Memories of the film “Jurassic Park” are awakened: Researchers find DNA that is around two million years old – almost twice as old as the previous record find from Siberia. But that could only be the beginning: researchers hope to discover genetic material from the even more distant past in the future.
Two million years ago, northern Greenland had lush landscapes instead of a polar desert like today. Now researchers have found DNA from that time from many different creatures. The genome is a million years older than the oldest found in frozen mammoth bones in the permafrost of Siberia.
The mini snippets come from animals, plants and microorganisms, including reindeer, rabbits, lemmings, geese, birches and poplars. The scientists hope that special genetic adaptations of the proven plants can be used to make today’s species more resistant to the current climate change.
Genetic traces of living beings can be found everywhere in the environment: they come from fallen hair and feathers, dander, faeces, pollen and many other things. In water and soil samples, the various animal species in the area can be identified solely from the DNA traces contained in them. One speaks of environmental DNA, also called eDNA – “e” from the English word “environmental”. Under certain conditions, ancient environmental DNA can also be tracked down and examined, especially in permanently frozen sediment.
For the first time, DNA from a past ecosystem can now be viewed directly so far back in time, says study leader Eske Willerslev of the University of Cambridge. ‘DNA can decompose quickly, but we have shown that given the right circumstances, we can go further back in time than anyone could ever have imagined,’ explains co-author Kurt Kjær from the University of Copenhagen.
The environmental DNA was found buried deep in sediments that took 20,000 years to form. “The sediment eventually became conserved in ice or permafrost and — crucially — was not disturbed by humans for two million years.”
The success was made possible by a new generation of devices for DNA processing and decoding, as the team led by Willerslev and Kjær reported in the journal “Nature”. The microscopic DNA fragments, measuring just a few millionths of a millimetre, were found in Ice Age sediments in northern Greenland. They come from the Cape København Formation, a nearly 100 meter thick sedimentary deposit in the mouth of a fjord in the Arctic Ocean at Greenland’s northernmost point.
The climate in Greenland then fluctuated between arctic and temperate and was 10 to 17 degrees warmer than today. The ecosystem was an open, so-called boreal forest with a mixed vegetation of poplar, birch and thuja trees as well as a variety of shrubs and herbs.
The late Pliocene and early Pleistocene epochs, 3.6 to 0.8 million years ago, had a climate similar to that projected for future warming, the study notes. The researchers hope their findings could help predict the long-term environmental consequences of ongoing global warming. They also hope that analyzes in much warmer regions will also be possible.
DNA generally survives best in cold, dry conditions, which prevailed for most of the time the material was deposited at Cape København, Willerslev explained. However, it is possible that ancient DNA was also preserved in clay in warm, humid environments, for example at sites in Africa. “If we can start studying ancient DNA in clay grains from Africa, we may be able to gather groundbreaking information about the origins of many different species – maybe even new insights into early humans and their ancestors – the possibilities are endless.”
Henrik Krehenwinkel from the University of Trier, who was not involved in the analysis himself, also believes that further “revolutionary new insights” are very possible. The successes achieved so far are primarily based on the major advances in sequencing technology, with which genetic material can be deciphered more and more quickly and cheaply. An end to the technical development is not foreseeable. Krehenwinkel does not see a time limit either. “Around ten years ago, experts still thought that it was not possible to go back much more than 100,000 years – now we are at two million.”
“If the conditions are right, DNA can be very stable,” explains the Trier environmental scientist. Permafrost is ideal because the molecule then hardly degrades chemically and because no microbes are active that would decompose the DNA very quickly. If it were actually possible, as suggested by Willerslev, to find and decipher ancient DNA in the tropics as well, this would offer immense potential for evolutionary insights. “Biodiversity has always been huge in tropical areas, and many species, including humans, have evolved in such regions,” says Krehenwinkel.
