Science Friday - Conversations, Baby Teeth, Tasmanian Tiger. March 5, 2021, Part 2

Episode Date: March 5, 2021

When Is It Time To Say Goodbye? Imagine you’re having a conversation with someone. You may get the sense that they have somewhere else to be. Or you might start feeling restless, and use an excuse to cut the conversation short. Sometimes, you feel like you could talk for HOURS. Chances are you’re wrong every time.  In a study published this week in the Proceedings of the National Academy of Sciences, Adam Mastroianni and colleagues tried to figure out how good humans are at judging the ideal length of a conversation. They found that both participants agreed a conversation ended at the right time in only 2% of their trials. And the difference between one partner’s desired conversation length and the actual length of a conversation could be as much as 50%—so in a 10 minute conversation, your partner might have wanted to talk to you for as little as 5 minutes, or as much as 15 minutes. SciFri’s Charles Bergquist talks with Mastroianni about these results, and why the “exit ramps” to a conversation are rarely where you want them to be. Talking Through The History Of Our Teeth Most of us have never thought much about why we have teeth. But if you’re the parent of a teething infant, the question becomes a whole lot more relevant: While you impatiently wait for baby’s teeth to poke through, or soothe your teething toddler in the middle of the night, you might find yourself wondering why humans go through all this trouble for a set of teeth that are only temporary. In a decade, your child will have shed their baby teeth to make room for their adult counterparts, and all this fuss will be but a distant—albeit painful—memory for both you and your former infant. But one such question can lead to another. Are baby and adult teeth made of the same stuff? Why can’t we just grow a new tooth if we lose one? And how did ancient people take care of their teeth? Biological anthropologist and ancient tooth expert Shara Bailey joins Ira to discuss why our teeth are the way they are.  A Look Back At The Time Of The Tasmanian Tiger Last week, conservation biologists on Twitter were all aflutter as rumors circulated that a creature called a “thylacine,” better known as a “Tasmanian tiger,” had been caught on camera in the Tasmanian bush. Thylacines have been considered extinct since the mid 80’s, but there are still those who believe—or hope—they still exist.  In a video posted to YouTube, Neil Waters, President of the Thylacine Awareness Group of Australia, shared the news of what he thought looked like images of two adult thylacines and a baby. Unfortunately, this time the animal caught on camera was identified as a pademelon. But at Science Friday, we’ll never pass up an opportunity to celebrate a charismatic creature. Last January, SciFri’s Elah Feder spoke with Neil Waters and Gregory Berns, a psychology professor at Emory University, about the fascinating history of the Tasmanian tiger.  Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I am Ira Flato. A little bit later in the hour, everything you wanted to know about baby teeth and an update on the hunt for the Tasmanian tiger. But first, a conversation about conversations. Here's high fries Charles Berkwis. Hi, Charles. Hey, Ira. All right. So fill us in on this. What's this all about? Well, you talk to a lot of people on this show. So I'm going to regard you as the in-house conversational expert. Oh, really? Okay. Go for it. How do you know when a conversation is over, when you're done talking to somebody? Well, I think that when I've asked all the questions and heard all the answers, usually my conversation is over. Okay, that's fair. But imagine that it's not an interview. You're not going for some specific piece of information here. This is just a random social situation, like you're chatting with someone at a picnic or a party, if you remember what those are like. Oh, yeah. Well, back when we were doing that, if I recall you would chat until there's sort of an awkward, paused and people are looking at each other. What do I do now? And then somebody will say,

excuse me, I need to refill my drink and then you're out. Right. Or take an important phone call, something like that. But have you ever been in the nightmare scenario where you drop that escape line and the other person just doesn't pick up on it? They follow you into the kitchen or whatever and they're still talking. Oh yeah. I hate when that happens. So it turns out people are universally bad at judging when to end a conversation. Their ideas and the ideas of their conversational partner just aren't in sync. Adam Astriani is a doctoral candidate in psychology at Harvard University. He wrote about this conundrum this week in the journal Proceedings of the National Academy of Sciences. I asked him just how bad we were at this and whether or not it was

possible to pin a number on it. The number would be 50%. So the difference between what people want And what they get is about 50% of the length of their conversation. Now, that doesn't mean that all conversations that people would prefer that they were half as long as they were. It means that what people want and what they get differs by half of the length of the conversation. That's more or less. So if I have a 10-minute conversation, my partner might have wanted it to be either five minutes or 15 minutes. I like to think of myself as a pretty sensitive person and good at picking up these social cues. Am I really?

I'm off, but that's a huge error bar. Yeah, well, it's possible that you are the world's only conversation savant. That is possible. But what we find is when most people try to guess when the other person wants to go, they're off by even more than half of the length of the conversation. They're off by more than 60%. So did anybody get this right? So there's this sort of unicorn 2% of conversations where both people come out saying it ended exactly when we wanted it to. If we loosen our restrictions just a bit and ask in how many conversations, does at least one person say it ended? when they wanted to, that's 30% and 30% of conversations. One person comes out saying that was good for me. In the remainder, both people say it didn't end when I wanted it to. And for most people, it's pretty far from when they wanted it to. Walk me through how you figured this out, the studies that you did. Yeah. We ran two studies. In the first study, we had a big sample of Americans and we asked them about their last conversation. We asked them, how long was it? And was there any point at which you felt ready for it to end? If they said, yes, we asked, when was that point to the nearest minute? If they

said no, asked how much longer did you want to go? In our second study, we asked those same questions, but we brought people into the lab and have them have a conversation in our lab. And what we found was that most people said, I did feel ready at some point, and it was before the conversation ended. But a full 30% of people said there wasn't any point when I felt ready for the conversation to end. I wanted more. Interesting. So it's not that we all just get bored with each other sooner than the other person would expect. Sometimes people are skipping out when the other person still is looking for more out of that interaction. Exactly.

Sometimes both people leave wanting more. One of our most striking results is in the lab when people have a full 45 minutes to talk. And by the way, plenty of people talk all the way to 45 minutes and we have to cut them off. But even people who leave sooner, 10% of the pairs in our second study who spoke in the lab, both left the conversation wanting to continue.

And they could have continued. And we think this is probably because they thought, or at least one person thought, the other person wanted to go. And so they decided to let them go. even though neither of them wanted to go. I feel like people are pretty good at picking up certain social cues, like this person is maybe lying to me or, gee, this situation feels somehow unsafe.

Why are we so bad at this one? That's funny. I mean, people are actually not that good at picking out liars. They tend to assume that people are telling the truth much more often than they are. But I think of this not so much as people being bad at picking up cues. I think of it as us being very good at hiding the cues. So when you feel ready for a conversation to end, you generally don't tell anybody that, at least not until much longer after you've felt that way. You might do things like shift around a little bit or break eye contact or maybe not reciprocated question, all things that are pretty ambiguous.

You can be doing those things for a lot of different reasons. Maybe you're thinking. Maybe you're distracted. Maybe you really do want to go. But it's hard for me to know on the other side of the conversation, which I think is why it's so hard for people to tell when someone else wants to go. So it's not that I'm bad at reading you. it's that you're really good at politely fooling me. Yes, I think we're very good at being polite. And politeness is an interesting word for it,

because I think we think of politeness as a thing that we do with strangers, but we find the same results for strangers and for friends and family members and spouses and lovers in our studies. And I think it's because the word politeness means one thing when we're talking to strangers, but we do the same thing with the people that we love, and we call it kindness. But it's the same thing fundamentally. So is this just a problem of me knowing, what the other person cares about in the conversation, or is it that we want two completely different

things? It's both of those things. So we find that people rarely want to leave the conversation at the same time, which is what creates the problem in the first place. We can't both get what we want if we want different things. Now, normally when people want different things, they try to compromise, but in order to compromise, I need to know what you want and you need to know what I want. And so not only do we have this coordination problem, but we have no way of solving it. Does it matter who in the conversation is speaking? Like, if I'm talking a lot, do I naturally think the conversation is going better than it is? It's a complicated question.

I don't know if we know the answer. We do know at least that it doesn't really matter who ends the conversation. And so maybe by extension, it doesn't really matter who is doing more of the talking in the conversation. When we ask people afterward, who took the first step toward ending the conversation? In 90% of pairs, people agree on who that was. That wasn't a given. It could have been that everybody claims that they were the prime mover. But in general, people agree on who it was who started the closing ceremonies.

But when we look at whether it makes a difference, whether you were that person or whether you were on the receiving end of the end, it doesn't make any difference. It's as if we all saw the exit on the highway. And one person said, we should get off there. The other person said, we sure should. And that's where it ended. It just, unfortunately, that exit wasn't exactly where either of us wanted to exit the highway. So those conversational exit ramps, that's things like, oh, you look at the time or I, really need to go check on people in the kitchen and see what they're doing, or that sort of thing?

Exactly, yeah. So the thing about a conversation is it is a lot like driving down the highway. You can't just leave whenever you want to, at least not without causing a lot of damage. You're going to run into a tree or a storefront or into a ditch. And conversations are similar. There are pretty strong rules about when you are allowed to leave. You can't leave in the middle of someone's sentence unless there's some kind of emergency. You can't leave in the middle of a story. And even broader than that, you're sort of supposed to reciprocate questions. And you could really just feel that most of the time in a conversation, it's not an appropriate time to go, all right, see you later. We think there's a lot of distance between those exit ramps.

And that's why we get off on them sooner than we want to or later than we want to, just like when you're on the highway, you wish you could get off exactly when you want to do and go straight to your destination. But often you have to wait a couple miles or get off a couple miles early. I'm thinking about good friends who have known each other for a long time and they're together. They may chat for a bit, and then there's just that long companionable silence while they're doing something, and then they start talking again. But then when we're dealing with somebody that we don't know, that's not a thing. That would not be natural, right? To be silent with somebody that you don't know in a conversational setting. Do we know anything about that?

I don't know if we know anything about the silences that arise in conversations between friends versus between strangers. My intuition is that the reason you can have a silence with a friend is because it's not really in question whether you like them or they like you. Whereas with a stranger, you don't necessarily know that a silence might mean that they're ready to be done talking to you. And you might know that that's not the case with a friend. I think a good thought experiment is talking to a stranger on a train where you know that. if you stop talking, it's not because you can walk away. And so you might drift in and out of conversation. And it doesn't necessarily say anything about how much each party likes the other. He says more about the constraints of the situation. Right. We've all been spending a lot more time

interacting online these days. How does that play into this? Is there any difference in online communications versus in-person communications? We don't know for sure if this is different online. All of our studies we ran pre-pandemic. Now the idea of talking to some many face-to-face sounds both quaint and desirable. But my guess is that it would be if we weren't in person for a few reasons. One is that even though we're not great necessarily at picking up the cues, I think mainly because we're good at hiding the cues. There are even fewer cues. You don't get to see people's eye contact as well. You don't see their body language. But maybe more importantly, there's no plausible reason to end a conversation when we're online. If I were to tell you that I'm

ready to be done talking to you, what am I going to go do? Go stand alone in my kitchen. There's nothing really going on, so I don't have any excuse to get out of this conversation. Are the people that you would say, this person is a great communicator, necessarily better at this conversational judgment than other people? We don't know for sure. There's some research from some of our colleagues at Cornell where they asked a whole dormful of people to nominate who the best and worst conversationalists were. What they've told me is that pretty much everybody gets nominated as both the best and the

worst, which suggests that there's maybe not such a thing as, a great conversationalist. There's a great conversationalist for you. And I think the mark of a great conversationalist is someone that makes you feel liked, that makes you feel good, that makes you want to talk to them. And that might be a different person for each person. Do you have any tips for how we can become better at this? I don't necessarily have a tip for how people can become better perceivers. I do have a tip for how people can end their conversations more gracefully. And I think it's by addressing the problem of parting head on. So the reason ends of conversations are so fraught is because it feels inherent to the parting of our ways that something has gone

wrong. Otherwise, we'd still be talking to each other. If we really liked it, why don't we just keep doing it? And so I think a lot of the energy that we put into ends of conversations are trying to overcome that problem. I think the best way to do it is to address it head on by saying, I had a really nice time talking to you. I'm looking forward to talking to you again. You don't have to lie. You don't have to say, I've got to be somewhere, but just address the fact that this conversation isn't ending because anything went wrong. It's just that sometimes in the course of human events, two people have to stop talking to each other and do something else. And this is one of those times, but I'm glad for the tie that we had together.

I'm going to cheat and look at the clock. Yeah. And that tells me that it is time to end this conversation. Do you agree? I think this conversation is ending exactly when I wanted it to. It's been lovely talking to you. Adam Mastriani is a PhD candidate in psychology at Harvard University in Cambridge, Massachusetts. For Science Friday, I'm Charles Berkwist.

Thank you, Charles. After the break, a conversation you'll not want to avoid, but really want to sink your teeth into. Baby teeth. Stay with us. This is Science Friday. I'm Ira Plato. Raise your hand if you pay close attention to your teeth. Now, raise your hand if you're a parent of a teething infant. The difference becomes painfully obvious, doesn't it? For you parents, while you impatiently wait for babies's teeth to poke through or soothe your fussy-teathing toddler in the middle of the night, you might find yourself wondering why humans go through all this trouble for a set of teeth that are only temporary. Then, of course, one question can lead to another. Our baby and adult teeth

made of the same stuff. Why can't we just grow a new tooth if we lose one? And how did ancient people take care of their teeth? Did they have a dentist? Was there such a person? We have questions, and so do our kids, and we want to hear from them too. So let us know what you're curious about when it comes to your teeth. Here to tackle those tooth questions is a tooth scientist. She studies ancient human teeth to understand how humans evolved. Dr. Sharra Bailey is a biological anthropologist, associate professor at New York University. Dr. Bailey, welcome back to Science Friday.

Thanks for having me. I love being here. Oh, it's so nice to have you. Just a note to our listeners, we are recording this in front of a live Zoom audience. And if you want to be part of our next Zoom recording, yeah, join us. You can sign up at our website at sciencefriety.com slash events. All right, Dr. Bailey, let's clear up this first mouth mystery. What's the difference between our teeth and our bones? Are they made of the same stuff?

Well, the white part of your teeth that we see when we smile is made of enamel. An enamel is really, really hard, and about 97% of it is made of minerals. And underneath the tooth enamel, you have something called dentine, which is very much like bone. So it's about 80% or 70% mineral and content. So it's very similar in makeup as bone. But the white part you see, that's different. Just as the inside of your bone is alive and living in your body, the inside of your teeth is alive and living. Yes, yes.

inside our teeth, we have nerves and blood vessels that are very, very much alive as anyone who's had a cavity filled or root canal could certainly attest to. Just thinking about it, though, I'm not trying that to go there. Let's talk about baby teeth now. Why have we evolved as humans to need adult teeth? Why can't our baby teeth just grow with us? That's a good question. Well, we're really constrained by our evolutionary history. So all mammals, in fact, have baby teeth. And since humans are mammals, we kind of just have that evolutionary baggage that we bring along with us.

The reason why we can't have just one set of teeth, our adult teeth, is because, of course, when we're babies, we're teeny, right? So we can't have these big teeth in a teeny tiny mouth. And so you're born and you develop these baby teeth. But as you grow, of course, your jaw gets bigger and you need bigger teeth. And of course, on the opposite end of the spectrum, why can't we keep regrowing our teeth? teeth as we lose them the way sharks do. Yeah, that would be nice. But if you think about it, right, what do we use our teeth for compared to what do sharks

use our teeth for, right? We use our teeth to slice, but also to grind. And if you're going to be grinding things up, you need a bigger surface area. You need a thick enamel so they don't wear down. And because of that, your body invests a lot of energy into making your teeth. And the shark's tooth, the body doesn't invest a lot of energy. in making them. And so, you know, you vest a lot of energy into making these teeth. You're going to make them last as long as possible. Is there another animal that has teeth like ours that can remake them over and over again?

Not like ours, you know, but like sharks, crocodiles, alligators can regrow their teeth not as many times, maybe about 80 times over their lifespan. But all their teeth are just simple cones. They don't have the cool mammal teeth that we have. So, well, let's see. I'm going to revise that. Elephants regrow their teeth about six times, and manatees can regrow their teeth more times than humans. But other than that, other than that, most mammals are just like humans. Or humans, I should say, are like most mammals.

Yeah. Could we humans modify our genes so we could grow a new set of teeth if we lose one? They are working on that. Yes, that's something that scientists are actually working on and trying to. to harness the genes that allow alligators to regrow their teeth and they're experimenting and seeing if they can use it for regrowing teeth, if you get your tooth knocked out, there's something they can do to alter the gene that would allow you to regrow because we retain the dental lamina. So we have the potential. All you need to do is insert a tooth bud

and then just get the chemical process going, this kind of interaction between molecules. That's all you got to do. But easy, easy. All right, we have it. We have someone. Let's go right to Liam from Louisville, Kentucky, has a question about loose teeth. Hi, Liam. Hi, how are you?

Hi, fine, thank you. Go ahead. My question is, why do teeth move around so much before they fall out? Ooh, well, when your adult teeth are growing, they produce this kind of chemical signal that tells your baby teeth roots to basically, go away. So your body actually resorbs or, you know, just kind of breaks down the tooth root. And if you break down the tooth root enough, eventually you have no root left and then your tooth gets all wiggly. Because it's just being held in there by what's called something, it's called the periodontal ligament. A big fancy word for you. But that's all that's holding your tooth in once the tooth root is

gone. And that's why it's so wiggly. Leam, were you like me? Do you like to play with your loose tooth if it's falling out and try to wiggle it a little bit more, then, you know, sort of help it a little? Yeah, I mess around and I always see. Yeah. All right. Thanks for that question. That was great. You study human evolution by examining ancient teeth.

What tales can the teeth tell? Oh, they can tell us so many things. They can tell us about diet in the past, what kind of diets humans were actually eating. We can look at microscopic toothwear. to tell us something about diet. We can look at pathology, like cavities, the rate of cavities over time. And something a lot of people don't know

is that before people started farming about 10,000 years ago, people didn't have to worry about cavities. You didn't have to go to the dentist because their diets were, they're mostly protein or whole grains and they just didn't have the, you know, really sugary kind of diets that we have today.

Can you tell about, speaking of diets, can you tell about how healthy they were from looking at their teeth? Absolutely, yeah. I mean, besides looking at cavities, you can look at gum disease because gum disease affects the bone that holds in your tooth. And so, yeah, you can tell quite a bit about health from the teeth. Well, thousands of years ago, people did not live as long as we are now, right? I mean, life expectancy would be in your 30s or 40s. Yeah.

Would you expect then that people kept their whole set of teeth? up until their death, just in general. A lot of them do, but a lot of them don't, but they lose them not because of cavities. They lose them because of tooth wear. So I've seen some, gosh, I would wish I could share some pictures with you. I have one image I love to show my students of an individual that wore their teeth all the way down. So everything was gone.

Like it was just the roots. So basically they were chewing food on the roots of their teeth. It was amazing. And that's remarkable because in most cases, once you start wearing your teeth down to that amount, you develop abscesses, which basically can kill you outside of mud or medicine. Do you have any idea what they were chewing on to wear it down that much? Oh, gosh. I don't know. What kinds of stuff would it be?

I mean, grains. Well, you could be. This was something that was about 40,000 years old. So they were eating meat, but it's possible that you can, you know, if you dry meat, that can become tougher or you can get grains, you know, dirt and things. And that will call it, that's more abrasive and that can wear your teeth down quickly. Or it was just a very old individual. Speaking of old, what are some of the oldest teeth that have ever been found? Yes.

I've looked at those. They're about, well, okay, not all of them. The oldest human teeth would be about six or seven million years old. I have not seen those personally, but I have seen the ones from the species art epithesis, which are 4.4 million years old. And that was cool to say. I'll bet. I mean, do you also find old baby teeth? We do, sure. Yeah, you don't find them as often. And you can imagine that when the, of course, when your baby teeth fall out, the root is gone, right? So all you're left with are these little

teeny tiny tooth crowns. And they're, you know, they're hard to recover from an archaeological site. They may be there, but people might not recognize them. And also, they tend to get worn down too. So when we do recover baby teeth, a lot of times, they're very, very worn. And the oldest baby teeth that you have found? Oh, that would be in the millions. It would be 3.4, I think, the oldest ones I've seen. I can't remember if the art epithicth has any baby teeth.

All right. Let's go to Dax from Phoenix. has a question about dinosaur teeth. Yeah, I want to know that. Dax, go ahead. What? Ask my question. I'm going to have to look at it again.

I can't remember it. Take your time. What did dinosaurs do to take care of their teeth? Ooh. Ooh. Dinosaurs probably had teeth that would be like alligators. They would replace their teeth if their teeth fell out. So they probably didn't really have to take care.

care of them. They were lucky. They just ate what they wanted to eat when their tooth fell out, grew back in, no problem. I imagine you find baby dinosaur teeth also somewhere along the line. Somebody would. I haven't. Somebody would. Yeah. Well, let's talk about the baby teeth a little bit more. When you study them, do they have the same forensic markers that adult teeth have? Yeah, they do. The front teeth, the incisor teeth are not quite as, they're much simpler. They're small. smaller, of course, but they're also simpler. But the molars, the baby molars do have the same kinds of, you know, the characters that we recognize as being markers of certain geographic areas. Well, when you come across some really old teeth, how do you tell whether it's from an ancient

human or some pre-human? Is it easy or very difficult to tell? Well, there are some very diagnostic characteristics. So, for example, if I saw a baby tooth from a Neanderthal, I would be able to tell you it's from a Neanderthal. I mean, to you, probably if I showed them to you, you'd say they look like just like ours, but to a trained eye, you can see big differences. And the same for, yeah, for earlier ones like Austrogyllicines, they'd have definitely some certain characteristics that would tell me that that's an ancient human, absolutely. This is Science Friday from WNYC. Studio talking with Dr. Sharra Bailey, Professor of Anthropology at New York University,

and we don't have to pull teeth with her. I had to get a dad joke in some place, Dr. Bailey. Excuse me. I looked at a skeletal picture of a baby's head when I was researching this. And, you know, it was kind of shocking to see that the adult teeth are right behind the baby ones when, you know, in a child waiting to descend.

A freaky. It is very freaky. You know, it's not obvious when you look at it. a kid that there's teeth and two sets of teeth in their mouth and that they have a second teeth right, the second set right behind that. Yeah, absolutely. You know, there was a, there was this chart when I was a kid in my dentist's office, he had a chart. It's a very classic Cheryl and Masler chart from the 1950s that actually showed that. And I remember being fascinated, but maybe that was, you know, I should have paid attention to that. I knew I'd be interested in teeth.

But I remember staring at that chart and being like, oh, I am seven and that means these teeth are forming. in. Yeah. Do other primates, you know, chimpanzees, other kinds of primates have that same two set of teeth system as we do? Absolutely. Not only that, but, you know, the number of teeth that we have, you know, two incisors, one canine, two premolars, three molars on each side, that's actually something we share with apes and old world monkeys. So our dental pattern is actually quite conserved. And then we have certain characters on our lower molars that are also seen in other apes. So we share a lot of things with chimpanzees. Yeah. And I know a number of children who,

when they lost their baby teeth, did not have the same number of teeth coming back. They were sort of missing some of their adult teeth. And the orthodontists had to move the teeth around a bit. Yeah. Yeah. There are certain hotspot areas in our dentition where if you're going to have, have teeth that don't form. So right next to your main teeth here, these incisors, these incisors, your wisdom teeth, and your second bicuspids are the ones that if they're not going to form, that's where it's going to happen. Here's a question from JV. and Rockville, Maryland. Are teeth specific to individuals, do you ever find identical teeth? I guess they're asking like fingerprints. Yeah, that's a really good question. Now, of course, if you have identical twins, their teeth are

going to look a lot alike. But even in identical twins, the teeth might be a little bit different. And that's because it's not just our genes that determine what our teeth look like, but also our environment and the kinds of things that are going on around us or in our environment while our teeth are developing. So they could, for example, one twin might have smaller teeth than the other twin. But besides twins, teeth are pretty unique to each person. Do you have any idea why some of our molars are called wisdom teeth? Yes. Yeah. Why is that? Because when they erupt, we're supposed to be wise by then. And the first permanent tooth that comes in is called your school tooth, because when that comes in, you're of age to go to school. And do you want to guess what the second molar is called? So you have your school tooth, your wisdom tooth. What do you think is in between?

Your college tooth, your adult tooth. You're an adolescent tooth. I don't know. I give up. It's called your factory tooth. Because when that comes in, you're old enough to work in a factory. Oh, goodness. That's going back to the 1800s when these teeth were named. Are we calling it Silicon Valley tooth now? Or something like that, yeah. And do they have a certain purpose or are they just just filling up the rest of your mouth as they should be? Because so many people have their wisdom teeth pulled out. Yeah. I mean, we don't really need the wisdom teeth so much.

We don't. Not so much. I mean, people, the thing is that, you know, think about our diets, right? They're so soft now. And in fact, that's one of the problems. That's why people have dental problems is because our jaws don't develop like they should because we eat these really soft diets as we're growing up. And so our jars are small, which doesn't give us enough space to erupt our teeth, which is why sometimes our teeth are impacted, which can be very dangerous.

But there's really no, there's really, if you don't have your wisdom teeth, you, you survived adulthood, you have babies, there's nothing, you know, nature is not selecting against you. One last question about the ancient teeth, because it fascinates me, if ancient people had good diets, Do their teeth look in better shape than the kind of crummy diets we have now? Yes. Yes, they do. No kidding. Besides being, you know, they wore down faster because their diets were tougher.

But, yeah, I don't see cavities. You don't really see periodontal disease that much. No, their teeth are in good shape. So we don't know if they had dentists that they went to either. They wouldn't have made a living. That's a good place to wrap up. Thank you very much for taking time to be with us. You're welcome. Thanks for having me.

Dr. Shara Bailey, Associate Professor in the Department of Anthropology at New York University, and thanks to everybody out there in Zoom World for taking time to be with us today. We're going to take a break, and when we come back, we'll revisit one of our favorite charismatic creatures, the thylacine. Is it still extinct? Just what is it? We'll find out after this break. This is Science Friday. I'm Ira Flato.

Last week, conservation biologists on Twitter were all a flutter at rumors circulating that a creature called a thylacine, better known as a Tasmanian tiger, had been caught on camera in the Tasmanian bush. Thylacines have been considered extinct since the mid-80s, but there are those who believe or hope they still exist. In a video posted to YouTube, Neil Waters, president of the Thylacine Awareness Group of Australia, shared the news of what he thought to be images of two adult thylacines and a baby. Baby has stripes, a stiff tail, the hawk, the coarse hair, it's the right color, it's a quadruped, stocky, and it's got the right-shaped ears. So it puts our thylacine in a much stronger position than it's been in for the last 30-something years now.

While the animal caught on camera was ultimately identified as a patty melon, we never turned down an opportunity to celebrate a creature as charismatic as the Tasmanian tiger. So today, we revisit our conversation from January 2020 with Neil Waters and Dr. Gregory Burns, along with Science Friday's charismatic creature correspondent Ella Fetter. Joining us again in our charismatic creature corner is our correspondent, Science Friday's own Ella Fetter. Hi, Ella. Hi, Ira. Yes, I am back once again to plead the case that one very special creature is worthy of the coveted charismatic creature title.

And by creature, again, I mean almost anything. We count tapeworms. We count bacteria. And by charismatic, I mean a creature that is as worthy of our curiosity and enchantment as a baby panda. Well, that's a pretty high bar, you've said there. If you like baby pandas, which of course we do. So last month I made the case that slime molds are charismatic because I wanted a bit of a challenge.

I might have been in over my head. I did get some people on board. Some people were on the slime train, and they left some very nice messages on our vox pop app. But we also got this. This is Kate from Modesto, California. I'm pretty sure slime molds will never be charismatic in my opinion. Mm-hmm.

Mm-hmm. Yeah. Mm-hmm. have something now better then for Kate? Well, funny, you should ask, Kate had something better for Kate. Kate left us another message with this suggestion. I've always been really interested in Tasmanian tigers. Many people say that they're extinct, but some people report sightings.

Do you have any information on them? Okay, so since Kate is my toughest critic, I decided to give this a shot. First of all, these are not Tasmanian devils, which is what I thought Kate was referring to at first. Tasmanian devils are endangered carnivores that live on the island of Tasmania. We're talking about Tasmanian tigers. Have you heard of these before? Who hasn't? Well, you're very learned.

I had never heard of these before, but now I'm in deep. Okay, so like Kate said, they're considered officially to be extinct. But people have been reporting sightings, like hundreds of sightings, not just in the island of Tasmania, but in mainland, Australia too. Okay, for those of us who have confused Tasmanian devils with Tasmanian tigers, fill us in in what a Tasmanian tiger is. Okay, so the Tasmanian tiger, also known as a thylacine, it actually looks a lot like a dog, but with, like tiger stripes kind of on its back, except that it's not a dog. It's not a tiger. It's actually a marsupial, like koalas and kangaroos. It actually has a pouch and everything.

I noticed we have a photo up on our website at Science. Science Friday.com slash cute. Yeah, not to bias you or anything. So here's the deal. The last known Tasmanian tiger died in a zoo in 1936, actually as a result of human neglect, it sounds like. 50 years later, the species was declared extinct, but people keep claiming to see them. And earlier this week, I caught up with one of those people, Neil Waters. He told me about a time 10 years ago when he was walking in Tasmania just before dark.

and I'm walking up this road, this dirt road through the bush, and I can hear this crunching of branches under feet somewhere in the bush alongside me. I can't see it because the bush is so thick, but I can hear it. Every time I stop, it stops. So something's following me. Creepy, right? Oh, yeah.

So eventually the creature runs off, but before it does, Neil does catch a glimpse. And apparently it looks kind of like a dog, but not a dog. It's dark, so he is as important. He does not see the telltale. tiger stripes. And he's not 100 percent. He's not totally sure what he's seen. But then he starts talking to people and he learns about all of these other sightings. And then he himself sees one again in 2014. So he's a geek like me. And you see something, you want to go out and prove that

they're really there. Exactly. So Neil is dedicating, he's actually dedicating the next two years of his life to living in the bush and finding definitive proof that these animals are still out there. He walks around with night vision goggles. He goes looking for their scat. He's even set up a bunch of motion sensitive cameras. And a lot of other people are going to help him sift through those photos like a big citizen science project. Eventually, someone will probably get the irrefutable proof. And when that happens, we want, you know, scientists to get on board as much as possible. And so that's why I keep annoying them and saying, hey, look, someone's sort again. Are they annoyed?

Oh, look, I've annoyed quite a few academics over the years, but I've got the respect of a few, too, so that's okay. It's 50-50 at the moment. So today we've actually brought on another academic to annoy, or to tell us more about the Tasmanian Tigers, and how you do research on an animal that is nowhere to be found. His name is Gregory Burns. It's a professor of psychology at Emory University. Welcome to the show. Yeah, welcome, Gregory. Hi, Ira. Hi, hi, Ella. Hey. So, Greg, first, Tasmanian tigers, they look like dogs but are not dogs. What is up with that? Yeah, so these creatures are fascinating. And as you said, the tigers are actually marsupials. And the only reason that we call them tigers is because they have stripes on their back. And when the original settlers of Tasmania saw them, and those would be the British colonialists, they saw them. And they saw the stripes. They said, oh, these. These must be some kind of tiger, and that's how they got their name.

But they are not at all related to dogs. And I got interested in it because of my interest in dogs and how dog brains works. And I was interested to find out, well, what can we figure out about these animals? They look like dogs or coyotes, but they're not. And so we started studying and looking for their brains. So this is a case of convergent evolution, right? How do you get two animals that are not remotely related looking so much alike? Yeah, and to really appreciate this, you know, what this animal is or was, you have to go way back in history.

We're talking 200 million years at least. And to kind of give you an idea, this is the age of the dinosaurs, you know, mammals didn't even exist back then. And actually the first mammals actually laid eggs. And the marsupials later descended from these creatures. And to give you an idea of how long ago this was, this is when all the continents were jammed together. There's just one big landmass, Gondwana, Pangaea. And as mammals evolved, during this period of time,

the continents started to separate. And what ended up happening was that these marsupials, these descendants from the very first mammals who actually laid eggs, they started to give birth live. Not, I mean, but just barely, right? The marsupials give birth life, but they're tiny, tiny little creatures and they crawl into the pouch. And so these animals start evolving, and as the continents split up, the marsupials were kind of left to their own in what became Australia. And they had no competition from other animals, which we call the placental mammals.

That's us. That's us. And that's pretty much all the mammals in the rest of the world. And so you had this kind of line of mammals evolving pretty much on their own in Australia. And you mentioned convergent evolution. And so the Tasmanian tiger or the thylacine actually ended up being what we call the apex predator in Australia. And so what did they prey on? Well, they preyed on the other animals, which would include things like kangaroos and wallabies and other little animals.

And so we think what happened was that they evolved to kind of look like an animal that preys on other small animals. And so we know those types of animals as things like coyotes and wolves and dogs. But in Australia, they were Tasmanian tigers, except they were marsupials. Right. Wait, if you say they're marsupials, did they have a pouch like a kangaroo did? They did. They had a rear-facing pouch. So not the pouch that everyone knows kangaroos have.

they had a rear-facing one, meaning the, you know, the young kind of looked out backwards. So zooming forward to the present, you know, they used to be apex predators, but by all, well, not by all accounts, by many accounts, they are now gone. What happened to these animals? Yeah, so what happened, I mean, we don't know exactly, but we can kind of piece together this story. It's kind of like a crime scene, so we're trying to do this forensically. So we know that thylacines existed on the mainland of Australia at least until probably about 4,000 or 5,000 years ago because there have been remains found that have been carbon dated to about 4,000 years ago.

And what's interesting is that period of time, there were also people in Australia by then, the aboriginals. So humans started occupying Australia probably 20, 30,000 years ago. And we know that the aboriginals were aware of the thylacines because you can find cave art showing them. And so there was this very deep relationship to them. That's interesting. Wow, keep going. Yeah.

And so the other thing that was going on in this period of time is this was also the period of the last ice age, which means that the oceans were lower. And so Australia, the mainland, was actually connected to Tasmania. Now, Tasmania is an island. and it's south of Australia, kind of between Australia and Antarctica. So it's really far south. But they were actually connected by a land bridge. So the thylacines, as well as the people, were able to move freely. And then as the ice age ended, the glaciers melted, the seas rose, and Tasmania was cut off from the mainland.

So you had this population of thylacines on the mainland, and then you had a population that was cut off in Tasmania. Now, for reasons, we're not totally sure, the mainland thylacine seemed to have disappeared. We don't know if it's because of conflict with the humans. Maybe they were hunted. Maybe their dogs competed with them. Or maybe it was just simply climate change, because before that, mainland Australia was much wetter and more temperate than it is now. So you ended up with just a small population of these creatures on the island of Tasmania. And then the British colonialists arrived.

And that was the end of the story, pretty much. What happened when the colonial? I mean, just to spell it out. What did the colonialists do? Well, the colonials wanted to turn Tasmania pretty much into farming land. And so they brought their sheep with them. And mysteriously, their sheep started disappearing and they were killed. And they all thought that this thylacine was the one doing it.

And so there was a bounty put out on the thylacines along actually with wild dogs. too. And so everyone just started killing off the thylacines because they were predating on the sheep. Although it actually remains debatable how much the thylacians were responsible for that. Really? So they might have been falsely implicated. I believe so. Wow. You know, last time we talked, Greg, I know you're a neuroscientist and last time we talked, you told me you've been studying dogs a lot and you actually trained a dog to sit still inside an MRI machine so that you could study its brain. How do you go about finding and studying a dead Tasmanian tiger's brain?

Ha, ha, they're as rare as hands teeth. So there's kind of a, I don't want to say a secret order of the thylene, but there is a very active international community of people interested in all things thylacine. And so one person that got to named Steven Sleitholm has compiled a database of all the known thylacine specimens in the world. And so I wrote to him and I asked him, I said, do you know, are there any brains left anywhere? Now, as you said, I'm interested in brains. And so what I wanted to know is, you know, even though a thylacine kind of looks like a dog, I wondered what their brains look like.

And it turns out that there are four known brains left intact in the world. And as luck would have it, the Smithsonian has one of them. So I borrowed it. That's cool. I'm Ira Flato. This is Science Friday from WNYC Studios, talking with Ella Fetter about the Tasmanian tiger. And Professor Gregory Burns. Yeah.

So what did you figure out when you took a look at these brains or this brain? Well, we actually know everything about this brain in the sense that we know the animal that it came from. It was completely documented. It came from a tiger that was captured in a town called Lonston in Tasmania in 1902. They brought this tiger over across the Pacific Ocean and then by rail all the way to the National Zoo in Washington. And then when they got this tiger there, they realized they didn't have just one tiger. They actually had four because there were three in her pouch. She was a mother.

And unfortunately, she died and two of the pups survived and they lived at the National Zoo until they died. And so we know everything about them. And when I got this brain, it was actually quite shrunken, kind of the size of a walnut. And we knew from the records that it didn't start out that way. It had actually shrunk to a third of the original size. But we were somehow able to coax enough signal out of it when we put it in the MRI that we could reconstruct many of the pathways that, exist in the thylacine's brain. And so I actually were almost out of time, so I should ask the question that everyone has been

wondering about, what do you think? Are they still around? As much as anyone, I would love for them to be around. And, you know, I went to Tasmania, you know, to look for them myself. And obviously, I didn't find any. Personally, I don't think they're there. I would like to keep hope for them. But actually, you know, I've thought of it.

about this a lot. And I think kind of keeping the hope alive actually does a disservice to the other animals that are disappearing as we speak. There you go. Okay. Wait, before we go, Ira, so I need your verdict on a scale of one to ten baby pandas. How charismatic are the Tasmania? And please, before you answer, bear in mind all that they've been through. Okay. You know, how do you, how can you not feel that an animal created by committee, it has a pouch like a kangaroo or looks like a dog and has stripes of a tiger. How could that not be cute? So it's really, I think it's really cute. Good animal. It wins. I need a rating. I'll give it an eight and a half. Eight and a half, Greg.

Eleven. This is off the charts. This is like, it blows away the baby panda. This is polar bear territory. Okay. Well, thank you very much, Greg and maybe Ira. And thank you also to Neil Waters, who spoke with me earlier this week. Thanks, Ella. And thanks to Dr. Gregory Burns, Professor of Psychology at Emory University, who we spoke with last January, and Neil Waters, who continues his search for the Tasmanian Tiger as president of the Thalocene Awareness Group of Australia. We wish him look. That's about all the time we have. Charles Berkwist is our director. Our producers are Christy Taylor, Katie Feather, and Kathleen Davis, senior producer Alexa Lim, contributing producer John Dan Koski, B.J. Leiderman composed our theme music. And of course, if you missed any part of the program,

or you'd like to hear it again. Subscribe to our podcasts or ask your smart speaker to play Science Friday. Have a great weekend. We'll see you next week. I'm Ira Flato.