Science | biology
Scientists recreate an ecosystem with mastodons, reindeer and hares on the shores of the Arctic from ancient DNA trapped in clay and quartz
European and American scientists have discovered in the subsoil of northern Greenland a lost world from 2 million years ago that stars today on the cover of the magazine ‘Nature’. They have done so using fragments of environmental DNA thanks to which they have identified an ancient open boreal forest –with poplars, birches and thujas– in which mastodons, reindeer, hares, lemmings and geese lived on the shores of a sea with corals, horseshoe crabs and green algae. Environmental DNA is the DNA extracted from samples of soil, water, sediments, air… that contains genetic material from multiple species.
So far, the oldest DNA fragments recovered dated back a million years and had been extracted from a Siberian mammoth bone. The material recovered in Greenland by the group led by Eske Weillerslev, from the University of Cambridge, and Kurt Kjær, from the Center for Geogenetics of the Lundbeck Foundation at the University of Copenhagen, doubles that age and comes from 41 samples of clay and quartz.
Two researchers take sediment samples in Greenland. /
“DNA can degrade rapidly, but we’ve shown that, under the right circumstances, we can now go further back in time than anyone dared to imagine,” says Kjær. “These samples were found buried deep in sediments that accumulated over 20,000 years. The sediment ended up being preserved in ice or permafrost and, most importantly, it was not disturbed by humans for 2 million years.”
a warmer world
The DNA samples, of millionths of a millimeter, were taken in the Copenhagen Formation, a sediment deposit almost one hundred meters thick located at the mouth of an Arctic fjord, north of Greenland. Two million years ago, the climate there ranged from arctic to temperate, and it was 10 to 17 degrees warmer than today. Among the animals identified by the DNA fragments, the mastodon stands out, an extinct elephant-like proboscidean mammal that until now was not believed to have spread as far north as North America.
Forty Danish, British, French, Swedish, Norwegian, German and American scientists have participated in the research. The first thing they had to do was determine if there was hidden DNA in the clay and quartz, and if so, see if they could extract it for analysis. After obtaining the genetic material, they compared each tiny fragment with existing DNA libraries of animals, plants and microorganisms. Some were easy to identify as predecessors of current species, others could only be assigned to genera, and some have not been found at all in the data banks.
The musk ox is one of the few mammals living north of Greenland today. /
“The Cape Copenhagen ecosystem, which has no equivalent today, existed at temperatures considerably higher than today. At first glance, the climate seems to have been similar to what we expect on our planet in the future due to global warming,” says Mikkel Pedersen, from the Lundbeck Foundation Center for Geogenetics at the University of Copenhagen and one of the authors of the finding.
“The possibilities are endless”
This researcher recalls how “one of the key factors today is to what extent species will be able to adapt to the change in conditions derived from a significant increase in temperature. The data suggest that more species than previously thought may evolve and adapt to widely varying temperatures. But above all, these results show that they need time to do so. The current rate of global warming means that organisms and species do not have that time, so the climate emergency remains a huge threat to biodiversity and the world: extinction is on the horizon for some species, including plants and trees”.
The recreation of the ancient Greenlandic ecosystem has been possible thanks to new DNA extraction and sequencing equipment that has made it possible to locate and recover very small and damaged fragments, says Kjær. Looking to the future, he hopes that some ‘tricks’ of the plants in that ecosystem will serve to make current species more resistant to global warming. In addition, Weillerslev is confident that, although DNA generally survives better in cold and dry environments, having recovered it from clay and quartz opens the door to doing the same in Africa. “If we can start to explore ancient DNA in clay grains from Africa, we may be able to gather powerful information about the origin of many species, perhaps even about early humans and their ancestors. The possibilities are endless”.
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