Discovery Of World’s Oldest DNA Breaks Record By One Million Years

Microscopic fragments of DNA were found in Ice Age sediment in northern Greenland. Using cutting-edge technology, researchers discovered the fragments are one million years older than the previous record for DNA sampled 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 GeoGenetics Center at the University of Copenhagen where Professor Kjær, a geology expert, is also based.

“A new chapter spanning one million 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,” so Professor Willerslev commenting the discovery.

“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.”

Professor Kjær adds that “the ancient DNA samples were found buried deep in sediment that had built-up over 20,000 years. The sediment was eventually preserved in ice or permafrost and, crucially, not disturbed by humans for two million years.”

The incomplete samples, a few millionths of a millimeter long DNA strings, were taken from the København Formation, a sediment formation almost 100 meters thick deposited in the shallow area of a fjord in Greenland’s northernmost point. The climate in Greenland at the time of sedimentation was between 10 to 17 degrees warmer than today, sustaining an ecosystem with no present-day equivalent, resembling a mix of temperate forest and mixed-grass prairie.

Detective work by 40 researchers from Denmark, the UK, France, Sweden, Norway, the U.S. and Germany, unlocked the secrets of the fragments of DNA. The process was painstaking – first they needed to establish whether there was DNA hidden in the sediment, and if there was, could they successfully detach the DNA from the mineral grains – like clay particles and quartz crystals – to examine it? The answer, eventually, was yes. The researchers compared every single DNA fragment with extensive libraries of DNA collected from present-day animals, plants and microorganisms.

The scientists discovered evidence of animals, plants and microorganisms including reindeer, hares, lemmings, birch and poplar trees. They even found that Mastodon, an Ice Age elephant, roamed as far as Greenland before later becoming extinct. Previously it was thought the range of the species did not extend from its known origins of North and Central America.

Some of the DNA fragments were easy to classify as predecessors to present-day species, others could only be linked at genus level, and some originated from species impossible to place in the DNA libraries of animals, plants and microorganisms still living today.

The findings have opened up a whole new period in DNA detection. Thanks to a new generation of extraction and sequencing equipment, researchers will be able to locate and identify extremely small and damaged fragments of genetic information in sediments considered previously unfit for DNA preservation.

“DNA generally survives best in cold, dry conditions such as those that prevailed during 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 may be possible that clay may have preserved ancient DNA in warm, humid environments in sites found in Africa,” Professor Willerslev concludes.

The paper “A 2-million-year-old ecosystem in Greenland uncovered by environmental DNA” is published in Nature. Material provided by the by University of Cambridge.