Wednesday, March 22

The oldest DNA reveals what life was like in a Greenland 17 degrees warmer two million years ago

Two-million-year-old DNA has been identified for the first time, which “will change the rules of the game” of evolution, admit the authors of this study published in the journal Nature.

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They have achieved this thanks to the discovery of microscopic fragments of environmental DNA in Ice Age sediments in northern Greenland. The development of current technology has made it possible to define that they are a million years older than the previous record, coming from DNA extracted from a siberian mammoth bone.

This genetic information has been used to map an ecosystem from two million years ago that endured extreme climate change. The researchers hope that the results can help predict the long-term environmental consequences of the current climate emergency.

“A new chapter spanning another million years of history has finally opened, and for the first time we can directly observe the DNA of an ecosystem from so far back in time,” says Eske Willerslev, co-leader of the research at St John’s College of the University of Cambridge (United Kingdom).

Sediment at the mouth of a fjord

The incomplete samples, only a few millionths of a millimetre, were obtained from the København Formation, a sediment deposit almost 100 meters thick located at the mouth of a fjord in the Arctic Ocean, at the northernmost point of Greenland. In all, they collected 41 useful samples found hidden in the clay and quartz.

“The ancient DNA samples were found buried deep in sediment that had accumulated [en aquella época] for 20,000 years. The sediment was ultimately preserved in ice or permafrost and, most importantly, was not disturbed by humans for two million years,” says Kurt H. Kjær, who also co-leads the work from the Center for Geogenetics in the Lundbeck Foundation at the University of Copenhagen (Denmark), of which Willerslev is director.

Greenland’s climate at that time was between 10 and 17 degrees warmer than it is today. Sediment was accumulating meter by meter in a shallow bay. “DNA can degrade rapidly, but we have shown that, under the right circumstances, we can go further back in time than anyone dared to imagine,” Willerslev said.

Tracks of reindeer, lemmis and even mastodons

The scientists discovered evidence of animals, plants, and microorganisms, such as reindeer, hares, lemmings, and birch and poplar trees; They even found that the mastodon, an Ice Age mammal, made it as far as Greenland before going extinct. The range of these elephant-like animals was previously thought not to have extended as far as Greenland from their known origins in North and Central America.

The research work carried out by 40 researchers from Denmark, the United Kingdom, France, Sweden, Norway, the United States and Germany allowed the secrets of the DNA fragments to be revealed. The process was painstaking: they first had to determine if there was hidden DNA in the clay and quartz, and if it did, they could separate it from the sediment for examination.

The answer, finally, was affirmative. The researchers compared each of the DNA fragments with extensive DNA libraries collected from living animals, plants, and microorganisms. Thus began to emerge a picture of the DNA of trees, shrubs, birds, animals, and microorganisms.

Some of the remains were easy to classify as predecessors of current species, others could only be related to the genus, and some came from species that were impossible to locate.

Samples from two million years ago also help academics gain insight into a hitherto unknown stage in the evolution of the DNA of a number of species that still exist today.

A milestone made possible by technological advances

“The expeditions are expensive and many of the samples were taken in 2006, when the team was in Greenland for another project, and have been stored ever since. It was not until a new generation of extraction and sequencing equipment was developed that we have been able to locate and identify extremely small and damaged DNA fragments in sediment samples. This meant that we were finally able to map a two-million-year-old ecosystem,” says Kjær.

In reviewing ancient genetic remains from the Kap København Formation, they also found a wide range of microorganisms, including bacteria and fungi, which they continue to map. A detailed description of how the interaction between animals, plants and single-celled organisms worked biologically within the ancient ecosystem of the northernmost point of Greenland will be presented in a future research paper.

It is now hoped that some of the two-million-year-old plant DNA “tricks” discovered could be used to help make some endangered species more resilient to a warming climate.

“The Kap København 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 W. Pedersen, co-first author of the paper and a researcher at the Lundbeck Foundation Center for Geogenetics.

New stage in DNA detection

One of the factors that arouse the most interest in this study is knowing to what extent species are capable of adapting to the change in conditions that is produced by a significant increase in temperature.

“The data suggests that there are more species that can evolve and adapt to highly variable 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 the trees,” warns Pedersen.

Researcher Kjær asserts: “It is possible that genetic engineering could imitate the strategy developed by plants and trees two million years ago to survive in a climate characterized by rising temperatures and avoid the extinction of some species, plants and trees. This is one of the reasons why this scientific breakthrough is so significant, as it could reveal how to try to counteract the devastating impact of global warming.”

DNA tends to survive best in cool, dry conditions, such as those that have prevailed most in the material at Kap København.

“Now that we have succeeded in extracting ancient DNA from clay and quartz, it is possible that clay has preserved ancient DNA in hot and humid environments in deposits found in Africa,” Willerslev predicts, adding: “If we can start to explore the Ancient DNA in clay grains from Africa, we may be able to piece together groundbreaking information about the origin of many different species, perhaps even new insights into early humans and their ancestors; the possibilities are endless”.