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