New York — Scientists have discovered the oldest known DNA and used it to reveal what life looked like 2 million years ago at the northern tip of Greenland. Today, it’s a barren arctic desert, but back then it was a lush landscape of trees and vegetation with an array of animals, even the now-extinct mastodon.
“The study opens the door to an essentially lost past,” said lead author Kurt Kjaer, a geologist and glaciologist at the University of Copenhagen.
With animal fossils so difficult to come by, researchers extracted environmental DNA, also known as eDNA, from soil samples. This is the genetic material that organisms shed into their surroundings – for example, through hair, excrement, spit, or decomposing corpses.
Studying ancient DNA can be a challenge because the genetic material degrades over time, leaving only small fragments for scientists.
But with the latest technology, researchers have been able to extract genetic information from small, damaged fragments of DNA, explained senior author Eske Willerslev, a geneticist at the University of Cambridge. In their study, published Wednesday in the journal Nature, they compared the DNA of different species, looking for matches.
The samples came from a sediment called the Cap Copenhaven Formation in Peary Land. Today, Kiar said, the area is a polar desert.
Millions of years ago, Willerslev said, this region was going through a period of severe climate change that led to a rise in temperatures. Sediments likely accumulated for tens of thousands of years at the site before the climate cooled and stabilized the finds in the permafrost.
The cold environment would help preserve the tiny bits of DNA — until scientists came along and excavated the samples, starting in 2006.
Researchers report that during the region’s warm period, when average temperatures were 20 to 34 degrees Fahrenheit (11 to 19 degrees Celsius) higher than they are today, the region was filled with an extraordinary array of plant and animal life. The DNA fragments point to a mixture of arctic plants, such as birch trees and willow bushes, with those that typically prefer warmer climates, such as fir and cedars.
The DNA also showed traces of animals including geese, hares, reindeer and lemmings. Previously, dung beetle and some rabbit remains were the only signs of animal life at the site, Willerslev said.
One of the big surprises was finding DNA from a mastodon, an extinct species that looked like a mix between an elephant and a mammoth, Kyarr said.
Several former mastodon fossils have been found from the temperate forests of North America. This is an ocean farther south than Greenland, Wellerslev said.
“I didn’t expect, in a million years, that I would find mastodons in northern Greenland,” said Love Dalen, an evolutionary genomics researcher at Stockholm University who was not involved in the study.
Because sediments accumulated at the mouth of the fjord, the researchers were also able to obtain clues about marine life from this time period. The DNA indicates that horseshoe crabs and green algae lived in the area — which means the nearby waters were likely much warmer at the time, Kyarr said.
By pulling dozens of species from a few sediment samples, the study highlights some of the advantages of amplified tRNA, said Benjamin Vernot, a paleontological DNA researcher at the Max Planck Institute for Evolutionary Anthropology in Germany who was not involved in the study.
“You really get a broader picture of the ecosystem at a given time,” Vernot said. “You don’t have to go and find this piece of wood to study this plant, and this bone to study this mammoth.”
Based on the available data, it’s difficult to ascertain whether these species really lived side by side, or if DNA was mixed from different parts of the landscape, said Laura Epp, an RNA expert at Germany’s University of Konstanz, who was not like that. participate in the study.
But Ip said this kind of DNA research is valuable for showing the “hidden diversity” of ancient landscapes.
Willerslev believes that because these plants and animals survived during a period of dramatic climate change, their DNA could provide a “genetic roadmap” to help us adapt to current warming.
Dalen of Stockholm University expects ancient DNA research to continue to dig deeper into the past. He worked on the study that previously held the “oldest DNA record,” from a mammoth tooth that was about a million years old.
“I wouldn’t be surprised if you could go back at least once or maybe a few million years, assuming you can find the right specimens,” Dalen said.
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