The oldest DNA sheds light on 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.

2 million years 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 Nature magazine on Wednesday.

The combination of temperate and arctic trees and animals suggests a previously unknown type of ecosystem that has no modern equivalent – one that can act as a genetic road map about how different species can adapt to warmer climates, the researchers found.

The discovery was made by scientists from Denmark, who were able to find and extract 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 in 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 the extinct and the living animals, plants and microorganisms. The genetic material revealed dozens of other plants and creatures not previously found at the site based on what is known from fossil and pollen records.

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

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

While DNA from animal bones or teeth can shed light on an individual species, DNA from the environment has allowed scientists to build a picture of an entire ecosystem, said Professor Eske Willerslev, a fellow at St John’s College at the University of Cambridge and director of the Lundbeck Foundation Geogenetics Centre. . In this case, the ecological community reconstructed by the researchers exists when temperatures will 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) this very, very different ecosystem. People knew from the macrofossils that there were trees up there, some sort of forest, but DNA allowed us to identify many more taxa (types of living organisms),” said Villerslev, who led the study.

The researchers were surprised to discover that cedars similar to those found today in British Columbia would once have grown in the Arctic alongside species such as larch that now grow in the northernmost parts of the planet. They didn’t find DNA from carnivores, but they think carnivores — such as bears, wolves or even saber-toothed tigers — must have been present in the ecosystem.

Lav Dahlen, a professor at the Center for Paleogenetics at Stockholm University, who worked on the DNA study of the mammoth tooth but was not involved in this study, said the breakthrough discovery really “pushed the boundaries” in the field of ancient DNA.

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

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

Willerslev said the 16-year study is the longest project of its kind that 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 realized that the DNA was hidden in clay and quartz in the sediment and could be separated from it. The fact that the DNA bound to mineral surfaces is likely why it survived so long, the researchers said.

“We looked at these samples and failed and failed. They were given the name in the lab “the curse of the København formation,” Willerslev said.

Further study of environmental DNA from this period may help scientists understand just how different organisms can adapt to climate change.

“This is a climate that we expect to encounter on Earth due to global warming, and it gives us some insight into how nature will respond to rising temperatures,” he explained.

“If we can get this road map right, it really holds the key to how organisms can (adapt) and how we can help organisms adapt to a very rapidly changing climate.”