Science Friday - Embryo Model, Sweat, Whale Vocal Fry. September 8, 2023, Part 1

Episode Date: September 8, 2023

Scientists Develop Human Embryo Model Without Sperm Or EggsThis week, research published in the journal Nature detailed a model of a 14-day old human embryo created without using sperm or eggs. The hope is to shine a light into a previously unavailable window of an embryo’s development, potentially helping to better understand miscarriages and side effects of medications taken during pregnancy. Ira talks with Casey Crownhart, climate and energy reporter at MIT Technology Review to talk about that and other top science news of the week including Japan’s rocket launch to the moon, zinc batteries, and newly discovered toxic bird species.Sweating Is Our Biological SuperpowerSweat may feel like a constant summer companion, whether or not you exercise frequently. Being damp can feel uncomfortable, but the smells that follow—thanks to the lives and deaths of sweat-munching bacteria—are often socially stigmatized as well. (Deodorant itself is actually a very recent invention!)But sweat isn’t just a cosmetic embarrassment: It’s crucial to keeping us cool, as the evaporating liquid pulls heat energy from our bodies. If you look at animals that don’t sweat, many have evolved alternate adaptations like peeing or even pooping on body parts to achieve that vital evaporative effect. People who are born unable to sweat run a constant risk of heatstroke.Ira talks to Sarah Everts, author of the new book, The Joy Of Sweat, about what makes sweat useful, the cool chemistry of this bodily fluid, and why it’s our evolutionary superpower.Vocal Fry Serves Up Treats For Toothed WhalesToothed whales—species like orcas, bottlenose whales, and dolphins—use echolocation to zero in on prey about a mile deep into the ocean.Until now, scientists couldn’t quite figure out how the whales were making these clicking sounds in the deep ocean, where there’s little oxygen.A new study published in the journal Science, finds the key to underwater echolocation is vocal fry. Although in whales it might not sound like the creaky voice that some people love to hate, the two sounds are generated in a similar way in the vocal folds.Ira talks with the study’s co-author, Dr. Coen Elemans, professor of bioacoustics and animal behavior at the University of Southern Denmark based in Odense, Denmark. To stay updated on all-things-science, sign up for Science Friday's newsletters.Transcripts for each segment will be available the week after the show airs on sciencefriday.com. 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 I Refledo. If you've done nothing else this summer, I'm betting, you've been sweating a lot. And as we all know, sweat helps us cool off as it evaporates. But what do animals that don't sweat? What do they do to cool off? Some unexpected things, as we'll find out, as we talk about the science of sweat a little bit later. But first, what do embryos, a moon landing, and arm joints? All have in common. Well, they're all part of our news roundup this week. Here with her selected short subjects in science is Casey Crownheart, Climate and Energy Reporter at MIT Technology Review, reporting from New York City. Casey, welcome back.

Thanks so much for having me back, Ira. You're quite welcome. Big news this week in the world of stem cell research scientists at the Wiseman Institute in Israel have successfully created a 14-day-old human embryo model without sperm or eggs. The findings were published in the prestigious journal Nature. Casey, why is this such a big? deal. Yeah. So these, you know, kind of synthetic embryos or embryo models, as we may call them, could be a really big deal for understanding the earliest stages of our development, creating new

drugs and treatments. And it's kind of a wild bit of science that these researchers had to do to make it happen. You know, like you said, instead of a sperm and an egg, this embryo model is made with stem cells, those cells in your body that can turn into a lot of different kinds of things. And by reprogramming them, scientists were able to make a small fraction of them, kind of spontaneously come together and assemble into something that looks a lot like a human embryo. Okay, tell us why it's like a human embryo. It's a model and not an embryo itself, which could become a person. Yeah, so a natural embryo really means that it's a sperm and an egg that come together and then, you know, kind of divide and turn into eventually a fetus and then a person.

And so because these were made with stem cells, it's not quite the same thing. But, you know, it starts to get a little bit fuzzy because this model was a really good one. This model even secreted some hormones that were able to turn a pregnancy test positive in the lab. So it's, yeah, really kind of wild. So what kind of knowledge then is there to be gained from embryo models like these? Yeah, so we could understand a lot more about kind of the earliest stages of human development. And it could also, you know, help scientists understand a little bit more stuff like really early miscarriages. Why do some early pregnancies work and some, you know, don't? So there's a lot of potential knowledge to be gained, but there's also a lot of kind of controversy around this sort of research. Yeah, because we all know, at least here in this country, embryonic research has a history of controversy, and I'm imagining this should be no exception.

Absolutely. I mean, there are really strict rules around researching natural embryos, but as these models start to look more and more like the natural real thing, it's not totally clear, you know, what rules should apply. Right now, a lot of researchers are kind of following the same rules that they would for natural embryo research. But it's definitely kind of this really early developing field. And as you said, this embryo was taken to 14 days. Could it actually go past 14 days? There's no kind of technical reason why these couldn't keep developing.

Like I said, so right now in the U.S. and the U.K. For a natural embryo, 14 days is pretty much the cutoff for when it's legal to do research. And so that's kind of why that 14-day mark is what researchers are sticking with. But, you know, there's no reason that this kind of thing couldn't keep developing further on. All right. Let's go on to our next story, which takes us to the moon, which is getting to be a pretty busy place. I mean, last week it was an Indian moon rover on the South Pole. And this week, Japan launched a rocket with a moon lander on board. What's the goal of this mission?

Yep. So this mission is kind of a similar one. So the goal here is to test out what's called a soft lunar landing. So that's a controlled, targeted touchdown. And if it is successful, in a couple of months or so, you know, like you said, this rocket just took off. But if it is able to land on the moon, that would make Japan the fifth country to do that. And what kind of stuff are they going to be studying there? So a lot of it is about kind of how to carefully touch down on the moon. And so, you know, kind of learning that so that as we start to go more and more places, we can land very carefully and precisely, which might be really important.

as we start to go places that are really resource limited. And there's a telescope on board too, right? Yeah. So a lot of people have been talking a lot about the moonlander, but the X-ray telescope that's on board. This rocket is actually kind of the main payload. And so this X-ray telescope is going to look into space using X-rays instead of visible light.

And it'll try to help us figure out, you know, how galaxies are shaped, how the universe formed, you know, just the small stuff. Cool, cool. Okay. Back here on Terra Firma, you have a story about a New Jersey-based company Eos, which developed a zinc battery. Now, what's so great about a zinc battery? Yeah, so we've got a lot more solar panels and wind turbines on the grid now, generating electricity.

But as you know, the sun doesn't always shine, the wind doesn't always blow. So a lot of people are trying to make batteries to store energy. The problem is the ones that we have for grid-based storage are pretty expensive. It's a lot of people use the same kind of batteries that are in electric vehicles. But we're looking for much cheaper ways to do that. And that's what EOS Energy is trying to do with this zinc-based battery to make a way to store a lot of energy for a really, really low price. And what's the shortcoming here? What's the trade-off?

They're not able to store as much energy in a small space. So, for example, a zinc-based battery would not work on a car. It would be way too heavy, way too big. But if you're, you know, trying to just build gigantic buildings to store energy for, you know, to power homes, that's not as big of a deal. Yeah. And so that's why these kinds of batteries have, you know, kind of specialized application. You know, Tesla's been doing them with lithium ions, but this would be zinc. Scaling up production, though, is the challenge all the time.

And it is, it is here too, right? Absolutely. And so the big news this week is that EOS got this big loan commitment from the U.S. Department of energy. It's about $400 million. It's a conditional commitment. So they have to kind of, you know, check some boxes. But this kind of funding is exactly what's so important with batteries. It's, you know, tough to make a battery in the lab. But a lot of people would say it's a lot tougher to take that battery, make a whole bunch of them and then actually get them out into the world to store energy. So this funding could help with that. Yeah, technology has this problem

all the time. Okay, more news on the energy front. The Biden administration announced that they'll be canceling oil drilling leases in the Arctic. What's the latest on that? How did this all come about? Yeah. So these leases were sold in January 2021, just as Trump was leaving office. But recently, the current Interior Secretary said that these sales were kind of legally flawed, the environmental review didn't really hold up. And so just recently, you know, they canceled seven of these oil and gas leases in the Arctic National Wildlife. refuge. A lot of groups are celebrating this. You know, we can't have any more oil and gas development and expect to meet our climate targets, according to the UN Climate Report. But it's not totally

clear what's going to happen going forward because this sale of these leases was mandated in a 2017 law to help pay for tax cuts. So it might not be kind of over yet. Yeah. We'll have those legal battles, I'm sure. Let's move on to a story about climate. climbing chimps. And from what I understand, scientists studied how chimpanzees climbing down from trees, how human shoulders and elbows may have evolved. Yes. So our arms look different from other primates, our shoulders and our elbow joints, but they look pretty similar to those of chimpanzees. And scientists weren't really sure how this evolution happened. But like you said, researchers were watching chimpanzees and another type of monkey called sooty manga bees.

go up and down trees. And they noticed that when both primates were going down trees, they did it pretty differently. The chimpanzees were extending their shoulders and elbows a lot more going down. So they were able to kind of come down very quickly in this sort of like, they called it a controlled fall. Sort of like a break. They were like good breaks. Yes, they're like little breaks to climb down trees. And so scientists kind of put together that this must be why, you know, our shoulders and elbows evolved the way we did is to be able to, you know, climb down trees better. Yeah. Did anybody ever think of looking at the, you know, the chimps climbing down versus up? I understand that an undergraduate student discovered this. Yeah, it's one of those wild things that, you know, they just weren't

looking at it. Climbing up the tree seems to be the more important part, but I guess coming down is just as just as crucial. Yeah, you're not burdened with all that graduate knowledge. Let's stay in the animal kingdom a bit. You've got some bad bee news for us involving invasive hornets, which are bees natural enemies. Tell us about that. There were 22 confirmed sightings in England this year of Asian hornets. I'll just say these are not the Asian giant hornets you may have heard about in the US a couple of years ago. These are smaller, so less kind of maybe scary to humans, but really, really a big deal for bees. So these hornets are native to Asia. They've spread to some other places and they prey on wild insects. Bees outside of, you know, this typical range don't really have any

defenses against them. And so this could be a big threat to local bee populations, other local pollinators, which there's all sorts of bad bee news, habitat destruction, climate change, pesticides, all this stuff. So this is kind of just another thing facing bees in England. Let's wrap up with some news that I dare to say is a little dangerous. And I'm talking about researchers finding two new toxic bird species in Papua New Guinea. Now I approach this very ignorantly. I don't know that I'd ever heard of a toxic bird. Is there such a thing? I had not heard of these either, but apparently researchers have known since the 90s that there are some species of toxic birds. You might be more familiar with poison dart frogs from South America. Yeah. That have heard about. Yep. So it's kind of a

similar sort of thing, where these birds have this sort of neurotoxin that they carry in their skin and in their feathers. And it can be kind of irritating and itchy at low doses. You know, at high doses, it can be, you know, cause paralysis or even be fatal. Scientists think that these birds use these toxins as a sort of defense against parasites and that they get them by eating poisonous beetles and then storing it. But they're not totally sure how these birds became toxic in the first place. So the poison doesn't attack the bird itself. It's sort of immune, but anything that wants to eat it is going to get hit. Yep. They've evolved some sort of defenses against this toxin. And again, we're not 100% sure exactly how that happened. But they've kind of, you know, pulled the Uno Reverse card and used it to their own advantage. Well, let's say this is adding to my ever-growing list of reasons not to touch unknown wildlife.

Yeah. No matter how cute they look. Thank you for taking time. to be with us today. Thanks so much for having me. You're welcome. Casey Crownheart, Climate and Energy Reporter at MIT Technology Review here in New York. After the break, have you been just a bit warm lately? We'll talk about the cool science of sweat. Stay with us. This is Science Friday. I'm Ira Flato. You know, whenever the weather turns hot, the conversation turns to sweat. You hate sweat, right? your clothes stick, your head is dripping, your deodorant as well, well, let's not go there. On the other hand, lots of people seek out sweat, whether it's hot yoga or a steam bath,

there's nothing like a good schitz, as we used to say. So is it good, or isn't it? My next guest is here to suggest you celebrate that sweat, no matter how profuse. Don't be salty. The chemistry is cool, even. It's our evolutionary superpower as human beings, and if we didn't have it, she adds in a new book, we might be left doing some even less savory things to keep cool. Yes, we'll talk about that. Here with me now is Sarah Everts, science journalist, author of The Joy of Sweat, Strange Science of Perspiration. Welcome, Sarah. Thank you for having me.

Let's talk about the joy of sweat for a moment because there are people who do seek it out. They go into a steam bath. They like hot yoga. It feels good to sweat. Yeah. Yeah, and in fact, when you sweat profusely, you release happy hormones, the same sorts of things that give you the runners high. And so I think, you know, there is sort of an emotional catharsis that we have when we sweat. And, you know, most cultures at one point or another have some sort of sweating ceremony from the sweat lodges of the indigenous peoples of the Americas or the Jim Jill Bangs in Korea or the banyas in Russia or, you know, the saunas and.

in Finland. And so we all seek out some sort of sweaty catharsis at some point or another. Let's get into what sweat really is because I've had for many years a misconception, you know, that sweat is just water and salt, but it's actually very closely related to our blood. Where does it come from? What happens to it before it appears on our skin? Why does it get there? Give us a little bit of the ABCs. Sweat is actually sourced from the watery parts of blood. blood plasma. So, you know, the red blood cells and the platelets and the immune cells have been filtered out. And that liquidy part is what keeps your body on the inside wet. So we are

salty oceans inside. And when your body gets overheated and you get the temperature directive to start to sweat, your sweat glands source that perspiration from this fluid that is percolated out of blood. It's called interstitial fluid. And so pretty much anything that's small and is circulating around in your blood system can emerge out your sweat pores. I had my sweat analyzed by a forensic scientist actually who took an analysis of even just a fingerprint of mine. So fingerprints are just sweatprints, right? And she could tell that I had had a morning coffee because there was caffeine that had emerged out in my sweat pores. If I had, for example, added a little shot of whiskey to my coffee or a little something more illegal,

all of that also emerges out in your sweat because it is circulating in your blood, as well as glucose, you know, urea, proteins, all sorts of interesting things come out and sweat. Do you think someday we might be able to use sweat as a fingerprint? because maybe you have a unique sweat profile or something like that. Well, I do know that forensic scientists are certainly interested in sweat fingerprints. So normally when you think of forensic scientists looking at fingerprints, they're looking at the whirls and swirls. They're looking at how it physically looks,

and they're comparing an image of a fingerprint to that of a database. Well, chemists are now actually analyzing. the chemistry of fingerprints. And they're able to find out all sorts of information. And in fact, that scientist who analyzed my fingerprint, she works with law enforcement trying to develop this as a technique. And she, for example, analyzed a single fingerprint lifted from a window sill where a stalker had tried to break into a house and found that he had been consuming alcohol and actually cocaine. And so I do think that there will be forensic analysis of fingerprints coming up. But I also think a lot of people are really into personal measurement. And that can also give us super

interesting information. So say you have a little Band-Aid-like sweat patch analyzing what's coming out of your skin or a smart watch add-on. And you get a little push alert because your sweat patch has notice that your blood alcohol level is probably higher because there's alcohol in your sweat. So it tells you maybe don't drive home after the bar, take a cab. Or you can imagine coaches on the sideline keeping tabs on the sweating of their players, say in a really important match, a player starts getting stressed and starts releasing stress hormones or signs of fatigue. That might ping the coach to, hey, let's switch out that player for somebody new. There's all sorts of applications like that that are less dystopian than the forensic applications, too.

We don't just have one kind of sweat either. There's regular sweat and then that funky armpit stuff that we get starting with puberty. But tell us about the differences between those two. Yeah. So at Cron Sweat, the stuff that we've been talking about, that's responsible for cooling us down. But there is another. And those are the apricrine glands. And those are found anywhere where hair grows at puberty. That kind of sweat isn't watery at all. It's actually more waxy. And when bacteria, living in your armpits, eat that sweat. They metabolize it into the very stinky odors that,

you know, start emerging out our armpits at puberty. So it's kind of like a good news, bad news situation, right? Most sweat when it emerges from our pores is not smelly. And the thing that's responsible is the bacteria in your armpit. But on the downside, it's actually bacterial, effectively bacterial poop that's making you stinky. So I'll leave you to decide whether you find this heartening or not. So it's not just your armpit then that may be stinky. It may be anywhere where the sweat collects and bacteria can get to it. Exactly. Yeah. You open your book with a story, and you have to tell the story of a woman who sweated red and how it baffled medical professionals.

Yeah, how alarming is that? So it certainly baffled medical professionals and it stressed her out, but it also super excited the medical professionals because can you imagine how often would you get to analyze red sweat? So she was a nurse, and she started noticing that around the, the collars of her white uniform and in the armpits, there were kind of red sweat patches. And, you know, she'd have to soak her work clothes for hours to get it out. So when they analyzed her body, they found that she was a super healthy 20-something nurse,

could not figure out what was wrong. And at a follow-up appointment was the finally the time where they cracked the case because she shows up. And her fingers have that kind of like reddish brown color that people who roll their own cigarettes sometimes get that kind of stain. And they knew that she was not a smoker. And so they're like, what, what is on your fingers? And she's like, oh, it was, you know, my favorite chips. It's a spicy corn tomato chip. And effectively, she had been eating upwards of 45 bags of chips a week. Wait, wait, 45 bags a week.

Yeah, of spicy tomato corn chips. And yeah, and because anything that you consume can end up in your blood system and your sweat is sourced from the watery parts of blood, some of that red-colored dye had emerged out her pores. And so when they put her on an elimination diet, her, you know, sweating red. cleared up and she just, you know, went back to the normal complaints we have about sweat, you know, dank odor and wet patches, but not colorful ones. That's interesting. You mentioned urea. How is sweat different from urine if they're both derived from our blood? Right. So this gets

to, you know, probably my biggest pet peeve, which is when people talk about going for a good sweat as a detox strategy. This is total hogwash. So effectively, because anything in your blood can emerge out in your sweat, lots of good stuff comes out like glucose and hormones, as well as bad stuff. But if you were to detox by sweating profusely, you would literally have to get rid of all the water in your blood out your sweat pores. That would completely dehydrate you and you would dry up and die. Instead, your kidney filters your blood for that nasty stuff floating around your bloodstream, filters it out and then dispatches it out in urine. And so, you know, sometimes there's urea in your blood and that gets siphoned off by the kidneys and dispatched out in pee,

as well as like all the other bad stuff. That's why we evolved the kidney. Sweat is entirely, at least that salty stuff, that is entirely just for cooling down. Speaking of unusual sweat, let me go to a clip we have from Brandt from Brooklyn. He has a question on the sci-fry Voxpop app. I don't just sweat in the summer. I sweat year-round. I do have sweaty armpits, but they don't bother me as much as my excessively sweating hands because I have to use my hands for things.

I have had Botox injections to help with the sweating. They do work, but they're expensive, they're painful, and they only last for about five months, and then the sweating comes right back. And he wants to know if there's anything more effective or inexpensive on the horizon. So what he's describing hyperhydrosis is a pretty serious sweating condition. And, you know, people who have it, you know, some can't even hold a cell phone or a pencil because it slips out of their hands.

And I am, you know, really sad in that there has not been more research on this. Botox is one solution, but it's only a temporary one and it's expensive. Some people try to take drugs to control their sweating, but there's often a lot of side effects. quite honestly, I wish that there were more strategies available. And I wish that more researchers dug into hyperhydrosis. One would think with all the people who have this, that the drug companies would be solviting. Maybe it's the wrong analogy to find a drug for this. Another bodily fluid. You know? Yeah. Yeah. Let's go into other kinds of disordered sweating. Tell us about any other ones. Well, you know, there are some individuals who don't actually sweat at all. They have a genetic

condition that interrupts the development of sweat glands in utero. And actually, that is really debilitating because whether you find sweat annoying or not, it is essential for keeping you alive, because effectively you are sweating a tiny bit at all times, making micro-adjusting. to your body temperature because as that sweat is dispatched onto your skin, the evaporation of the water whisks away. It pulls away the heat from the surface of your skin. Meanwhile, your blood is rushing by. So have you ever noticed when light-skinned people get really hot, they turn red? That's because their vascular system has pushed up veins as close to the surface of the surface of of the skin as possible so that the cooling evaporation of sweat can cool the blood rushing by.

And so then that blood can go back into the interior and cool you down. And so people who don't have sweat glands at all, they have to, you know, spritz themselves with water constantly. It's very uncomfortable to live in even a slightly warm climate because their body can't make those micro adjustments to body temperature. So it must be dangerous. Oh, yeah. Yeah, it's life-threatening. I mean, you know, as much as it's kind of annoying to be drippy on a hot day,

it's your body just trying to do its thing to keep you alive. Heat stroke is a terrible way to die. I knew before I read this book that people are some of the only animals that sweat, but you really want us to see sweating as what makes us special, our evolutionary superpower even. What makes it so super for us? Right. Well, it makes it so super

because we can exercise and run and effectively cool down at the same time. So if you think about our evolutionary history, most of our prey sprints way faster than us. But we, because we have this huge, naked surface area of skin, right? Most other animals are covered in fur. We're a naked ape. We have this enormous surface area for cooling down. So our prey would sprint away way faster than us, and we would start running after them. And eventually they would have to stop and cool down so they

didn't overheat. And we could catch up, forcing them to sprint again and catch up and sprint again until they were so exhausted or that they were easy to kill or they died of overheating. And so, you know, the modern incarnation of this is marathons, of course, right? We can run great distances and cool down while on the move. And if you just think about dogs, for example, the way a dog cools down is by panting. And it's sticking out its tongue and it's also evaporating water, but it's evaporating water from saliva. And it's evaporating it off the only naked surface area it has, which is a tiny little

tongue in comparison to, you know, their whole body. And, you know, if you think about that, we have such a larger surface area off of which we can cool down. And this allows us to live in really hot climates. It's allowed humans to, you know, populate a good chunk of the world for better or for worse. I also noticed that some of the options animals have for keeping cool are, how shall I put it, pretty gross. Alarming at best is how I would put it. I mean, like peeing on their feet, pooping even sometimes? Yeah, so this is the thing, right? So evaporation of water off the surface of your body, this is the most efficient way to cool down.

And so, you know, if not sweat, then another bodily fluid. And so dogs use saliva, which is arguably gross, but not as gross as urine or poop. So, for example, vultures will poop on their own legs. It's quite a liquidy poop to evaporate the heat off themselves. Seals urinate on themselves. Honeybees vomit on themselves to get water onto the surface of their bodies to evaporate away the heat. And so when you know what could have been, when you know what evolution might have bequeathed us, you know, sweat is a lot less gross than all of those other things. I mean, imagine a subway in the dead of summer where people are peeing, puking, you know, licking themselves so that they can cool down.

In contrast, sweating is so much less gross. We have to take a short break, but when we come back, there's more. Yes, we're going to keep on sweating with author Sarah Everts, author of The Joy of Sweat. And to our listeners, if you want to read an excerpt from the book, no sweat. Just go to science Friday.com slash sweat. This is Science Friday. I'm Ira Plato. We're talking about sweat, the chemistry, the physiology, and even the forensics of it. With my guest, Sarah Everts, author of the book, The Joy of Sweat, the Strange Science of Perspiration,

and boy, are we finding out just how strange some of this is. I want to bring in a question from Lynette in California. She sent this in via the sci-fi box pop app. and it's a question I have too. I recently learned that there are differences between tears depending on why they're produced. I'm wondering if the same is true with sweat. Is the sweat that the body produces because of stress

the same as the sweat that's produced because of heat? Thank you for that question, Lynette, because I have the same question about nervous sweat. Why do we sweat when we're nervous at all? What does that have to do with cooling off the body? and are there two kinds of sweat? Yes, I love this question. So we can sweat because our body gets hot, right?

As soon as our temperature rises and all of our, you know, two to five million sweatlands open up. But another way to open up the floodgates is stress hormones like adrenaline. And so if you're panicked, you can also start the sweating. And, you know, like we don't know exactly. why that is evolutionarily, but you can imagine that most of the time when you're fearful, or at least in our history, you kind of had to run away really quick or climb a tree or do something like that. And so it's possible that our body is effectively assuming that we're going

to need to cool down pronto. But what's really interesting about fearful sweat is that there might be a unique odor that we produce when we are stinky. So research, have followed up on this kind of weird idea that we might produce an anxious odor. And they gave people t-shirts to wear and put them in front of a television screen. And they watched either a nature documentary or they watched a really scary movie and got the subjects to sweat. And then they took away these odor samples and gave it to a panel of sniffers. And what's really interesting is that these complete strangers could distinguish, you know, just normal B.O from the body odor produced during an, you know, a moment of anxiety. And so we do sniff out information about others around us. And yeah, chemists are hard at work trying to pluck that molecule out. But they haven't been successful yet, but they're certainly working on it.

I know you also investigated up close, another mystery of sweat, and that is we can be attracted to other people's sweat smells. Tell us what you learned about sweat and love. Okay. So I went to Moscow to go to a sweat dating event where people sniff body odor as a way to find love and romance. And the idea is that, you know, whether or not you find somebody attractive or likable or the hobbies match, at some point, you're going to smell the body odor of the person you are with, and it's going to be a make-or-break moment. And so why not cut to the chase or kind of eliminate the chase and do your, like, filtering for potential dates by body odor?

And certainly humans have a body odor print. We know this because dogs can track a specific human based on a sample of their t-shirts, right? And, you know, we do smell one another. In fact, you know, parents can identify the body odor of their newborns just within hours of birth. Siblings can identify a long-loss brother or sister after two years of being apart. So we do recognize the body odor of others. And in fact, there's been all sorts of tantalizing research that suggests that how our partner's smell is involved in whether or not we're attracted to them.

So, you know, the famous t-shirt study by Klaus Vedekind is when women were given the t-shirts of men. And by the way, all this research is very heteronormative with, you know, know, cisgendered straight couples. And I wish it weren't so. I wish that they would evaluate a greater diversity of human sexuality. But when women were given these stinky t-shirts of men to smell, they found the men with the most complementary immune systems to be the most attractive. And by complementary, I don't mean same. I mean different enough that any progeny that they would have together, would have a very strong immune system. And if you think about it, it makes sense.

For most of human history, our major foes have been microbial, right? We've died from plagues and pathogens. And so it behooves us to try and find a mate that will create, you know, children that can survive these pathogens. Let's talk about all the tricks we use to sweat less or reduce the smell of our sweat, anti-perspirants and deodorants. Have we mastered this yet? I mean, are we tired of swiping our armpits? Yeah. Well, it's interesting because this is actually a relatively new phenomenon. For most of human history, we have either lobbed on perfume if we were anxious about our BO, or we've washed with soap and water or just water and then lobbed on perfume. There's this way in which the last 100 years, deodorant and antipersercerant manufacturers have put the fear of sweat in all of us.

Deodorants are actually just antiseptics. And so they kill the population of bacteria in your armpit that eats your apricrine sweat and turns it into stinky odors. Whereas antiperspirants cut off the food supply by blocking your pores. So they, you know, close the buffet so that these bacteria go hungry and get it. can't make the stinky odors. But there are researchers, you know, trying to find different new strategies to fight odors. So some are looking at, instead of killing the bacteria, blocking the enzymes that the bacteria are using to make those stinky smells. So it would be kind of like a live and let live situation, but just don't do that one thing. Sarah Everts, author of The Joy of Sweat,

the Strange Science of Perspiration. Thank you for taking time to be with us today. Oh, it was such a pleasure. I want to end this hour with a story that's, well, how should I say, a whale of a tail. Toothed whales think orca, bottle nose whales and dolphins. Tooth whales use echolocation to zero in on prey deep underwater. And we're talking about a mile deep or more. Until now, scientists couldn't quite figure out how the whales were making those clicking sounds in the deep ocean where there's little air.

Turns out the key to underwater. Eccolocation is vocal fry. Yeah, that creaky voice that some people love to hate, only this time in a whale. Here's what it sounds like. Here to tell us more about this discovery published this week in the journal Science is my guest. Dr. Cohen-Ele-Mans, Professor of Bioacoustics and Animal Behavior at the University of Southern Denmark, based in Odinson, Denmark. He's joining us today from Washington. Dr. Ellumans, welcome back to Science Friday. Thank you so much for having me again. It's great. Can you begin by telling us exactly what vocal fry is for people who don't know? Yes, a vocal fry is one of the few human registers. We have at least three, maybe four,

where the vocal folds move qualitatively different in each register. And with vocal fry, the movements are such that the vocal folds are basically close for more than 60 to 80% of the time. So they're closed most of the time, and then they open very briefly and then they have a little snap. So a very little bit of air passes through. So why exactly does Vocal Fry help tooth whales with echolocation when they are so deep underwater? What we've been able to show now is that sound production in Tooth Whales actually occurs in their nose. And by combining a bunch of different experiments, we've been able to show that two pairs of phonetic lips basically make these echolocation clicks. So these echolocation clicks are made in the vocal fry register.

And one of the cool things of this is that when whales dive, of course, their volume of air decreases very, very rapidly and below 100 meters, they only have 10% left. Below a kilometer, they only have 1% left. So they need to be very air efficient. And this vocal fry registers allows them to be very efficient with their air. What are they actually doing in their, in their bodies, in their heads and the melon. When the whales dive, they basically shuttle all the air that's in their lungs into their nose. And there it goes into a cavity that's in the skull that cannot be compressed. So the air stays there safely.

And then the larynx, which we use to produce sound, lost this function in tooth whales. And it's become a very efficient plug. So it fits very nicely into this bony nose structure, basically. And that allows them to separate the two compartments, basically. So you have an air compartment in the nose and an air compartment that's very rapidly declining in the lungs. So when they dive, the lungs completely collapse and all the air moves in their nose. Now, this allows them to separate the control of these volumes. And that's been key, I think.

So one of the main things they can do is they can now pressurize the air in their nose to extremely high pressures without damaging lung tissue. So when we play, for example, trumpet really loud and would try to do it a few times louder, we would actually damage our lungs. And these animals uncoupled, these driving pressures, basically, in their nose and in the lungs. And then the other cool thing they can do is then they can use

this very high driving pressures to make the loudest sounds in the animal kingdom, basically. Now you categorize tooth whale vocalizations into three different registers similar to humans, vocal fry, which we just talked about. Then you have the chest register,

normal speaking tone, and the falsetto, even higher than the others, why did you decide to categorize them in this way? It's actually the other way around. When we realized that this was analogous to normal vocal fault oscillation, we realized that this huge diversity of sounds that these animals make actually fit very nicely in these three categories that are the registers. And then what we did is we tried to, through different lines of evidence,

try to show that this is also the case. And one line is the sound. So you see indeed that these. animals make distinct sounds that have different waveforms, but also different frequency ranges, just like registers. Then also the anatomy supports it. And lastly, we looked at the opening and closing of these vocal folds, first in vitro, but then later also using tags. We try to reconstruct the vocal fold kinematics of animals diving down to two kilometers deep, based on the sounds that we could record on these tags. Okay, let's listen to what these different registers sound like.

first the orca, the killer whale. Dr. Alamaz, tell us what we were hearing. Yes, so first you were hearing a few echolocation clicks. And after that, another sound these animals make, and this is definitely in a higher frequency range, right? And last was what's called a whistle. And these whistles go even up to 80 kilohertz in killer whales. It's really spectacular. They have an enormous frequency range they can produce. I am absolutely sure there's going to be lots of different sounds that don't necessarily fit in these categories, but this provides us first physiological basis to start classifying these sounds. Okay, now let's listen to the bottle-nosed dolphin.

It also starts with echolocation and then the other two registers. Wow. That really doesn't sound like the vocal fry I'm familiar with in people. No, so during echolocation, the frequencies are very low. Yeah, it's almost like a hearing test, you know, when they try to see how low you can hear. I'm Ira Plato, and this is Science Friday from WNYC, studios. This study, I understand, is the culmination of 10 years of research. And in that time, you had to develop so new techniques to study echolocation. How did you study the two whales?

Yeah, so I think what's really fun in these studies is that we use a lot of different approaches. So first, we developed techniques to film trained animals, so inside in their nose, with very small endoscopes and fast cameras. That allowed us to show that the source was definitely in the nose, but it also posed a conundrum because we saw there was clear motion going on with each echolocation click, but it happened after the click. So that was totally weird. And what we did then is that we developed a setup that we've also used for other species in the lab where we can blow air through an isolated head. It's very difficult to study these animals. It took several years to collect sufficiently fresh animals, basically, that died either in

in beachings or in fishermen's nets to be able to show really von der Lips make the sound. We also tagged animals where you put an acoustic tag on the animal. And we needed to be very precise to have the tag on the nose. And that was also seething through many, many years of tagged animals. Now, what did we know and what didn't we know about how tooth whales make vocalizations before this study? So what we definitely knew is that the sound was produced somewhere in the nose. There was a lot of different lines of evidence, but it's very challenging to film them.

And so people have tried to film them, but these were at insufficiently high frame rates to actually demonstrate these were the sound sources. But now we've established that it's actually that sound source and also the theory we established for human sound production is also applicable here in a completely new organ that's evolved only in these animals. This study focused on tooth whales as we've been talking about. What about baleen whales who also make sounds but don't use echolocation? What do we know about their anatomy? In baleen whales, it's a similar problem that we know all the things we know about their sound production are acoustic recordings and they're very hard to interpret because if you put a hydrophone on the water, you can record animals within several kilometers.

So it's very hard to pinpoint which animal makes what sound. And again, it's very hard to get fresh tissue there, but we know very little about the functional aspects of those baleen whales as well. Do they have the same origins, both kinds of whales? Both groups of whales evolved from a common ancestor about 40, 45 million years ago, and that was an animal that much resembled a hippo. And then at some point, echolocation evolved in these animals, and the tooth whales come out of that group.

And the other group became the Berlin whales. Huh. So echolocation seems to be the reason why they branched out. Given just how critical vocal fry is to how tooth whales evolved and hunt for prey, do you think this might change some vocal fry haters to better appreciate its usefulness? I really hope so. I really hope so. It was very funny because I've been very much focused on this over the last weeks, of course, a month.

If you listen on airports here or so, like, so many people you have vocal fry. At the start of sentences, at the end of sentences, and it's not just young women or old women or men or everybody does it. It's very common. Let's make it official. Let's call today Science Vocal Friday. Okay. Focal Friday. I like that one.

All right. Dr. Elements, thank you for taking to have to be with us today. Thanks so much. Take care. Dr. Cohen-Elemanz, Professor of Bioacoustics and Animal Behavior at the University. University of Southern Denmark, based in Odensa, Denmark. If you want to listen to those tooth whale vocal fry recordings again or check out some graphics explaining whale vocal anatomy, sure, go to our website, sciencefriety.com slash whale sounds. And that wraps up another show.

Have a great weekend. We'll see you next week. I'm Ira Flato.