Squirrel poop drops Ice Age clues + The neuroscience of laughter
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Hey, it's Flora, and you're listening to Science Friday. Hundreds of thousands of years ago, deep in the mountains of the Yukon, a ground squirrel pooped. And that scat stayed frozen for millennia until very recently when researchers thought it out and found a real data dump. Scientists analyzed the DNA in the droppings and identified traces of a surprising number of animals and plants, providing this new detailed snapshot of life during the last ice age. Joining me now is the lead author on that study, Dr. Tyler Murchie, who studies ancient DNA at the Hawkeye Institute in British Columbia.
What surprising findings were revealed from ancient squirrel poop?
Tyler, welcome to Science Friday.
Thanks. It's awesome to be here.
Thank you for being here. Is poop underappreciated in archaeology? Like, is poop the new amber?
I would definitely say so. At the beginning of the field, there was a lot of people who had worked with paleofeces to try to get DNA. But it's always kind of been this undercurrent of the field because people really gravitate towards, you know, the big, amazing tusk of the woolly mammoth or these super cool bones. The idea of looking at poop, You know, it's not as flashy of a sample type. And so a lot of these have just kind of been in cold storage for some time. And I think this paper and some of our other ongoing work is really highlighting you can get amazing ancient biomolecules from unsuspecting sources like, you know, old poop.
Yeah. OK, so tell me a little bit about these specimens. Where did you find them? When were they from?
Yeah. So a lot of this fieldwork is done by folks like Scott Cocker and Dwayne Fraze. And they go out to these areas in the Yukon that are these placer gold mines. And so the miners are there trying to thaw gold out of the permafrost sediments. And so they spray water cannons on the walls. This thaws out the gold. It ends up in the river bottoms. But then the thing that they maybe don't expect to find are tons and tons of fossils. And so tens of thousands of remains of mammoths and step-eisen and all the Ice Age critters you can imagine end up exposed. But you also see in these large vertical exposures a whole bunch of pockets of ground squirrel burrows. And these burrows and remains in general age between, you know, thousands of years ago to our oldest samples here are 700,000 years old, which is, you know, really ancient.
It's, you know, anatomically modern humans maybe arose about like 300,000 years ago. So twice as old and more than that.
So they're sampling within these burrows?
Yeah, and well, part of the effort is to get up to these burrows and see like, okay, what's all in there? And a lot of them contain, you know, bits of plants. There's unidentified bone, there's seeds and nuts and all this kinds of stuff. And then there's this whole midden, this latrine area that's just full of poop. And there's hundreds of poops all kind of packed together in one spot. This is their pooping area. And we thought, well, what if we looked at the DNA that's inside those? I wonder what all's in there.
Wow. Okay, so you bring it back to the lab, and then what's the next step? What exactly are you analyzing?
Yeah, so we're trying to pull the ancient DNA out. And in part, that involves taking a small sample and then digesting the organic and inorganic parts of that to release the DNA. That ends up in solution. The funny part is that, you know, when you're working with samples, usually there's no smell. But with these samples, it was only once you put them in solution and digested that you and you open the tube to pull out the superdate. And then you realize, oh, wow, yeah, this is definitely liquefied poop right now. The smell holds up.
That's kind of amazing for 700,000 years.
Yeah, well, it's in part, they've been frozen in permafrost all that time. So it's really spectacular preservation.
Wow.
Yeah, and then so you're trying to get, you get the DNA out, and then you have to attach adapters to the ends of the fragments. And this is because when using high throughput sequencing technologies, where we get hundreds of millions or billions of DNA sequences for every sample, you have to be able to identify, okay, which samples which, and that took quite a lot of effort, because...
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