Paleohistology (WHY TEETH EXIST) with Yara Haridy

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.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Alie Ward?

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• 0:44Alie Ward?

  So if you're ready for thicker, fuller hair, start your free online visit today at forhers.com/ologies for personalized care. So that's F-O-R-H-E-R-S.com/ologies. Individual results may vary. Featured products include compounded drug products, which the FDA does not approve or verify for safety, effectiveness, or quality. Prescription required. Price varies based on product and subscription plan. See website for full details, restrictions, and important safety information. Ugh, trips are full of unexpected discoveries. Maybe you see a sea slug, or you find out that your friend still sleeps with a stuffed animal. But when it comes to your vacation rental, there should not be any surprises. When you book a Verbo vacation rental, if what you expect isn't what you get, Verbo Care has you covered. If something's broken or just not right,

• 1:29Alie Ward?

  Verbo will work to make it right. Plus, you get 24/7 live human support with every booking. Grab your stuffy, we're going on vacay. So book today on the Verbo app. If you know, you're Verbo. Terms apply. See verbo.com/trust for details.

• 1:44Alie Ward?

  Oh, hey, it's your neighbor's Wi-Fi network that shows up as New England clam router, Ally 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. 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 olde 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.

• 2:27Alie Ward?

  They were born in Morocco, they grew up in Egypt and moved to Canada as a pre-teen, then did undergrad in pre-med 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 Vertebrae 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.

• 3:12Alie Ward?

  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 ologiesmerch.com. As a reminder, also, we have shorter, kid-friendly episodes suitable for all ages and classroom safe, and those are called Smologies, 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 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.

• 3:53Alie Ward?

  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 mouths. 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,

• 4:36Alie Ward?

  what tools fossil pickers rely on, teeny tiny mysteries, busting age-old flimflam.

• 4:42Alie Ward?

  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, paleohistologist Dr. Yara Haridi.

• 5:14Alie Ward?

  First thing I'll have you do is if we could say your first and last name and the pronouns you use.

• 5:19Speaker 02

  So I'm Yara Haridi.

• 5:20Alie Ward?

  Dr. Haridi.

• 5:23Speaker 02

  Dr. Yara Haridi, she/her pronouns.

• 5:27Alie Ward?

  When did you defend your PhD?

• 5:28Speaker 02

  I was officially awarded to me in January 2022. Yeah.

• 5:34Alie Ward?

  I followed you on Twitter for years.

• 5:36Speaker 02

  Before.

• 5:37Alie Ward?

  I know.

• 5:37Speaker 02

  Yeah, in the before times.

• 5:39Alie Ward?

  In the before times, the raccoon was Twitter. When that's where all the scientists gathered.

• 5:43Speaker 02

  It was such a beautiful time.

• 5:44Alie Ward?

  It was a beautiful time.

• 5:45Speaker 02

  Yeah.

• 5:45Alie Ward?

  I got to know your work. And I always loved that whenever someone found a like a raccoon skull under a shed, they would tag you. You're like, what is this?

• 5:53Speaker 02

  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, 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.

• 6:20Alie Ward?

  Yeah.

• 6:20Speaker 02

  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.

• 6:28Alie Ward?

  Nothing but blue skies. So I am excited to catch up with you because I wanted to have you on for so long. Now, okay, theology itself.

• 6:39Alie Ward?

  I saw that you have a paper histological skeletonology. That a possibility. Paleodentology. What what are we thinking? What would you say yourology is?

• 6:49Speaker 02

  I mean, when people ask me like what my main method is, it's paleo histology. 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.

• 7:06Alie Ward?

  Old, old.

• 7:07Speaker 02

  Yeah, old, old.

• 7:08Alie Ward?

  We're talking tissues, but we're also talking teeth. Is a tooth a tissue?

• 7:12Speaker 02

  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.

• 7:22Alie Ward?

  Yeah.

• 7:22Speaker 02

  So those will be the tissues, but the structure as a whole is the tooth.

• 7:26Alie Ward?

  And take me back. When did you start getting interested in paleontology?

• 7:31Speaker 02

  Oh, girl. This is a 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.

• 8:17Speaker 02

  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.

• 8:36Speaker 02

  So when I decided to go into a science and try to at least go into being a doctor, so 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 turned left or a couple of left turns turned right. And I got into paleo. They offered me a masters and I continued from there.

• 9:03Alie Ward?

  What was it about it? Was it just the age, like the unfathomable age? Was it the structures?

• 9:09Speaker 02

  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?

• 9:35Alie Ward?

  Yeah.

• 9:36Speaker 02

  But then there was a PhD student in the lab at the time and he taught me this method called paleo histology 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? 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.

• 10:20Speaker 02

  All that was recorded in the fossils. And at that point I was like, oh, wait, this might be a real science.

• 10:25Alie Ward?

  This might be a real, actual thing.

• 10:28Speaker 02

  Well, before that, everyone was 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.

• 10:43Alie Ward?

  I feel like if you are 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.

• 11:04Speaker 02

  Yeah.

• 11:04Alie Ward?

  Or scales, something.

• 11:06Speaker 02

  Something still hard.

• 11:07Alie Ward?

  Something still hard, yeah, something with with a structure to it.

• 11:10Speaker 02

  And that's fair, because 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?

• 11:24Alie Ward?

  Yeah.

• 11:24Speaker 02

  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.

• 11:50Alie Ward?

  And it is rock, but it takes the impression of all those tissues?

• 11:54Speaker 02

  Not always.

• 11:55Alie Ward?

  Oh, what? Okay.

• 11:56Speaker 02

  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 disappeared. Sometimes the tissue itself gets mineralized. So for example, let's think of your skin.

• 12:16Alie Ward?

  Mm hmm.

• 12:16Speaker 02

  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.

• 12:35Alie Ward?

  I didn't realize that soft tissues were even something that you could look at. Now, between the soft tissues and the teeth.

• 12:42Speaker 02

  Mm hmm.

• 12:43Alie Ward?

  Teeth obviously evolved over time. When did things start getting teeth?

• 12:49Speaker 02

  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 tissues?

• 12:59Alie Ward?

  Okay.

• 13:00Speaker 02

  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 fossilized 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?

• 13:39Alie Ward?

  Mm hmm.

• 13:40Speaker 02

  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 or division. So about four hundred and fifty five million years ago.

• 13:53Alie Ward?

  Oof.

• 13:53Speaker 02

  Yeah, hard, hard to

• 13:55Alie Ward?

  Can't fathom.

• 13:56Speaker 02

  conceptualize, right?

• 13:57Alie Ward?

  Can't even fathom.

• 13:57Speaker 02

  So dinosaurs went extinct when?

• 13:59Alie Ward?

  Sixty five, yeah.

• 14:00Speaker 02

  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.

• 14:14Alie Ward?

  Were they ever made of cartilage and get harder? Or they were always mineralized? Did a- animals ever have like kind of gummy like blablablablabla like kind of like teeth?

• 14:24Speaker 02

  I love, did they just gum things to death in the ocean?

• 14:27Alie Ward?

  Yeah.

• 14:27Speaker 02

  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 of fish.

• 14:45Alie Ward?

  Woo.

• 14:45Speaker 02

  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 gonna like clean your car with.

• 15:01Alie Ward?

  Yeah.

• 15:01Speaker 02

  They look like that, but stick googly eyes on the end.

• 15:03Alie Ward?

  Oh, no.

• 15:04Speaker 02

  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 adontodes. So that's a word I'm gonna be using often. So adontodes 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 the inside of the mouth.

• 15:29Alie Ward?

  It sounds like a teratoma. You know?

• 15:32Speaker 02

  Yeah, totally.

• 15:34Alie Ward?

  A blob item with teeth sticking out everywhere. But what did they use them for on the outside?

• 15:42Speaker 02

  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.

• 16:08Alie Ward?

  Yeah.

• 16:08Speaker 02

  Makes it harder for parasites to get attached, et cetera, et cetera.

• 16:11Alie Ward?

  Please, please see our gorology episode about long, cute, ancient, patient, poopable nightmare fish with the iconic biologist and punster, Dr. Solomon David, as well as our teratology episode about the history and culture of monsters in 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.

• 16:40Speaker 02

  And of course, the image of like teeth outside the mouth is so grotesque.

• 16:44Alie Ward?

  Yeah.

• 16:44Speaker 02

  But if you think about like modern sharks, modern sharks have teeth outside the mouth or they have these odontodes, they're covered in them. So if you put sharks one way, it's smooth. But if you put 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.

• 16:59Alie Ward?

  Those are odontodes?

• 17:00Speaker 02

  Yeah.

• 17:00Alie Ward?

  Oh.

• 17:01Speaker 02

  Exactly.

• 17:02Alie Ward?

  Covered in tiny teeth?

• 17:04Speaker 02

  Mm hmm. Yeah.

• 17:05Alie Ward?

  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.

• 17:15Speaker 02

  Yep.

• 17:15Alie Ward?

  So the first ones, though, were outside the body. When did they start merging into the hole?

• 17:23Speaker 02

  Uh, merging into the whole. Um, should we go back to the, what are they for on the outside?

• 17:29Alie Ward?

  Yeah, right, right.

• 17:30Speaker 02

  So there's a couple of floating hypotheses. There's one that's like, okay, they're for protection because they're hard and they're on the outside. And at that time period, middle order of vision, there's like big scary things in the ocean, big cephalopods, so big squid nautilus 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, 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.

• 18:13Speaker 02

  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 don't toads 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 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 are as well.

• 18:45Alie Ward?

  How big were these outside ones? Were they teeny or were they like?

• 18:48Speaker 02

  I should just show you. They're in the cabinets behind us.

• 18:51Alie Ward?

  Yeah, grab one.

• 18:52Speaker 02

  Yeah, give me one second.

• 18:53Alie Ward?

  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 odontoid also, which is exciting. I didn't know that there was even a generalized name for them. This hall of cabinets is so bonkers.

• 19:15Speaker 02

  So I have a part of a head shield from a giant fish. And what you can see here. All these little bumps?

• 19:24Alie Ward?

  Mm hmm.

• 19:24Speaker 02

  Each one of them is a little tooth.

• 19:26Alie Ward?

  No. It looks

• 19:28Speaker 02

  Or a dant.

• 19:29Alie Ward?

  A dantode. It looks kind of like a tiny cottage cheese ceiling, you know?

• 19:34Speaker 02

  Yeah, yeah, the popcorniness of it.

• 19:36Alie Ward?

  Mm hmm.

• 19:37Speaker 02

  The texture is very intense.

• 19:38Alie Ward?

  They're like little tiny beads, almost. And now you clarified that you have gotten flak here and there for calling it a tooth because a tooth is in a jaw.

• 19:51Speaker 02

  Yeah.

• 19:52Alie Ward?

  But we're talking broadly to communicate.

• 19:54Speaker 02

  Right.

• 19:54Alie Ward?

  What it's an analogous structure.

• 19:56Speaker 02

  Right, or homologous, right?

• 19:58Alie Ward?

  Homologous, okay.

• 19:59Speaker 02

  Because they have the same origin. So the reason that we know that these dantodes on the outside of the mouth are even related to teeth is because they're made of the same thing.

• 20:08Alie Ward?

  Mm hmm.

• 20:08Speaker 02

  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.

• 20:15Alie Ward?

  Mm hmm.

• 20:16Speaker 02

  Except that they don't replace the same way and they don't have a job in that they don't chew.

• 20:21Alie Ward?

  And then they started coming, merging, they started saying, let's get in the hole.

• 20:27Speaker 02

  So how did we get teeth in the mouth? Or how did you, how did you go from dantodes, things that are bumpy outside the head, to things that I can bite other fish with? So that happened a long, we assumed some time in probably the Devonian.

• 20:42Alie Ward?

  So the Devonian was a cute little sixty million year era from about four hundred and twenty million years ago to three hundred and sixty 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.

• 21:12Alie Ward?

  Meaning flat plate fish that looked like they were wearing bulletproof vests and helmets. Four hundred 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 seventy-one people in the US in twenty twenty-three, but unprovoked sharks killed ten globally. Only two of those were in the US. Sharks are the eldest daughter of our planet.

• 21:40Speaker 02

  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 sharper and pointier odontodes, and they kind of grade into the mouth. And then you have actual pointy things in the mouth, ostensibly teeth.

• 22:01Speaker 03

  Can we see those pearly whites, eh?

• 22:02Speaker 02

  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 odontodes, they got re-expressed inside the mouth.

• 22:13Alie Ward?

  Oh, okay.

• 22:15Speaker 02

  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 gonna express it in the mouth instead.

• 22:28Alie Ward?

  Kind of like when you get a weird hair that pops up somewhere else. You go, what are you doing here?

• 22:32Speaker 02

  Yeah, except I don't recommend tweezing out your tooth.

• 22:34Alie Ward?

  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?

• 22:42Speaker 02

  Ivory is just dentine.

• 22:43Alie Ward?

  Ivory is just dentine. Does that mean there's no enamel or pulp?

• 22:46Speaker 02

  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.

• 23:12Alie Ward?

  Got it. Okay. I wonder why they don't keep the enamel since the enamel is so hard?

• 23:18Speaker 02

  Well, I think it's just it gets 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 they're not just like whacking around big sticks. Like there is some feedback. It's a living tissue, right?

• 23:40Alie Ward?

  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 of 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.

• 24:22Alie Ward?

  Our pachydermatologist 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.

• 24:30Alie Ward?

  And this is one thing in a recent paper of yours about sensitive teeth, like blame your fish ancestors.

• 24:36Speaker 02

  Yep.

• 24:38Alie Ward?

  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

• 24:45Speaker 02

  Oh, no.

• 24:46Alie Ward?

  It's just, I guess, a time mention, but I do blame my fish ancestors. I'm pissed with them.

• 24:50Speaker 02

  It's a good start.

• 24:50Alie Ward?

  So a sensory organ on the outside also helps them figure out like, oh, how cold the water is? What?

• 24:59Speaker 02

  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 some sensitivity from it. I mean, you know, you felt like if you press really hard on your teeth, you can feel them.

• 25:18Alie Ward?

  I know you just pressed on your teeth. I know it. Yeah.

• 25:21Speaker 02

  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 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 changed or any of that. We don't know exactly what they're sensing, but we know that some kind of signal was getting passed.

• 25:58Alie Ward?

  And then tell me a little bit about this paper.

• 26:01Speaker 02

  This paper has been the nightmare of the past three years.

• 26:04Alie Ward?

  Okay.

• 26:06Alie Ward?

  Checks out.

• 26:07Speaker 02

  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, uh, 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 adonotes, 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.

• 26:48Speaker 02

  And the fossil I was really interested in was this animal from the latest Cambrian.

• 26:53Alie Ward?

  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..."

• 27:30Alie Ward?

  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.

• 27:53Speaker 02

  Now, if you remember earlier, I said the best things that we know, the earliest vertebrates are from the middle Ordovician, the E. 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.

• 28:11Alie Ward?

  Oh dear.

• 28:11Speaker 02

  Um, 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.

• 28:22Alie Ward?

  And fragmentary, that's the whole tooth? Or that is just it burst into shards?

• 28:28Speaker 02

  I should show you.

• 28:30Alie Ward?

  Is it teeny? Yeah.

• 28:31Speaker 02

  What do you got?

• 28:33Alie Ward?

  These are the, oh, teeny, teeny.

• 28:35Speaker 02

  And I got how they're actually done in the rock.

• 28:37Alie Ward?

  You know what they look like? They look like nerds. Like the smallest nerds. And they're in a vial, you're pouring them out. Those are teeth? Those look like gravel.

• 28:47Speaker 02

  I know, right?

• 28:48Alie Ward?

  Those look like decomposed granite in a fancy garden.

• 28:51Speaker 02

  Do you see the little white bumps?

• 28:53Alie Ward?

  Yes.

• 28:53Speaker 02

  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.

• 29:03Alie Ward?

  They are like Grape-Nuts.

• 29:04Speaker 02

  Yeah.

• 29:04Alie Ward?

  The size of Grape-Nuts.

• 29:05Speaker 02

  Tiny. Um, and we got 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 odontode.

• 29:17Alie Ward?

  No.

• 29:18Speaker 02

  Every single one. So the odontodes 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.

• 29:39Alie Ward?

  They're teeny, tiny.

• 29:41Speaker 02

  So when someone tells you the fossil record is a problem, this is it.

• 29:45Alie Ward?

  I mean, you could overlook that so easily. And here you have a rock.

• 29:49Alie Ward?

  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?

• 30:02Speaker 02

  Yes.

• 30:03Alie Ward?

  Do you really?

• 30:03Speaker 02

  Yeah, we use dental tools all the time and dental putty to like make molds and stuff. Oh yeah, I'm friends with a lot of dentists.

• 30:10Alie Ward?

  I hope you have a good dentist. I can't believe how teeny it is.

• 30:14Speaker 02

  So I just opened another vial and poured in another bunch of scrap. But this one's supposedly from a different species. And so you can kind of tell because the shape of the odontodes is different. They're more elongate. They kind of look like little rice grains, except smaller than rice grains.

• 30:30Alie Ward?

  Yeah, they're like wavy almost.

• 30:32Speaker 02

  Yeah.

• 30:33Alie Ward?

  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 the ones we're looking at, the vial of wavy rice grains that Dr. Horeidi painstakingly picked out of a rock. So we sat down at the table with this array of ancient specimens around us like tapas.

• 30:56Speaker 02

  They're all over North America.

• 30:58Alie Ward?

  And how big was this animal?

• 31:00Speaker 02

  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 like 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.

• 31:24Alie Ward?

  How many people in the world do this?

• 31:26Speaker 02

  Paleohistology as a whole or?

• 31:28Alie Ward?

  Looking for tiny teeth like this?

• 31:30Speaker 02

  Um, probably a handful, probably less than 10 of us. Yeah.

• 31:34Alie Ward?

  Are you guys on a WhatsApp thread?

• 31:36Speaker 02

  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 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 vertebrate ancestors, cordates, et cetera, to the jump.

• 32:18Speaker 02

  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.

• 32:33Alie Ward?

  Is it unnerving to know that that missing link is somewhere in a rock? That y'all haven't found yet?

• 32:44Speaker 02

  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.

• 33:12Alie Ward?

  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?

• 33:20Speaker 02

  So I was just out in Colorado. We were looking at this one road cut. So there's this one area there 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 Order 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.

• 33:45Speaker 02

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

• 34:06Alie Ward?

  I remember talking to Michael Habib and asking about how much it costs for a dino dig.

• 34:14Alie Ward?

  And he's like, yes. And I was like, two million, three million? He was like, $10,000.

• 34:20Speaker 02

  Yeah.

• 34:21Alie Ward?

  And I was like, less than a Camry. Less than a used Camry to dig up dinosaurs. Like, is it tough to get an in when you know they're going to dynamite something? And you're like, oh, there's so much good 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?

• 34:39Speaker 02

  Totally, totally. I mean, but 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 wanted to check it out, moved 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 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 science. But it's just hard. It's sometimes hard to scrap that together. Yeah.

• 35:12Alie Ward?

  Bonkers to me, considering that that's like one dinner. That's like one dinner in Washington. It's just some hobnobbing over champagne somewhere with a lobbyist. I don't know.

• 35:23Speaker 02

  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. 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.

• 36:02Alie Ward?

  Your gummy boys and your floopy.

• 36:05Speaker 02

  Yeah, yeah, finless things. Yeah.

• 36:07Alie Ward?

  Um, can I, I know we have so much more to cover, but can I cover it with Patreon questions?

• 36:12Speaker 02

  Absolutely.

• 36:12Alie Ward?

  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 Warm to Gaza.

• 36:38Alie Ward?

  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 deaths from offenses from Israel, you can see our Genocideology 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 ologists' hearts each week.

• 37:12Alie Ward?

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• 37:55Alie Ward?

  a scientist that needs to put their work up, or someone who's just starting a business, I'm like, dude, Squarespace. So head to Squarespace.com/ologies for a free trial. And when you're ready to launch, use offer code OLOGIES to save 10% off your first purchase of a website or domain. You can do it. Peppa Pig is your preschooler's best friend. Give the gift of bike riding confidence this year and help Peppa learn to ride her bike. Kids can imagine learning to ride a bike with the Ready Pedal Go Peppa Bicycle Playset. Put Peppa's helmet on, attach the push stick to her bike, and push to make her pedal. Ready Pedal Go Peppa and more from Peppa Pig are now available at all major retailers this holiday season.

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• 39:38Speaker 06

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• 40:09Alie Ward?

  OK, thanks also to patrons of the show who submit questions before we record via patreon.com/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.

• 40:25Alie Ward?

  Mouse Paxton, Spicy Native, both wanted to know, in Spicy Native's words, "Baleen, when did it evolve? Is whale baleen, Mouse asks, considered teeth?" Ooh, that's a very good question. What is it? I thought it was keratinized, right? You're right. OK. Yeah. So not a teeth, not an odon.

• 40:46Speaker 02

  You got it?

• 40:47Alie Ward?

  Odontoin, odonto-

• 40:49Speaker 02

  You got this.

• 40:50Alie Ward?

  Why can't I do it?

• 40:51Speaker 02

  Because you're not believing in yourself.

• 40:53Alie Ward?

  No.

• 40:54Speaker 02

  Odontodes.

• 40:55Alie Ward?

  Odentodes.

• 40:56Speaker 02

  Odontodes, yeah, yeah, yeah. It's fine.

• 40:58Alie Ward?

  I'm new at this word.

• 41:00Speaker 02

  We'll get it. We'll get it, guys. Um, no, you're absolutely right. 10 points for Ally.

• 41:05Alie Ward?

  Okay.

• 41:05Speaker 02

  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.

• 41:11Alie Ward?

  Uh, odontodes. I did it. I did it.

• 41:16Speaker 02

  God, I'm so proud of you.

• 41:18Alie Ward?

  Thank you.

• 41:18Speaker 02

  Um, yeah, okay, so great question from your listeners. Baleen is not teeth.

• 41:24Alie Ward?

  Mm-hmm.

• 41:25Speaker 02

  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 both.

• 41:37Alie Ward?

  Oh.

• 41:38Speaker 02

  Maybe? Yeah, so, so baleen whales came from toothy ancestors. They came from whales that have teeth.

• 41:46Alie Ward?

  Mm-hmm.

• 41:46Speaker 02

  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 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. Or 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?

• 42:14Alie Ward?

  Mm-hmm.

• 42:14Speaker 02

  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.

• 42:24Alie Ward?

  Could baleen, because it's keratinized, be sort of like hair that's like just hanging out in the mouth?

• 42:30Speaker 02

  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. I'm not a whaleologist.

• 42:41Alie Ward?

  Mm-hmm.

• 42:41Speaker 02

  But, um, I think they probably just re-express that there. I don't know what an intermediate would look like. Maybe it had like weird mustaches. I don't know.

• 42:48Alie Ward?

  No, like a little walrus.

• 42:52Speaker 02

  That's a really good question.

• 42:53Alie Ward?

  We still haven't done a cytology 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. Mayan Marlo, Planet Si Lorraine, Empress of Smallwood, T-NOS, wanna know, Ryan asked, are bird beaks teeth?

• 43:17Speaker 02

  Ooh, bird beaks are not teeth. That's another keratin structure.

• 43:21Alie Ward?

  Mm-hmm.

• 43:22Speaker 02

  But birds did have teeth at some point.

• 43:24Alie Ward?

  Do they not have teeth now?

• 43:26Speaker 02

  No, birds have teeth now.

• 43:27Alie Ward?

  Oh, okay. What happened to them?

• 43:29Speaker 02

  Very good question. Don't know.

• 43:30Alie Ward?

  Okay. How are they chewing stuff?

• 43:35Speaker 02

  They don't chew. Birds don't chew.

• 43:37Alie Ward?

  At all?

• 43:37Speaker 02

  Uh-uh, no, no. Birds kind of like do a grab and swallow.

• 43:42Alie Ward?

  Because they got the crop.

• 43:43Speaker 02

  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?

• 44:19Alie Ward?

  Oh.

• 44:19Speaker 02

  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, 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 ramphothica, which is the fancy word for beak.

• 44:41Alie Ward?

  So, when you get attacked by a goose...

• 44:43Alie Ward?

  Or killed by like a cassowary, cassowary.

• 44:47Speaker 02

  Cassowary, yeah.

• 44:49Alie Ward?

  They're gumming you with keratin, sort of?

• 44:51Speaker 02

  So, I mean, a goose is gonna like, 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. They're not true teeth. And a cassowary is not gonna kill you with its beak, it's gonna kill you with its foot. Again, another keratin structure, don't mess with cassowaries. You can take a goose, but you can't take a cassowary.

• 45:13Alie Ward?

  No.

• 45:14Speaker 02

  Don't do it.

• 45:14Alie Ward?

  No, don't do it.

• 45:15Speaker 02

  Don't do it.

• 45:16Alie Ward?

  That's one of my biggest fears.

• 45:18Speaker 02

  Cassowary?

• 45:18Alie Ward?

  Yeah, just getting in a, 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'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.

• 45:33Speaker 02

  You're nuts.

• 45:34Alie Ward?

  I don't know.

• 45:35Speaker 02

  I would take a cassowary over a grizzly.

• 45:37Alie Ward?

  This is a good question.

• 45:38Speaker 02

  It's a great question.

• 45:39Alie Ward?

  I'm gonna, I'm gonna take a poll.

• 45:40Speaker 02

  Would you guys take a cassowary or would you take a grizzly? I don't know, it's a great question.

• 45:46Alie Ward?

  I gotta figure out too if cassowaries can fly. I don't think they can at all. Yeah, okay, not even up a tree? Okay. A grizzly can't go up a tree. Still, okay.

• 45:54Speaker 02

  Also cassowaries are such good dads. The dads do most of the caretaking, they're so sweet.

• 45:58Alie Ward?

  Okay.

• 45:58Speaker 02

  Cuties. Hang out with the cassowaries. Yeah, yeah, yeah, no, not the grizzlies.

• 46:02Alie Ward?

  I went down a D tour looking for a cassowary expert because according to my friend, Wikipedia, cassowaries 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 YYZ, wanna know about bone density?

• 46:44Alie Ward?

  Do you think from a histological perspective, do you think that hormones were affecting these structures? Like these, um, odontodes?

• 46:55Alie Ward?

  I said it.

• 46:55Speaker 02

  Louder.

• 46:56Alie Ward?

  Odontotes.

• 46:57Speaker 02

  You killed it.

• 46:57Alie Ward?

  I had no caffeine today.

• 47:00Speaker 02

  Oh.

• 47:00Alie Ward?

  And I also.

• 47:01Speaker 02

  Why don't we do coffee first?

• 47:02Alie Ward?

  I don't know.

• 47:03Speaker 02

  There's a kind of fade out.

• 47:04Alie Ward?

  I don't know.

• 47:05Speaker 02

  I commend you.

• 47:06Alie Ward?

  I'll plead also that I'm on Pacific time. But hormones affecting bone density, tooth density?

• 47:12Speaker 02

  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 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.

• 47:54Alie Ward?

  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.

• 48:04Speaker 02

  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? We get osteoporosis.

• 48:20Alie Ward?

  Yeah.

• 48:21Speaker 02

  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.

• 48:39Alie Ward?

  Mm hmm.

• 48:39Speaker 02

  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.

• 48:49Alie Ward?

  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 spaceflight. 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 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, Scott and Mark Kelly, both astronauts.

• 49:33Alie Ward?

  Mark Kelly, yes, an astronaut and an Arizona State Senator, husband to Gabby Giffords. It involved physiological, telemetric, transcriptomic, epigenetic, proteomic, 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, 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?

• 50:18Alie Ward?

  Does enamel wear down? Or do your teeth say, "Hey, we've got a lot of pressure, I better build this up"?

• 50:24Speaker 02

  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 a slight remineralization of our enamel. So you know, if you have really weak enamel, there are ways to make it stronger. Florid 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.

• 51:07Alie Ward?

  Yeah.

• 51:07Speaker 02

  Yeah.

• 51:07Alie Ward?

  Oof. 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 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, Emma T., Rot Vice Waffle, Han the Bee, Kim Grineer, Era Victor, Empress of Smallwood, Maria Walzer, and Deli Dames. This was a good question. Also, everyone, you gotta brush your kitties and doggies teeth.

• 51:51Alie Ward?

  I, we love their disgusting devil breath, but you gotta 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 ad, a 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 asked, as well as Lori Fulford, Wynne Rebecca Smith, Megan Walker, Naomi Jane, Alyssa McElroy, Katze, Alexandra Rambo, Sheila Marita Honey Pie, Tom Boudry, Catherine

• 52:35Alie Ward?

  BH, first time question askers, Ariana Rose, Planet Si 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.

• 52:49Alie Ward?

  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 waist? Those are real?

• 53:17Speaker 02

  Yeah.

• 53:17Alie Ward?

  Oh, jeez.

• 53:18Speaker 02

  Oh, yeah.

• 53:19Alie Ward?

  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?

• 53:25Speaker 02

  So, great question. Tooth replacement or constant tooth replacement is the original state. Once tooth replacement evolved, almost everything kept replacing its teeth. So salamanders replaced their teeth, reptiles replaced 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?

• 54:04Alie Ward?

  Yeah, horrifying.

• 54:05Speaker 02

  Terrifying, but they're just like in wait, 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.

• 54:15Alie Ward?

  Many patrons had teeth on the brain, including mycologist Janet R., Dame Camacho, Emily Stauffer, Talia Dunya, 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, your, then your tryphophobia of holes will definitely kick in. Round nubbins. Housed in holes, as your internet father dad word, I do not recommend Googling baby skulls

• 54:58Alie Ward?

  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.

• 55:07Speaker 02

  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. So just fitting together really well. Really hard to do if you're constantly changing your teeth.

• 55:32Alie Ward?

  Oh, yeah.

• 55:33Speaker 02

  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.

• 55:58Alie Ward?

  Right.

• 55:59Speaker 02

  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.

• 56:10Alie Ward?

  They're like, it's a prototype. It's, I'll get it next time.

• 56:12Speaker 02

  It's fine.

• 56:13Alie Ward?

  I'll get it next time.

• 56:14Speaker 02

  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, et cetera. So, yeah, it's just not, it's never as good as your original organ, right?

• 56:34Alie Ward?

  Yeah. You mentioned salamanders.

• 56:37Speaker 02

  Hit me.

• 56:38Alie Ward?

  Salamanders have teeth?

• 56:38Speaker 02

  Salamanders have teeth.

• 56:39Alie Ward?

  Are they little nubbins?

• 56:40Speaker 02

  Tiny, tiny, tiny little things. Eating bugs, eating ants, mostly worms. They're kind of 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 of that is just in one area. So you really want your worm to go down.

• 57:00Alie Ward?

  Yes.

• 57:00Speaker 02

  Not back up.

• 57:01Alie Ward?

  Right.

• 57:01Speaker 02

  Yeah.

• 57:02Alie Ward?

  What about snails have those like raspers? What are they called?

• 57:05Speaker 02

  Uh, radulas. Yeah.

• 57:08Alie Ward?

  Are those teeth?

• 57:10Speaker 02

  They are not teeth.

• 57:11Alie Ward?

  Okay.

• 57:11Speaker 02

  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, little hooks that's keratinized. Yeah, yeah.

• 57:24Alie Ward?

  Not odontodes.

• 57:25Speaker 02

  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.

• 57:37Alie Ward?

  Right. But just not an actual odonto. 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?

• 57:53Speaker 02

  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 high replacement.

• 58:29Alie Ward?

  Do crocodiles and alligators lose their teeth?

• 58:31Speaker 02

  Oh, yeah.

• 58:31Alie Ward?

  They do?

• 58:33Speaker 02

  They constantly replace their teeth constantly.

• 58:35Alie Ward?

  Do you find them in fossilized?

• 58:37Speaker 02

  Oh, yeah. Oh, yeah. They make up like chunks of the freshwater fossil record.

• 58:42Alie Ward?

  What about dinosaurs?

• 58:43Speaker 02

  Replace their teeth constantly.

• 58:44Alie Ward?

  Shut up.

• 58:45Speaker 02

  Mm hmm.

• 58:45Alie Ward?

  Really? Because mammals hang on to them.

• 58:48Speaker 02

  Mm hmm.

• 58:48Alie Ward?

  Do, do you find a lot of dinosaur teeth fossilized?

• 58:51Speaker 02

  Oh, yeah. Oh, yeah, tons.

• 58:52Alie Ward?

  No.

• 58:53Speaker 02

  Yeah, yeah, yeah.

• 58:53Alie Ward?

  Ah, where, do people ever just come across them?

• 58:57Speaker 02

  Uh, if you're in the right place, yeah, absolutely. Yeah, yeah, yeah.

• 59:00Alie Ward?

  If you find a dinosaur tooth, you should call a paleontologist though, right?

• 59:04Speaker 02

  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. Cause 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.

• 59:23Alie Ward?

  Yeah.

• 59:23Speaker 02

  Um, some, some dinosaur teeth. So like I was, I was working, 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.

• 59:38Alie Ward?

  Ooh.

• 59:39Speaker 02

  Yeah, because they wanna like chew a lot of plant matter with multiple tissues at once. Right? So they use multiple teeth at once to kinda 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.

• 59:55Alie Ward?

  What about deer teeth and herbivore teeth?

• 59:58Speaker 02

  So herbivore teeth are really weird, particularly deer and what is it? Horses and camel, anything that eats a lot of abrasive material.

• 1:00:07Alie Ward?

  Mm hmm.

• 1:00:08Speaker 02

  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.

• 1:00:18Alie Ward?

  Mm hmm.

• 1:00:18Speaker 02

  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 it greater.

• 1:00:28Alie Ward?

  Mm hmm.

• 1:00:28Speaker 02

  For the plant matter. Yeah.

• 1:00:30Alie Ward?

  Do they replace those teeth or no?

• 1:00:32Speaker 02

  Same as us, they're mammals.

• 1:00:34Alie Ward?

  But rats and other lagomorphs, do there's, they keep growing to sharpen, right?

• 1:00:40Speaker 02

  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.

• 1:01:00Alie Ward?

  Ooh.

• 1:01:00Speaker 02

  I know, right?

• 1:01:01Alie Ward?

  No.

• 1:01:01Speaker 02

  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.

• 1:01:14Alie Ward?

  I wonder if they ever swallow them when they fall out.

• 1:01:17Speaker 02

  Oh, sure. Hundred percent. Yeah, yeah. Dogs and cats do too. Yeah.

• 1:01:19Alie Ward?

  They poop mouth?

• 1:01:20Speaker 02

  Yeah, yeah. Comes right through.

• 1:01:22Alie Ward?

  God.

• 1:01:22Speaker 02

  And if you wanna hear fun fact.

• 1:01:24Alie Ward?

  Yeah.

• 1:01:24Speaker 02

  Rodent teeth, lagomorph teeth, um, why are they yellow?

• 1:01:27Alie Ward?

  Different material, more denting?

• 1:01:30Speaker 02

  Iron, iron in their enamel.

• 1:01:32Alie Ward?

  So much stronger?

• 1:01:33Speaker 02

  So much stronger.

• 1:01:35Alie Ward?

  I love that they're not just dirty. You know?

• 1:01:40Speaker 02

  I'm so happy they're taking care of their dental hygiene. And it's just an adaptation.

• 1:01:45Alie Ward?

  It's not just turmeric, you know?

• 1:01:47Speaker 02

  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, it keeps that really sharp edge.

• 1:01:55Alie Ward?

  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 servitology 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, Alexandra 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.

• 1:02:37Speaker 02

  Can't believe you're doing this without caffeine. Absolute champ.

• 1:02:41Alie Ward?

  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 Thylacoleo having weirdo, beautiful rodent-like front fangs. 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? Can the bee ask, it seems that a common problem with human teeth is overcrowding. Is this specific to humans or is there evidence of this in other animals? Like, do they have any wonky occlusion, just like on accident?

• 1:03:25Speaker 02

  I mean, yeah, pathologies happen, usually if something happened in childhood or depending on how.

• 1:03:34Speaker 02

  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.

• 1:03:48Alie Ward?

  What am I supposed to do with these?

• 1:03:49Speaker 02

  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, 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.

• 1:04:33Speaker 02

  You know, people counter that with, but I don't want to give my baby like a whole bone to chew on, which is 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.

• 1:04:48Alie Ward?

  And with dogs, when you give them bones to chew, cooked no good because it's splinters, right? Are you cooking out these binding collagen fibers? Is that what's going on?

• 1:04:57Speaker 02

  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.

• 1:05:23Alie Ward?

  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.

• 1:05:33Speaker 02

  No, I mean, things die out there and then get flooded over or buried secondarily, yeah?

• 1:05:38Alie Ward?

  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?

• 1:05:55Speaker 02

  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?

• 1:06:16Alie Ward?

  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.

• 1:07:01Speaker 02

  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.

• 1:07:24Alie Ward?

  And this is in their tissues and not just like plaque around it?

• 1:07:28Speaker 02

  Correct. Yeah, it's the actual enamel that holds on to 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, a continuous chemical history.

• 1:07:47Alie Ward?

  Well, you want what you eat. Um, okay. The most annoying thing about your job. I'm getting, can I guess?

• 1:07:53Speaker 02

  Yeah, I'm so curious.

• 1:07:56Alie Ward?

  Funding? Funding or?

• 1:08:00Alie Ward?

  Do you get emails from people who tried to convince you that dinosaurs didn't exist?

• 1:08:05Speaker 02

  I don't, although my last, my most recent paper did get covered in a creationist article.

• 1:08:10Alie Ward?

  What did they say?

• 1:08:11Speaker 02

  Well, they said that I needed Jesus.

• 1:08:16Speaker 02

  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 gone for the paper so far, but yeah.

• 1:08:28Alie Ward?

  No.

• 1:08:29Speaker 02

  It's a pretty new paper, but it was hilarious. It was pretty good. I can send it to you. It's hilarious. It's so bizarre.

• 1:08:35Alie Ward?

  Okay, let's dive into her 2025 Nature paper, once again titled "The Origin of Vertebrate Teeth and Evolution of Sensory Exoskeletons",

• 1:08:45Alie Ward?

  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 anatolysis have been misidentified as dentine tubules and instead represent aglaspedid arthropod sensory sensilla structures. What does all that mean? Let's gossip about it."

• 1:09:17Speaker 02

  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 gonna image this thing with this, all this new methods that we have. So I now use a particle accelerator to image fossils.

• 1:09:36Alie Ward?

  No.

• 1:09:36Speaker 02

  I've not heard about this.

• 1:09:37Alie Ward?

  No.

• 1:09:37Speaker 02

  Okay. So synchrotrons 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, which is the point. 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 ordination all the way back to the late Cambrian. And it would be my transitional fossil that I was looking for.

• 1:10:17Alie Ward?

  Oh, my god.

• 1:10:17Speaker 02

  This is what I pitched to come to UChicago 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, 70s, and then again in the 90s. And they were like a big splash every time because it's brand new, early vertebrate.

• 1:10:32Alie Ward?

  Mm hmm.

• 1:10:33Speaker 02

  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 a 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.

• 1:10:53Alie Ward?

  But.

• 1:10:53Speaker 02

  Maybe these are arthropods.

• 1:10:56Alie Ward?

  Because remember, we just spent the last hour establishing that in vertebrates, like arthropods with their exoskeletons do not have odontodes, right? We know those words now, so why are we seeing them?

• 1:11:08Speaker 02

  And everyone who said it was an arthropod kind of got like brushed aside. And another paper came out that used paleo histology 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 odontode. 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.

• 1:11:36Alie Ward?

  Mm hmm.

• 1:11:36Speaker 02

  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.

• 1:11:51Alie Ward?

  Mm hmm.

• 1:11:51Speaker 02

  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.

• 1:12:03Alie Ward?

  Mm hmm.

• 1:12:04Speaker 02

  And I respect these people and. What if they were right? What if, you know, so we scanned 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. 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.

• 1:12:48Speaker 02

  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 addontodes? Yeah. And what are they? What are these like weird bumps that look like addontodes 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 sensile. Sensile are sensory structures? That are super diverse.

• 1:13:29Speaker 02

  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. Are they steady? Yeah, steady, yeah, exactly. So that's a type of sensile, that's a mechanocensor 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 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,

• 1:14:12Speaker 02

  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 odontodes. I'm like, why does it make sense?

• 1:14:19Alie Ward?

  Mm hmm.

• 1:14:20Speaker 02

  And he's like, well, because teeth are sensory. Odontodes 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?

• 1:14:34Alie Ward?

  Yeah.

• 1:14:35Speaker 02

  So you know, your, your teeth are sensitive, right?

• 1:14:37Alie Ward?

  Of course.

• 1:14:38Speaker 02

  You're having some issues with that and like, like a lot of us do, but it doesn't really make sense. Why would you chew with these super sensitive structures?

• 1:14:45Alie Ward?

  Yeah.

• 1:14:46Speaker 02

  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.

• 1:14:59Alie Ward?

  Bonkers. Bonkers.

• 1:15:00Speaker 02

  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.

• 1:15:11Alie Ward?

  Mm hmm.

• 1:15:12Speaker 02

  Because when your dentine is exposed, it's the sensitive tissue.

• 1:15:15Alie Ward?

  Oh, no.

• 1:15:15Speaker 02

  Okay. So now we know odontodes have dentine and we know that teeth have dentine. But we don't know if odontodes outside the mouth are sensitive.

• 1:15:24Alie Ward?

  Mm hmm.

• 1:15:24Speaker 02

  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 odontodes?

• 1:15:31Alie Ward?

  Mm hmm.

• 1:15:32Speaker 02

  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?

• 1:15:42Alie Ward?

  Yeah.

• 1:15:42Speaker 02

  So those guys are covered in odontodes too. They're covered in little teeth.

• 1:15:45Alie Ward?

  What?

• 1:15:46Speaker 02

  Bizarre. And they are super easy to keep and super common. So I went to a pet store and I got a bunch of them.

• 1:15:53Alie Ward?

  Oh, my God.

• 1:15:54Speaker 02

  And started breeding them in the lab to get their little embryos. So we could actually test if their odontodes are innervated, because that would be the first step for them to be actually sensory. If the odontode 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 order division. 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 there. But do modern odontodes outside the mouth have nerves?

• 1:16:31Alie Ward?

  Mm hmm.

• 1:16:32Speaker 02

  So went, collected a bunch of these algae eating plecos, learned how to keep an aquarium. Cause God knows I never had an aquarium. Uh, 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. 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 odontode. All their odontodes were innervated right into the pulp cavity.

• 1:17:11Alie Ward?

  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?

• 1:17:17Speaker 02

  They fight with them.

• 1:17:19Alie Ward?

  What do they do?

• 1:17:21Speaker 02

  They have chicanodontodes that 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?

• 1:17:32Alie Ward?

  No.

• 1:17:33Speaker 02

  Please check me on that.

• 1:17:33Alie Ward?

  Yara later told me that she meant one in 20 or 5% 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 ciliaformology 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.

• 1:18:05Speaker 02

  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 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 odontos. 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.

• 1:18:41Alie Ward?

  With taste buds in between their outside teeth.

• 1:18:44Speaker 02

  Seems that way. Yep.

• 1:18:46Alie Ward?

  Why don't sci fi movies just do a better job?

• 1:18:49Speaker 02

  Just do a biology.

• 1:18:50Alie Ward?

  Yeah, just do biology.

• 1:18:53Alie Ward?

  Horrifying and amazing.

• 1:18:56Speaker 02

  Yep, yep.

• 1:18:57Alie Ward?

  Yikes. And so what happened when you were writing up this paper?

• 1:19:00Speaker 02

  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 sinnsilic. Then we did a bunch of stuff on sharks and catfish to find out. The odontodes were innovated 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 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.

• 1:19:42Speaker 02

  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.

• 1:19:57Alie Ward?

  I'm gonna tell my dentist about this. Do dentists know this?

• 1:20:00Speaker 02

  I tried. I just had a tooth cleaning actually last week and I'm like, hey, I'm 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.

• 1:20:10Alie Ward?

  No.

• 1:20:10Speaker 02

  Please, please, ma'am, ma'am. They shut me down so quickly.

• 1:20:14Alie Ward?

  You're like, you work with teeth, I work with teeth, slightly different eras.

• 1:20:19Speaker 02

  Yeah.

• 1:20:19Alie Ward?

  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?

• 1:20:30Speaker 02

  Uh, but no, I would say the hardest part, that was a 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, and 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.

• 1:21:11Speaker 02

  So that's always sad, 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 uh 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 that would be the hardest part.

• 1:21:33Alie Ward?

  Just you're like head down.

• 1:21:35Speaker 02

  Yep.

• 1:21:35Alie Ward?

  Don't mind the wars, the genocides, the climate change.

• 1:21:39Speaker 02

  Yeah, and and that's tough.

• 1:21:41Alie Ward?

  Yeah.

• 1:21:41Speaker 02

  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.

• 1:21:51Alie Ward?

  Mm hmm.

• 1:21:52Speaker 02

  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.

• 1:22:00Alie Ward?

  Mm hmm.

• 1:22:00Speaker 02

  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.

• 1:22:12Alie Ward?

  And there's always community science too for people to join.

• 1:22:15Speaker 02

  Yeah.

• 1:22:15Alie Ward?

  Right?

• 1:22:16Speaker 02

  Totally. And there's like big science fairs, big volunteer opportunities, yeah.

• 1:22:19Alie Ward?

  Get in there.

• 1:22:20Speaker 02

  Yeah.

• 1:22:20Alie Ward?

  But um 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 uh odontoed goosebumps?

• 1:22:35Speaker 02

  Ooh, odontoed goosebumps. That's 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.

• 1:23:16Alie Ward?

  Oh my god.

• 1:23:16Speaker 02

  Like, 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, 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 fish. It's just weird.

• 1:23:44Alie Ward?

  Discovery is always so, so interesting.

• 1:23:47Speaker 02

  The amount of mental freedom that we have to ask strange questions and go down strange rabbit holes, it is a ADHD-er's, like, dream. Which is why there's so many of us in academia.

• 1:23:59Alie Ward?

  Yeah.

• 1:24:00Speaker 02

  Right? Yeah. So, I, I mean, I love my job.

• 1:24:03Alie Ward?

  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 want to keep your bones around? Or are you, like, throwing me in the ocean, burning me up and grinding me up? I would think about bones differently, where I'd be like, I kind of want my skull to be around after.

• 1:24:20Speaker 02

  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.

• 1:24:34Alie Ward?

  Wouldn't that be cool?

• 1:24:35Speaker 02

  It would be so cool. I, I don't find it, like, obviously, I mean, I work with bones all the time. I don't find it grotesque. I find it so fascinating.

• 1:24:42Alie Ward?

  Yeah.

• 1:24:43Speaker 02

  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.

• 1:24:49Alie Ward?

  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.

• 1:24:53Speaker 02

  Yeah.

• 1:24:54Alie Ward?

  If they can use me. Or just put me in a mud flat and, uh...

• 1:24:58Speaker 02

  And let, let the octopus aliens find me. Yeah. I'm with you.

• 1:25:01Alie Ward?

  Just a little peace sign in a mud flat. Perfectly flattened.

• 1:25:05Alie Ward?

  Yeah, slap me over.

• 1:25:06Alie Ward?

  Yeah.

• 1:25:07Speaker 08

  No coffin, please. Just wet, wet mud.

• 1:25:10Alie Ward?

  Uh, this is a joy, and I'm so glad this has been six years in the making.

• 1:25:16Alie Ward?

  At least.

• 1:25:17Alie Ward?

  At least.

• 1:25:17Alie Ward?

  At least.

• 1:25:18Alie Ward?

  And now you're doctor. Thank you for having me at this beautiful, terrifyingly, uh, dark maze of cabinets known as the collections of the Field Museum.

• 1:25:28Alie Ward?

  They're so lovely.

• 1:25:29Alie Ward?

  Oh, my God. What an icon.

• 1:25:32Alie Ward?

  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 Samir Project at alieward.com/ologies/paleohistology. And remember, we also have kid-safe, classroom-appropriate cuts of Ologies Classics. They're out every week. Just search Smologies, S-M-O-L-O-G-I-E-S, and subscribe wherever you

• 1:26:13Alie Ward?

  get your podcasts. We are at Ologies on Blue Sky and Instagram. I'm at @Alieward on both. Ologies merch is available at ologiesmerch.com. And to submit questions before we record, sign up for $1 a month at patreon.com/ologies. The lovely Erin Talbert admins the Ologies Podcast Facebook group. Aveline Malik makes our professional transcripts. Callie Ardwyer does the website. The smily Noel 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 Chaffee 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

• 1:26:55Alie Ward?

  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 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 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. 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.

• 1:27:40Alie Ward?

  That's how I got my health insurance. And I once had a bit part on Grey'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 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. Fuck eyes. Bye-bye.

• 1:28:22Alie Ward?

  Pachydermatology, omeology, cryptozoology, lithology, nanotechnology, meteorology, geology, anthropology, seriology, geology.

• 1:28:42Speaker 04

  Your teeth. I want to see them.

• 1:28:45Speaker 09

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