Scientists are using the world’s oldest known DNA to paint a picture of what life was like 2 million years ago in the far north of Greenland.
Today, it is an arctic arctic wasteland, but back then it was a lush landscape of trees and vegetation with a wide variety of animals, even the now-extinct mastodon.
“The study opens the door to a past that has basically been lost,” said lead author Kurt Kjar, a geologist and glacier expert at the University of Copenhagen.
With animal fossils hard to come by, the researchers extracted environmental DNA, also known as eDNA, from soil samples. This is the genetic material that organisms shed into their environment, for example through hair, waste, spit or decaying carcasses.
Studying very old DNA can be challenging because genetic material breaks down over time, leaving scientists with only tiny fragments.
But with the latest technology, researchers were able to extract genetic information from small pieces of damaged DNA, explained senior author Eske Willerslev, a geneticist at the University of Cambridge. In their study, published Wednesday in the journal Nature, they compared DNA with that of different species, looking for matches.
The samples came from a sediment deposit called the Kap Kobenhavn Formation in Peary Land. Today, the area is a polar desert, Kjær said.
But millions of years ago, this region was going through a period of intense climate change that sent temperatures soaring, Willerslev said. The sediments likely accumulated over tens of thousands of years at the site before the climate cooled and cemented the finds into permafrost.
The cold environment would help preserve the delicate bits of DNA, until scientists came and extracted 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 area was teeming with an unusual variety of plant and animal life, the researchers reported . The DNA fragments suggest a mix of arctic plants, such as birches and willow bushes, with others that typically prefer warmer climates, such as firs and cedars.
The DNA also showed traces of animals such as geese, hares, reindeer and lemmings. Previously, a dung beetle and some hare remains had been 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, Kjar said.
Many mastodon fossils have previously been found in the temperate forests of North America. That’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.
Because the sediment accumulated at the mouth of a fjord, the researchers were also able to obtain clues about the marine life of that time period. The DNA suggests that horseshoe crabs and green algae lived in the area, meaning the nearby waters were likely much warmer back then, Kjar said.
By extracting dozens of species from 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 did not participate in the study.
“You really get a broader picture of the ecosystem at a particular time,” Vernot said. “You don’t have to go find 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 whether these species actually lived side by side or if the DNA was mixed from different parts of the landscape, said Laura Epp, an eDNA expert at the University of Constance of Germany which was not. involved in the study.
But Epp said this type of DNA research is valuable in showing “hidden diversity” in ancient landscapes.
Willerslev believes that because these plants and animals survived a time of dramatic climate change, their DNA could provide a “genetic road map” to help us adapt to today’s warming.
Stockholm University’s Dalen hopes ancient DNA research will continue to delve deeper into the past. He worked on the study that previously held the “oldest DNA” record, from a million-year-old mammoth tooth.
“I wouldn’t be surprised if you could go back at least one or maybe a few million years, assuming you can find the right samples,” Dalen said.
The Sabah Daily Gazette
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