Kleptotherms

Hey, this is Radiolab. I'm Latif Nasser. So at this point of the year, at least here in the Northern Hemisphere, it can start to feel like enough with the cold already. The newness of the season has worn off, the winter holidays are over, and most of us are just ready for it to be warm again. So today we are defrosting an episode about people and creatures seeking warmth. Sometimes they do it in obvious ways. Sometimes they do it in devious ways. We first aired this episode back in 2021, and you'll hear there are certain things about it that do feel very 2021. But there's also so much in here that feels timeless. Stories that I feel confident will stay relevant until the thermal death of the universe. Wait, you're listening. Okay. All right. Okay. All right. You're listening to Radiolab. Radiolab. From WNYC. Rewind. Lou. Hey, how are you feeling? I mean, I feel fine. And I think I still am like a dashed nasally. Hi there. It's Radiolab. I'm Lulu Miller here with senior correspondent Molly Webster. So can you humor me and close your eyes? Yes. Eyes closed in my closet. Okay. So now journey with me. Me and you are on a trip. We've got our backpacks and our hiking boots. Okay. And we've, we come across this site, an archeological dig, and they are, they're like unearthing this ancient library. And we're like looking all around and you're over there and I don't know, you find like a old globe. And then we come across this book that's like covered in dust and we blow the dust off. And the dust, like it turns into like snowy, frosty snowflakes and little tiny flames. It's like, and then it says in silver letters, kleptotherms. And then we were like, Ooh, what's what? And we cracked the book and it's like, and we open it and there's five chapters and we turn the page in the first chapter. There's just a picture of a snake in a coil. So we're going to start and read that chapter. Okay. So once upon a time, there was a bright blue snake in New Caledonia. It's bright blue and black, so it's just like striped. Is this real? This is real. Oh, this is one. Okay, this is real. Oh, it turns out this whole book is stored in the Library of Congress as non-fiction. Okay. So it's this blue and black snake. It looks kind of like beetle juice. And it is a horrible thing. It's an amphibious sea snake. So it can live in the ocean and on land. And scientists have observed that it does this thing. They sneak into burrows, which are occupied by large tropical seabirds. This is Hans Isermann, a social scientist at the Université Grenoble Alps, who explained that the snake will slither deeper and deeper into the burrow toward the bird sneaking up and then it just kind of hugs it and they take advantage of the mass body heat in warming their own bodies and are they not even eating those birds they're just kind of like curling around them and sucking up their heat that's essentially what they're doing yes wow There's just something so primal about the heat being more important even than the meat. Yeah. So this behavior is called kleptothermy. Kleptothermy. And what does that mean? Basically engaging in heat theft. Okay. You see it all throughout the animal kingdom. Really? Yeah. Seriously? Yeah. So like male garter snakes? They pretend to be female so that other males will try to mate with them. Like the friction of them trying to mate just warms them up? Yes. There's little dwarf caimans, which are kind of crocodile-y looking things that steal from termite nests. How do you cuddle up to a termite? I don't know. I think you just like throw yourself upon the whole warm nestiness of all that bug heat. Wow. And us humans also engage in clepsothermia when we want to. That oh so sweet act of cuddling, or as the scientists call it, huddling, is, for at least one person involved, a theft. I remember reading about it a couple of years ago, and I thought it was just fascinating. But if you think about it, it feeds into the same kind of equation. An equation biologists call the economy of action. It's very simple. Animals need to take in more energy than they exert. And one of the most expensive things that we do, particularly as mammals, is warming our bodies. And it turns out that of all the ways to keep our body warm, Jumping up and down, finding a sunspot, eating something really fatty, getting our warmth from another creature is super efficient. It can decrease the cost of thermal regulation by up to about 60 or 70 percent. Wow. There are a lot of observational studies on this for many, many different animals. Rats, penguins, daigus. Not only is their peripheral temperature higher, but also their base metabolic rate is much lower, meaning that they exert much less energy. To stay warm. Huh. And so Hans' idea is that because for so long, humans relied on getting warmth from one another to survive. Even 200 years ago, people would sleep with nine people in one bed to keep warm. Our sense of how chilly or warm we feel isn't just about air particles. It is being influenced by the people around us. Way more than we typically think. I think it's for most people, it's hard to imagine until you see it and then you can't unsee it. Which brings us to... Chapter... Two. What's the picture? I'm wearing sweatpants, a long sleeve shirt. It's a guy in a jacket. It's probably one of my nicer shirts. I wanted to look nice even though it's only the radio. His name is John and he's going to lead us to a different idea about how to get warm. Okay. Okay. Can you tell me a little bit about where you grew up? I grew up in the woods, in a house in the woods in Connecticut. Do you remember how the world felt to you as a kid? Like thinking back, me and my sister would make paths through the woods. There was a pond nearby and we would go frogging. And I just remember playing with the hose, getting water all over us. and feeling free. But as he started to get a little bit older... When I was 13 or 14, things really started to change. I gained a lot of weight, and everyone was making fun of me. And I became very uncomfortable in my skin. Which, you know, happens to a lot of middle schoolers, but for John, it hit him harder. I was scared of looking at my own reflection. I almost thought I was seeing a ghost. I would keep the lights off and keep a distance from the mirror. I didn't look at the mirror for like two or three years. And then once he hit college? I started hearing voices. And what were some of the kinds of things they might sort of be saying to you? Do this and do that. I got to walk in a certain fashion and they told me that I didn't deserve to eat. It was madness. And then I saw a doctor. Like, did you get a diagnosis then? Yeah. Schizoaffective. Which is not exactly schizophrenia, but has some of its symptoms. He prescribed me a drug, an antidepressant, and I had a really bad reaction to it. What happened? It really brought on those internal voices. Like I remember driving in the car, thinking everyone on the road was targeting me. So? I went off my meds. But this sense that people were out to get him just kept getting worse. I just remember everyone giving me a hard time. How did they give you a hard time? They would give me dirty looks. They would pull schemes on me and mock me at times, maybe even. I remember my mom saying once, people aren't out to get you. And if you take your meds, then you'll realize that. So like, how sure are you that you were actually being mocked and actually being given dirty looks? And how much do you think that could have been something inside you seeing it that way? It could have been something inside me somewhat, but it's hard for me to believe that it was all me making it up. So he keeps just trying to muddle through. And at a certain point, John does something seemingly trivial. It's a nice warm day out, shorts and t-shirt kind of weather. And he puts on a winter hat. I got for Christmas one year. What color? It was gray. It's a comfort. And before he heads out the door, he rifles through his stuff and decides to also put on... A hooded sweatshirt, hood up. And then he grabs a third layer. It was a jacket. And a fourth. Sweatpants. Until eventually he's all bundled up from head to toe. And he started going out in the muggy heat of a Connecticut summer wearing this little getup all the time. And people would say things like, What are you preparing for a wrestling match? like trying to lose weight for a wrestling match Right like training in trash bags kind of thing Yeah And John is the first person to say like as he was putting on all these layers he was falling into this trope Like, if you saw someone walking around in a ton of layers in the heat of summer, you're probably going to think something's up. Maybe keep a wide berth. I mean, when people see you wearing layers, what do you think they think about you? I think they're fearful. They fear me. Hello? Hello? Hello. And the thing is, while most people might step away when they see someone wearing layers, there were a few people all over the globe who decided to look closer. Am I audible? There you are. Sorry about that. This is Dr. Tathagata Mahintamani, a psychiatrist in India. Currently, I am in northwestern part of India. Who back when he was starting out as a psychiatrist in Raji, started noticing that in the middle of summer, every now and then people with schizophrenia would walk into the hospital wearing tons of layers. Ladies were wearing multiple layers of saris and male patients were wearing multiple layers of shirts. And over in Melbourne, Australia. I was doing my first psychiatry rotation. Dr. Terrence Chong was treating a patient with schizophrenia. I noticed at the time he was taking off layers and layers and layers of clothing. And this was in the heat of summer. There was a doctor in Memphis, Tennessee who noticed the same thing. Wow. Yeah. And eventually it even got a fancy medical name. Redundant clothing. So the idea there is just it's redundant. You don't need it. It's multiple. It's redundant. Redundant clothing. Yes. So a bunch of doctors were seeing this, but nobody really knew why. And some of the explanations were like, look, people with schizophrenia, some of them end up not having homes. They're living on the street. You have to keep your belongings on your back. So like you have you wear them all. Another thing might be evolution. A lack of motivation. So basically the person maybe forgot to take the last layer off. Yes, yes. Another explanation is just this generalized erratic, I'm confused, so I have on all these clothes. I mean, there were all kinds of different explanations. Can you just describe why you crave the layers? I think it's a way of shielding myself from the world. Like, I feel the world is harsh. It's hard. It's hard for me to completely put a finger on it because I was just doing what felt natural. And Dr. Maheen Tamani, after seeing enough people walk through his door wearing layers in the heat, seemingly comfortable, wanted to figure out if something else was going on. So he got a group of people with schizophrenia, some of whom wore layers and some of whom didn't. And he just ran all these tests. He did like cognitive tests and psych tests and physiological tests and basically long, long, long, long, long story short. What he found was that the people in layers had something different going on with their blood. First of all, their blood pressure was dropping way lower on certain tests. And when he analyzed blood samples, he found that their T3 and T4 levels were lower. And what does that really mean? Like, what does that mean? So free T3 and free T4s are very reliable markers of temperature regulation. Temperature regulation? Yes, with cold intolerance. Like you just get cold quicker? Yes. Okay. You feel cold quicker. Wait, so they're actually, they may have layers on because they are actually physically colder. I asked him almost exactly that. Is your idea that they are actually wearing the layers to feel warmer? It is our findings. And our ideas are based on our findings. He says the evidence suggests that like they are wearing layers for the same reason you or I wear layers when we go out into the winter. Like their body is telling them they feel colder. Now, back in Connecticut, John didn't know any of this. He just knew that the more he tried to stay warm by bundling, the more it pushed people away. It was a really difficult time for me. And things finally got so bad that he goes back to the doctor. and this time is in fact diagnosed with paranoid schizophrenia. And he's prescribed a different medication. I immediately noticed less up and down, less craziness. I noticed myself getting better by the day. And the world seemed to be getting a little better too, a little gentler. And I felt people liked me. And he started loosening up, literally taking off his hat, his jacket, or one of them. It was winter and I would wear like a tank top under a winter jacket and that was it. And he started to embrace his diagnosis. I read about how people with schizophrenic disorders oftentimes think divergently and a link to creativity. And he would tell people about it. Like one time he went to go buy cigarettes and the guy behind the counter thought he looked a little young. And I said something like schizophrenic people tend to look young, which I don't know if it's even true. But I was very proud. I wasn't very proud, but I was like I had some pride. And then one day, about 30 miles away from where he lives A young man walked into Sandy Hook Elementary School and we all know what happened And the day it happened, one of John's online friends sent him an instant message saying Like when they first heard about the news that there was a shooting in Connecticut they thought of me For an instant, they worried the shooter had been John. It was really hurtful. It was like I would never do anything like that. I definitely stopped having that pride towards my diagnosis. He stopped taking his medication. I felt a lot more gloom and doom, and I started to slip real quickly. Into this chilly spiral, where without his meds, the world started to seem colder, which Dr. Maheen Tamani explained can be this unfortunate part of the disease that the longer you go it alone, it can have what's called a neurotoxic effect. Our neurotoxic effect on the brain, loss of brain function, and also there is structural brain damage also there. As the time progresses, the patients with schizophrenia often, you know, drifts. So as John was drifting, the world started seeming even colder. Thinking everyone was targeting me. So he'd layer up, which itself would make the world oftentimes be colder. There was a woman walking and she just gave me the dirtiest look I've ever seen in my life. And I said to her, what is it, the winter clothes that I'm wearing that makes you dislike me? And she immediately called the police. And then it's like one more layer. Another layer. Wow. At the end of our study, we also thought that this might be a window. You know, this kind of redundant clothing might be a window through which we can peep towards something really, really broken down. Dr. Maheen Tamani found that the thing that the people who were wearing layers all had in common was that compared to the controls, they were the ones who had been going it alone. without treatment for longer. That's really wild that you could just look out and like see that from the outside. Yeah. Which made me start to wonder, is it almost like humans have within them like this visual signal for like, I'm really lost. I might not even know how to ask for help, but here is a signal. That's pretty. I mean, I put the idea to Dr. Raheem Tavani and he was like, I am not in a position to answer this, but this is a wonderful and intriguing question. Yeah, but I also put it to John. Is there anything to that or am I like overly projecting an idea? No, I think you're you could be on to something. I think there could be like a cry for help through layers. And he told me a story about one time when someone seemed to read it that way. I think she was wearing a t-shirt and short jean, jorts. Jorts, the old lady jorts. Yeah. I said, hey, how are you? I was probably not talking that clearly and making much sense either. And she asked me if I would sit down and have lunch with her. I took a bite or two from my grilled cheese sandwich. I almost felt I didn't deserve that food. and I said to her, I think I'm going to feed the rest of the birds. And she said to me, don't feed the birds, just eat your food. Then I ultimately fed the birds. She went aw, like feeling empathy towards me. Yeah. Did you feel a little bit better after that? Yeah, I did feel better. He eventually felt so relaxed. He slipped off his sandals and he put his feet on the sand and he just walked home barefoot. Yeah. Okay so turning the page Chapter 3 Picture two people playing a game sort of like catch The cyberball experiment Okay. So Hans, our researcher from earlier, told me about this study he did where he had people playing this game called cyberball. And the way it works is that you enter the game and two other computer players invite you to start tossing a ball around with them. Foop, foop, foop, foop. Okay. And then at a certain point, they just suddenly start rejecting you. You're not part of this ballgame anymore. They just suddenly start excluding you and won't throw you, pass you the ball. And in... That's terrible. Yeah. And so like in that, people rate the room temperature as colder. But then what he did was he snuck onto their fingers a little digital thermometer. With Velcro on it was just a bunch of sensors with a wire sticking out of it. And he found that their peripheral skin temperature, their skin temperature dropped in that condition when they were excluded. Yeah. And so it's like you perceive it as colder and your skin actually gets a little colder. Oh, wow. I mean, to see it reflected on the skin felt like such a leap from emotion or feeling or thought to physical reality. What was it like for you to find that result? I think in the beginning it was stunning to find it. I mean, I think that's also why we repeated the experiment. But it also opened up the door for kind of trying to figure out what else was there. What else was there after the break? On 1440 Explorers, we talk to the world's experts to unpack the fascinating knowledge behind everyday topics that shape our world. It's really easy to influence dream content. We can turn you into a drunk. The credit card has massive negative social consequences, and also, it's magic. The ancient Greeks' idea of what a ghost was is very different to the modern Western idea of what a ghost is. Listen to 1440 Explorers wherever you get your podcasts. This is Lulu, Radio Lab, back here with senior correspondent Molly Webster. Should we go back to the book? Yeah. Nice. Chapter four here, right? Chapter four. Picture's pretty groovy. It's like a thermometer and it's broken and mercury is spilling out of it like blood. And I want to take chapter four. Hell yeah. You're welcome. Thank you for letting us in. Because I've been thinking about this a lot lately. Like for all of us right now, our core body temperatures, that basic temperature that our body is working at, has become a literal passport back into society. It's kind of a rainy day, so it might be a little bit light. So I went to a bar in Brooklyn, where like any other bar in the city right now, there are people at the front of the bar with the gun. Temperature gun. The temperature gun. Zapping everybody who shows up. Bonnie and Scott have got it under control. Deciding if people can come in and out of the door. Oh, like the new bouncer of temperature. Exactly. We got a 96.1. And this is happening. Before I go to work every morning. Basically everywhere. I have to take my temperature and text it to the school nurse. So here we go. We actually put a call out to our listeners had people send us little recordings. Walking up to get my temperature tested. As they headed to work. Arriving at Mask Sound in East Rutherford, New Jersey. Or to the grocery store. I'm at my supermarket. I'm about to go take the temperature. Dropping their kids off at school. Okay, Joey, let's take your temperature so you can go into school. Stop if your temp reads above 99.4. This is how we decide now whether or not it's okay to be around other people. Normal temperature. You are free to pass. Thank you. Good to go. See you, buddy. Now, we did not get anybody who is in the sort of uh-oh range, but what you do hear in the tape... 97.5. ...and what I saw in the bar... 95.5. 96. 96.3. ...is a pretty surprising range of numbers. 97.5. 97.2 degrees. 96.4. 98.5. 95.2. That's not right. 94.6. Little chilly, but low is better than high. I mean, there were temperatures from maybe 92 all the way up to 98. That's six whole degrees. Okay, so what are these guns? They don't work. Yeah. What is that? I mean, there was just a study out that says the temperature guns read like two to three degrees cooler than you actually are. Which is troubling in its own right. But the thing that really hit me is that the spread of supposedly healthy people sort of flies in the face of that bedrock of human health. That golden number, 98.6. Yes, the golden number of like what a human body should be. Except it's kind of a con. A con? Sort of. Let me just explain first where it comes from. Okay. So the story of 98.6 starts in the 1800s, as all good science stories do. Yep. So in the late 19th century, you get the introduction of thermometers into medical practice. So for this section, I'm going to get a little help from Deanna Day. I'm a writer and historian. Sorry, I got some great. Great. I always have this moment because I am doing like 50,000 things. She is the master of many things. But anyway, Deanna told me there's a couple of things to know about the 1800s for the purposes of our story. One is that fevers back then weren't seen as some sort of signal or sign of a disease. The fever was just the disease. They thought fevers were the actual illness. The thing you had that was causing all of your symptoms. Like you catch a heat and then it like gives you all this bad vomity tiredness. But then along came a guy named Karl Wunderlich. Cool name. So Wunderlich was a physician in Germany. He was the chair of medicine at the University of Lipsig. And he was one of the first people, one of the first doctors to use thermometers in his clinic. At the time, they were like two feet long and took 20 minutes to take a temperature. And in the 1850s, when Wunderlich was doing his thing, it was like an era when big data was becoming king, which is funny because you wouldn't actually think about that because there were no computers. Lots of pencils. Yeah, lots of pencils, lots of paper. And so his thing that he was like, OK, the data that I'm going to collect is I want to understand how temperature of a human body changes throughout the progression of an illness. And so at his hospital, they took temperature readings repeatedly over and over from about 25,000 patients. 25,000 patients, a million and a half temperature recordings. Did he have a fleet of temperature collectors? No, it was basically him and whoever worked in his clinic. He just had a really busy clinic in Germany. Wow. That's like, that feels, but I guess over like decades, right? Yeah, like 20 years. So Wunderlich collects all this data and... Did the 19th century version of crunching the numbers and created all of these charts. Fever charts. He found different diseases had different fever progressions in patients. He would have like a patient that had syphilis, say, and he could map their temperature change throughout syphilis and he would get like a really pretty pattern on an XY graph. Some diseases would have a fever that would spike and drop and spike and drop. And other diseases had a fever course that would kind of like ramp up gradually or ramp down slowly. Really? Cool. I've never thought of that. Like that each illness has a little curly Q signature that you're like, oh, that's cool. If I'm honest, like, I don't know if that actually still holds up today. Yeah. But his idea was that you could track someone's temperature and diagnose them that way. And that was a big change. All of a sudden, we start seeing fever not as something that comes at you from the outside, but something that your body does on the inside when it's reacting to a disease. And this is how we get to a place where we can gun someone and say, oh, you're sick. Stay away. Anyways, he publishes it all in this big book. And kind of incidentally, he was like, and in healthy people, when they are no longer sick, we have found that body temperature is 37 degrees Celsius. Which is the conversion to Fahrenheit is 98.6. Interesting. So he was just like, oops, I was studying this other thing. I accidentally have a cash million data points. Yeah, it was essentially a footnote. 98.6, that thing we all sort of bow before was just a little footnote from the 1800s? Well, yes, until this guy came along named Edward Seguin. Edward Seguin is the person who actually translated Wunderlich's work and introduced it to the United States. And he's really into thermometry. Which is a word. It was just a word, I know. He writes this manual called Family Thermometry, which is supposed to teach moms how to take their kids' temperature and why it's important and how to do it. And so Seguin, along with thermometer companies, kind of went on this big push through like. Articles in Good Housekeeping and Ladies Home Journal and Scientific American. To talk about thermometers and make them like a new tool for the home. And there are advertisements in all kinds of publications. And over and over again, they'd hammer on this number, 98.6, 98.6. That's what you should be. That's what your kids should be. And I feel like this like marketing campaign that happened at the end of the 1800s and the early 1900s is essentially been handed down to us through the century and made us think that 98.6 is the normal or ideal temperature for a human body, which is bullshit. Well, it turns out that there's a lot of variation across all these different parameters. So this is Catherine Lay. Infectious disease epidemiologist at Stanford University. And as Kat explained it to me, there is no one healthy human temperature. Women have higher temperatures than men. Bigger people have higher temperatures. Fatter and skinnier people have different temperatures. Taller people have lower temperatures. Whoa They just so thinned out that they got surface area for days I don know Hormones can change your temperatures Morning and night can change your temperatures Younger people have higher temperatures than older people I'm already thinking about the sweatsuits. I want to rock. And even in the same person, temperature taken in the ear, in your armpit, and your butt can vary by like two degrees. Well. Now, all this variation piles up to an average of 98.6. But just to really crack this thermometer wide open, and you might remember this from the episode I did last summer, Fungus Among Us, researchers don't even think 98.6 is our average anymore. Like there was just a new paper a year ago that said it looks like the sort of average of a healthy kind of Western population is 97.5. And Kat was actually involved in that research, and she said that it looks like our temperature has been dropping 0.05 degrees Fahrenheit every decade since the 1850s. There's a number of reasons they think that might be the case, like maybe we have better medicine, so we're not fighting infections as much. You know, maybe it's just the fact that we are older and taller, you know? Even the average is, I mean, I remember that episode, I was so focused on the scary fungus that I feel like I missed the teacher drop. It was just slipped in there, you know. But it's like you're saying, so not only is there all this individuality on person and time of day and part of body, but then also, oh, and also the average isn't the average either. Yeah. So much so that for some people, because you're a man, you're old, and it's early in the morning, coming up to 98.6 might actually be a fever for you. This is exactly why it's important to not believe that a number like your temperature can tell you everything. But even when you know that, it's so hard to let go of that number. I just got the COVID vaccine yesterday and I feel so rough. So I had this moment where, like, I got my COVID vaccination, my second one, and it, like, laid me low. So, so, so achy. And in the middle of that, I thought I should take my temperature. I was super achy and I really hurt. And so I, you know, turned on my voice memo. It hurts so bad. And my voice is ridiculous. And I think my fever must be like 102. And I take my temperature and it just comes out as 98.1. And I was just like, oh, am I? A big faker? Yeah. Am I making this worse than it is? Like the thermometer just said I wasn't sick. And then I like no one at Radiolab is going to believe me. The thermometer can't be right because it doesn't encapsulate. I'm terrible. despite knowing everything i just told you this is while you're in the midst of this reporting i'm in the midst of this reporting you are still like measuring yourself up against that number point six and and and so it's like all of that against against me and then in the middle of sort of like the fever haze, the non-fever haze, the non-fever fever haze. I'm like kind of hanging off the side of my bed, like very pathetic. And I was just like, this is just like what Deanna said. I think that acting as if fever, as a quantitative measure, can give you objective truth, just makes it impossible for you, not you, makes it impossible for anyone to see the full scope of what is happening inside a person. I definitely felt that in that moment, taking my own temperature. But I think I also realized that you can actually throw out the 98.6 thing, and then your temperature, whatever it is, can be a window into so much more about a person, like how old you are, what your hormones are, or whether you live in a place with adequate medical care. Can I add one more kind of eerie one? Of course. Of what your temperature might be able to tell you. So Hans, our researcher from before, he actually did a study where he wanted to see what predicted core body temperature. So he plugged in all these variables, age, height, weight, location, distance from equator, cigarette consumption, sugary drink consumption, perceived level of stress, any medications, access to a cell phone, like tons and tons of tons of things. And this thing that was right up near the top, more important than body weight or height, was diversity of your social network. And so what that means is like not how many friends you have, but how many different kinds. So like do you have your work? Oh, it's not number. It's groups or something. Yes, it's like your work friends and your soccer friends and your knitting friends and your extended family and the Webster sisters. And so like the more kinds of groups you had, the higher your core body temperature was. How do you, does he have any explanation for that? I think the, I mean, he doesn't know, like, he doesn't know exactly what that means. But I think there's some idea of like, if one type bails on you, the more types of backups you have, the safer your body, the less at risk your body feels. It's just there's this very porous border between what I thought of as a very physiological thing, which is your body temperature, to what's happening mentally and emotionally in your brain. Like emotions tuning your body temperature to what it is. Which makes me think back on that temperature check tape a little differently. Like, Can I take a temperature? Yes, sir. Normal temperature. 96.1. Did you gain weight? 97.5. 96.4. What time of day is it? Temperature is normal. Maybe you're pregnant. 97.2 degrees. 97.7. Have you seen a doctor? 97.7. Did a stranger wave at you on the street? 95.4. 96.3. Normal temperature. Did you talk to your sister? 97.5. Are you on medicine? 95.5. Or maybe you're off it. Good temperature check. Do you live alone? Who do you love? Have you seen them? Molly Webster. This episode was produced by Becca Bressler, Molly Webster and me with production help from Karen Leong and fact-checking by Emily Krieger. Hans Iserman has a new book about a lot of the science we covered in this hour called Heartwarming, How Our Inner Thermostat Made Us Human. Special thanks to Tony Bartlemay, Julie Parsinette, Philip Makoviak, Carla Hawk, Lacey Alexander, Anna Stanowitz, Brendan and all the folks over at the Commissioner in Park Slope. Our listeners for their voice memos. Thank you, thank you, thank you. Temperature, temperature, temperature. And last big one to Invisibilia. I first started talking to John back when I was working with them and they let me use some of that audio. I really recommend you go check it out. Thanks for listening. Okay, so remember I said this book does have a fifth chapter. Ooh, the picture is just a scale in perfect balance. Okay. So you know how there's a kind of gnarliness to the concept of theft? Like kleptotherapy, this is all about how we are constantly— We're stealing something. Yeah, it's like that equation. You've got to take in more than you give. And if you don't get enough, you feel wounded and at risk. And if you are getting enough, you're stealing it from someone or something else. And if we got to an equilibrium, wouldn't that be so nice? Yes, equilibrium would be. So we're all giving and taking and coexisting, and it's a balance. Yeah. Okay. Do you know what that's called? You know what the physicists call that? No. The thermal death of the universe. Wait, equilibrium is thermal death? Yeah. Like there will be a time when everything becomes the same temperature. And that is the end. I don't know. I'll be grateful for the give and take. Be grateful for the give and take. We'll give you away to your life. That's the end. See you next time. Thanks for listening. Bye. Hi, I'm Eric Baum. And I'm from Minneapolis, Minnesota. and here are the staff credits. Radiolab is hosted by Lulu Miller and Latif Nasser. Soren Wheeler is our executive editor. Sarah Sandback is our executive director. Our managing editor is Pat Walters. Dylan Keefe is our director of sound design. Our staff includes Jeremy Bloom, W. Harry Fortuna, David Gable, Maria Paz Gutierrez, Sindhu Nayasambadan, Matt Kilty, Mona Madgawker, Annie McEwen, Alex Neeson, Sarah Kari, Rebecca Rand, Anissa Vitsa, Arianne Wack, Molly Webster, and Jessica Young. Our fact checkers are Diane Kelly, Emily Krieger, Natalie Middleton, Anjali Mercado, and Sophie Semei. 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