Science Friday - Bird Poop Importance, The Wonders Of Sweat, Invertebrate Butts. July 8, 2022, Part 1

Episode Date: July 8, 2022

We Need To Talk About Bird Poop Seabird poop—sometimes called guano—was the “white gold” of fertilizers for humans for millennia. Rich in nitrogen and phosphorus from birds’ fish-based diets, the substance shaped trade routes and powered economies until chemical fertilizers replaced it. But while people may no longer find bird poop profitable, these same poop deposits—often found on islands or coasts where the birds nest and rear their young—may also be nurturing ecosystems that would be left high and dry if the birds were to disappear. As seabird populations quickly decline, that’s becoming an increasing risk. Australian researchers Megan Grant and Jennifer Lavers talk to Ira about the under-appreciated role of bird guano in ecosystems, and why scientists should be looking more closely at the poop patterns of endangered seabirds.     Sweating Is Our Biological Superpower Sweat 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.   From Zero To 100 Butts: The Wild World Of Invertebrate Behinds Recently, the staff of Science Friday came across a tweet that caught our attention, sent out by researcher Dr. Maureen Berg. Turns out, it was a call to source comic ideas for Invertebrate Butt Week, a celebration of—you guessed it—the butts of invertebrates. “Invertebrates really get the short end of the stick,” says Rosemary Mosco, the creator of the comic series Bird And Moon and #InverteButtWeek organizer. “People are not as excited about them as, say, a majestic whale or a beautiful bird. And I love my birds, but [invertebrates have] such an incredible diversity. So, butts are sort of a cheeky way to access some of that amazing diversity and celebrate it.” Rosemary and other scientists and illustrators teamed up to create #InverteButtWeek, a celebration of the behinds of the backbone-less. “It’s a chance for some people who do science communication to do the silliest thing that they can possibly think of,” says Dr. Ainsley Seago, curator of invertebrate zoology at the Carnegie Museum of Natural History.   Science Friday’s D Peterschmidt talks to the organizers of #InverteButtWeek about how it came together, their favorite invertebrate butt facts (like how sea cucumbers have anal teeth), and how you can participate in the celebration.   Transcripts are available 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'm Ira Flato. A bit later in the hour, a look at them sweat. No, don't change the doll. You're going to like this. But first, every coastline has his birds. And where there are birds, there is, of course, bird poop. And if you live near a beach, you know this well. Whether ducking what may fall from a flying gull or observing the distinctive white color on those offshore rocks. This bird poop or guano, white gold, as it was once called, was you. used by people for millennia to fertilize crops. That's because it's rich in nitrogen and phosphorus, key nutrients for plant growth. And seabirds leave it, well, everywhere, but especially in the places where they build nesting colonies during the breeding season. Seabirds continue to shape

and potentially enrich their ecosystems on coastlines and islands around the world. So what happens if the seabirds are at risk of extinction? Here with more about what we know about the important role of seabird guano and what we still need to know are my guests megan grant phdd candidate at the university of tasmania and researcher at the adrift lab in australia and dr jennifer's senior lecturer in marine sciences also at the adrift lab welcome both of you to science friday hello thank you for having us our uh nice to have you mgan why did you decide to research seabird guano in the first place I suppose it's not the sexy topic, but I think it's really interesting because seabirds are so integral to terrestrial environments.

It's quite unique in that they move nutrients from the marine environment to terrestrial environments. And that form of movement doesn't happen very often. Most of the nutrients flow from terrestrial areas to marine environments, not the other way around. So seabirds are incredibly important. And seabirds have been suggested as the most important vector or transport mechanism for the movement of nutrients out of any animal on earth. Tell us about this incredible island. Introduce us to that area you studied. Yeah.

So I work out on Lord Howe Island, which is located roughly halfway between New Zealand and Australia. It's a tropical island with roughly 300 residents. living on it and it's home to thousands of terrestrial birds as well as sea birds. And one of these species is the flesh-footed shear water. You may know it as a mutton bird. These birds come to Lord Howe Island and breed. So rather than being a surface nester, like say a gull, they burrow into the ground and their burrows can be two to three metres long, which is incredible for such a small bird.

I mean, it's incredible considering they dig these burrows with their feet. It's crazy, crazy to think. No kidding, that is crazy. These birds come to Lord Howe Island to breed, then they fly back up to the Sea of Japan, so in the northern hemisphere, forage there and live there, and then, yeah, come back to Lord Howe Island to breed. Now, I mentioned all the nutrients in bird guano.

Do we have clues that the flesh-footed shear water is fertilizing Lord Howe Island with all its guano. Absolutely, yeah. So the vegetation structure in the Sheawater Colonies is predominantly palm species, and it's one species of palm called the Kentia palm. There's very few other species. It's pretty much 95% palm tree. And then if you walk to the edge of the colony and then step out of the colony,

the vegetation structure changes almost immediately. All of a sudden you get a variety of shrubs and other tree species and other palm species. And yeah, so it seems like there's this really intricate link between the shearwaters and the vegetation on Lord Howe Island. And that's where this idea that the shear waters are bringing really beneficial nutrients to the island. And these areas, these colonies where the seawater's are, the vegetation needs the nutrients from their guano to survive. So that's the connection. Yeah, that's the connection. The palm trees and the guano. Yeah. Interesting. Jennifer, what are some other places where we might

be able to notice this connection between seabirds and their ecosystems? Virtually everywhere we look, really. This is the fascinating thing about seabird colonies. Once we see this or we become aware of their ability to kind of drive their habitats or be what we call ecosystem engineers, which is quite a cool term, then we'll start to recognize this pattern everywhere we look. And the vegetation that occurs where those seabirds nest essentially evolves or adapts to the response of the birds being present. And so you get this really intimate relationship, as Megan said, between bird and tree, and only certain trees exist where the birds are. And in the case of the sheer waters, or the mutton birds that we're studying on Lord Howe Island, they're also what we call turbating or turning

over the soil as they dig their burrows over and over again and basically making a big mess of the place. And so that turning over the soil and that constant depositing of these nutrients really dictates what can grow there and what can't. There's a really great, although I suppose a little bit sad example from the Aleutian Islands in Alaska. It's probably one of the better ones that we know of where in the early 19th century we introduced foxes as part of the pelt or the fur trade. And the foxes in very short order removed the seabirds basically ate them for lunch and dinner. And the seabirds were gone. And so what we noticed for the vegetation, the habitat structure on these Aleutian islands in Alaska was that they very quickly

transitioned from being kind of woody and shrubby and having trees and things to now those islands are grasslands. And so that was one of the most kind of marked or clearly demonstrated examples of if you remove seabirds from these habitats, those habitats just don't look the way they used to look anymore because they're not getting the things that they need to maintain those, and other life. And Megan? So, I mean, part of my PhD is looking at how the Shearwater Guano links very closely to not just the Kentia Palms that I was talking about, but also to the soil and the soil invertebrates as

well within these regions that the Shearwater's breed. For the soil invertebrates, I'm studying an invasive species, which is the leopard slug. to see whether they also have similar nutrient levels to say like the guano that the shear waters have deposited. But this can be said for, you know, seabird colonies all around the world. It's not just the vegetation that the seabirds influence. It's the soil and it's the soil invertebrates. I can't remember the exact location, but there was an island somewhere where there were seabirds and they compared it to an island without seabirds,

and the island with seabirds, the iguanas were longer than the iguanas on the island without seabirds. So there are huge flow-on effects from having seabirds in a region compared to without seabirds. It's phenomenal. So that brings me to this question. We're talking so much about what we do know. Megan or Jennifer, what do we still need to know?

Well, I'm just thinking of your wonderful review paper that you just did, Megan, and it really pinpointed to us that there are, I'll say, a handful, maybe a dozen seabird species that Megan was able to identify that are endangered or critically endangered. Some of those are known to have been quite heavily involved in the historical guano trade. So we know that there were significant quantities of guano. in the past, so much so that our original human societies were based around harvesting of that guano and transporting it around the globe when using it as fertilizer and various kinds of things. Those seabird populations are now numerically far less abundant to the point where they've been listed as vulnerable or endangered.

And when Megan was looking at what do we know about these species with regards to their guano and their population sizes now in various aspects, the answer was kind of not enough. So we've lost a lot of these birds. We've clearly have the potential to lose significant amounts of guano with that. And yet simple things, very basic metrics like how much nutrients is actually in the guano of that species. So what exactly have we lost or what could we regain if we restore these vulnerable and in a endangered species? We couldn't really answer that question because basic measurements of the value of their guano just aren't available. And Megan?

I was going to say a very similar thing in that I think it's really important to start studying the species that we could possibly lose. Megan, I understand that perhaps you can tell people how important seabirds are. Are you consulting on a video game about guano? So this is just, I mean, when my review paper was published, I put it up on Twitter just to basically say, look, I've written a paper, please go and read it and all of that. And then I had someone comment on that post and said, oh, you know, we're making a board game about guano. We would love to ask you some questions.

P.S. This is not a joke. and I didn't know whether to take this person seriously because even though they said it appears it's not a joke it sounded like a joke I mean who makes a board game about guano and basically they're making a game a board game about the guano trade when guano was a hot commodity basically and in some instances it was valued more highly than gold anyway so they're making a board game about this. And they've asked me to be their scientific consultant, which is super exciting. Wow. Wow. Yeah. Well, you let us know when that game is out? It's coming out next year. So I can't give away too many details because it's still in production. Okay. I get it. I get it. Hush, hush for now.

Yeah, exactly. Well, we'll have you back when it comes out, okay? Absolutely, yeah. Thank you both for taking time to be with us today. Oh, thank you so much for having us. It's been an absolute joy. It was wonderful talking about poo all morning. Any excuse? Megan Grant, a PhD candidate at the University of Tasmania and researcher at the Adrift Lab in Australia, and Dr. Jennifer Laver's senior lecturer in marine sciences, also at the Adrift Lab. We're going to take a break, and when we come back, the secrets of sweating. Why we do it, why we might even want to embrace it. We'll get a good schvitz after this, as they say. 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 is 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 schvitz, 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 Everett's 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. 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 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, you know, 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 smartwatch add-on. And you get a little push alert because your sweat patch has noticed 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. and 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 Crine 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 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. You have to tell the story of a woman who's 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 colors 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 of 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. tips. 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 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, you know, 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 SciFri 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 sadden 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 salivating, and 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 adjustments 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 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, 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. Yeah. Me 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 the.

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 Everett, 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 Leneta 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 is 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 sweat glands 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.

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, antiperspirants 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 hundred years, deodorant 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 close the buffet so that these bacteria go hungry and get. 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. What about manipulating the microbiome? Maybe some probiotic that's in the odor that compete. with the bacteria, right? Yeah. So that's not a totally new idea, but you could imagine people trying it out. And there's one really fascinating researcher who's studied what's called armpit transplantations.

But instead of like, you know, lifting the skin, effectively, it's just like lifting the bacteria from one armpit and putting it into somebody else's armpit. So say you produce pretty stinky odors. It could be because, you know, you have a higher proportion of corn, a back. bacteria in your armpit than, say, Staphylococcus, and say, I produce less, maybe I could donate my armpit microbiome to you. He's only had success with twins, like very close family members, because, of course, the bacteria living in your armpit, they are living there because they love your skin, right? They love all the weird little components that you produce in your sweat, your acrine sweat, that salty stuff. They love that ecosystem and they're probably

pretty well established. So it's actually very hard to disrupt a person's microbiome if they're healthy. Maybe putting less smelly bacteria in your armpit might be a solution, but so far it hasn't worked. Sarah Everett's 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. As you probably know, if you listen to the show, we're big fans of the microbiome, microbes that live in the gut. But one related subject that we don't talk about as much is what happens at the end of the gut. Yeah, I'm talking about what even scientists call the butt. But what is a but anyway? And why are so many scientists celebrating it for a whole week? But I digress.

Digital audio producer D. Peter Schmidt has the story. A few weeks ago, we saw a tweet that kind of caught our attention. Do you mind reading the tweet that you sent out back to me? Hold on a second. Let me get it up. Hello, does anyone know of any animal that has a few butts, like more than one but fewer than 100? And I'm generally talking butts as the anus, but I'm open to other interpretations.

That's Dr. Marine Berg, a scientist at the Joint Genome Institute at Berkeley National Lab. You probably aren't sitting around thinking about animal butts, but Marine is a part of a group of scientists and illustrators who think about them, a lot. She got her start in invertebrate biology, and invertebrate butts, or invertebuts, have become one of her passions. She's even given public talks about them. Now I'm known as like the invertebrate butt girl on Twitter. So anytime any like kind of new

animal butt thing comes up, I always get tacked in these. It's just like a standard procedure at this point. Even though I do no research in this field, I'm just once again, I'm just the loudest person about this. Yeah, how do you feel about that of that being your calling card now on Twitter. I'm honored, honestly. So now, people tag her in tweets when certain discoveries are made. There's a recent worm that was discovered

that has hundreds of butts. That worm, Rem Silas Multicadada, isn't like most worms. Its body segments and branches out at multiple places, looking more like a connected series of cracks in a dried-up riverbed than a traditional worm, and at the end of each of these dozens of branches is an an anus. I'm always looking

for comic fodder and that one kind of wrote itself. Turns out, Maureen isn't the only one fascinated with invertebrate butts on Twitter. I thought, oh my goodness, I have to do a comic about an animal with a zillion different butts. Science Illustrator Rosemary Moscow put together a chat group, appropriately named butt chat, and invited other butt-enthusiastic illustrators and scientists. I mean, what were your initial reactions to just being involved in this project? Oh, complete lack of surprise. Dr. Ainsley-Sigo, the curator of invertebrate zoology at the Carnegie Museum of Natural History

in Pittsburgh was one of the researchers who got invited to this butt chat. And like Marine, she'd also given a talk about bug butts before. She started a small document with some of her favorite butt facts, threw it into the chat, and the other members started adding to it. I think at one point I said, oh no, we've opened Pandora's butt. There were so many different pieces of information flying in this chat. The group decided they'd team up and use their combined science and illustration powers for good, by making comics about the backends of the backboneless.

They're calling their celebration Invertebutt week, like Shark Week or Ceplepod Week, but for invertebrate butts. It's just a chance for some people who do science communication to do the silliest thing that they can possibly think of. We love talking about this stuff. Sometimes you get really tired of only covering the depressing news or only covering the extremely technical details. And this is something that's both educational and delightful, frankly. So we've got lots of information, but not an answer to the big question. What even is a butt?

There's been discussions on science Twitter in the past about what is a butt. Is it just like kind of the back end of an animal or is it like the anus? Some purest researchers are a little anal about this and believe that the word but should only be used when referring to fleshy buttocks. Marine and Ainslie have more generous views on this. You got one end where food comes in and one end where poop goes out. That second end is in my mouth. personal definition of the butt. It does get challenging when you think about questions like if a bug wore pants,

would it wear them like this or like this? But I think we can conclude that what would we in insect morphology terms refer to the abdominal apex is, I would say, with zero ambiguity the butt region. So, yeah, context is very important on how you define it, but I'm flexible on definition. And for a bit more context, we have to go back hundreds of millions of years ago to the Earth's oceans. most animals back then didn't have what we think of as a butt. Most just had a single multi-purpose whole for eating and excreating. The descendants of some of these animals are still with us, like coral and jellyfish. But as you might imagine, that one road set up had some serious drawbacks.

And so the idea with that is like you can only eat and then you digest your food and then you can get rid of your waste. Whereas with us as humans, you can continue to eat as you're digesting. You don't need to wait for your whole digestive system to clear out before you eat again. So the whole even concept of evolving an anus allows you to like basically eat and digest at the same time. So it's a little bit more efficient. The evolutionary marble of the digestive system and subsequently the anus was a big deal for life on earth. Animals got more out of their meals, bodies lengthened and grew bigger and developed better ways to move around like swimming, walking and flying, rather than say, just existing, floating in the water like a jellyfish. What's a butt that you think that more people should know about?

I mean, my favorite animal butt to talk about is the sea cucumber butt just because it does a lot of weird things. Like it's not just one weird thing that does a lot. A lot of sea cucumbers' butts act as homes for other animals. Like you have the fish, you have crabs, you have a lot of things that live in the butt. And because, you know, maybe you don't want just any animal living in your butt, a lot of sea cucumbers have anal teeth to prevent certain animals from inhabiting their butt, essentially. Because what some will do is they'll get into the butt and they'll start kind of munching and

gnawing on the gonads and stuff, which is obviously bad. So they kind of have it all. They have like eating, breathing, defense, apartment building. Like they have it all and I really admire it. It would get like the most versatile butt award. Exactly. I want to talk about the face mite. The best part about them is that they don't have butts. Franz Anthony is another science illustrator working with Rosemary on the project. The problem when someone doesn't have butts is that, they can poop. So throughout their life, their body just gets longer and longer as their poop accumulates inside. And then once they die, they just burst open and then the my poop is basically all over

people's faces. And I think that's really, really fun. And I don't like to pick favorites, but Ainsley's preferred butt might be mine now too. One of my absolute favorites is the Neuropteran family barothity. Their type of lace wing, small insects with large clear wings, and their larvae live in termite mountains, which is a pretty dangerous place. to grow up. Termites are essentially soldiers. They're territorial and dangerous and they don't want any intruders in their home. So how do these seemingly defenseless larvae defend themselves when termites approach them? They turn around and wave their button in its face and release an invisible but powerful gas that knocks out the termites almost instantly. So they're essentially

farting them to death as a form of defense. And it's just one of the most beautiful things that nature has come up with in her infinite wisdom. That's the central thesis of inverted butts week, which is let there be joy. It's okay to have yourself a secret little chortle that's farting another animal to death. That's pretty great. I wanted to end on this question, which is, why should we care about butts? I'll take my answer off the air. Listen, I don't think that butts are necessarily the most important thing going on right now in society. But I think that butts are something delightful to think about. And looking at one particular body part of an animal can be a way to look at an entirety of an animal and look at the way that it experiences the world. Yeah, I think butt in general is

just really funny because it's really accessible. Even kids understand it. So it is a good way for kids to understand bigger concepts. And adults too. I mean, I think like adults are already so excited about anything goofy and butt-related. So I think we all need to hop aboard the butt train and write it to Science Town. I'm so sorry. Unfortunately, you've missed this year's Infertibut Week, but who knows, maybe it'll be an annual event. In the meantime, though, you can check out illustrations from Rosemary and friends and others on our site. That's at ScienceFriiday.com slash butts.

For Science Friday, I'm Dee Peter Schmidt, National But-Correspondent. Thank you, Dee. Hey, before you go, can you fill us in on some of the folks who helped make this show happen? Sure thing. John Dankoski is our director of news and audio. Annie Niro is our individual giving manager. Flissomeres as our office manager, and Charles Berkwist as our radio director. Thanks for listening.

Thanks again, Dee. And that's about all the time we have for this hour. BJ Leiderman composed our theme music. Have a great weekend. I'm Ira Flato. Thank you.