Oldest DNA sheds light on 2 million year old ecosystem that has no modern equivalent |  CNN

Oldest DNA sheds light on 2 million year old ecosystem that has no modern equivalent | CNN

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An Ice Age sediment core from northern Greenland has produced the oldest DNA sequences in the world.

The 2 million year old DNA samples revealed that the now largely lifeless polar region was once home to rich plant and animal life – including elephant-like mammals known as mastodons, reindeer, hares, lemmings, geese, birches and poplars, according to new research published in the journal Nature on Wednesday.

The mixture of temperate and arctic trees and animals suggested a hitherto unknown type of ecosystem that has no modern equivalent – one that could serve as a genetic roadmap to find out how different species might adapt to a warmer climate, the researchers found.

The discovery is the work of Danish scientists who were able to detect and recover environmental DNA – the genetic material released into the environment by all living organisms – in tiny amounts of sediment taken from the København formation at the mouth of an arctic fjord. Ocean at the northernmost point of Greenland, during a 2006 expedition. (Greenland is a self-governing country within Denmark.)

They then compared the DNA fragments with existing libraries of DNA taken from both extinct and living species. animals, plants and micro-organisms. The genetic material revealed dozens of other plants and creatures that had not previously been detected at the site based on what is known from fossils and pollen records.

“The first thing that blew our minds when we looked at this data is obviously this behemoth and its presence so far north, which is quite far north of what we knew to be its natural range,” said study co-author Mikkel Pedersen, assistant professor at the Geogenetics Center of the Lundbeck Foundation of the University of Copenhagen, during a press conference. .

It smashes the previous record for the world’s oldest DNA, set by research published last year on genetic material extracted from the tooth of a mammoth that roamed the Siberian steppe more than a million years ago. years, as well as the previous record of DNA from sediments.

An artist's reconstruction of what the Kap København Formation in northern Greenland might have looked like 2 million years ago.

While DNA from animal bones or teeth can shed light on an individual species, environmental DNA has allowed scientists to form a picture of an entire ecosystem, said Professor Eske Willerslev, a member of the St John’s College, University of Cambridge and Director of the Lundbeck Foundation. Geogenetics Center. In this case, the ecological community reconstructed by the researchers existed when temperatures would be between 10 and 17 degrees Celsius warmer than Greenland is today.

“Only a few plant and animal fossils have been found in the area. It was super exciting when we got the DNA back (to see) this very, very different ecosystem. People knew from macrofossils that there had been trees, some kind of forest up there, but DNA allowed us to identify a lot more taxa (types of living organisms),” Willerslev said, who conducted the research.

Researchers were surprised to find that cedars similar to those found in British Columbia today would have once grown in the Arctic alongside species like larch, which now grow in the northernmost regions. of the planet. They found no carnivore DNA, but believe that predators – such as bears, wolves or even saber-toothed tigers – must have been present in the ecosystem.

Love Dalen, a professor at Stockholm University’s Paleogenetics Center who has worked on researching the DNA of mammoth teeth but was not involved in this study, said the groundbreaking discovery truly “pushed the boundaries” of the field of ancient DNA.

“It’s a really amazing paper!” he said over email. “It can tell us about the composition of ecosystems at different points in time, which is really important for understanding how past changes in climate have affected biodiversity at the species level. This is something that animal DNA cannot do.

“Furthermore, the findings that several temperate species (such as the spruce and mastodon relatives) lived at such high latitudes are exceptionally interesting,” he added.

A close-up of organic matter in the coastal deposit of the Kap København Formation in northern Greenland.

Willerslev said the 16-year study was the longest such project he and most of his team of researchers have ever been involved in.

Extracting the fragments of genetic code from the sediment took a lot of scientific detective work and several painstaking attempts – after the team first established that the DNA was hidden in clay and quartz in the sediment and could be detached from it. The fact that the DNA bound to mineral surfaces is likely why it survived so long, the researchers said.

“We revisited those samples and we failed and we failed. They got the name in the lab from the “curse of the København formation,” Willerslev said.

Further study of environmental DNA from this period could help scientists understand how various organisms could adapt to climate change.

“It’s a climate we expect to face on Earth due to global warming and it gives us an idea of ​​how nature will respond to rising temperatures,” he explained.

“If we can read this roadmap correctly, it really holds the key to how organisms can (adapt) and how can we help organisms adapt to a very rapidly changing climate.”

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