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Oldest DNA reveals life 2 million years ago in Greenland

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NEW YORK — Scientists have discovered the oldest known DNA and used it to reveal what life was like 2 million years ago on the northern tip of Greenland. Today, it’s a barren Arctic desert, but back then it was a lush landscape of trees and vegetation, home to an array of animals, including even the now-extinct mastodon.

“The study opens the door to a past that has basically been lost,” said lead author Kurt Kjær, a geologist and glacier expert at the University of Copenhagen.

With the hard-to-find animal fossils, the researchers extracted environmental DNA, also known as eDNA, from soil samples. This is genetic material that organisms shed into their environment through hair, waste, saliva or rotting carcasses.

Studying truly ancient DNA can be difficult because the genetic material degrades over time, leaving only small fragments for scientists.

But senior author Eske Willerslev, a geneticist at the University of Cambridge, explained that with the latest technology, researchers can extract genetic information from small, damaged pieces of DNA. In their study, published Wednesday in the journal Nature, they looked for matches by comparing DNA with that of different species.

The samples came from a deposit of sediment in Peary Land called the Kap København formation. Kjær said the area is today an arctic desert.

But Willerslev said that millions of years ago, this region went through a period of intense climate change that increased temperatures. Sediment likely accumulated in the area for tens of thousands of years before the climate cooled and the finds turned into permafrost.

The cold environment would have helped preserve sensitive pieces of DNA — until scientists came along and extracted samples starting in 2006.

During the region’s warm period, when average temperatures were 20 to 34 degrees Fahrenheit (11 to 19 degrees Celsius) higher than today, the region was populated with an unusual array of plant and animal life, the researchers reported. The DNA fragments suggest a mix of Arctic plants, such as birch trees and willow shrubs, with plants that generally prefer warmer climates, such as fir and cedar.

DNA also showed traces of animals such as geese, rabbits, reindeer and lemmings. Previously, the remains of a scarab and some rabbits were the only signs of animal life in the area, Willerslev said.

Kjær said the big surprise was to find DNA from the mastodon, an extinct species that looks like a mix of elephant and mammoth.

Many mastodon fossils have previously been found from temperate forests in North America. It’s an ocean away from Greenland and much further south, Willerslev said.

“A million years later, I didn’t expect to find mastodons in northern Greenland,” said Love Dalen, an evolutionary genomics researcher at Stockholm University who was not involved in the research.

Because of the sediment deposited at the mouth of a fjord, the researchers were also able to obtain clues about marine life from this period. Kjær said DNA suggests horseshoe crabs and green algae lived in the area, meaning the waters nearby were likely much warmer back then.

By pulling dozens of species from just a few sediment samples, the study highlights some of the advantages of eDNA, said Benjamin Vernot, a former DNA researcher at the Max Planck Institute for Evolutionary Anthropology in Germany, who was not involved in the study.

“You get a broader picture of the ecosystem at a given time,” Vernot said. “You don’t have to find this piece of wood to study this plant and this bone to study this mammoth.”

Laura Epp, an eDNA expert at the University of Konstanz in Germany, said it’s difficult to say definitively, based on the available data, whether these species actually lived side-by-side or if the DNA mingled with each other from different parts of the landscape. included in the study.

But Epp said this type of DNA research is valuable for demonstrating “hidden diversity” in ancient landscapes.

Willerslev believes that because these plants and animals survived a period of dramatic climate change, their DNA may offer a “genetic roadmap” to help us adapt to current warming.

Dalen of Stockholm University expects ancient DNA research to continue to push back into the past. He previously worked on the study that held the “oldest DNA” record from a mammoth tusk, which is about a million years old.

“Assuming you can find the right examples, I wouldn’t be surprised if you can go back at least another million years or maybe even a few more million years,” Dalen said. Said.

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The Associated Press Department of Health and Science has support from the Howard Hughes Medical Institute’s Science and Education Media Group. The AP is solely responsible for all content.

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