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Welcome to Stuff You Should Know, a production of iHeartRadio.

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.

Hot potato?

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, and loosen up.

Loosen 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 brushstroke overview with 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.

Well, let's just call it the the YD if we're going to, if we're going to put initials on things.

How about that?

Or abbreviate things.

So

the YD, the Younger 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.

And 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, 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.

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 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 legit Earth, like I said

before,

you know,

I mean, it would obviously wouldn't change the year, but let's say as far as longness 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, um, speaking of, I bought a copy of If Anyone Builds It, Everyone Dies, the Eleazar Yukowski Natesaura's book that just came out.

Okay.

I did not know about it.

You 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 to

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.

Yeah, 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

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.

Right.

And so that 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 9,000 years.

And all the ice sheets, all the glaciers, all the 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.

Yeah.

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, and I never know how to to pronounce it.

It's an umlaut.

Is it really?

Yeah, I'm 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.

All right.

What, what, with the umlaut?

No, the null set.

No.

I wouldn't know how to do that.

With the umlaut, I guess my best stab would be the Berling-Allarud

Interstadial.

I think you nailed it.

All right.

A lot more rain.

We got a, 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, 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

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.

Yeah, this was actually right before this was the point when people from Eurasia migrated into North America.

So this was 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.

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 that energy and that time that we dedicate to hunting and gathering and put it into farming i i just made that word up but let's call it that from now on

like what is farming and they're like you're doing it right now buddy i see over there picking weeds exactly and uh 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 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 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 100 years, it was really like in full swing.

And 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, um, Kyle helped us with this, and he, he, um, he said that the, the younger dryest came along and spoiled the party.

Um, that's truer than you would think because right before this in that um bulling allorod 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 yeah

so um this is this kicks off 1300 years of really really cold weather um

and then all of a sudden it just stops and it it it comes along it like happened starting about a hundred 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 two 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.

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 driest

octopatala.

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.

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 no because you've got clay from melting glaciers above it and clay from melting glaciers below this flower and this flower thrives in in uh temperatures where the glaciers are not melting at all so it's a huge mystery and then um 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.

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?

Yeah, yeah.

All right,

we'll be right back.

Junk

and Josh

stuff

you

should know

you're thoughtful about where your money goes you've got your core holdings some recurring crypto buys maybe even a few strategic options plays on the side the point is you're engaged with your investments and public gets that that's why they built an investing platform platform for those who take it seriously.

On Public, you can put together a multi-asset portfolio for the long haul.

Stocks, bonds, options, crypto, it's all there.

Plus an industry-leading 3.8% APY high-yield cash account.

Switch to the platform built for those who take investing seriously.

Go to public.com and earn an uncapped 1% bonus when you transfer your portfolio.

That's public.com.

Paid for by Public Investing.

All investing involves the risk of loss, including loss of principal.

Brokerage services for U.S.-listed registered securities, options, and bonds in a self-directed account are offered by Public Investing Inc., member Finrun SIPC.

Crypto trading provided by Backed Crypto Solutions LLC.

Complete disclosures available at public.com/slash disclosure.

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

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's 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 and like oh well we have these gases here we have this sediment here

we have a 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.

And 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, it's 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.

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.

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 that's pretty cool.

When you high five and someone holds on and locks fingers,

it's not what you're after.

It'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 won a boxing match or something.

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.

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.

Depends on whether you say potato or potata.

Yeah, 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 the, like, 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 because it's not the most pleasant landscape to look at.

Yeah.

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.

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 interstadial period, period, they came roaring back.

And they were like,

we love the YD.

We're happy again.

Yeah, 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 IceCore 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.

And 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 lay 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.

And 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.

Right.

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 a year.

And 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 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.

Yeah, and the evidence that people, the human population contracted, meaning there was a lot of die-off,

shows up in archaeological sites like the Hererensburg 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 are 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.

Clovis.

We did a whole episode on the Clovis.

Yeah, they used to pop up a bunch.

Remember the whole Clovis first police and all that stuff?

Yeah.

Yeah.

God, man, this feels like a thousand years ago.

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.

Yeah, for sure.

Another interesting thing is,

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 a...

Basically, a new and improved arrowhead came about, and they think it's probably because they were struggling and they needed to kill better.

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

I know.

And those, you know what?

The animals loved them.

They did.

They were like, shoot me again.

Yeah, shoot one of those my way.

I could use a laugh.

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.

And as a 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 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.

Yeah.

And, you know,

that became a challenge in a lot of ways, not just because of 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.

And so all of a sudden, these wild cereals that are growing, their yields are going to be way down.

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.

The basics.

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.

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

onto like a like a little ground.

Yeah, like some wheat.

He'd be like, what are you doing?

And they'd say, just watch.

Just give me a couple thousand years and you're going to be blown away.

Yeah.

You want this water to be beer one day, fella?

Exactly.

Let me pour it on this grain.

And then it magically turns into beer.

Oh, man.

Shall we take another break?

I think we shall, Chuck.

Chuck

and

Josh.

Stuff

you

should know.

You're thoughtful about where your money goes.

You've got your core holdings, some recurring crypto buys, maybe even a few strategic options plays on the side.

The point is, you're engaged with your investments, and Public gets that.

That's why they built an investing platform for those who take it seriously.

On Public, you can put together a multi-asset portfolio for the long haul.

Stocks, bonds, options, crypto, it's all there.

Plus an industry-leading 3.8% APY high-yield cash account.

Switch to the platform built for those who take investing seriously.

Go to public.com and earn an uncapped 1% bonus when you transfer your portfolio.

That's public.com.

Paid for by Public Investing.

All investing involves the risk of loss, including loss of principal.

Brokerage services for U.S.-listed registered securities, options, and bonds in a self-directed account are offered by Public Investing Inc., member Finrun SIPC.

Crypto trading provided by Backed Crypto Solutions LLC.

Complete disclosures available at public.com slash disclosure.

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All right, we should talk a second about something called solar insulation, not insulation, insulation with a no.

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've 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 meltwater interrupting thermohaline circulation.

And that sounds very sort of like sciencey and nerdy.

And like, guys, I hope you explain this, but it's really very simple.

It is.

It's that a bunch of water disturbed

the warming cycle of the ocean very, very quickly.

Yeah, specifically in the North Atlantic, which has this thing, you mentioned the thermohaline circulation, which is where warm water warmed by surface air on top 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?

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.

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.

That's right.

All right.

So park that 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.

Sure.

Agassiz, if you're an Andre Agassiz 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 block passage to those great lakes opened up, and all of a sudden, billions and billions of gallons of freshwater make its way down to the North Atlantic.

They think a similar sort of thing happened in the Nordic region.

But you're like, all right, so that makes sense.

But was this water like super cold or something?

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

Yeah.

And so

fresh water is less dense than seawater.

And so a bunch of freshwater mixed in with seawater makes it less dense than it normally would be.

And it needs to be dense to fall down to the deep ocean, which makes the other deeper water come back up, right?

Yeah.

So that means that the thermohaline circulation is interrupted.

And if you have an interruption in the thermohaline 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.

Yeah, I mean, it makes sense to me.

But that's why I love science is people keep poking around and the fringe nut maybe one day is proven somewhat right.

And that, well, I still think that the meltwater is probably the reason why.

But one of the other hypotheses is the impact hypothesis.

And that is, like you said, was pretty controversial until more recently.

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 airburst even.

And that released a thermal pulse that that kind of set the the world on fire almost, like all these massive wildfires across all the continents.

The air is filled with soot, it's blocking sunlight.

And in fact, it's there's so much soot, 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

the idea of a nuclear winter.

Yeah, basically the same exact result, but just it was different things that got us there, right?

So 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,

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 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 onto the impact hypothesis because he has this theory,

I guess you could call it that, that there was an ancient apocalypse around the time that the Younger Dryas happened that wiped out massively advanced civilizations that we don't even know 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 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.

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.

Yeah, which makes sense.

It's basically like handing an olive branch from one hypothesizer to another.

You know, let's work together.

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

Also, as an aside, remember our Goblecki Tepe episode?

Oh, yeah.

It's been a while.

I don't remember exactly how to pronounce it.

We talked about how there was this guy who

also kind of fringedly concluded that some astronomical engravings at the site recorded 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 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, 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?

I think so.

So

I'm going to toss that one, okay?

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 C 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?

Well, it's landlocked, yes.

Yeah, but this is 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,

what is that?

That's cubic kilometers.

So 3 million cubic kilometers?

No, 6.3 cubic kilometers.

To the third power, though.

No, so that's what makes it cubic.

So if you took a kilometer of language

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

just of magma got released from that volcano.

It was a massive eruption.

Yeah,

I just outed myself

in a mathematical way.

Well, finally, you did.

I'm the one who does it all the time.

Well, comparatively speaking, Mount St.

Helens released one cubic kilometer.

Vesuvius was three, and this was 6.3.

So

the other interesting thing about this one is volcanoes can produce platinum,

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.

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

frontal haline circulation problem.

Yeah.

And then the supernova person's like, what about me?

And they're like, sorry, you're not.

She said you were dismissed.

Exactly.

All right.

So that was the Y D's.

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

not the modern, modern era, but just what we know now as planet Earth.

Yeah, the beginnings of our era all find its roots in 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.

Yeah, I mean,

the current shape of our planet happened after the Younger Dryest.

Like the way the coastlines were shaped, I mentioned the Rockies and the Alps, you know, those

mountain ranges all over the world, even.

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.

Yeah, and that's actually one reason why it's difficult to track what humans were doing during the Younger Dryas, because 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 lost a lot of archaeological sites because of that sea level rise.

But it was a trade-off because, again, we have riding.

Yeah, that's right.

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

Yeah.

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

No, I don't think so.

Okay, well, I guess that's it for the YD, right, Chuck?

That's it for now.

I mean,

who knows what's ahead?

Well put.

And because Chuck said who knows what's ahead, truly, it's time for listener mail.

This is called Birthmark

episode, because we, I think that might have been a selector.

Maybe Patrick just listened to it again.

I think so.

That's what happened.

Hey guys, listened 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.

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

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 tours and road trips.

Your chemistry together is very comforting and we especially like hearing Josh make Chuck laugh.

Do it right now.

Hot patata.

That actually worked.

I was like, I'm going to have to fake a laugh here, but you got me.

Awesome.

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.

Awesome, Patrick.

Thank you for that.

Patrick and his wife, Christine, right?

Yep.

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.

Agreed.

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 stuffpodcast at iHeartRadio.com.

Stuff You Should Know is a production of iHeartRadio.

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