Dec 8, 2022 - Science

Ancient DNA describes a lush Greenland 2 million years ago

Illustration of vines growing in DNA shape

Illustration: Aïda Amer/Axios

Ancient DNA recovered from Greenland's permafrost contains fragments of genetic material from plants, corals, mastodons and other animals that provide details about the warm, lush landscape that once existed there, scientists reported this week.

Why it matters: DNA from plants and animals that lived long ago carries records of how organisms responded to climate change in the past and could help scientists understand how they might adapt to current global warming.

  • "It opens up a new possibility to mitigate the impact of climate change," the study's co-author Eske Willerslev of the University of Copenhagen said in a press briefing.

The big picture: Ancient DNA has been found in marine sediments near Antarctica, a cave in Georgia, an Arctic lakebed and other locations around the world.

  • But the 2-million-year-old DNA from the polar desert of Greenland is the oldest sequenced so far — and about twice as old as DNA extracted from a mammoth tooth.

Details: The team of researchers extracted DNA from sediment samples taken from the Kap København Formation in northern Greenland, where fossils discovered earlier indicated a forest existed two million years ago.

  • By comparing the sequences of ancient DNA fragments to those in libraries of DNA from plants, mammals, invertebrates and other organisms, the scientists found 102 genera of plants and animals. (The data resolution isn't fine enough to detect species.)
  • These included poplars and pines that no longer grow in Greenland but are found farther south in northern boreal and deciduous forests, according to the paper published this week in the journal Nature.
  • They also found fragments of DNA from mastodons, hares and geese as well as horseshoe crabs, corals and other marine organisms that suggested the water in the area was warm.
  • Mastodon DNA was a surprise, the researchers said. They are thought to be a much younger species that lived farther south.

What they're saying: "It was super exciting when we recovered the DNA that a very, very different ecosystem appeared," said Willerslev, who has been collecting sediment samples at the site for 16 years in search of two-million-year-old DNA.

How it works: A big challenge for scientists working with ancient DNA is it can degrade over time from shearing, enzymes in microbes or spontaneous chemical reactions.

  • The researchers found clay minerals could preserve the DNA better than quartz, which dominates the sediment. They said improving their methods for extracting DNA from clay could allow them to go further back in time and to increase the resolution of their findings.

Ancient DNA can also be contaminated with genetic material from organisms that lived much later.

  • "We can find DNA in any samples we look at, but most of it will be recent contamination or from living organisms such as microbes," Jamie Wood, a paleoecologist at the University of Adelaide, who wasn't involved in the study, said in an email.
  • The authenticity of the data in the new study was determined by analyzing patterns of damage, comparing the DNA results with pollen from the same samples and other techniques.

The intrigue: The mixture of Arctic and temperate species isn't found on the planet today, Willerslev said.

  • The climate though was "very similar to what we expect to face on Earth due to global warming," he added.
  • Studying DNA from the environment could provide insights about how to help organisms adapt to climate change, including determining which organisms could live together, as well as breeding and gene editing that could help plants, in particular, survive, he said.
  • "Organisms have already experienced what we are facing today with climate change. A lot of those adaptations have been lost. By going back into the past, you have this roadmap of how they adapted."

What to watch: The clay and cold environment that preserved the samples in the study could give researchers insights about the ideal conditions for finding ancient DNA, Wood said.

  • Willerslev and his colleagues are looking at deep sea sediment samples as well. "We know even less about the ocean's response to climate change," he said.
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