'Amazing' DNA 2 million years old reveals ancient ecosystem in Greenland

‘Amazing’ DNA 2 million years old reveals ancient ecosystem in Greenland

Mastodons, geese, reindeer and hares in an illustration from ancient Greenland.

An illustration of Cape Copenhagen 2 million years ago.
Drawing: Beth Zaiken

A team of scientists has sequenced the oldest DNA to date, found in permafrost in the far north of Greenland. The DNA is 2 million years old, surpassing the previous oldest DNA record by a million years.

The genetic material came from 41 sediment samples taken from Kap København, a formation in Peary Land. Today it is a dune-covered polar desert populated by musk oxen and lichens, but in the distant past the area was a temperate forest. According to the team’s analysis, it was home to a host of beasts, including (to everyone’s surprise) behemoths, not previously thought to be so far north.

“It was super exciting when we retrieved the DNA that a very, very different ecosystem emerged,” said Eske Willerslev, an evolutionary geneticist at the University of Cambridge and co-author of the study, during an interview. a press conference held this week.

The previous record for the oldest known DNA was from million year old mammoth teeth on Wrangel Island, where hairy proboscideans persisted until their extinction about 4,000 years ago. The new record holder is not descended from a single animal; it highlights a whole ecosystem of organisms that lived in Greenland shortly after the Pliocene epoch gave way to the Pleistocene. The team’s research is published today in nature.

The samples represent what’s called environmental DNA, which means they come from environmental samples (in this case, frozen sediment), rather than being extracted from the bones or teeth of an ancient creature. . Environmental DNA (eDNA for short) contains the genetic material of many organisms in an environment, which shed hair, blow snot, and poop evidence of their presence in an area.

eDNA (both ancient and contemporary) shows researchers a complete organic picture, which includes everything from birds and insects to fungi. It can reveal the ancient presence of animals without needing to rely on fossil evidence. Outside of paleontology, eDNA is particularly useful for tracking down endangered or otherwise hard-to-detect animals in their environment. like crayfish and quolls.

But DNA is an unstable molecule. It contains the genetic information that dictates the morphology, behavior and relationships of species, but this sensitive information will only remain as long as the environment permits. Generally, you are more likely to find preserved DNA in dry, cold areas than in humid, warm areas.

Millions of years ago, the northern tip of Greenland was as lush and bustling as the name of the country would lead you to believe. But he was getting cold. At one point, the soil from a coastal forest washed into an estuary, where it was deposited. DNA in soil is adsorbed onto clay and quartz minerals, potentially aiding the preservation of organic molecules.

Fast forward through 2 million years of climatic and geological changes, and a team of scientists have managed to extract the details of this ancient forest environment, like a message from a bottle.

“People knew from microfossils that there had been trees up there – some kind of forest up there – but DNA allowed us to identify many more taxa,” Willerslev added. The presence of behemoths, he noted, was “mind-blowing.”

Two researchers digging a dune at Cape Copenhagen.

Study co-authors Eske Willerslev and Kurt H. Kjær expose new layers of sediment.
Photo: Svend Founder

Kap København is a dark landscape, but evidence of its ancient past persists beyond the genetic level. Withered branches are signs of Greenland’s old-growth forests, and thawing permafrost occasionally releases 2-million-year-old moss.

“The ancient DNA samples were found deep within sediments that had accumulated over 20,000 years,” said Kurt H. Kjær, a geologist at the University of Copenhagen, at a Cambridge university. Release. “The sediment was ultimately preserved in ice or permafrost and, crucially, was undisturbed by humans for two million years.”

It took researchers 16 years to collect and ultimately analyze paleoenvironmental eDNA, which came from 41 sediment samples taken from five sites in Kap København in 2006, 2012 and 2016.

The scientists then compared the eDNA sequences of their samples with reference genomes in a database to see which animals and plants lived there.

The researchers found plant and animal DNA that suggests that Kap København was a much warmer boreal forest environment than present-day Greenland. “Obviously it is important that we can go back much further in time [with the new DNA age result], but this is also the time when we can go back,” Willerslev said. “It’s a climate that is very similar to what we expect to face on Earth through its global warming.”

In this way, the researchers believe that paleoenvironmental data from Kap København can provide clues to how modern species will adapt to a rapidly warming world.

Climatic records indicate that the region was between 51.8 degrees and 66.2 degrees Fahrenheit warmer on average than it is today. It was much more temperate, and plants and animals thrived. In fact, the environment has no modern analogue; Arctic species cohabited with more temperate species.

Among the species detected by the team were trees such as poplar, birch, cedar, birch and cedar, as well as animals such as mastodons, reindeer, rodents and geese. The mastodon is a cousin of the woolly mammoth most commonly associated with North America, but it has obviously found its way much further north.

“I think this is a fantastic study that is clearly groundbreaking, and the results are extremely cool! The mastodons from northern Greenland are an amazing find!” said Love Dalén, an evolutionary geneticist at the Swedish Museum of Natural History who is not affiliated with the newspaper, in an email to Gizmodo Dalén was part of the team that found million-year-old DNA in a mammoth molar last year.

“This study most certainly changes the previous conception of the age of DNA that can be recovered from sediments,” Dalén added. (The previous record for oldest sediment DNA was around 250,000 year old hominin DNA from Denisova Cave.)

A view over Kap København to the coast.

Kap København is now inland from the coast, but 2 million years ago it was contiguous with it.
Photo: Kurt H. Cher

Curiously, the team also detected horseshoe crab, coral and algae DNA in the 2 million year old soil. This is because of where the sampled soil ended up, in a coastal estuary that was home to marine species. When the soil was washed away by the sea, the DNA of marine organisms became part of the eclectic cocktail of eDNA. Later, the ground became frozen permafrost and the genetic material was preserved there.

eDNA is not a perfect reflection of the species present in an environment. The researchers found no carnivores in their sequencing, an unlikely situation in the field. The team attributed the absence to low-biomass apex predators likely formed in the environment. They were “probably something that ate mastodons and reindeer”, Willerslev speculated.

Other taxa will be mapped from the team’s samples, including certain bacteria and fungi. Because recently sequenced DNA may have had its longevity increased by clinging to quartz crystals and clay, Willerslev added that ancient DNA could be found at sites as far south as Africa, with the right environmental conditions.

This discovery gives hope that even older genetic samples could be found. How old exactly could this be? At the press conference, Willerslev said he wouldn’t be surprised if “we could go back twice as far” – although “I don’t guarantee it”.

The team has plans to collect DNA samples from the deep-sea environment. By applying the techniques deployed on the Kap København samples, scientists may be able to unlock the secrets of paleoenvironments far from the Arctic Circle. and the complete catalog of creatures they contain.

More:Scientists found out which animals were in a zoo simply by taking DNA from the air

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