NEW YORK (AP) — Scientists have discovered the oldest known DNA and used it to reveal what life was like 2 million years ago in the northern tip of Greenland. Today it’s a barren arctic wasteland, but back then it was a lush landscape of trees and vegetation with an array of animals, even the now extinct behemoth.
“The study opens the door to a past that has all but been lost,” said lead author Kurt Kjær, a geologist and glacier expert at the University of Copenhagen.
Since animal fossils are hard to find, the researchers extracted environmental DNA, also known as eDNA, from soil samples. It is the genetic material that organisms release into their environment – for example, through hair, waste, spit or decaying carcasses.
Studying very old DNA can be a challenge because the genetic material breaks down over time, leaving scientists with only tiny fragments.
But with the latest technology, researchers have been able to extract genetic information from small bits of damaged DNA, explained lead author Eske Willerslev, a geneticist at the University of Cambridge. In their study, published Wednesday in the journal Naturethey compared the DNA to that of different species, looking for matches.
The samples came from a sediment deposit called the Kap København Formation in Peary Land. Today, the region is a polar desert, Kjær said.
But millions of years ago, this region was undergoing a period of intense climate change that caused temperatures to rise, Willerslev said. Sediment likely accumulated over tens of thousands of years at the site before the climate cooled and cemented the finds in the permafrost.
The cold environment would help preserve the delicate pieces of DNA – until scientists arrive and drill the 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 filled with an unusual array of plants and animals, the researchers reported. The DNA fragments suggest a mix of arctic plants, like birches and willows, with those that generally prefer warmer climates, like firs and cedars.
DNA also showed animal tracks, including geese, hares, reindeer and lemmings. Previously, a dung beetle and hare remains were the only signs of animal life at the site, Willerslev said.
A big surprise was finding DNA from the mastodon, an extinct species that looks like a cross between an elephant and a mammoth, Kjær said.
Many mastodon fossils have already been found in the temperate forests of North America. It’s an ocean away from Greenland, and much further south, Willerslev said.
“I would not have expected, in a million years, to find mastodons in northern Greenland,” said Love Dalen, an evolutionary genomics researcher at Stockholm University who was not involved in the study. study.
Because the sediments accumulated at the mouth of a fjord, the researchers were also able to obtain clues about marine life from this period. DNA suggests horseshoe crabs and green algae lived in the area, meaning nearby waters were likely much warmer at the time, Kjær said.
By extracting dozens of species from a few sediment samples, the study highlights some of the benefits of eDNA, said Benjamin Vernot, a former DNA researcher at the Max Planck Institute for Evolutionary Anthropology in Germany who did not participate in the study.
“You really get a bigger picture of the ecosystem at any given time,” Vernot said. “You don’t need to fetch this piece of wood to study this plant, and this bone to study this mammoth.”
Based on the available data, it’s hard to say for sure if these species really lived side by side, or if the DNA was mixed from different parts of the landscape, said Laura Epp, an eDNA expert at the German University of Konstanz which was not involved in the study.
But Epp said this type of DNA research is valuable for showing “hidden diversity” in ancient landscapes.
Willerslev thinks that because these plants and animals survived a period of dramatic climate change, their DNA could offer a “genetic roadmap” to help us adapt to today’s warming.
Dalen of Stockholm University expects research into ancient DNA to continue to push further into the past. He worked on the study that previously held the record for “the oldest DNA”, of a mammoth tooth around a million years old.
“I wouldn’t be surprised if you could go back at least one or maybe a few million years, assuming you could find the right samples,” Dalen said.
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The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute Science and Education Media Group. The AP is solely responsible for all content.
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