Stuff You Should Know - How Extinction Works

Episode Date: October 21, 2014

Scientists believe that 99% of the estimated 50 billion species that have ever lived on Earth have disappeared through extinction. This is a natural process typically, but it can also be cataclysmic and it's becoming clear we are amid a massive one. Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

I'm Munga Shatikler and it turns out astrology is way more widespread than any of us want to believe. You can find it in Major League Baseball, International Banks, K-Pop groups, even the White House. But just when I thought I had a handle on this subject, something completely unbelievable happened to me and my whole view on astrology changed. Whether you're a skeptic or a believer, give me a few minutes because I think your ideas are about to change too.

Just a Skyline drive on the iHeartRadio app, Apple Podcast, or wherever you get your podcasts. Attention Bachelor Nation, he's back. The host of some of America's most dramatic TV moments returns with the most dramatic podcast ever with Chris Harrison. During two decades in reality TV, Chris saw it all, and now he's telling all. It's going to be difficult at times, it'll be funny, we'll push the envelope, we have a lot to talk about. Welcome to the Most Dramatic Podcast Ever with Chris Harrison on the iHeartRadio app,

Apple Podcasts, or wherever you get your podcasts. Welcome to Stuff You Should Know from HouseFuckWorks.com Hey and welcome to the podcast. I'm Josh Clark. There's Charles W. Chuckers Bryant. Jerry is over there. I almost said your last name Jerry, how weird. And today we have a fourth character in the studio with this Chuck, this is a scent. Coming together to make like a tangible human being.

So you are wearing patchouli. Not wearing. Well you have patchouli on you as a result of one of Emily's sugar scrubs, right? Yeah. Mama? Yeah. And it's loveyourmama.com? Yeah.

And Jerry is contributing to that with an enchilada. So all of them combined, I would say there's an extra person in the seat right here. What kind of person is that? Just another person. Okay. A viable living organism. One that when we leave the studio will probably become extinct. That's a good one.

Did you like that? Yeah. Interesting setup. Yeah. Probably two weeks ago. Nice. How are you doing, man? I'm good.

I've been thinking of Busta Rhymes all day. Why? Did you have a song about extinction? Yeah, an album called Extinction Level Event. Oh, yeah? Yeah. And that was in one of the songs. That sounds super 90s.

Well, it's Busta Rhymes. Yeah. It has to be 90s. But I mean, even those words, Extinction Level Event, people were worried about stuff because of like the turn of the millennium. You remember? Yeah. It was a huge hit, deep impact, and Armageddon came out on the same day basically.

And both were hits. People were just nervous. And as a result, Busta Rhymes was very popular. That's right. Although he's not anymore. He's still good though. He hasn't been doing much. No, but his body of work is still good.

Oh, sure. Yeah. Leaders in the new school. He worked with a tribe called Quest. Oh, yeah. He guested on one of my favorite songs. Yeah. What's the scenario?

Was that the one? I think so. I mean, it was definitely on that one. Yeah. But that was the one also where I think, yeah, he makes fun of people with saggy pants because it was so new. Right. Apparently Busta Rhymes wasn't down with it yet.

Yeah. It's just pretty ironic because he got hardcore into that. That was raw, raw like a Dungeon Dragon, right? Right. That was pretty awesome. It's a good song. Yeah. So, Extinction is clearly what we're talking about today and I guess we should probably

give a shout out to some of the extra reading material we picked up on. There's a woman named Elizabeth Colbert or Colbert, depending on if you watch the Colbert report, she is basically a leading expert as far as journalists go on Extinction. She wrote a book called The Sixth Extinction. It's a good article. Yeah. And she wrote an article in The New Yorker. She's a New Yorker journalist.

That was basically the predecessor to the book, you know how they do. Sure. They're like, oh, I need an extra 20 grand, so I'll just write a synopsis of the book I'm writing. Yeah. And it's a good article and we worked from that. There's another one from The New Yorker review of books called They're Taking Over about the explosion of jellyfish.

Yeah. On How Stuff Works, there's one that I wrote years back called Will We Soon Be Extinct? Yeah. And there's another How Stuff Works one that we've done an episode on called Why is Biodiversity Important? Yeah. And I found one in an I09 for animals that we thought were extinct but miraculously popped back up.

Nice. Which is always a good story. Oh, yeah. It's a heartwarming story of triumph over adversity and coming back when everybody thought you were down. Yeah. Some of them like. Basically rocky.

Hundreds of millions of years later even. Yeah. It's crazy. Like the silicon? I think that's one. Was that the big fish? Mm-hmm. Yeah.

They just caught that thing one day and said, hey, wait a minute. Yeah. This thing's extinct. It's supposed to be. Exactly. Let's talk about how and why things fall off, but things do fall off and it seems that there is a, that the whole thing is a very natural process, extinction is. But for a very long time, I guess scientists believed that the God created all of the animals.

Yeah. And that his will was too perfect, his creation was too divine to even allow for extinction. So because they were aware of the fossil record, they rationalized these huge bones of animals they didn't see anywhere as we just haven't found them yet. Well, yeah. And this was all the way up into the 19th century and some really smart people like Thomas Jefferson thought, for instance, when he sent Lewis and Clark out west that they might come across the great mastodon.

Right. It's found to be out there somewhere, guys, so be careful. But there were some other smarter people like George Cuvier in 1812, he was pretty ahead of his time. In fact, in 1812, he was way ahead of his time because he published an essay called Revolutions on the Surface of the Globe and he asserted that now things can go extinct and he called them a species produced lost species. And basically hypothesized that there have been cataclysmic events that have caused

extinctions. Right. In so many words. This is basically flew in the face of this that like not only was there extinction, but there were huge events that caused it. And so the religious thinkers of the day said, okay, wait, wait, wait, we can work with this because buddy, what you're talking about is like Noah's flood. So you, my friend, just proved the Bible correct using science.

Yeah, Darwin wasn't on board though, although he did believe in extinction. He thought it was the only way it could happen is the gradual extinction. Right. It is also true. And we'll talk about that as well. And of course, Darwin is this huge hero of biology. Yeah. So everybody said, well, Darwin's right about just about everything.

So literally until the 1990s, Darwin's view that extinction happens extremely slowly. Yeah. It's more than speciation events, so ultimately you should always have more species, new species coming up than you have going extinct. Yeah. Until the 1990s. That's the way that it was, that's the way it seemed. Yeah.

So Chuck, like I said, all of this stayed around until 1991. Yeah. And it was a result of like, think about it. Think about how you think of mass extinctions now. You think of an asteroid hitting earth, destroying everything. And it wasn't until 1991 that that view became widely accepted. And it was because of this dude named Alvarez. He was a geologist, I believe, Walter Alvarez.

And in the 70s, he started studying this clay layer that was basically in the fossil record right at the time the dinosaur suddenly died out. Right. And no one could quite explain what was going on here. They just knew that this must have happened gradually. So it must be a problem with the actual fossil record, not our way of thinking. Yeah. And there are plenty of problems with the fossil record, which we'll get into as well.

Right. But Walter Alvarez said, let me look at this in a little more detail. And he looked at the iridium and found that the iridium levels were off the charts, which shouldn't be because it's very, very rare. And we associate iridium on earth as being brought here by, say, like an asteroid or whatever. Yeah. It's super abundant in asteroids.

So all of a sudden this guy goes, oh, wait a minute. Actually, we can explain this dying out of dinosaurs where the dinosaurs went 65 million years ago by an asteroid. And that was in 1980 that they proposed this hypothesis and they ran into a lot of resistance. Sure. And then finally, in 1991, a year after a crater was discovered under the Yucatan Peninsula in Mexico, they dated it and said, yeah, it just so happens that this crater was formed just at the moment the dinosaurs died out.

So the Alvarez hypothesis is probably right. And extinction can happen on a mass, sudden scale, just as it can also happen on a very long-term scale, too. Yeah. That crater was 112 miles wide, so it fit the profile. And basically ended the Cretaceous period in the Mesozoic era. And for a while, they called it the Cretaceous tertiary event, but now they call it the Cretaceous Paleogene event.

Right. And did you notice that the... Or K-P-G. Right. They noticed the... Did you notice the Cretaceous, which is spelled with a C, is denoted with a K? Yeah, I did. Did you see why?

It's just German. It's just a German translation for it. I figured it was something like that. Yeah. It was just bugging me. So now we now believe an asteroid brought us into the Cenozoic era that we've enjoyed today. Love the Cenozoic.

It's pretty awesome. It's a good era. I mean, it's our era. So you've got to love it. You've got to love it. So Chuck, like I said, the extinction can happen, and it does happen, and it's a natural process. If you talk to people about extinction today, though, they say, yeah, we're kind of in a

huge extinction event. Yeah, and it makes sense. I mean, when you look at our past, they estimate maybe up to five billion species have lived on Earth, and more than 99% of those are gone. And I love how the New Yorker put it. I think that there's an old joke that all of life on Earth today could be accounted for with a simple rounding error. Yeah.

Like everything we know. So yeah, we've lost 99% of things that have ever lived on this planet due to extinction. Right. Which, again, is like it has such a terrible connotation these days, extinction, extinction. But it happens naturally, apparently what they've found from looking at the fossil record and from studying life on Earth is that a species tends to have about a 10 million year lifespan. And a speciation event occurs where it branches off from one species and produces an entirely

new species, and that species, on average, will stick around for about 10 million years, and then something happens and it dies out, and other species take its place. This is the natural course of life from what we can tell. The thing is, it normally happens on a very slow timescale, like when it's what's called background extinction, right? Yeah. The background rate is supposed to be between one and five species per year, but they think that now it could be like a hundred times that.

I've seen up to a thousand times the normal rate. And I saw another study from 2014, so it's fresh. And it said that these researchers calculated the normal rates, and they found that there's between 0.023 and 0.135 extinct species per million species per year. It doesn't really mean much. It means so much that it boggles the mind. You know? That's a really strange way of putting it, but basically they're saying like for every

million species on Earth at any given point in time during a year, as low as 0.023 species will die out. So in a year, you shouldn't necessarily have that many species. In current times though, like you said, between a hundred and a thousand times that rate is what we're seeing right now, which is, you could say alarming. It is alarming. The reason they don't have hard numbers on this stuff is because, like we said, it's a tough thing to study because the fossil record is, well, there's a lot of problems.

One is it's incomplete. We don't really know how many species there have been on Earth since the beginning of Earth. It's just impossible to tell. Fossils form under, you know, really specific conditions, so you may think something is gone because it has disappeared from the fossil record, but all that means is there wasn't a fossil. It doesn't necessarily mean it's gone.

So that's why things will pop back up, that they'll think, hey, we haven't seen a fossil of this guy in 2,000 years, but here it is all of a sudden. And even if it has gone extinct, just where it stopped showing up in the fossil record doesn't mean, like you said, that's when it went extinct right then. It could have been millions of years later. Well, because then you're supposing that the last thing of that species happened to make a fossil, which is just silly. And also, it makes you wonder how many species have lived and died on Earth that just never

showed up in the fossil record. Yeah, just weren't fossils at all. Right. Yeah. Well, if it never crawled into amber or, you know, was buried by ash or something, that's luck. Or got trapped in brontosaurus poop. I don't know if that's good luck or bad luck.

It's just, it is what it is. It's nature. So because of all these gaps in the fossil record, these researchers that love this topic tend to do a lot of math and a lot of speculating with algorithms and mathematical formulas. They love those. To figure this stuff out. Sure. And that's the only way to do it, really, is to speculate with numbers.

It also helps them define things like the minimum viable population, which if you go below that, then it's bad news for the species. It's the minimum amount you can have to still be considered to have a bright future as a thing. Right. As a species. Right. Yeah.

That's what I mean. Yeah. A dim future if you're not surviving. Yeah. Math is pretty grim. It can be. In this case, for sure. So we'll talk about exactly what makes an extinction and then what makes up mass extinctions.

But first, let's do a little breakage, huh? I'm Mangesha Tickler and to be honest, I don't believe in astrology, but from the moment I was born, it's been a part of my life. In India, it's like smoking. You might not smoke, but you're going to get secondhand astrology. And lately, I've been wondering if the universe has been trying to tell me to stop running and pay attention, because maybe there is magic in the stars if you're willing to look for it.

So I rounded up some friends and we dove in and let me tell you, it got weird fast. Tantric curses, Major League Baseball teams, canceled marriages, K-pop, but just when I thought I had a handle on this sweet and curious show about astrology, my whole world came crashing down. Situation doesn't look good. There is risk to father. And my whole view on astrology, it changed. Whether you're a skeptic or a believer, I think your ideas are going to change, too.

Listen to Skyline Drive and the iHeart Radio app, Apple Podcast, or wherever you get your podcasts. In Bachelor Nation, he's back, the man who hosted some of America's most dramatic TV moments returns with a brand new Tell All podcast. The most dramatic podcast ever with Chris Harrison. It's going to be difficult at times. It'll be funny. We'll push the envelope.

But I promise you this, we have a lot to talk about. For two decades, Chris Harrison saw it all. And now he's sharing the things he can't unsee. I'm looking forward to getting this off my shoulders and repairing this, moving forward and letting everybody hear from me. What does Chris Harrison have to say now? You're going to want to find out. I have not spoken publicly for two years about this, and I have a lot of thoughts.

I think about this every day. Truly, every day of my life, I think about this and what I want to say. Listen to the most dramatic podcast ever with Chris Harrison on the iHeart Radio app, Animal Podcasts, or wherever you get your podcasts. Okay, so Chuck, you've been talking about animal species going extinct and then showing up again like the sealic ant. Yeah, or at least disappearing from the record. But we as humans assume they were extinct.

Like again, the sealic ant, there's this fish that they caught off the coast of South Africa. When did we talk about it? Was it in this day in history? I don't remember, we definitely have hit on that though. I think it was. Because it's huge, right? Yeah, it's a big, ugly fish. And it looks like an old dinosaur, but they thought it had died out like 50, 60 million

years ago. Actually, way longer. They thought it disappeared 400 million years ago. Even more impressive. Yeah. So then they caught one off the coast of South Africa in the 30s, then they caught another one a couple decades later in Madagascar or Mauritius or something. That made the sealic ant a Lazarus species, even though it hadn't really gone anywhere.

We just thought it did. So, we humans having the most important perspective on the entire planet, possibly in the entire universe, it was a Lazarus species to us. Yeah, Lazarus from the Bible, raised from the dead. Like the sealic ant. Again, with the biblical connotations with extinction, there's a lot at stake here. That's true. Another way something might disappear and you might think it's gone is if it actually evolves

into a new species. That's called pseudo extinction. And that's a great success story as well. It is, but it also, I don't understand why that's not just a speciation event. I mean, why is that pseudo extinction? Why is that any different from regular extinction? Yeah, maybe just because it didn't die out, it actually just changed and evolved. Those are two different things.

Yeah, it seems like a gray area to me. But for the most part, when an animal just disappears, and we should say like even today, we're still finding things that we thought were extinct, the so-called Lazarus species, which goes to make the point, we have no idea how many living species there are on the planet today. Yeah, or have been. It's all just a good guess. It is.

Using math. Yeah. Yeah. But for the most part, we understand that when a species goes away suddenly, it went extinct. And as we've been saying again and again, extinction is kind of this natural processor. It is a very natural process. And it typically results from a change in the habitat of a species and its inability to adapt.

So it dies out. Yeah. So is there a competition with other species hunting by humans, or perhaps the environment has been tainted by humans? Humans or a new bacteria or a new virus. The thing is though is, so these big factors, habitat loss, competition with new species, hunting, and contaminants in the environment, those are the big four reasons that something goes extinct, right?

Yeah. Humans can and are responsible for all four of those. Yeah. And this is the extinction that happens over time, obviously. It's not a big asteroid hit in the planet. No. But it can happen pretty quickly, and this is a Tracy Wilson joint. And in the introduction, she mentions the Stellar Seacow, which was an Arctic resident.

It was a big old manatee, basically. And they were first described by Arctic explorers in 1741. By 1768, they were extinct. So it can happen on a pretty rapid scale, especially when you introduce humans. Yeah. And it has a domino effect too, because we talked about, and everyone knows about the dangers of losing bees, it's not just like, oh, well, there are no more bees. That's going to affect pollination, and plants, and those plants are being fed on by other

animals. And it tends to have a snowball effect. Like for example, at the end of the last Ice Age, mammals, small mammals, started to go extinct. And because of that, large animals started to go extinct because they like to eat the small animals. Exactly, which is the answer to the question, why is biodiversity important? Well, because ecosystems thrive and survive on a wide number of species that exist pretty

much naturally in balance. You know, a pretty good example of that stuff falling out of balance is the passenger pigeon. You familiar? Yeah, they're trying to de-extinct that thing. Yeah, you want to talk about de-extinction? Yeah. Well, de-extinction is exactly what it sounds like. It is sort of Jurassic Parky.

It is, in 2003, some scientists revived the Bercardo, Bucardo, and that's a Spanish mountain goat, and they did it just sort of like Jurassic Park from DNA that was frozen in time. Unfortunately, although it did work initially, the DNA only survived a matter of minutes. But they did, it did count as a de-extinction. I think there was a live birth that survived a few minutes, wasn't it? Yeah, the animal itself only survived a few minutes, though. Right.

It was like, I should not be. That's true. They basically said it's happening now, and we have the capabilities, and we may not be able to bring the woolly mammoth back, but we might be able to bring back something kind of close. Right. That raises in this article that you sent this moral question, like, should we be doing this?

Just because we can, does that mean we should? If you bring back an animal that has been extinct for so long, that its habitat is now gone. So they're going to live. Exactly. Where are you going to put it? A zoo? That doesn't seem like a good reason to bring an animal back so we could put it in a zoo.

Yeah, and just like, maybe this is my opinion here, which we don't do a lot of, but it seems like concentrating on the problems we face now with the extinction rates is something that we should concentrate on, not bringing back the woolly mammoth. Right. And that also kind of dovetails with the point that if we have this ability and routinely exercise it, we may be less inclined to protect the stuff we have now for like, well, if it's important enough, we'll just genetically re-engineer it and bring it back later. Yeah, I think they, in the CNN article, they liken it to just thinking we have an undo

button on the world. Control Z. Yeah, no good. No. And it's funny because the author doesn't realize that Control Z works outside of Microsoft Word too. I don't know. I don't know. He specifically mentioned Control Z in Microsoft Word.

Oh, Word specifically? Microsoft Word. He said it. Yeah, that's a little weird. He could be a shill and he was just working it in, you know. Well on Macs though, it's not Control. Maybe he dismissed Microsoft and awkwardly put in Word. Maybe.

Or maybe that's the only program he knows. Maybe, you know. How do I work this? So you're saying that they're trying to bring back the passenger pigeon, right? Yeah. So the passenger pigeon is this really neat example of what happens when you have a lack of biodiversity. There were when European settlers came to the New World, apparently like one out of

every four birds in North America was a passenger pigeon. A quarter of the entire bird population was passenger pigeons. That's a lot of pigeons. That is a ton of pigeons. There are so many that you could just like shoot into like a flock and you would kill a couple hundred. Literally there were that many. The thing is, if you read 1493 or 1491, I can't remember which one it is, but both

are excellent books by Charles C. Mann. He talks about the passenger pigeon and how they've recently realized that there were so many passenger pigeons because a century before one of their great predators, the Native American, had been wiped out by disease that had been introduced to the continent about a century before that. So by the time the Europeans got here and really started to settle and encounter the passenger pigeon, they're like, God, look at all these pigeons and didn't realize that the pigeon population had exploded because their natural predator had died off.

And so we, in turn, hunted them into extinction. So because of one near extinction, another species was allowed to thrive and explode, and then when they were faced with their predator again, humans, they were eventually wiped out and went extinct. Yeah. The American buffalo, we almost hunted them out of existence. Yeah. We're not for Ted Turner.

Yeah. We tried our best to. They were just shooting those things for fun at one point. Man, that's disgusting. It is disgusting. It's just about the trains just going through the West and just shooting out the windows at the buffalo for no reason. Yeah.

And doing nothing, just leaving them there to rot. Unbelievable. Remember, we did an episode on the buffalo. That was a good one. So sad. No, it was good. Well, it was sad, too, though. So if you want to talk about extinction-level events, that's a whole different deal.

You want to talk plus the rot. That's not a slow, gradual extinction. That is some big thing that happens that wipes out a lot of living things all at once, and they estimate there's been more than 20 of these in the history of the world, but five of them, they call them the big five for a reason. For good reason. And we'll just go through those kind of quickly now. The Ordo Viscian extinction, it's about 490 million years ago, and that wiped out about

half of all animal families. The reason it wiped out about half was because at the time most of the stuff on Earth still lived in the sea, glaciers formed at this time, lowering sea levels, which meant that animals that lived in a certain depth of the sea usually toward the surface lost their habitat. Boiled. Yeah. Maybe.

Yeah. Or were brought down to the level where their predators like to hang out and were eaten on mass. But that accounted for that extinction, which is kind of rare, because as you'll see when we're talking about the big five or mass extinctions in general, it's very difficult to pinpoint exactly what happened. So that's one of the rare ones that we're like pretty sure this is why all of these, all this life went extinct all of a sudden.

Yeah. And one reason it's difficult is because it was almost 500 million years ago. That's another reason. It's kind of tough here in 2014. Number two, I feel like Letterman. Number two on the top five extinction, the late Devonian extinction, they're still debating about that and about a quarter of the marine families. And by the way, we should mention when they research these things, they home in on family

and genera in the big classification group. Right. They don't say like, oh, look at these kingdoms that have disappeared or these phylum. They go down to the smaller levels. Right. And family and genus are just above species as far as the taxonomy is concerned. Exactly. So what I say about half of the marine genera and that was 360 million years ago.

Right. No idea what caused that one. No idea. At least you and I have no idea. Yeah. I don't think they care about that one too much. The Permian Triassic extinction, this is a pretty big one. It's the biggest one ever.

This is the one they call the Great Dying, right? I think so. I've seen estimates of as much as 95 to 96% of all life. That's crazy. It's off during this extinction event. In this article it says 85% of marine genera and 70% of land species went extinct. And that was 250 million years ago. There's a lot of people who have different ideas about what did it, but they think it's

possible as volcanic activity, creating acid rain. That's a big one. That possibly happened more than once. Was that the one where, I don't know. I think that was the KPG event was the one where they think, they're not exactly how it happened, but they might have been just broiled. And then awesome. Broiled on the face of the earth.

Which would have happened pretty quickly too, actually. And I think that one is if, because they think it may have burst through the atmosphere, right? Yeah. It just rained hot debris everywhere. That's the one that got rid of the dinosaurs 65 million years ago. What is it called? The K-mpg?

Yeah. The Cretaceous Paleogene event now. And that's the one where they are pretty sure that an asteroid hit Central America. And sent all of this rock, like basically vaporized rock, away from earth with so much force that this stuff made it out of the atmosphere and then started to come back down. And as it did, it generated thermal heat enough to bring the broil down on earth. Yeah, and that's the one of two sub explanations. The other is that the old familiar ash basically kept photosynthesis from it, like it blacked

out the sun. Yeah, like a nuclear winner. Yeah. Yeah. Pretty nuts though. But we skipped number four. Yeah. For no good reason.

The end triassic extinction killed about 20% of marine families, about half of marine genera, and that was 200 million years ago. Yeah. But again, like with a mass extinction, there's no real definition for it, I found. I was looking to see, okay, who's the body that says like, okay, a mass extinction event took place? It's, again, the fossil record is incomplete enough and we're making guesses and mathematical guesses, but still guesses to the extent that we don't have a real definition for what constitutes

a mass extinction. With those five were so massive that there's virtually no debate whatsoever that those account for mass extinction events. Yeah. It's kind of like you know it when you see it kind of thing, but there's no agreement on how fast, pretty much, there's no agreement on how fast it has to happen or how widespread it has to happen, but typically it's like a large percentage of all of the animals alive. Something like 20% say of all living animal species, not just animals, animal species

just die off and it's worldwide that seems to be another factor in defining a mass extinction event. Yeah, like how widespread. Yeah. Sure. So these events were pretty big. Yeah. And one of the, I think one of the researchers in the article you sent made a pretty good

point that the current mass extinction that we're in now, which we're going to talk about in depth here in a minute, he said, these are way more dangerous because in the event of an asteroid, let's say, while it might really suck, it's one bad event and right afterward the world starts to try and recoup. It may take a million years, but it tries its best to start reforming life and get going again. Right. Where in now there's no stress relief.

It's just a constant. There's no recuperation because it's not over. Right. So the recuperation will come, but we won't be around to see it because the breaking point will be us wiping ourselves out by wiping out the biodiversity. And there is a kind of this whole moralistic thing to the idea of extinction. There's this whole human guilt, but if you just kind of take a step back and look at mass extinction intellectually, it doesn't wipe out life.

It just changes everything. Right. So for one species, it might be a boom time. For everybody else, it's a dying off time, but it's all in your perspective. Well, yeah. This beautiful earth that we know and love now isn't anything like it was 100 million years ago. Exactly.

And there's not necessarily a set level or a baseline that earth is supposed to be at. Right. Because nature doesn't care. Right. And nature's not like, oh, we got all these people here now and things seem pretty modern and they got smart phones. So maybe we should just protect this version. Yeah.

They're like, what was the cycle every what, 10 million years? For a species. For a species. Okay. That's a lifespan of a species on average. So basically every, what, 10,000? 10 million. 10 million years, the earth just doesn't care.

No. The point is, is for a species, its lifespan is 10 million years and the earth is not caring every day of that. Yeah. It doesn't care. It's just stumbling toward the next event basically. Exactly. That will one day probably happen.

The thing is, is all of this is not to say that humans are off the hook. All evidence that's coming in now is showing that we are doing a lot to speed up extinction events and create a mass extinction. So much so that the big five is possibly the big six and we may be in the very beginning stages of the sixth one and we'll talk about that right after this. I'm Mangesh Atikular and to be honest, I don't believe in astrology, but from the moment I was born, it's been a part of my life. In India, it's like smoking.

You might not smoke, but you're going to get secondhand astrology. And lately, I've been wondering if the universe has been trying to tell me to stop running and pay attention because maybe there is magic in the stars if you're willing to look for it. So I rounded up some friends and we dove in and let me tell you, it got weird fast. Tantric curses, Major League Baseball teams, canceled marriages, K-pop. But just when I thought I had a handle on this sweet and curious show about astrology, my whole world came crashing down.

It doesn't look good, there is a risk to father. And my whole view on astrology, it changed. Whether you're a skeptic or a believer, I think your ideas are going to change too. Listen to Skyline Drive and the iHeart Radio app, Apple Podcast, or wherever you get your podcasts. Attention Bachelor Nation. He's back. The man who hosted some of America's most dramatic TV moments returns with a brand new

Tell All podcast, the most dramatic podcast ever with Chris Harrison. It's going to be difficult at times, it'll be funny, we'll push the envelope, but I promise you this, we have a lot to talk about. For two decades, Chris Harrison saw it all and now he's sharing the things he can't unsee. I'm looking forward to getting this off my shoulders and repairing this, moving forward and letting everybody hear from me. What does Chris Harrison have to say now?

You're going to want to find out. I have not spoken publicly for two years about this and I have a lot of thoughts. I think about this every day. Truly, every day of my life, I think about this and what I want to say. Listen to the most dramatic podcast ever with Chris Harrison on the iHeart Radio app, Apple Podcasts, or wherever you get your podcasts. So Chuckers, we've been talking about mass extinction events. There's a big five and a lot of people are saying, no, there's six and the sixth one

is human caused. So much so that geologists are proposing that we call our current epoch the Anthropocene because humans are having such an impact on Earth that they imagine 10,000 years from now, geologists will be able to look and point to this layer and say, here's where humans started. Yeah, let's get in the way back machine. Oh, yeah. Let's crank this baby up.

Does it have enough kerosene? Oh, it's got enough kerosene, buddy, because we're going back about 50,000 years. You got enough? Okay. I'm going to bring a spear. And we're going to go to Australia even because it's just nice down there. And what I see around me are these huge wombat-like things that are as big as hippos. Huge.

And I see a tortoise over there that's the size of a VW beetle. And this weird short-faced kangaroo and he's 10 feet tall. 10 foot tall kangaroo, look at the size of that thing. And everything is crazy, but let's just unpack here and let's start propagating you and me. Okay. I'm going to make a spear just for safety. All right. And it sounds like I need to defend you off too.

And you know what? It's weird. Things are starting to disappear around us as we grow and as we expand. And scene can we get out of here because that 10 foot tall kangaroo's eyeing us? Well not anymore, but he's dead because they believe a lot of people think that around 50,000 years ago when humans started expanding their footprint, there was a very inconvenient correlation with species dying out as we spread about the earth. Yeah.

This sixth mass extinction, I apologize for not being able to say sixth correctly. No, it's just right. But there's a huge debate and it's still, it's not settled. Both sides are like war right. Another one is like war right. The thing is both sides agree like yeah, we're in the midst of a sixth mass extinction. And isn't that what matters? But is it human cause or is the result of climate change?

And just because it's the result of climate change doesn't mean that if you take the trail back far enough, it isn't necessarily human cause. But these are the two debates. So one is the theory of overkill, which is the one you were just describing. Yeah. And that was describing Australia 50,000 years ago. If we want to get back in the way of that machine and go to North America 11,000 years ago, three quarters of our largest animals started to die out like the mastodon and the

woolly mammoth and the giant beaver, saber-toothed tiger and not coincidentally probably that's right around the time where we first walked over the Bering Land Bridge and set up shop here in North America. Yeah. The thing is, is you can also say, well, that kind of gives or takes a few thousand years and yeah, you can, that's definitely stretchable, but it's just not been proven. So there is a huge correlation between the spread of humans and the death of what are called megafauna, huge land animals.

And they say that theory of overkill says that we came along with our smart little tool kits, which included like spearheads and arrows and axes and clubs and domesticated dogs after a certain point in time. And overhunted either these huge, like hippo-sized marsupials or we hunted things that were slightly smaller that the huge hippo-sized marsupials ate, either way, we contributed directly to their mass extinction. Yeah. And they think generally that overhunting isn't, at the very least it's not the sole

cause because you probably just can't hunt enough the amount of people that we had, especially in a place like Australia, which wasn't super heavily founded, it wasn't like 10 million people moved to Australia overnight. Right. So they say overhunting is probably not the sole cause, but maybe a factor. But other things humans did, like maybe in Australia they started burning shrubs to clear land and maybe those shrubs were eaten by a certain species and then that caused that domino effect again.

The other camp that basically says no, it's climate change and it's fairly natural. Other people might say it's human-caused climate change, but for the most part, if you are a climate change extinction proponent, you'd probably just believe that this is a natural process that the earth is undergoing and humans didn't have enough of an impact early on to account for the loss of a lot of these species. Yeah. So this study pointed to a place called Sahul, which was Australia, New Guinea and Tasmania all joined together in this mega continent.

That was a crazy place. It was. Several tens of thousands of years ago and they're saying that by the time humans arrived in Sahul or Australia, most of the megafauna was already gone. It was gone as a result of climate change and there's no evidence that we had a tool capable of killing these animals at this time. Yeah, true. So the debate still rages on.

Yeah. And there's been several ice ages that didn't make things go extinct. So people point to that as maybe another counter argument. But the researchers you sent along did this pretty cool thing. They did the first global analysis of mapping large animals during this period 132,000 to a thousand years ago and it was the first time they were able to really get a fine point on this geographical variation and species loss. They did find that 177 species of large mammals disappeared during that period where we were

starting to spread out as a species. Which apparently is as it's put in this article, a massive loss. Yeah. And they said they expect these kind of things to happen on an island like if you go to Hawaii or any island, they say that survival is the exception when humans invade an island. Exactly. But to happen on a continent, it's pretty amazing to think about the human impact. Still an island?

Well, yeah, I guess that's a good point. But the jury is still out though on exactly what's causing this. Most scientists agree that we are in a mass extinction event and it's happening pretty quickly. Something like I think a third of all coral reefs are in danger of extinction, a third of amphibians I believe. Yeah, and a quarter of all mammals and an eighth of all birds are all classified as threatened with extinction.

And this is happening around the world so it's fitting the criteria for a mass extinction. Yeah, they're basically chalking up to the pace of human expansion and if you consider that farming and logging and building roads and buildings and most of the world's water ways have been diverted or dammed at this point or manipulated somehow, only 2% of rivers in the United States run unimpeded, 2%. Everything else has been altered in some way. Chemical plants affecting CO2 in the atmosphere, it's having an effect. And that CO2 actually in the atmosphere is having another effect called ocean acidification

which has been described as global warming's evil twin. As more and more CO2 gets released in the atmosphere, the oceans scramble to keep up by absorbing more and more and it stores some of that by turning some of it into acid which lowers the pH of the ocean which is making the ocean unfit for a lot of life. But as to kind of demonstrate how mass extinction's bad for one species, great for another, jelly fish populations are booming. Oh really? So probably-

Because they like to lower pH? Yeah. They like it more acidic and they're like seriously starting to cause some real problems and we're just seeing the beginning of this. So it's entirely possible that the next thousand years we'll see the rise of the jelly fish as the rest of the life on Earth starts to die off. Well here's a staggering stat, the drop in ocean pH levels that have occurred in the past 50 years they think might exceed what has happened in the past previous 50 million

years. Wow. So in the past 50 years they've changed the, basically changed the chemical makeup of the ocean more than the past 50 million. And speaking of 50 years, apparently in the next 50 years an estimated half, half of all species on Earth could be extinct. Sucks man, I want to see a sloth as big as an elephant. Hey, get into de-extinction.

Well here- You just saw one, we were in, we were in Sahul. Well yeah, it was nice. But I wanted to come in the way back machine and bring it to Atlanta. No, I don't think that's a good idea man. That thing looked like it would go berserk. And finally, unless you have anything else. I don't think so, I'm looking at everything.

We have a few highlights of extinct animals that have been rediscovered, which is not the same thing as being re-engineered. What was this in Io9? Yeah, this is Io9 and some of those are pretty good. The Bermuda Petrel disappeared, they fought in the 1600s, but rediscovered in 1951. There's about 180 of those alive today. Let me see here, what else is good? Well we also, we already talked about the Silacanth.

The Cuban Solinodon, discovered in 1861 has only been caught 37 times in the history of the world. In 1970 they thought it was extinct, it's like a weird rat-like species. But then they found one in the 70s and then another one in 2003. So like welcome back, Cuban Solinodon. So it was like caught during the 70s and then during the period of the 70s revival in the early 2000s. That's right.

Nice. Gilbert's Pohturu, man these have weird names. That's why they went extinct. Because you couldn't say sloth. We should save the, what, Pohturu. In 1841 this is a rabbit-sized marsupial in Australia and it last appeared in 1879 and they thought, well this thing's gone. Up until 1994 it came back out and poked its head around and got caught in a few traps.

But apparently less than a hundred of those in the world. So those are just a few of the ten and there's more than ten, obviously, but it's always a good story. Sure it is. Heartwarming. We think this thing's dead. It's like, yeah, welcome back to the mass extinction, still going on. If you want to know more about extinction you should read each and every one of the articles

we cited and you can also read this article on HowStuffWorks.com by typing extinction in the handy search bar and since I said that it's time for a listener mail. I'm going to call this police interrogation follow-up from Matt Pope, A. in Victoria, British Columbia. Thank you to Vancouver by the way for two great shows after our great shows in Toronto. Yep. Thanks to Toronto and Vancouver. Very supportive people and boy that second crowd man, Cooper, was drunk and rowdy.

Yeah. Hey guys, just listened to police interrogation and I thought I'd share a couple of quick personal stories to illustrate the pitfalls of relying on nonverbal cues to see if someone's guilty. I've never been in trouble with the law myself but several years ago I witnessed a crime, called 911 to report it, cops nabbed the perpetrator and a few days later asked me to come down to provide a witness statement. When I arrived an officer led me into a tiny room that was every bit as bleak as the ones

you see on TV. It was a weird experience even though I wasn't accused of a crime and the cop was polite in his questioning, the interrogation room setting and the power differential between the uniform cop with a gun and my unarmed self made me feel really nervous. I started sweating, my voice shook and if you'd been watching my body language did one way mirror you'd have thought I was guilty. Wow. He was just a witness.

Yeah. The second story is very similar. Every year our local courthouse has a public event where they give tours and put on a mock trial and actually hang someone, kidding, I made up that part. That was pretty good too. It's supposed to be educational and fun. My father is a lawyer and one year asked me, I'd like to play the defendant in the trial. I'm no actor but I said, sure, my character was accused of a minor drug offense and I

went through the whole ordeal being on trial and testifying my own defense. I'll spare you the details but afterward my mom said, wow, you looked really guilty up there. I hope you never actually are on trial for anything because they'll lock you up and throw away the key. I learned from these situations the very act of treating someone like a criminal and make him appear guilty. Yeah.

It reminds me of the Stanford Prison study that we've talked about. And there's a psychology is nuts about that, psychology is nuts video on our YouTube channel about the Stanford Prison experiment. Yeah, that's a good one. You should check that out. I hope you guys never have to find out the hard way you'll react to police interrogation if you do. I hope you find a good lawyer.

That's from Matt Pope once again in Victoria, BC. Well, thanks a lot, Matt. That's kooky about your town doing mock trials and stuff like that. Yeah, and like hanging a guy? Yeah. Crazy. He said it's fun. The only thing that's okay about it is they make the guy look like Hitler.

Right. So it's like hanging Hitler every year, which everybody can get behind. Yeah, they call it the Hitler hang. If you want to send us an email that Chuck feels the need to make up stuff about, you can, well, you can send us an email, you can also tweet to us at syskpodcast. You can join us on facebook.com slash stuff you should know. You can send us an email to stuffpodcast at howstuffworks.com, and as always, check out our home on the web, stuffyoushouldknow.com.

For more on this and thousands of other topics, visit howstuffworks.com. I'm Munga Chauticular, and it turns out astrology is way more widespread than any of us want to believe. You can find it in Major League Baseball, international banks, K-pop groups, even the White House. But just when I thought I had a handle on this subject, something completely unbelievable happened to me. And my whole view on astrology changed.

Whether you're a skeptic or a believer, give me a few minutes, because I think your ideas are about to change too. Listen to Skyline Drive on the iHeart Radio app, Apple Podcast, or wherever you get your podcasts. Attention Bachelor Nation, he's back, the host of some of America's most dramatic TV moments returns with the most dramatic podcast ever with Chris Harrison. During two decades in reality TV, Chris saw it all. And now he's telling all.

It's going to be difficult at times. It'll be funny. We'll push the envelope. We have a lot to talk about. Listen to the most dramatic podcast ever with Chris Harrison on the iHeart Radio app, Apple Podcasts, or wherever you get your podcasts.