead author Emilio Mármol, a postdoctoral researcher at the Globe Institute, University of Copenhagen. He collaborated with scientists from SciLifeLab and the Centre for Palaeogenetics - a joint initiative between Stockholm University and the Swedish Museum of Natural History.

Well-preserved mammoth tissue

For years, scientists have mapped mammoth DNA to reconstruct their genome and evolutionary history. But RNA - the molecule that reveals which genes are active - has until now remained out of reach. The widespread belief that RNA is too fragile to survive more than a few hours after death may have discouraged researchers from examining these information-rich molecules in mammoths and other long-extinct species.

In 2010, archaeologists discovered an almost 40,000-year-old and exceptionally well-preserved mammoth that had been hidden in the Siberian permafrost. It was found near the town of Yukagir and was therefore named Yuka. Researchers estimate that Yuka was between six and eight years old when it died. Despite its young age, it stood three meters tall and weighed five tons. The juvenile mammoth has since provided scientists with new insights into the species - partly because its DNA was intact. (Source: Illustreret Videnskab)

"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," says Emilio Mármol.

"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," says Love Dalén, Professor of Evolutionary Genomics at Stockholm University and the Centre for Palaeogenetics.

RNA found in young mammoth

The researchers were able to identify the old RNA in frozen muscle remains from Yuka, a juvenile mammoth that died almost 40,000 years ago. In the future, the researchers hope to conduct studies that combine prehistoric RNA with DNA, proteins, and other preserved biomolecules.

"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", says Emilio Mármol.

The article "Ancient RNA expression profiles from the extinct woolly mammoth" is published in the journal Cell.