The Hunt for the Oldest DNA

Niobe Thompson & Niobe Thompson / Canada & United States / 2024

Three million years ago, camels roamed through Greenland’s endless forests and our ancestors lived in the trees.It all came to an end with the Ice Ages. What died and what survived, as natural selection shaped the evolutionary tree during this epochal shift from hot to cold? Until now, scientists have known less about the natural world before the Ice Age than they did about the age of dinosaurs, which ended 64 million years ago. A new discovery is set to reveal this lost world, species by species.Led by Danish gene-hunter Eske Willerslev, a team of scientists for the first time in history is sequencing DNA from before the Ice Age. The picture that emerges is of a hot planet, when forests blanketed the Arctic and carbon levels matched those in our atmosphere today. Is this a portrait of our own climate future?

How can we travel back in time? Is there a time machine?
Yes. It’s DNA. It’s ancient DNA.
– Eske Willerslev

Three decades ago, the promise of ancient dinosaur DNA that inspired Jurassic Park went up in flames, as scientists realized their samples were contaminated. In the aftermath, no one could have predicted how ancient DNA science would rise from the ashes in spectacular fashion, transforming what we know about our human origins, the evolution of life, and the nature of distant lost worlds.

At that time, a 20-year-old Danish fur trapper returned home from Siberia and enrolled in biology classes. What followed became one of the most remarkable careers in science, a career that perfectly tracks the resurrection of ancient DNA science. The fruits of his work sparked a scientific revolution. Now, he is turning the page on the next chapter in genetic research. This is the story of how very old genomes are re-writing our understanding of life on Earth, following the inspiring career of one of its central authors: gene hunter and evolutionary biologist Eske Willerslev.

Decades ago, Willerslev’s core insight was that living DNA is all around us, falling continually from living organisms. He calls it “dirt DNA”, and while others have fought for access to precious fossil bones, he has quietly invented ways to piece together entire genomes from the fragments lying in the ground below us.

While everyone else was looking for DNA in fossils, and discovering one species at a time… I was looking in the dirt for everything!
– Eske Willerslev

Willerslev’s core obsession was to recover DNA older than any yet recovered – to use ancient DNA as a time machine, opening a window on the deep past. Until now, the oldest DNA ever recovered was from a mammoth that lived 1 million years ago. Most scientists agreed that this was the hard outer limit of survival for molecules of DNA. But not Willerslev. 17 years ago, he began taking dirt samples from the most remote and forbidding corner of Greenland: an arctic desert called Cape Copenhagen, where the remnants of life from before the Ice Age littered the frozen ground. They were far older than one million years.

Today, Willerslev’s maverick move has paid off in a spectacular way, with the greatest discovery of his career. Smashing the 1-million-year limit, his team has recovered the DNA of a lush forest ecosystem, populated by surprising creatures that flourished in the High Arctic well over two million years ago. From the dirt of Cape Copenhagen, his team has reconstructed the genomes of nine land and sea animals, from fleas and lemmings to horseshoe crabs and big mammals. They have recovered the DNA of 102 plants, from mosses to cedar trees, and nearly 2000 other organisms, from bacteria to plankton. Many of these plants and animals are now extinct, and some have never been detected in the Arctic. He has even discovered the genetic fingerprints of mastodons, whose remains have until now never been found north of New England, 4000 kilometres to the south.

With exclusive access to the work of Willerslev’s team over many years, Hunt for the Oldest DNA brings viewers inside a breakthrough that signals a new era in DNA science. For the first time, we can use DNA to travel back millions of years and piece together the ecosystems of lost worlds. Using exquisite 3D animation, we visit the weird Arctic forests that blanketed the Arctic before the Ice Age, where the sun never set for months on end and where the ancestors of bears, camels, beavers and horses survived 24-hour darkness through the long Arctic winter.

These creatures lived in the Pliocene: the last hot epoch on Earth, when Arctic temperatures were 20 degrees Celsius warmer than today. In a final twist, we learn how much this strange lost world aligns with our own. The Pliocene was the last time atmospheric carbon reached the levels in our atmosphere today. Willerslev’s ancient DNA is giving us a glimpse of our climate future. Could the genetic codes of life in the Pliocene give us the tools to survive what is to come?