Brain Networks and Social Laughter

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This limited time sale awaits you now at alienware. com slash deals 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 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 Iice Age Joining me now is the lead author on that study, Dror Tyler Merchy, who studies ancient DNA at the Hawkeye Institute in British Columbia. 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 paleofces 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 Wooy mammoth or these super cool bones. The idea of looking at poop you know, it's not as flashy of 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, Okaykay, so tell me a little bit about these specimens Where did you find them? When were they from? Yeah So a lot of this field work is done by folks like Scott Coer and Dwayne Frase 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 ends up in the river of 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 you know mammoth and Steepeisen and all the ice age critters you can imagine end up exposed. but you also see in these large vertical exposures a bunch of pockets of A Groundsquirre burows. and These burrows and remains in general age between you know thousands of years ago to our oldest samples here are seven hundred thousand years old, which is reallyally ancient. It's you know, anatomically modern humans maybe arose about like three hundred thousand years ago. so twwice 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, oy, 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 of those? I wonder what all's in there Wow. Okaykay, 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 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 and you open the tube to pull out the superdate and then you realize, oh, wow, yeah, this is definitely liquefied poop right now up, that's kind of amazing For seven hundred thousand years Yeah. but 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 sample is which And that took quite a lot of effort because There's so many partially degraded organics in poop that make chemically it quite challenging But then after you do all that, you have to then try to pull out the DNA you're interested in, which is a whole other biochemical effort because you know, ninety percent of the sample is just DNA that we don't know what it is. And so that just kind of gets put into some other bin. and then of the ten percent or so that we can identify ninety nine point nine percent of that is bacteria. And then of theo point one percent that's other stuff is all the other things that are in there And we're really interested in here in case of the plants and animals. Are you cross referencing with a library or something? I mean, how do how do you do that? Is there a simple way to talk about it Yeah, so the um NCBI nucleotide database, people their genomis basically just upload all of their DNA data for every organism they've ever discovered and it just goes on this database We then pull a local copy of this database, which is huge. AM Hundreds of millions or it must be billions of reference genomes on there now at this point, mayaybe not full genomes, but sequences anyway. And then we one by one, every you know thirty little base pair sequence of DNA, H of DNA that we get, we align it to this gigantic database and you have to use high performance computers to run through you know, these enormous calculations to figure out what everything is In this case, it took something like running continuously on four high performance servers at four different universities three to five months or so of continuous and I was hogging the machines for most of that time. So it's a lot of data Wow All right, well talkk me through some of the highlights of what you found. Yeah, well, when we first started, I thought, oh, this it's going to be mostly ground squirrel DNA and their gut microbiomome, so the kind of bacteria and stuff that live in their guts. But I really wasn't expecting to find Wlly Mammoth and step bison and horse and wolves and Basically a snapshot of the Ice age in groundquirrel poop and even more DNA than we typically find even in the sediments in these areas. So it's really this kind of enriched picture of all these different animals and plants and fungi and microbes And not only are we getting individual little fragments of these organisms that we're able to identify as, oh, yep, this definitely belongs to you know, this species of grass or this belongs to like the um this type of herb We can actually start reassembling the genomes of these different organisms all at the same time. and stitch those back together to then look at how they're related to other things today and So there's all sorts of applications you can get into And the kind of the go ahead, no, go ahead. Oh, I was just gonna to say that the big question is, well Why is this all this DNA in there? Like That was what I was gonna ask What did these squirrels get up to? Yeah. so one of the important parts is that Arctic ground squirrels. they are in hiberrnation or a state of torpor for about eight months of the year. So they really are unconscious most of the time and in their buroughs. And so The period of the year that they're actually awake. They need to be out in that landscape getting everything they can for nutrition and Even when we first started, I kind of just assumed ground squirrels were, you know mostly eating nuts and seeds and stuff like that I didn't realize that they Re reallyally kind of like little bears almost. So we think There were so many big animals around during the Pleistocene, there was this kind of paradox of productivity, tons of big organisms all over the place and there is dead carcasses of mammoths around and such. and we think that they're eating those remains and bringing back bones and bits of tissues to their nest to help make it through. You know, cold winter months during the ice age during extxtremely cold periods of time H I mean, is there anything about in particular that makes it a really good time capsule Yeah, that's another great question I think in part It's sort of a natural enrichment of the environal DNA that's on that landscape anyway you know, like we're shedding DNA all the time. And if that DNA ends up in the sediment, it can end up binding to minerals in the sediment and preserving long term I would think The DNA that passed through the digestive system of a squirrel You wouldn't think that would have great preservation. So it's kind of wild to imagine that these copper lights would be that well preserved And so I don't know if it's just there's so much to begin with that it could make up for the fact that there is natural degradation from those microbes Or maybe there's some other sort of microbiome effect where the bacteria in the poop are protecting it from the kind of other environmental bacteria that might break down that DNA That's definitely an area that we want to get more into. I'm sure there's some chemistry involved for why the DNA is preserving so well Any of your findings challenge any assumptions of sort of ice age ecosystems Yeah, well, one of them that's kind of a tentative call in our in our assignments is We head headits to Puma, which is Cgar But there weren't cougars as far as we know in Northern Yukon at that time. They really came from South America But when we look at the hits to Puma They also match to American cheetah But there wasn't an American cheetah genome available on the reference database at the time. so it hit the next closest ancestor, which was Cgar I suspect these are actually cheetah reeds, American cheetah, which is actually It's kind of a little bit of a misnomer They're not that closely related to cheetah in Africa I think they initially thought they were And so this is sort of a little bit of a challenge of, well Were either cougars present here much deeper in the past or was it this other organism? There's some more investigations needed there But then when we get into the squirrels, that's a whole other can of worms in that There is maybe several additional species that have just kind of been assumed to all be the same thing in part because people aren't as interested in squirrels, so there hasn't been as much effort into their like own taxonomic, you know, evolutionary history We've definitely the one at seven hundred thousand years old. seems like a totally different thing then the ones that are even there today are probably actually several species that have been together into one thing When you walk down the street and you see like Sat on the ground or you like, There's so much in it I feel like definitely now I realize oh ye Well, and especially from an environmental DNA perspective, just realizing You know, we're shedding millions of skin cells every day. There's just so much DNA being released. and yeah, poop is full of DNA, but also we're just kind of like you know, the character Pig Ben from Charlie Brown J just releasing information, all these like, you know, incredibly small molecules of DNA all the time So's just there's kind of gold mines all over the place in all these unsuspecting locations Dr. Tyler Merchy is a biomolecular archeologist at the Hakeye Institute in British Columbia. Tyler, thank you so much Thanks thanks for chatting. This was great We have to take a quick break, but if you lik these poop buns, stick around. 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Go to join deeleteMe d. com slash Friday and use promo code Friday at checkout That's joindeleteme d. com slash Friday code Friday WNYC Studios is supported by Con Edison New York, it's hot out there. and you're probably relying on air conditioning to keep cool But if your AC is always turned up Well, your energy bills are likely to go up too Luckily, Con Edison has ways to help Try their energy saving tips, which are personalized to you, or explore budget billing, which helps you spread your biggest payments out across the year Visit coned. com slash Bill helpelp to get started because taking control is New York Hey there, it's Ira. I want you to think about the last time you had a big old laugh. You know, the kind where you're running out of breath, clutching your stomach, your eyes are tearing up and you just can't seem to stop You know, there's a fancy phrase for this. It's called spontaneous or involuntary laughter Now this feels like a very different kind of laugh then. let's say how you might laugh making small talk with your neighbors or ling at Flors and my jokes This is called voluntary laughter And not only do these two types of laughs feel very different. But a new study found that they originate in different parts of the brain Joining me is study author, Dctor Sophie Scott at University College, London. doctor Scott studies how our brains process and produce speech. Welcome to Science Friday. Thank you so much Nice to have you. Okay, Sophia, what did you find? Where do these different laughs come from So there's basically in the human brain two different ways that control how sounds are made One is called the volitional motor system and it's associated with brain areas you actually only find in humans and they are recruited when you are talking, when you are singing, when you're using your voice in a volitional way. and by volitional I don't mean you're kind of paying attention to exactly how you make every single speech sound, but you it's a voluntary act. could Stop at any time