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