Secretly Incredibly Fascinating - Human Teeth

Episode Date: March 9, 2026

Alex Schmidt and special guest Andrew Ti explore why human teeth are secretly incredibly fascinating. Visit http://sifpod.fun/ for research sources and for this week's bonus episode. Come hang out with us on the SIF Discord: https://discord.gg/wbR96nsGg5 Visit http://sifpod.store/ to get shirts and posters celebrating the show.

Human teeth, known for being in our mouths. Famous for being hard. Nobody thinks much about them, so let's have some fun. Let's find out why our teeth are secretly incredibly fascinating. Hey there, folks. Hey there, syphalopods. Welcome to a whole new podcast episode, a podcast all about why being alive is more interesting than people think it is. My name is Alec Schmidt, and I'm very much not alone.

As folks know, Katie is out doing baby and family things. And my guest is a wonderful returning guest from, among other things, the very first episode of SIF. He came through helping the entire show exist. And I hope you know him from, Yo Is This Racist, another show they make called Starter Trek. It's all part of a wonderful and listener supported network called Suboptimal Pods. Please welcome Andrew T. Oh, my gosh. Hi, Alex.

Thank you. Yeah. I'm so glad to see you. That was a more thoughtful intro than any, I have not thought about anything I've done in that way. So thank you. This topic ran away in the polls on the Discord. Thank you to Paul Garaventa, Arcblade, Aenoid, Metal de Terra, and many other folks for suggesting it. Andrew, what's your relationship to or opinion of this week's topic of human teeth?

I have, I think like many people, like a mostly personal relationship to human teeth. I don't have maybe, you know, that's not true. I know that some people really hate other people's teeth or, like, you know, disembodied teeth. So I have very little relationship to that. My own relationship is, I would say, improving greatly as I've gotten a little older. I'm like a very fastidious flosser now in a way that I'm like, oh, I could have been like this my whole life. What was I doing? All this wasted youth.

I learned to floss in my 20s, basically. Yeah. I wasn't doing it. That's, as far as like proper, like correct flossing, I think there's an argument. Mine came later than that. Because I get notes every time I go to the dentist. I think part of it, I will say, the personal anecdote is not that I would say my dentist when I lived in New York was unskilled.

I'm sure they were very skilled. But they were a person who was, I would say, maybe more customer service oriented. This was the time I was like, I think I need a new dentist. She came in and her direct quote words, I will never forget these words were, she looked into my teeth after the hygienist had done it. And she said, great job, Andrew, perfect as always. And I was like, that is not true. I know you are lying to me.

So what else have you been lying to me about? Because I was just like, I know my teeth aren't perfect. What the fuck are you talking about? I never thought of that as like a lie detector. Like I won't really floss. I'll go to this dentist and then I'll see if they're an honest person. Yeah. As far as like my physical teeth go, I believe I'm fine.

But I was just like, the phrase perfect as always set off such massive alarm bells for me. I was just like, well, that's not true. So, uh-oh. I need a new dentist. I need someone who won't gas. I need a non-chat GPT dentist, is what I'm saying. Right, not coded to compliment me no matter what. Yeah, yeah.

Yeah, I just need, just be honest. Just be like, this is fine, this is f***, that's all I want. Wow, we're very aligned. Yeah, I think my teeth are like, fine, but also I have fillings and I've had invisible because my child had done us was like, you'll need braces an hour later. And I was like, later. And my parents went up a little bit. Yeah, they're okay.

But like, it's just that you know, you know they're okay. They're not like, you know, we're probably like 80th percentile teeth because we're just normal people with access to dental care. And it just, I just know I'm not a top teeth person. That feels right. Yeah. This topic is like so personal to everyone. Yeah. So also thank you folks for coming along.

And the suggestion on Discord was just teeth. and then I immediately needed to narrow it to the teeth in humans because animal teeth are a whole range of nightmares and cool things and everything else. God, oh, I'd buy it. And we have a whole giant fun episode about it. And every episode we lead with a quick set of fascinating numbers and statistics. This week that's in a segment called Statistics, won't you count out and play?

Statistics Gweet the math today Hey And that name was submitted by Andy G Thank you Andy G We have a new name for this segment every week Please make them a silly and way I can bat as possible Submit through Discord or to sitpott at gmail.com

And we'll be like in and out of numbers throughout the episode The first one is pretty simple It's either 28 or 32 Either 28 or 32 That's how many teeth most modern adults And the main reason for the variation is wisdom teeth. Have you had yours out? I've had mine out.

Oh, my God. Yeah. Okay. You know what? I'm realizing this is why this is a good show. This is jogging something. You know what? I thought it's probably too casual in the intro.

I think I do have like an outlier mouth. I got my wisdom teeth out relatively, not relatively young. I think there's a good number of people that get them out in their teens, I believe. Teens, okay. But I was told when I got them out that I had like uncommonly long and robust roots of my wisdom teeth. They put me under general anesthetic to take my wisdom teeth out. Which is I'm realizing now quite serious. Like when I was 14, I was like, yeah, yeah, I don't want to be awake for this either, of course.

But like, you know, not kind of realizing how genuinely dangerous, you know, I think most people would consider having a tooth extracted under general anesthetic to be very unnecessary. Wow. You know, just because getting put to sleep, there's always a chance you don't wake up. And my mom, I remember, she told me afterwards, as far as I know, it went fine. And I don't know if this is like an outlier behavior either, or I simply have outlier teeth. But she described the dentist as putting his like shin bone horizontally across my chest to have the leverage to

pull this tooth out. And she like watched, right? Or she heard? Yeah. Yeah, I think, I mean, she said she saw it. So I don't totally, maybe it was like a sword in the stone situation. It was like, it was like a man's entire strength was being leveraged against my wisdom teeth.

Wow. So whatever that is. That's amazing. I can't remember the physical objects, but they were like cartoon Dracula fangs. apparently on the root side. Like, if you'd put them in backwards, you'd be like, oh, that's too much for like a Dracula prop. Like too long.

Like an actor could not physically hold them the other side of their mouth and like deliver a line, you know, wolf fangs level. It turns out people vary a lot with their wisdom teeth. There's not just one common situation. And as soon as I asked you about your wisdom teeth, I was like, wait, I'm violating HIPAA, even though I'm not a doctor. But like it's personal, thank you. Yeah.

Oh, I don't mind. No, I fully forgot all of that stuff. Everything I just told you is to my memory accurate, but that memory is like decades old. And I haven't particularly talked about it with anyone. Like, it's never really come up. So, huh, I think. And your dentist is king of England now.

That's great. Yeah. Yeah, dentists let me know. Yeah, the four teeth held up by the lady of the. Apparently it was real fucked up. Between my memory and my mom's, she is known to exaggerate at times. But this is what I remember. I remember waking up and then sometime in the subsequent weeks being told, yeah, it was crazy.

The dentist was just like, like full body, two hands, you know, leveraging, leveraging your lower body. Whatever that is, that's what I was told was needed to remove my tooth. We'll use the rest of the skeleton. It's cool. It's cool. Yeah. Yeah. Yeah.

People really vary on the size of them. We call them wisdom teeth for almost just an old wives tale reason. They just tend to appear between ages 17 and 25 when you're theoretically wiser and older. But they can come sooner or later or whenever. Yeah. Yeah. And they also tend to be a little bit smaller than your other molars. Wisdom teeth are really a third.

set of molars behind the first and second molars. And also, it turns out there's three ways that can go. Some people, you know, develop wisdom teeth, have them removed. Other people, the wisdom teeth are not crowding your other teeth and they just keep all 32 of their teeth throughout life. And then other people never developed them. Apparently the estimate is about a quarter of the population. Does not develop at least one wisdom tooth, if not all four. That's such odd variance, honestly. It seems like, yeah, I cannot believe that's how they're like, I mean, I guess maybe it's triggered by nutrition or some kind of environmental or genetic factor, but like, oh, I guess it's also like, because for the people who it, quote, unquote, doesn't develop, presumably there is

still a nub of something, or at least the stem cells that could become a wisdom tooth are still there. Yeah, like usually. I would assume. And it even varies beyond that. Yeah. Yeah. Right. Right. Right. So. We'll talk about especially the genetics and evolution later. It's pretty varied. You'd think everybody would kind of have the same situation. But no. Yeah.

Every other part of the body, at least the plan typically is the same. And I guess through most of human history, it's really, it seems like it's probably more of a rarity that people generally have all their teeth. Like I would assume if you lost adult teeth, there would be less danger of crowding, presumably. Yeah. Right. They're spares. Yeah, there's spares from when we ate differently and had bigger jaws before. That's wisdom teeth. Yeah, yeah.

That makes sense. All right, about it. Yeah. And you had great ones. That's awesome. I had, yeah, again, as far as I, my memory goes, I had, I said I'm a top, top 80% percentile, like cleanliness. I am, you know, as far as my memory goes, I'm like a 99th percentile wisdom tooth robustness. Yeah, and the other quick number is about 20, because most people develop just 20 of what are nicknamed baby teeth.

So things like the wisdom teeth are also named that sort of old wives tale name because you don't have baby wisdom teeth usually. Those aren't part of the set that come in first. That makes sense. And it's, I assume, front to back. Pretty much. Is that how baby teeth typically come in? Yeah, okay. That makes sense.

The next number here is one out of 289 babies. It's an estimate. One out of 289. That's an estimate of how many babies are born with teeth worldwide. Oh, God. I don't know why that gave me the willies a little bit. Yeah, I've heard of this, partly because apparently the actress who plays Captain Janeway on Star Trek Voyager was born with teeth. That's the name for biography.

I'm going to write that down. Yeah, tell Taney, and she probably knows. But yeah. And that's one estimate, but I've had a bunch of different estimates higher or lower. That's an estimate from a 20-23 meta-analysis, the digital resources at the Cleveland Clinic lean on. And apparently it's not really understood still why some babies are born with some teeth. Huh. It's possibly genetic is our guess, but also kind of the obvious guess.

And what we do know is that babies who come out with teeth tend to. to have an even number of them in pairs. And also, they often don't need to be removed or receive special care. Like if they're causing the baby pain or are painful for the breastfeeding mom, like biting, you know, they might get removed. But if they're structurally sounds, then doctors will usually leave them. How often, if that isn't the case, do teeth typically come in? Is it like a wide range or is it like, I guess I just assumed that would be an extreme

outlier because I know that they don't start teething right away. So I know I assumed it was like a time that was months post birth. Is that right? And that's true. Yeah. Child development varies a whole bunch, reading a lot about it in life. But apparently around six to eight months, kids will start to get their first tooth. Oh, God. Okay. So born with teeth means significantly early. Yes. Yeah. Yeah. Wow. Okay. Like not completely unknown, but rare. One out of 289 babies. is not that many. Those are called natal teeth as their name. And then there's a somewhat separate thing called neonatal teeth, which is where the baby is born and then teeth and some teeth poke out within the first month rather than like half a year into being alive. So babies vary a whole

bunch. You know what? I'm realizing, I think one of the reasons it maybe gives me the willies is that in the alien franchise, I think one of the more unnerving things is that they're born. with quite a lot of teeth. I mean, I know teeth is like a big problem with them. That's sort of their main evil part. That's one of the unnerving things when you see the chestburster is it has a full grill going on. Yeah.

Because it feels like to me, baby shouldn't have teeth. Newborn things shouldn't have teeth. I'm realizing is what is in my brain. Which probably is not even right for the animal kingdom. It's truly. And we develop pretty differently from a lot of other even mammals on Earth. Like they'll be born with us. a set of teeth and also walk pretty early, you know, and stuff.

And we have much longer, slower childhoods. Yeah. Okay. Ugh. But okay. I hope it's not too much of an uh, because it kind of gets us into takeaway number one. A human can have far more than two sets of teeth. A few different stories about people not being limited to just baby teeth and then adult teeth.

I feel like that's the opposite. That, for me, feels hopeful. Good. That's like, if you get your adult teeth. tooth knocked out, there's always a chance. You got a third spare. There are a few different labs and teams of scientists working on fresh ideas for, yeah, either implanting or developing a next adult tooth for people who lost one. Sure. That makes sense. I mean, it seems like one of those things without getting political

that if we were able to like do more research with things like stem cells without political complication, that seems like it should be on the docket. Of the things you can grow, a nerve and a piece of bone, I know it's not exactly bone, or I just think it's not exactly bone. Like, it just seems like that's easier than growing like a, you know, fucking heart or even like a tendon or anything as far as like things that can be grown. Mechanically, it's very simple. It turns out, and the two teams working on this, one's in the UK, one's in Japan. So I think they're working around some United States politics and stuff.

Or they just live there, but either way. Well, I mean, it's telling. It's not in the United States, I think. There's a few different versions of this kind of thing, where it's not just baby teeth and adult teeth for a person. And the first one to talk about is labs and scientists trying to work on, hey, can we use stem cells or what is in the mouth already to buy. biometically get a third set of teeth.

The team in England here, back in 2013, King's College London, they grew a new, like, human-style tooth. It's made of human cells and mouse cells, which is cool. Honestly, at this point, it's fine. Yeah, I don't mind. I guess you're right. You know, now that we're talking about it, a third set of teeth is literally the whole point of alien. I don't know why I've got alien on the brain, but that's the main problem with those second mouth.

It's a body horror icon. We love it. Yeah, we're really into it. Eds. Yeah. And then this team has just continued to work on newer and bigger things. And in April 2025, they announced new advances in growing, basically the anatomical structures that hold a tooth in place in our mouth.

Because you also need to generate that. That's part of the trick. Yeah. That's probably the real meat of it. It turns out. Even I, a one-time science-educated dummy, understands that the little rock part is not the tough part of getting a human tooth in. Yeah, and even a lot of the enamel is minerals. Like, it really is basically a mothrack.

And that's easy. But the roots and the foundation, you know, there we go. Yeah, the nerves, et cetera. Yeah, I get that. I get that. Yeah, and they say their next goal is to do this with only human cells and none of the mouse cells. and they're also focusing on the foundations because they want people's bodies to not reject what's being implanted. And hopefully if it grows from your mouth, your body will work with it.

And then there's a whole separate approach from a team in Japan. It's medical researchers at a hospital in Osaka. Their goal is to exploit our genetics to make dormant buds of potential teeth that are beneath our adult teeth make another tooth. It turns out at least some of the of us have like a vestigial roots for a third set of teeth going on that just don't get activated. That seems, again, what could possibly go wrong? But like those, yeah, those buds, which again, knowing nothing, presumably are just little clusters of undifferentiated stem cells that can be activated with hormones and mostly hormones, I assume. Almost, yeah.

Mostly hormones and ions. It can't be that much other... Hormones, ions, and pressure. Is that what causes stuff to react to the body? Something like that. I don't remember any biology, really. I'm basically relating what popular mechanics says for this one. But they say that the whole idea is to manipulate one gene

so it does not make one protein. Right. That's it. Right. Yeah, it's inhibiting. Right. But again, if you blanket disinhibit the... second mouth gene. That is how you get a xenomorph. So you do want to be selective with it, which I imagine is high on the list of complications. Yeah, patients aren't really seeking that.

They're like, I'll consider it. But right now I just want the first set of teeth. Yeah. And honestly, it's mostly cosmetic if you do. Yeah, it's a gene that we've named USAG. and it apparently dictates the number of times our mouth grow sets of teeth. And so in 2024, they started a clinical trial in Osaka where they prevent that gene from forming a protein that stops you at two sets of teeth. And there's, I guess, buds already beneath the second set that could be a third set. Yeah.

And they hope by 2030 to be like selling this and doing this in the world. As far as like other ways a person can have more than two sets of teeth, The technical term for most of us, we are a diphyodont. Two sets of teeth lifetime. Diphiodonts. Most mammals are that. Some others grow more teeth or only of or have one set. The technical name for our baby teeth is deciduous teeth, like a deciduous tree.

The leaves fall, the teeth fall. It's going away. Yeah. One of my front, I can't remember which one. One of my front adult teeth came in basically behind the, deciduous tooth. So at one point, I had two teeth. It was one of my front teeth.

I can't remember which one. Like, right here. Just, like, growing in right behind it. So, and the baby teeth was not loose at all, really, before the whole one came in. So I can't remember. I do think we didn't, like, pull it especially. But, yeah, I was, I was xenomorphine for brief time when I was probably like four, five, something like that, six.

I feel like I'm mementoing you about your teeth. Yeah, I really, I really, my, I have, I'm feeling like a very specific antarrograde amnesia, or retrograde amnesia in this case, because I'm not doing new, new teeth memories. This is cool. But yeah. It wasn't like behind it pushing it out. It was like located.

No, it mostly just pushes the previous one out in the same socket. And this one just came in right behind. Wow. Cool. Like two sockets essentially. or I'm sure it wasn't technically two sockets, but like I don't know what was happening because I was six, man.

Right. But I do remember that. I do remember that happening. Yeah, the way our teeth come in can be so specific, there's a whole separate thing where without any of the biomedical stuff we were talking about before,

people can have more than two sets of teeth. The main name for it is Hyperdansha, where people just have more teeth. And apparently if a baby is born with teeth, doctors track that closely because that could mean it's not even a baby tooth. It's just extra supplemental teeth that have come before the baby teeth. And they have more sets coming. And they'll usually use x-rays to just look what's under the gums coming in the future to find out. Yeah.

It makes sense. But it's, I thought you were going to say, you know, again, just based off of this, like, even if it's not a hormone imbalance, it's, it's an atypical, potentially an atypical, like, hormone or nutrition or something situation to have that happen. So I was, I wonder if it's an indicator of anything else, but maybe not. It seems like it could be. Like, it's also just such an interesting presentation that doctors are like, I'm going to learn everything about you now. Let's, let's see what's going on. Yeah. Probably a bunch of shit just gets not self-ro-like. I don't think my thing was, I think my parents were just like, that's crazy. And it just fell out eventually.

So like, you know, who cares? Yeah. And then the last thing here for a way a person can have more than two sets of teeth is a whole separate thing involving tumors. I don't know if you've heard of this, but it's called a teratoma. Yeah. One of my friends had, like, quite a large teratoma. Oh, okay. Which you should explain first, I suppose.

It's something that can be benign or malignant. It's a tumor from germ cells, which are the initial. building blocks of what become our reproductive cells. But if it behaves like a tumor, then the out of control growth and multiplication can make all sorts of human tissue, including teeth. Yeah. But anywhere in the body, not the mouth. My friends, they named it Terry the Teratoma.

That's wonderful. Make friends with it. I've made little, little, yeah. And apparently they're basically always removed by doctors once detected. Like even if they're benign, it's just something to remove. And they can develop all sorts of tissue. And the most common types are apparently muscles, fats, hair and teeth. Yeah.

I think hair and teeth were in this one. And it's just sounds gross, but, you know, what else? Yeah. I don't know if it is gross. I looked up pictures. I shouldn't have because I don't do well with that stuff. But if you like interesting anatomy folks, you should look up pictures because they're out there. And there's not a picture of this, but apparently in 2008, a medical journal did like a

case study of one. The journal is oral and maxillofacial pathology because they did a whole article about one massive and benign teratoma in a 25-year-old woman. They described it as having greater than 300 teeth without specifying. It was just a greater than symbol. Like they didn't finish counting. Yeah. You could probably greater than 50 it. And it's already one of the worst things that I personally. So it's, you know, it's, yeah, gosh, 300. It's such an insanely large number.

Right. And like the good news is their study, they feel based on what they found that if a teratoma has clearly defined teeth, that is, quote, indicative of benignity, benidity. Basically, if a teratoma has entire human-looking teeth on it, probably not cancerous, is there finding. Which would be good news. Like, if your Teratoma's super toothy looking, it might be okay for what it is. Yeah. Right. Like many things, it's like, just because you're scared of it and find it unnerving doesn't mean it's evil. That's, yeah. Many Pixar movies are about this. Yeah. So I really just thought of all people

as having baby teeth and then adult teeth and there's so much more going on. It's, yeah. And back to more numbers here. We mentioned teeth being sort of like rocks. The number there is 97%. Apparently the enamel in our teeth is 97% minerals. Right, because they're not bone. Yeah, they're not bones and they are stronger than our bones. Like they are harder. They're considered the hardest substance in the entire human body, our teeth. That makes sense. But it's also an extremely hard mineral enamel layer over much softer layers. There's dent in and then there's pulp. That's why your teeth can be sensitive and harmed. It's not just a rock. Right. It's coated in a rock. It's like an M&M. It's like a bone M&M with a rock, a delicious rock coating. I just imagine it being

labeled T and T or something. Yeah, that makes sense. Yeah. And that enamel is crucial to your dental health, and apparently it has a limited ability to repair itself. It does not grow back in a large scale way if it's damaged, but because it's 97% minerals, we can supplement it with natural minerals like fluoride to rebuild it at early stages of decay. Obviously, in the interest of both sides of the political spectrum, you should say allegedly or whatever. Are we a fluoride? Right, right. The fluoride mind control stuff, just lovely stuff. stuff, really. It's both a throwback and I guess it's just back. We're back at witchcraft times. Yeah, and like specifically because of RFK Jr., the U.S. Health Secretary, because apparently the number there, November 2025, that is when a team at several U.S. universities working together, like hurried to publish a decades-long study in the journal Science Advances.

They followed more than 25,000 participants across decades and found no evidence of fluoride having any impact on children's IQ, positive or negative or anything. Fluoride doesn't control your mind, doesn't harm you. It's a public health good that helps people. But even before, I know it's like RFK Jr. specifically, you kind of like pin this on because he's obviously made himself the face of it. But like the fact that they had to do this study was entirely born out of, you kind of. like, I'll just say right-wing paranoia, more or less. I guess there's probably left-wing paranoia involved also at some level, but like what has coalesced into right-wing paranoia?

Like, fluoride controls your mind is not based on anything, and yet they had to do a 20-year, 20,000 person millions of dollars of study? It was 41 years, actually, yeah. Yeah. So, like, tens of millions of dollars potentially, or like, you know, millions of dollars worth of, research time to just prove something that is not, like the contrapositive is not real. Right.

This is the cost of just debate me, bro. Like, oh, you're defending, you know, this is, this is a decades long just debate me over something that wasn't, it's not real. Yeah, like if you've seen the movie Dr. Strangelove, it depicts someone worrying about fluoride and water in a paranoid, bizarre way that has no basis in anything. Yeah. Oh, my God. It goes back. Yeah, but to attempt to assuage that person's paranoia, you have to do a 41-year study. And guess what? Still not assuaged.

Yeah, and then the other number, a team at Harvard in May of 2025, very specifically because Robert F. Kennedy Jr. is now the health secretary, they just modeled out what would happen if we stopped fluoridating water in the United States. and by the way, apparently only about 62% of the population in the U.S. drinks fluoridated water. We just haven't extended it to the whole system. But if we removed it from the people who have it, apparently just young Americans, ages 19 and under, just that group, there would be 25.4 million more cavities and tooth decay and other dental needs is what they estimate. And they figure that would cost about $9.8 billion. in dental costs, not counting the additional cost to parents not being able to work while they do the driving to the dentist and so on. Yeah. Yeah. So people are being as clear as humanly possible about this.

Yeah. Yeah, yeah, yeah. Well, you know, of course, the counterpoint is you can drink raw milk in a hot tub. So, you know, got to, got to consider both sides is the important thing, Alex. All I heard is hot tub. Let's go. But yeah, and the way our teeth are enamel coated and then very soft on the inside, it's just fascinating. And it gets us into another amazing thing from the distant past. Because takeaway number two, there's a theory that human teeth evolved from the sensitive armored scales of an aquatic animal. Okay. That makes sense.

Right, because they're not simply more jaw. Yeah. And they can feel pain and temperature in a way that was probably helpful to swimming creatures 500 million years ago. Right, right, right, right. Yeah. Instead of just being like impervious chomping things that would be kind of helping that way. Right. It is a little crazy that teeth are basically like a knife that feelings can be hurt, which is like kind of bonkers.

Like of the tools, that's one of the weirder ways to make that tool. My friend wrote a comedy sketch about the battle droids in the Star Wars prequels because they scream when they get shot. The droids are arguing, why do I feel pain? Why did you do this? Yeah. It's really like, there's no reason to do any of this stuff. I mean, again, that's intelligent design for you, I guess. We put a very finicky heat and pain sensor in our razor blades in our mouth.

Yeah. And then invented Coca-Cola. God made Coca-Cola. Yeah. Yeah, so this theory, the source is University of Chicago evolutionary biologist Yara Haridi. She published an article about this in the journal Nature in 2025. And it's very strange that our teeth are fragile in this.

in this study, they explored it by examining ancient aquatic species from about 500 million years ago. Because they wanted to get back to when vertebrates evolved. Before it was just weird invertebrates with exoskeletons and stuff. And they said, let's look at the beginning of vertebrates. And in particular, they looked at the fossils of an animal called anatolepus, which is aquatic and invertebrate. it just had an exoskeleton of scales. Okay. And then the shortest version of this is the scales can sense the temperature of water.

There's a lot of nerves inside the scales. And then amazingly, the scales are structurally similar to the teeth of the first vertebrate fish. Okay. So right. So it's like our mouths are kind of just folded in scales. Yeah. On the inside. Yeah.

Like, we selected for scales also being used to divide food and, you know, like clamp onto something we're trying to eat and purposes like that. The easiest way to describe this era 500 million years ago is sort of a weird ocean of a bunch of little wiggly stuff. Yeah, yeah. It's like so early in evolution, nothing like us was around. Yeah, everything's a soup. And right. And the fallacy is to think, how did feathers become hair? And the reality is like some weird scale maybe became both.

Yes. Yeah, exactly. Right, right, right. Yeah, apparently an Adelaipus is sort of like an aquatic arthropod. Almost like a spider or scorpion or something. It's not, it doesn't feel like a member of our family tree, but it is. I know I'm just like pop culture only, but it's very sarlac to me. It is very sarlac.

Yeah, yeah. Yeah. Or I guess what you would imagine that like scales becoming a mouth is. Sarlak, just like a big fleshy thing folding in on itself. And Yara Haridi also says these creatures both didn't have great eyesight and lived in very muddy, shallow waters. So because they weren't seeing while they needed every other sense they could get. And so these scales with nerves in them is basically worth the pain of how it feels if that

gets attacked in order to sense as much as you can around you. Yeah, yeah. Yeah, that makes sense. I mean, you know, it's the same as just our skin has noceoceptors for the same reason. It's like, got to know. Got to know if something's cutting you. Totally. It's worth the hurt to get the information.

Yeah. Yeah, and then they've compared. That's a fact. It's always worth the hurt to get the information. That's the SIF promise. I'm like trying to stop a marketer from putting that out. Like, no, no, no, it's bad. It's bad.

We're a fun show. We're a fun show. Yeah, and then this team, they did some extra comparing the early vertebrate fish's teeth to modern teeth in sharks and catfish and other fish now. They all have nerves in them, and this theory, which could always be proved or disproved, is that water, like, water temperature sensitive scales were the origins of what eventually became teeth and humans and other species. And so that's why they're so sensitive. That's why they're so harmful. We've got to go to the dentist. But I guess it also makes sort of sense because, like, if you, you know, think about it, your teeth are one of the main interfaces your body has with the outside world.

Like, that's the first contact for all of your food mostly, I guess your lips. But yeah. And that's the shit that you're bringing in from outside. So it's so useful to feel stuff. Yeah. Yeah. Well, that's a thing. I guess it's useful to feel stuff,

but it's crazy to put them in the same contraption. Because like if you have like a threshing machine, right, like it has a sensor before the teeth to say like, hey, this thing might damage your teeth or damage your tummy. You know, maybe. Maybe not, actually. But like that would be the place to put it

is before you get to the daggers, not inside, not concurrent with the dagger stage. Yeah, the mouth needs some kind of waiting room. more processing space. Again, a second smaller mouth to provide information. They're perfectly designed. Yeah, they really are. Yeah.

And folks, that's a ton of numbers and two takeaways. We're going to take a quick break, then return with takeaways about almost all of human history and teeth. We're back and we have two more takeaways for this main show about human teeth. And if you somehow miss the first half of the show, I'm with Andrew T, our wonderful guest. Hello. And let's get into takeaway number three. Almost everything we know about human evolution specifically comes from fossil teeth.

Oh, sure. They stick around. Yeah, they're the hardest part of not just Homo sapiens' body, but a bunch of other hominens. It's basically all of what we have of evolutionary history. That makes sense. Yeah. Again, yeah, the Little Rock's last longest. Yeah.

I'm just pitching taglines for your show now. Little Rocks last the longest. It's a tagline for teeth. Like, we're selling teeth. And Alex is selling teeth. That's the important thing. I'm building a Bone Temple and then I sell the teeth. I don't need the teeth.

I just need the bones. Because crucially, not the same thing. Bone Temple only. Bone Temple only. No teeth. And key source here is a lecture by evolutionary biologist Tanya Smith that she did at Harvard's Peabody Museum, also linking Smithsonian Magazine for coverage of some studies. Especially with human evolution, almost all of our findings are teeth. Apparently, if you are in this field, you have access to thousands and thousands of old teeth, very few skulls, let alone skeletons. teeth is really all that's left and then they try to learn as much as possible from the teeth.

Bite analysis as like a modern forensic crime thing is wildly inaccurate and essentially pseudoscience. And I was like, oh, but I wonder if the confidence for bite analysis comes from like anthropology and evolutionary studies. It's like, oh, this is where all the information is. It's like, well, maybe, but not on a individual human level. That's all done on, yeah. I'll bet that's true that they decided the shape of the teeth in one modern individual's mouth as some kind of skeleton key to everything.

Yeah. Yeah. Yeah, because we do have basically just teeth for our earliest ancestors. And then in the rare cases where we find more, the teeth are still very helpful. And a big example is Lucy. Lucy is the nickname of an Australopitheca skeleton found in 1974. and not complete, but so much of a skeleton that it was world news that they found it. Right.

And apparently, even with Lucy, the teeth are the most helpful part. They analyzed carbon signatures on the teeth decades later when we had that technology and learned that Australopithecus had moved from the trees to living on the ground based on traces of what Australopithecus was able to eat. The other side of it is it's just there's more data to compare. it against, because there's other teeth, maybe. Yeah, that too. Like the complete skeleton of it.

You just don't have as many complete skeletons or whatever, femurs or skulls to compare throughout history. But again, a lot of bags of rocks. I'm realizing the character of the tooth fairy is much more interesting than I thought. The tooth fairy has all the data for human and non-human evolution, it turns out. They kind of would. Yeah, like even the loose. layers of a tooth can tell us what happened to various people at various times in their lives.

It turns out there are very recent studies of the DNA of stuff left in teeth from historical periods. Like in 2018, people looked at teeth from 1500s, Meso America to figure out the exact type of salmonella virus that caused a pandemic at the time. And in 2025, people looked at teeth from Napoleon's army and figured out which two, two kinds of fever killed the most people in the retreat from Russia in 1812. It's just loaded with information. Yeah, makes sense. I guess it would be like anything, but it's the hard drive that you have that matters. Yeah, yeah, the way it layers and develops and is kept, we can just learn so much.

And then the rest of the body, I don't know, there's some stuff, but that's about it. Yeah. Fair enough. And teeth are our oldest evidence of any members of the homo genus, and they were found in East Africa. They're from 2.5 to 3 million years ago. It helps confirm that humans probably first evolved in Africa than spread to the rest of the worlds. And also, we have found through teeth a general evolutionary process as we got to Homo sapiens, where jaws probably got smaller, but also we kept having the same amount of teeth, which plays a role in the crowding and the wisdom

to eat stuff we talked about before. Yeah. Hell yeah. That's my favorite part. Like in somebody like a Neanderthal or a homo erectus, that third molar was just useful for eating and no problem. They had a bigger jaw.

No problem. Like many things. There's just maladaptive things based on a modern homo sapient lifestyle and nutrition, presumably. Yeah, that's kind of part of it too. Yeah. Yeah, like also apparently

Australopithecus, we found that they started to have a thicker tooth enamel in their species because they were eating seeds, nuts, roots, other like really hard stuff from the ground level of their habitat, rather than fruit and other soft stuff in the trees. Oh. Basically everything we know about our ancestors is from the teeth. We've just deduced it from that, and the rest of the body's not as helpful nearly. Well, we don't got it.

Yeah. Yeah. What are you going to look at? All right. And because teeth are this harder enamel, it tends to tell us basically everything about the migration of people across the earth, not only that we probably evolved in Africa, but also we just keep having new learnings about when people migrated to new parts of the world. Apparently in 2015, researchers looked in a cave in what's now southern China. They found just teeth from Homo sapiens. And because the teeth were older than expected, that altered our estimate of when people came to East Asia.

Asia by 35,000 years. Oh, sure. Just a handful of teeth. I mean, it's the calling card. They figured out everything. It's the calling card. It's what we got left. Yeah, well, we're going to leave behind.

You shall all be teeth. I like the idea of them as a souvenir or a goody bag or something. Yeah, like here, thanks. Yeah. It kind of is. And also, our approach to our own teeth gets us into one. last takeaway for the main show because takeaway number four, human dentistry techniques probably paved the way for horse culture in humans.

We needed that once we figured out how to take care of our own teeth and remove our own teeth, we were able to do almost like a wisdom teeth removal to horses' mouths that helped us ride them. Oh, okay, right, because of the bridle? Yeah, the bridle and the bit. The bit? Exactly. Yeah. The main source here, it's a 2018 study published in PNAS.

Author is William Taylor of the Max Planck Institute. And folks have heard the SIF episode about Spurs recently. We talk about horse domestication. Apparently that started 4,000 years ago. And it probably took more centuries for us to ride them. Initially, they were dairy animals. We kept them for horse milk, you know. Yeah.

Which I would like to try, I guess. You probably do it in Mongolia, right? This story's from Mongolia, actually. Yeah. Yeah. Seems Mongolia. Yeah, it feels like it. Yeah. And apparently, a little more than 3,000 years ago,

that's the age of our earliest evidence of humans doing horse dentistry, trying to alter the tooth of a horse. And it might have happened earlier. It's just what we've got. Someone tried to relieve a horse's toothache. And we think so because it's a horse's toothache. with a notch cut into the side. We think they were trying to give it a new flat surface to chew with.

But also either their tools weren't good enough or the horse wouldn't hold still, so they didn't cut through all the way and probably failed. God. I mean, just imagine pre-anesthetic horse dentistry. Yeah. It seems really hard. It was 1,150 BC around then. So we didn't have a lot of gear or, I,

yet. No. But then they had a much bigger idea, which is that apparently humans are not the only, you know, mammal that has extra teeth in its mouth from a previous evolutionary stage. And horses have a pair of extra pre-molars. Oh. And if I recall, horse teeth are quite large. Yeah.

And these two extra are tiny because they're not used for eating anymore in, like, like modern domesticated horse species. And they're confusing nickname is Wolf Teeth. So I'll link it, but if you Google horse wolf teeth and don't find some weird hybrid animal that somebody drew, you will find a diagram of this. Horse, wolf, teeth. Not your random passphrase generator, unfortunately.

Oh, yeah. Horse, wolf, teeth, balloon, apple. Yeah, and I'll also link the past Siff about toothpicks because we talk about the earliest human attempts to do dentistry on ourselves. We figure that people figured out how to remove something like an impacted wisdom teeth in ourselves and then applied that to the wolf teeth of horses. So around 750 BC people in what's now Mongolia started removing the wolf teeth of horses, which doesn't stop them from eating and does. helped them take a bit and a bridle much more easily and then paved the way for an entire, much larger horse riding and domestication culture. It is sort of just like maybe not sunk cost fallacy, but it's also just like the investment

idea. Like you figured out again how to do horse dentistry, you're getting every ounce of value you're going to add to this horse. Yeah, like whoever unlocked this said it's much easier to ride a horse now and changed all of history. That's cool. Yeah. Yeah. Yeah. Yeah. Pretty good. And they're already a domesticated horse. It's not a big change. Yeah. Yeah. It's cool. But now they're a car. They used to be just for milk. Now they're a car. Or motorcycle, I guess. Oh, true. More of a, yeah, more of a biker. Yeah, sure. Yeah. Just the, the leather vest has lettering of horse dentist or stuff. Like some really not hardcore. Hors Dentches is the house.

Folks, that is the main episode for this week. And I want to thank Andrew T. again, for coming through and making this episode happen. Suboptimalpods.com is where you can find his work and Tawny Newsom's work together in a listener-supported way. They're doing Starter Trek, which is a wonderful show about the biggest Star Trek episodes, which Tani is very versed in. Andrew is very not versed in and it's an exciting show to get to hear. And of course, yo is this racist is Andrew and Tani's very long running and wonderful podcast. And hey, you're in the outro of this podcast.

We've got fun features for you such as help remembering this episode with a run back through the big takeaways. Takeaway number one, a human life can have far more than two sets of teeth. Takeaway number two, human teeth may have evolved from the sensitive armored scales of an aquatic animal 500 million years ago. Takeaway number three, almost everything we know about human evolution and a lot of new information about history, specifically comes from teeth. Takeway number four, human dentistry techniques paved the way for horses' wolf teeth removal and an entire 3,000. year culture of equestrian people. And then a lot of numbers throughout this show about wisdom teeth, baby teeth, the enamel that is the mineral that puts our teeth together, and more.

Those are the takeaways. Also, I said that's the main episode, because there's more secretly incredibly fascinating stuff available to you right now if you support this show at maximum fun.org. Members are the reason this podcast exists, so members get a bonus show. every week where we explore one obviously incredibly fascinating story related to the main episode. This week's bonus topic is George Washington's teeth. I tried to find the weirdest and most famous set of teeth in the world. And George Washington's teeth take the cake.

Also might have decayed from cake. Visit sifpod.f.fod.fun for that bonus show, for a library of more than 23 dozen other secretly incredibly fascinating bonus shows and a catalog of all sorts of Max Fun bonus shows. It's special audio. It's just for members. Thank you to everybody who backs this podcast operation. Additional fun things, check out our research sources on this episode's page at maximum fun.org. Key sources this week include a ton of wonderful science writing.

Special thanks to writer Andrew Paul for popular science, writer Tim Newcomb for popular mechanics, and a lot of writers at Smithsonian Magazine, especially Lorraine Bosenwa, Margarita Bassi and Alexa Roblesquil. We also use digital resources from the Cleveland Clinic and from the American Dental Association. And then a lot of interesting studies. That teratoma with more than 300 teeth was written up in oral and maxillofacial pathology. That theory about the scales of an aquatic arthropod was in the journal Nature in 2025. Lead author there is University of Chicago Evolutionary Biologist Yara Haridi.

And if you'd like to hear or read a lecture all about the evolution of our human teeth. Check out a lecture by Dr. Tanya Smith, given at Harvard's Peabody Museum. That page also features resources such as native-land.claan.ca. I'm using those to acknowledge that I recorded this in Lenape Hoking, the traditional land of the Muncie-Lenape people and the Wappinger people, as well as the Mohican people, Skadigoke people, and others. I also want to acknowledge Andrew recorded this on the traditional land of the Gabrielino Ortaongva and Keech and Chich and Chum people's, and in both of our locations, as well as many other locations in the Americas and elsewhere, Native people are very much still here. That feels worth doing on each episode and join the free SIF Discord, where we're sharing stories and resources about Native people in life.

There is a link in this episode's description to join the Discord. We're also talking about this episode on the Discord, and hey, would you like a tip on another episode? because each week I'm finding you something randomly incredibly fascinating by running all the past episode numbers through a random number generator. This week's pick is episode 193. That's about the topic of the middle finger. That middle finger gesture people do. Fun fact there, there is a gigantic statue of a strange middle finger

in the center of the Italian city of Milan. So I recommend that episode. I also recommend my co-host Katie Golden's weekly podcast Creature Feature about animals, science, and more. Our theme music is unbroken, unshaven by the Budoz band. Our show logo is by artists Burton Durand. Special thanks to Chris Sousa for editing this episode. Special thanks to the Beacon Music Factory for taping support.

Extra, extra special thanks. Go to our members. Thank you to all our listeners. And if I'm honest, I am sorting out whether there will be a new SIF episode next week, because I might be on parental leave next week. We're going to see either way next week or in the future. We will be back with more secretly incredibly fascinating. So how about that?

Talk to you at some point is where I'll leave it. Talk to you at some point. Maximum Fun. A worker-owned network. Of artists-owned shows. Supported. Directly. By you.