Ologies with Alie Ward - Paleohistology (WHY TEETH EXIST) with Yara Haridy

Episode Date: January 21, 2026

Excuse me, why do you have teeth? How did they get in your mouth and where did they come from? Let’s ask researcher, tooth enthusiast, and Paleohistologist Dr. Yara Haridy.  She opened up the archives at Chicago’s Field Museum to chat about ancient skulls, drawers of bones, and the evidence that changed how we think about chompers. Drop your jaws as we discuss the origins of teeth, why yours hurt, the long-debated rumors of extinct species, how particle accelerators and paleontology worlds collide, what tools fossil pickers rely on, teeny tiny mysteries, why you should hug a tree before it kills you, and why a catfish might become your overlord. Visit Dr. Yara Haridy’s website and follow her on InstagramA donation went to the Sameer ProjectMore episode sources and linksOther episodes you may enjoy: Osteology (SKELETONS/BODY FARMS), Selachimorphology (SHARKS), Elasmobranchology (MORE SHARK STORIES), Paleontology (DINOSAURS), Evolutionary Biology (DARWINISM), Functional Morphology (ANATOMY), Genicular Traumatology (BAD KNEES), Castorology (BEAVERS), Urban Rodentology (SEWER RATS), Biomineralogy (SHELLS), Scorpiology (SCORPIONS), Garology (LONG CUTE ANCIENT PATIENT BOOPABLE NIGHTMARE FISH)400+ Ologies episodes sorted by topicSmologies (short, classroom-safe) episodesSponsors of OlogiesTranscripts and bleeped episodesBecome a patron of Ologies for as little as a buck a monthOlogiesMerch.com has hats, shirts, hoodies, totes!Follow Ologies on Instagram and BlueskyFollow Alie Ward on Instagram and TikTokEditing by Mercedes Maitland of Maitland Audio Productions and Jake ChaffeeManaging Director: Susan HaleScheduling Producer: Noel DilworthTranscripts by Aveline Malek Website by Kelly R. DwyerTheme song by Nick Thorburn Hosted by Simplecast, an AdsWizz company. See pcm.adswizz.com for information about our collection and use of personal data for advertising.

Oh, hey, it's your neighbor's Wi-Fi network that shows up as New England clam router. Allie Ward, and we are biting up just enough to chew about ancient 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 you, it's like a little corner of the earth in time you'd never otherwise imagine unless you are this ologist or one of their colleagues, paleontologists who study fossilized prehistoric tissue samples. I love this.

This ologist, 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 premed at the University of Toronto before getting a master's in ecology and evolutionary biology there, studying animal jaw bones. 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 and evolution of sensory exoskeletons that's like shaking up the fossil world. And in addition to being a professional paleontologist and an evolutionary biologist, there 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 going to 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 ologiesmerch.com. As a reminder, also, we have a shorter kid-friendly episode suitable for all ages and classroom safe, and those are called Smologis.

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 reads books, who said that ologies, quote, can make the most obscure, weird topic super interesting. Coco, you have no idea. We're about to do it again. Okay, paleo histology. It comes from 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 ologist. 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 mouse. 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 flimplam, and why you should hug a tree before it kills you. Plus why a catfish might become your overlord with science communicator, researcher, paleontologist, tooth enthusiast, and researcher of ancient tissues, paleo-histologist Dr. Yara Haridi. First thing I'll have you is if you could say your first and last name and the pronouns you use.

So I'm Yara Haridi. Dr. Haridi. Dr. Haridi? Dr. Yara Haridi. She-her pronouns. When did you defend your PhD? I was officially awarded to me in January 2020. Yeah.

I followed you on Twitter for years. Before. Before. Yeah, in the before times. In the before times. I reckon it was Twitter when that's where all the scientists gathered. It was such a beautiful time. It was a beautiful time.

I got to know your work. And I always love that whenever someone found a raccoon skull under a shed, they would tag you. What is this? I did become like a go-to bone and tooth person, which was my goal in the first place. And honestly, it's so sad because I used to suggest like social media as a go-to thing all the time. Even for like young people, like young people who are trying to get into science because it was such a good resource. You know, 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 got friends. I got, you know, all that kind of stuff. And it was a really, really beautiful place. Hopefully science will come together again somewhere else. Nothing but blue sky. So I am excited to catch up with you because I wanted to have you on for so long.

Now, okay, the ology itself, I saw that you have a paper, histological skeletal chronology. That's a possibility. Paleo-dentology. 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 paleo histology is just the study of ancient tissues.

So histology is just literally the study of tissues. And then paleo histology, you just make that ancient. Old, old, old. We're talking tissues, but we're also talking teeth. 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 tooth. And take me back. When did you start getting interested in paleontology? Oh, girl. 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 knew. You know, 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 1994. 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 what I decided to go into a science and try to at least go into being a doctor, so I 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 of paleontology. And yeah, a couple of right turns turned left or a couple left turns turned, 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 structures? 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 280 plus million years old, which 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 tissues. And I didn't understand what that meant at the time because what do you mean tissues survived in these 280 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 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? How does it grow its teeth? All that was still preserved. And at that point, 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 science 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 takes it's and it's not 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 imagined hard bones that survived and everything else rotted out. Or scales something. Something's still hard. Something's still hard. Yeah. Something with a structure to it. And that's fair because that's the vast majority of fossils. That's like 99.9% 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 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? Okay. Yeah, yeah, yeah. So fair, right? That's kind of the old thinking of like, well, it's just an impression, like the scales, for example, like how to, you know, like dinosaur mummies and stuff. Sometimes they are impression. 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 cross-linked 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 extrapolate that even more, it's like, when did things start getting mineralized tissues?

Okay. So we have this process called biominerization 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. Calcium carbonate skeletons. Arthropods have exoskeletons. So just taking stuff from the environment and making your own skeletons. 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 fossilized really well. And so we can go. 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 on it? 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 455 million years ago. Woof. Yeah. Hard to kind of conceptualize. Right. So dinosaurs won't extinct when? Oh, 60. 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 teeth. Were they ever made of cartilage and get harder or they were always mineralized? Did animals ever have like kind of gummy like like kind of like teeth? I love. Did they just gum things to death in the ocean? 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 of fish. They appear 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, you have like a handheld vacuum that you're going to like clean your car with. They look like that, but stick googly eyes on the end. Oh, no. 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 going to be using often. So odontodes are little chunks that basically look like a tooth, but they're on the outside of the mouth. They're made of enamel and dentine, and they have a pulp cavity. But they cover the outside of fish rather than being inside of the mouth. It sounds like a teratoma, you know?

Yeah, yeah, totally. A blob item with T's sticking out everywhere. But what did they use them for on the outside? Boom, exactly. We don't, like, so we don't know or we didn't know. 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 hardened scales that cover their entire bodies. Makes it harder for things to bite you. Yeah. Makes it harder for parasites to get attached,

et cetera, et cetera. Please, please see our Gorology episode about long, cute, ancient, patient, boopable nightmare fish with the iconic biologist in punster, Dr. Solomon David, as well as our Teratology episode about the history and culture of monsters and fiction

because 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 grotes. Yeah. But if you think about like modern sharks, modern sharks have teeth outside the mouth. Or they have these odontos. They're covered in 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, is because they have little tiny teeth all in their skin.

Those are adontotes? Yeah. Exactly. Hovered 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? Merging into the hole. Should we go back to the, what are they for on the outside? Yeah, right, right. So there's a couple 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, nautaloid-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 protection. 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 the first ones didn't have pectoral fins. They just had a tail. It's like a tube. Like I said, it's a 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 in their skin, these little little little.

teeth on the outside, there are dontoads, to help basically with hydrodynamics. The way that the water flows over their body is more efficient because of the little bumps all over them. So maybe the early fish did that too. So that's one and other theory. And then the last theory is that maybe it has something to do with sensation. That may be because our modern teeth are sensitive, maybe the outside ones are as well. How big were these outside ones? Were they teeny or were they like I should just show you. They're in the cabinets behind us. Yeah. Grab one.

Yeah, yeah. Yeah, yeah. 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 odontode 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 Adjol's fish. And what you can see here, all these little bumps each one of them is a little tooth No it looks A dontoed

It looks kind of like a tiny cottage cheese ceiling You know Yeah yeah the popcorniness of it They're like little tiny beads Almost And now you clarified That you have gotten flak

Here and there We're calling you a tooth 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 origin. So 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 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 try.

And then they started coming, merging. They started saying, let's get in the hole. So how did we get teeth in the mouth? Or 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. We assumed 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 helmets. 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 U.S. in 2023, but unprovoked sharks killed 10 globally. Only two of those were in the U.S. Sharks are the eldest daughter of our planet. And so what we have is a couple of fossils that are covered in these little bumps all the way across

their face and right at the margin of the jaw, which had now evolved, you have sharks. and pointier adon toads. And they kind of grayed into the mouth, and then you have actual pointy things in the mouth, based on ostensibly teeth. 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 adonotodes,

they got re-expressed inside the mouth. Oh, okay. Right. 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 going to express it in the mouth instead. Kind of 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 dent.

Does that mean there's no enamel or pulp? So tusks are just teeth, but they're fancy teeth. in that they are usually non-replacing. They're usually continuously growing. So elephants are the famous tusks, 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 them 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 is so hard? Well, I think it's just to get worn away after a while. 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's some kind of feedback that 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 tissue. 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. or working on it. Our pack of dermatologist 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, sweet little brats. And this is one thing in a recent paper of yours about sensitive teeth, like blame your fish ancestors. Yep.

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 it's just a guess a time mentioned. 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 sweet sensitivity.

So they just eat like a candy and they get sensitivity from it. I mean, you know, you felt like if you press really hard on your teeth, you can feel them. I know you just pressed on your teeth. 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 cold. 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 sense for like, hey, it's warm water or cold water or a change in tides or something. something's trying to bite me or the sediment flow changed or any of that. We don't know exactly what they're sensing, but we know that some kind of signal was getting past. And then tell me a little bit about this paper. 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 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, which tends to be a lot more interesting. So I basically had pitched to come to Chicago, to do my work at University of Chicago, I pitched, hey, I want to look at the very first thing in the fossil record that might have adon toads 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 Pangaea 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 2025 in the venerated journal Nature titled The Origin of Vertebrate Teeth and Evolution of Sensory Exoskeletons. And it reads, 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 oardivision. The latest 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, tiny. Like fits on the end of a toothpick tiny. Oh, dear.

Yeah, oh, dear is right. 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. I should show you. Do you want to see? Yeah. What you got?

Oh, teeny, teeny, teeny. And I got Heather actually gone 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. Do 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're like grape nuts. Yeah, they're tiny, tiny. And we get really good data from them. Oddly enough, they scan beautifully, they section beautifully. Under our microscope, they're just gorgeous. And the enamel's intact. Every one of those little bumps is a little adontoed.

Every single one. So the adontos 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.

Do you really? Yeah, we use dental tools all the time and dental putty to like make molds and stuff. Yeah, I'm friends with a lot of dentists. I hope you have a good dentist. I can't believe how teeny is. So I just opened another vial and poured out another bunch of stuff. crap. But this one's supposedly from a different species. And so you can kind of tell because the shape of the adontodes is different. 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 475 million years ago in what is now North America. And then once 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. There is one partially articulated head, which is only a couple of centimeters wide. Then there's another one that's like,

a bit bigger. So we don't know if what we're catching as 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? Paleo histology as a whole or looking for tiny teeth like this? Probably a handful, probably less than 10 of us. Yeah. Are you guys on a WhatsApp thread? 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 shapes. 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 boys. There was all kinds of squishy early vertebrates. And so I'm really interested in the jump from gooey things that were our vertebrity ancestors, chordates, etc. 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 because 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, 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 fieldwork 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 two 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 Ordovician. 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. So we've been out there digging.

Yeah, the whole thing. 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 want to see what a face of these weirdos looks like. Does it have a tail? You know, all that kind of stuff. So we weren't able to hit that just yet, but we'll go back soon.

I remember talking to Michael Habib and asking about how much it cost for a dino dig. And he's like, guess. And I was like $2 million, $3,000. He was like $10,000. Yeah. And I was like 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 going to dynamite something and you're like, oh, there's so much of this stuff in there? Do you have to choose like, I'm going to put this on hold and I'm going to 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's all of life, right? You have to kind of move things around and we prioritize.

So when we found out that this area was getting dynamited, we want to check it out, move to a bunch of things aside, and went and checked it out. But like Habib 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, my last fieldwork 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 science.

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-knobbing 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. can be a lot of hours of manual skilled labor. And people have funded that. People have found ways to fund that. They did that for Sue. Like, how do you fund the preparation of this giant Trix? It's a little bit easier to sell a Trix than it is to sell a jolless floppy fish covered in teeth. My children are not loved.

Oh, your gummy boys and your bloopy. Yeah. Finless things. Can I, I know we have so much more to cover, but can I cover it with Patreon question? Absolutely. Okay. Let's see what they've asked. But first, let's donate to a cause of YAR'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 Warm 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 Ghazan displacement and mass deaths 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 ologist's hearts each week. 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 Tomsk had a whale of one, as did. Mouse Paxton, Spicy Native, both wanted to know. In Spicy Native's words, baline, when did it evolve? Is whale baline, mouse asks, considered tea? Ooh, is a very good question. What is it? I thought it was carotinized, right? You're right. Okay. Yeah.

So not a teeth, not an odont. You got it. Odontoin. Adonto. You got this. Why can't I do it? Because you're not believing in yourself. No. Odont toads.

Odentodes. Odontodes. Yeah. It's fine. I knew it this word. We'll get it. We'll get it, guys. No, you're absolutely right. 10 points for Allie. Okay. That they're totally carotinized. And so if they're keratinized, they don't have dentine.

They don't have enamel. And so they're not. Odonto. It did it. I did it. So proud of you. Thank you. Yeah.

Okay. So great question from your listeners. Leoline is not teeth. It is a 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 both. Maybe.

Yeah, so baline whales came from toothy ancestors. They came from whales that have teeth. And so at some point, they started losing one and gaining the other. And that is quite like a controversial topic because I think there's like one team that's like, no, they lost teeth first and then gain baline. 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. Are, do you think all that extra vascularity, all that extra blood supply around the lip of this certain fossils, is that because of baleon?

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 balian evolved. But I think people are getting closer. There's a lot of really cool new fossils in that time period. Could baleen, because it's keratinized, be sort of like hair that's like just hanging out in the mouth? I mean, so keratin is incredibly diverse tissue.

Because our skin has keratin. Our hair has keratin. Our nails have... So it can just be expressed anywhere, really. And I'm not a whaleologist. But I think they probably just re-express 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 question. We still haven't done a setology 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.

My and Marlow, Planet Silorraine, Empress of Smallwood, Tinas, want to know. Ryan asked, are bird beaks teeth? Ooh, bird beaks are not teeth. That's another keratin structure. But birds did have teeth at some point. Do they not have teeth now? No birds have teeth now. Oh, okay.

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?

No. No. Birds kind of like do a grab and swallow. Because I got the crop. They got a crop. They also have like sometimes little keratin horns on their tongue 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 kind of hard to imagine how beak and teeth coexist. Like does the tooth keep growing through the beak? Oh.

Oh, yeah. How do those two tissues merge? I'm not saying it can't happen, but we just, so far as we know, things that have true beaks in the fossil record do not tend to have teeth, at least 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 rampathica, which is the fancy word for beak.

So when you get attacked by a goose or killed by like a cassowary, casseroi, casseroi, they're gumming you with keratin sort of? So, I mean, a goose is going to like, you can take a goose. Guys, most of you can take a goose. Don't upset the geese, but you can take a goose. You'll see like little bumps on the goose's beak. And that's just keratin, like, sticking down. They're not true teeth.

And a cassowary is not going to kill you with its beak isn't going to kill you with its foot. Again, another keratin structure. Don't mess with casseroys. You can take a goose, but you can't take a caswallery. No. Don't do it. No, don't do it.

That's one of my biggest fears. Cassowaries? Yeah, just getting in a accidentally getting in a situation where we're one-on-one and knowing I'm cooked. Because I just know, I would give up instantly. I'd just be like, a grizzly, I'm like, maybe I could boop in the nose, but I can't boop. that thing in the beak or you're nuts you're nuts i don't know i would take a casseroe over grisly this is a good

question it's a great question i'm gonna i'm gonna take a poll would you guys take a cassowary or would you take a grizzly i don't know that's a great question i got to figure out too if castoraries could fly i don't think they can't they can't yeah okay not even up a tree okay no no grisly can't go still okay also castaways are such good dads the dads do most of the caretaking they're so sweet okay cuties hang out with the casseroys yeah yeah no not the grisly i went down to a detour looking for a cassowary expert because according to my friend, Wikipedia, cassoiris 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 cassowary 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 Y, Y, Y, Z want to know about bone density. Do you think from a histological perspective, do you think that hormones were affecting these structures, like these odontodes, I said it?

Louder. Odontodes. You killed them. I had no caffeine today. And I also. Why don't we do coffee first? I don't know. I don't know.

And I will also plead. 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.

It 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 101. 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 the bone. So we have an osteology episode all about bones and donating yourself to a body farm, but I'm going to 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 when that? 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, yeah, one astronaut to space and left his twin on Earth, came back and I think he had lost some crazy amount of bone density. And it takes them 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 multi-dimensional analysis of a year-long human space flight. For the record, I have never, I looked at this paper, I've never seen so many co-authors on one study. I squinted counting, 84 of them. And I might be one or two off because 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, Scott and Mark Kelly, both astronauts,

Mark Kelly, yes, an astronaut and an Arizona state senator, husband to Gabbygifords, it involved physiological, telemetric, transcriptomic, epigenetic, proteemic, metabolic, immune, microbiomic, cardiovascular, vision-related, and cognitive data that were collected over 25 months. And it found changes in telomere length and epigenetics, changes in gut biome, body weight, rotted 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. weight because they don't have osteosites, 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 a 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 whole.

from forming. That's kind of how our teeth try to react to cavities because you really don't want to hold right to your nerves, which are in your pulp cavity, which is why your teeth hurt. Yeah. 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 nightguard, but he can't really talk with it yet because 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 garters, you're not alone, you're doing great. So patrons asking about historical tooth decay, Katie Elmer, Emmettie, Rot Weiss Waffle, Han the Bee,

Kim Grineer, Erevector, Empress of Smallwood, Mariah Walzer, and Deli Dames. This was a good question. Also, everyone, you got to brush your kitties and doggies teeth. We love their disgusting devil breath, but you've got to get in there, rub them with a little 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 adept patient 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 flim-flam, they ask? As well as Lori Fulford, Wynn, Rebecca Smith, Megan Walker, Naomi Jane, Alyssa McElroy, Catsay, Alexandra Rambo. Sheila Marita, Honey Pie, Tom Budry, Catherine B.H. First-time question askers are Ariana Rose, Planet Sin Lorraine, 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 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, geez. Oh, yeah. Oh, geez. 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? So, great question. Tooth replacement, our constant truth replacement, is the original state. Once tooth replacement evolved, almost everything kept replacing its teeth.

Oh. So salamanders replaced their teeth. Reptiles replace their teeth. Everything, everything, everything, until mammals. 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 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. 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 erupt. Many patrons had teeth on the brain, including Michaelologist Janet R. Dame Camacho, Emily Stoffer, Talia Dunyak, CRH, and Nancy K. Clark. And yeah, by the age of three, most tiny people have all 20 of their baby teeth with 32 hanging out in a jaw condominium upstairs. If you've ever seen x-rays of baby heads or medical specimens, rest in peace, it looks like a lotus pod. And if you don't have natal osteophobia, 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 macha 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 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. And it's like, it's called precise occlusion. It's 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. 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 and then have that grow. And that's now in progress. People are doing 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. 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 their implants, etc. So, yeah, it's just not, it's never as good as your original organ, right? Yeah. You mentioned salamanders. Hate me. Salamators have teeth. Salamanders have teeth. Are they little nubbins? Tiny, tiny, tiny little things. Eating bugs, eating bugs, eating ants, mostly worms. They're kind of like just Velker 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, not back up. Right. Yeah. What about snails have those like raspers, what are they called? Radulas. Yeah. Thank you.

Are those teeth? They are not teeth. Okay. We found the boundary. And how do we know they're not teeth? teeth. They're not made of the same stuff. They're actually keratin. It's like a little pad of Velcro kind of thing, little hooks that's keratinized. Yeah. Not odontodes. Not odontodes, which are a vertebrate only thing. Yeah. So true teeth and odontodes in large start at vertebrates. No invertebrates have

them. They have similar things. I mean, things have got to eat, but not true teeth. But just not an actual odontode. Going back to replacing teeth, like sharks are placing 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? Because 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. Or the reverse is true. Because they have that enamel, then they need higher replacement. Do crocodiles and alligators lose their teeth? Oh, yeah. They do?

Oh, yeah. They constantly replace their teeth, constantly. Do you find them fossilized? Oh, yeah. Oh, yeah. They make up, like, chunks of the freshwater fossil record. What about dinosaurs? Replace their teeth constantly.

Shut up. Really? Because mammals hang on to them. Mm-hmm. Do you find a lot of dinosaur teeth fossilized? Oh, yeah. Oh, yeah, tons. Yeah, yeah, yeah.

Do people ever just come across them? 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, etc.

Not all teeth are super valuable to science. So like a lot of shark teeth, we have just tons. Some dinosaur teeth. So like I was working, I was in Alberta for a bit, and we found a whole hadrosaur dental battery. And hadosaurs 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's dead because they were held together with ligaments. What about deer teeth and herbivore teeth? So herbivore teeth are really weird, particularly deer and, what is it, horses, and camel, anything that eats a lot of abrasive material. 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 tissues. And so that way you're like basically making a greater for the plant matter. Do they replace those teeth or no? Same as us. They're mammals. But rats and other lagomorphs.

Do 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. It's horrible. I know, right? But that's because they're ever growing. And they'll actually like curl and like grow into their own palettes 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 adult teeth. That's it. I wonder if they ever swallow them when they fall out. Oh, sure. 100%.

Yeah, yeah. Dogs and cats do too. Yeah. Yeah. Come up. Comes right there. God. And if you want to hear, fun fact.

Yeah. Rodent teeth, lag morph teeth. Why are the yellow? Different material? More denting? Iron and their enamel. So much stronger. So much stronger.

I love that they're not just dirty. You know? I'm so happy they're taking care of their dental hygiene. Yeah. 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 so it's just like, it keeps that really sharp edge. Ah, just a bevel. 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 servidology 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, 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? Absolutely champ. Painful. I'm not going to 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 pouched lion, thylacolio, having weirdo, beautiful, rodent-like front fangs. Okay, Sean asked, why are marsupial teeth so much different for most creatures we know? do you find a lot of different teeth in areas like Australia that's just its own continent? Can the be asked, it seems that a common problem with human teeth is overcrowding. Is this specific to humans or is there evidence of this and 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. 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 got to eat well. That selection pressure is probably lifted for us. One, because we're social animals. We feed each other, you know, we make mushy food for, like, 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 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 it on the fossil record too. That's how we know if something's been buried right away or 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. Oh, 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 dino.

Well, last Patreon question. What unexpected information can we gain from fossilized teeth beyond diet? But I want to 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 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 paleo-detective work. But basically they can find isotopes that link to diet. So now we know that some dinosaurs were eating like C4 plants or like this type of plant. Or we know 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,

continuous chemical history. Well, you are what you eat. Um, okay, the most annoying thing about your job. I'm getting, 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 most recent paper did get covered in a creationist article. What did they say? Well, they said that I needed Jesus. They said that, 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 gone for the paper so far. But yeah. It's a pretty new paper. But it was hilarious. It was pretty good. I can send it to you. It's hilarious.

Oh dear. So bizarre. Okay, let's dive into her 2025 nature paper once again titled the origin of vertebrate teeth and evolution of sensory exoskeletons in which lead author, Dr. Yara Haridi establishes, quote, here to resolve controversy and understand the origin of dental tissues, we synchrotron scanned diverse, extinct and extant vertebrate and invertebrate. exoskeletons, we find that the tubules of anadalepsis have been misidentified as dentine tubules and instead represent a glaspididid 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 thing. And so people found it and thought that this was the earliest vertebrate. And I was like, great. We're going to image this thing with all this new methods that we have. So I now use a particle accelerator to image fossils. No. I've heard about this. No. Okay. So synchotrons are these rings that you accelerate an electron in and then you basically shoot x-rays from the bending of those to 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 order division 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 you Chicago. And I was like, this is really what I want to do. The fossils exist somewhere. Let's go find them. And so they've been published on before in the 90s, and then again in the 90s, and they were like a big splash every time because it's a brand new early vertebrate. 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 vertebrates. But maybe these are arthritis. 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 them? And everyone who said it was our 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 odontode.

and they saw these tubules inside the adontode. And so they were like, this is dentine. And dentine is only found in vertebrates. And therefore, it has to be a vertebrate. Slam dunk, big deal. Mm-hmm. Came out. And everyone was like, okay, great.

We now know this late Cambrian fish thing, fragment thing, is a vertebrate. 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. Mm-hmm. 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 to. 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 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 fish. 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. But even at that moment, I was like, why does it still look like a tooth? 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 a dontodes on an arthropod versus a vertebrate? Yeah. So I did some deep digging, read way too much about arthropods. And found out that there are these things called syncytes. Sensile are sensory structures that are super diverse. So 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. Are those steady? Yeah. Exactly. So that's a type of sensile. That's a mechanosensor one. So it can sense the deflection as they move. 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 cambrae. It was sensory organs all over their bodies. 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. And that makes sense that they look like odontodes. I'm like, why does it make sense?

And he's like, well, because teeth are sensory. Adonotodes are probably. sensory too. And I was like, how do we prove this? How do we actually test if odontodes, which are outside the mouth, are sensory, the same way teeth inside the mouth are. Yeah. So, you know, your teeth are sensitive, right? Of course. You're having some issues with that 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 has sensory organs. Elephants touching the ground, narwhals with their giant, like, horn, it's not a horn, it's actually a giant tooth. Bunkers. Bunkers. And they sense all kinds of

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. Because when your dentine is exposed, it's the sensitive tissue. Oh, no. Okay. So now we know adontodes have dentine, and we know that teeth have dentine. But we don't know. if adon toads outside the mouth are sensitive. And so this is where I took a really weird tangent that I want to tell you about. So remember when I told you that sharks have adontoads? They're covered in these little bits.

The other ones that have adontoes 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 odontodes too. They're covered in little teeth. What? Bizar. And they are super easy to keep and super common.

So I went to a pet store and I got a bunch of them. Oh, my God. And I started breeding them in the lab to get their little embryos. So we could actually test if their adon toads are innervated because that would be the first step for them to be actually sensory. If the adon toad has nerves going to it, then at least that's step one of it being innervated. And these adon toads in our early fish from the middle order division have pulp cavities. And pulp cavities are where the next. nerve goes. And we were able to trace it all the way down to know that, like, there had to have

been a nerve there. 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 method called clarity, where you make the little embryo super clear. You basically remove all the fats and lots up with 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. 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 adontode. All their adonotes 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 chican tones that are on this like, catfish are really weird, guys. I'm just going to side note everybody. I think what is it? One in five vertebrates is a catfish? No. Please check me on that. Year later told me that she meant one in 20 or five percent of all vertebrates are catfish.

One in 20 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 5% of vertebrates on dating apps are bots. Who knows? Anyway, actual real, slimy, perfect, whiskery catfish. Their diversity is wild.

Yeah. No. They did really well for themselves. Not all of them have adon toads, 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. They also sense their environment all the time because they're bottom dwellers, right? They're always feeling the bottom and they're tasting with taste buds in between their addontos.

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. Yeah. Why don't sci-fi movies just do a better job? Just do a biology.

Yeah, just do myology. 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 made an arthropod library where we did comparative stuff. We found out that they were some silly.

Then we did a bunch of stuff on sharks and catfish to find out the adontodes were innervated and then tied it all back to the Ordovician vertebrates. So this paper, we basically said the late Cambrianianianian. supposed vertebrate is not a vertebrate. So we kicked that out, which meant that now our true earliest mineralizing vertebrates are middle-orderivision for 150 or so million years ago. And we finally have a little bit of proof that the external odontodes were not only for 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 function.

I tell my dentist about this. Do you dentists know this? I tried. I just had a tooth cleaning actually last week and I'm like, hey, I was so happy because I'm proud of my paper and I'm like, you want to know something? And they're like, please open your mouth. No. I'm like, please, 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, we were talking. Okay. What were we talking about? But no, I would say the hardest part, that was the question, right? Hardest part about my job is that I have to keep thinking about ancient fish while the world is doing what the world is doing. Yeah. I think that would be the hardest part. Funding has obviously become a problem. recently for a lot of scientists, particularly natural history, particularly life science, 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 in general, because we need to

preserve these things. New discoveries are how we get out of economic downfalls, et cetera, So that's always said. But I think the hardest, hardest part is just, I guess I think about old bones today, even though, you know, bombings are happening or economic crashes are happening. 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 it'll be the hardest part. Just you're like, head down, don't mind the wars, the genocides, the climate change. Yeah.

And that's tough. Yeah. 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. 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 with science. 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 you can. 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 I mean, 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, odontode goosebumps? Ooh, don'toed goosebumps.

That's disturbing but accurate. 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 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. Oh my God. That's such a bizarre feeling. And if you literally sit with it and you let it like permeate your being,

you realize how special that is and how small we are. And kind of making ourselves small, I think in many ways, like I don't know, it makes you feel like you're part of a big system and time and the earth. and all of that comes together to make this particular moment where you're seeing this fish.

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 ADHD's like dream, which is why there's so many of us in academia. Yeah. Right? Yeah. So, I mean, I love my job.

When you think about things in the long term, exasentially, not to doom and gloom it, but if you could fossilize yourself after death, would you, like, do you want to 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, I kind of want my skull to be around afterward. You can donate to science. And then, you know, you'll probably end up like a cadaver in anatomy lab.

And that's always really, really helpful. 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 don't find it like obviously I mean I work with bones all the time I don't find it 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 let let the octopus aliens find me yeah I'm with you just a little peace sign in a mud flat perfectly flattened yeah Slop me over. Yeah. No coffin, please. Just wet, wet mud.

This is a joy. And I'm so glad this has been six years in the making. At least. At least. At least. Now you're doctor. Thank you for having me at this beautiful, terrifyingly dark maze of cabinets known as the collections of the Field Museum. They're so long.

Oh, my God. What an icon. So ask informed people unabashed questions because. their skulls are full of good stuff. Thank you so much paleo-histologist, 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. Herrii, her website is yaraheriti.com. Her Instagram is Yara underscore herridi, and we'll have more links to the studies and the Samirot Project at alleyward.com slash ologies slash paleo histology. And remember we also have kids-safe,

classroom-appropriate cuts of Ologies classics. They're out every week. Just search Smollogis, S-M-O-O-G-I-E-S, and subscribe wherever you get your podcasts. We are at Ologies on Blue Sky and Instagram. I'm at Allie Ward on both. Ologies merch is available at Ologiesmerch.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, Avaline Malik, makes our professional transcripts. Calliard Dwyer does the website. The Smiley Noel Dilworth is our scheduling producer. The web holding us together as managing director, Susan Hale.

And working as a set to chew through the edits are Jake Chafee 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 going to 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. It's a very fun, low-key way to just make something no stakes 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-U-R-L hat, I think, and my profile picture is a bat face. Again, not getting paid. Doodle. Just love it. Second Secret, which is a bit more vulnerable. I feel like I'm going to 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 was like a panty hose big girdle and it was filled with like 10 pounds of bird seed and it was fun to squish it with my finger also I had baby bangs and blue black hair so enjoy that okay so floss those modern teeth they evolved so hard and they deserve it wear your mouth guards lock eyes bye bye Hacadermatology, momeology, cryptozoology, Lytology, nanotechnology, meteorology, I want to see them.