Scientists Extract World’s Oldest RNA from Woolly Mammoth Remains

A research team has successfully extracted and sequenced the world’s oldest known RNA from a woolly mammoth named Yuka, who was frozen in the Siberian permafrost approximately 40,000 years ago. Discovered by tusk hunters in 2010, Yuka exhibited remarkable preservation, with intact skin, muscle tissue, and even reddish hair. This groundbreaking study, conducted by scientists at Stockholm University, reveals new insights into the biology of this long-extinct species.

The research team meticulously processed samples of Yuka’s muscle and other tissues, employing specialized chemical treatments to isolate RNA fragments. Traditionally, RNA is considered too fragile to survive for extended periods, leading many researchers to believe that sequencing such ancient molecules was impossible. Most previous attempts to analyze ancient RNA have been thwarted by degradation or contamination.

Groundbreaking Methods Reveal New Biological Insights

By adapting RNA-handling techniques to accommodate the unique challenges of ancient, fragmented molecules, the researchers accessed previously unattainable information, including the activity of genes at the time of Yuka’s death. Evidence suggests that Yuka experienced significant stress as it succumbed to a cave lion attack, with muscle tension and distress signals evident in the data.

Emilio Mármol, the study’s lead researcher, emphasized the importance of RNA analysis: “With RNA, you can access the actual biology of the cell or tissue happening in real time within the last moments of life of the organism.” He added that while DNA provides valuable information about an organism’s evolutionary history, RNA offers a “full picture of the whole pipeline of life” from DNA to proteins.

Combining RNA and DNA analyses led to the surprising discovery that Yuka, initially thought to be a juvenile female based on anatomical inspections, is genetically male. Both RNA and DNA contained sequences from the Y chromosome, which is exclusive to males. The implications of this finding remain unclear, as Mármol noted, “We did not find any evidence with our data supporting impaired genital development.”

Potential for Future Research on Extinct Species

While scientists have successfully analyzed DNA from specimens dating back up to 2 million years, RNA sequencing has faced significant obstacles, with successful analyses previously limited to samples no older than 14,000 years. RNA typically degrades rapidly after an organism dies, but freezing conditions can preserve it, as demonstrated in Yuka’s case.

The successful extraction of ancient RNA opens new avenues for research. According to evolutionary biologist Beth Shapiro, “Knowing that RNA is preserved means that we have another tool to use to reconstruct and validate ancient genomes.” This method could also facilitate examinations of other long-extinct species, potentially revealing the presence of RNA-based viruses, such as influenza or coronaviruses, at the time of their demise.

Mármol expressed enthusiasm for future research opportunities, particularly with species like Tasmanian tigers and woolly mammoths. He also highlighted the potential of studying extinct species such as the dodo, cave lions, and dire wolves. The optimal candidates for RNA extraction are those that lived in cold, dry environments, as warmer climates are less likely to preserve such delicate materials.

In addition to providing insights into extinct species, this approach could enhance our understanding of currently endangered species. Mármol stated, “There is probably a great room to explore the biology and evolution of currently endangered species back when they were more numerous.” By incorporating RNA into paleogenetic studies, researchers aim to gain a more comprehensive understanding of the factors contributing to population declines.

The extraction and analysis of ancient RNA, combined with DNA and protein studies, mark a significant advancement in paleogenetics. This pioneering research not only enhances our understanding of lost ecosystems but also holds the potential to inform conservation efforts for today’s threatened species.