Oldest DNA sheds light on a 2 million-year-old ecosystem that has no modern parallel


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

The 2 million years old DNA samples revealed that the now largely lifeless Arctic was once home to rich plant and animal life — including elephant-like mammals known as mastodons, reindeer, hare, lemmings, geese, birch trees and poplars, according to new research published in the journal Nature on Wednesday.

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 for how different species might adapt to a warmer climate, the researchers found.

The finding is the work of scientists in Denmark who were able to detect and recover environmental DNA – genetic material released into the environment by all living organisms – in small amounts of sediment from the København Formation, in 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 DNA libraries collected from both extinct and living specimens animals, plants and microorganisms. The genetic material revealed dozens of other plants and creatures not previously discovered at the site based on what is known from fossils and pollen records.

“The first thing that surprised us when we looked at this data is clearly this mastodon 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, an assistant professor at the Lundbeck Foundation GeoGenetics Center at the University of Copenhagen, 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 the tooth of a mammoth that roamed the Siberian steppe more than a million years ago, as well as the previous record for DNA from sediment.

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

“Only a few fossils of plants and animals 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 macrofossils that there were trees, a kind of forest up there, but the DNA allowed us to identify many more taxa (types of living organisms),” said Willerslev, who led the study.

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

Love Dalen, 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 groundbreaking finding really “pushed the frontier” for the field of ancient DNA.

“This is a really great paper!” he said by email. “It can tell us about the composition of ecosystems at different times, which is very important for understanding how past climate changes have affected species-level biodiversity. This is something that animal DNA can’t do.”

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

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

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

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

“We looked at these monsters again and we failed and failed. They were dubbed in the lab the ‘curse of the København formation,'” Willerslev said.

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

“It’s a climate we’re going to be facing on Earth as a result of global warming and it gives us an idea of ​​how nature will respond to rising temperatures,” he explains.

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

The Valley Voice
The Valley Voicehttp://thevalleyvoice.org
Christopher Brito is a social media producer and trending writer for The Valley Voice, with a focus on sports and stories related to race and culture.


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