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Wednesday, Dec. 7, 2022 (Halifax, NS) Researchers have discovered microscopic fragments of DNA in sediment from the Ice Age in northern Greenland that date back two million years, breaking a long-standing record and ushering in a new chapter in the history of evolution.

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 ancient DNA has been used to map a two-million-year-old ecosystem, which weathered extreme climate change. Researchers hope the results could help predict the long-term environmental toll of today’s global warming.

The discovery was made by a team of scientists led by Eske Willerslev of the University of Cambridge and the Lundbeck Foundation GeoGenetics Centre and Kurt H. Kjaer of the Lundbeck Foundation.

"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," says Prof. Willerslev.

"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."

The results of the 41 usable environmental DNA, or eDNA, samples found hidden in clay and quartz are published today in Nature.

John Gosse, a professor in Dalhousie University's Department of Earth and Environmental Sciences and director of CRISDal (Cosmic Ray Isotope Sciences at Dalhousie) Lab, was asked to date the sediments through geochronometry, which is the measure of geological time to, for instance, date past meteor impacts, eruptions, earthquakes or, in this case, when sediment was deposited by a stream that no longer exists.

"The geochronometry was challenging because no single technique could provide a precise date for the deposition of sediment with the eDNA," says Dr. Gosse. "Combined, the dating methods suggest a most probable age of about two million years."

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 not disturbed by humans for two million years.

The incomplete samples, a few millionths of a millimetre long, were taken from the Kap København Formation, a sediment deposit almost 100 metres thick tucked in the mouth of a fjord in the Arctic Ocean in Greenland’s northernmost point. The climate in Greenland at the time varied between Arctic and temperate, and was between 10° to 17° C warmer than Greenland is today.

Scientists discovered DNA evidence of animals, plants and microorganisms, including reindeer, hares, lemmings, birch, herbs and poplar trees. Researchers even found that mastodon, an Ice Age mammal, roamed as far as Greenland before becoming extinct. Previously, it was thought the elephant-like animals' range did not extend as far as Greenland from North and Central America.

Detective work by 40 researchers from Denmark, the UK, France, Sweden, Norway, the U.S., Canada 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 clay and quartz, and if there was, could they successfully detach the DNA from the sediment to examine it. Eventually, the answer was yes.

The researchers compared every DNA fragment with extensive libraries of DNA collected from present-day animals, plants and microorganisms. A picture began to emerge of the DNA from trees, bushes, birds, animals and microorganisms.

The two-million-year-old samples will help academics build a picture of a previously unknown stage in the evolution of the DNA of a range of species still in existence today.

"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," Prof. Willerslev explained.

"If we can begin to explore ancient DNA in clay grains from Africa, we may be able to gather ground-breaking information about the origin of many different species – perhaps even new knowledge about the first humans and their ancestors. The possibilities are endless.”

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Images available here.

Author contacts:

John Gosse
Department of Earth and Environmental Sciences
Dalhousie University
Email: John.gosse@dal.ca

Kurt H. Kjaer
Faculty of Health and Medical Sciences
University of Copenhagen
Natural History Museum of Denmark
Phone: +45 30589730
Email: kurtk@sund.ku.dk
Website: https://globe.ku.dk/research/geogenetics/

Eske Willerslev
Department of Zoology
University of Cambridge
United Kingdom
Phone: +45 2875 1309
Email: ewillerslev@sund.ku.dk and ew482@cam.ac.uk
Website: http://www.geogenetics.ku.dk/ and www.zoo.cam.ac.uk

Media contact:

Alison Auld
Senior Research Reporter
Communications, Marketing and Creative Services
Dalhousie University
Cell: 1-902-220-0491
Email: alison.auld@dal.ca