Selects: How Extinction Works | STUFF YOU SHOULD KNOW

Hello friends, it's Josh and I'm back. with the select. And this week I've. selected our 2014 episode on extinction. In this episode, we go over all the big. extinctions [music] and what probably. caused them, including the one we're. most likely in right now, which was. probably caused by humans. And if you. pay attention, you can start to notice a. little glimmers, a little beginnings of. what would become my side podcast, The. End of the World, with Josh Clark. And. although we don't talk about any movies,

I'm betting there's some glimmers of. Chuck's longrunning side podcast, Movie. Crush, in here, too. Hope you enjoy this. episode. It's a good one. [music]. Welcome to Stuff You Should Know, a. production of iHeart [music] Radio. >> Hey, and welcome to the podcast. I'm. Josh Clark. There's Charles W. Chucker's. Bryant. Jerry is over there. I almost.

said your last name, Jerry. How weird. And then today we have a fourth. character in [music] the um in the. studio with his Chuck. This a scent. >> Yeah. >> Scent. coming together to make like a tangible. human being. So you are wearing pichuli. >> Uh not wearing. >> Well, you have pichuli on you as a. result of one of Emily's sugar scrubs, right? From. >> Mama. >> Yeah. And it's loveyoumama.com. >> Yeah. >> Okay. And then Jerry uh is contributing.

to that with um an enchilada. So the all of them combined. I would say. there's like there's an extra person in. this seat right here. >> Uh 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. I've had that plan since probably. two weeks ago.

>> Nice. >> Uh, how you doing, man? >> I'm good. I've been thinking of Buster. Rhymes all day. >> Why did he have a song about Extinction? >> He had an album called Extinction Level. Event. >> Oh, yeah. >> Yeah. And that was in one of the songs. >> That sounds super 90s. >> Well, it's Buster Rhymes. 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. >> XFiles is a huge hit. >> Sure. >> Deep Impact and Armageddon Oh yeah.

>> came out at like on the same day. basically and both were hits. >> Like people were just nervous. >> Yeah. >> And um as a result, >> Buster Rhymes was very popular. >> That's right. Although he's not anymore. >> Uh he's still good though. He hadn't. been doing much. >> No, but his body of work is still. >> Oh, sure. Yeah. Leaders of the New. School. >> And his early work with Tribe Called. Quest. >> Oh, yeah. He guested it on one of my. favorite songs.

>> Yeah. This What's the scenario? >> Was that the one? >> I think so. I mean, he was definitely on. that one. >> Yeah. >> But they That was the one also where I. think um Yeah. He makes fun of people. with saggy pants cuz it was so new, >> right? >> Apparently Buster Rhymes wasn't down. with it yet. Yeah. >> Which. >> is pretty ironic because he got hardcore. into that. >> That was uh raw raw like a dungeon. dragon. Right. >> Right. Right. >> It was pretty awesome. >> It's a good song. >> Yeah. >> So, Extinction is clearly what we're. talking about.

>> today. Uh and uh I guess we should. probably give a shout out to some of the. extra reading material. >> Yeah, man. we picked up on um there's a. woman named uh Elizabeth um Colber or Co. Colbear depending on if you watch the. Col Bear Report. >> Yeah. >> Um and she is basically. a leading expert as far as journalists. go on extinction. She wrote a book. called The Sixth Extinction. >> That's a good it's a good article. >> Yeah. [clears throat] And like they she.

wrote an article in the New Yorker. She's a New Yorker journalist. >> That was basically the predecessor to. the book. They're [clears throat]. like, "Oh, I need an extra 20 grand, so. I'll just write a synopsis of the book. I'm writing.". >> Um, and it's a good article and we work. from that. There's another one from the. New York Review of Books called They're. Taking Over about the explosion of. jellyfish. >> Yeah. >> Um, 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 uh I found one in. >> I9. >> for uh animals that we thought were. extinct but miraculously popped back up. >> Nice. >> Which is always a good story. >> Oh yeah. It's a 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 silicant. [snorts]. >> Uh I think that's one. Was that the the. big fish? Yeah.

They just caught that thing one day. >> Yeah. >> And said, "Hey, wait a minute.". >> Yeah. >> This thing's extinct. >> It's supposed to be. >> And we'll we'll talk about how and why. >> things fall off, >> but things do fall off. And it seems. that there [clears throat] is a um that. the whole thing is a a very natural. process, extinctionist. But for a very long time, I guess. scientists um believed that the.

God created all of the animals, >> yeah, >> on earth 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. Yeah. And this was all the. way up and, you know, 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 Mastadon, >> right? >> He's like, "It's bound to be out there. somewhere, guys. So, be careful." Uh, but there were some other smarter people. um like George Kovier. >> in 1812. He was pretty ahead of his. time. In fact, in 1812, he was way ahead. of his time because he uh published an. essay called Revolutions on the Surface. of the Globe. >> Yeah. >> And he kind of asserted that no, things. can go extinct. Uh and he called them uh. a species produce lost species,

>> right? >> 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 there were. huge events that caused it. And so the. 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. That. is also true and we'll talk about that. as well. >> And of course Darwin is this huge hero. of biology. So everybody's like, well, Darwin's right about just about. everything. So literally until the. 1990s, Darwin's view that extinction happens. extremely slowly. >> Yeah. >> Slower 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 um. 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 a a. asteroid hitting Earth, destroying. everything. And it wasn't until 1991.

that that view became widely accepted. And it was because of this dude um named. Alvarez. He was a geologist I believe uh. Walter Alvarez. And in the 70s he. started studying this clay layer that. was basically in the fossil record right. at the time the dinosaurs 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, um, Walter Alvarez said, "Let me let me look at this in a little. more detail." And he looked at the. aridium and found that the aridium. levels were off the charts, which. shouldn't be because it's very, very. rare. And we associate aridium 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. Maybe 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. >> Um and then finally in 1991. um a year after a crater was discovered. under the Yucatan Peninsula in Mexico. um 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 a very long-term. scale, too. >> Yeah, that crater was 112 miles wide, so. it fit the profile. [clears throat]. >> And uh basically ended the Cretaceous. period in the Mesazoic era. And for a. while they called it the Cretaceous. tertiary event, but now they call it the. Cretaceous Paleo gene event. >> And did you notice that the. >> KPG, >> right? They noticed the that Did you.

notice the C 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, I I it was just bugging me. So now. we now believe an asteroid brought us. into the cenazoic era that we that we. enjoy today. >> Love the cenazoic. >> It's pretty it's pretty awesome. >> It's a good era. >> I mean it's our era. >> Yeah. So you got to love it. >> You got to love it. >> Um so Chuck,

like I said, the extinction. extinction can happen and it does happen. and it's a natural process. Um, 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 the the our past, they. estimate maybe up to 5 billion species. have lived on Earth and more than 99% of. those are gone. And uh, 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 [laughter]. everything we know. >> Um 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.

millionyear lifespan. And there 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 time scale like when it's.

what's called background extinction, right? >> Yeah. The background rate uh 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 it said. that they these researchers calculated. the normal rates and they found that. there's between 023 and.135. extinct species per million species per.

year. >> It doesn't really mean much. >> It means so much that it boggles the. mind. >> Yeah. You know, like 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, >> uh, as low as 0023. species will die out. >> Yeah. >> So, in a year, you shouldn't necessarily. have that many species. In in current. times though, like you said, between a.

100 and a thousand times that rate is. what we're seeing right now, which is, you could say, alarming. >> It is alarming. Uh the reason they don't. have hard numbers on this stuff is. because like we said uh it's a tough. thing to study because the fossil record. is well there's a lot of problems. Uh. one is it's incomplete. We don't really. know how many fos or species there have. been on Earth since the beginning of. Earth. It's just impossible to tell. >> Um 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, >> right? >> 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 supposeding that the last thing.

of that species happened to make a. fossil. Yes. >> Which is just silly. >> Yeah. Um 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, >> Uhhuh. >> was buried by uh ash or something, >> that's luck. >> Or got trapped in Bronosaurus 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, um these. researchers that love this topic tend to. do a lot of math, >> right? >> And a lot of speculating with algorithms. and uh mathematical formulas, figure. this stuff out. >> Sure. >> And that's the only way to do it really. uh is to speculate with numbers. Um 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 uh to.

have a bright future, >> right? >> As a thing. >> or to just survive as a species, right? >> Yeah, that's what I mean. >> Yeah. >> Dim future if you're not surviving. >> Yeah. Math is pretty grim. >> It can be in this case for sure. >> Um so we'll talk about exactly what. makes an extinction and and then what. makes up mass extinctions. Um but first. let's do a little uh breakage. Huh. >> [music].

>> stuff you should know. >> Okay. So, Chuck, you've been talking. about um animals, animal species going. extinct and then showing up again like. the celacant. >> Yeah. Or at least disappearing, >> right, >> from the record. >> But we as humans assume they were. extinct. Like again the celacanth is. this fish um 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. >> cuz 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 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 uh or Maitius or. something and um that made the celacanth.

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. >> Yeah. >> It was a Lazarus species to us. >> Yeah. Lazarus from the Bible, >> right? >> Raised from the dead. >> Yeah. Yeah, >> like the cel. >> again with the biblical connotations. with extinction. >> Yeah, >> there's a lot at stake here. >> That's true. Um, 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. >> Mhm. >> 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? Um, yeah, maybe just because. it's uh it's didn't die out, it actually. just changed and evolved. >> Those are two different things. >> Yeah, it seems like a gray area to me. >> Yeah. >> But for the most part, when an animal.

just disappears, and we should say like. even today, we we're still finding. things that we thought were extinct. Yeah. Yeah. >> Soal 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. >> Grim grim math. But for the most part we. understand that when uh species goes. away suddenly it went extinct. And as.

we've been saying again and again, extinction is kind of this natural. process or it is a very natural process. Um, and it typically results from a. change in the habitat. >> Yeah. >> Of species and it's inability to adapt. So it dies out. >> Yeah. Uh competition with other species. Um hunting by humans or perhaps the. environment has been tainted uh by. humans. humans or a new bacteria or a.

new virus. The thing is though is so. these 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 the and these are this is the. extinction that happens over time. Obviously, not a big asteroid hitting. the planet. >> No, but it can happen pretty quickly. And this uh this is a Tracy Wilson joint. and in uh in the introduction she.

mentions the uh stellar sea cow which. was an Arctic resident. It was a big old. manatee basically. >> Yeah. >> And they were first described by Arctic. explorers in 1741. By 1768 they were extinct. So it can. happen on a pretty rapid. um scale. >> Yeah. >> Especially when you introduce humans. >> Yeah. Yeah. And it, you know, it has a. domino effect, too, cuz we talked about, and everyone knows about the dangers of.

losing bees. It's not just like, oh, well, there are no more bees, right? >> That's going to affect pollination and. plants, and those plants are being fed. on by other animals. >> And, uh, it tends to have a snowball. effect. Um, like for example, at the end. of the last ice age, uh, 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.

are exist pretty much naturally in. balance. >> Yeah. >> Um, you know, a pretty good example of. that stuff falling out of balance, um, is the passenger pigeon. You familiar? >> Yeah. They're trying to [clears throat]. de-extinct that thing. >> Yeah. You want to talk about. de-extinction? >> Yeah. Well, deextinction is um exactly. what it sounds like. It is sort of. Jurassic Parky. >> It is uh in 2003, some scientists. revived the Bur uh Bicardo Bicardo, 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, uh although it did work initially, uh. the DNA only survived a matter of. minutes, but they did it did count as a. deextinction. >> I think it there was a live birth that. survived a few minutes, wasn't it? >> Yeah. The the animal itself only. survived a few minutes though, >> right? It was like I should not be.

[laughter]. >> That's true. Uh, and. I mean 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. So, and that raises in this. article that you sent um just. [clears throat] this moral question like. should we be doing this? Just because we. can does that mean we should? >> And so like if you bring back an animal. that has been extinct for so long that.

its habitat is now gone. >> Yeah. Where are they 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 uh like maybe it, this is. my opinion here, which we don't do a lot. of, but 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 and that also kind of. dubtales with the point that if we have. this ability and routinely um exercise.

it, we may be less inclined to protect. the stuff we have now. If we're 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, right, >> on the world. >> 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 I'm not sure. >> He specifically mentioned control Z and. 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. >> Maybe, [laughter]. >> you know. >> Well, on Macs though, it's not control. Um maybe he just meant Microsoft and. awkwardly put in Word. >> Maybe. >> Or maybe that's the only program he. knows. maybe, you know, >> how do I work this? [laughter] Um, so. you were saying that they're trying to. bring back the car the passenger pigeon, right? >> Yeah. >> So, the passenger pigeon is this really.

neat example of what happens when um you. have a lack of biodiversity. >> Yeah. Um [clears throat] there were when. uh 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, it was there were. that many. The thing is is um if you if. you read 1493 or 1491, I can't remember. which one it is, but both are excellent. books by Charles C. Man, he talks about. the passenger pigeon and how they've. recently realized that there were so. many passenger pigeons because a century. before their one one of their um great. predators, the Native American, yeah, had been wiped out by disease that had. been [clears throat] 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, >> right? >> And so we in turn hunted them into. extinction. So because of one near. extinction, the another species was. allowed to thrive and explode. And then. that when they were faced with their. their predator again, humans, they were.

eventually wiped out and went extinct. >> Yeah. The American buffalo. We almost. hunted them out of existence. >> Yeah. Were it not for Ted Turner? >> Yeah. We tried our best to. They were. just shooting those things for fun. Yeah. At one point. >> Man, that's disgusting. >> It is disgusting. You hear about the. like trains? >> Yeah. >> 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. Um, so. >> No, it was good. Well, it was sad, too,

though. >> Oh, gotcha. >> So, uh, if you want to talk about. extinction level events, that's a whole. different deal. >> If you want to talk buster rhymes, >> that's not a slow gradual extinction. That is uh some big thing that happens. that wipes out a lot of living things. all at once. And um they estimate. there's been more than 20 of these in. the history of the world. But um five of. them, they call them the big five, right? >> For a reason, >> for good reason. >> And uh we'll just go through those kind.

of quickly now. Uh the Ordo Vissian. extinction, it's about 490 million years. ago. And that wiped out about half of. all animal families. >> And 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 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 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. Uh. number two feel like Letterman. Number.

two on the top five extinction. Um the. late Deonian extinction. Um they're. still debating about that. [clears throat] And about a quarter of. the marine families, and by the way, we. should mention when they uh research. these things, they home in on family in. Janera in the big um uh classification. group, >> right? >> They don't say like, "Oh, look at these. kingdoms that have disappeared or these. phylm." They go down to the smaller. levels, >> right? And family and genus are just.

above species as far as the taxonomy is. concerned. >> Exactly. Um, 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 uh the Perian Triacic extinction. This is um this is a pretty big one. >> This is the biggest one ever. >> This is the one they call the great. dying, right? >> Uh I think so. >> I've seen estimates of as much as 95 to.

96% of all life. that's crazy. >> Died off during this this extinction. event. Um, 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 volcanic. activity creating acid rain. Yeah. >> Um, 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 the uh KPG event was. the one where they think um they're not. exactly how it happened, but they may. have been just broiled. >> Isn't that awesome? >> Broiled on the face of the earth. >> Yeah. Which would have happened pretty. quickly, too, actually. >> And I think that one is if uh because. they think it may have burst through the. atmosphere, right? >> Yeah. So, >> just rained hot debris everywhere. >> That's the one that got rid of the. dinosaurs. Yeah. 65 million years ago. What is it called? The K Khen PG. >> Yeah. The Cretaceous Paleo gene event.

now. And that's the one where they they. are pretty sure that an asteroid hit um. Central America. >> Yeah. >> And sent all of this rock. >> Yeah. >> like basically vaporized rock out with. away from Earth with so much force that. this stuff made it out of the. atmosphere. >> Yeah. >> 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 um sub.

explanations. The other is that uh the. old familiar um ash basically. kept photosynthesis from it like it. blacked out the sun. >> Yeah. Like a nuclear winter. >> Yeah. >> Yeah. >> Um. >> pretty nuts though. >> But we skipped number four. >> Yeah. >> For no good reason. Um the end triacic. extinction killed about 20% of marine. families and about half of marine. genera. And that was 200 million years. ago. >> Yeah. And again, like with a mass. extinction, there's there's no real.

definition for it. I found I was looking. to see, okay, who's who's the body that. says like, okay, a mass extinction event. took place. It's again, the the. 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. But those five were so. massive. Yeah. That there's virtually no. debate whatsoever that those account for.

mass extinction events. >> Yeah. >> Um the it's kind of like a you know it. when you see it kind of thing, but. there's no agreement on how pretty much. >> um there there's no agreement on how. fast it hap 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. Yeah. Something like 20% say of all living. animal species, not just animals. Animal. species just die off.

>> Yeah. >> Um and it's worldwide. That's another. that seems to be another um factor in. defining a mass. >> extinction. Like how widespread. >> Yeah. Sure. >> So um these events were pretty big. >> Yeah. And one of the um I think one of. the researchers in the article you sent. made a pretty good point that the. current mass extin extinction that we're. in now which we're going to talk about. in depth here in a minute. Uh 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. [clears throat] Right? >> Where in now there's no stress relief. It's just a constant there's no. recuperation because it's not over. >> Right? Or the recuperation will come but. we won't be around to see it because it. the 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 to the idea of. extinction. This there's this whole. human guilt. But if you just kind of. take a step back and look at mass. extinction, um, intellectually, it doesn't wipe out life. It just. changes. >> everything, >> right? So for [clears throat] 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 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 that or a baseline that Earth. is supposed to be at, >> right? Cuz nature doesn't care, >> right? >> And nature's not like, "Oh, we got all. these people here now and uh things seem. pretty modern and they got smartphones, so maybe we should just protect this. version.". >> Yeah. >> Uh they're like, "What what was the. cycle? Every what? 10 million years. >> for a species.". >> For a species. Okay. >> That's the lifespan of a species on.

average. So basically every what 10,000. >> 10 million. >> 10 million years the earth it 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. stuff you should know. [music]. >> So, chuckers, we've been talking about. mass extinction events. There's 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 uh geologists. are proposing that we call our current. epoch the anthroposine. >> Yeah. 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. Uh, let's get in the wayback. machine. >> Oh, yeah. Let's crank this baby up.

>> Does it have enough kerosene? >> Oh, it's got enough kerosene, buddy. Cuz. we're going back about 50,000 years. >> Oh, you got enough. Okay, I'm going to. bring a spare key. >> And we're going to go to Australia even. [music] um because it's just nice down. there. And what I see around me are. these huge wombatlike things that are as. big as hippos. >> Huge. >> And I see a tortoise over there that's. the size of a VW beetle. >> Yeah. >> And this weird shortfaced kangaroo. And. he's 10t tall. >> 10 foot tall kangaroo. Look at the size.

of that thing. >> And everything is crazy. But um 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 needed. to fend 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 uh and. seen. >> That was nice. Can we get out of here? Cuz that 10 foot tall kangaroo is eyeing. us.

>> Well, not anymore, buddy. He's dead. um. because they believe. >> a lot of people think that around 50,000. years ago when humans started expanding. their footprint um there was a very. inconvenient. uh correlation with species dying out as. we spread about the earth. >> Yeah. The the this sixth mass extinction. I apologize for not being able to say. sixth correctly.

>> No, that's right. But um there there's a. huge debate and it's still it's not. settled. Both sides are like ah we're. right. Right. >> The other one is like we're right. The. thing is both sides agree like yeah. we're in the midst of a six mass. extinction. >> And isn't that what matters? >> But is it human- caused 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. caused. 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 uh describing. Australia 50,000 years ago. Um, if we. want to get back in the wayback machine. and go to North America 11,000 years. ago, uh, 3/4 of our largest animals. started to die out like the mastadon and. the woolly mammoth and the giant beaver, saber-tooth tiger. And not. coincidentally, probably that's right. around the time where we first walked. over the Bearing Land Bridge and setup. 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 it there is a huge. correlation between the spread of humans. and the death of what are called. megapona, huge land animals. >> Yeah. And they say that 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.

>> Sure. >> And over hunted either these huge. like hipposized marsupials. >> Yeah. >> Or we hunted things that were slightly. smaller that the huge hipposized. marsupials ate. Either way, we. contributed directly to their mass. extinction. >> Yeah. And they think um generally that. over hunting isn't 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 uh founded, you know, it wasn't. like 10 million people moved to. Australia overnight, >> you know, right? >> So, they say over hunting is probably. not the sole cause, but maybe a factor. Um but other things humans did like. maybe um in Australia they started. burning uh shrubs to clear land and. maybe those shrubs were eaten by a. certain species and then that caused. that domino effect. Again. >> another um 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're. 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. This one study pointed to a place. called Sahul, which was uh 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 were saying that by. the time humans arrived in Sahul or. Australia, most of the megapona was. already gone. It was gone as a result of. climate change. And there's no evidence. that we had a toolkit capable of killing. these animals. um you know at this time. >> Yeah. True. >> So the debate still rages on. >> Yeah. And you know there's been several. ice ages that didn't make things go. extinct, >> right? >> So people point to that as maybe uh.

another counterargument. >> Yeah. >> Uh but the researchers you sent along. did this uh pretty cool thing. They did. the first global analysis. um of mapping large animals during this. period 132,000 to a thousand years ago. Right? And it was the first time they. were able to really get a fine point on. this geographical variation and the and. species loss. And they did find that 177. species of large mammals disappeared. during that period where we were.

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

Um the but the jury is still out though. on exactly what's causing this. Most. scientists agree that we are in an a. mass extinction event and it's happening. pretty quickly. Um. something like I think a third of all. coral reefs are in danger of extinction. Uh 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 um. >> 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 the pace of human expansion. And you. know, if you consider that uh farming. and logging and building roads and. buildings and uh most of the world's. waterways have been diverted or damned. at this point or manipulated somehow, >> right? >> Um only 2% of rivers in the United. States run unimpeded. 2%. >> Everything else has been altered in some. way. >> Chemical plants um affecting, you know,

CO2 in the atmosphere. It's having an. effect. >> and that CO2 actually in the atmosphere. is having another effect um called ocean. acidification which has been described. as global warming's evil twin as more. and more CO2 gets released in the. atmosphere. Um the oceans scramble to. keep up by absorbing more and more. Yeah. 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 is bad for one species, but great for another, jellyfish. populations are booming. >> Oh, really? >> So, probably. >> because they like the lower pH. >> Yeah. Yeah. >> They like it more acidic and they are. 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 jellyfish as. the rest of the life on Earth starts to.

die off. >> Well, here's a staggering stat. Uh the. 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 deextinction. >> Well, here um. >> you just saw when we were in we were in. Sahul. Well, yeah, it was nice, but I. wanted to like I wanted to come in the. wayback 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. >> Uh, and finally, unless you have. anything else. >> I don't think so. I'm looking at. everything. >> Um, we have a few highlights of uh.

extinct animals that have been. rediscovered, which is not the same. thing as being re-engineered. >> What was this? An IO 9 article? >> I some of those are pretty good. >> Sure. uh the Bermuda patrell and uh. disappeared they thought in the 1600s. but rediscovered in 1951. There's about. 180 of those alive today. Uh let me see. here what else is good. Well, we also we. already talked about the cilocanth. The. Cuban uh Solendon Solenodon, excuse me, discovered in 1861.

um has only been caught 37 times in the. history of the world. in in 1970 they. thought it was extinct. It's like a. weird ratlike species, but then they. found one in the 70s and then another. one in 2003. >> Huh. >> So like, welcome back Cuban Solenodon. >> So it's like caught during the '7s and. then during the period of the 70s. revival in the early 2000s. >> That's right. >> Nice. >> Uh Gilbert's pouru. Man, these have.

weird names. >> That's why they went extinct. >> because you couldn't say sloth. you know. that we we should save the uh the what? >> Yeah. >> In 1841. This is a rabbitiz uh marsupial. in Australia [clears throat]. >> and it last appeared in 1879 and they. thought well this thing's gone up until. 1994. Uh came back out and poked his. head around and got caught in a few. traps. But uh currently less than a. hundred of those in the world. >> Yeah. And. >> so those were just a few of the 10 and.

there's more than 10 obviously but um. it's always a good story. Sure it is. It's heartwarming. >> We think this thing's dead. >> It's like, yeah, welcome back to the. mass extinction. >> Yeah, exactly. >> Still going on. >> Uh, if you want to know more about. extinction, you should read each and. every one of the articles we've cited. Uh, and you can also read this article. on how stuffworks.com by typing. extinction into the handy search bar. And since I said that, it's time for. listener mail. >> I'm going to call this police. interrogation follow-up.

>> Okay. >> From Matt Pope. A in Victoria, British. Columbia. >> All right. >> Thank you to Vancouver, by the way, for. [music] two great shows. >> Yeah. >> After our great shows in Toronto. >> Yep. >> Thanks to Toronto and Vancouver. >> Very supportive people. And boy, that. second crowd in Vancouver was drunk and. rowdy. >> Yeah. [laughter]. >> Hey guys, just listened to police. interrogation. I thought I'd share a. couple of quick personal stories that. illustrate the pitfalls of relying on. non-verbal cues [music] 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. The cops snabbed 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 and is 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 had been.

watching my body language through the. one-way mirror, you would have thought I. was guilty. >> Wow. >> And he was just a witness. >> Yeah. >> Uh the second story is very similar. Uh. 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, Chuck. >> Uh it's supposed to be educational and. fun. My father is a lawyer and one year. asked me if I'd like to play the. defendant [music] 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 [music] 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 can. make him appear guilty. >> Yeah. >> 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. Uh I hope you guys um.

never have to find out the hard way. Uh. you'll react to police interrogation. If. you do, I hope you find a good lawyer. That is from Matt Pope once again in. Victoria, BC. >> Huh. Well, thanks a lot, Matt. Um that's. kooky about your town doing mock trials. and stuff like that. >> Yeah. And like hanging a guy. >> Yeah. It's crazy. >> He said it's fun. The only 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. [laughter].

>> If you want to send us an email that. Chuck feels the need to make up stuff. about, you can send us an email to. stuffodcast at iheartradio.com. [music]. >> Stuff you should know is a production of. iheartradio. For more podcasts from. [music] iHeart Radio, visit the iHeart. Radio app, Apple Podcasts, or wherever. you listen to your favorite shows. [music].