In the last moments of Yuka, a well-preserved woolly mammoth, he may have been desperately trying to outrun a cave lion.
Scratches on the back of Yuka’s legs hint at a predator’s attack — and inside his ancient muscle tissue, researchers have found molecular traces of intense physical strain. Newly recovered RNA molecules suggest Yuka’s muscles were pushed to exhaustion. These RNA sequences, dating back roughly 40,000 years, are the oldest ever obtained, scientists report on November 14 in Cell.
Researchers have sequenced ancient RNA before, but never anything this old. Until now, the record belonged to RNA from a 14,000-year-old Pleistocene wolf. The new findings show that RNA can survive far longer than expected, says biologist Love Dalén of Stockholm University.
Traditionally, ancient-DNA studies have dominated Ice Age research. RNA, often depicted as the fragile counterpart to DNA, was thought to degrade almost instantly after an organism dies. “I think people just assumed it wouldn’t work,” Dalén says. “So no one really tried.”
Yet under exceptional conditions — such as the deep freeze that preserved Yuka in Siberian permafrost — RNA can endure for millennia.
If DNA provides the full blueprint of an organism, RNA acts like the foreman directing construction: it tells cells which proteins to make, when, and in what quantities. That makes RNA a snapshot of what a cell was actively doing at a given moment, explains geneticist Emilio Mármol-Sánchez of the University of Copenhagen. It can reveal tissue types, gene activity, and aspects of an animal’s health or stress.
Mármol-Sánchez, Dalén and their team examined RNA from 10 woolly mammoths whose tissues had remained frozen for thousands of years. Yuka’s RNA was especially well preserved, giving scientists new insights into the animal’s physiology. They detected markers of cellular stress, along with microRNAs — small regulatory molecules — that may have played a defining role in mammoth biology. Although mammoths and elephants share nearly identical genomes, differences in microRNA activity might help explain how one species became a cold-adapted Ice Age giant.
The study, Mármol-Sánchez says, provides a methodological template for retrieving and analyzing ancient RNA. And that could unlock a new dimension of knowledge about the lives, evolution and deaths of the iconic megafauna that once roamed the frozen landscapes of the Pleistocene.
