RNA from mummified woolly mammoth is the oldest ever recovered

In its final moments, Yuka the woolly mammoth may have been trying to outrun a cave lion.

That’s the conclusion of scientists who have just studied some of its genetic material.

Preserved in permafrost, Yuka’s hind legs bear scratches. His muscle tissue exhibits molecular evidence of stress. Molecules called RNA hint that the mammoth’s muscles may have been exhausted. That genetic material is the oldest RNA ever recovered. It also offers a peek into Yuka’s life some 40,000 years ago.

Scientists shared their findings in the January 8 issue of Cell.

Until now, the oldest RNA that biologists have decoded was about 14,000 years old. It came from a wolf. The new sample shows RNA may persist far longer than scientists had suspected.

RNA has long been considered DNA’s more delicate cousin. Textbooks suggest that RNA degrades almost immediately after death. So researchers who’ve studied Ice Age animals at a molecular level have tended to focus on DNA — not RNA. “I think people just assumed that it wouldn’t work [for RNA], so they haven’t tried,” says Love Dalén. He’s a biologist at Stockholm University in Sweden.

But the freezing environment that mummified Yuka’s remains proved perfect for preserving its RNA.

Mummified mammoth micro-molecules

DNA is the full genetic instructions for how to build an animal. RNA is the building manager. It tells cells exactly what to build and when.

Looking at RNA gives scientists a snapshot of a cell’s activity at a particular time. It shows which genes were switched on or off. That can tell them about the tissue the cell was in. It even can reveal an animal’s health.

Dalén and his colleagues analyzed RNA samples from 10 woolly mammoths. The tissue had long laid frozen in Siberian permafrost. Yuka’s RNA was preserved well enough for the team to uncover new biological details. Among them was evidence of cellular stress.

They also turned up molecules called microRNAs. These could play a role in making a mammoth a mammoth, Dalén says. For instance, mammoths and elephants have very similar genetic blueprints. The difference between the two species might lie in those microRNAs. These might control the activity of certain genes in one species and not the other.

The team’s new findings offer a roadmap for working with ancient RNA, says Emilio Mármol-Sánchez. He’s a geneticist at the University of Copenhagen in Denmark.

That roadmap could help uncover new details about the lives and deaths of the iconic animals that once roamed Earth’s icy plains.