The oldest DNA sheds light on a 2-million-year-old ecosystem with no modern parallel

The oldest DNA sheds light on a 2-million-year-old ecosystem with no modern parallel
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An Ice Age sediment core from North Greenland has yielded the world’s oldest DNA sequence.

2 million years old DNA samples A new study published in the journal Nature on Wednesday revealed that the now largely lifeless polar region was once home to a rich array of plant and animal life, including elephant-like mammals known as mastodons, reindeer, rabbits, lemmings, geese, marmots and marmots. .

The mix of temperate and Arctic trees and animals offered a previously unknown ecosystem with no modern equivalent – can act as a genetic road map Researchers have found how different species can adapt to warmer climates.

The discovery is the work of Danish scientists who were able to detect and extract environmental DNA – the genetic material shed into the environment by all living organisms – in a small amount of sediment taken from the Kobenhavn Formation at the mouth of an Arctic fjord. The ocean at the northernmost point of Greenland, during an expedition in 2006. (Greenland is an autonomous country within Denmark.)

They then compared the DNA fragments with existing DNA libraries collected from extinct and living organisms. animals, plants and microorganisms. Based on what is known from the genetic material, fossils and pollen records, it has revealed dozens of other previously undiscovered plants and animals from the area.

“This is the first thing that comes to mind when we look at history does It’s clear that this mastodon and its presence in the far north is far north of what we know as its natural range,” study co-author Mikkel Pedersen, associate professor at the Center for GeoGenetics at the Lundbeck Foundation at the University of Copenhagen, said at a press conference.

This broke the previous record for the world’s oldest DNA study published last year Genetic material extracted from the tooth of a a mammoth that roamed the Siberian steppes more than a million years ago, as well as previous record for DNA from sediment.

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

Professor Eske Willerslev, from St John’s College, University of Cambridge and director of the Lundbeck Foundation, says that while DNA from animal bones or teeth can shed light on an individual species, ecological DNA allows scientists to build a picture of an entire ecosystem. Center for GeoGenetics. In this case, the researchers were reconstructing the ecological community when the temperature will be between 10 and 17 degrees Celsius warmer than present-day Greenland.

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

The researchers were surprised that cedar trees similar to those found in British Columbia today would once have grown in the Arctic alongside species such as larch, which now grow in the northernmost reaches of the planet. They didn’t find any DNA from carnivores, but they believe that predators — bears, wolves and even sabre-toothed tigers — were present in the ecosystem.

Love Dalen, a professor at Stockholm University’s Center for Paleogenetics, who is working on mammoth tooth DNA research but said he was not involved in the research, the groundbreaking finding really “pushed the envelope” for the ancient DNA field.

“This is a really amazing paper!” I said via 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 have affected biodiversity at the species level. That’s something animal DNA can’t do.”

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

A close-up of organic material in a beach bed in the Kap København Formation, northern Greenland.

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

Extracting fragments of the genetic code from the sediment required a great deal of scientific detective work and several painstaking attempts – after the team first determined that DNA was hidden in the clay and quartz in the sediment and could be separated from it. According to the researchers, the binding of the DNA to mineral surfaces is what caused it to survive for so long.

“We’ve revisited these examples and failed and failed. They got the name “Curse of the Köbenhavn Formation” in the laboratory, “said Willerslev.

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

“This is a climate that we will face on Earth due to global warming, and it gives us an idea of ​​how nature will respond to rising temperatures,” he said.

“If we 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.”

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