TV Review: Hunt for the Oldest DNA

The documentary 'Hunt for the Oldest DNA' follows the groundbreaking work of Professor Eske Willerslev, an evolutionary biologist renowned for pioneering research in ancient DNA. While Professor Willerslev is the central figure, the programme also features insights from other evolutionary biologists, palaeontologists, and climatologists, illustrating how understanding the past can shape multiple scientific fields, especially our future. With a compelling blend of adventure, scientific breakthroughs, and personal struggle, the documentary presents an engaging exploration of the challenges and triumphs in environmental DNA research.

As the title suggests, the documentary's central premise is the pursuit of ancient DNA, pushing the limits of technology and scientific ingenuity to uncover prehistoric ecosystems. Historically, fossils were the primary means of studying extinct species, but advances in DNA extraction techniques have revolutionised the field. The programme highlights this shift, showcasing Professor Willerslev's relentless ambition to retrieve DNA from sediments rather than fossils, and ultimately reconstructing entire pre-glacial ecosystems from microscopic genetic remnants – ancient DNA.

Professor Willerslev's journey began with an unconventional idea. Inspired by an observation as mundane as a dog defecating in the rain, he hypothesised that DNA could persist in soil long after organic matter decayed. His proposal gained initial scepticism from experienced professors, and his idea was dismissed, but this did not stop him from pursuing the idea of 'dirt DNA'. This moment particularly resonated with me as his resilience in the face of rejection was inspiring, and his ability to think beyond traditional methods highlights his innovation as a scientist.

To test his hypothesis, Professor Willerslev's initial attempt to extract ancient DNA was from permafrost in Siberia, a promising environment due to the cold, which slows DNA degradation of poop and urine remnants of mammals from ice age. His team successfully retrieved genetic material from extinct species, including woolly mammoths and bison, dating back 400,000 years. This breakthrough not only confirmed his theory but also established the field of environmental DNA research, enabling scientists to reconstruct entire past ecosystems rather than focusing on individual species.

The documentary's narrative structure is compelling, blending historical context with personal stories and scientific breakthroughs. One of the key turning points is Professor Willerslev's exploration of Cape Copenhagen, Greenland, an environment so dry and cold that it theoretically could preserve DNA beyond a million years. This location, however, became known as the 'curse of Cape Copenhagen' within the ancient DNA research community, as repeated efforts to retrieve readable DNA proved fruitless for over a decade. Professor Willerslev candidly reflects on this challenging period, admitting that his relentless pursuit of results led to overworking his students, sometimes at the cost of their research careers. This self-reflective moment highlights the human side of scientific discovery – the immense pressure, sacrifices, and ethical dilemmas faced by researchers.

A significant turning point comes when one of Professor Willerslev's students, Dr Mikkel Winther Pederson from the University of Copenhagen, Denmark, proposed using shotgun sequencing – an approach that allows for the identification of much shorter DNA fragments, unlike previous techniques that required longer sequences. The documentary does an excellent job of explaining complex scientific concepts with accessible analogies and visuals. One particularly effective analogy compares shotgun sequencing to shredding War and Peace into short phrases and attempting to reconstruct the book by searching for matching phrases across a vast library.

This technological leap, made possible by advancements in computational power, finally allowed Professor Willerslev's team to reconstruct an ancient ecosystem from two-million-year-old DNA of the Pliocene epoch – a groundbreaking achievement that shattered previous records and that was recognised as one of the most significant scientific discoveries of 2022.

Beyond uncovering prehistoric ecosystems, the documentary makes a compelling connection between past climates and present concerns. The Pliocene epoch, which had CO2 levels similar to today, provides valuable insights into future climate change. Professor Willerslev's discoveries suggest that studying ancient genetic adaptations could help develop climate-resilient crops, a promising avenue for mitigating the effects of global warming. I particularly appreciated how the documentary linked these discoveries to real-world applications, making the research feel immediately relevant. Inspired by this, I found myself wanting to learn more about developing climate-resilient crops and their potential impact on food security.

Overall, 'Hunt for the Oldest DNA' is a fascinating documentary that balances scientific depth with personal stories behind the discoveries. Professor Willerslev's enthusiasm and determination make him a captivating protagonist, and the programme's engaging storytelling ensures even complex topics remain accessible. The blend of adventure, scientific rigour, and personal struggle makes this a must-watch for anyone interested in genetics, evolution, or climate science. The documentary ultimately leaves viewers with a sense of wonder – reminding us that 'a little bit of dirt contains the key to an entire living world.'

The documentary was made by Handful of Films and Tangled Bank Studios for PBS.