[Insert Your Own Catchy Title About Younger Dryas Here]

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1:01John Polk story on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Hi, I'm Dr. Priyanka Wally. And I'm Hari Kondabolu. It's a new year. And on the podcast Health Stuff, we're resetting the way we talk about our health. Which means being honest about what we know, what we don't know, and how messy it can all be. I like to sleep in late and sleep early. Is there a chronotype for that or am I just depressed? Yes. Health stuff is about learning, laughing and feeling a little less alone. Listen on the iHeartRadio app, Apple Podcasts or wherever you get your podcasts. Welcome to Stuff You Should Know, a production of iHeartRadio.

1:49Hey, 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. Hot potato? Mm-hmm. That's how Emily's family says potato. I think I would only say it when it's preceded by hot. I would only say it like, 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. Nor would you say a hot potato. Like, what a square. Yeah, that is pretty square, isn't it? Get the stick out of your butt, fella. Loosen up.

2:27Loosen up. Get the cardigan out from around your shoulders. Yeah, geez. So that was obscure, but still. 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. Oh, wow. What we're talking about is something called the Younger Dryas, which is a pretty terrible name for this if you want to be catchy, right? Yeah. I mean, I think a lot of people would probably say WTF. Right. Let's just call it the YD if we're going to put initials on things. How about that?

3:07Or abbreviate things. So the YD, the Unger Dryas, is 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. Yeah. And a time, as we'll see, where the Earth and its inhabitants and animals and nature was all going like, all right, thank God we can we can finally get down to business and start being an Earth, like a legit Earth.

4:06And then, you know, the YDs come along and say, not so fast. 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, 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. Yeah. Like, 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 Wisconsinian ice age that we're talking about.

4:50The last one was 250 million years before, right? So it was 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 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. 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.

5:40But let's say as far along this goes, we would be like the year 3000 something. Right. 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? The second one. Okay. All right. So it's a good thing this happened or we wouldn't be talking about it right now. Exactly. That's exactly right. So, yeah, that's a really anthropic way of looking at it. Well. Speaking of, I bought a copy of If Anyone Builds It, Everyone Dies, the Eliezer Yukowski-Nate Soros book that just came out. Okay. I did not know about it.

6:18You say that as if it was just on the tip of my tongue, which I appreciate. No, you do. We remember I basically mischaracterized it in the Zizians episode and had that book, right? About building AI. And if anyone builds it, then we're all going to die. Like just the existential threat of AI. It is really good. You could read it in if you had 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. Great. 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.

7:00Yeah, so it was very icy. There were huge ice sheets covering a lot of Earth, like most of North America, Northern Europe, and Asia. And as we'll see, a lot of 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. But lots of ice everywhere. We had barren plains, very harsh conditions. We had things like, you know, woolly mammoths, like ice loving creatures dwelling the earth. and, you know, human populations that were sparse and scattered and constantly kind of moving around trying to survive.

7:43Right. And so the last ice age started about 100 ,000 years ago, and it took about 80 ,000 years to reach its peak point. So 20 ,000 years ago, it hit what's called the last glacial maximum, right? So it took 80 ,000 years to get there and then 10 ,000 years to basically melt. It melted a lot faster than it developed. And just like right after it peaked, it just started warming up and it took about 9000 years. And all of the ice sheets, all the glaciers, all this stuff that was covering Earth and keeping it in an ice age just basically went away. And Earth just blossomed into a version that we like.

8:23Yeah. And it became, you know, not terribly unlike what we're looking at now. There was a jump in temperatures that was, you know, kind of close-ish to today. And this was called the, I never know how to pronounce. It's an umlaut. Is it really? Yeah. That's all it is. Yes. So all of our Nordic friends, the circle with the forward slash through or the O with the forward slash through, that's an umlaut, right? Okay. I mean, I guess we call it the null set because it looks like a zero with a slash through it. So call it that. I mean, we don't really call it that, but that's what it looks like. Pronounce it like that.

8:56All right. What? With the umlaut? No, the null set. No. I wouldn't know how to do that. But with the umlaut, I guess my best stab would be the Burling Alarud Interstadial. I think you nailed it. All right. A lot more rain. 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 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 the only humans that are around at this point.

9:39And 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. 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 was 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.

10:19This is where we started taking our first stabs at agriculture. 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 and 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. They're like, what is farming? They're like, you're doing it right now, buddy. I see you over there picking weeds. Exactly. And tending to those wild plants. And that's basically the, you know, kind of, I guess the argument for the beginning of agriculture, at least, right?

10:57Yeah, where we basically said, that's a good looking plant. Let's just try to make that one grow as well as we can. 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. Yeah. I think by a hundred years, it was really like in full swing.

11:38And then, yeah, 500 years is basically like the ice age is back. I wonder if they were like, hey, does anyone think it's getting colder? Right. No, just keep farming and be quiet. Right. Yeah. Yeah. Just keep planting those plants. 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 bullying Olorod interstadial was when we started making beer too. So that got disrupted as well. We'd be so much drunker today. So another reason we would have wiped ourselves out in just one global bar fight basically.

12:17Yeah. So this is, off 1300 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 that scientists are quite concerned about and thinking people as well, that's a rise of 2 degrees Fahrenheit.

13:08Not 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. 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 Octopetala. Yeah, nailed it. And the odd thing about this flower and why they named the YDs after it is that it thrives in cold Arctic regions.

13:49It'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 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 none of that makes any sense. 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.

14:30So 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. 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, yay? Yeah, yay. All right. We'll be right back.

14:59Chuck and Josh.

15:04Stuff you should. No.

15:17New year, new goals, and in this economy, a better money plan is more necessary than ever. I am Matt. And I'm Joel. We are from the How to Money podcast, and every week we help you to spend smarter, save more, and make sense of what's going on out there. If you want 2026 to be the year you finally feel in control of your money, we're here to give you the tools and advice to help you make it happen. Listen to How to Money on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Hi, I'm Dr. Priyanka Wally. And I'm Hari Kondabolu. It's a new year, and on the podcast Health Stuff, we're resetting the way we talk about our health.

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17:55So, Chuck, we've been talking like pretty big shots, pretty confident here, right? Yeah, a couple of tough guys. Exactly. And the reason why we're doing that 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. Yeah, and those are big deals. You can find out a lot from an ice core. You can find out, like, basically what it accumulated there, like stuff that the wind blew in there from other places. You know, they've got these 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.

18:39And, like, oh, well, we 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? 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 a lake bottom and date that and then see what was going on around the lake at that time too.

19:16And lakes are advantageous because they're 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 is going to give you way more than that. 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 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 you know a very niche nerdy stuff you should know t-shirt could just be lake bottom greater than symbol tree ring that's a super nerdy i think that would actually offset the be dumb and happy one that you got generated.

20:16I think so. But just, you know, you walk around like Comic-Con and somebody will say, I know exactly what you're doing, buddy. And they'll just silently walk past you and give you the high five and the low five without stopping. Right, but it'll be a sort of a nerdy, they'll miss the high five. It won't be quite right. They'll try and fist bump you when you put up your hand or something. Or they lock fingers with you on the low five and you guys keep trying to go in different directions. That's got to 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.

20:50It's so weird. Oh, goodness. I don't know why I think of Oprah Winfrey when does she has she ever done that? I think she likes to raise people's hands like they just want a boxing match or something. All right. So we're settling into the YD. I mentioned earlier that the northern hemisphere was one that was really affected the most, especially around the North Atlantic. The southern hemisphere, 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. Is it glacial or glacial? Oh, I don't know.

21:30Depends on whether you say potato or patata. I guess so. The Rockies here in what would later be the United States expanded. The Alps expanded. They found very weird things like penguin-like creatures in southern Italy. Like, things were getting really out of whack again, and everyone back then was like WTF. Yeah, and even if you weren't living in an iced-over area, 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.

22:10Because it's not the most pleasant landscape to look at. And remember, humans are running around at this time. I think 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. That sounds nice, actually. Yeah, kind of. Talk about elbow room. But all the plants and animals that had started to thrive in the middle in between the Ice Age and the YD, they died back. And all the animals and plants that had died back during that interstitial period, they came roaring back. And they were like, we love the YD. We're happy again.

22:52Yeah, for sure. I mentioned the pollen retreating being evidence of, like, you know, the tree cover going away. And they found evidence of that in Ice Core. Once again, 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 trees died out during this icy period. 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. So it was obviously a lot colder and a lot drier. That was the two characteristics of the YD.

23:31And then, 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. Yeah, it's so crazy. When I was going through this stuff, that to me was like the big reveal. I mean, 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.

24:11and the sea surface temperatures increased in the Caribbean and the tropical Pacific and the mountains of New Zealand saw warmer conditions. So it was like everything was kind of upside down all of a sudden. 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.

24:49It 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 a year.

25:32And that definitely impacts local conditions in the life there. So it makes a really big difference even when you see little changes to average temperatures. Yeah, for sure. There were likely some animal extinctions happening. You mentioned the amount of humans, which was 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.