[Insert Your Own Catchy Title About Younger Dryas Here]

Quick, name your favorite geological mystery. You can’t do it! Well, don’t worry. In this episode we’re going to tell you all about what will surely be your favorite (albeit only) one when we get into one weird millennium that happened not that long ago. See omnystudio.com/listener https://omnystudio.com/listener for privacy information.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

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• 0:04Josh Clark?

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• 1:41Speaker 00

  Welcome to Stuff You Should Know, a production of iHeart Radio.

• 1:51Josh Clark?

  Hey, and welcome to the podcast. I'm Josh and there's Chuck and Jerry's here too. And this is Stuff You Should Know. And what we've got on our hands today, Chuck, is a hot potato of a real deal geological mystery.

• 2:05Speaker 02

  Hot potato?

• 2:08Speaker 02

  That's how Emily's family says potato.

• 2:11Josh Clark?

  I think I would only say it when it's preceded by hot. I would only say it like, I wouldn't say, I'm going to have a baked potato. Like you'd be out of your mind to say it like that.

• 2:20Speaker 02

  Nor would you say a hot potato. Like what a square.

• 2:24Josh Clark?

  Yeah, that is pretty square, isn't it?

• 2:26Speaker 02

  Get the stick out of your butt, fella, loosen up.

• 2:28Josh Clark?

  Right, loosen up, get the cardigan out from around your shoulders.

• 2:32Speaker 02

  Yeah, geez.

• 2:34Josh Clark?

  So that was obscure, but still, um, so like I said, this is a mystery today. And just to give a brief brush stroke overview, the widest brush, real lot of space in between bristles, just barely any paint on it, that kind of overview.

• 2:49Speaker 02

  Oh, wow.

• 2:50Josh Clark?

  What we're talking about is something called the Younger Dryas, which is a pretty, it's a pretty terrible name for this, if you want to be catchy, right?

• 3:00Speaker 02

  Yeah, I mean, I think a lot of people would probably say WTF.

• 3:04Josh Clark?

  Right, well, let's just call it the YD, if we're gonna, if we're gonna put initials on things. How about that, or abbreviate things? So, um, the, the YD, the Younger Dryas, is this, this surprising, shocking period in Earth's history, fairly recent history, where we came out of the last ice age, everything was going smoothly, and then bam, we got hit by another ice age out of nowhere. That lasts for over a thousand years, and then bam, it goes away just as fast as it came along. And paleogeologists, paleoclimatologists, all the paleos are perplexed as to what caused it and then why it stopped so suddenly, too. That's why I said it's a real deal geological mystery.

• 3:50Speaker 02

  Yeah, and, and a time, as we'll see, where, uh, the Earth and its inhabitants and, uh, the animals and, um, nature was all going like, alright, thank God, we can, we can finally get down to business and start being an Earth, uh, like a legit Earth. And then, you know, the YDs come along and say, not so fast.

• 4:13Josh Clark?

  Right, and you call it a legit Earth because when it finally ended, and actually that period in between the last ice age and the YD,

• 4:23Josh Clark?

  Those are like really habitable for human beings. Like, we love those kind of conditions, so much so that after the YD ended, it became the age of humans.

• 4:32Speaker 02

  Yeah.

• 4:33Josh Clark?

  Like, this is the, this is the age where we began our civilizations. We started farming. We began to flourish as a species and basically take over the planet. And what's interesting is, this is the most recent Ice Age. There have been seven in Earth's history. And just as an aside, this was the Wisconsonian Ice Age that we're talking about. The last one was 250 million years before, right? So it's pretty significant that we just, geologically speaking, came out of an Ice Age, because there's not that many. And then, not coincidentally, when the second to last Ice Age ended, that opened the door for the dinosaurs to come along and take over the Earth. So things, big things happen when an Ice Age changes. So for it to switch back to an Ice

• 5:16Josh Clark?

  Age all of a sudden, and then switch back to nice and temperate for us humans, it is just very weird. It was actually, I've seen it described as an extreme weather millennial event.

• 5:29Speaker 02

  Yeah, and you know, it kind of made me wonder, had this not happened, because we were sort of headed toward, you know, legit Earth, like I said, before, you know, I mean, it would, obviously wouldn't change the year, but let's say, as far along this goes, we would be like the year 3000 something.

• 5:47Josh Clark?

  Right.

• 5:48Speaker 02

  Like, would we be just that much further along as a planet? Or would we be nowhere, because in a thousand years, we will have already destroyed ourselves?

• 5:57Josh Clark?

  The second one.

• 5:59Speaker 02

  Okay. All right. So it's a good thing this happened, or we wouldn't be talking about it right now.

• 6:03Josh Clark?

  Exactly. That's exactly right. So yeah, that's a really anthropic way of looking at it.

• 6:09Speaker 02

  Well.

• 6:09Josh Clark?

  Um, speaking of, I bought a copy of If Anyone Builds It, Everyone Dies, the Eliezer Yudkowsky Nate Sora's book that just came out.

• 6:18Speaker 02

  Okay. I did not know about it. You say that as if it was just on the tip of my tongue, which I appreciate.

• 6:23Josh Clark?

  No, you do. Um, we remember, I basically mischaracterized it in the Zizians episode and had to make like a whole, okay. That book, right, about building AI. And if anyone builds it, then we're all gonna die. Like, just the existential threat of AI. It is really good. You could read it in, if you had a, a day that you could dedicate to reading it, you could read it in a day. It's really popularly written, lots of really cool anecdotes. It's just very good. So I strongly recommend that book.

• 6:51Speaker 02

  Great.

• 6:52Josh Clark?

  Okay, so let's kind of just back it up a little bit and go to the previous Ice Age, the Wisconsinian Ice Age, and talk about what Earth looked like like that.

• 7:02Speaker 02

  Yeah, so it was, uh, it was very icy. Uh, there were huge ice sheets covering a lot of Earth, like most of North America, uh, Northern Europe and Asia. And as, as we'll see, a lot of the, um, the YD is affected the Northern Hemisphere much more than the Southern, but also weird things happen in the Southern Hemisphere that don't quite jive. That's why it's such a kind of a strange mystery.

• 7:25Josh Clark?

  Mm-hmm.

• 7:26Speaker 02

  But, uh, lots of ice everywhere. We had barren plains, very harsh conditions. Uh, we had things like, you know, woolly mammoths, like ice, ice-loving creatures dwelling the Earth and, uh, you know, human populations that were sparse and scattered and, and constantly kind of moving around, trying to survive.

• 7:45Josh Clark?

  Right. And so that, the last Ice Age, um, started about 100,000 years ago, and it took about 80,000 years to reach its peak point. Um, so 20,000 years ago, it hit what's called the last glacial maximum, right? Um, so it took 80,000 years to get there and then 10,000 years to basically melt. Uh, it melted a lot faster than it developed. Um, and just like right after it peaked, it just started warming up and it took about 9,000 years and all of the ice sheets, all the glaciers, all the stuff that was covering Earth and keeping it in Ice Age, just basically went away and Earth just blossomed into a version that we like.

• 8:24Speaker 02

  Yeah. And it became, you know, not terribly unlike what we're looking at now. Uh, there was a jump in temperatures that was, you know, kind of close-ish to today. And this was called the, and I never know how to pronounce.

• 8:36Josh Clark?

  It's an umlaut.

• 8:38Speaker 02

  Is it really?

• 8:38Josh Clark?

  Yeah, I'm, I'm.

• 8:39Speaker 02

  That's all it is.

• 8:40Josh Clark?

  Yeah. So all of our Nordic friends, the circle with the, the forward slash through or the O with the forward slash through.

• 8:47Speaker 02

  Yeah.

• 8:47Josh Clark?

  That's an umlaut, right?

• 8:49Speaker 02

  Okay. I mean, I guess we call it the null set because it looks like a zero with a slash through it.

• 8:54Josh Clark?

  So call it that.

• 8:54Speaker 02

  I mean, we don't really call it that, but that's what it looks like.

• 8:56Josh Clark?

  Pronounce it like that.

• 8:58Speaker 02

  All right. What, what with the, uh, umlaut?

• 9:00Josh Clark?

  No, the null set.

• 9:02Speaker 02

  No. Would know how to do that. With the umlaut, I guess my best stab would be the Burling Alarud interstadio.

• 9:11Josh Clark?

  I think you nailed it.

• 9:13Speaker 02

  All right. A lot more rain. We got us, you know, we achieved a sea level that's not what we have today, but about half of what we have today. With that rain, obviously, you're going to get a lot of plants. The woodlands are thriving. Animals are now are, you know, forest dwelling and walking alongside things like cave bears and woolly mammoths. And things are going pretty good. We have Homo sapiens at this point are are the only humans that are around at this point. And they're like, they're loving life, man. They're saying, all right, we can travel a little bit more. And as we'll see, you know, kind of dabble, stick their toe in settling here and there.

• 9:53Josh Clark?

  Yeah, this was actually right before this was the point when people from Eurasia migrated into North America. So this is the point where they were cut off. They couldn't go back. There's no going back. They were in North and South America now because the Bering Land Bridge was covered up by those rising sea levels, which turned it into the Bering Sea. And this time, so remember, we're talking about this little period after the end of the Ice Age before the YD comes along, where everything seems to be going smoothly for humans. This is where we started taking our first stabs at agriculture.

• 10:26Speaker 02

  Yeah.

• 10:26Josh Clark?

  We're just like, let's try something new. We just came out of an Ice Age. Let's just get as funky as we can with it. And we're going to basically take some of that energy in that time that we dedicate to hunting and gathering and put it into farming. I just made that word up, but let's call it that from now on.

• 10:46Speaker 02

  Like, what is farming? And they're like, you're doing it right now, buddy. I see you over there picking weeds.

• 10:51Josh Clark?

  Exactly.

• 10:52Speaker 02

  And tending to those those wild plants. And that's basically the, you know, kind of, I guess, the argument for the beginning of agriculture at least, right?

• 11:00Josh Clark?

  Yeah, where we basically said, that's a good looking plant. Let's just try to make that one grow as well as we can.

• 11:06Speaker 02

  That's right. So things are going along swimmingly. People are not moving around as much. They enjoy sitting for the first time and things like that. And then all of a sudden, the YD comes along and the glacial conditions return in the broad sense, in a very quick way. I mean, how long did it take? Like, I mean, the whole thing was like a thousand years, but we reached kind of close to that last glacial maximum in about 500 years.

• 11:35Josh Clark?

  Yeah, I think by 100 years, it was really like in full swing. And then, yeah, 500 years is basically like the Ice Age is back.

• 11:43Speaker 02

  I wonder if they were like, hey, does anyone think it's getting colder?

• 11:47Josh Clark?

  Right. No, just keep farming and be quiet.

• 11:50Speaker 02

  Right, yeah, yeah, just keep planting those plants.

• 11:52Josh Clark?

  We should also say Kyle helped us with this and he said that the younger Dryas came along and spoiled the party. That's truer than you would think because right before this in that boiling Alarad interstadiol was when we started making beer too. So that got disrupted as well.

• 12:10Speaker 02

  We'd be so much drunker today.

• 12:12Josh Clark?

  So another reason we would have wiped ourselves out in just one global bar fight, basically.

• 12:18Speaker 02

  Yeah.

• 12:19Josh Clark?

  So this kicks off 1,300 years of really, really cold weather. And then all of a sudden, it just stops and it comes along. It like happened, starting about 100 years, 500 years into it. It was really basically back to Ice Age conditions in a lot of places. But when it stopped, it swung back to nice and humid even faster. And there's actual ice cores from Greenland that show that Greenland in 10 years, the average temperature increased by 18 degrees Fahrenheit, 10 degrees Celsius. That is insane. And for comparison, so the global warming that's going on today

• 13:01Josh Clark?

  that scientists are quite concerned about and thinking people as well. That's a rise of 2 degrees Fahrenheit, not 18 degrees Fahrenheit, 2 degrees Fahrenheit in about 20 decades. We're talking about 18 degree rise in one decade. That's how fast this thing warmed up.

• 13:20Speaker 02

  Yeah, that's super quick. And again, you know, whenever you talk about this kind of stuff, you got to zoom out and look at it from a sort of macro point of view. But yeah, that's super fast and got super hot. And also super cold previously during the YDs, which was named, by the way, after a flower, the Dryas octopetalla. Yeah, nailed it.

• 13:45Speaker 02

  And the odd thing about this flower and why they named the YDs after it is that it it thrives in cold Arctic regions. It's one of these flowers that loves the ice, kind of the mountains of Scandinavia. And in the late 1800s, like the 1870s, Swedish scientists were studying clay deposits that they discovered, and they discovered this flower. And they were like, this flower shouldn't be here between these layers of clay. It was deposited by melting glaciers, but like, none of that makes any sense.

• 14:14Josh Clark?

  No, because you've got clay from melting glaciers above it and clay from melting glaciers below this flower. And this flower thrives in temperatures where the glaciers are not melting at all. So it was a huge mystery. And then what made it even more mysterious is that it was confirmed by other clay deposits elsewhere in Scandinavia. So there was definitely something weird going on. And they named it Younger Dryas because there actually had been an older Dryas before. That was not nearly as much of a bizarre freak as the Younger Dryas was.

• 14:44Speaker 02

  That's right. So we got the OD, we got the YD. Should we take a break? Yeah, that sounds like a pretty good time for a break, yeah?

• 14:52Josh Clark?

  Yeah, yeah.

• 14:54Speaker 02

  All right. We'll be right back.

• 15:21Josh Clark?

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• 16:24Josh Clark?

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• 18:38Josh Clark?

  So Chuck, we've been talking like pretty big shots, pretty confident here, right?

• 18:43Speaker 02

  Yeah, a couple of tough guys.

• 18:44Josh Clark?

  Exactly. And the reason why we're doing this is because of ice core samples, a lot from Greenland, also from Antarctica, and sedimentation from high-altitude European lakes. That's why we're talking so tough right now.

• 18:59Speaker 02

  Yeah, and those are big deals. You can find out a lot from an ice core. You can find out like basically what's, what it accumulated there, like stuff that the wind blew in there from other places. You know, they've got these little, little bubbles in that ice and you can trace gases even that were present back then and compare to like other parts of the world at that time. And like, oh, well, they have these gases here. We have this sediment here. We have a distinct lack of pollen for this period here, which means like probably a lot of plant life was killed off and stuff like that. And then the lake stuff is super valuable too, right?

• 19:36Josh Clark?

  Yeah, because constantly sediment is accumulating at the bottom of a lake and very similar stuff's getting trapped down there, like air bubbles, soot, pollen, all that stuff. And it just gets deposited year after year. And you can actually date that stuff. You can take a sample of the lake bottom and date that and then see what was going on around the lake at that time too. And lakes are advantageous because they're all All over the world. Ice shelves and glaciers are not all over the world. So you're limited from where you can take ice cores. And then also, lakes can last like thousands of years. Whereas if you're reading tree rings, you're reading maybe decades, maybe a century or two worth. A lake, it's going to give you way more than that.

• 20:18Josh Clark?

  So it's pretty clever, the way that they can take this stuff, not only figure out when this sediment deposit or this ice deposit was was put down, but also what like a lack of pollen or what type of pollen means for like the world at large at the time. I just think that's pretty cool that humans are able to do that. And they don't seem to just be making this up.

• 20:42Speaker 02

  You know, a very niche nerdy stuff, you should know t-shirt could just be

• 20:48Speaker 02

  lake bottom greater than symbol tree ring.

• 20:52Josh Clark?

  That's a super nerdy. I think that would actually offset the be dumb and happy one that you got generated.

• 20:59Speaker 02

  I think so, but just, you know, you walk around like Comic Con and somebody will say, I know exactly what you're doing, buddy.

• 21:05Josh Clark?

  And they'll, they'll just silently walk past you and give you the high five and the low five without stopping.

• 21:10Speaker 02

  Right, but it'll be a sort of a nerdy, they'll miss the high five, that won't be quite right. They'll try and fist bump you when you put up your hand or something.

• 21:17Josh Clark?

  Or they lock fingers with you on the low five and you guys keep trying to go in different directions.

• 21:22Speaker 02

  That's gotta be the worst. I thought the fist bump and the hand together was the worst, but when you high five and someone holds on and locks fingers. Not what you're after.

• 21:32Josh Clark?

  It's so weird.

• 21:34Speaker 02

  Oh goodness. I don't know why I think of Oprah Winfrey when, does she, has she ever done that?

• 21:39Josh Clark?

  I think she likes to raise people's hands like they just won a boxing match or something.

• 21:45Speaker 02

  All right, so we're settling into the YD. I mentioned earlier that the northern hemisphere was the one that was really affected the most, especially around the North Atlantic.

• 21:56Speaker 02

  The southern hemisphere, we'll, we'll talk about some weird abnormalities there as well. But these ice sheets advanced across the Arctic sea, just like they did during the old LGM, the last glacial maximum.

• 22:09Speaker 02

  Is it glacial or glacial?

• 22:11Josh Clark?

  Oh, I don't know. Depends on whether you say potato or patata.

• 22:15Speaker 02

  Yeah, I guess so. Uh, the Rockies here and what would later be the United States, uh, expanded. Uh, the Alps expanded. Um, they found very weird things like, uh, penguin-like creatures in southern Italy. Uh, like, things were getting really out of whack again, and everyone back then was like WTF?

• 22:34Josh Clark?

  Yeah, and, um, the, the, like, even if you weren't living in an iced over area, uh, you know, basically due south of that was tundra. Like, so Western Europe, which is nice and verdant and lush right now, was tundra at the time. You've got grasses, maybe a fox or two, if you're lucky, and you're bored just looking around, because it's not the most pleasant landscape to look at.

• 22:55Speaker 02

  Yeah.

• 22:56Josh Clark?

  I remember humans are running around at this time. I think, um, we are, we shrunk tremendously as a population down to maybe, the highest estimate I saw was around 10 million people across the entire planet at this time.

• 23:10Speaker 02

  That sounds nice, actually.

• 23:11Josh Clark?

  Yeah, kind of. Talk about Elba Room. But the, the, all the plants and animals that had started to thrive in the, the middle, in between the Ice Age and the YD, they died back. And all the animals and plants that had died back, uh, during the interstadial period, they came roaring back and they were like, we love the, we love the YD. We're happy again.

• 23:35Speaker 02

  Yeah, for sure. Uh, I mentioned the, the pollen retreating, um, being evidence of like, you know, the tree cover going away, and they found evidence of that in Ice Core once again. Uh, this is in the Hulu Cave in China, and it showed, you know, a drastic reduction in tree pollen, which, you know, basically you can infer that, like, yeah, a lot of, uh, a lot of trees died out during this icy period.

• 23:57Josh Clark?

  Right. And from that, you can also infer that there was probably less rain because trees help generate clouds, and they also help keep the planet warm. Um, so it was obviously a lot colder and a lot drier. That was the two characteristics of the YD. And then, um, like you said, the Southern Hemisphere experienced something radically different, right? So remember, Northern Europe is covered in ice again. It's tundra right below that. And then if you go down to Antarctica, they basically hand you like a lei and a Hawaiian shirt and like a Mai Tai.

• 24:34Speaker 02

  Yeah, it's so crazy. When I was going through this stuff, that to me was like the big reveal. I mean, I was, I'm a big dummy when it comes to this stuff. So I just figured that would have been even colder and even worse. But temperatures actually rose in the southern hemisphere and a lot of the southern hemisphere became warmer and wetter. And the sea surface temperatures increased in the Caribbean and the tropical Pacific and the mountains of New Zealand, it's all warmer conditions. So it was like, everything was kind of upside down all of a sudden.

• 25:05Josh Clark?

  Yeah, but you also mentioned earlier that it didn't happen. There were weird pockets here, there, which also goes to underscore how bizarre the Younger Dryas was. Like, there's a basin around Venezuela and it actually had temperatures drop. So this is the southern hemisphere, right? It saw a temperature drop of three degrees Celsius, five and a half degrees Fahrenheit. And every time I see something like that, I'm like, so? Like, that's not that big of a deal.

• 25:31Speaker 02

  Right.

• 25:31Josh Clark?

  It turns out, it is a really big deal. Even though to you, an average winter temperature of 55 going down to 50 doesn't sound all that bad. But climatologically speaking, any change in temperature, even by half degrees, has really huge weather consequences over, say, the course of a year. So in this case, dropping by three degrees Celsius or five and a half degrees Fahrenheit, it might not have seen that much temperature wise over an average winter. But it also opened up the door for way more freak weather. So they might have gone from like no blizzards whatsoever, maybe one blizzard a year, to three blizzards

• 26:13Josh Clark?

  a year. And that definitely impacts local conditions and the life there. So it makes a really big difference, even when you see little changes to average temperatures.

• 26:23Speaker 02

  Yeah, for sure. There were likely some animal extinctions happening. You mentioned the amount of humans, which was at an, you know, probably at an all time high at this point, started going back lower and lower. Their available food was getting slimmer and slimmer. We mentioned they were dabbing their toe in the pond of kind of settling down a little bit and not hunting and gathering and traveling everywhere. And all of a sudden, they had to pack it up and start moving around again to try and find food again.

• 26:53Josh Clark?

  Yeah, and the evidence that the that people, the human population contracted, meaning there was a lot of die off, shows up in archaeological sites like the Herensberg culture in present day Germany, Austria and Belgium. During the YD, the archaeological sites dropped by half compared to what they had been just before the YD, which suggests that there were a lot fewer people, making a lot fewer camps or villages. And then also, significantly, in North America, this is when the very famous Clovis culture just disappears from the record, too.

• 27:28Speaker 02

  Clovis. We did a whole episode on the Clovis.

• 27:30Josh Clark?

  Yeah, they used to pop up a bunch. Remember the whole Clovis first police and all that stuff?

• 27:35Speaker 02

  Yeah. Man, this feels like a thousand years ago.

• 27:37Josh Clark?

  It really does. But so this is when they disappeared. And they don't think that the Clovis all just died off, but they think that these weather conditions and hardships for living basically dispersed them and they started forming the prototypes to the bands of Native Americans that we see today.

• 27:53Speaker 02

  Yeah, for sure. Another interesting thing is, in, you know, sometimes in the times of trouble, there can be human advancement because you're struggling and need to think of better ideas on how to do what you're doing. And it seems like that might have happened with the hunting because the animals are more scarce, hunting is harder, the game is just not around. So this is where we saw at least one thing that we think might have been an advancement was the Harif Point, H A R I F, which is basically a new and improved arrowhead came about, and they think it's probably because they were struggling and they needed to kill better.

• 28:30Josh Clark?

  Yes. And it was quite an innovation because the arrowheads they were using before were made of dandelion heads.

• 28:35Speaker 02

  I know. And those, you know what? The animals loved them.

• 28:39Josh Clark?

  They did. They were like, shoot me again.

• 28:41Speaker 02

  Yeah, shoot one of those my way. I could use a laugh.

• 28:44Josh Clark?

  Right. And then also, Chuck, it really helps that there were people dabbling in agriculture before the YD came along, because it seems to have given the people related to them a bit of a leg up, like they didn't have to figure out agriculture from scratch under these conditions. So in pockets where there Was vegetation and a decent amount of game. People did settle down again in those areas. There's a place called the Zagros region, which is in modern Iran, which shows settlements that were basically probably not just hunting camps. They were probably permanent or semi-permanent settlements. So people did like sit down where they could and set up shop.

• 29:28Josh Clark?

  And as a matter of fact, some people say, okay, people were kind of dabbling in agriculture before, but it was just dabbling. And in fact, that's that culture might not have been passed along. It is possible that the younger Dryas did force humans to basically adopt agriculture. Because again, remember, conditions are so terrible that whatever leg up you, a human, can give to this plant that you're going to eat later is invaluable. So that's basically what agriculture is, is helping plants along to make them grow better.

• 30:00Speaker 02

  Yeah, and you know, that became a challenge in a lot of ways, not just because the ice, but they found, once again, in those ice deposits or the ice cores, they found air bubbles with a noted decrease in concentration of CO2 in the atmosphere.

• 30:16Josh Clark?

  Yeah.

• 30:17Speaker 02

  And so all of a sudden, these wild cereals that are growing, their yields are going to be way down. And, you know, they had some, you know, for the time, some fairly advanced agriculture burgeoning there. They were like pest control and like watering things, weeding things, transplanting things.

• 30:34Josh Clark?

  The basics.

• 30:36Speaker 02

  Yeah, the very basics, but that's, you know, the very beginnings. And, yeah, this put a big sort of stop sign in front of all of that.

• 30:44Josh Clark?

  Yeah, like imagine being the guy who is watching the other guy pour water out of his gazelle flask.

• 30:49Speaker 02

  Yeah.

• 30:50Josh Clark?

  Under like a little.

• 30:52Speaker 02

  The ground.

• 30:52Josh Clark?

  Yeah, like some wheat. Be like, what are you doing? And they'd say, just watch, just give me a couple thousand years and you'll be blown away.

• 31:01Speaker 02

  Yeah, you want this water to be beer one day, fella?

• 31:04Josh Clark?

  Exactly.

• 31:05Speaker 02

  Let me pour it on this grain.

• 31:07Josh Clark?

  Right, and then it magically turns into beer.

• 31:09Speaker 02

  Oh, man. Shall we take another break?

• 31:11Josh Clark?

  I think we shall, Chuck.

• 31:16Speaker 06

  Chuck and Josh. Stuff you should know.

• 31:38Josh Clark?

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• 31:47Speaker 02

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• 32:00Josh Clark?

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• 32:16Speaker 02

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• 32:40Speaker 02

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• 32:44Josh Clark?

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• 32:49Speaker 02

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• 32:53Josh Clark?

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• 33:00Speaker 02

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• 33:07Josh Clark?

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• 33:09Speaker 02

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• 33:22Josh Clark?

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• 33:34Josh Clark?

  Everyone has a story to tell. What's yours? The moment you met your partner, landed that promotion? For people living with a rare disease, life can feel divided into before the diagnosis and all the after moments that follow. On Voices of Vivgard, Vivgard is also known as its generic name, Fgard Tigamod Alpha Fcab, you'll hear powerful stories from people facing challenges and embracing a life with a rare disease.

• 33:58Speaker 02

  Join host Andra Stratten as she guides listeners through honest conversations about life after diagnosis. You'll hear how each guest worked with her care team on their treatment plan, as well as their personal challenges, setbacks, progress, and moments of connection.

• 34:11Josh Clark?

  These stories reveal that life is bigger than a moment, a condition, or a tough day. Listen to Voices of Vivgard on the iHeart Radio app, Apple Podcasts, or wherever you get your podcasts.

• 34:37Speaker 02

  All right, we should talk a second about something called solar insulation, not insolation, insulation with an O. And this is how much solar warmth reaches the Earth's upper atmosphere. And the basic pattern of warming the globe is driven by this. And the Younger Dryas is definitely like this weird, exceptional pocket that stands out. And because of this, everyone that nerds out on this kind of stuff was like, well, we got to figure this out. I mean, why did this happen? And they have emerged with four main hypotheses. The one that has the most traction we're going to start with is the melt-water interrupting thermohaline circulation.

• 35:22Speaker 02

  And that sounds very sort of like sciency and nerdy. And like, guys, I hope you explain this. But it's really very simple.

• 35:29Josh Clark?

  It is.

• 35:29Speaker 02

  Is that a bunch of water disturbed the warming cycle of the ocean very, very quickly.

• 35:36Josh Clark?

  Yeah, specifically in the North Atlantic, which has this thing that you mentioned. Thermohaline circulation, which is where warm water warmed by surface air on top of the ocean falls down into the deep water. And as it does it, it displaces the cold water, which comes up to the top and gets warmed itself. Then it sinks and the cycle just keeps going on and on. Right? This is how warmth is delivered to the north, the northern hemisphere. Right? Those it moves northward. So the warmer sea water is always moving toward the north. So it's delivering warmth. And at the same time, that cold water upwells in the southern hemisphere.

• 36:19Josh Clark?

  So it delivers cold to the southern hemisphere, which is why, under normal conditions with the thermohaline circulation, the Antarctica is cold and comparatively speaking, the northern hemisphere is warmer.

• 36:32Speaker 02

  That's right. All right. So park that in your, in your brain. And then understand that North America at the time had this huge 700 mile by 200 mile lake called Lake Agassiz, I guess.

• 36:47Josh Clark?

  Sure.

• 36:48Speaker 02

  Agassiz, if you're an Andre Agassi fan. It developed as the Laurentide Ice Sheet and extended down to the Great Plains and blocked the Great Lakes. And all the rivers that were flowing there backed up and it formed this big natural reservoir that was 700 by 200 miles big. And this theory holds, the meltwater theory holds, that as that last glacial maximum warmed things up, that ice sheet retreated. The blocked passage to those Great Lakes opened up and all of a sudden billions and billions of gallons of fresh water make its way down to the North Atlantic. They think a similar sort of thing happened in the, in the Nordic region. But you're like, all right, so that makes sense. But was this water like super cold or something?

• 37:32Speaker 02

  It was cold, but the main thing it did was desalinate that, that upper ocean water. Right?

• 37:38Josh Clark?

  Yeah. And so fresh water is less dense than sea water. And so a bunch of fresh water mixed in with sea water makes it less dense than it normally would be. And it needs to be dense to fall down to the deep ocean. Uh, which makes the other deeper water come back up, right?

• 37:55Speaker 02

  Yeah.

• 37:55Josh Clark?

  So that means that the thermo haline circulation is interrupted. And if you have an interruption in the thermo haline circulation, it just stops moving like that. You would expect to see the northern hemisphere get cold because there's warmth is not being delivered there any longer. You'd also expect to see Antarctica warm up because that cold, deep ocean water is not welling up around the very southern, southern hemisphere. And that's exactly what you see with the Younger Dryas. It's a really beautiful, elegant explanation that I think was hypothesized in 1982. And up until very, very recently, you were a fringy nut. If you believed anything besides that as the explanation for where the Younger Dryas came from.

• 38:41Speaker 02

  Yeah, I mean, it makes sense to me, uh, but that's why I love science is people keep poking around and the fringe nut maybe one day is proven somewhat right. Uh, and that, well, I still think that the meltwater is probably the, the, the reason why, but, um, one of the other hypotheses is the impact hypothesis. And that is, like you said, was pretty controversial until more recently. Um, it has gained a little bit of traction because some things do kind of add up. But the idea here is that a meteorite or a comet or something impacted the earth, maybe an air burst even. And that released a thermal pulse that kind of set the, the world on fire almost like all these massive wildfires across all the continents.

• 39:25Speaker 02

  Uh, the air is filled with soot, it's blocking sunlight. And in fact, it's, there's so much that there's atmospheric dust such that you reduce solar radiation and all of a sudden you have what's called an impact winter or, you know, kind of like a, like a new, the idea of a nuclear winter.

• 39:41Josh Clark?

  Yeah, basically the same exact result, but just it was different things that got us there, right? So, um, there's evidence for this that most people point to as like, this is pretty good evidence. There's something called a black mat, which is a layer of carbon matter. That seems to be a soot deposit that you find all over North America. And in parts of Europe. And all that suggests that there were wildfires going on on different continents at the same time.

• 40:10Speaker 02

  Yeah.

• 40:10Josh Clark?

  Which would suggest like some sort of massive comet or meteorite bursting and setting off this thermal pulse. So the fact that those things coincide on two different continents with the onset of the Younger Dryas has definitely made the the impact hypothesis much more popular than it was before. One thing detracting from it that probably makes some legitimate scientists wary of embracing it publicly right now is the writer and science contrarian Graham Hancock latched on to the impact hypothesis. Because he has this theory, I guess you could call it that, that there was an ancient apocalypse

• 40:52Josh Clark?

  around the time that the Younger Dryas happened that wiped out massively advanced civilizations that we don't even know it really existed and reset humanity. And then we had to rebuild from there. And there's not a lot of evidence, if any, for this stuff. It's really, really fascinating, but the the evidence we do have, the scientific evidence we do have, doesn't set that up. But anyway, he basically said, see, this impact hypothesis supports my idea that there was an ancient apocalypse. And scientists tend not to agree with Graham Hancock much.

• 41:25Speaker 02

  Yeah, and the other thing, there's a couple of more sort of smaller points that might support this. One is there was a platinum spike in South Africa that preceded the YD. And in some other places and platinum is, you know, a lot of time within meteorites. So maybe some support there. And also sometimes people kind of combine the first one and say, maybe there was an impact combined with this meltwater thing. So there was a low atmospheric explosion over North America. And that's what released all this meltwater all over the place.

• 41:58Josh Clark?

  Yeah, which makes sense. It's basically like handing an olive branch from one hypothesizer to another, you know? Let's work together.

• 42:06Speaker 02

  Yeah, let's go get a drink and just settle it.

• 42:08Josh Clark?

  Also, as an aside for remember our Gobleki Tepe episode?

• 42:13Speaker 02

  Oh, yeah.

• 42:14Josh Clark?

  It's been a while. I don't remember exactly how to pronounce it. We talked about how there was this guy who who. Also kind of fringily concluded that some astronomical engravings at the the site recorded the the comet or the meteorite burst that happened at this time. Which is kind of cool, but again, there's not a lot of evidence to support it. Moving on, there's a couple of other explanations that don't have nearly as much traction, but they do make sense. One is a supernova explosion. Supposedly, a star went supernova in the Vela constellation at the right time that could have affected Earth by burning away its ozone layer, which would cool the upper stratosphere,

• 42:57Josh Clark?

  which is the second most layer above Earth, which would prevent it from holding much water vapor. Water vapor is a greenhouse gas, and without a very strong greenhouse gas in the atmosphere, heat would just go out into space much more easily from Earth, and it would get cooler as a result. The problem with this one that I have is wouldn't that happen all over the planet if the ozone layer was burned away by a supernova?

• 43:21Speaker 02

  I think so.

• 43:22Josh Clark?

  So I'm gonna, I'm gonna toss that one, okay?

• 43:25Speaker 02

  Yeah, nailed it. The last one is another sort of example where the sun is blotted out, so there's a massive drop in temperature very quickly. But this time, it is because a volcano erupted, a massive volcano. This is the Locker Sea volcano, not C E A, or I'm sorry, S E A, but S E E, because we all know that Germany doesn't have any water, right?

• 43:53Josh Clark?

  Yeah, well, it's landlocked, yes.

• 43:55Speaker 02

  Yeah, but this was a German volcano. Of course, we're kidding. That's a reference to an older episode. We know all about the Black Sea. So hold your emails. But this volcano, it was definitely a mega eruption. It spewed 6.3, I mean, what is that even? Trillion?

• 44:11Speaker 02

  What is that?

• 44:12Josh Clark?

  That's a cubic kilometers.

• 44:15Speaker 02

  So 3 million cubic kilometers?

• 44:17Josh Clark?

  No, 6.3 cubic kilometers.

• 44:21Speaker 02

  To the third power, though.

• 44:23Josh Clark?

  No, so that's what makes it cubic. So if you took a kilometer of land.

• 44:28Speaker 02

  Oh, yeah, yeah, yeah.

• 44:30Josh Clark?

  And you made it square and you did 6.3 times. And then you also made it a kilometer tall. A cube that's 6.3 kilometers on each side.

• 44:40Speaker 02

  Yeah.

• 44:40Josh Clark?

  Just of magma got released from that volcano. It was a massive eruption.

• 44:47Speaker 02

  Yeah, I just outed myself in a mathematical way.

• 44:52Josh Clark?

  Well, finally, you did. I'm the one who does it all the time.

• 44:56Speaker 02

  Well, comparatively speaking, Mount St. Helens released 1 cubic kilometer. Vesuvius was 3, and this was 6.3. So the other interesting thing about this one is volcanoes can produce platinum.

• 45:09Josh Clark?

  Yeah.

• 45:09Speaker 02

  Or at least, you know, part of like groups of platinum metals. And that could account for that spike we talked about in South Africa.

• 45:17Josh Clark?

  Yes. And so the volcanic eruption hypothesizers frequently say, hey, how about this? A volcano erupted and attracted a comet that blew up over North America, which kicked off the melting of the ice caps, which caused the thermohaline circulation problem. Yeah. And then the supernova person's like, what about me? And they're like, sorry, you're not invited.

• 45:39Speaker 02

  You were dismissed.

• 45:40Josh Clark?

  Exactly.

• 45:42Speaker 02

  All right. So that was the YDs. I guess we could talk a little bit about what happened afterward. Afterward is where we are, the Holocene period. And that was when the climate finally worked itself out. That pendulum stopped swinging and things started warming up and stabilizing. And, you know, people started thriving again. The animals came out. The birds started chirping. The bees started pollinating and it led to, you know, not the modern, modern era, but just, you know, what we know now is Planet Earth.

• 46:18Josh Clark?

  Yeah, the beginnings of our era all find its root. Roots in this this time, like this is where agriculture developed. This is where civilization first developed. Writing came along a few thousand years later. I mean, all of this happened in a really short period of time. Like essentially, everything that has to do with like human civilization began in the 10,000 years immediately following the Younger Dryas.

• 46:43Speaker 02

  Yeah, I mean, the current, the current shape of our planet happened after the Younger Dryas. Like the, the, the way the coastlines were shaped. I mentioned the Rockies and the Alps, you know, those, those mountain ranges all over the world even. They, they, I was about to say took their final shape, but of course that's not true. But took the shape that we know and love today.

• 47:03Josh Clark?

  Yeah, and that's actually one reason why it's difficult to track what humans were doing during the Younger Dryas, because the, the settlements that they had that were closer to the coastline then are now under hundreds of feet of ocean water and are probably just totally destroyed. So we, we lost a lot of archaeological sites because of that sea level rise. But it was a trade off because again, we have writing.

• 47:26Speaker 02

  Yeah, that's right. And those wild cereals that we talked about that were having such a hard time, you know, became Captain Crunch.

• 47:34Josh Clark?

  Yeah. And really, is there anything more you need to prove that humans have reached peak civilization than that?

• 47:42Speaker 02

  I don't think so.

• 47:43Josh Clark?

  Uh, okay. Well, I guess that's it for the YD, right Chuck?

• 47:48Speaker 02

  Uh, that's it for now. I mean, who knows what's ahead?

• 47:52Josh Clark?

  Well put. And because Chuck said, who knows what's ahead? Truly, it's time for listener mail.

• 48:02Speaker 02

  Uh, this is called birthmark episode, because we, I think that might've been a select or maybe Patrick just listened to it again. I think so. That's what happened. Hey guys, listen to that episode again recently because I have a birthmark that makes me perpetually look like I have a black eye. On a regular basis, someone will ask me some variation of like, who punched you? What happened to your face? I used to enjoy giving a clever story as a way to mess with them, like getting kicked out of a nightclub or squaring off with a bear. But I started to feel bad for lying even to my friends, even if only for a minute. So now I usually just take the boring route and explain that it's a birthmark. It's just subtle enough that friends can go years without noticing it even.

• 48:43Josh Clark?

  Wow.

• 48:43Speaker 02

  But once it's brought to their attention, they can't unsee it. Many don't believe me when I tell them it's just a birthmark and they think I'm trying to cover something up. My mom even told me that she was interrogated when I was a child by doctors.

• 48:56Josh Clark?

  Oh, wow.

• 48:57Speaker 02

  And would get dirty looks from other parents when they noticed a mark on my face. And I feel bad that her experience of my birthmark has never been as fun as mine. Anyway, ever since my wife Christine introduced me to your show about nine years ago, Stuff You Should Know has been a staple for us during house chores and road trips. Your chemistry together is very comforting and we especially like hearing Josh make Chuck laugh. Do it right now.

• 49:17Josh Clark?

  Hot potato.

• 49:20Speaker 02

  That actually worked. I was like, I'm gonna have to fake a laugh here, but you got me.

• 49:26Josh Clark?

  Awesome.

• 49:26Speaker 02

  Keep up the great work, guys. Thanks for making the two of us smile again and again and again. We've made them smile three times. All the best from Troutdale, Oregon. That is Patrick Burton.

• 49:37Josh Clark?

  Awesome, Patrick. Thank you for that. Patrick and his wife Christine, right?

• 49:41Speaker 02

  Yep.

• 49:42Josh Clark?

  So thanks to you both. And Patrick, I have to say, if you're going to have a birthmark that's not in the shape of Abraham Lincoln, the place that you have it is about as cool as it can be.

• 49:52Speaker 02

  Agreed.

• 49:53Josh Clark?

  If you want to be like Patrick and Christine and let us know how long you've been listening to us and what you think, hopefully it's generally positive, you can send us an email, too. Send it off to [email protected].

• 50:06Speaker 00

  Stuff You Should Know is a production of iHeartRadio. For more podcasts, iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.

• 50:24Josh Clark?

  Buy smart, drive for less and trade for more. That's Toyota affordability and it starts with a great deal on an off-road ready Tacoma or half-ton Tundra, two of Toyota's longest lasting trucks, combining power for work, tech for adventures and style in between. And they're built on a reputation for quality and reliability, which is why Toyota trucks are known for holding their value, which could mean big savings when it's time for your next Toyota. So get a great deal today and a great value tomorrow. Shop toyota.com for more. Toyota, let's go places. Introducing Voices of Vivgard. Vivgard is also known as its generic name, Fgard Tigamod Alpha F-Cab. And this new show features firsthand stories from people living with a rare disease.

• 51:06Josh Clark?

  Hosted by Andrew Stratton, these perspectives highlight that life is more than a moment, a condition, or a tough day. Living with a rare disease can be challenging, but it does not define the Voices of Vivgard. In these episodes, they share their stories, from diagnosis to working with their care team on their treatment plan. Listen to Voices of Vivgard on the iHeart Radio app, Apple Podcasts, or wherever you get your podcasts.

• 51:29Speaker 02

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• 51:58Speaker 06

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• 52:00Speaker 07

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