Two-million-year-old DNA from northern Greenland has revealed that the region was once home to mastodons, lemmings and geese, offering unprecedented insights into how climate change can shape ecosystems. The breakthrough in ancient DNA analysis pushes back the DNA record by 1m years to a time when the Arctic region was 11-19C warmer than the present day. The analysis reveals that the northern peninsula of Greenland, now a polar desert, once featured boreal forests of poplar and birch trees teeming with wildlife. The work offers clues to how species might adapt, or be genetically engineered, to survive the threat of rapid global heating. Prof Eske Willerslev of the University of Cambridge and the University of Copenhagen, said: “A new chapter spanning 1m extra years of history has finally been opened and for the first time we can look directly at the DNA of a past ecosystem that far back in time.” The fragments are 1m years older than the previous record for DNA sampled from a Siberian mammoth bone. “DNA can degrade quickly but we’ve shown that under the right circumstances, we can now go back further in time than anyone could have dared imagine,” said Willerslev. In future, similar techniques might be used to uncover new insights into the first humans and their ancestors, he added. Willerslev and colleagues worked for 16 years on the project, which resulted in the DNA of 41 samples found hidden in clay and quartz being sequenced and identified. The ancient DNA samples were found buried deep in the Kap København Formation, a sediment deposit almost 100 metres thick that built up over 20,000 years. The sediment, tucked in the mouth of a fjord in the Arctic Ocean in Greenland’s northernmost point, was eventually preserved in ice or permafrost and lay undisturbed by humans for 2m years. Extracting and analysing the DNA was a painstaking process that involved piecing together tiny fragments of genetic material that first needed to be detached from clay and quartz sediment. It was only the advent of a new generation of DNA sequencing techniques that allowed the scientists to identify and piece together extremely small and damaged fragments of DNA, through referencing extensive libraries of DNA collected from present-day animals, plants and microorganisms. A picture emerged of forests populated by reindeer, hares, lemmings and mastodons, aelephant-like ice age mammals that have previously only been found in North and Central America. The samples did not reveal any carnivores – probably because they were fewer in number – but the scientists speculated that there may have been ancient bears, wolves or sabre-toothed tigers. “We don’t know what was there, but probably something that ate mastodons and reindeers,” said Willerslev. The authors say it is encouraging that these species were able to thrive so far north in a region that would still have been cast into darkness for much of the winter, despite warmer temperatures. “The data suggests that more species can evolve and adapt to wildly varying temperatures than previously thought,” said Dr Mikkel Pedersen, of the Lundbeck Foundation GeoGenetics Centre at the University of Copenhagen and co-first author. However, the speed of global heating today means that many species will not have enough time to adapt, meaning that the climate emergency remains a huge threat to biodiversity. Willerslev and colleagues said studying ancient ecosystems could provide clues to how some species were genetically adapted to a warmer climate. “It is possible that genetic engineering could mimic the strategy developed by plants and trees 2m years ago to survive in a climate characterised by rising temperatures and prevent the extinction of some species, plants and trees,” said Prof Kurt Kjærr, of Copenhagen University and a co-author. “This is one of the reasons this scientific advance is so significant because it could reveal how to attempt to counteract the devastating impact of global warming.”