Beth Zaikenjpg Tiny fragments of environmental DNA found in Ice Age sediment in northern Greenland. Using cutting-edge technology, the researchers discovered that the fragments are a million years older than the previous record for a DNA sample from a Siberian mammoth bone. The discovery was made by a team of scientists led by Professor Eske Willerslev and Professor Kurt H. Kjær. Professor Willerslev is a Fellow of St John’s College, University of Cambridge and Director of the Lundbeck Foundation Center for Geogenetics at the University of Copenhagen, where Professor Kjær, an expert in geology, is also based. “A new chapter spanning a million extra years of history has finally opened and for the first time we can directly see the DNA of a past ecosystem so far back in time,” Professor Willerslev commented on the discovery. “DNA can degrade quickly, but we’ve shown that under the right conditions, we can now go further back in time than anyone would dare to imagine.” Professor Kjær adds that “the ancient DNA samples were found buried deep in sediment that had accumulated over 20,000 years. The sediment was ultimately preserved in ice or permafrost and, importantly, undisturbed by humans for two million years.” The incomplete samples, a few millionths of a millimeter long DNA sequence, were taken from the København Formation, a nearly 100-meter-thick sedimentary formation deposited in the shallows of a fjord at the northernmost tip of Greenland. The climate in Greenland at the time of deposition was between 10 and 17 degrees warmer than today, sustaining an ecosystem with no modern equivalent, resembling a mix of temperate forest and mixed-grass prairie. Detective work by 40 researchers from Denmark, the UK, France, Sweden, Norway, the USA and Germany unlocked the secrets of the DNA fragments. The process was painstaking – first they had to determine if there was hidden DNA in the sediment, and if there was, could they successfully extract the DNA from the mineral grains – such as clay particles and quartz crystals – to examine it? The answer, after all, was yes. The researchers compared each DNA fragment to extensive DNA libraries collected from present-day animals, plants and microorganisms. Scientists have discovered evidence of animals, plants and microorganisms, including reindeer, hares, lemmings, birches and poplars. They even discovered that Mastodon, an Ice Age elephant, roamed as far as Greenland before later disappearing. It was previously thought that the species’ range did not extend beyond its known origin in North and Central America. Some of the DNA fragments were easy to classify as ancestors of today’s species, others could only be linked at the genus level, and some came from species that were impossible to fit into the DNA libraries of animals, plants and microorganisms still living today. The findings have opened a whole new era in DNA detection. Thanks to a new generation of extraction and sequencing equipment, researchers will be able to identify and locate extremely small and damaged fragments of genetic information in sediments previously thought unsuitable for DNA preservation. “DNA generally survives best in cold, dry conditions, such as those that prevailed for most of the period since the material was deposited at Kap København. Now that we have successfully extracted ancient DNA from clay and quartz, it is possible that the clay has preserved ancient DNA in hot, humid environments at sites found in Africa,” Professor Willerslev concludes. The paper, “A 2-million-year-old ecosystem in Greenland not covered by environmental DNA,” is published in Nature. Material provided by Cambridge University.
