Science

The oldest DNA illuminates a 2-million-year-old ecosystem that has no modern parallel

The oldest DNA illuminates a 2-million-year-old ecosystem that has no modern parallel

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An Ice Age sediment core from northern Greenland has yielded the world’s oldest DNA sequences.

The 2 million year old boy DNA samples revealed that the polar region, now largely lifeless, 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 Wednesday in the journal Nature. .

The mix of temperate and arctic trees and animals suggested a previously unknown type of ecosystem that has no modern equivalent: one that could act as a genetic roadmap The researchers found how different species could adapt to a warmer climate.

The find is the work of scientists in Denmark who were able to detect and recover environmental DNA (genetic material shed into the environment by all living organisms) in small amounts of sediment taken from the København Formation, at the mouth of ‘a fjord in the Arctic. Ocean at the northernmost point of Greenland, during a 2006 expedition. (Greenland is an autonomous country within Denmark.)

They then compared the DNA fragments to existing libraries of DNA collected from both extinct and living animals, plants and microorganisms. The genetic material revealed dozens of other plants and creatures previously undetected at the site based on what is known from fossils and pollen records.

“The first thing that struck us when we looked at this data is obviously this mastodon and its presence this far north, which is quite north of what we knew as its natural range,” said study co-author Mikkel Pedersen, assistant professor at the Lundbeck Foundation’s Center for Geogenetics in the University of Copenhagen, in a press conference. .

It beats 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, as well as the previous sediment DNA record.

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

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

The researchers were surprised to discover that cedars similar to those found in British Columbia today would once have grown in the Arctic alongside species such as larch, which now grow at the northernmost tip 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, professor at Stockholm University’s Center for Paleogenetics, who worked on DNA research from mammoth teeth but was not involved in this study, said the breakthrough finding really “pushed the envelope” of the ancient DNA field.

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

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

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

Willerslev said the 16-year study was the longest project of its kind that he and most of his team of researchers had ever been involved with.

Extracting the fragments of genetic code from the sediment required a great deal 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 separate from him The fact that the DNA had bound to the mineral surfaces was probably why it survived for so long, the researchers said.

“We went through these samples and we failed and failed. They were named in the lab the ‘Curse of the København Formation,'” Willerslev said.

Further study of environmental DNA from this time period could help scientists understand how they are different organisms can 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 get this roadmap right, it really holds the key to how organisms can (adapt) and how we can help organisms adapt to a very rapidly changing climate.”



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