July 4, 2020 • 43 mins
Where do teeth come from and how do different dental variations in the animal world force us to rethink our glorious chompers? In this episode of Stuff to Blow Your Mind, Robert and Joe explore dental evolution and the wondrous marching molars of elephants and manatees. (Originally published 7/23/2019)
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Episode Transcript
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Speaker 1 (00:05):
Hey, welcome to Stuff to Blow Your Mind. My name
is Robert Lamb and I'm Joe McCormick, and it's Saturday.
Time to go into the vault for an older episode
of the show. This one originally aired on July nineteen.
It's about teeth. I'm ready to bite. Yeah, well, let's
bite right in and figure out what we're biting with.
(00:27):
Welcome to Stuff to Blow Your Mind, a production of
I Heart Radios How to Work. Hey you, welcome to
Stuff to Blow Your Mind. My name is Robert Lamb
and I'm Joe McCormick. And if you've been listening to show,
you know we just had our friend Katie Golden from
Creature feature on. I think it was the episode right
(00:48):
before this one where we talked about teeth with with
Katie and that was a lot of fun. But Robert,
I couldn't stop thinking about teeth. Oh yeah, I mean,
teeth are weird. Teeth are wonderful and strange and grotesque.
I was actually just at the dentist yesterday for a checkup,
and I just kept thinking about just how weird it
(01:09):
is that that I just regularly go to this place
and pay another human being to reach into my mouth
with special instruments and clean my weird bone like jaw protutions.
The outside bones outside bones. Never forget your teeth are
outside bones. Their bones that you wash. Oh this this
is from Kimmy Schmidt. Right, Yeah, Titus Syndromedon sings that song.
(01:29):
I think he's auditioning for like a chewing gum commercial,
But he's actually wrong, I'm sorry to say, despite how
much I love that moment from the show, teeth are
not outside bones. They are not bones at all. They're
totally different thing. We can explain that in a minute.
But yeah, yeah, I mean, well, let's go ahead and
get into it. So, yeah, our teeth are bone like
in many respects. Uh yeah, but they are not bones.
(01:52):
So just for an example, bones are composed of calcium, phosphorus, sodium,
and other minerals. Uh and but mostly it's the protein
call legend that forms the living growing collagen framework in bones.
Bones have impressive regenerative powers. You break a bone, it
can even like a really vicious break of a bone,
and it can heal back. Also, bone marrow produces red
(02:16):
and white blood cells. Teeth do not have bone marrow. Instead,
they have dental pulp. So teeth, on the other hand,
are you know, they're composed of calcium, phosphorus and other minerals.
They're harder than any bone that we have in the body. Yeah,
but they also lack the regenerative powers of bones. So
if you crack or break a tooth, you're gonna need
at least a root canal, if not a total extraction.
(02:38):
That is kind of strange. That seems I wonder what
the evolutionary reason for that is. I would expect, you know,
there would be a strong pressure on the ability to
regenerate teeth. Well, it depends on how this really gets
into like the bigger questions of of biological mortality, right,
like what do you need your teeth for? How long
(03:00):
are you going to be a viable organism? How long
do you need to live, you know, in order to
accomplish your genetic mission of you know, reproduction, uh and
so forth, and and you know, the evolution isn't really
concerned with long term dental health beyond that point. Well maybe, yeah,
maybe we don't need teeth because um, well, for one thing,
we're not like sharks, right, We're not just like biting
(03:22):
indiscriminately into whole organisms and you know, cross bones and
stuff like that. We we tend to if we're eating
an animal, we kill it before we start biting into it.
Uh so you know, you you would be able to
have the time to seek out the soft parts to
bite into, and so you're not using your teeth in
a kind of like violent, fast moving kind of way
(03:45):
like a lot of other organisms would. Yeah, and and
and it really drives home one of the one of
the key and I guess kind of obvious things that
we're gonna we're gonna touch on here and there is
that as as organisms evolve, their teeth are going to
change to meet the demands of their diet. And if
if you're if you do not need your robust teeth
of old anymore, well, those those teeth are going to change,
(04:08):
and you're gonna end up with a dental model that
is going to be more in keeping with what you're
actually going to use your choppers for. It's funny, you
could think of teeth in a way as a form
of convergent evolution. So like the same way that you
see uh, wings evolving independently in different lines of animals.
It's not that everything on Earth that has wings evolved
(04:32):
from a common winged ancestor. So wings arose in one
case in insects, and then they separately arose in you know, mammals,
They rose in bats and stuff, and then they separately
arose in the dinosaurs that became birds, and then also
in the other the flying reptiles, right, which are not dinosaurs,
but also independently evolved wings. Uh. So, so you see
(04:55):
winged flight evolving over and over despite the fact that
all these organisms don't come from wings of a common
ancestor organism that I mean, I guess if you go
far back enough, they all do have a common ancestor,
but it didn't have wings. Um. And you can see
a kind of similar thing in different things we call
teeth that you know, lots of organisms have an opening
(05:16):
of the elementary tract. They've got a mouth of some
kind or another, and it it just often happens to
be the case that organisms evolve a need to mash
and crush and cut things that are going into the
front of the elementary tract. And that's how you get
these different evolutions of things that are like teeth. Uh.
And there there are a lot of different things you
(05:37):
might call teeth, and not all are evolutionarily related to
the calcified structures we see in animals like ourselves. In fact,
one great example of a whole different kind of of
twothworld that I was thinking about just recently is uh.
It reminds me of this controversy over the mouth of
a Cambrian predator that I have been calling Anomala carus
(06:01):
or Anomala carress. I just found out that some people
pronounce it anomalachrus. And now now I feel like my
whole world has been turned on its head. I don't
know which to say, but I think I'm gonna keep
saying Anomala caress even if that's wrong, for the sake
of consistency. This is this is basically, if you've ever
been to a natural history museum, you've probably seen a
representation of this. Uh, this this prehistoric fish. Yeah, I mean,
(06:25):
well not a fish, well fish like organism and the
this long predating fish. So the Cambrian period, of course,
you know, it's roughly five hundred million years ago. It's
the first time in the history and the fossil record
of Earth where we suddenly see this explosion and diversity
of animal body forms. You know, before this, there were animals,
(06:46):
and most of them had soft bodies and leave very
little records. But there were things like worms of various
kinds um But but then suddenly around the Cambrian period
you see all these different life forms emerging, and a
lot of the life worms have hard shells. This is
where you see the explosion of trilobytes. It sometimes thought
of as the Age of trialobytes, which are these scuttling
(07:08):
you know, almost like insect or crab like creatures that
would move along the bottom of ocean floors and have
these hard shells on their backs. But Anomala carrass or
Anomalocros appears to have been the top predator or one
of the top predators of the Cambrian period, which was
and it was this lobed swimming predator that grew up
to about six ft long. And when the fossils of
(07:31):
Anomala carrass were first discovered, paleontologists thought that they were
actually looking at two different species because it's a mostly
soft bodied organism, so its entire body usually doesn't get
preserved or doesn't get preserved very well. And since most
of their bodies are these soft parts that don't get fossilized.
(07:52):
Usually there were really only two parts of the body
that paleontologists kept finding. These two parts were, first of all,
these little pairs of shrimp looking things that they would
come in pairs, and they would kind of have these
curved shapes and they, I mean, they look like shrimp shells.
That's the best way to put it. And that's actually
where the name of Anomala carus comes from. H Anomala
(08:15):
carus means, you know, anomaly in cars means weird shrimp
or usual unusual shrimp. So you have these pairs of shrimps.
And then the other part that they would often find
would be these circular rings of hard looking plates. Now,
the shrimp looking things we actually feel we actually figured
out that these two different things actually were different parts
(08:36):
of the same organism, this Cambrian predator. And so the
shrimp looking things, it turned out, were curly we think,
feeding tentacles that were on the underside of the head.
So you'd see this thing swimming along. It's got the
eyes in the front and then sort of as a mouth,
it's got this like, you know, two lobed mustache of
shrimp tentacles that we think probably could kind of like
(08:58):
grab things and push them towards mouth parts, and then
the mouth parts would be the other part that gets fossilized,
that ring of plates, that's the mouth, that's sort of
halo of teeth like a tooth lined sphincter of death.
I mean, really, that's all a mouth is, is that
it is the it is the anti anus, it's the
other the other side of the organism. Yeah, just imagine
(09:20):
like like an anus that's just surrounded by a circle
of teeth that move inward. Right, And as we've discussed,
we had we did a whole at least one whole
episode on the evolution of the anus, and of course
you didn't always have two openings in organisms. You had
organisms that had to depend on one um orifice for
both functions, right, Which is amazing that that we're not
saying that's the case with a no, no, not at all.
(09:41):
We're just sort of demystifying the difference between the anus
and the mouth. Actually, I don't know for sure whether
an Almala cars had an anus or not, but I'm
pretty sure it had an anus. I had to get
had some form of venus, right, it had, I would
have to guess it had a one way digestive system, right.
I mean those we discussed in those episodes. There are
organisms that not or come to not have an anus.
(10:02):
You know, sometimes an organism in a certain phase of
its life no longer has to worry with defecating, or
has come to a situation where it cannot defecate anymore
and we'll just have to live with it. Yeah, certain
varieties of scorpion that have lost their anus because their
anus was on what like a third or fourth segment
of their tail, which they jettison to escape a predict.
(10:25):
It's a very sad scorpion story. But to the Anomala
carus mouth So from what I can tell, there's actually
still scientific disagreement about those mouth parts, about that sphincter
of death, about that ring of teeth pointing inward. So
it has long been assumed that Anomala Carus preyed on
trial bytes in one way or another. But how right?
(10:47):
Trial bytes have these really hard protective shells on their backs,
and some paleontologists thought, well, maybe the Anomala Carus would
eat them by attacking them right after mole thing when
their shells would have been soft, or maybe it would
attack them by like scooping them up with its little
feeding shrimps, the feeding tentacles, and then cracking or prying
(11:09):
off the shell somehow with those rings of plate like
teeth in the mouth. But I've read criticisms of this
model coming from the last decade or so, basically saying
that some current models of the Anomala carus mouth show
that it just would not have been strong enough to
crack through trialobyte shells, and maybe maybe it had to
feed on soft bodied organisms like jellyfish or worms instead.
(11:32):
I don't know if the idea of eating trio bytes
right after molting would get around this problem. It might
or it might not. Um So, did the Anomala cars
actually have this this crushing sphincter of deadly teeth or not?
I don't. I don't know if we know the answer
to this right now. This seems like a still open question.
I mean, obviously it did have these plates, it did
have these mouth parts, but we don't know how strong
(11:54):
its mouth was. Yeah, it is just so weird to
look at a representation of these because it's like it's
it's it's the sphincter of death. Like you said, but
it's also this feeling. It's that it's like a teeth.
It's like teeth made of broken glass, you know. Uh,
it's it's very strange to to look at. Yeah, it
was originally thought when people found the mouthparts in isolation,
(12:15):
so you just be this ring of plates, and they
didn't know it was the same organism as the pair
of weird shrimps. They I think originally thought this might
have been some part of of like weird old jellyfish.
All right, on that note, we're gonna take a quick break,
but when we come back, we will continue to explore,
to explore the weird wide world of teeth. So another thing, uh,
(12:40):
you know, we were saying, of course again that teeth
are not outside bones. As great as the song is,
they're not bones at all. They're these hardened structures. And
one question is where do teeth come from? Like what
is their evolutionary history as we know them? And the
current evidence indicates that the earliest known teeth evolved and
(13:02):
I guess this would be different than like the Cambrian
sort of mouth plates. This would be like teeth in
jawed animals, you know. Uh, the earliest known teeth evolved
not as adapted bones, because that's where you sort of think, right,
You think, well, you know you had some bone structures
and overtime those evolved into tooth like shapes. Sos of
the bones would be coming out of the jaw and
(13:23):
doing that. But actually it looks like the earliest teeth
evolved and not as adapted bones, but as adapted fish scales.
I was looking at a paper from Biology Letters in
by Martin Rooklin and Philip C. J. Donohue uh called
roman Dina and the Evolutionary Origin of Teeth basically finds
(13:44):
evidence from a species called roman Dina stalina, which is
an extinct plaqueoderm, and a plaque aderm is a type
of armor plated ancestral fish from more than four hundred
million years ago. One plaque aderm you've probably seen fossils
of before, is the awesome, the terrifying dunk Leosteus. This
is another superstar of a sort of a prehistoric creature
(14:08):
exhibits and museums. Yeah, you look up a dunkle osteous
cast or a dunkle Osteus skull. I mean, it's chomp city,
just unbelievable, and they got huge. Imagine this gigantic fish
with this chomp city head. It is definitely something out
of a movie. Oh yeah, well, like why we keep
making all these shark tech movies. They need to make
(14:28):
a movie about this. You can caught Dunkles like a monster.
It would be just named Dunkles, I like it, or
just dunks dunks dunks dunk dunks, dunk dunk dunk dunks.
I'm sorry, okay, but anyway. In the study X ray
analysis of fossil remains of this fish, again, this is
(14:49):
not dunkle Osteus. This is a different plaque. DRM Roman
Dina Stalina showed that scales evolved first the fish. Scales
evolved first, and then teeth evolved in the s line
of fish as an adapted type of scale cell along
a structure called the toothplate. And isn't it weird how
scales became so many different things like bird feathers evolutionarily
(15:14):
are adapted from ancestral reptile scales. Scales over time grew
into these these filaments and things that eventually became feathers.
But it's also thought that mammal fur and mammal hair
are adapted from scales of a common ancestor. Well, I
mean they've they've had time, right, That's that's one way
to look at it. And it seems like teeth or
(15:34):
another example here and these fish from four hundred million
years ago, it looks like teeth are coming out of
the adaptation of scale cells. Now as we uh, you know,
we're gonna go ahead and jump the time machine and go,
you know, go go go forward in time here, and
you know, it's easy to sort of fall into the
trap of thinking, okay, certainly, especially when we get into
mammal teeth, we're basically talking about the same scenario in
(15:57):
any given organism, right, I mean, yeah, you're your dog's
teeth don't look quite like human teeth, but there are
a lot of parallels. A cow's teeth don't look exactly
like a dog's teeth, but there are a lot of parallels.
You know. But then again, as we know from our
conversation with Katie, I mean, beaver teeth just chuck the
boat over, right, And another one that really chucks the
boat over are the are the teeth of elephants. And
(16:22):
they're extinct ken Because when when you look at an
elephant or a mastodon or a mammoth. First of all,
they are polyphiodonts rather than uh, diffidants, meaning that they're
psych They cycle through teeth their entire life rather than
depending on a mere two sets of teeth, So more
kind of like sharks to an extent. Basically like with
(16:45):
a human, you have you have two sets. You got
that first set, those baby teeth, and you get those
adults set, uh, the adult teeth, and you've got to
make that adult set last because those are the ones
that are supposed to take you to the grave. Uh.
With the elephant is a different scenario. Uh, there's still
a limited number of teeth. It's not just teeth forever,
but it's it's but it's also just a totally different
(17:07):
um like way that they grow. So you have long
ridges of teeth that move not from bottom to top.
You know, like when when you think of like a child,
a young child about their their their they lose their
baby teeth and then those adult teeth grow up out
of the jaw, like down down in the jaw and
then they load up to the yeah or or down
(17:27):
or you know, they come down and they come up
out of the jaw. Right. Well, it's great to see
those like cross sections of the jawbone at the baby
teeth still in there is just disgusting. It's like, how
could you ever look at a child the same way again?
But with elephants, you have long ridges of teeth that
move from back to front along upper and lower jaws lowly,
(17:48):
slowly wearing into a shelf at the front as the
roots are absorbed. So segments of the warranteeth in these
teeth are are oblong looking things too, so bay Basically,
they just move out of the back of the jaw
along to the front of the jaw and then they
break off in sections, sort of like a pez dispenser
(18:09):
or one way I like to think of it. It's
it's kind of like a toblarown bar. Each elephant tooth
or masted on tooth is a toblaroom bar that gets
worn down and as it reaches the front, segments of
that tobler room bar just fall out, and then in
the back of the jaw, new fresh teeth are growing out. Uh,
you know, growing out of roughly the same place you know,
(18:29):
where your wisdom teeth would be located. So this alone
is crazy. You know, most animals have vertically grown choppers.
But elephants and the kin of elephants essentially have six
sets of molars that that replace over time. So basically
the way the cycle goes is that, uh, they have
you know, one set of molars at birth, um, and
(18:51):
they keep those for about they lose those after two years.
Then they get a second set, lose those at six years,
and they get a third set, of fourth at a
fifth set in a sixth set, and then the and
in rare circumstances they will get a seventh set of
molars that come out of the back. But then that's
how you know you're dealing with like a real silver back.
Like well, it's actually one way that the scientists are
(19:13):
able to age the remains of elephants, Like you find
the remains of the jaw and you can look and
you can see you can learn a lot from it.
If it's a different type of elephant, can you know,
if it's mammoth or mastered on you can you can
study exactly what kind of foods it was eating based
on what those teeth look like. But then if it's
a particularly old elephant, um, well, look I'll say first
(19:34):
let's say it was a you know, an adult elephant
that wasn't too old, then you would see like the
warren teeth, and then you would see in the back
where fresh teeth were growing out. But then in the
an older adult elephant, it's on its last set the
hole in the back of the jaw, back on each
side of the jaw would be closed. It has just
(19:56):
become solid bone again because it is on its last
set of teeth, and those are the teeth that are
going to take it to the grave. I can't remember
if you already said this or the teeth. Is it
born with all these teeth already there or do the
teeth like generate over time they generate? Okay, yeah, they're
not already loaded back there. Um, so these are also
(20:16):
these are known as high it's known as hind molar progression,
also known as marching molars, which I particularly like that
one because there's this idea that they're marching from the
back of the jaw towards the front. And the main
other extent creatures that have these are the manatees, which
I'll get back to in a bit. And interestingly enough,
the manatees have them, but the doo gong, the relative
(20:38):
of the manatee does not. Kangaroo molars also apparently work
in this fashion. Um. But but then other creatures like you.
You might look to the rock higher ax, which is
the elephants rodent like relative. But even though it has
some elephant like qualities to its uh to, its teeth,
including two rodent like front teeth, are actually tiny tusts.
(21:00):
It doesn't have marching molars. Um. But I mentioned already
how the elephant molars are also elongated. Uh. They they
They're really crazy to look at because it looks like
fused teeth in a sense. It's it's like a big
long chunk of teeth and it's essentially it has enamel
loops for grinding plant matter. So that's what the elephants
(21:23):
using these for. It's just grinding top to molars against
bottom molars and uh and that is of course wearing
the teeth down as well, thus the need to continually
replace them. Right, the elephant is herbivore. It's gonna be
eating rough plant matters, so it needs sort of a
mortal mortar and pestle in the mouth to to mash
it up real good. Yeah. But again, when the when
the teeth are done that's it. And this is going
(21:44):
to lead in the wild especially, is going to lead
to malnutrition and or starvation. So I encourage everyone to
think about elephant teeth the next time you see an elephant.
Certainly if you have the chance to see one in
the wild, but if you see one in a zoo
or what have you, Like, it's teeth are or as
amazing as any other amazing quality of the elephant. Like, yes,
it's trunk is a is a is a marvel of
(22:07):
the natural world. But also it's teeth are just so
super weird. Yeah, this high capacity magazine of molars, Yeah
it is. It's like a magazine a pet dispenser of
teeth um And it's just it's just not what you
come to expect from teeth in general. Like you know,
even even a shark, right, it continually grows those teeth,
but they're growing out of sort of flipping out of
(22:29):
the jaw top and bottom. But the the elephant has
a different system entirely. Now, what is the deal with
tusks since we're talking about elephants, Because we talked with
Katie and we've talked on the show before about the
idea of narwhal tusks. How the narwhal tusks are not
like modified bones. They are teeth, you know, their teeth
jutting up just straight forward, straight out of the mouth. Yeah,
(22:52):
they're they're modified incisors. Is the deal? Oh even an elephants?
Yeah yeah, so um so yeah, it's it's easy to
sort of look at tusks and even if you know
they're not horns, you kind of like think of them,
you kind of categorize them in the same in the
same area. So, yeah, elephants are are weird wonderful creatures,
(23:14):
uh that we've we've been looking at them so long.
There's such a famous animal we can you know, they're
in our story books as as as children, they're in
our animated films. You kind of forget how weirdly alien
they are in many many regards. Is it weird that
I'm just imagining now what it would be like to
get bitten by an elephant? I don't know. I keep
thinking trying to imagine what that would be like to
(23:37):
have um marching molars, to have that kind of dental situation.
And granted we wouldn't because we do not need to
have that for our diet, but if we did, like,
can you imagine your teeth growing in from the back
and then they like breaking off in the front. Also
their soft foods. Yeah, all right, let's take one more
break and we come back. I want to talk just
(23:58):
a little bit about an tee teeth. Okay, alright, we're back.
So we've talked about manatees on the show before. Um mana,
teach me something, Robert. Well. Manatees are, of course marine mammals,
and they are Serenians. Uh, they have a few living
kid that will get to oh SERENI. So are they
named after the sirens? Exactly? Yeah, tying into the whole, uh,
(24:22):
you know, mistaking manatees for mermaid thing. Now, their closest
living relatives are the elephants, and they're kind of like
the elephants of the sea in some respects, you know,
drifting through the waters feasting on vegetation. There are three
extant varieties of manatees. There's the Amazonian manateee, the West
Indian manateee, and the West African manateee, and all of
them have marching molars, much like the elephants. But then
(24:46):
I was reading around a little bit of this about
this and there's a. There's another variety of Serenian that
went extinct in the eighteen hundreds, and this was Stellar's
sea cow. Now it apparently, uh, this was a Serenian
that already had a rather narrow habitat. It was already
like you could make the argument, I think that was
already kind of endangered before human activity really put the
(25:10):
nail in the casket here. But it actually didn't have
true teeth. Uh. It had instead what has been described
as broad horny pads that it used to chew the
soft parts of kelp, which made up most of its diet.
And this leads us to the other existing Serenian, and
(25:31):
that's the Eastern Hemisphere hemispheres do Gong, which looks very
similar to a manity, but it has a shorter snout
which kind of you often see it in pictures. It
looks like a vacuum cleaner because it's essentially what it is.
It's cleaning, it's it's eating off the bottom. Uh. And
it also has a flute tail that looks much like
a whale um. But then you really have to think
(25:53):
about its teeth. So it has no marching molars. It
does not have the marching molars of a manatee. Uh.
They also have incisors, which are essentially a little tusks,
which manatees are lacking. But the thing about doo gongs
is that they also have horny pads in their mouths
for chewing, and they are more important than their actual teeth.
(26:14):
The cheek teeth are almost a non functioning and um
and are not very tough to begin with. So I
was reading a few different papers about them from J. M.
Lanyon and G. D. Sanson in the Journal of Zoology,
and they point out that regarding doo gongs, quote, the
soft mouth parts of the doo gong are highly modified
so that the entire oral cavity functions to crush low
(26:38):
fiber sea grasses. Thus, the doo gong has developed an
efficient method of food ingestion, and mastication that is suited
to put processing large quantities of soft sea grass during
short dive times. The potential cost to the doo gong
and having lost its hard dental surfaces is that it
has become restricted to a low fiber diet. So this
(26:59):
is interesting. The do going eats mostly seagrass, while manatees,
who again have these more robust teeth and have these
marching molars. They eat roughly sixty different varieties of fresh
and saltwater plants. Um. I've read that the difference in
the snout also means that manatees can sort of reach
out a little bit because they just have a more
(27:19):
vary diet. UM. Manatees have also been observed to occasionally
eat fish from nets. So, you know, we generally think
of them as herbivores, and you know, for the most
part they are, but it seems like if they have
the chance to eat a fish out of a net, uh,
they will do so. And so we have another example
of opportunistic carnivory. Yeah. Meanwhile, the doo gong is apparently
(27:42):
not engaging in this in this behavior that we know of,
So that would mean that the doo gong is really
the only true marine herbivore mammal in the world, the
only marine herbivore mammal. Wow. So I guess I'm trying
to think of counter examples. What I can't because you
know what I it is. I think of a lot
of like filter feeding whales as herbivores, and they're not.
(28:06):
They're eating you know, the microscopic animals, their carnivores. Yeah,
we we we we. We don't think of them as
such because they're not trying to eat us. I mean, uh,
you know whale myths aside, the animals they eat are
very small. It's like, are you a carnivore if you
only popcorn shrimp? Some people might not think so, but
(28:26):
but I love I love this as a kind of
a closing example to look at this as the you know,
the doo gong, the manatee and Stellar sea cow as
being examples just within the Sirenian world of how teeth
change with diet and how you can have kind of
you know, rapidly different like the idea you have marching
molars in the manatee and Stellar's sea cow didn't have
(28:47):
teeth at all, and then the doo gong is kind
of in this place in between the two. I just
find that fascinating. And and again, any any chance I
have to explain how cool manatees are, I've got to
take it because a man of teas are just amazing
creatures and if you have the chance to see some
in the wild, you should definitely do so. I got
to see some just the other week. I was down
(29:08):
at downe in Florida at what is it Wakula or
I've also heard Waccola Springs. Got to see multiple manatees
and baby manatees. It was breath tick. Now, the same
way that the manatee and the dugong may have inspired
the Legends of the Mermaid, did the manatees of Wakula
Springs inspire the Creature of the Black Lagoon? The Creature
(29:29):
from the Blackgan They did film some some scenes there um,
mainly like the you know, just the swamp footage. Is
the stuff that they filmed there at the springs. Yeah,
but they weren't you telling me, like they can't do
licensed stuff, like they can't actually have creature materials. They
were at least I think maybe maybe they're not willing,
(29:49):
you know, they're not willing or able to pay out
for the licensing phase. I'm not privy to the details,
So I just know that a few years ago they
had some creature memorabilia there and now there's not any.
But they were showing in Creature from the Black Lagoon
one evening in the lobby and so that was kind
of cool to have gone out on the swamp during
the day and then at night, like to see this
old movie and see these scenes from it, and it's like, oh, well,
(30:10):
there you go. I went by there in a boat
just several hours ago. Uh. I think we've established on
the show that we're firmly on the side of the
creature in the country from the Black Lagoon, and that
the heroes are awful. Yes, there's the alleged scientists in
that in that show are are are awful. There's a
life form shoot it. Luckily those are not the scientists
(30:30):
that are involved in taking care of manatees today. Hey, folks,
if we suddenly sound different, we just jumped into another
space and time. So here we are again. I just
wanted to close out with another quick grab bag of
teeth related stuff that I couldn't stop thinking about. Robert.
You remember at the end of our episode with Katie
where goose teeth came up, right, Yeah, so of course, Um,
(30:55):
geese can sometimes I didn't mean to demonize geese by
the way when talking to Katie, but geese can be
surprisingly aggressive. I think we don't usually worry about birds
getting territorial and attacking us, but if you get too
close to a goose nest, you're you're asking for trouble, right, Yeah,
they're They're more fierce than we sometimes realize. They're also
sott smarter than we sometimes realize. Like there's certainly no
(31:17):
no Corvid's, but there have been some interesting studies that
have put them to the test with the various tasks
and they can actually perform well. Yeah, and so I
think in that episode with Katie we actually talked a
little bit about goose teeth. Now, goose don't actually have
biological teeth with denton and enamel. But if you have
not seen an image of the serrated edges of death
(31:40):
writhing like the dead lights inside a goose mouth, you
have got to go search for this right now. It's
an image that you must see. They're a bunch of
them all over the internet. Uh, Robert, I added one
to your notes, But oh, you might not have your
notes right in front of you, do you. I do not. Well,
it's just got knives in the mouth basically along the
edge of the so basically like the tongue and the
(32:01):
beak are both covered in these fierce jagged sawtooth spines
around the lateral edges and um. The most recent evidence
indicates that existing birds to send from ancestors that lost
their teeth in a multi stage process that took place
roughly between I think about one D sixteen one hundred
one million years ago. Um. So, if you're out there
(32:24):
listener asking, wait a minute, lost their teeth? Birds lost
their teeth. Yes, because, as we've talked about plenty of times,
birds evolve from dinosaurs that definitely had teeth. Arcosaurs archaeopterics
had teeth, and it appears that this period, around a
hundred million years ago, they acquired gene mutations that changed
(32:44):
a couple of things. They change jaw development to stop
the development of teeth as as they matured, and to
cause the development of beaks instead. And one consequence of
this knowledge is that if we can suppress the molecular
their pathways for the gene that suppresses the growth of
teeth in birds, you know, the gene that turns off
(33:06):
tooth development, you turn off the turnoff there, we can
sort of create birds with teeth again. And in fact,
a group of researchers actually did this and and publish
their findings in Current Biology way back in two thousand six.
You've probably I bet this has come up on the
show before at least maybe a while ago, right, was
the transforming of chickens into tiny dinosaurs. Yeah, they already
(33:27):
are tiny dinosaurs they respect, but they are very much tyrannosaurss.
But in this case, I think the resemblance is slightly
less to the therapod dinosaurs and more to crocodilians, because
when they made a couple of genetic tweaks or epigenetic
tweaks to embryonic chickens, the embryos grew teeth that resembled
the conical teeth you would see in the mouth of
(33:49):
an alligator or crocodile, indicating that these were probably pretty
similar to the teeth of ancestral birds more than a
hundred million years ago. So the goose does not have
true teeth. But I wonder if you could crisper up
like a really awful fanged crocodile goose from the deep past.
I bet that could be done, though I don't know
if it would survive development with the mutation. Yeah, I'm
(34:12):
not sure about that, but but I do love this
example because it kind of goes back to what we're
exploring with the Syreneans, that if if teeth are no
longer needed, if they are no longer the best means
of masticating food or or or helping to you know,
to aid in the ingestion of food. They're not going
to stay around forever. I mean, they're they're they're like
anything in the body, they're they're a costly investment. Yeah.
(34:35):
This is one of the things that that we often
fail to remember when we think about evolution without taking
like energy and development concerns in mind, we think of
evolution primarily as a process of addition. But what episode
was it just recently on the show where we talked
about a lot of subtraction evolution. Oh, I think it
was in the one about the phrase survival of the fittest. Yeah,
(34:56):
and what that it tends to imply to people who
you know, uh, if if you haven't thought about it
all that deeply, one thing is that you get this
sort of vague impression that maybe it always works by
like adding new powers and not by just subtracting things
that are useless expenses. Right. And and we also, yeah,
I think discussed as we've discussed before, this whole idea
of something devolving. You know, it's like no evolution. Uh,
(35:19):
you can go in either direction. So if you say
your views on the topic, I've evolved, it's not necessarily
a good thing. Right. It's like if you're your HR
department tells you that your benefits are evolving, not necessarily
a good thing, right, Um, ask more questions to find
out exactly what's going on. Well, yeah, but I mean, yeah,
there is no devolving. It's all evolving. So some evolving
(35:39):
and you might like, and some evolving you might not like.
Who knows. I mean, maybe we could evolve brains that
just feel excruciating pain every moment of the day for
no good reason at all. It just happens to work
that way. Um. But another and interesting evolutionary question is
why did birds lose their teeth? And this is an
unsolved probably blow. We don't have a good answer of
(36:02):
exactly what the evolutionary pressure driving the switch from teeth
to beaks was. Uh the answer. So one historical hypothesis
I've read about is that it helped birds lighten their
bodies to optimize flight dynamics. But I've also read opinions
that's not a very good explanation because you know, we
see tons of flying animals with teeth. Teeth don't necessarily
(36:24):
weigh a whole lot that that seems like that's probably
not a very good candidate for explaining it. So we
don't fully know the answer. I mean, one would assume
it would you know, would come down to diet one
way or another. But yeah, you would think so. I mean,
and one thing you can look at is the different
kinds of beaks that existing birds have. I mean, beak
diversity is is enormous across the aviens that used the
(36:45):
beaks for all kinds of different things. We should come
back and do an episode on beaks, just on beaks, yes,
And we can also talk about the movie Beaks, which
is maybe the most painful bad horror movie I've ever watched. Yeah,
it's a rip off of Alfred Hitchcock's The Birds. Uh,
And so it's just a about birds attacking people. That
that's That's pretty much all you need to know, except
(37:05):
it just happens to have this distinction. And you know me,
I'm somebody who watches tons of bad horror movies. It's
probably the most excruciating one I ever tried to finish.
So that would you say this is worse than bird Dimmick? Oh? Yeah, no,
burd Dimmick is a joy by comparison. I'm not saying
it's I'm not saying it's worse from a filmmaking skill
point of view, but Burdemic was much more enjoyable and
(37:27):
it was easy to make it through the runtime. Beaks
is a film that one of the things, one of
the things I think about it is that it has
a soundtrack with like a really uh, just grading synthesizer
score that has songs. They're not really songs. It's like
a single very high pitch synthesizer note held down for
(37:48):
minutes at a time that starts to just wear on
you as if you you think you have something wrong
with your ears or your brain. It's like a it's
a soundtrack that mimics tended us or something, and it's
just really glee to watch. Anyway, we got sidetracked, but yes,
I think we should come back to an episode on Beaks,
because yeah, beak diversity is is amazing, and so I
(38:08):
guess that brings us back to the actual goose mouth,
the serrated edges inside there along the tongue, along the
beak edges. If those aren't teeth, what's going on there
with those little jagged spines. Uh So, the serrated edges
in a modern bird's beak that that's made of stuff
called tomium. These are these little spiny cutting edges that
can be used kind of like teeth. But from what
(38:29):
I've read, they're they're not usually for what we would
think of as chewing. They're more for grabbing hold of
food like plant matter or like live prey and either
cutting it or gripping it firmly so that the bird
can like keep hold of it and tear it away
from anything it's attached to. Uh So, you can see
this for like, uh, you know, anything that would be
eating like plant matter and trying to tear it away
(38:51):
from whatever it's like the stem or something. Or you
can see it for grabbing hold of a fish and
making sure it doesn't get away. It's just generally useful
for like hooking stuff into the mouth, and of course
and for cutting um and for for a bonus in
bird relatives that also lost their teeth. If you haven't
looked at this, you should check out the mouths of
(39:12):
leather back sea turtles. Have you seen this one, Robert,
I don't know that I have seen leather back sea
turtles before but in the wild. But but I didn't
get a good look in their mouth. Well, actually, I
think with Katie we were talking about some viral images
of animal mouths that you think like, Okay, that's got
to be photoshopped, but actually it turns out to be
totally real. Leather back sea turtle mouths are like this.
(39:35):
They there's some of the photos of them make the
rounds on the internet, and it looks like a made
up monster mouth that somebody is passing off as a fake,
real animal. It's totally real. It looks like a vivid
you know, somebody took the bad acid nightmare of It's
hard to explain because these are the ones that they
look they're swirly looking kind of yeah, they don't so
(39:56):
it's not rows of teeth again, their turtles, they don't
have teeth, but they are these thorns. It's like a
thorn forest. Imagine a sort of fractal sarlac on steroids
with even more teeth, this forest of thorns going down
the esophagus. And what this actually is, it's not teeth,
(40:16):
but it's a covering of cartilage based prongs that are
known as esophageal pappally which what they do is they
help the leather back sea turtle hold onto its prey,
which primarily consists of jellyfish. So imagine you're trying to
eat a jellyfish, this organism that's kind of squishy and
mostly made of water in the water. Yeah, you might
(40:38):
imagine that it's kind of hard to like get that
in the mouth and keep it from slipping out of
the mouth, especially if you're trying to like eject seawater
back out of the mouth while you're eating it and
then to shove it along down through the esophagus. And
apparently the sea turtles have these long digestive tracks that
can hold a whole bunch of jellyfish in them all
(40:58):
at the same time while they're sort of waiting to
be processed by the stomach. So yeah, the thorn forest
in the mouth is mainly for grabbing hold of these
gelatinous masses of prey and holding them in place so
that they don't slip away. But again, another example of
it's not teeth, but they they fulfill some of the
purposes that we associate with teeth. Yeah, So that's that's interesting.
(41:19):
If if teeth did not exist, they would evolve necessary
to invent. All right, Well this has been fun, Robert, Yeah, absolutely,
uh and you know, we again, we only covered so
many teeth there. There are other amazing examples out there,
and if anyone listening can think of some really good ones,
you know, uh, let us know, because we could always
come back and do another sack full of teeth on
(41:41):
the show. And I would love to do beaks. I was.
I was up close and personal with a two can
the other day and um, you know, it's just always
amazing to look at a beak like that, and uh, yeah,
I'd love to go through the world of beaks. In
the meantime, if you want to check out more episodes
of Stuff to Blow your Mind, you can go to
Stuff to Blow your Mind dot com. That's the mother ship.
That's where we'll find them. You'll find various links there
(42:02):
as well. Uh and hey, if you want to support
the show, about the best thing you can do is
to rate and review us wherever we have the power
to do so, and make sure that you have subscribed
to not only Stuff to Blow Your Mind but also
our other show Invention. Huge thanks as always to our
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you would like to get in touch with us with
feedback on this episode or any other, to suggest a
(42:24):
topic for the future, or just to say hello, you
can email us at contact at stuff to Blow your
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production of iHeart Radio's How Stuff Works. For more podcasts
(42:44):
from my heart Radio, visit the iHeart Radio app, Apple Podcasts,
or wherever you listen to your favorite shows. Blows Joined
Three Boys, proper posers, Priss
Hey, welcome to Stuff to Blow Your Mind. My name
is Robert Lamb and I'm Joe McCormick, and it's Saturday.
Time to go into the vault for an older episode
of the show. This one originally aired on July nineteen.
It's about teeth. I'm ready to bite. Yeah, well, let's
bite right in and figure out what we're biting with.
(00:27):
Welcome to Stuff to Blow Your Mind, a production of
I Heart Radios How to Work. Hey you, welcome to
Stuff to Blow Your Mind. My name is Robert Lamb
and I'm Joe McCormick. And if you've been listening to show,
you know we just had our friend Katie Golden from
Creature feature on. I think it was the episode right
(00:48):
before this one where we talked about teeth with with
Katie and that was a lot of fun. But Robert,
I couldn't stop thinking about teeth. Oh yeah, I mean,
teeth are weird. Teeth are wonderful and strange and grotesque.
I was actually just at the dentist yesterday for a checkup,
and I just kept thinking about just how weird it
(01:09):
is that that I just regularly go to this place
and pay another human being to reach into my mouth
with special instruments and clean my weird bone like jaw protutions.
The outside bones outside bones. Never forget your teeth are
outside bones. Their bones that you wash. Oh this this
is from Kimmy Schmidt. Right, Yeah, Titus Syndromedon sings that song.
(01:29):
I think he's auditioning for like a chewing gum commercial,
But he's actually wrong, I'm sorry to say, despite how
much I love that moment from the show, teeth are
not outside bones. They are not bones at all. They're
totally different thing. We can explain that in a minute.
But yeah, yeah, I mean, well, let's go ahead and
get into it. So, yeah, our teeth are bone like
in many respects. Uh yeah, but they are not bones.
(01:52):
So just for an example, bones are composed of calcium, phosphorus, sodium,
and other minerals. Uh and but mostly it's the protein
call legend that forms the living growing collagen framework in bones.
Bones have impressive regenerative powers. You break a bone, it
can even like a really vicious break of a bone,
and it can heal back. Also, bone marrow produces red
(02:16):
and white blood cells. Teeth do not have bone marrow. Instead,
they have dental pulp. So teeth, on the other hand,
are you know, they're composed of calcium, phosphorus and other minerals.
They're harder than any bone that we have in the body. Yeah,
but they also lack the regenerative powers of bones. So
if you crack or break a tooth, you're gonna need
at least a root canal, if not a total extraction.
(02:38):
That is kind of strange. That seems I wonder what
the evolutionary reason for that is. I would expect, you know,
there would be a strong pressure on the ability to
regenerate teeth. Well, it depends on how this really gets
into like the bigger questions of of biological mortality, right,
like what do you need your teeth for? How long
(03:00):
are you going to be a viable organism? How long
do you need to live, you know, in order to
accomplish your genetic mission of you know, reproduction, uh and
so forth, and and you know, the evolution isn't really
concerned with long term dental health beyond that point. Well maybe, yeah,
maybe we don't need teeth because um, well, for one thing,
we're not like sharks, right, We're not just like biting
(03:22):
indiscriminately into whole organisms and you know, cross bones and
stuff like that. We we tend to if we're eating
an animal, we kill it before we start biting into it.
Uh so you know, you you would be able to
have the time to seek out the soft parts to
bite into, and so you're not using your teeth in
a kind of like violent, fast moving kind of way
(03:45):
like a lot of other organisms would. Yeah, and and
and it really drives home one of the one of
the key and I guess kind of obvious things that
we're gonna we're gonna touch on here and there is
that as as organisms evolve, their teeth are going to
change to meet the demands of their diet. And if
if you're if you do not need your robust teeth
of old anymore, well, those those teeth are going to change,
(04:08):
and you're gonna end up with a dental model that
is going to be more in keeping with what you're
actually going to use your choppers for. It's funny, you
could think of teeth in a way as a form
of convergent evolution. So like the same way that you
see uh, wings evolving independently in different lines of animals.
It's not that everything on Earth that has wings evolved
(04:32):
from a common winged ancestor. So wings arose in one
case in insects, and then they separately arose in you know, mammals,
They rose in bats and stuff, and then they separately
arose in the dinosaurs that became birds, and then also
in the other the flying reptiles, right, which are not dinosaurs,
but also independently evolved wings. Uh. So, so you see
(04:55):
winged flight evolving over and over despite the fact that
all these organisms don't come from wings of a common
ancestor organism that I mean, I guess if you go
far back enough, they all do have a common ancestor,
but it didn't have wings. Um. And you can see
a kind of similar thing in different things we call
teeth that you know, lots of organisms have an opening
(05:16):
of the elementary tract. They've got a mouth of some
kind or another, and it it just often happens to
be the case that organisms evolve a need to mash
and crush and cut things that are going into the
front of the elementary tract. And that's how you get
these different evolutions of things that are like teeth. Uh.
And there there are a lot of different things you
(05:37):
might call teeth, and not all are evolutionarily related to
the calcified structures we see in animals like ourselves. In fact,
one great example of a whole different kind of of
twothworld that I was thinking about just recently is uh.
It reminds me of this controversy over the mouth of
a Cambrian predator that I have been calling Anomala carus
(06:01):
or Anomala carress. I just found out that some people
pronounce it anomalachrus. And now now I feel like my
whole world has been turned on its head. I don't
know which to say, but I think I'm gonna keep
saying Anomala caress even if that's wrong, for the sake
of consistency. This is this is basically, if you've ever
been to a natural history museum, you've probably seen a
representation of this. Uh, this this prehistoric fish. Yeah, I mean,
(06:25):
well not a fish, well fish like organism and the
this long predating fish. So the Cambrian period, of course,
you know, it's roughly five hundred million years ago. It's
the first time in the history and the fossil record
of Earth where we suddenly see this explosion and diversity
of animal body forms. You know, before this, there were animals,
(06:46):
and most of them had soft bodies and leave very
little records. But there were things like worms of various
kinds um But but then suddenly around the Cambrian period
you see all these different life forms emerging, and a
lot of the life worms have hard shells. This is
where you see the explosion of trilobytes. It sometimes thought
of as the Age of trialobytes, which are these scuttling
(07:08):
you know, almost like insect or crab like creatures that
would move along the bottom of ocean floors and have
these hard shells on their backs. But Anomala carrass or
Anomalocros appears to have been the top predator or one
of the top predators of the Cambrian period, which was
and it was this lobed swimming predator that grew up
to about six ft long. And when the fossils of
(07:31):
Anomala carrass were first discovered, paleontologists thought that they were
actually looking at two different species because it's a mostly
soft bodied organism, so its entire body usually doesn't get
preserved or doesn't get preserved very well. And since most
of their bodies are these soft parts that don't get fossilized.
(07:52):
Usually there were really only two parts of the body
that paleontologists kept finding. These two parts were, first of all,
these little pairs of shrimp looking things that they would
come in pairs, and they would kind of have these
curved shapes and they, I mean, they look like shrimp shells.
That's the best way to put it. And that's actually
where the name of Anomala carus comes from. H Anomala
(08:15):
carus means, you know, anomaly in cars means weird shrimp
or usual unusual shrimp. So you have these pairs of shrimps.
And then the other part that they would often find
would be these circular rings of hard looking plates. Now,
the shrimp looking things we actually feel we actually figured
out that these two different things actually were different parts
(08:36):
of the same organism, this Cambrian predator. And so the
shrimp looking things, it turned out, were curly we think,
feeding tentacles that were on the underside of the head.
So you'd see this thing swimming along. It's got the
eyes in the front and then sort of as a mouth,
it's got this like, you know, two lobed mustache of
shrimp tentacles that we think probably could kind of like
(08:58):
grab things and push them towards mouth parts, and then
the mouth parts would be the other part that gets fossilized,
that ring of plates, that's the mouth, that's sort of
halo of teeth like a tooth lined sphincter of death.
I mean, really, that's all a mouth is, is that
it is the it is the anti anus, it's the
other the other side of the organism. Yeah, just imagine
(09:20):
like like an anus that's just surrounded by a circle
of teeth that move inward. Right, And as we've discussed,
we had we did a whole at least one whole
episode on the evolution of the anus, and of course
you didn't always have two openings in organisms. You had
organisms that had to depend on one um orifice for
both functions, right, Which is amazing that that we're not
saying that's the case with a no, no, not at all.
(09:41):
We're just sort of demystifying the difference between the anus
and the mouth. Actually, I don't know for sure whether
an Almala cars had an anus or not, but I'm
pretty sure it had an anus. I had to get
had some form of venus, right, it had, I would
have to guess it had a one way digestive system, right.
I mean those we discussed in those episodes. There are
organisms that not or come to not have an anus.
(10:02):
You know, sometimes an organism in a certain phase of
its life no longer has to worry with defecating, or
has come to a situation where it cannot defecate anymore
and we'll just have to live with it. Yeah, certain
varieties of scorpion that have lost their anus because their
anus was on what like a third or fourth segment
of their tail, which they jettison to escape a predict.
(10:25):
It's a very sad scorpion story. But to the Anomala
carus mouth So from what I can tell, there's actually
still scientific disagreement about those mouth parts, about that sphincter
of death, about that ring of teeth pointing inward. So
it has long been assumed that Anomala Carus preyed on
trial bytes in one way or another. But how right?
(10:47):
Trial bytes have these really hard protective shells on their backs,
and some paleontologists thought, well, maybe the Anomala Carus would
eat them by attacking them right after mole thing when
their shells would have been soft, or maybe it would
attack them by like scooping them up with its little
feeding shrimps, the feeding tentacles, and then cracking or prying
(11:09):
off the shell somehow with those rings of plate like
teeth in the mouth. But I've read criticisms of this
model coming from the last decade or so, basically saying
that some current models of the Anomala carus mouth show
that it just would not have been strong enough to
crack through trialobyte shells, and maybe maybe it had to
feed on soft bodied organisms like jellyfish or worms instead.
(11:32):
I don't know if the idea of eating trio bytes
right after molting would get around this problem. It might
or it might not. Um So, did the Anomala cars
actually have this this crushing sphincter of deadly teeth or not?
I don't. I don't know if we know the answer
to this right now. This seems like a still open question.
I mean, obviously it did have these plates, it did
have these mouth parts, but we don't know how strong
(11:54):
its mouth was. Yeah, it is just so weird to
look at a representation of these because it's like it's
it's it's the sphincter of death. Like you said, but
it's also this feeling. It's that it's like a teeth.
It's like teeth made of broken glass, you know. Uh,
it's it's very strange to to look at. Yeah, it
was originally thought when people found the mouthparts in isolation,
(12:15):
so you just be this ring of plates, and they
didn't know it was the same organism as the pair
of weird shrimps. They I think originally thought this might
have been some part of of like weird old jellyfish.
All right, on that note, we're gonna take a quick break,
but when we come back, we will continue to explore,
to explore the weird wide world of teeth. So another thing, uh,
(12:40):
you know, we were saying, of course again that teeth
are not outside bones. As great as the song is,
they're not bones at all. They're these hardened structures. And
one question is where do teeth come from? Like what
is their evolutionary history as we know them? And the
current evidence indicates that the earliest known teeth evolved and
(13:02):
I guess this would be different than like the Cambrian
sort of mouth plates. This would be like teeth in
jawed animals, you know. Uh, the earliest known teeth evolved
not as adapted bones, because that's where you sort of think, right,
You think, well, you know you had some bone structures
and overtime those evolved into tooth like shapes. Sos of
the bones would be coming out of the jaw and
(13:23):
doing that. But actually it looks like the earliest teeth
evolved and not as adapted bones, but as adapted fish scales.
I was looking at a paper from Biology Letters in
by Martin Rooklin and Philip C. J. Donohue uh called
roman Dina and the Evolutionary Origin of Teeth basically finds
(13:44):
evidence from a species called roman Dina stalina, which is
an extinct plaqueoderm, and a plaque aderm is a type
of armor plated ancestral fish from more than four hundred
million years ago. One plaque aderm you've probably seen fossils
of before, is the awesome, the terrifying dunk Leosteus. This
is another superstar of a sort of a prehistoric creature
(14:08):
exhibits and museums. Yeah, you look up a dunkle osteous
cast or a dunkle Osteus skull. I mean, it's chomp city,
just unbelievable, and they got huge. Imagine this gigantic fish
with this chomp city head. It is definitely something out
of a movie. Oh yeah, well, like why we keep
making all these shark tech movies. They need to make
(14:28):
a movie about this. You can caught Dunkles like a monster.
It would be just named Dunkles, I like it, or
just dunks dunks dunks dunk dunks, dunk dunk dunk dunks.
I'm sorry, okay, but anyway. In the study X ray
analysis of fossil remains of this fish, again, this is
(14:49):
not dunkle Osteus. This is a different plaque. DRM Roman
Dina Stalina showed that scales evolved first the fish. Scales
evolved first, and then teeth evolved in the s line
of fish as an adapted type of scale cell along
a structure called the toothplate. And isn't it weird how
scales became so many different things like bird feathers evolutionarily
(15:14):
are adapted from ancestral reptile scales. Scales over time grew
into these these filaments and things that eventually became feathers.
But it's also thought that mammal fur and mammal hair
are adapted from scales of a common ancestor. Well, I
mean they've they've had time, right, That's that's one way
to look at it. And it seems like teeth or
(15:34):
another example here and these fish from four hundred million
years ago, it looks like teeth are coming out of
the adaptation of scale cells. Now as we uh, you know,
we're gonna go ahead and jump the time machine and go,
you know, go go go forward in time here, and
you know, it's easy to sort of fall into the
trap of thinking, okay, certainly, especially when we get into
mammal teeth, we're basically talking about the same scenario in
(15:57):
any given organism, right, I mean, yeah, you're your dog's
teeth don't look quite like human teeth, but there are
a lot of parallels. A cow's teeth don't look exactly
like a dog's teeth, but there are a lot of parallels.
You know. But then again, as we know from our
conversation with Katie, I mean, beaver teeth just chuck the
boat over, right, And another one that really chucks the
boat over are the are the teeth of elephants. And
(16:22):
they're extinct ken Because when when you look at an
elephant or a mastodon or a mammoth. First of all,
they are polyphiodonts rather than uh, diffidants, meaning that they're
psych They cycle through teeth their entire life rather than
depending on a mere two sets of teeth, So more
kind of like sharks to an extent. Basically like with
(16:45):
a human, you have you have two sets. You got
that first set, those baby teeth, and you get those
adults set, uh, the adult teeth, and you've got to
make that adult set last because those are the ones
that are supposed to take you to the grave. Uh.
With the elephant is a different scenario. Uh, there's still
a limited number of teeth. It's not just teeth forever,
but it's it's but it's also just a totally different
(17:07):
um like way that they grow. So you have long
ridges of teeth that move not from bottom to top.
You know, like when when you think of like a child,
a young child about their their their they lose their
baby teeth and then those adult teeth grow up out
of the jaw, like down down in the jaw and
then they load up to the yeah or or down
(17:27):
or you know, they come down and they come up
out of the jaw. Right. Well, it's great to see
those like cross sections of the jawbone at the baby
teeth still in there is just disgusting. It's like, how
could you ever look at a child the same way again?
But with elephants, you have long ridges of teeth that
move from back to front along upper and lower jaws lowly,
(17:48):
slowly wearing into a shelf at the front as the
roots are absorbed. So segments of the warranteeth in these
teeth are are oblong looking things too, so bay Basically,
they just move out of the back of the jaw
along to the front of the jaw and then they
break off in sections, sort of like a pez dispenser
(18:09):
or one way I like to think of it. It's
it's kind of like a toblarown bar. Each elephant tooth
or masted on tooth is a toblaroom bar that gets
worn down and as it reaches the front, segments of
that tobler room bar just fall out, and then in
the back of the jaw, new fresh teeth are growing out. Uh,
you know, growing out of roughly the same place you know,
(18:29):
where your wisdom teeth would be located. So this alone
is crazy. You know, most animals have vertically grown choppers.
But elephants and the kin of elephants essentially have six
sets of molars that that replace over time. So basically
the way the cycle goes is that, uh, they have
you know, one set of molars at birth, um, and
(18:51):
they keep those for about they lose those after two years.
Then they get a second set, lose those at six years,
and they get a third set, of fourth at a
fifth set in a sixth set, and then the and
in rare circumstances they will get a seventh set of
molars that come out of the back. But then that's
how you know you're dealing with like a real silver back.
Like well, it's actually one way that the scientists are
(19:13):
able to age the remains of elephants, Like you find
the remains of the jaw and you can look and
you can see you can learn a lot from it.
If it's a different type of elephant, can you know,
if it's mammoth or mastered on you can you can
study exactly what kind of foods it was eating based
on what those teeth look like. But then if it's
a particularly old elephant, um, well, look I'll say first
(19:34):
let's say it was a you know, an adult elephant
that wasn't too old, then you would see like the
warren teeth, and then you would see in the back
where fresh teeth were growing out. But then in the
an older adult elephant, it's on its last set the
hole in the back of the jaw, back on each
side of the jaw would be closed. It has just
(19:56):
become solid bone again because it is on its last
set of teeth, and those are the teeth that are
going to take it to the grave. I can't remember
if you already said this or the teeth. Is it
born with all these teeth already there or do the
teeth like generate over time they generate? Okay, yeah, they're
not already loaded back there. Um, so these are also
(20:16):
these are known as high it's known as hind molar progression,
also known as marching molars, which I particularly like that
one because there's this idea that they're marching from the
back of the jaw towards the front. And the main
other extent creatures that have these are the manatees, which
I'll get back to in a bit. And interestingly enough,
the manatees have them, but the doo gong, the relative
(20:38):
of the manatee does not. Kangaroo molars also apparently work
in this fashion. Um. But but then other creatures like you.
You might look to the rock higher ax, which is
the elephants rodent like relative. But even though it has
some elephant like qualities to its uh to, its teeth,
including two rodent like front teeth, are actually tiny tusts.
(21:00):
It doesn't have marching molars. Um. But I mentioned already
how the elephant molars are also elongated. Uh. They they
They're really crazy to look at because it looks like
fused teeth in a sense. It's it's like a big
long chunk of teeth and it's essentially it has enamel
loops for grinding plant matter. So that's what the elephants
(21:23):
using these for. It's just grinding top to molars against
bottom molars and uh and that is of course wearing
the teeth down as well, thus the need to continually
replace them. Right, the elephant is herbivore. It's gonna be
eating rough plant matters, so it needs sort of a
mortal mortar and pestle in the mouth to to mash
it up real good. Yeah. But again, when the when
the teeth are done that's it. And this is going
(21:44):
to lead in the wild especially, is going to lead
to malnutrition and or starvation. So I encourage everyone to
think about elephant teeth the next time you see an elephant.
Certainly if you have the chance to see one in
the wild, but if you see one in a zoo
or what have you, Like, it's teeth are or as
amazing as any other amazing quality of the elephant. Like, yes,
it's trunk is a is a is a marvel of
(22:07):
the natural world. But also it's teeth are just so
super weird. Yeah, this high capacity magazine of molars, Yeah
it is. It's like a magazine a pet dispenser of
teeth um And it's just it's just not what you
come to expect from teeth in general. Like you know,
even even a shark, right, it continually grows those teeth,
but they're growing out of sort of flipping out of
(22:29):
the jaw top and bottom. But the the elephant has
a different system entirely. Now, what is the deal with
tusks since we're talking about elephants, Because we talked with
Katie and we've talked on the show before about the
idea of narwhal tusks. How the narwhal tusks are not
like modified bones. They are teeth, you know, their teeth
jutting up just straight forward, straight out of the mouth. Yeah,
(22:52):
they're they're modified incisors. Is the deal? Oh even an elephants?
Yeah yeah, so um so yeah, it's it's easy to
sort of look at tusks and even if you know
they're not horns, you kind of like think of them,
you kind of categorize them in the same in the
same area. So, yeah, elephants are are weird wonderful creatures,
(23:14):
uh that we've we've been looking at them so long.
There's such a famous animal we can you know, they're
in our story books as as as children, they're in
our animated films. You kind of forget how weirdly alien
they are in many many regards. Is it weird that
I'm just imagining now what it would be like to
get bitten by an elephant? I don't know. I keep
thinking trying to imagine what that would be like to
(23:37):
have um marching molars, to have that kind of dental situation.
And granted we wouldn't because we do not need to
have that for our diet, but if we did, like,
can you imagine your teeth growing in from the back
and then they like breaking off in the front. Also
their soft foods. Yeah, all right, let's take one more
break and we come back. I want to talk just
(23:58):
a little bit about an tee teeth. Okay, alright, we're back.
So we've talked about manatees on the show before. Um mana,
teach me something, Robert. Well. Manatees are, of course marine mammals,
and they are Serenians. Uh, they have a few living
kid that will get to oh SERENI. So are they
named after the sirens? Exactly? Yeah, tying into the whole, uh,
(24:22):
you know, mistaking manatees for mermaid thing. Now, their closest
living relatives are the elephants, and they're kind of like
the elephants of the sea in some respects, you know,
drifting through the waters feasting on vegetation. There are three
extant varieties of manatees. There's the Amazonian manateee, the West
Indian manateee, and the West African manateee, and all of
them have marching molars, much like the elephants. But then
(24:46):
I was reading around a little bit of this about
this and there's a. There's another variety of Serenian that
went extinct in the eighteen hundreds, and this was Stellar's
sea cow. Now it apparently, uh, this was a Serenian
that already had a rather narrow habitat. It was already
like you could make the argument, I think that was
already kind of endangered before human activity really put the
(25:10):
nail in the casket here. But it actually didn't have
true teeth. Uh. It had instead what has been described
as broad horny pads that it used to chew the
soft parts of kelp, which made up most of its diet.
And this leads us to the other existing Serenian, and
(25:31):
that's the Eastern Hemisphere hemispheres do Gong, which looks very
similar to a manity, but it has a shorter snout
which kind of you often see it in pictures. It
looks like a vacuum cleaner because it's essentially what it is.
It's cleaning, it's it's eating off the bottom. Uh. And
it also has a flute tail that looks much like
a whale um. But then you really have to think
(25:53):
about its teeth. So it has no marching molars. It
does not have the marching molars of a manatee. Uh.
They also have incisors, which are essentially a little tusks,
which manatees are lacking. But the thing about doo gongs
is that they also have horny pads in their mouths
for chewing, and they are more important than their actual teeth.
(26:14):
The cheek teeth are almost a non functioning and um
and are not very tough to begin with. So I
was reading a few different papers about them from J. M.
Lanyon and G. D. Sanson in the Journal of Zoology,
and they point out that regarding doo gongs, quote, the
soft mouth parts of the doo gong are highly modified
so that the entire oral cavity functions to crush low
(26:38):
fiber sea grasses. Thus, the doo gong has developed an
efficient method of food ingestion, and mastication that is suited
to put processing large quantities of soft sea grass during
short dive times. The potential cost to the doo gong
and having lost its hard dental surfaces is that it
has become restricted to a low fiber diet. So this
(26:59):
is interesting. The do going eats mostly seagrass, while manatees,
who again have these more robust teeth and have these
marching molars. They eat roughly sixty different varieties of fresh
and saltwater plants. Um. I've read that the difference in
the snout also means that manatees can sort of reach
out a little bit because they just have a more
(27:19):
vary diet. UM. Manatees have also been observed to occasionally
eat fish from nets. So, you know, we generally think
of them as herbivores, and you know, for the most
part they are, but it seems like if they have
the chance to eat a fish out of a net, uh,
they will do so. And so we have another example
of opportunistic carnivory. Yeah. Meanwhile, the doo gong is apparently
(27:42):
not engaging in this in this behavior that we know of,
So that would mean that the doo gong is really
the only true marine herbivore mammal in the world, the
only marine herbivore mammal. Wow. So I guess I'm trying
to think of counter examples. What I can't because you
know what I it is. I think of a lot
of like filter feeding whales as herbivores, and they're not.
(28:06):
They're eating you know, the microscopic animals, their carnivores. Yeah,
we we we we. We don't think of them as
such because they're not trying to eat us. I mean, uh,
you know whale myths aside, the animals they eat are
very small. It's like, are you a carnivore if you
only popcorn shrimp? Some people might not think so, but
(28:26):
but I love I love this as a kind of
a closing example to look at this as the you know,
the doo gong, the manatee and Stellar sea cow as
being examples just within the Sirenian world of how teeth
change with diet and how you can have kind of
you know, rapidly different like the idea you have marching
molars in the manatee and Stellar's sea cow didn't have
(28:47):
teeth at all, and then the doo gong is kind
of in this place in between the two. I just
find that fascinating. And and again, any any chance I
have to explain how cool manatees are, I've got to
take it because a man of teas are just amazing
creatures and if you have the chance to see some
in the wild, you should definitely do so. I got
to see some just the other week. I was down
(29:08):
at downe in Florida at what is it Wakula or
I've also heard Waccola Springs. Got to see multiple manatees
and baby manatees. It was breath tick. Now, the same
way that the manatee and the dugong may have inspired
the Legends of the Mermaid, did the manatees of Wakula
Springs inspire the Creature of the Black Lagoon? The Creature
(29:29):
from the Blackgan They did film some some scenes there um,
mainly like the you know, just the swamp footage. Is
the stuff that they filmed there at the springs. Yeah,
but they weren't you telling me, like they can't do
licensed stuff, like they can't actually have creature materials. They
were at least I think maybe maybe they're not willing,
(29:49):
you know, they're not willing or able to pay out
for the licensing phase. I'm not privy to the details,
So I just know that a few years ago they
had some creature memorabilia there and now there's not any.
But they were showing in Creature from the Black Lagoon
one evening in the lobby and so that was kind
of cool to have gone out on the swamp during
the day and then at night, like to see this
old movie and see these scenes from it, and it's like, oh, well,
(30:10):
there you go. I went by there in a boat
just several hours ago. Uh. I think we've established on
the show that we're firmly on the side of the
creature in the country from the Black Lagoon, and that
the heroes are awful. Yes, there's the alleged scientists in
that in that show are are are awful. There's a
life form shoot it. Luckily those are not the scientists
(30:30):
that are involved in taking care of manatees today. Hey, folks,
if we suddenly sound different, we just jumped into another
space and time. So here we are again. I just
wanted to close out with another quick grab bag of
teeth related stuff that I couldn't stop thinking about. Robert.
You remember at the end of our episode with Katie
where goose teeth came up, right, Yeah, so of course, Um,
(30:55):
geese can sometimes I didn't mean to demonize geese by
the way when talking to Katie, but geese can be
surprisingly aggressive. I think we don't usually worry about birds
getting territorial and attacking us, but if you get too
close to a goose nest, you're you're asking for trouble, right, Yeah,
they're They're more fierce than we sometimes realize. They're also
sott smarter than we sometimes realize. Like there's certainly no
(31:17):
no Corvid's, but there have been some interesting studies that
have put them to the test with the various tasks
and they can actually perform well. Yeah, and so I
think in that episode with Katie we actually talked a
little bit about goose teeth. Now, goose don't actually have
biological teeth with denton and enamel. But if you have
not seen an image of the serrated edges of death
(31:40):
writhing like the dead lights inside a goose mouth, you
have got to go search for this right now. It's
an image that you must see. They're a bunch of
them all over the internet. Uh, Robert, I added one
to your notes, But oh, you might not have your
notes right in front of you, do you. I do not. Well,
it's just got knives in the mouth basically along the
edge of the so basically like the tongue and the
(32:01):
beak are both covered in these fierce jagged sawtooth spines
around the lateral edges and um. The most recent evidence
indicates that existing birds to send from ancestors that lost
their teeth in a multi stage process that took place
roughly between I think about one D sixteen one hundred
one million years ago. Um. So, if you're out there
(32:24):
listener asking, wait a minute, lost their teeth? Birds lost
their teeth. Yes, because, as we've talked about plenty of times,
birds evolve from dinosaurs that definitely had teeth. Arcosaurs archaeopterics
had teeth, and it appears that this period, around a
hundred million years ago, they acquired gene mutations that changed
(32:44):
a couple of things. They change jaw development to stop
the development of teeth as as they matured, and to
cause the development of beaks instead. And one consequence of
this knowledge is that if we can suppress the molecular
their pathways for the gene that suppresses the growth of
teeth in birds, you know, the gene that turns off
(33:06):
tooth development, you turn off the turnoff there, we can
sort of create birds with teeth again. And in fact,
a group of researchers actually did this and and publish
their findings in Current Biology way back in two thousand six.
You've probably I bet this has come up on the
show before at least maybe a while ago, right, was
the transforming of chickens into tiny dinosaurs. Yeah, they already
(33:27):
are tiny dinosaurs they respect, but they are very much tyrannosaurss.
But in this case, I think the resemblance is slightly
less to the therapod dinosaurs and more to crocodilians, because
when they made a couple of genetic tweaks or epigenetic
tweaks to embryonic chickens, the embryos grew teeth that resembled
the conical teeth you would see in the mouth of
(33:49):
an alligator or crocodile, indicating that these were probably pretty
similar to the teeth of ancestral birds more than a
hundred million years ago. So the goose does not have
true teeth. But I wonder if you could crisper up
like a really awful fanged crocodile goose from the deep past.
I bet that could be done, though I don't know
if it would survive development with the mutation. Yeah, I'm
(34:12):
not sure about that, but but I do love this
example because it kind of goes back to what we're
exploring with the Syreneans, that if if teeth are no
longer needed, if they are no longer the best means
of masticating food or or or helping to you know,
to aid in the ingestion of food. They're not going
to stay around forever. I mean, they're they're they're like
anything in the body, they're they're a costly investment. Yeah.
(34:35):
This is one of the things that that we often
fail to remember when we think about evolution without taking
like energy and development concerns in mind, we think of
evolution primarily as a process of addition. But what episode
was it just recently on the show where we talked
about a lot of subtraction evolution. Oh, I think it
was in the one about the phrase survival of the fittest. Yeah,
(34:56):
and what that it tends to imply to people who
you know, uh, if if you haven't thought about it
all that deeply, one thing is that you get this
sort of vague impression that maybe it always works by
like adding new powers and not by just subtracting things
that are useless expenses. Right. And and we also, yeah,
I think discussed as we've discussed before, this whole idea
of something devolving. You know, it's like no evolution. Uh,
(35:19):
you can go in either direction. So if you say
your views on the topic, I've evolved, it's not necessarily
a good thing. Right. It's like if you're your HR
department tells you that your benefits are evolving, not necessarily
a good thing, right, Um, ask more questions to find
out exactly what's going on. Well, yeah, but I mean, yeah,
there is no devolving. It's all evolving. So some evolving
(35:39):
and you might like, and some evolving you might not like.
Who knows. I mean, maybe we could evolve brains that
just feel excruciating pain every moment of the day for
no good reason at all. It just happens to work
that way. Um. But another and interesting evolutionary question is
why did birds lose their teeth? And this is an
unsolved probably blow. We don't have a good answer of
(36:02):
exactly what the evolutionary pressure driving the switch from teeth
to beaks was. Uh the answer. So one historical hypothesis
I've read about is that it helped birds lighten their
bodies to optimize flight dynamics. But I've also read opinions
that's not a very good explanation because you know, we
see tons of flying animals with teeth. Teeth don't necessarily
(36:24):
weigh a whole lot that that seems like that's probably
not a very good candidate for explaining it. So we
don't fully know the answer. I mean, one would assume
it would you know, would come down to diet one
way or another. But yeah, you would think so. I mean,
and one thing you can look at is the different
kinds of beaks that existing birds have. I mean, beak
diversity is is enormous across the aviens that used the
(36:45):
beaks for all kinds of different things. We should come
back and do an episode on beaks, just on beaks, yes,
And we can also talk about the movie Beaks, which
is maybe the most painful bad horror movie I've ever watched. Yeah,
it's a rip off of Alfred Hitchcock's The Birds. Uh,
And so it's just a about birds attacking people. That
that's That's pretty much all you need to know, except
(37:05):
it just happens to have this distinction. And you know me,
I'm somebody who watches tons of bad horror movies. It's
probably the most excruciating one I ever tried to finish.
So that would you say this is worse than bird Dimmick? Oh? Yeah, no,
burd Dimmick is a joy by comparison. I'm not saying
it's I'm not saying it's worse from a filmmaking skill
point of view, but Burdemic was much more enjoyable and
(37:27):
it was easy to make it through the runtime. Beaks
is a film that one of the things, one of
the things I think about it is that it has
a soundtrack with like a really uh, just grading synthesizer
score that has songs. They're not really songs. It's like
a single very high pitch synthesizer note held down for
(37:48):
minutes at a time that starts to just wear on
you as if you you think you have something wrong
with your ears or your brain. It's like a it's
a soundtrack that mimics tended us or something, and it's
just really glee to watch. Anyway, we got sidetracked, but yes,
I think we should come back to an episode on Beaks,
because yeah, beak diversity is is amazing, and so I
(38:08):
guess that brings us back to the actual goose mouth,
the serrated edges inside there along the tongue, along the
beak edges. If those aren't teeth, what's going on there
with those little jagged spines. Uh So, the serrated edges
in a modern bird's beak that that's made of stuff
called tomium. These are these little spiny cutting edges that
can be used kind of like teeth. But from what
(38:29):
I've read, they're they're not usually for what we would
think of as chewing. They're more for grabbing hold of
food like plant matter or like live prey and either
cutting it or gripping it firmly so that the bird
can like keep hold of it and tear it away
from anything it's attached to. Uh So, you can see
this for like, uh, you know, anything that would be
eating like plant matter and trying to tear it away
(38:51):
from whatever it's like the stem or something. Or you
can see it for grabbing hold of a fish and
making sure it doesn't get away. It's just generally useful
for like hooking stuff into the mouth, and of course
and for cutting um and for for a bonus in
bird relatives that also lost their teeth. If you haven't
looked at this, you should check out the mouths of
(39:12):
leather back sea turtles. Have you seen this one, Robert,
I don't know that I have seen leather back sea
turtles before but in the wild. But but I didn't
get a good look in their mouth. Well, actually, I
think with Katie we were talking about some viral images
of animal mouths that you think like, Okay, that's got
to be photoshopped, but actually it turns out to be
totally real. Leather back sea turtle mouths are like this.
(39:35):
They there's some of the photos of them make the
rounds on the internet, and it looks like a made
up monster mouth that somebody is passing off as a fake,
real animal. It's totally real. It looks like a vivid
you know, somebody took the bad acid nightmare of It's
hard to explain because these are the ones that they
look they're swirly looking kind of yeah, they don't so
(39:56):
it's not rows of teeth again, their turtles, they don't
have teeth, but they are these thorns. It's like a
thorn forest. Imagine a sort of fractal sarlac on steroids
with even more teeth, this forest of thorns going down
the esophagus. And what this actually is, it's not teeth,
(40:16):
but it's a covering of cartilage based prongs that are
known as esophageal pappally which what they do is they
help the leather back sea turtle hold onto its prey,
which primarily consists of jellyfish. So imagine you're trying to
eat a jellyfish, this organism that's kind of squishy and
mostly made of water in the water. Yeah, you might
(40:38):
imagine that it's kind of hard to like get that
in the mouth and keep it from slipping out of
the mouth, especially if you're trying to like eject seawater
back out of the mouth while you're eating it and
then to shove it along down through the esophagus. And
apparently the sea turtles have these long digestive tracks that
can hold a whole bunch of jellyfish in them all
(40:58):
at the same time while they're sort of waiting to
be processed by the stomach. So yeah, the thorn forest
in the mouth is mainly for grabbing hold of these
gelatinous masses of prey and holding them in place so
that they don't slip away. But again, another example of
it's not teeth, but they they fulfill some of the
purposes that we associate with teeth. Yeah, So that's that's interesting.
(41:19):
If if teeth did not exist, they would evolve necessary
to invent. All right, Well this has been fun, Robert, Yeah, absolutely,
uh and you know, we again, we only covered so
many teeth there. There are other amazing examples out there,
and if anyone listening can think of some really good ones,
you know, uh, let us know, because we could always
come back and do another sack full of teeth on
(41:41):
the show. And I would love to do beaks. I was.
I was up close and personal with a two can
the other day and um, you know, it's just always
amazing to look at a beak like that, and uh, yeah,
I'd love to go through the world of beaks. In
the meantime, if you want to check out more episodes
of Stuff to Blow your Mind, you can go to
Stuff to Blow your Mind dot com. That's the mother ship.
That's where we'll find them. You'll find various links there
(42:02):
as well. Uh and hey, if you want to support
the show, about the best thing you can do is
to rate and review us wherever we have the power
to do so, and make sure that you have subscribed
to not only Stuff to Blow Your Mind but also
our other show Invention. Huge thanks as always to our
excellent audio producers Seth Nicholas Johnson and Maya Cole. If
you would like to get in touch with us with
feedback on this episode or any other, to suggest a
(42:24):
topic for the future, or just to say hello, you
can email us at contact at stuff to Blow your
Mind dot com. Stuff to Blow Your Mind is a
production of iHeart Radio's How Stuff Works. For more podcasts
(42:44):
from my heart Radio, visit the iHeart Radio app, Apple Podcasts,
or wherever you listen to your favorite shows. Blows Joined
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