October 21, 2014 • 47 mins
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.com
See omnystudio.com/listener for privacy information.
Mark as Played
Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:00):
Welcome to you stuff you should know from house Stuff
Works dot com. Hey, and welcome to the podcast. Don't
Josh Clark, there's Charles W. Chucker's Bryant. Jerry is over there.
I'm gonna said your last name, Jerry. How weird. And
then today we have a fourth character in the in
(00:23):
the studio with this Chuck. This a scent scent coming
together to make like a changeable human being. So you
are wearing Patuli, uh not wearing well, you have Petulia
on you as a result of one of Emily's sugar
scrubs right from Mama and it's Love your Mama dot com. Okay.
(00:45):
And then Jerry is contributing to that with um an enchilada,
so that all of them combined, I would say, there's
like 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
(01:06):
studio we'll probably become extinct. That's a good one. Did
you like that? Yeah? I've had that plan since probably
two weeks ago. How are you doing, man, I'm good.
I've been thinking of Busta Rhymes all day. Why did
he have a song about extinction had an album called
the Extinction Level Event. Oh yeah, yeah, and that was
(01:29):
in one of the songs that sounds super nineties. Well
let's Buster Rhymes has. But I mean even those words
extinction level Event. People were worried about stuff because of
like the turn of the millennium. You remember, Exiles is
a huge hit Deep Impact and Armageddon came out of
like on the same day basically, and both were hits.
(01:52):
Like people were just nervous and um. As a result,
Buster Rhymes is 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 yeah, leaders in the
New School and his early work with Chip call Quest.
(02:13):
Oh yeah, he guessed it on one of my favorite
songs is What's the Scenario? Was that the one I
think so? I mean it was definitely on that one,
but they that was the one also where I think, um, yeah,
he makes fun of people with saggy pants because it
was so new. Apparently Bustter Rhames wasn't down with it yet. Yeah,
just pretty ironic because he got hardcore into that. That
(02:36):
was raw, raw, like a dungeon dragon, right, it's pretty awesome.
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 Elizabeth
(02:57):
um Colbert or Corp Colbert depending on what if you
watch the Colbert Report. 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, and like she wrote an
article in the New Yorker. She's a New Yorker journalist
(03:19):
that was basically the predecessor to the book. You know
how they do. Like, I need an extra twenty grand,
so I'll just write a synopsis of the book I'm writing.
Um And it's a good article, and we worked from that.
There's another one from the New York Review of Books
called They're taking Over about the explosion of jellyfish. UM.
On how stuff Works, there's one that I wrote years
(03:39):
back called will We Soon Be Extinct? And there's another
how stuff Works one that we've done an episode on
called wise bio Diversity Important. Yeah, and I found one
in an I O nine for animals that we thought
were extinct but miraculously pop back up nice, which is
always a good story. Oh yeah, it's a it's a
(04:01):
heartwarming story of triumph of raversity 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 when I
was at the Big Fish. They just caught that thing
one day, yeah, and said, hey, wait a minute, Yeah,
(04:24):
this thing's extinct. It's supposed to be. And we'll talk
about how and why things fall off. But things do
fall off, and it seems that there is a um
that the whole thing is a very natural process. Extinctionists.
But for a very long time, I guess scientists um
(04:46):
believed that the God created all of the animals on
Earth and that his will was too perfect, his creation
was too divine to even allow for extinct and so
because they were aware of the fossil record, they rationalized
these huge bones of animals that he didn't see anywhere
(05:06):
as we just haven't found him yet. Well yeah, and
this was all the way up and you know, into
the nineteenth 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.
He's like, it's found to be out there somewhere, guys,
to be careful. But there were some other smarter people,
(05:27):
um like George Cuvier in eighteen twelve, he was pretty
ahead of his time. In fact, in eighteen twelve he
was way ahead of his time because he published an
essay called Revolutions on the Surface of the Globe and
he kind of asserted that now things can go extinct,
and he called them a species produced lost species and
(05:51):
basically hypothesized that there have been cataclysmic events that have
caused extinctions. In so many words, this is basically flew
in the face of this that like, not only was
their 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.
(06:14):
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 well, Darwin's right about
(06:34):
just about everything, so literally, until the nineteen nineties, Darwin's
view that extinction happens extremely slowly, slower than speciation events,
so ultimately you should always have more species, new species
coming up, then you have going extinct. Until the nineteen nineties,
(06:56):
that's the way that it was, That's the way it seemed,
so Chuck, like I said, all of this um stayed
around until and it was the result of like think
about it, think about how you think of mass extinctions now,
you think of a asteroid hitting Earth, destroying everything. And
it wasn't until that that view became widely accepted. And
(07:20):
it was because of this dude um named Alvarez. He
was a geologist, I believe, Walter Alvarez, and in the
seventies he started studying this clay layer that was basically
in the fossil record right at the time the dinosaurs
suddenly died out, and no one could quite explain what
was going on here. They just knew that this must
(07:42):
have happened gradually, so it must be a problem with
the actual fossil record, not our way of thinking. And
there are plenty of problems with the fossil record, which
we'll get into as well. But UM Walter Alvarez said,
let me, 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 arts, which shouldn't
be because it's very, very rare, and we associate a
(08:04):
ridium on Earth as being brought here by, say, like
an asteroid or whatever. Yeah, it's superabundant 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 sixty five million years ago by an asteroid.
And that was in nineteen eighty that they proposed this hypothesis,
(08:24):
and they ran into a lot of resistance UM and
then finally in n 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
(08:44):
died out. So Valvareus 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 a hundred and twelve miles wide, so
it fit the profile and basically ended the Cretaceous period
in the Mesozoic era. And for a while they called
(09:06):
it the Cretaceous Tertiary event, but now they call it
the Cretaceous paleogene event. And did you notice that the
right they noticed the that. Did you notice the Cretaceous,
which is spelled at the sea is denoted with the K.
Did you see why? It's just German. It's just a
German translation for it. I figured out something like that. Yeah,
(09:29):
it was just bugging me. So now we now believe
in asteroid brought us into the Cenozoic era that we
that we enjoyed today. Love the Cnozoic. It's pretty good,
pretty awesome. I mean it's our era, so you gotta
love it. You gotta love it. Um, So Chuck, like
I said, the extinction, extinction can happen, and it does happen,
(09:51):
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 our past. They
estimate maybe up to five billion species have lived on
Earth and more than those are gone. And I love
(10:14):
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, like
everything we know. Um, so, yeah, we've lost 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
(10:39):
they've found from looking at the fossil record from studying
life on Earth is that a species tends to have
about a ten million year lifespan, and there a speciation
event occurs where it branches off from one specie produces
an entirely new species, and that species on average will
stick around for about ten million years, and then something
(11:00):
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
(11:21):
and five species per year, but they think that now
it could be like a times that I've seen up
to a thousand times the normal rate, and I saw
another study from two thousand fourteen, so it's fresh and
it it said that they these researchers calculated the normal
rates and they found that there's between point zero two
(11:42):
three and point one three five extinct species per million
species per year. That doesn't really mean much. It means
so much that it boggles the mind, you know, Like
that's a really strange way of putting it. But basically
they're saying, like, for every million species on on earth
at any given point in time during a year, as
(12:04):
low as point zero two three species will die out.
So in a year, you shouldn't necessarily have that Maine
species in two 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
(12:25):
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 have been on Earth
since the beginning of Earth. It's just impossible to tell um.
Fossils forum under you know, really specific conditions. So you
(12:48):
may think something is gone because it has disappeared from
the fossil record, but all that means is there wasn't
a fossil 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 the fossil of this guy and two thousand years,
but here it is all of a sudden, And even
if it has gone extinct, just where it stopped showing
up from the fossil record doesn't mean, like you said,
(13:11):
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 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. Yeah, Well, if it never
(13:31):
crawled into amber or you know, was buried by 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
(13:52):
lot of math and a lot of speculating with algorithms
and mathematical formulas. This up out, sure, and that's the
only way to do it, really, 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
(14:14):
to still be considered to have a bright future right
as a thing, or to just survive as a species. Right, Yeah,
that's what I mean, damn 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.
(14:37):
But first let's do a little break it un Okay, So, Chuck,
you've been talking about um animals, animal species, going extinct
and then showing up again like the Ceila can't or
at least disappearing from the record, but we as humans
(14:58):
assume they were extinct like a again, the Cela cant
is this fish um that they caught off the coast
of South Africa. When did we talk about it wasn't
into this day in history. I remember we definitely have
hit on that though. I think it was. 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 fifties, sixty million years ago, actually way longer. They
(15:21):
thought it disappeared four million years ago, even more impressive.
So then they caught one off the coast of South
Africa in the thirties. Then they caught another one a
couple of decades later in Madagascar or Mauritius or something,
and um that made the Seila cant a Lazarus species.
You know, I hadn't really gone anywhere. We just thought
(15:43):
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, Lazarus from the Bible
race from the dead like the sea cant again with
the biblical connotations with extinction. Yeah, a lot at stake here,
that's true. Another way something might disappear and you might
(16:05):
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? Um, yeah, maybe just because it's uh,
(16:26):
it's didn't die out 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 were still finding things that we thought were extinct,
so called Lazar species, which goes to make the point
(16:49):
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, 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
(17:12):
natural processor. It is a very natural process, um. And
it typically results from a change in the habitat of
species and it's inability to adapt so it dies out. Yeah.
Competition with other species, hunting by humans, or perhaps the
(17:34):
environment has been tainted 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, Humans can and are
responsible for all four of those. Yeah, and the and
(17:56):
these are This is the extinction that happens over time.
Obviously not a big asteroid hid in the planet. No,
But it can't happen pretty quickly. In this this is
a Tracy Wilson joint and in uh in the introduction,
she mentions the stellar sea cow, which was an Arctic resident.
It was a big old manateee basically, and they were
(18:17):
first described by Arctic explorers in seventeen forty one. By
seventeen sixty eight they were extinct. So it can't happen
on a pretty rapid um scale. Yeah, especially when you
introduce humans. Yeah, and it you know, 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,
(18:40):
well there're no more bees. That's gonna affect pollination and plants,
and those plants are being fed on by other animals,
and it tends to have a snowball effect. Um. Like,
for example, 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 liked to
eat the small animals. Exactly. Which is the answer to
(19:02):
the question why is biodiversity important? Well, because ecosystems thrive
and survive on a wide number of species that are
exists pretty much naturally imbalanced. Um. You know. A pretty
good example of that stuff falling out of balance, um
is the passenger pigeon. Are you familiar. Yeah, they're trying
(19:24):
to de extinct to that thing. Yeah. You want to
talk about the extinction, Yeah, Well, the extinction is um,
exactly what it sounds like. It is sort of Jurassic
parky it is. In two thousand three, some scientists revived
the Burcardo Bucardo, and that's a Spanish mountain goat and
they did it just sort of like Jurassic Park from
(19:45):
DNA that was frozen in time. Unfortunately, although it did
work initially. Uh, the DNA only survived a matter of minutes,
but they did they did count as a d extinction.
I think there was a live birth that survived a
few minutes, wasn't it. Yeah, the the animal itself only
(20:05):
survived a few minutes, though it was like, I should
not be 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 wooly mammoth back,
but we might be able to bring back something kind
of close, right. So, and that raises in this article
(20:26):
that you sent um this 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 where they're gonna live, exactly
where you're gonna 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
(20:48):
uh like maybe it 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 wooly mammoth. Right, And and that also kind
of dovetails of the point that if we have this
ability and routinely UM exercise it, we may be less
(21:11):
inclined to protect the stuff we have now, for like, oh,
it's important enough, we'll just genetically re engineer and bring
it back later. Yeah. I think they in the scene
an article they liken it to just thinking we have
an undo button on the world controls the Yeah, no, good, No,
it's funny because the author doesn't realize that controls the
works outside of Microsoft word too. He specifically mentioned control
(21:35):
Z and Microsoft word, oh words, specifically Microsoft word. He said, yeah,
that's a little weird. He could be a schill and
he was just working it in maybe you know, well
on max though it's not control UM. Maybe he just
smit Microsoft and awkwardly put in word maybe, or maybe
that's the only program he knows. You know, how do
(21:59):
I work this? UM? So you're saying that they're trying
to bring back the the passenger pigeon. Right, So the
passenger pigeon is this really neat example of what happens when, um,
you have a lack of biodiversity. Um, there were when
European settlers came to the New World, apparently like one
(22:21):
out of every four birds in North America was a
passenger pigeon. A quarter of the entire bird population was
passenger pigeons. There's 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
that there were that many. The thing is is, um
(22:43):
if you live, if you read one. 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 they're one of one of
their um great predators. The native American had been wiped
(23:03):
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
(23:23):
turned 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 when extinct. Yeah, the
American Buffalo, we almost sounded them out of existence. Yet
(23:44):
we're not for Ted Turner. Yeah, we tried our best too.
They were just shooting those things for fun at one point, man.
That's disgusting. Disgusting. You hear about the trains just going
through the West and just shooting out the windows at
the Buffalo for no reason and doing nothing, just leaving
them there to rot. Remember we did an episode on
the Buffalo that was a good one. So sad um
(24:05):
So it was good. Well it was sad dude though. So, uh,
if you want to talk about extinction level events, that's
a whole different deal. You want to talk that's not
a slow gradual extinction, that is, uh, some big thing
that happens that wipes out a lot of living things
(24:25):
all at once, and they estimate there's been more than
twenty of these in the history of the world, but
um five of them. They call him the Big Five
for a reason, for good reason, and we'll just go
through those kind of quickly. Now, Uh, the Ordo Viscian extinction,
it's about four ninety million years ago, and that wiped
(24:46):
out about half of all animal families. And the reason
it wiped out about half is because at the time
most of the stuff on are still lived in the sea.
Glaciers formed at this time, lowering sea levels, which meant
that animal is that lived in a certain depth of
the sea, usually towards the surface, lost their habitat boiled
yeah maybe yeah, or were brought down to the level
(25:10):
where their predators like to hang out and we're eating
non 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 were 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.
(25:31):
It's because it was almost five million years ago. It's
kind of tough. Here in number two, I feel like
letterman number two on the top five extinction UM, the
Late Devonian extinction UM, 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
(25:53):
in on family and genera and the big um classification group.
They don't say like, oh, look at these kingdoms that
have disappeared or these phylum. They go down to the
smaller levels and family and genis are just above species
as far as the taxonomy is concerned, exactly. UM. So
(26:14):
what I say about half of the marine genera and
that was three hundred and sixty million years ago, 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 um. This is a pretty big one. This
is the biggest one ever. This is the one they
called the Great Dying, right I think so. I've seen
(26:37):
estimates of as much as nine to nineties six percent
of all life died off during this this extinction event. Um.
In this article it says of marine genera and seventy
of land species when extinct, and that was two hundred
and fifty million years ago. There's a lot of people
(26:58):
who have different ideas about what did it. But do
they think it's possible as volcanic activity creating acid rain. 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 KPg event was the one where
they think, um, they're not exactly how it happened, but
they might have been just broiled and then awesome broiled
(27:19):
on the face of the Earth, which would have happened
pretty quickly to actually and I think that one is
if because they think it may have burst through the
atmosphere right, yes, it rained hot debris everywhere. That's the
one that got ride of the dinosaurs six million years ago.
What is it called the k K hyphen PG, Yeah,
the Cretaceous Paleogene event now, and that's the one where
(27:40):
they they are pretty sure that an asteroid hit um
Central America and sent all of this rock like basically
vaporized rock with 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 they did,
it generated thermal heat enough to bring the broil down
(28:05):
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 like a nuclear winner. Um. Pretty nuts though,
But we skipped number four for no good reason. Um.
The end Triassic extinction killed about of marine families, about
(28:29):
half of marine genera, and that was two million years ago. Yea.
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 fossil record
(28:50):
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 that there's virtually no debate
whatsoever that those account for mass extinction events. Yeah. Um,
(29:13):
it's kind of like 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 happened 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 say, of all living animals species,
(29:35):
not just animals. Animal species just die off. Um, and
it's worldwide. That's another that seems to be another um
factor in defining a mass extinction widespread. Yeah, so um,
these events were pretty big. Yeah, and one of them,
I think one of the researchers in the article you
sent made a pretty good point that the current mass
(29:56):
extinction extinction that we're in now, which we're gonna 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 afterwards, the world starts to
try and recoup. It may take a million years, but
(30:16):
it tries its best to start reforming life and get
going again. Where right 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.
(30:37):
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 for one species it might be a boom time.
(31:02):
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 a hundred million years ago exactly. And there's not
necessarily a set level that or a baseline that Earth
is supposed to be at, right because nature doesn't care
(31:22):
and nature is not like, Oh, we got all these
people here now and things seem pretty modern and they
got smartphones, so maybe we should just protect this version. Uh,
they're like, what was the cycle every what ten million
years for a species? For species? OK, that's a lifespan
of a species on average, So basically every what ten
(31:43):
million years the Earth, it just doesn't care. No, The
point is is, for a species, it's lifespan is ten
million years, and the Earth is not caring every day
of that. It doesn't care. It's just stumbling toward the
next event, basically exactly that will one day probably have.
The thing is is all of this is not to
say that humans are off the hook. All evidence that's
(32:05):
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. So, Chuckers, we've been talking about mass
(32:34):
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 anthroposcene because humans
are having such an impact on Earth that they imagine
(32:54):
ten thousand years from now, geologists will be able to
look and point to this layer and say, here's where
human started. Yeah, let's get in the way back machine.
Oh yeah, let's crank this baby up? Does they have
enough charisee? Oh, it's got enough kerosene, buddy, because we're
going back years, you got, okay? And we're we're going
to go to Australia even because it's just nice down there.
(33:17):
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
these ten ft tall ten ft tall kangaroo looks the
size of it and everything is crazy. But um, let's
(33:38):
just unpack here and let's start propagating you and me. Okay,
I'm gonna make it far just for safety, all right.
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, can we get out of here
(34:00):
because that teen foot tall kangaroos eyeing us, well not anymore,
but he's dead because they believe a lot of people
think that around fifty years ago, when humans started expanding
their footprint, Um, there was a very inconvenient correlation with
(34:24):
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. But um, there there's
a huge debate and it's still it's not settled. Both
sides are like, we're right, right, another one is like,
we're right. The thing is both sides agree like, yeah,
(34:46):
we're in the midst of a six maths 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 cause.
But these are the two debates. So one is the
theory of overkill, which is the one you were just describing. Yeah,
(35:08):
and that was describing Australia fifty years ago. Um, if
we want to get back in the way back machine
and go to North America eleven thousand years ago, uh,
three quarters of our largest animals started to die out,
like the mascodon and the Willie mammoth and the giant beaver,
sabretooth tiger and not coincidentally, probably that's right. Around the
(35:29):
time where we first walked over the bearing 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 mega faun
(35:49):
a huge land animals. 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 and over hunted either these huge like hippo
(36:10):
sized marsupials, or we hunted things that were slightly smaller
that the huge hippo sized marsupials. Eight. 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 soul cause because you probably just can't hunt enough.
(36:32):
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 ten million people moved to Australia overnight,
you know. So they say over hunting is probably not
the soul cause, but maybe a factor. UM. But other
things humans did, like maybe um in Australia they started
burning shrubs to clear land, and maybe those shrubs were
(36:56):
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 cause climate change. But for the most part,
if you are a climate change extinction proponent, you're probably
just believed that this is a natural process that the
(37:18):
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. This one study pointed to a
place called Sahul, which was Australia, New Guinea and Tasmania
all joined together in this megacontinent. There was several tens
of thousands of years ago, and they were saying that
(37:40):
by the time humans arrived in Sahul or Australia, most
of the megaphone it was already gone. He has gone
as a result of climate change and there's no evidence
that we had a tool kit capable of killing these animals, um,
you know, at this time. So the debate still rages on.
And you know, there's been several ice ages that didn't
(38:02):
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 um of mapping large animals during this period a
hundred and thirty two thousand to a thousand years ago,
and it was the first time they were able to
(38:23):
really get a fine point on this geographical variation in
the and species loss. And they did find that a
hundred and seventy seven species of large mammals disappeared during
that period where we were starting to spread out as
a species, and which apparently is as this put in
this article, a massive loss. Yeah, and they said, you know,
(38:46):
they expect these kind of things to happen on an island,
like if you go to Hawaii or you know, any island.
They say that that survival is the exception when humans
invade an island, But for to happen on like a continent,
it's it's pretty uh, it's pretty as going to think
about the human impact. It's still an island. Well, yeah,
I guess that's a good point. Um. But the jury
(39:07):
is still out though, and exactly what's causing this. Most
scientists agree that we are in an 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.
A third of amphibians, I believe, Yeah, and a quarter
(39:29):
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 faking the criteria
for a mass extinction. Yeah, they're basically chalking up to
the pace of human expansion. And you know, if you
consider that, uh, farming and logging and building roads and buildings,
and most of the world's waterways have been diverted or
(39:52):
damned at this point or manipulated somehow. Um. Only two
percent of rivers in the United States run unimpeded. Everything
else has been altered in some way. Chemical plants um
affecting you know CEO two in the atmosphere, it's having
an effect. And the c O two actually in the
atmosphere is having another effect um called ocean acidification, which
(40:16):
has been described as global warming's evil twin. As more
and more C O two gets released in the atmosphere um,
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.
(40:38):
But as to kind of demonstrate how mass extinction is
bad for one species great for another, jellyfish populations are booming,
so probably because 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
(40:59):
possible that the next thousand years will see the rise
of the jellyfish. Is 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 fifty years. They think might exceed what has
happened in the past previous fifty million years. So in
the past fifty years they've changed the basically changed the
(41:21):
chemical makeup of the ocean more than the past fifty
million and speaking of fifty years, apparently in the next
fifty years and 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
the extinction. Well here, Um, you just saw when we
(41:45):
were in we were in Sahol. Well, yeah, it was nice,
but I want to like I wanted to come in
the way back machine and bring it to Atlanta. 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 extinct animals that have
(42:08):
been rediscovered, which is not the same thing as being
re engineered. What was this in I O nine Particle nine?
And some of those are pretty good. The Bermuda, petrel
and uh disappeared they fought in the sixteen hundreds, but
rediscovered nineteen fifty one. There's about a hundred and eighty
of those alive today. Uh. Let me see here what
else is good? Well? We also we already talked about
(42:29):
the Celo camp, the cuban, uh, soulan, don, Solenodon, excuse me.
Discovered in eighteen sixty one. Um has only been caught
thirty seven times in the history of the world. In
in ninev they thought it was an extinct it's like
a weird rat like species. But then they found one
in the seventies, and then another one in two thousand three. Huh,
(42:52):
so like welcome back Cuban Solenodon. So it's like caught
during the seventies and then during the period of the
seventies revival in the early two thousands. That's right. Nice, uh,
Gilbert's po po turu and these have weird names. That's
why they went extinct, because you couldn't say, you know
that we we should save the the what yeah, forty
(43:17):
one This is a rabbit size marsupial in Australia and
it last appeared in eighteen seventy nine. And they thought,
while this thing's gone up until came back out and
poked his head around and got caught in a few traps.
But currently less than a hundred of those in the world.
And so those are just a few of the ten,
and there's more than ten, obviously. But it's always a
(43:38):
good story. Sure, it is heartwarming. We think this thing
is 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. Uh and you can also read
this article on how stuff works dot com by typing
extinction into the handy search bar. And since I said that,
(44:00):
time for listener mail, I'm gonna call this police interrogation
follow up from Matt pope Hey in Victoria, British Columbia.
All right, thank you to Vancouver, by the way, for
two great shows after our great shows in Toronto and Vancouver.
Very supportive people. And boy that second crowd Vancouver was
(44:23):
drunk and rowdy. Hey, guys, just listen to police interrogation.
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 nine one to report it. Cops snabbed the
perpetrator and a few days later asked me to come
(44:43):
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.
The weird experience, even though I wasn't accused of a
crime and the cop was polite and it's questioning the
interrogation room setting, 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
(45:04):
you had been watching my body language did the one
way mirror, you would have thought I was guilty and
he was just a witness. The second story is very similar.
Every year a local courthouse as a public event where
they give tours and put on a mock trial and
actually hang someone kidding. That was pretty good. It's supposed
to be educational and fund My father is a lawyer.
In one year asked me, I would like to play
(45:26):
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 afterwards 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
(45:48):
of treating someone like a criminal and make him appear
guilty reminds me of the Stanford prison study that we've
talked about. And there's a psychologist nuts about that psychologies
Nuts video and are you tube channel about the Stanford
prison experiment. Yeah, that's a good one. You should check
that out. I hope you guys um never have to
find out the hard way you'll react to police interrogation
(46:09):
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, Um. That's cookie about your town
doing mock trials and stuff like that. Yeah, like hanging
a guy, Yeah, crazy said, it's fun. The only the
only thing that's okay about is they make the guy
look like Hitler, right, So it's like hanging Hitler every year,
(46:30):
which everybody can get behind. Yeah, they call it the
Hitler hanging. 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 s y s K Podcast.
You can join us on Facebook, dot com, slash stuff
you Should Know, You can send us an email to
Stuff Podcast at how stuff works dot com, and as always,
(46:54):
check out our home on the web, Stuff you Should
Know dot com. For more on this and thousands of
other topics, visit how stuff Works dot com m
Welcome to you stuff you should know from house Stuff
Works dot com. Hey, and welcome to the podcast. Don't
Josh Clark, there's Charles W. Chucker's Bryant. Jerry is over there.
I'm gonna said your last name, Jerry. How weird. And
then today we have a fourth character in the in
(00:23):
the studio with this Chuck. This a scent scent coming
together to make like a changeable human being. So you
are wearing Patuli, uh not wearing well, you have Petulia
on you as a result of one of Emily's sugar
scrubs right from Mama and it's Love your Mama dot com. Okay.
(00:45):
And then Jerry is contributing to that with um an enchilada,
so that all of them combined, I would say, there's
like 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
(01:06):
studio we'll probably become extinct. That's a good one. Did
you like that? Yeah? I've had that plan since probably
two weeks ago. How are you doing, man, I'm good.
I've been thinking of Busta Rhymes all day. Why did
he have a song about extinction had an album called
the Extinction Level Event. Oh yeah, yeah, and that was
(01:29):
in one of the songs that sounds super nineties. Well
let's Buster Rhymes has. But I mean even those words
extinction level Event. People were worried about stuff because of
like the turn of the millennium. You remember, Exiles is
a huge hit Deep Impact and Armageddon came out of
like on the same day basically, and both were hits.
(01:52):
Like people were just nervous and um. As a result,
Buster Rhymes is 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 yeah, leaders in the
New School and his early work with Chip call Quest.
(02:13):
Oh yeah, he guessed it on one of my favorite
songs is What's the Scenario? Was that the one I
think so? I mean it was definitely on that one,
but they that was the one also where I think, um, yeah,
he makes fun of people with saggy pants because it
was so new. Apparently Bustter Rhames wasn't down with it yet. Yeah,
just pretty ironic because he got hardcore into that. That
(02:36):
was raw, raw, like a dungeon dragon, right, it's pretty awesome.
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 Elizabeth
(02:57):
um Colbert or Corp Colbert depending on what if you
watch the Colbert Report. 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, and like she wrote an
article in the New Yorker. She's a New Yorker journalist
(03:19):
that was basically the predecessor to the book. You know
how they do. Like, I need an extra twenty grand,
so I'll just write a synopsis of the book I'm writing.
Um And it's a good article, and we worked from that.
There's another one from the New York Review of Books
called They're taking Over about the explosion of jellyfish. UM.
On how stuff Works, there's one that I wrote years
(03:39):
back called will We Soon Be Extinct? And there's another
how stuff Works one that we've done an episode on
called wise bio Diversity Important. Yeah, and I found one
in an I O nine for animals that we thought
were extinct but miraculously pop back up nice, which is
always a good story. Oh yeah, it's a it's a
(04:01):
heartwarming story of triumph of raversity 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 when I
was at the Big Fish. They just caught that thing
one day, yeah, and said, hey, wait a minute, Yeah,
(04:24):
this thing's extinct. It's supposed to be. And we'll talk
about how and why things fall off. But things do
fall off, and it seems that there is a um
that the whole thing is a very natural process. Extinctionists.
But for a very long time, I guess scientists um
(04:46):
believed that the God created all of the animals on
Earth and that his will was too perfect, his creation
was too divine to even allow for extinct and so
because they were aware of the fossil record, they rationalized
these huge bones of animals that he didn't see anywhere
(05:06):
as we just haven't found him yet. Well yeah, and
this was all the way up and you know, into
the nineteenth 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.
He's like, it's found to be out there somewhere, guys,
to be careful. But there were some other smarter people,
(05:27):
um like George Cuvier in eighteen twelve, he was pretty
ahead of his time. In fact, in eighteen twelve he
was way ahead of his time because he published an
essay called Revolutions on the Surface of the Globe and
he kind of asserted that now things can go extinct,
and he called them a species produced lost species and
(05:51):
basically hypothesized that there have been cataclysmic events that have
caused extinctions. In so many words, this is basically flew
in the face of this that like, not only was
their 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.
(06:14):
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 well, Darwin's right about
(06:34):
just about everything, so literally, until the nineteen nineties, Darwin's
view that extinction happens extremely slowly, slower than speciation events,
so ultimately you should always have more species, new species
coming up, then you have going extinct. Until the nineteen nineties,
(06:56):
that's the way that it was, That's the way it seemed,
so Chuck, like I said, all of this um stayed
around until and it was the result of like think
about it, think about how you think of mass extinctions now,
you think of a asteroid hitting Earth, destroying everything. And
it wasn't until that that view became widely accepted. And
(07:20):
it was because of this dude um named Alvarez. He
was a geologist, I believe, Walter Alvarez, and in the
seventies he started studying this clay layer that was basically
in the fossil record right at the time the dinosaurs
suddenly died out, and no one could quite explain what
was going on here. They just knew that this must
(07:42):
have happened gradually, so it must be a problem with
the actual fossil record, not our way of thinking. And
there are plenty of problems with the fossil record, which
we'll get into as well. But UM Walter Alvarez said,
let me, 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 arts, which shouldn't
be because it's very, very rare, and we associate a
(08:04):
ridium on Earth as being brought here by, say, like
an asteroid or whatever. Yeah, it's superabundant 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 sixty five million years ago by an asteroid.
And that was in nineteen eighty that they proposed this hypothesis,
(08:24):
and they ran into a lot of resistance UM and
then finally in n 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
(08:44):
died out. So Valvareus 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 a hundred and twelve miles wide, so
it fit the profile and basically ended the Cretaceous period
in the Mesozoic era. And for a while they called
(09:06):
it the Cretaceous Tertiary event, but now they call it
the Cretaceous paleogene event. And did you notice that the
right they noticed the that. Did you notice the Cretaceous,
which is spelled at the sea is denoted with the K.
Did you see why? It's just German. It's just a
German translation for it. I figured out something like that. Yeah,
(09:29):
it was just bugging me. So now we now believe
in asteroid brought us into the Cenozoic era that we
that we enjoyed today. Love the Cnozoic. It's pretty good,
pretty awesome. I mean it's our era, so you gotta
love it. You gotta love it. Um, So Chuck, like
I said, the extinction, extinction can happen, and it does happen,
(09:51):
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 our past. They
estimate maybe up to five billion species have lived on
Earth and more than those are gone. And I love
(10:14):
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, like
everything we know. Um, so, yeah, we've lost 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
(10:39):
they've found from looking at the fossil record from studying
life on Earth is that a species tends to have
about a ten million year lifespan, and there a speciation
event occurs where it branches off from one specie produces
an entirely new species, and that species on average will
stick around for about ten million years, and then something
(11:00):
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
(11:21):
and five species per year, but they think that now
it could be like a times that I've seen up
to a thousand times the normal rate, and I saw
another study from two thousand fourteen, so it's fresh and
it it said that they these researchers calculated the normal
rates and they found that there's between point zero two
(11:42):
three and point one three five extinct species per million
species per year. That doesn't really mean much. It means
so much that it boggles the mind, you know, Like
that's a really strange way of putting it. But basically
they're saying, like, for every million species on on earth
at any given point in time during a year, as
(12:04):
low as point zero two three species will die out.
So in a year, you shouldn't necessarily have that Maine
species in two 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
(12:25):
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 have been on Earth
since the beginning of Earth. It's just impossible to tell um.
Fossils forum under you know, really specific conditions. So you
(12:48):
may think something is gone because it has disappeared from
the fossil record, but all that means is there wasn't
a fossil 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 the fossil of this guy and two thousand years,
but here it is all of a sudden, And even
if it has gone extinct, just where it stopped showing
up from the fossil record doesn't mean, like you said,
(13:11):
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 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. Yeah, Well, if it never
(13:31):
crawled into amber or you know, was buried by 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
(13:52):
lot of math and a lot of speculating with algorithms
and mathematical formulas. This up out, sure, and that's the
only way to do it, really, 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
(14:14):
to still be considered to have a bright future right
as a thing, or to just survive as a species. Right, Yeah,
that's what I mean, damn 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.
(14:37):
But first let's do a little break it un Okay, So, Chuck,
you've been talking about um animals, animal species, going extinct
and then showing up again like the Ceila can't or
at least disappearing from the record, but we as humans
(14:58):
assume they were extinct like a again, the Cela cant
is this fish um that they caught off the coast
of South Africa. When did we talk about it wasn't
into this day in history. I remember we definitely have
hit on that though. I think it was. 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 fifties, sixty million years ago, actually way longer. They
(15:21):
thought it disappeared four million years ago, even more impressive.
So then they caught one off the coast of South
Africa in the thirties. Then they caught another one a
couple of decades later in Madagascar or Mauritius or something,
and um that made the Seila cant a Lazarus species.
You know, I hadn't really gone anywhere. We just thought
(15:43):
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, Lazarus from the Bible
race from the dead like the sea cant again with
the biblical connotations with extinction. Yeah, a lot at stake here,
that's true. Another way something might disappear and you might
(16:05):
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? Um, yeah, maybe just because it's uh,
(16:26):
it's didn't die out 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 were still finding things that we thought were extinct,
so called Lazar species, which goes to make the point
(16:49):
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, 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
(17:12):
natural processor. It is a very natural process, um. And
it typically results from a change in the habitat of
species and it's inability to adapt so it dies out. Yeah.
Competition with other species, hunting by humans, or perhaps the
(17:34):
environment has been tainted 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, Humans can and are
responsible for all four of those. Yeah, and the and
(17:56):
these are This is the extinction that happens over time.
Obviously not a big asteroid hid in the planet. No,
But it can't happen pretty quickly. In this this is
a Tracy Wilson joint and in uh in the introduction,
she mentions the stellar sea cow, which was an Arctic resident.
It was a big old manateee basically, and they were
(18:17):
first described by Arctic explorers in seventeen forty one. By
seventeen sixty eight they were extinct. So it can't happen
on a pretty rapid um scale. Yeah, especially when you
introduce humans. Yeah, and it you know, 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,
(18:40):
well there're no more bees. That's gonna affect pollination and plants,
and those plants are being fed on by other animals,
and it tends to have a snowball effect. Um. Like,
for example, 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 liked to
eat the small animals. Exactly. Which is the answer to
(19:02):
the question why is biodiversity important? Well, because ecosystems thrive
and survive on a wide number of species that are
exists pretty much naturally imbalanced. Um. You know. A pretty
good example of that stuff falling out of balance, um
is the passenger pigeon. Are you familiar. Yeah, they're trying
(19:24):
to de extinct to that thing. Yeah. You want to
talk about the extinction, Yeah, Well, the extinction is um,
exactly what it sounds like. It is sort of Jurassic
parky it is. In two thousand three, some scientists revived
the Burcardo Bucardo, and that's a Spanish mountain goat and
they did it just sort of like Jurassic Park from
(19:45):
DNA that was frozen in time. Unfortunately, although it did
work initially. Uh, the DNA only survived a matter of minutes,
but they did they did count as a d extinction.
I think there was a live birth that survived a
few minutes, wasn't it. Yeah, the the animal itself only
(20:05):
survived a few minutes, though it was like, I should
not be 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 wooly mammoth back,
but we might be able to bring back something kind
of close, right. So, and that raises in this article
(20:26):
that you sent um this 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 where they're gonna live, exactly
where you're gonna 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
(20:48):
uh like maybe it 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 wooly mammoth. Right, And and that also kind
of dovetails of the point that if we have this
ability and routinely UM exercise it, we may be less
(21:11):
inclined to protect the stuff we have now, for like, oh,
it's important enough, we'll just genetically re engineer and bring
it back later. Yeah. I think they in the scene
an article they liken it to just thinking we have
an undo button on the world controls the Yeah, no, good, No,
it's funny because the author doesn't realize that controls the
works outside of Microsoft word too. He specifically mentioned control
(21:35):
Z and Microsoft word, oh words, specifically Microsoft word. He said, yeah,
that's a little weird. He could be a schill and
he was just working it in maybe you know, well
on max though it's not control UM. Maybe he just
smit Microsoft and awkwardly put in word maybe, or maybe
that's the only program he knows. You know, how do
(21:59):
I work this? UM? So you're saying that they're trying
to bring back the the passenger pigeon. Right, So the
passenger pigeon is this really neat example of what happens when, um,
you have a lack of biodiversity. Um, there were when
European settlers came to the New World, apparently like one
(22:21):
out of every four birds in North America was a
passenger pigeon. A quarter of the entire bird population was
passenger pigeons. There's 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
that there were that many. The thing is is, um
(22:43):
if you live, if you read one. 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 they're one of one of
their um great predators. The native American had been wiped
(23:03):
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
(23:23):
turned 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 when extinct. Yeah, the
American Buffalo, we almost sounded them out of existence. Yet
(23:44):
we're not for Ted Turner. Yeah, we tried our best too.
They were just shooting those things for fun at one point, man.
That's disgusting. Disgusting. You hear about the trains just going
through the West and just shooting out the windows at
the Buffalo for no reason and doing nothing, just leaving
them there to rot. Remember we did an episode on
the Buffalo that was a good one. So sad um
(24:05):
So it was good. Well it was sad dude though. So, uh,
if you want to talk about extinction level events, that's
a whole different deal. You want to talk that's not
a slow gradual extinction, that is, uh, some big thing
that happens that wipes out a lot of living things
(24:25):
all at once, and they estimate there's been more than
twenty of these in the history of the world, but
um five of them. They call him the Big Five
for a reason, for good reason, and we'll just go
through those kind of quickly. Now, Uh, the Ordo Viscian extinction,
it's about four ninety million years ago, and that wiped
(24:46):
out about half of all animal families. And the reason
it wiped out about half is because at the time
most of the stuff on are still lived in the sea.
Glaciers formed at this time, lowering sea levels, which meant
that animal is that lived in a certain depth of
the sea, usually towards the surface, lost their habitat boiled
yeah maybe yeah, or were brought down to the level
(25:10):
where their predators like to hang out and we're eating
non 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 were 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.
(25:31):
It's because it was almost five million years ago. It's
kind of tough. Here in number two, I feel like
letterman number two on the top five extinction UM, the
Late Devonian extinction UM, 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
(25:53):
in on family and genera and the big um classification group.
They don't say like, oh, look at these kingdoms that
have disappeared or these phylum. They go down to the
smaller levels and family and genis are just above species
as far as the taxonomy is concerned, exactly. UM. So
(26:14):
what I say about half of the marine genera and
that was three hundred and sixty million years ago, 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 um. This is a pretty big one. This
is the biggest one ever. This is the one they
called the Great Dying, right I think so. I've seen
(26:37):
estimates of as much as nine to nineties six percent
of all life died off during this this extinction event. Um.
In this article it says of marine genera and seventy
of land species when extinct, and that was two hundred
and fifty million years ago. There's a lot of people
(26:58):
who have different ideas about what did it. But do
they think it's possible as volcanic activity creating acid rain. 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 KPg event was the one where
they think, um, they're not exactly how it happened, but
they might have been just broiled and then awesome broiled
(27:19):
on the face of the Earth, which would have happened
pretty quickly to actually and I think that one is
if because they think it may have burst through the
atmosphere right, yes, it rained hot debris everywhere. That's the
one that got ride of the dinosaurs six million years ago.
What is it called the k K hyphen PG, Yeah,
the Cretaceous Paleogene event now, and that's the one where
(27:40):
they they are pretty sure that an asteroid hit um
Central America and sent all of this rock like basically
vaporized rock with 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 they did,
it generated thermal heat enough to bring the broil down
(28:05):
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 like a nuclear winner. Um. Pretty nuts though,
But we skipped number four for no good reason. Um.
The end Triassic extinction killed about of marine families, about
(28:29):
half of marine genera, and that was two million years ago. Yea.
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 fossil record
(28:50):
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 that there's virtually no debate
whatsoever that those account for mass extinction events. Yeah. Um,
(29:13):
it's kind of like 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 happened 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 say, of all living animals species,
(29:35):
not just animals. Animal species just die off. Um, and
it's worldwide. That's another that seems to be another um
factor in defining a mass extinction widespread. Yeah, so um,
these events were pretty big. Yeah, and one of them,
I think one of the researchers in the article you
sent made a pretty good point that the current mass
(29:56):
extinction extinction that we're in now, which we're gonna 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 afterwards, the world starts to
try and recoup. It may take a million years, but
(30:16):
it tries its best to start reforming life and get
going again. Where right 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.
(30:37):
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 for one species it might be a boom time.
(31:02):
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 a hundred million years ago exactly. And there's not
necessarily a set level that or a baseline that Earth
is supposed to be at, right because nature doesn't care
(31:22):
and nature is not like, Oh, we got all these
people here now and things seem pretty modern and they
got smartphones, so maybe we should just protect this version. Uh,
they're like, what was the cycle every what ten million
years for a species? For species? OK, that's a lifespan
of a species on average, So basically every what ten
(31:43):
million years the Earth, it just doesn't care. No, The
point is is, for a species, it's lifespan is ten
million years, and the Earth is not caring every day
of that. It doesn't care. It's just stumbling toward the
next event, basically exactly that will one day probably have.
The thing is is all of this is not to
say that humans are off the hook. All evidence that's
(32:05):
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. So, Chuckers, we've been talking about mass
(32:34):
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 anthroposcene because humans
are having such an impact on Earth that they imagine
(32:54):
ten thousand years from now, geologists will be able to
look and point to this layer and say, here's where
human started. Yeah, let's get in the way back machine.
Oh yeah, let's crank this baby up? Does they have
enough charisee? Oh, it's got enough kerosene, buddy, because we're
going back years, you got, okay? And we're we're going
to go to Australia even because it's just nice down there.
(33:17):
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
these ten ft tall ten ft tall kangaroo looks the
size of it and everything is crazy. But um, let's
(33:38):
just unpack here and let's start propagating you and me. Okay,
I'm gonna make it far just for safety, all right.
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, can we get out of here
(34:00):
because that teen foot tall kangaroos eyeing us, well not anymore,
but he's dead because they believe a lot of people
think that around fifty years ago, when humans started expanding
their footprint, Um, there was a very inconvenient correlation with
(34:24):
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. But um, there there's
a huge debate and it's still it's not settled. Both
sides are like, we're right, right, another one is like,
we're right. The thing is both sides agree like, yeah,
(34:46):
we're in the midst of a six maths 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 cause.
But these are the two debates. So one is the
theory of overkill, which is the one you were just describing. Yeah,
(35:08):
and that was describing Australia fifty years ago. Um, if
we want to get back in the way back machine
and go to North America eleven thousand years ago, uh,
three quarters of our largest animals started to die out,
like the mascodon and the Willie mammoth and the giant beaver,
sabretooth tiger and not coincidentally, probably that's right. Around the
(35:29):
time where we first walked over the bearing 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 mega faun
(35:49):
a huge land animals. 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 and over hunted either these huge like hippo
(36:10):
sized marsupials, or we hunted things that were slightly smaller
that the huge hippo sized marsupials. Eight. 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 soul cause because you probably just can't hunt enough.
(36:32):
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 ten million people moved to Australia overnight,
you know. So they say over hunting is probably not
the soul cause, but maybe a factor. UM. But other
things humans did, like maybe um in Australia they started
burning shrubs to clear land, and maybe those shrubs were
(36:56):
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 cause climate change. But for the most part,
if you are a climate change extinction proponent, you're probably
just believed that this is a natural process that the
(37:18):
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. This one study pointed to a
place called Sahul, which was Australia, New Guinea and Tasmania
all joined together in this megacontinent. There was several tens
of thousands of years ago, and they were saying that
(37:40):
by the time humans arrived in Sahul or Australia, most
of the megaphone it was already gone. He has gone
as a result of climate change and there's no evidence
that we had a tool kit capable of killing these animals, um,
you know, at this time. So the debate still rages on.
And you know, there's been several ice ages that didn't
(38:02):
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 um of mapping large animals during this period a
hundred and thirty two thousand to a thousand years ago,
and it was the first time they were able to
(38:23):
really get a fine point on this geographical variation in
the and species loss. And they did find that a
hundred and seventy seven species of large mammals disappeared during
that period where we were starting to spread out as
a species, and which apparently is as this put in
this article, a massive loss. Yeah, and they said, you know,
(38:46):
they expect these kind of things to happen on an island,
like if you go to Hawaii or you know, any island.
They say that that survival is the exception when humans
invade an island, But for to happen on like a continent,
it's it's pretty uh, it's pretty as going to think
about the human impact. It's still an island. Well, yeah,
I guess that's a good point. Um. But the jury
(39:07):
is still out though, and exactly what's causing this. Most
scientists agree that we are in an 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.
A third of amphibians, I believe, Yeah, and a quarter
(39:29):
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 faking the criteria
for a mass extinction. Yeah, they're basically chalking up to
the pace of human expansion. And you know, if you
consider that, uh, farming and logging and building roads and buildings,
and most of the world's waterways have been diverted or
(39:52):
damned at this point or manipulated somehow. Um. Only two
percent of rivers in the United States run unimpeded. Everything
else has been altered in some way. Chemical plants um
affecting you know CEO two in the atmosphere, it's having
an effect. And the c O two actually in the
atmosphere is having another effect um called ocean acidification, which
(40:16):
has been described as global warming's evil twin. As more
and more C O two gets released in the atmosphere um,
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.
(40:38):
But as to kind of demonstrate how mass extinction is
bad for one species great for another, jellyfish populations are booming,
so probably because 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
(40:59):
possible that the next thousand years will see the rise
of the jellyfish. Is 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 fifty years. They think might exceed what has
happened in the past previous fifty million years. So in
the past fifty years they've changed the basically changed the
(41:21):
chemical makeup of the ocean more than the past fifty
million and speaking of fifty years, apparently in the next
fifty years and 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
the extinction. Well here, Um, you just saw when we
(41:45):
were in we were in Sahol. Well, yeah, it was nice,
but I want to like I wanted to come in
the way back machine and bring it to Atlanta. 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 extinct animals that have
(42:08):
been rediscovered, which is not the same thing as being
re engineered. What was this in I O nine Particle nine?
And some of those are pretty good. The Bermuda, petrel
and uh disappeared they fought in the sixteen hundreds, but
rediscovered nineteen fifty one. There's about a hundred and eighty
of those alive today. Uh. Let me see here what
else is good? Well? We also we already talked about
(42:29):
the Celo camp, the cuban, uh, soulan, don, Solenodon, excuse me.
Discovered in eighteen sixty one. Um has only been caught
thirty seven times in the history of the world. In
in ninev they thought it was an extinct it's like
a weird rat like species. But then they found one
in the seventies, and then another one in two thousand three. Huh,
(42:52):
so like welcome back Cuban Solenodon. So it's like caught
during the seventies and then during the period of the
seventies revival in the early two thousands. That's right. Nice, uh,
Gilbert's po po turu and these have weird names. That's
why they went extinct, because you couldn't say, you know
that we we should save the the what yeah, forty
(43:17):
one This is a rabbit size marsupial in Australia and
it last appeared in eighteen seventy nine. And they thought,
while this thing's gone up until came back out and
poked his head around and got caught in a few traps.
But currently less than a hundred of those in the world.
And so those are just a few of the ten,
and there's more than ten, obviously. But it's always a
(43:38):
good story. Sure, it is heartwarming. We think this thing
is 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. Uh and you can also read
this article on how stuff works dot com by typing
extinction into the handy search bar. And since I said that,
(44:00):
time for listener mail, I'm gonna call this police interrogation
follow up from Matt pope Hey in Victoria, British Columbia.
All right, thank you to Vancouver, by the way, for
two great shows after our great shows in Toronto and Vancouver.
Very supportive people. And boy that second crowd Vancouver was
(44:23):
drunk and rowdy. Hey, guys, just listen to police interrogation.
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 nine one to report it. Cops snabbed the
perpetrator and a few days later asked me to come
(44:43):
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.
The weird experience, even though I wasn't accused of a
crime and the cop was polite and it's questioning the
interrogation room setting, 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
(45:04):
you had been watching my body language did the one
way mirror, you would have thought I was guilty and
he was just a witness. The second story is very similar.
Every year a local courthouse as a public event where
they give tours and put on a mock trial and
actually hang someone kidding. That was pretty good. It's supposed
to be educational and fund My father is a lawyer.
In one year asked me, I would like to play
(45:26):
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 afterwards 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
(45:48):
of treating someone like a criminal and make him appear
guilty reminds me of the Stanford prison study that we've
talked about. And there's a psychologist nuts about that psychologies
Nuts video and are you tube channel about the Stanford
prison experiment. Yeah, that's a good one. You should check
that out. I hope you guys um never have to
find out the hard way you'll react to police interrogation
(46:09):
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, Um. That's cookie about your town
doing mock trials and stuff like that. Yeah, like hanging
a guy, Yeah, crazy said, it's fun. The only the
only thing that's okay about is they make the guy
look like Hitler, right, So it's like hanging Hitler every year,
(46:30):
which everybody can get behind. Yeah, they call it the
Hitler hanging. 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 s y s K Podcast.
You can join us on Facebook, dot com, slash stuff
you Should Know, You can send us an email to
Stuff Podcast at how stuff works dot com, and as always,
(46:54):
check out our home on the web, Stuff you Should
Know dot com. For more on this and thousands of
other topics, visit how stuff Works dot com m
Stuff You Should Know News
Hosts And Creators
Josh Clark
Chuck Bryant
Show Links
Order Our BookRSSStoreSYSK ArmyAboutPopular Podcasts
Dateline NBC
Current and classic episodes, featuring compelling true-crime mysteries, powerful documentaries and in-depth investigations.
Death, Sex & Money
Anna Sale explores the big questions and hard choices that are often left out of polite conversation.
Stuff You Should Know
If you've ever wanted to know about champagne, satanism, the Stonewall Uprising, chaos theory, LSD, El Nino, true crime and Rosa Parks, then look no further. Josh and Chuck have you covered.