When paleogeneticist Love Dalén first saw the remarkably preserved body of a juvenile woolly mammoth named Yuka lying on a lab table in eastern Siberia in 2012, he experienced what he calls a holy hell moment at seeing an animal that didn’t look like it died yesterday despite living 39,000 years ago during the last Ice Age. The young mammoth had been found thawing out of a permafrost cliff near the Siberian coastline with deep scratch marks on its hindquarters, suggesting it was either attacked by cave lions while alive or scavenged after death. Now in a groundbreaking paper published in the journal Cell, Dalén and his colleagues report they managed to extract something remarkable from that ancient mammoth: RNA molecules that typically survive mere minutes or hours, not millennia.
While DNA is like a recipe for how to make a mammoth, RNA are the messenger molecules that translate that recipe into actually building and operating the animal, instructing cells how and when to make proteins and determining what makes liver cells different from muscle cells. The team collected tissue samples from ten different mammoths including Yuka and painstakingly extracted RNA fragments that were either small to begin with or had broken down over time despite being frozen. Analysis of Yuka’s muscle tissue revealed RNA related to slow twitch muscle function and RNA produced in response to stress, consistent with an animal being chased by cave lions or stuck in mud trying to escape. The RNA also revealed something unexpected: genetic material from a Y chromosome, proving that Yuka was actually male despite Russians naming the mammoth female based on visual inspection of remains where critical parts were likely missing. The stunning proof of principle shows it’s possible to see which genes were active in a now extinct animal, with processes inside cells frozen in time for 40,000 years offering insights into what drove the species to extinction and potentially allowing scientists to study ancient RNA viruses like Ebola, COVID, and influenza.
