Paleohistology (WHY TEETH EXIST) with Yara Haridy

Ikea presenterar gudav förändring. Du måste prata. De svenska ostklasiker finns med på prickarna när du fyller år, på BB efter förlossningen och i vardagen när alltid precis som vanligt. En liten del av den stora och en stor del av det lilla. Här går Presto Grevé, svenska ostklassiker för små och stora traditioner. Animal anatomy, particularly little weird teeth. I know you never knew that you needed to know about this, and it's wild, it's fascinating. I promise.

Paleontologists who study fossilized prehistoric tissue samples. I love this. This allogist an old friend I met on the internet on Twitter. Ye old Twitter and someone who was always on hand to help identify a bone, who popularized the hashtag guess the skull and loves the history of bones. They were born in Morocco. They grew up in Egypt.

and moved to Canada as a preteen, then did undergrad in pre-med at the University of Toronto before getting a master's in ecology and evolutionary biology there, studying animal jawbone. Then they got their PhD at the Humboldt University of Berlin and as a postdoc at the University of Chicago has already published several papers, including the 2025 Nature Paper, The Origin of Vertebrate Teeth. an evolution of sensory exoskeletons that's like shaking up the fossil world.

And in addition to being a professional paleontologist and an evolutionary biologist, they are also a celebrated science communicator who says that they love finding creative ways to make science accessible, weird, and wonderful for everyone, which this episode does so much.

So we're gonna get into it in a minute, but first thank you so much to patrons of the show who make it possible and they send in hilarious and thoughtful questions before we record. Thank you to everyone out there supporting the show by wearing our merch. from allogiesmerch.com. Uh as a reminder, also we have shorter kid-friendly episodes suitable for all ages and classroom safe, and those are called SMOLOGES, S-M-O-L-O-G-I-E-S.

They're available in their own feed wherever you get podcasts you can subscribe. And thanks to everyone who leaves reviews of the show and to provide evidence that I do read them all. Thank you to recent reviewer Coco Reed's books who said that oldies quote can make the most. Obscure, weird topic, super interesting. Coco, you have no idea. We're about to do it again. Okay, paleohistology. It comes from the words for old tissues.

And the histo in tissues comes from an older Greek word that means web. And I was in Chicago a few months ago for a friend's wedding and the afternoon before the rehearsal dinner I romped off to the Field Museum. to lurk behind the scenes with this allogist I had been admiring from the internet for years. I saw drawers of bones, millions of years old skulls, microscopes, and the evidence that changed how we think about what grows in our mouth.

So prepare to drop your jaws as we discuss the origins of teeth, why yours hurt sometimes, how they got in your mouth, the long-debated rumors of extinct species. How particle accelerators and paleontology worlds collide? What tools fossil pickers rely on? Teeny tiny mysteries. Busting, age old phlimp, and why you should hug a tree before it kills you. Plus, why a catfish might become your overlord. With science communicator, researcher, paleon.

First thing I'll have you do is we could say your first and last name and the pronouns. So I'm Yara Haridi. Doctor Haridi. Doctor Yara Haridi. She her pronouns. Um when did you defend your PhD? I was officially uh awarded to me in January Yeah. I followed you on Twitter for years. Before. I before in the before times. In the before times, the rock and it was Twitter.

When that's where all the scientists gathered. It was such a beautiful time. It was a beautiful time. Yeah. We got to know your work and I always love that whenever someone found a like a raccoon skull under a shed, they would tag you. Be like, What is this? I did become like a go to bone and tooth person, which was my goal in the first place. And honestly that

It's so sad because I used to suggest like social media as a go-to thing all the time. For even for like young people. Uh like young people who are trying to get into science. because it was such a good resource. You know, I I got jobs off of it. I got talking head gigs. I got collaborations like actual science collaborations where someone's like, well, wait, I have the machine that can do this. Yeah. I

Friends, I got you know, all that kind of stuff. And it was a really, really beautiful place. Um hopefully science will come together again somewhere else. Nothing but blue sky. So I am excited to catch up with you because I've wanted to have you on for so long. Now, okay, the ology itself. I saw that you have a paper, histological skeleton chronology. That a possibility. Paleodentology. What what are we thinking? What would you say your ology is?

I mean, when people ask me like what my main method is, it's paleohistology. So I feel like that would be a really good one. And paleohistology is just the study of ancient tissues. So histology is just literally the study of tissues and then paleohistology, you just make that ancient. Old, old. Yeah, old, old. We're talking tissues, but we're also talking teeth. Mm-hmm. Is the tooth a tissue?

So what makes up a tooth are the different tissues we'll be talking about. So like dentine, enamel, those are like words that people have heard from, you know, your toothpaste commercials. Yeah. So those will be the tissues, but the structure as a whole is the And take me back, when did you start getting interested in paleontology? Oh girl, this is uh this is like I feel like it's such an odd story because so many people, especially in Paleo, they were dino kids and they knew they just

You know, my my husband's that way where he's like, I just knew that this is at least a direction I wanted to go. Not paleo particularly, but like art for example. Paleo tends to be like that, where a lot of people have been into it since forever. But I took like a couple of wrong turns to even get here. So I grew up in the Middle East.

And in the Middle East, you don't really have like a dinosaur phase as a kid. It wasn't marketed that way, you know, I'm nineteen ninety four, so good year. But, you know, Jurassic Park was just becoming like big and so It just wasn't as big in the Middle East and it wasn't a thing and I didn't really understand that that could be a career. And so then we immigrated to Canada and I started going to university and really being interested in science.

And, you know, I'm Egyptian, so in our culture, you can be a few things. You can be a doctor, you can be a pharmacist, you can be an engineer, or you can be a disappointment. So, uh, what I decided to go into a science and try to at least go into being a doctor. So I was studying for med school.

And man, I just wasn't enjoying it. And the parts that I enjoyed were the anatomy, the physiology, how things worked. As I was studying for med school, I volunteered in a paleo lab and I fell in love with paleontology. And yeah, a couple of right turns turn left or a couple of left turns turn right. And I got into paleo. They offered me a master's and I continued from there. What was it about it? Was it just the age, like the unfathomable age? Was it the structure?

That's a really good question. And I can actually mark the point where it like happened. They had me picking fossils and picking fossils is when you just sit on a microscope and you're like picking little microscopic like little bones from salamanders or teeth. And that was fun. And I think the shape of fossils is interesting. And I was just kind of mind blown that these were from the Permian. So they were two hundred eighty plus million years old which was

breaks your brain if you are not used to those numbers and who is. Yeah. But then there was a PhD student in the lab at the time and he taught me this method called paleohistology and the study of And I didn't understand what that meant at the time because What do you mean tissues?

survived in these two hundred and eighty million plus year old fossils. And so we cut them up and you can see under the microscope the bone tissue. You can start asking different questions, uh like how old is this animal? How did it grow? How fast does it grow? What are the blood vessels like? Same thing with teeth. Does it replace its teeth?

Uh, how does it grow its teeth? All that was still preserved. And at that point it went from like mind blown to like shattered, like gone. Because that was crazy. You can see cell spaces, you can see lines where like, you know, this animal had a hard winter. All that was recorded in the fossils. And at that point, I was like, oh wait.

This might be a real sci. This might be a real actual thing. Well before that everyone's just photographing externally like these fossils and it's not that that isn't science, of course it is. But it just wasn't as it didn't tickle that little part of my brain of like, we can go deeper. We can see how this animal ticked. What did its blood vessels do? What did its cells do? Yeah.

I feel like if you were not a fossil person, not a paleo person, you think the only things that maybe survived were the bones. And then you read an article where you're like, we know that there were feathers in here. Okay, we know there were scales. But I either imagine Hard bones that survived and everything else rotted out or scale something

Something's still hard. Something's still hard, yes. Something with with a structure to it. And that's fair,'cause that's the vast majority of fossils. That's like ninety-nine point nine percent of fossils are actually teeth because enamel is the hardest vertebrate tissue.

And so it survives really well. It's already very crystallized. So like how much more crystallized can the earth make you? So they survive really, really well. A bone being secondary to that. But there are exceptional preservation moments in Earth where the right bacteria didn't get to it or the right bacteria did get to it. And they preserve feathers, they preserve skin. We now have ichthyosaur blubber. People like have

you know, actually done um isotopic measurements and know that it's fat that was preserved in a really interesting chemical way. And it is rock. But it takes the impression of all those tissues? Not always. Oh what yeah, yeah, yeah. So fair, right? That's kind of the the old thinking of like, well

It's just an impression, like the scales, for example, like how do you know, like dinosaur mummies and stuff. Sometimes they are impressions. Sometimes the soft tissue left an impression and then disappear. Sometimes the tissue itself gets mineralized. So for example, let's think of your skin. There's multiple layers in your skin and some parts of them basically get replaced one-to-one or they get crosslinked or get changed in some chemical way that makes them stable.

So they actually preserve as that tissue that has been infused with new chemicals that are stable. I didn't realize that soft tissues were even something that you could look at. Now, between the soft tissues, And the teeth. Teeth obviously evolved over time. When did things start getting Teeth. So that is basically the question of my life. When did things start getting teeth? Or if I can like extrapolate that even more, it's like when did things start getting mineralized?

Okay. So we have this process called biomineralization where we um or organisms as a whole will basically take minerals from the environment and make a skeleton out of them. And we're not the first to do that. You know, sponges have skeletons, they have glass skeletons.

Shelled organisms like mollusks, they have skeletons too. Those shells count. Uh calcium carbonate skeletons, arthropods have exoskeletons. Um so just taking stuff from the environment and making your own skeleton. We do that too. And so we make bone, we make teeth. Our skeletons are made of calcium phosphate. But what's interesting, of course, is that these mineralized specimens fossilize really well. And so we can go back in time and be like, okay, what's the first animal to have?

Tooth tissues on it. What are the first animal to have bone tissues? And as far as we know, we kind of trace it all the way back. Deep, deep, deep in time into like the middle Ordovician. So about four hundred and fifty five million years ago. Woof. Yeah. Hard hard to kind of conceptualize, right? Okay, so dinosaurs went extinct when?

Oh, 65. 65, yeah. Yeah, right. So, and then these like bone has existed for a very long time. Tooth tissues have existed for a very long time. And I say tooth tissues because they weren't exactly Were they ever made of cartilage? And get harder, or they were always mineralized. Did animals ever have like kind of gummy, like blah blah blah, like kind of like teeth?

I love. Did they just gum things to death in the ocean? Yeah. Um probably, but also more likely is that they were just suction feeding. There was some kind of filter feeding that happened early on. So the very first Tooth-like structures to appear in the fossil record don't appear in the mouth. They appear on the outside.

They disappear on the outside on these like scales and dermal bone, which is partially nightmarish until you see how ridiculous these fish look like because they're nonsense looking. They look like you know yet like a handheld vacuum that you're gonna like clean your car with or they look like that but stick googly eyes on the end. Oh no. Because their mouth is always open because they don't have jaws yet.

So these little tooth-like things that are on the outside of these fish, we call them odontodes. So that's a word I'm gonna be using often. So odontodes are Little chunks that basically look like a tooth, but they're on on the outside of the mouth. They're made of enamel and dentine and they have a pulp cap. But they cover the outside of fish rather than being the uh inside of the mouth. It sounds like a teratoma. You know? Yeah, yeah, totally.

A blob item with teeth sticking out everywhere. But w what did they use them for on the outside? Boom, exactly. We don't like so we don't know or we didn't. We had a couple hypotheses. Why would you have these things on the outside of your body? The very first answer was always like protection. Like, oh, you're making your hardest tissue on the outside of the body, you're

to make armor, you know. A lot of modern fish do that. Things like gar have really um hardened scales that cover their entire bodies. Makes it harder for things to bite you. Yeah. Uh makes it harder for parasites to get attached, etc. Please, please see our Garology episode about long, cute, ancient, patient, boobable nightmare fish with the iconic biologist and punster Doctor Solomon David, as well as our teratology episode about the history and culture of monsters in fiction.

Because the a teratoma is a blob that can grow in your body, but with fully formed teeth and clots of hair. And if you listen to the end of the episode, I'll tell you. my own personal secret about teratomas. But yes, millions of years before actual teeth. And of course the image of like teeth outside the mouth is so grotesque. Yeah. But If you think about like modern sharks, modern sharks have teeth outside the mouth, or they have these odontos, they're covered of them.

So if you pet sharks one way, it's smooth, but if you pet them the other way, it's super rough. That sandpaper feeling you get from sharks, it's because they have little tiny teeth all in their skin. Those are Adontos? Yeah. Exactly. Covered in tiny teeth. Mm-hmm. Yeah. I love that the big teeth.

in a shark are what freak people out, but little do they know they have an army of tiny teeth also backing them up. Yep. So the first ones though were outside the body. When did they start merging into the hole? Uh merging into the hole. Um, should we go back to the what are they for on the outside?

So there's a couple h floating hypotheses. There's one that's like okay, they're for protection because they're hard on their own and they're on the outside. And at that time period, middle or division, there's like big scary things in the ocean, big cephalopods, so big

Squid nautiloid looking things that would eat our little fishy ancestors. There's big sea scorpions that are bigger than you or I that are up to like six feet or more. Again, things that would eat our little fishy ancestors. So it makes sense that the first hypothesis was protective. Another one that's based more on sharks. is that maybe it helps them with locomotion. So when I said these fish are really weird looking, they don't have fins yet.

So so the first ones didn't have pectoral fins, they just had a tail, it's like a tube. Like I said, it's an Handheld vacuum with eyes on the end and an open mouth. So how do they move around in these like turbulent seas? How do you make your locomotion more efficient? Sharks.

They use the little spikes on in their skin, these little teeth on the outside, there are dontodes, to help basically with hydrodynamics. The way that the water flows over their body is more efficient because of the little bumps all over. So maybe the early fish did that too. So that's one other theory. And then the last theory is that maybe it has something to do with sensation, that maybe because our modern teeth are sensitive, maybe the outside ones.

How big were these outside ones? Were they teeny or were they like I think I should just show you. They're beh they're in the cabinets behind us. Yeah, grab one. Yeah. Okay. Give me one second. Okay. I just love that you're like, well, we've got something that's millions and millions of years old over here.

Like how I would pull a coffee mug out of a cabinet. This is the first time I've ever heard the word odontoed, also which is exciting. I didn't know that there was even a generalized name for them. This hall of cabinets is So bonkers. So I have a part of a head shield from a jawless fish. And what you can see here. No. It looks a dontoed. It looks kind of like a tiny cottage cheese ceiling, you know? Yeah, yeah. The popcorniness of it, the the textures.

They're like little tiny beads almost. And now you clarified that you have gotten flack here and there for calling it a two. Because a tooth is in a jaw. Yeah. But we're talking broadly to communicate what it's an analogous structure. Right. Or homologous, right? Homologous. Okay. Because they have the same orange.

So w the reason that we know that these sedontos on the outside of the mouth are even related to teeth is because they're made of the same thing. They're made of enamel, they're made of dentine, they have pulp cavities, they have the same blood supply. So they they act very similar to our own teeth in the mouth, except that they don't replace the same way and they don't have a job in that they don't chew. And then they started coming merging, they started saying, let's get in the hole.

So how did we get tea? in the mouth or how did you how did you go from odontodes, things that are bumpy outside the head, to things that I can bite other fish with. So that happened along some we assume some time in probably the Devonian. So the Devonian was a cute little 60 million year era from about 420 million years ago to 360 or so million years ago. And it was a party. It involved plants growing on land, the formation of leaves and seeds, critters.

Slithering out of the water into their terrestrial destinies. We had shelled bugs, we had fishes with jaws. In fact, it was called the age of fishes. There were even now extinct things called placoderms, meaning flat plate fish, that looked like they were wearing bulletproof vests. And helmet. 400 million years ago, primitive sharks were like, hey, about a million years before trees existed. Sharks older than trees.

Also be nice to sharks. Trees killed 71 people in the US in 2023, but unprovoked sharks killed 10 globally. Only two of those were in the US. Sharks are the eldest daughter of our planet. And so what we have is a couple of fossils that ha are covered in these little bumps all the way across their face and right at the margin of the jaw, which had now evolved.

uh you have sharper and pointier dontodes and they kind of grade into the mouth and then you have actual pointy things in the mouth based on ostensibly teeth. We see those probably whites, huh? So that's one way that we think it happened. The other way that we think it could have happened is just whatever genetics that make up Adontodes, they got re-expressed inside the mouse. Oh, okay. So it doesn't have to be a gradual like actual movement of the structure into the mouth.

but it can be a re expression, just, hey, let me take this toolbox that I use up here and I'm gonna express it in the mouth instead. Kinda like when you get a weird hair that pops up somewhere else. You go, what are you doing here? Yeah, except I don't recommend tweezing out your teeth. No, don't do it. Don't do it. Okay, what's the difference between a tusk and a tooth?

One is ivory. What's ivory versus ivory is just dentine. Ivory is just dentine. Does that mean there's no enamel or pulp? So tusks are just teeth. Uh-huh. Uh, but they're fancy teeth. In that they uh Are usually non replacing. They're usually continuously growing. So elephants are the famous tusk.

When they're babies, they have a little itty bitty enamel cap on the end of their tooth. And then as it keeps growing, that usually gets worn away because they just like rub'em on trees, they dig with them, they fight, and then it ends up all being dentine. Yeah. Got it. Okay. I wonder why they don't keep the enamel since the enamel's so hard. Well, I think it's just it gets worn away after a while. Um also there's a bunch of studies that are really interesting that show that

Elephants use their tusks as like sensory things. So they hit them on the ground and they like feel vibrations with them. Yeah. So there is some kind of feedback that they're g they're not just like whacking around Big sticks. Like there is some feedback. It's a living tissue, right? Underneath that is the yellowish dentine, which is softer than the outside enamel, but still hard tissue. And it's protecting that little lump of inner pulp in the tooth.

and dentine is made up of collagen proteins, and according to a chapter in the journal Engineered Regeneration. banger have a book. There are fine tubes arranged in dentine known as dentine tubules. And when dentine is exposed, it can transfer cold, hot, Sour and sweet. stimulation from outside to the pulp nerve and cause pain. And darlings, we owe you an odontology teeth episode. We also owe you an elephant episode. We're working on it.

Our pacchidermatologist of choice has been in the field for like two years. We're waiting for her to become available. Please don't yell at me, you sweet little brats. And this is one thing in a recent paper of yours about sensitive teeth. Like blame your fish ancestors. Yep. Um which I got a crown replaced and I can't drink cold water on that side. It's been like two months and I'm just angry about it and I'm dehydrated and Oh no. It's just I guess a time mention.

But I do blame my fish ancestors. I'm pissed at them. It's a good start. So a sensory organ on the outside also helps them figure out like How cold the water is? What? This is such a good question. But basically, we don't know. We don't know what they're sensing because not only are we sensing cold, we can sense sweetness, we can sense pressure with our teeth.

Some people have s uh sweet sensitivity. So they just eat like a candy and they get some uh sensitivity from it. I mean, you know, you felt like if you press really hard on your teeth, you can feel'em. I know you just pressed on your teeth. I know it. Yeah. So our teeth can sense multiple things. The reason we sense cold is Later. Basically, the signal gets sent out, and how does it get decoded later? Your brain says this signal means coal.

So that happens down the line. That could technically be almost anything. So I don't know if these early fish had. this tissue basically, and then downstream they had it sensed for like, hey, it's warm water or cold water or a change in tides or something's trying to bite me or the sediment flow change. or any of that. We don't know exactly what they're sensing, but we know that some kind of signal was getting And then tell me a little bit about this paper.

So this paper has been the nightmare of the past three years. Okay. Checks out. Yeah. So It's an interesting story because It's a a really winding pathway and I think it shows how science is not very linear. And sometimes when we set out to research one thing or look for one thing, we get a much more complicated story. Tends to be a lot more interesting. So I basically had pitched to come to Chicago, uh to do my work at University of Chicago. I pitched, hey, I wanna look at the very first

thing in the fossil record that might have odontodes, that might have bone. Let's figure out where our skeletons came from by understanding these early tissues. I wanted to cut it up. I want to scan it. We have really good ways to scan things now. Let's like throw everything at this Fossil.

And the fossil I was really interested in was this animal from the latest Cambrian. And again, this was 300 to 400 million years ago. This was hundreds of millions of years before Pangea existed and then broke apart.

So we're going way, way back. And Dr. Haridi is like casually in possession of teeth of an age that are beyond my capacity to fathom. She published a paper in May of twenty twenty five in the venerated journal Nature titled The origin of vertebrate teeth and evolution of sensory exoskeletons.

The origin of vertebrate teeth has been a longstanding problem in paleontology. Although teeth evolved from structures in the dermal exoskeleton of jawless vertebrates known as odontodes, their origin and function remains obscure. And this paper is groundbreaking and that's not a fossil pun, but it's already racking up citations. despite being like just a few months old. So we'll get into why later in the episode when we know what more words mean. And also it's a juicy story.

and had some fascinating reactions. Now if you remember earlier I said the best things that we know the earliest vertebrates are from the middle Ordovician. The Cambrian is just before the Ordovician. But the problem with these fossils is that they're super fragmentary. And when I say super fragmentary, I'm saying like

Like fits on a end of a toothpick tiny. Oh dear. Um yeah. Oh dear is right. Uh because when you tell someone, oh, I'm a paleontologist, and then you show them the fossils you work on. I make a lot of seven year olds very disappointed. And fragmentary, that's the whole tooth or that is just it burst into shards? Sh I should show you.

Is it teeny? Yeah. What do you got? Oh my god. These are the oh teeny teeny. And I got how they're actually found in the rock. You know what they look like? They look like nerds. It's like the smallest nerds. And they're in a vial, you're pouring them out. Those are teeth? Those look like gravel. I know, right? Those look like decomposed granite in a fancy garden. Can you see the little white bumps? Yes.

So this is part of dermal bone on these ancient fish. So I'm basically holding like what is it? You say fragments of like cereal. They're so tiny. They are like grape nuts. Yeah. The size of grape nuts. Um, and we get really good data from them. Oddly enough, they scan beautifully, they section beautifully. Under a microscope, they're just gorgeous. And the enamel is intact. Every one of those little bumps is a little odontoed. No. Every single one.

So the odontos adhere to the dermal bone and that's how they make their armor. Yeah. Yeah. And so they're covered in these ones. They're really tiny. They're even tinier than the other piece that I showed you earlier. And so this is the earliest representation of what some of these fragmentary early, early mineralizing vertebrates look like. They're

Teeny tiny. So when someone tells you the fossil record is a problem, this is it. I mean, you could overlook that so easily. And here you have a rock. And you've circled some things and there are absolutely pinprick little white lightish structures. And you've got to go in there. Do you use ironically a dental tool? Yes. Yes. Yeah, we use dental tools all the time and dental putty to like make molds and stuff. Uh yeah, I'm friends with a lot of people.

I bet. I hope you have a good dentist. I can't believe how teeny is so I just opened another vial and poured in another Bunch of scrap. But um this one's supposedly from a different species. And so you can kind of tell because the shape of the odontodes is different. Uh they're more elongate, they kind of look like little rice grains, except Smaller than rice grains? Yeah, they're like wavy almost. Yeah. So these grains of rice, these little pebbles, they are the proto teeth.

that covered marine animals four hundred and seventy five million years ago in what is now North America. And the ones we're looking at, the vial of wavy rice grains that Dr. Haridi painstakingly picked out of a rock. So we sat down at the table with this array of ancient specimens around us like tapas. They're all over North America. And how big was this animal? It's a good question. We don't get many articulated specimens, so specimens that are still together and in life form.

And so it's really hard to estimate. We there is one partially articulated head, which is only a couple of centimeters wide, but then there's another one that's Quite a bit bigger. So we don't know if what we're catching is a baby and an adult. We're really unsure. It's very hard to estimate what these earliest, earliest ones looked like. How many people in the world do this? Paleohistology as a whole or looking for tiny teeth like this.

Um, probably a handful, probably less than ten of us. Yeah. Are you guys on a WhatsApp thread? Um, I don't think so. We kind of meet regularly in conferences and stuff. And then everyone kind of approaches it a little bit differently. So I'm probably one of the only ones that does the histology. A few others do, but some people look at it from morphology, so the shape.

Some people look at it taxonomy, they look at the actual like individual species, but I'm interested in the tissue. Why dentine? Why enamel? Why bone? And I'm interested in that because before these guys, there was squishy. There's all kinds of squishy early vertebrates. And so I'm really interested in the jump from gooey things that were our vertebrate ancestors, chordates, et cetera, to the jump of like fully armored fish. Because in the fossil record, that looks like

It just happens. There's no transition between fully naked goopy thing to mega armored fish. We don't have anything in the middle. We don't have a lightly armored fish in between. Is it unnerving to know that that Missing link is somewhere in a rock. that y'all haven't found yet? I think that's a hopeful thing'cause I'm I'm excited. I mean, that's the direction I want my research to go. That's what we're hoping to find. It's still, you know.

Uh when I talk to kids nowadays, they're like, oh everything's been discovered or you know a lot of people think that about science. Oh everything's already been found out, but there's still so much mystery and this is one of them. So there's a lot of space for young scientists to come in and expand. Especially with new technology, there's a lot of ways to ask or re ask old questions. Are you out in the field wearing khaki garments and like a hat?

in most of the summer. What does your field work look like? So I was just out in Colorado. We were looking at this one road cut. So there's this one area they're about to dynamite because they're making this road really wide.

And that area has this formation called the Harding Sandstone, which is something that we are interested in because that's where we find these little guys from the middle or division. So they called me up and they're like, Hey, are you interested in working on this before we blow it up? Absolutely. Yes, please. Ha ha ha. So we've been out there digging. Uh yeah, the whole the whole thing. Um

And we dug a lot in that hillside, found a lot of these fragments, a lot of scales. We were very lucky, but we're still looking for a more complete guy, because that's really what we want. I wanna see what a face of these weirdos looks like. Yeah. Does it have a tail? Is it, you know, all that. stuff. So we we weren't able to hit that just yet, but we'll go back soon. I remember talking to Michael Habib and uh asking about how much it cost for a dino dig.

And he's like, Gas and I was like, Two million? Three million? He was like ten thousand dollars. Yeah. And I was like the less than a Camry. Less than a used Camry to dig up dinosaurs. Like, is it tough to get an inn when you know they're gonna dynamite something and you're like, oh, there's so much good stuff in there? Do you have to choose like I'm gonna put this on hold and I'm gonna go to the place where you're about to dynamite and I'll get to you later in the protected lands?

Totally. Totally. I mean, but that that's all of life, right? You have to kind of move things around and reprioritize. So when we found out that this area was getting dynamited, we went to check it out, moved a bunch of things aside and went and checked it out. But like have you said, it's so much cheaper than people think.

And that's again why it's even crazier that it's so hard to get science funding. Because I mean, the my last field work was maybe only two, three grand to get a few people out there for a whole week and dig it up and, you know, and really get a good survey and do a lot of science. A lot of But it's just hard. It's sometimes hard to scrap that together. Yeah. Bonkers to me.

Considering that that's like one dinner. That's like one dinner in Washington. It's just some hop nobbing over champagne somewhere with a lobbyist. I don't know. And now I think in many ways Scientists are realizing that we need donors, we need people who are into it. Once you get the specimens out of the ground, they need to be prepared.

And it's the preparation that can be really expensive because you're hiring a highly skilled person and paying them fairly, hopefully. And so that can be a lot of hours of manual skilled labor. Uh and people have funded that. People have found like ways to fund that. They did that for Sue. Like, how do you fund the preparation of this giant T Rex? It's a little bit easier to sell a T Rex than it is to sell.

A jawless floppy fish covered in teeth. My children are not loved. Yeah, yeah. Finless things. Yeah. Um, can I I know we have so much more to cover, but can I cover it with Patreon questions? Absolutely. Okay. Let's see what they've asked. But first, let's donate to a cause of Yara's choosing, and this week she selected the Samir Project, which assists families who want to return home to Gaza by cleaning the streets of rubble, cleaning debris-filled structures.

renting and fueling heavy machinery and bringing large crews to tend to destroyed neighborhoods. and working on destroyed water lines. They also have an initiative right now called Give Warmth to Gaza, protecting families from the wind and rain and giving the warmth of care and recovery with blankets, tarps, tents, and clothing. And for more context, on Gazan displacement and mass death.

From offenses from Israel, you can see our genocidology episode and its recent updated encore with a world-renowned genocide scholar, Dr. Dirk Moses. So that donation was on behalf of Dr. Yara Haridi. And thank you so much to sponsors of the show who make it possible to donate to a different charity close to the Oligist Hearts each week. Ikea presenterar Ljud av förändring. Nu är min turismärk. Nu är slut! Nej, jag har inte det tänkt på! Går från vänner till rival.

Välkommen till Wikia. Vings utvalda hotell för vuxna har allt som gör det svårt att åka hem. Profyllda poler och span, förstklassiga restauranger och mycket annat du inte vill släppa taget. Missa inte våra fina sommarabatter. Boka en semester du inte vill hemfrå. Svenska ostklassiker finns med på prickarna när du fyller år, på BB efter förlossningen och i vardagen när allt är precis som vanligt. En liten del av det stora och en stor del av det lilla.

Här går Präst och greve, svenska ostklassiker för små och stora traditioner. Okay, thanks also to patrons of the show who submit questions before we record via patreon.com slash ologies. It is hard to select which of your strong toothy contenders to start with, but patrons Peter and Gregorius of Thompson. had a whale of one. As did. Mouse Paxton, Spicy Native both wanted to know, in Spicy Native's words, baleen. When did it evolve? Is whale baleen? Mouse asked.

Considered teeth? Ooh, it's a very good question. What is it? I I thought it was keratinized, right? You're right. Okay. Yeah. So not a teeth, not a d not an odont. Oh you got it? Odontoin. Odonto. You got this. Why can't I do it? Because you're not believing in yourself. No. Odonto. Toads. Odentoades. Oh. Odentoads. Yeah, yeah, yeah. It's fine. I'm new at this word. We'll get it. We'll get it.

Um no, you're absolutely right. Ten points per alley. Okay. That they're totally keratinized. And so if they're keratinized, they don't have dentine, they don't have enamel, and so they're not. Uh Odontodes. Did it. They did it. I was so proud of you. Thankfully. Um yeah, okay. So great question from uh your listeners.

Baline is not teeth. It is completely different tissue. And where did it come from? That's such a good question. So that's a whole section of study because we have fossils that look like they might have bow. Oh. Yeah. So so baline whales came from toothy ancestors. They came from whales that have. teeth and so at some point they start losing one and gaining the other.

And that is quite like a controversial topic'cause I think there's like one team that's like, No, they lost teeth first and then gained baleen and then another team says that there's an overlap there. But yeah, so it just depends on how you're interpreting these like really middle fossils. Do you think all that extra vascularity, all that extra blood supply around the lip of this certain fossil, is that because of baleen or is that just because Maybe it had fleshy lips. I don't know.

So yeah, that's a whole area. People don't really know exactly how they were uh baleen evolved, but I think people are getting closer. There's a lot of really cool new fossils in that time period. Could balen, because it's keratinized, be sort of like hair that's like Just hang it out in the mouth. I mean it so keratin is incredibly diverse tissue because our skin has keratin. our hair has character and our nails have so it can just be expressed anywhere really and I'm not a whalologist.

But um I think they probably just re-expressed that there. I don't know what an intermediate would look like. Maybe they had like weird mustaches. I don't know. No, like a little walrus. That's a really good idea. We still haven't done a cetology episode about whales, but we have done one on functional morphology that discusses

what happens when a whale shows up on a beach dead and you have to go over the speed limit with a saw and axes in the backseat to get there before it explodes, but you get stopped by the cops. Myanmar, Planet Silorane, Empress of Smallwood, T Nas, wanna know Ryanast. Are bird beaks teeth? Ooh. Bird beaks are not teeth. That's another keratin structure. But bird teeth.

Did have teeth at some point. Do they not have teeth now? No birds have teeth now. Oh, okay. What what happened to them? Very good question. Don't know. Okay. How are they chewing stuff? They don't chew. Birds don't chew. At all? Mm-mm. No, no. Uh birds kinda like do a grab and swallow.

How's it got the crop? They got a crop. They also have like sometimes little keratin horns on their tongue that that help that help them push things back into their gullet. Yeah, their crop has like all these little stones sometimes and grit and stuff that helps them chew.

But they're kind of like whole meal eaters, really. Yeah, they don't really chew. They'll tear things apart, you know, and feed their babies and stuff, but they won't chew. There is one hypothesis that basically as teeth were lost.

in birdie ancestors, that's when the beak started to like fully envelop. Because it's kinda hard to imagine how beak and teeth coexist. Like does the tooth keep growing through the beak? How do those two tissues merge I'm not saying it can't happen, but we just as so far as we know Things that have true beaks in the fossil record do not tend to have teeth, uh, at least in the on the bird side. So birds are dinosaurs. So on the direction of evolving to birds, they lost.

a lot of their teeth and did full ramphetheca, which is the fancy word for beak. So when you get attacked by a goose or killed by like a cassowary cast cassary. Cassary? Yeah. They're gumming you with keratin sort of? So I mean a goose is gonna like You you can take a goose. Guys, most of you can take a goose. Don't don't upset the geese, but you can take a goose. Um you'll see like little bumps. on the goose's beak and that's just keratin like sticking down.

And a castleary is not gonna kill you with its beak, isn't gonna kill you with its foot. Again, another caraton structure. Don't mess with castworks. You can take a goose, but you can't take a castware. No don't do it. No, don't do it. Don't do it.

one of my biggest fears. Cast worries? Yeah. Just getting in it accidentally getting in a situation where we're one on one and knowing I'm cooked. Cause I just know I would give up instantly. I just feel like A grizzly I'm like maybe I could boop in the nose, but I can't boop that thing in the beak or not. You're not I would take a Casper over Grizzly.

This is a good question. This is a great question. I'm gonna take a pole. Would you guys take a castawary or would you take a grizzly? I don't know. That's a great question. I gotta figure out too if Castawaris can fly. I don't think they can at all. Yeah, okay, not even up a tree. Okay. No. The grizzly can't go up a tree. Still. Okay. Also Castaways are such good dads. The dads do most of the caretaking. They're so sweet. Okay.

Hang out with the Casawares. Yeah. No, not the grizzlies. I went down a detour looking for a Casawary expert because according to my friend, Wikipedia, Cassawaris are wary of humans, but if provoked. They are capable of inflicting serious, even fatal, injuries. They are known to attack both dogs and people, and the Cassawari has often been labeled the world's most dangerous bird. Although in terms of recorded statistics, it says

it pales in comparison to the common ostrich, which kills two to three humans per year in South Africa. Still, trees and gravity, they're a more vicious team. They will snap you in half. Not even blink on that note. Okay, Lars Watts, Howdy Crab, Joshua YYZ wanna know about bone density. Do you think from a histological perspective, do you think that hormones were affecting? These structures like these um Odonto.

I said it. Louder. Odontotes. You killed her. I did no caffeine today and I also Why didn't we do coffee first? I don't know. I don't know. And I will also recommend you. I'll plead also that I'm on Pacific Time. But hormones affecting bone density, tooth density? Bone density, absolutely. So definitely our hormones affect how most of our skeleton grows, but particularly our bones. This is why women are very susceptible in menopause.

to losing bone density, we start to lose some of our estrogen, and that helps us maintain bone density. Basically tells our bone cells, these things called osteocytes to be more sensitive in certain ways so that they can Help other cells communicate. So a little bit of bone bio one oh one but Basically, within our bones, there's really just the three cell types there's the osteoclasts, the bone destroyers.

Osteoblasts, the bone builders, and then osteocytes, the ones that live and maintain inside of the So we have an osteology episode all about bones and donating yourself to a body farm. But I'm gonna blame two hours of jet lag for my memory's soggy spots. And I love a refresher. But when we lose hormones or certain types of hormones.

It messes with the way that they communicate. And so all of a sudden you have more osteoclast activity. So removing too much bone and not enough building of bone. What happens with that? Well, we get osteoporosis. Yeah. And so totally, hormones play a huge role in how we maintain our skeleton, particularly bone density. This is also a problem when it comes to

space travel because we lose bone density if we're not actually working out or getting gravity acting upon our skeleton. So that's how the twin experiment where they sent one astronaut into space and like Twin on Earth came back, and I think he had lost some crazy amount of bone density. And it takes him a certain number of months to gain that back.

Just a side note, we talked about these twins and the one on Earth being like, You can take my blood and poop for science, but I'd draw the line at eating rehydrated steak. And that was in the astro bromatology episode about space food. But for more on this parent trap of space data, you can see the NASA twin study, a multidimensional analysis of a year-long human space flight. For the record, I have never, I looked at this paper, I have never seen so many co-authors.

on one study. I squinted counting eighty four of them. And I might be one or two off because it's I counted so long that I got bored and I started thinking about hockey players kissing. But yeah, this NASA twin study about twin brothers, uh Scott and Mark Kelly, both astronauts. Mark Kelly, yes, an astronaut and an Arizona State Senator, husband to Gabby Gifford.

It involved physiological, telemetric, transcriptomic, epigenetic, proteamic, metabolic, immune, microbiomic, cardiovascular, vision related, and cognitive data that were collected over twenty-five months and it found Changes in telomere length and epigenetics. Changes in gut biome, body weight, carotid artery dimensions, retinal thickness, inflammation, cytokines.

cognitive performance and bone density, which dropped several percentage points. But yes, many things can break down that scaffolding in your body. And then is the same thing true for pressure with teeth? Does enamel wear down or do your teeth say, hey, we've got a lot of pressure. I better build this up.

So unfortunately, our teeth don't react the same way because they don't have osteocytes. They don't usually have cells inside that will adapt to the change in real time. There's small adaptations, especially with our teeth, human teeth. that we have things like secondary dentine, we have uh slight remineralization of our enamel. So, you know, if you have really weak enamel, there are ways to make it stronger, fluoride being one of them.

And then dentine, if there's damage, you'll have secondary dentine start to deposit and like kind of block. the hole from forming. That's kind of how our teeth try to react to cavities, because you really don't want a hole right to your nerves, which are in your pulp cavity, which is why your teeth hurt. Yeah. Ooh. We need a tooth episode, I know, but your pod mother recently found out that his tooth clenching at night has worn down his enamel and contributed to cavities and he is pissed.

And now he has to wear a night guard, but he can't really talk with it yet'cause he just got it. So in bed he'll turn out the light to go to sleep, but then he thinks of something else to tell me, and I can't understand a word he says. But it's spitty and it's charming. Mouth guarders. You're not alone.

You're doing great. So patrons asking about historical tooth decay. Katie Elmer, Emma T, Rott Weisswaffel, Han the B, Kim Grinier, Era Victor, Empress of Smallwood, Mariah Waltzer, and Deli Dames. This was a good question. Also, everyone, you gotta brush your kitties and doggies teeth. I we love their disgusting devil breath, but you gotta get in there, rub them with a little uh veterinary toothpaste. and a brush or a rag tell them they're precious and perfect babies. If you have a pet shark

you might have to brush them less because they are sharp and also because their teeth are like on a subscription model. They just keep showing up. They lose on average a tooth a week. Patrons envious of this adaptation had questions, including Regular, who asked, Why do we only get two sets of teeth in our life while other animals get infinite teeth? Actually, is that true or flimflam?

As well as Glory Fulford, Wynn Rip Rebecca Smith, Megan Walker, Naomi Jane, Alyssa McElroy, Katze, Alexandra Rambo, Sheila Marita, Honeypie, Tom Boudry, Catherine B. H. First Time Question Askers, Ariana Rose, Planet Silorraine, and Lisa Gorman, who asked, It seems like a lot of us. mammals in general could benefit from the ability to grow some spares. Okay, losing teeth. Lunar crumpet. and others. Why do some animals lose teeth?

And replace them like sharks. I see people in Florida, their beaches are lousy with these shark teeth. And I'm like, where are you getting these? Like who who are these sharks? Just shedding them, you know? Like cigarette butts. Why do some animals pop them out also?

Those x-rays of children that have a whole row of teeth in the wings. Terrifying. Those are real? Yeah. Oh Jesus. Oh jeez. So how come why do some of us retain our teeth for as long as we can and others are just like popping them off? Great question. Tooth replacement or constant truth replacement is the original state.

Once tooth replacement evolved, almost everything kept replacing its teeth. Oh. So salamanders replaced their teeth, reptiles replaced their teeth, everything, everything, everything until. And there's a couple of exceptions, of course, with full tooth loss. Like birds don't replace their teeth because they don't have any. So mammals.

basically reduce that to a really uh extreme extent where we only have the two sets, the baby teeth and our adult teeth, right? So the baby teeth are what you're seeing in those baby X-rays? Yeah, horrifying. Um terrifying, but they're just like in weight. Right. So they're like a full adult tooth made right above the or below the Current baby tooth and it's just like lying in wait and like waiting to arrive.

Many patrons had teeth on the brain, including mycologist Janet R., Dame Camacho, Emily Stoffer, Talia Duniac, CRH, and Nancy K. Clark. And yeah, by the age of three, most tiny people have all 20 of their baby teeth. with thirty-two hanging out in a jaw condominium upstairs. And if you've ever seen X-rays of baby heads or medical specimens, rest in peace. It look like a lotus pod. And if you don't have natal osteophobia, your then your tripophobia of holes will definitely kick in. Round nubbins.

Housed in holes. As your internet father dad word, I do not recommend Googling baby skulls in general, but definitely not in a packed cafe on a Sunday afternoon. full of matcha drinkers. I wanted to keep looking. I also had to close the tab. But yeah, summoning the tooth fairy. And that's what we have. Most mammals have just reduced it down to

To just the two stages, milk teeth and adult teeth. There's one theory that it's because of chewing. So our molars are shaped very specifically to fit together, right? And they perfectly fit together in this like. It's called precise occlusion. So just fitting together really well. Really hard to do if you're constantly changing your teeth. Oh yeah. So how do you have that consistent fitting together if that's not the case?

And so we think that maybe by evolving one they had to lose the other, potentially. But yeah, mammals basically we just have the two. Uh but people are working on it, right? Because we study sharks, we study all kinds of animals that replace their teeth constantly, because wouldn't it be nice? Instead of getting crowns, they just pull that one out, put like

a little stem cell implant right and then have that grow. And that's now in progress. People are doing that that with mice. They were able to implant a tooth bud and grow a new tooth. It was shaped a little funky, but it did well. It still did well. They're like it's a prototype. It's pr I'll get it next time. It's fine. I'll get it next time.

And the thing is, like teeth are really complicated, especially ours. This is why implants don't work very well. They still work, guys. It's better than nothing. But They don't work very well because they don't have the nerve and the blood supply and the pressure sensitivity anymore. So sometimes people bite too hard, break our their implants, et cetera. So yeah, it's just not it's never as good as your original organ, right? Yeah. You mentioned salamanders.

Hate me. Salamanders have teeth? Salamanders have teeth. Are they little nubbins? Tiny. Tiny Tiny, tiny little things. Eating bugs, eating ants, mostly worms. They're kinda like just velcro on the inside of the mouth so everything goes the right way and not out the other way. Because like salamanders also don't have a secondary palate. So the way they're breathing, the way they're eating, all that is just in one area. So you really want your worm to go down. Yes. Not back up. Right.

Yeah. What about snails have those like raspers? What are they called? Uh radulas? Yeah. Are those teeth? They are not teeth. Okay. We found the boundary. Um, and and how do we know they're not teeth? They're not made of the same stuff. They're actually keratin. It's like a little pad of velcro kind of thing, a little hook.

That's keratinized, yeah. Yeah. Not odontodes. Not odontodes, which are a vertebrate only thing. Yeah. So true teeth and odontodes in large start at vertebrates, no invertebrates. Yeah. They have similar things. I mean things you gotta eat, but just not an actual Odon toad. Going back to replacing teeth like sharks replacing teeth, it seems like that would be really expensive. to use those minerals to regrow. Right. But it was worth it because what, they would chip off a lot.

We assume so. That's a really yeah, that's a very good point. So why replace so many teeth?'Cause like you said, it's super expensive. Also maintaining bone is really expensive. So we always assume that something that is hanging around or has been successful through this much time has to be helpful. And the assumption is that yeah, they're probably chipping their teeth so much.

Also, mammals have really thick enamel. We have really thick enamel, but most reptiles, fish have pretty thin enamel comparatively. And maybe that's just because they're making them and tossing them. You know, or or the reverse is true. Because they have thin enamel, then they need higher placement. Do crocodiles and alligators lose their teeth?

They do. Oh yeah, they constantly replace their teeth. Constantly. Do you find them in f fossilized? Oh yeah. Oh yeah. They make up like chunks of the freshwater fossil. What about dinosaurs? Replace their teeth constantly. Shut up. Mm-hmm. Really? Because mammals hang on to them. Mm-hmm. D do you find a lot of dinosaur teeth fossilized? Oh yeah. Oh yeah, tons. Yeah, yeah, yeah.

Where do people ever just come across them? Uh if you're in the right place, yeah, absolutely. Yeah, yeah, yeah. If you find a dinosaur tooth, you should call a paleontologist though, right? Yeah, always call somebody or at least look it up, see where you're at, especially if you're like anywhere near public lands, you shouldn't probably be picking them up in the first place because the context is part of the science. So like where you found it, what's around it, et cetera.

Not all teeth are super valuable to science. So like a lot of shark teeth, we have just tons. Yeah. Um some some dinosaur teeth. So like I was working uh I was in Alberta for a bit and we found a whole hadrosaur dental battery. And hadrosaurs merge a bunch of these really thin leaf-shaped teeth into like a brick and then chew with the brick. Ooh. Yeah, because they want to like chew a lot of plant matter with multiple tissues at once.

Right. So they use multiple teeth at once to kind of chew and grind against this big brick of teeth. And so you find them all over the place because they fall apart when the animal is dead, because they were held together with ligaments. What about deer teeth and herbivore teeth? So herbivore teeth are really weird, particularly dear and

What is it, horses and camel, anything that eats a lot of abrasive material? Uh they use something called cementum as the how they attach their teeth. They basically chew on multiple tissues at all times. If you've ever seen like a deer tooth, It's like wavy at the top with like little pits. They want these cusps to be pointy and they want the pits to be deeper. And how you do that is have some harder tissues and softer.

And so that way you're like basically making a greater for the plant matter. Yeah. Do they replace those teeth or no? Those same as us, they're mammals. But rats and other lagomorphs. Do there's they keep growing to sharpen, right? So only their incisors and lagomorphs and rodents are very special in that. They don't replace their incisors, the front two like yellow teeth, but they grind them against each other to sharpen. So like people who have rabbits as pets.

will realize that like if I don't give them enough stuff to chew, now I have to trim their teeth, which is such a wild thing to think about. I know, right? No. But that's because they're ever growing. and they'll actually like curl and like grow into their own palates if they're not taken care of properly. But yeah, that's ever growing teeth. But the rest of their teeth, one set of milk teeth, one set of battle teeth. That's it.

I wonder if they ever swallow them when they fall out. Oh, sure. A hundred percent. Yeah, yeah. Dogs and cats do too. Yeah. Just poop mount. Yeah, yeah, poop mount. Comes right there. And if you wanna hear fun fact, rodent teeth lag morph teeth. Um, why are they yellow? Different material? More dentine? Iron, iron and their enamel. So much stronger. So much stronger. I love that they're not just dirty.

I'm so happy they're taking care of their dental hygiene and it's just an adaptation. It's not just turmeric, you know. But yeah, that's how beavers like get through giant trees without destroying their enamel. They have it on one side and Keeps that really sharp edge. Ah, just a bevel. Mm-hmm. So yes, we have an excellent urban rodentology episode with Dr. Bobby Corrigan all about sewer rats and why you should love them. In it, I cry.

as well as a cervedology episode about deer and a beaver episode about how and why rodent teeth are that striking sunset color and how one side of the tooth is iron enriched and tougher, leading to a kind of Shiv sharpening happening on those two front incisors. And for patrons thirsting for more knowledge, like Sonia Bird, Alexander Rambo, Lulani, and Chris Curious, uh please report to the Beaver and the Rat episodes at once.

So many good questions about a topic that none of us knew existed until today. Let me see. Can't believe you're doing this without caffeine. Absolute champ. Painful. I'm not gonna lie to you. Okay, just a quick dip into other animal teeth. Hats off to patron Sean, who prompted me to learn that marsupials are packing 40 to 50 teeth. with the extinct marsupial or pouch lion phylocolio having weirdo beautiful rodent like front fang.

Okay. Sean asked why are marsupial teeth so much different from most creatures we know? Do you find a lot of different teeth in areas like Australia that's just its own continent? And the bee asked, It seems that a common problem with human teeth is overcrowding. Specific to humans, or is there evidence of this in other animals? Like, do they have any wonky occlusion just like on accident? I mean yeah, pathologies happen, usually if something happened in childhood or depending on how

Poorly we bred them. See Bulldog skull. See Chihuahua skull. See a lot of domestic dogs and Persian cats. Um they just lose space and the genetics to make the teeth are still there and so the teeth keep being made. What am I supposed to do with these? But why do we have wonky teeth, right? One thought there's a few studies on this. because most animals don't have overcrowding. Most animals

have enough space for their teeth and that's been selected for pretty intensely, right? You gotta eat well. That selection pressure is probably lifted for us. One,'cause we're social animals. We feed each other, you know, we make mushy food for like b elders who do not have teeth anymore. There's ways that we adapt beyond needing perfect occlusion. The other thought is that we've through evolutionary time have softened our diets.

And having a really hard diet helps you grow your jaw bigger. And so like basically your jaw grows properly, has enough space and your teeth are not overcrowded. You know, people will counter that with, but I don't want to give my baby like a whole bone to chew on, which fair. I mean, choking hazards are not great. But look how perfect their jaw could have been. But yeah, it's thought to be potentially because of general softening of our diet. And with dogs when you give them bones to chew.

cooked no good because it splinters. Right. Are you cooking out these binding collagen fibers? Is that what's going on? Yeah, and you're weakening you're weakening the mineral bonds as well. So it just starts to like fragment. Also, like if you see a bone out in the sun, if you're like walking in the desert or whatever, it looks like almost wood. It like fragments so much.

Yeah, it's the same thing. It's the heat impact just slowly. Yeah. And we see that in the fossil record too. That's how we know if something's been buried right away or it sat out in the sun for a long time and then got buried. So you can see like Literally dinosaur bones that are like fragmented and look like wood. Ooh. I never thought about a skeleton.

being fossilized. I always just thought something just ate shit in the mud and then it was game over. No, I mean things die out there and then get flooded over or buried secondarily. Yeah. Okay. Danny the Dino. Because it's a dyno. Well, last Patreon question. What unexpected information can we gain from fossilized teeth? beyond diet, but I wanna know, diet wise, are you learning a lot about what they ate just based on their nubbins or their fangs? So on diet, we know a bunch about

what animals ate based on their teeth in general, just morphology, so people will actually quantify the shape and then be able to be like, Okay, this is best for this kind of diet or this kind of diet. But also, especially more recently, people are taking the enamel Analyzing the isotopes in there so Maybe you can explain what isotopes are? That is all I'm here for. So yeah, isotopes.

are atoms. They're kind of like siblings of the same element. So every element on the periodic table uh has to have an equal number of electrons, the very lightweight little orbiters around the center cluster or nucleus. And the nucleus is made of positively charged protons and neutrally charged neutrons.

and those are the same weight. They're much heavier than the electrons. So the number of electrons and protons have to be the same. But an isotope is the same element But kind of like the sister, it has a different amount of protons and neutrons, so its mass is a little different as an isotope form. And an isotope can emit radiation or not, but they are helpful in paleodetective work. But um Basically they can find isotopes that link to diet. So now we know that some

Dinosaurs were eating like C four plants or like this type of plant, or we know um they ate more seafood because that has a different type of isotope. So teeth Shape wise will inform diet, chemistry-wise will also inform diet. Super interesting. And this is in their tissues and not just like plaque around it. Correct.

Yeah. It's the actual enamel that holds onto it because basically these animals are replacing their teeth all the time, right? So constantly whatever they're eating is what's getting incorporated into their tissues and then expressed in their enamel as they make new enamel. So it's kind of like a continuous dental history, d uh continuous chemical history. Well, you are what you eat. Um, okay. The most annoying thing about your job. I'm gonna can I guess? Yeah. I'm so curious. Funding.

Funding or Do you get emails from people who tried to convince you that dinosaurs didn't exist? I don't, although my last, my most recent paper did get covered in a creationist uh article. What did they say? Well, they said that I needed Jesus. They said that um what is it? Teeth have been around forever and therefore my study was wrong and I hadn't considered this and that and that I need Jesus.

Which is pretty funny. I think it was like one of the only citations we've gotten for the paper so far. But yeah. It's now it's it's a pretty new paper, but it was hilarious. It was pretty good. I can send it to you. It's hilarious. Yeah. So bizarre. Okay, let's dive into her twenty twenty five nature paper, once again titled The Origin of Vertebrate Teeth and Evolution of Sensory Exoskeletons.

We synchrotron scanned diverse extinct and extant vertebrate and invertebrate exoskeletons. We find that the tubules of anatolept have been misidentified as dentine tubules and instead represent a glaspated arthropod sensory sensilla structures. What does all that mean? Let's gossip about it. And so One of the things I really wanted to look at was this early fish from the Cambrian

And so people found it and thought that this was the earliest vertebrae. And I was like, great, we're gonna image this thing with this all this new methods that we have. So I now use a particle accelerator to image fossils. No. I don't know if you've heard about those. No. So synchrotrons are these rings that you accelerate an electron in, and then you basically shoot x-rays.

from the bending of those two fossils. And it's basically like a hundred billion times stronger than your doctor's x-ray. Really strong. Strong enough to get through rock. Oh my god. So people use it for like batteries, people use it for all kinds of things. We used it for rocks and I was like, okay, I want to shoot these really early fossils. Let's see if these like early fragments really are teeth, because then that would pull back.

The record of mineralizing vertebrates from middle Ordovician all the way back to the late Cambrian. And it would be my transitional fossil that I was looking for, right? Oh my god. This is what I pitched.

to come to U Chicago and I was like, This is really what I wanna do. The fossils exist somewhere, let's go find them. And so they'd been published on before in the nineties seventies and then again in the nineties and they were like a big splash every time because brand new early vertebrate. Mm-hmm. We scanned them and I was like, Great, this really looks

Like a tooth. These really look like little odontodes and a piece of bone. Wonderful. We have brand new, really beautiful 3D images. Gorgeous. Okay, great. I dig into the literature some more, and at that time, even when they originally published them, They thought maybe these are not virtual. But maybe these are arthropods.

Because remember, we just spent the last hour establishing that invertebrates, like arthropods with their exoskeletons, do not have odontodes, right? We know those words now. So why are we seeing? And everyone who said it was an arthropod kind of got like brushed aside. And another paper came out that used paleohistology to prove that they were vertebrates. And how they did that was they cut up these little fragments.

And saw the inside of the odonto and they saw these tubules inside the odonto. And so they were like, this is dentine. And dentine is only found in vertebrates. And therefore it has to be a vertebrate. Slam dung, big deal. And everyone's like, Okay, great. We now know this uh late Cambrian fish thing, fragment thing is a vertebrae.

But I was like, okay, I want to scan it. Now that we know it's a vertebrate, let's get a good 3D structure of these earliest teeth. When we scanned it, I was like, great, this does look like a tooth. And then I started reading some more. And I was like, well, the people who originally published. that it was an arthropod are really good scientists. And I respect these people. And What if they were right?

What if? You know, so we scan some arthropods to compare tubes and we start scanning these arthropods and we see tubules. little little tubes. And so these arthropods have also bumps on their skeleton and we're like, this is odd. And each bump has tubules and it's really hard. And we're like What if? So we scanned a bunch of arthropods and basically, long story short, found out that this late Cambrian guy was not. A vertebrate. No. At all. But an arthropod.

So what does that mean? Exactly. So what that means is that we don't have our transitional fossil. We don't have the guy in the middle. We still have this giant gap between squishy boys and fully armored fellows. And that was really weird. And it really bothered me. I was really upset. Yeah. I was like, oh no, my tooth, my earliest tooth. Oh no. Um But even at that moment I was like, why does it still look like a tube?

Why are these arthropods covered in things that look like odontodes? Yeah. And what are they? What are these like weird bumps that look like odontodes on an arthropod versus a vertebrate? Yeah. So I did some deep digging, read way too much about Arthur Poggs and found out that there are these things called sensillae. Mm-hmm. sensory structures that are super diverse. So like think of

like a fly that lands and he's like rubbing his little legs and there's hairs all over it. Like you know, the movie The Fly. Yeah. Yeah. So that's a type of sensibility. That's a mechanosensor one so it can sense the deflection as they move. Um there's chemistry ones like chemosensory ones, so they touch the ground, they taste the ground every time they land.

But that's what sensile are, and that's what we found on this ancient arthropod from the ladies' Cambrian. It was sensory organs all over their body. And so we're like, oh That's really bizarre. So this is really intricate sensory network of like bumps and stuff on arthropods. Fantastic. I go and I tell Neil, my supervisor, and I'm like, hey, I think they're this. And he's like, oh.

Well, that kind of makes sense that they look like teeth, then that makes sense that they look like adontodes. I'm like, why does it make sense? And he's like, Well, because teeth are sensory. Odontoids are probably sensory too. And I was like, How do we prove this? How do we actually test? Odontodes, which are outside the mouth are are sensory the same way teeth inside the mouth are. Yeah. So you know your your teeth are sensitive, right? Of course.

You're having uh some issues with that and light and like a lot of us do, but it doesn't really make sense. Why would you chew with these super sensitive structures? Yeah. That was always such a bizarre thought process. But then you look at all these different animals that use their teeth as sensory organs. Elephants touching the ground, narwhals.

Uh with their giant like horn, it's not a horn, it's actually a giant tooth. Bonkers. Bonkers. And they sense all kinds of uh temperature changes and wave changes because their dentine is sensitive. Dentine is our sensitive tissue. That's why if you take care of your enamel and your gums, usually your teeth are okay. Mm-hmm. Because when your dentine is exposed, it's the sensitive tissue. Oh no. Okay. So now we know odontodes have dentine and we know that teeth have dentine.

But we don't know if adontodes outside the mouth are sensitive. And so this is where I took a really weird tangent that I want to tell you. So remember when I told you that sharks have odontodes, they're covered in these little little bits? The other ones that have odontodes are catfish? And so you know like a little pleco, those like algae eating little fish that you get in your aquarium. Yeah. So those guys are covered in Adontos too. They're covered in little teeth. What? Bizarre.

And they are super easy to keep and super common. So I went to my pet store and I got a bunch of them. Oh my God. And started breeding them in the lab to get their little embryos. So we could actually test if their dontodes are innervated. Because that would be the first step for them to be actually sensory. If the odonto has nerves going to it, then at least that's step one of it being innervated. And these odontodes in our early fish from the Middle Ordovician.

Have pulp cavities. And pulp cavities are where the nerve goes. And we were able to trace it all the way down to know that like there had to have been a nerve. But do modern odontodes outside the mouth Have nerves. So went, collected a bunch of these algae-eating plecos, learned how to keep an aquarium, because God knows I never had an aquarium, and bred a bunch of these little fish.

And then we use this amazing uh method called clarity where you make the little embryo super clear. You basically remove all the fats and lots of the proteins, and then you add antibodies that attach only to nerves, and then they have a fluorescent probe, so they glow under a microscope. And so you bathe them in these antibodies and you put them under the microscope and then they glow wherever the nerves go. And you can trace every nerve to every odontos.

all their dontodes were innervated right into the pulp cavity. No. And so when they're in the aquarium, are they like, oh it's a little cold in here. Is that what they're feeling? Is that they fight with them. What do they do? They have Chica dont are on this like Catfish are really weird guys. I'm just gonna side note everybody. Uh I think what is it? One in five vertebrates is a catfish. No. Please check me on that. Yeah later told me that she meant one in twenty or five percent.

Of all vertebrates are catfish. One in twenty vertebrates on planet Earth are catfish. What the fuck's going on? So yeah, we need a catfish expert for a cilia formology episode. And yeah, I think it needs to be a two-parter addressing internet scams as well. Maybe five percent of vertebrates on dating apps are bots. Who knows? Anyway, actual real slimy Perfect whiskery catfish. Their diversity is wild. Yeah. Yeah. They did really well for themselves.

Not all of them have odontodes, but these little algae-eating ones do. And they have them all over their bodies, all over their fins, all over their cheeks. And they ram each other with them. Um they also send them. their environment all the time because they're bottom dwellers, right? So they're always feeling the bottom and they're tasting with taste buds in between their Adontos. They taste their environment. Have you ever wondered when you like

If you put a little bit of food somewhere in your aquarium, even if it's far from your fish, they'll know where to get it. That's because they're constantly kind of tasting their environment. With taste buds in between their outside teeth. Seems that way. Yep. Why don't sci fi movies just do a biology? Just do a biology. Yeah, just do my Horrifying and amazing.

Yep. Yep. Yikes. And so what happened when you were writing up this paper? So it was like a bunch of different parts, right? We we made a arthropod library where we did comparative stuff. We found out that they were sensillic.

Then we did a bunch of stuff on sharks and catfish to find out that the odontodes were innervated and then tied it all back to the Ordovician vertebrates. So this paper we basically said the late Cambrian Supposed vertebrate is not a vertebrate, so we kicked that out, which meant that now our true earliest mineralizing vertebrates are middle Ordovician, four hundred and fifty or so million years ago. And we finally have a little bit of proof.

that the external Odontodes were not only for pr uh protection, they weren't only for being armor, but they could have also helped our ancient ancestors with sensation. And that maybe that explains why our teeth are sensitive in the first place. Maybe it's because it's an inherited complexity from their original. Gonna tell my dentist about this. Do you dentist? I tried. I just had a tooth cleaning actually last week and I'm like

Hey, I was so happy'cause I'm proud of my paper and I'm like you wanna know something? And they're like please don't. mouth. Like, please, please, ma'am, ma'am. They shut me down so quickly. You're like, you work with teeth, I work with teeth, slightly different era. Yeah. Everyone. Pass this on to your hygienist.

They deserve cool facts and a lot of praise. People should know. But yeah, uh we were talking okay. What were we talking about? Uh but no, I would say the hardest part that was the question, right? Hardest part about my uh job is That I have to keep thinking about ancient fish while the world is doing what the world is doing.

Yeah. Yeah, that I think that would be the hardest part. Funding has obviously uh become a problem recently for a lot of scientists, particularly natural history, particularly life science, uh earth sciences. It's just, you know. When everyone starts to panic, they think that it's time to cut science. And that's actually the worst time to cut science. Um, in general, because we need to preserve these things. New discoveries are how we get out of economic downfalls, et cetera, et cetera.

That's always sad. But I think the hardest, hardest part is just l I guess I think about old bones today, even though, you know Bombings are happening or uh economic crashes are happening. Um and then the system that's supporting me and celebrating me is also the same one that's upholding all kinds of other issues. So yeah, I think that Just you're like a head down, yep, don't mind. The wars, the genocides, the climate change. Yeah. And and that's tough.

Yeah. Uh the way I get over that though is like through stuff like this. Science communication. I really do see a difference when you talk to people. Most people haven't met a scientist. I sure didn't until I was like about to become one. Mm-hmm. So I don't want to leave it all doom and gloom because like I push people I think the real solution to this is more people interacting.

Just go to your museums, go to your universities, go volunteer for whatever invasive weed thing that people are removing from your local neighborhood, interact with science as much as. And there's always community science too for people to join. Yeah. Right? Totally. And there's like big science fairs, big volunteer opportunities. Yeah. Get in there. Yeah. But um I mean I how do you even

Say what the best thing about your job is when you're getting to look at all this cool weird stuff. What's your favorite part? What gives you like uh Odontoed Goosebumps? Ooh, Odonto Goosebumps. Disturbing but accurate. Um I would say Like looking at the tissues under a microscope, realizing that you're the first person to see this animal since it got buried.

You're the first person to put these things together. Fossils, just like the actual physical objects, the fact that they exist is amazing. The new methods, the people I work with. Like I love my job. I love my job. I want everyone to experience the feeling of finding their first fossil because that's it's so weird to just crack open a piece of rock and be the very first person to look at this bone since it was buried 480 million years ago. Like that's such a bizarre feeling.

And if you literally sit with it and you let it like permeate your being, um, you realize how special that's. and how small we are. And kind of making ourselves small, I think in many ways, like I don't know, i i it makes you feel like you're part of a big system. And and time and the earth and all of that comes together to make this particular moment where you're seeing this.

It's just weird. Discovery is always so, so interesting. The amount of mental freedom that we have to ask strange questions and go down strange rabbit holes, it is uh ADHD or is like Dream, which is why there's so many of us in academia. Yeah. Right. Yeah. So I mean, I Um, when you think about things in the long term, existentially, not to doom and gloom it, but if you could fossilize yourself after death, would you like do you wanna keep your bones around? Or are you like

Throw me in the ocean, burn me up and grind me up. I would think about bones differently where I'd be like kinda want my skull to be around afterwards. You can donate to science. Um and then you know, you'll probably end up like a cadaver in an anatomy lab and that's always really, really helpful. Uh sometimes you'll end up as a teaching skeleton.

I don't know how to end up as a teaching skeleton, but I would love to end up as a teaching skeleton. Yeah, wouldn't that be cool? It would be so cool. I I don't find it like

Obviously, I mean I I work with bones all the time. I don't find it grotesque. I find it so fascinating. Yeah. That like everything's such a different shape and you know, my skeleton can be hanging around in a classroom staring at students forever. I would love that. I think that would be cool too. Now that I've been talking to you about bones, I'm like

Kind of more into that. Yeah. If they can use me. Or just put me in a mud flat and uh And let let the octopus aliens find me. Yeah. I'm with you. Just a little peace sign in a mud flat. Perfectly flattened. Yeah. Slap me over. Yeah. No copping, please. Just wet, wet mud. Uh this is a joy. And I'm so glad this has been Six years in the making? At least. At least. At least. And now you're doctor. Thank you for having me at this beautiful, terrifyingly uh dark maze of cabinets.

So ask informed people unabashed questions because their skulls are full of good stuff. Thank you so much, Paleohistologist Dr. Yara Haridi, for opening up the stacks at the Field Museum for this visit. changing the way I gaze at my own teeth. And for more on Dr. Haridi, her website is yaraharidi.com. Her Instagram is yara underscore haridi. And we'll have more links to the studies and the some here project.

at alleyward.com slash ology slash paleohistology. And remember we also have kids safe, classroom appropriate cuts of ologies classics. They're out every week. Just search Smology's S-M-O-L-O-G-I-E-S and subscribe wherever you get your podcasts. We are at Oligies on Blue Sky and Instagram. I'm at Alley Ward on both.

Ologies Merch is available at ologyesmerch dot com and to submit questions before we record, sign up for a dollar a month at patreon.com slash ologies, the lovely Aaron Talbert admins the Ologies Podcast Facebook group. Aveline Malik makes our professional transcripts.

Kelly Rdwyer does the website. The smiley Noelle Dilworth is our scheduling producer. The web holding us together is managing director, Susan Hale, and working as a set to chew through the edits are Jake Chafey and lead editor Mercedes Maitland of Maitland Audio. Nick Thorburn made the theme music, and if you stick around until the very end, you know, I'm gonna tell you a secret. And this week

It's two. So one app I've been loving lately is called Doodle and I'm not getting paid to talk about it. It's in beta right now. It gives you a prompt every day to doodle something. And then you can see what your friends or strangers doodled on that same prompt. And it's a very fun, low-key way to just make something no stake. and let your brain be goofy and creative. Once again it's free. It's called doodle.

No E on the end. And my wonderful friend Stephanie is the designer. I think it's a genius. I'm on there as Squirrel Hat with a K-S-K-W S-K-W-U-R-L hat, I think. And my profile picture is a bat face. Um, again, not getting paid, doodle, just love it. Second secret, which is a bit more vulnerable. I feel like I'm gonna regret this as soon as we hit publish, but. I used to act on TV. That's how I got my health insurance.

And I once had a bit part on Gray's Anatomy on an episode called Something to Talk About, in which I play a pregnant wife with a mysteriously pregnant cisgender husband. So if you would like to learn some dramatized medical trivia, do enjoy that. Don't make fun of me too hard. Also the belly they had me wear was like a pantyhose big girdle and it was filled with like ten pounds of birdseed and it was fun to push it with my finger. Also I had baby bangs and blue black hair, so enjoy that.

I can presenter Gjud av förändring. Du. Vi måste prata. Med Ving kan du skräddar sy din resa, sol och bad, storstad eller kanske till ett paradis långt bort. Upplevelser som är lätta att älska. Svåra att lämna. Boka en semester du inte vill hemfrån. Se våra bästa erbjudanden på wing.se.