A study in the journal Cell reported that researchers recovered and sequenced ribonucleic acid from Yuka, a juvenile woolly mammoth that died roughly 40,000 years ago in Siberia. The RNA, extracted from muscle tissue preserved in permafrost, doubled the age record for any recovered RNA and challenged long-held assumptions about how quickly the molecule decays.
RNA carries genetic instructions from DNA to the cell’s protein-making machinery but is far more fragile than DNA or proteins. Under continuous freezing, however, Yuka’s molecules remained intact enough for sequencing. Love Dalén’s team at Stockholm University adapted modern laboratory protocols to handle the fragmentary strands, retrieving much smaller, older molecules than had ever been analyzed.
Yuka, found in 2010 along the Oyogos Yar coast by members of the Yukagir community, had been radiocarbon-dated to about 40,000 years old. Field observations suggested a female, but DNA and Y-chromosome fragments confirmed the animal was male, between five and ten years old at death. Deep claw and cut marks on the hide hinted at an attack shortly before death, and molecular analyses revealed stress-related RNA transcripts in the tissue. “We found signs of cellular stress,” said Emilio Mármol-Sánchez, now at the Globe Institute in Copenhagen, according to Science Daily. He later called the dataset “a snapshot of the last minutes or hours of Yuka’s life,” according to El Mundo.
The team detected microRNAs not present in modern elephants, and rare mutations in several fragments verified their mammoth origin, explained Bastian Fromm of the Arctic University Museum of Norway in comments carried by Adnkronos. Out of ten mammoth specimens examined, only three yielded RNA; uninterrupted freezing proved essential because degradation requires liquid water.
Some biotechnology companies have pointed to such findings as steps toward bringing extinct species back, but Dalén urged caution: “I don’t think it’s possible to de-extinct any species, only to bring back certain internal and external characteristics,” he said.
The work showed that, under ideal conditions, RNA can persist for at least 400 centuries, giving scientists a new window into the gene activity of long-gone Ice Age animals.
The preparation of this article relied on a news-analysis system.