Discovery of 2-million-year-old DNA in Greenland reveals new details about ancient life

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PBS NewsHour

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JUDY WOODRUFF: Scientists working in Greenland have identified the oldest samples of DNA ever found on Earth. By analyzing this two-million-year-old genetic material, they have revealed how Northern Greenland was once a wildly different environment than the cold polar region it is today, one teeming with ancient wildlife and plants, including some that scientists thought had never lived so far north. William Brangham is back now to explore this with one of the researchers who made this discovery.

WILLIAM BRANGHAM: For more on this remarkable discovery, I’m joined by one of the lead scientists on this project. Professor Eske Willerslev is an evolutionary geneticist and one of the early pioneers in studying ancient DNA. He’s director of the Center for GeoGenetics at the University of Copenhagen’s GLOBE Institute. Professor Willerslev, so good to have you, and congratulations on this research. So you discovered this DNA in Northern Greenland. Can you just tell us a little bit about how you actually found the DNA?

ESKE WILLERSLEV, University of Copenhagen: So it’s some settings, big hills of two-million-year-old dirt basically lying in Northern Greenland. And what we did is we were digging into this dirt and we were drilling out some dirt core. You can’t see any biological material like bones or anything like that. It’s basically dirt, but the DNA from the past has stuck to this dirt. And this is because we’re shedding DNA all the time while we’re alive. And so did these animals and plants also two million years ago.

WILLIAM BRANGHAM: So you’re not drilling into an ancient carcass or an ancient tree. This is something that the animals or plants excreted during their lives?

ESKE WILLERSLEV: That’s correct. So it’s coming from skin cells. It’s coming from ancient feces, from urine, and stuff like that. If I touch the screen like this, right, my DNA will be on the screen. So we will basically — every person is shedding DNA to the surroundings, and some of this DNA will bind to these sediment particles and survive for two million years, basically.

WILLIAM BRANGHAM: What you just said there is so striking, though, because I had no idea that DNA could survive for such a long period of time. How is that possible?

ESKE WILLERSLEV: Well, I was surprised about that too. So the oldest DNA until this study was one million years. And that’s basically what most people believed was possible. But apparently, I mean, when it binds to these mineral particles in the soil, it basically protects the DNA so it can survive much longer.

WILLIAM BRANGHAM: So once you have isolated the DNA and said, aha, this is ancient DNA, how do you go about then trying to figure out what it’s DNA from… what these organisms were?

ESKE WILLERSLEV: Yes, that was a challenge too because two million years is a long time in evolution, right? So whatever DNA we were finding is not identical to what we see today. But we can basically compare it to all known DNA sequences ever recorded from both the present and also what people have retrieved from bones and teeth of the past, for example. And then we can basically identify these fragments, and from these fragments, through the comparison, reconstruct what animals and plants they belonged to.

WILLIAM BRANGHAM: And tell us a little bit about what you discovered.

ESKE WILLERSLEV: It’s a total surprise. I mean, you have to understand that today this area up in Northern Greenland is what we called an arctic desert. There’s almost nothing. It looks like the Sahara, basically. And then what we can see two million years ago, it was a diverse forest of all kinds of trees and also animals like mastodon, these extinct big elephants, as well as the ancestor of reindeers. There were hares, there were lemmings, there were geese. I mean, so a very different ecosystem than what you see today.

WILLIAM BRANGHAM: And I understand as well you found some traces of horseshoe crabs as well. I mean, again, I’m no paleontologist, but it seems striking to think that you’re finding mastodons in some proximity to horseshoe crabs.

ESKE WILLERSLEV: Yes, but this is because if you had been there two million years ago and you were standing at the shore with your rubber boots at the water, right, you would see basically a river — facing a river that is coming out, bringing material with it into the bay, into the ocean. So therefore, it’s a mixture between the DNA from the terrestrial surroundings, right? You would have looked up again at this forest and seen the mastodon and so forth. And then you also get marine organisms, right, because the sediments fold into a marine setting. And that’s why we see the horseshoe crab. And all of these animals suggest a time where it was way warmer than today, probably 11 to 12 degrees Celsius warmer than today.

WILLIAM BRANGHAM: Well, walk me through the implications of that. If these species existed in that warmer world, what are the implications for modern-day man?

ESKE WILLERSLEV: Well, to me, there’s two major implications. One is that what we see is an ecosystem with no modern analogue. There’s nowhere in the world you find this ecosystem, which is a mixture between arctic organisms and temperate organisms. So what it tells us is really that climate change, when it’s getting warmer, is actually quite unpredictable. I mean, most models, if not all models, that are trying to predict how our surroundings, our biology will react to this moment, probably wouldn’t be able to have predicted this when you go back in time. So you can say the plasticity of organisms is different than what we think. And this is, of course, worrisome because if you’re bad at forecasting, it means you also have — it’s difficult to make a strategy to mitigate the consequences of global warming. On the other hand, I would say now we have a genetic road map, right? We have a genetic — it’s the building blocks of life. We have a genetic road map where we can find out how did these organisms back in time adapt to global warming.

WILLIAM BRANGHAM: I know that you have been studying ancient DNA for much of your career, but this does seem like a genuinely striking advancement in your own work. And I wonder how that personally resonates with you. When you realized what you had and what you discovered, what is that like for you?

ESKE WILLERSLEV: I mean, it’s amazing, right? I mean, sometimes I kind of divide our discoveries into what we call founding papers and then you can see the papers where we just build on what we found, basically. And this is definitely one of the founding papers. I mean, it allows us to go back to — for the first time back to before the last Ice Age, right, and to a climate which is very similar to what we are heading towards because of global warming. So it’s also a very important period because it tells us something about what we can expect to happen in the future.

WILLIAM BRANGHAM: Such a tremendous discovery here. Professor Eske Willerslev of the University of Copenhagen, thank you so much for talking with us.

ESKE WILLERSLEV: My pleasure.

JUDY WOODRUFF: So fascinating. I am in awe of these scientists.

H/T jz