SciShow Tangents - Poop

Episode Date: February 21, 2023

The bodily function so universal, there's a kids book all about how everybody does it! But... is that kids book a lie?! Find out the answer to that and way more in this very overdue episode of Tangents!SciShow Tangents is on YouTube! Go to www.youtube.com/scishowtangents to check out this episode with the added bonus of seeing our faces! Head to www.patreon.com/SciShowTangents to find out how you can help support SciShow Tangents, and see all the cool perks you’ll get in return, like bonus episodes and a monthly newsletter!And go to https://store.dftba.com/collections/scishow-tangents to buy your very own, genuine SciShow Tangents sticker!A big thank you to Patreon subscribers Garth Riley, Mike A, and Tom Mosner for helping to make the show possible!Follow us on Twitter @SciShowTangents, where we’ll tweet out topics for upcoming episodes and you can ask the science couch questions! While you're at it, check out the Tangents crew on Twitter: Ceri: @ceriley Sam: @im_sam_schultz Hank: @hankgreen[Trivia Question]Penguin poop distance traveledhttps://iposeogsekk.com/penguano.pdfhttps://improbable.com/ig/winners/#ig2005[Fact Off]AI listening to sounds of poop/diarrhea/farthttps://www.newscientist.com/article/2350082-ai-listens-to-toilet-sounds-to-guess-whether-people-have-diarrhoea/https://www.inverse.com/innovation/fart-monitoring-aiDagger made of frozen poop debunked (or, at the very least, not effective in lab conditions)https://www.sciencedirect.com/science/article/pii/S2352409X19305371https://nautil.us/the-problem-with-the-frozen-poop-knife-study-237572/https://www.cbc.ca/radio/asithappens/as-it-happens-friday-edition-1.5282456/why-scientists-tried-and-failed-to-make-a-knife-out-of-frozen-poop-1.5282458[Ask the Science Couch]Period poops (progesterone/estrogen & prostaglandins)https://my.clevelandclinic.org/health/articles/24411-prostaglandinshttps://pubmed.ncbi.nlm.nih.gov/3297513/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3823955https://health.clevelandclinic.org/why-do-you-poop-more-on-your-period/

Hello and welcome to SciShow Tangents. It's a lightly competitive science knowledge showcase. I'm your host, Hank Green, and joining me this week as always is science expert, Sari Reilly. Hello. And our resident everyman, Sam Schultz. Hello. I always say hello, and you always say hi. You've messed up everything, Sari. Wow. Wow. It's all broken now. I have a question. So say you're in a situation where it's not unusual for there to be a lot of guys, and there's a bunch of guys around what percentage of them being mostly too entirely bald do you start to think this is a collection of men who have gathered together because they have this thing in common i think that you could have 10 000 bald men together and they'd all be this is gonna be. They'd all be in denial and not realize any of them are real.

That's not how it works. They'd all think each other was bald and none of them would think, I'm bald. No, I think bald guys know they're bald. I think that it's above 75% I notice where I'm like, these are all a bunch of bald guys. Have you started seeing a lot of this happening? I know, I'm just kind of curious. I'm always curious about the thresholds

at which we start to think things are weird because weird things happen all the time. But like, it's only weird if we think it's weird. Somebody once made this great example to me. I don't remember where I came from, but it was like, sometimes you think, what are the odds that that would happen? So for example, what are the odds that that would happen? So, for example, what are the odds that a person would stop in front of you who has the license plate one number more than yours?

That's so weird. It's just exactly the same, but the last number is one up. It's very unusual. But every license plate you see at the car in front of you is a bit of a marvel. The odds that it would be exactly that number every time are very low. But the odds that it would be exactly that number every time are very low, but the odds that it would be some number every time are very high.

So what makes something weird is entirely just sort of a human experience of what is coincidental and not coincidental. And so I decided to explore this through the lens of bald men. Bald guys. Bald men. I think for me, over 50%. whenever a room is over 50 percent ish

and i know there's all kinds of problems with human estimation of what 50 percent is then i think something is going on but also i have been in enough rooms where there are mostly bald men and they're just like scientists yeah and like the thing that they are gathering is not about their baldness it is just that is the composition of scientists at elite institutions and so i like look at it and like yeah this checks out hate it but uh right right where like if you saw like a group of doctors and they are wearing white coats that wouldn't be weird because that's what doctors do but if you're at the grocery store and everybody was in an orange coat it would be very strange and so i think that we should go to the grocery store we should all wear orange coats we should all check out at the same time and know and be like how long is it going to be before how many

people in a row wearing an orange coat is it before the person checking out the boob in the boobing orange coat going on it's an orange coat thing in town yeah i don't think i'd ever notice personally i don't know i'm having trouble with this question because i think i could just walk i could go through a whole day seeing 100 bald people and then come home perfectly peace of mind. No, not just have some mac and cheese and watch Daredevil. Yeah. Yeah.

Yeah. And run my hands through my luxurious hair. Every week here on SciShow Tangents, we get together to try to one up a maze and delight each other with science facts while also trying to stay on topic. But for some reason, talking about large groups of bald men instead. Our panelists are playing for Glory and for Hank Bucks, which I will be awarding as we play. And at the end of the episode,

one of them will be crowned the winner. But first, as always, we have to introduce the topic with the traditional science poem. This week, it's from me. You think you know what happens to food. It goes in your mouth and then it moves right through from your face to your tummy and to your intestines, eventually all the way to your rectum. But actually, that's not true.

That is not what happens to food. Well, some stuff we eat is not nutritious. Dietary fiber can still be delicious. And that's part of our food that we can't digest. And it does come out along with the rest. But food is mostly caloric stuff that helps you think and get real buff. Mostly, that doesn't get all the way through. It's absorbed and it becomes new you. Your eyes and your bones and your thoughts and your fears,

your biggest toenail and your cute little ears, it's metabolized into thoughts of your past. And the waste from that process, it turns out, is gas. And so, this is incredibly fun, the waste from your food comes out of your lungs. So if poop is not what becomes of your chow, then what is it, Sari? Please tell me right now. Wow. So I didn't even get to what poop is. You got stuck on carbon dioxide and then it was really... Well, the first thing, I wrote another poem poem at first and then i realized that it was wrong because it was about food food turning into poop but that's not really what happens your poop's a bunch of stuff if mostly it's not food for some animals they can they can continue to digest the stuff that's in the poop and indeed do some they

will re-eat it but you know it's it you know, it's a bad sign if your poop, for a human, contains a bunch of nutritious stuff. That means your digestive system is not working. In some way, like undigested food is food to something else. And the things that are in poop are partially food in that everything is once food, if you think about, like based on your poem. Sure, sure.

The food becomes you and then you become the poop, as in poop is cells that are left over from, like, the lining of your intestines, mucusy stuff, dead bacteria from your stomach, so, like, a lot of microbiome components, which I guess that is the least you part of your poop. But they still eat the food. But it's wild how much of your poop is just living organisms that aren't you. But at what point does it enter that and start becoming poop? All throughout. Yeah.

All throughout. So in your esophagus, your digestion starts in your mouth. You got bacteria in your mouth. You have saliva, mucusy kind of stuff. And so as soon as you start mushing that into the points, as part of digestion, different waste products get injected. And so like somewhere in your intestines, those epithelial cells shed. And then that just becomes like part of the poop ball, kind of like a Katamari in that game, Katamari Damacy, where you like roll it. It rolls up more and more.

Yeah, the poop is going through and it kind of sloughs off cells and gathers them up into the poop ball. Some of your organs contribute, so like your liver and your gallbladder contribute bile and that contributes to poop. So any metabolic waste products

from the rest of your body get funneled into your intestines and get added to the poop wall that is accumulating. And the bacteria are growing the whole time and they get caught up in there, but they don't all come out. Some of them stay behind. And I guess they're growing. They're like eating the food, eating the nutritious stuff and growing. And then it's like 30% of the solid mass of a healthy poop is bacteria. I don't like this.

This is too complicated. It should just be food. I feel like we've sent you into an existential crisis. It's not existential. You just made it not fun anymore. It's all science-y now. Yeah. I mean, so there's also just like poops, whatever comes out the butt.

Does that make you feel better, Sam? Much better. What's diarrhea? What's going on there you're just not feeling very good it all comes out too fast water yeah it's usually that the whole thing is moving quickly um that's not the only thing that can cause diarrhea but but oftentimes it's like your body's like something's wrong whatever is in here we need to get it out quickly and that's what that's what happens is it just doesn't have enough time to absorb all the water. But there are other causes as well.

The definition, correct me if I'm wrong, Sari, is whatever comes out the butt. Or cloaca. Yes, thank you. Asterisk or cloaca. But yes, whatever comes out the butt. Because animals also, and that's where the idea of poop gets squishy or uncertain for some animals. Because an anemone or a jellyfish, they have one whole mouth slash butt. And so any indigestible food comes out the mouth. Or like owls, they poop and they have owl poop but the owl pellets which

are the indigestible fur bones other cred or whatever that you dissect in third grade science uh they vomit it out so that's not poop it looks like poop because it is indigestible material that made its way partially through the digestive system but it comes out well here's a question i i know what you're gonna ask i think you do just by your face sometimes i hate thinking about this but go go sometimes a person can get so impacted that uh poop will back up into their stomach and they will vomit it out. This is obviously a very serious health condition.

It's obviously also extremely gross. And in that case, it comes out the mouth, but it's poop. So it doesn't come out the butt. It doesn't come out the butt. I think once it has made its way, there must be a threshold. Much like your threshold of bald men, it has to make it like 90, 80% of the way through your digestive system.

Then no matter what hole it comes out of, it's poop. Once it's in the intestines, I would think, like past the stomach. Post-stomach stuff. Certainly large intestine. Sari, do you have anything else that you know about uh the etymology of poop i do uh i have two things that i know that i think are worth sharing so poop meaning excrement is a fairly recent word uh it's from the uh seven late 1700s ish and was started by children, which I think is very funny.

It's a word that kids started saying because it sounded funny and it's probably another one of those imitative origins. And so you do a little poop and it means like a fart or a poop, like any sort of excrement. Anything that comes out of the butt is a poop.

Right. We forgot about farts when we were talking about anything that comes out of the butt. Any solid or liquid thing that comes out of the butt is a poop. Right. We forgot about farts when we were talking about anything that comes out of the butt. Any solid or liquid thing that comes out of the butt is poop. Farts used to be poop.

Like break, like fart, the word poop used to mean fart or like gas or solid or liquid, whatever came out. That's great. That's just the noise

your butt makes when it comes out. It makes a poop. I want a list of words that kids made up. That sounds like a good one. I don't know if there's any others besides poop. I'm sure there are. I want to know them. Anyway. Yeah. So that's great. I love that. And it also comes from similar words as to make a short blast on a horn. So like a toot and a poop. I think we're in the same range of linguistics.

But the other thing that I learned, so I was like, oh, poop's recent. What did we call poop beforehand? Feces is what we called it beforehand. Oh, boring. Boring. Don't do that. Boring.

No, don't do that. But it is, feces is from Latin and it's a plural word from the word fex or fex which i thought is very weird uh f-a-e-x the plural is feces uh and it just means the sediment or the dregs and so it'd be like at the bottom of your wine glass you've got the feces and then for some reason you're like at the bottom of the human tummy and and butt you've got the dregs of the human system sure i can see that it's the stuff you don't want that's left over afterward it's almost like a polite way to say it and then all the kids thought of the nastier ways later that is always the way all right that means now that we're really informed that it's time to move on to the quiz portion of our show. Supposedly, nothing in this world is certain except death and taxes.

But also, there's poop. Not the most certain thing in the world, but still a constant that is with us from the time that we are born to the time that we die. And while poop does serve the very important purpose of allowing us to pass waste from our body, it's also a very versatile tool that can be used in a myriad of ways, even in the early moments of an animal's life. So I'm going to tell you three stories of babies and poop in the animal kingdom, but only one of them is going to be true. We're going to play a few games. Which one of them is the true poop fact? Story number one, babies don't always make the wisest choices.

For example, lobster larvae like to eat jellyfish, putting their unprotected insides at risk from the jellyfish's venomous stingers. So the larvae wrap their fecal pellets in a membrane that lets them absorb nutrients from their meals while preventing the stingers from poking their guts. So there's a special little poop packet for, uh, for hobsters, or it could be fact number two, figuring out the right diet for your newborn can be tricky. So for the small Tibetan animal known as plateau pikas, parents have to go through an extra hurdle to make sure their young ones are

well-fed. They have to go out and gather yak poop. Scientists have found that pika babies whose parents fed them yak poop were better able to digest grassy meals thanks to the microbes present in that yak poop. Or it could be fact number three. Both of those could have been lies. So young animals can be vulnerable to attack. So finding a way to protect them can be very important for parents. Armyworm moths keep their young safe in a protective nest made out of poop. Their poop contains a special protein that makes their larva smell like a poisonous berry after they hatch, which wards off hungry birds.

There are three facts. Our lobster larva wrap their poops to protect their intestines from jellyfish stingers. Pika parents feed their pika pups yak poop in order to help their digestive systems handle grassy meals. Or armyworm moths make protective poop nests so

their larva can smell fresh as a poisonous berry when they're born. These are really good lies. Yeah. I don't know what you're going to do, you guys. The last one is especially like that's a hell of a lie if that's a lie i'm most dubious about the third one because poop is kind of a constant in life but there are some creatures that don't poop they just

get constipated and then die before they have to worry about it okay so like you think some mites which are little arachnids and i know some mayflies live short time and then some moths like i think so a lot of moths never eat yeah they can't eat they don't have mouthpieces and they don't have they're just don't have mouths yeah but they have mouthpieces but they don't like they're not usable so basically they don't have mouths they have like they just don't eat they do one thing big big chunky plump breeding mechanism that's why that's a better way of what i was gonna say um so i don't think the third one's well i guess it would be very weird if a mouth moth pooped to form nests but i'm dubious about it because i think there are so many moths that don't are you pretty sure no moths do or you know some do i have no idea okay i only looked up the ones that didn't i'd assume lobster larvas swim around do they because how are they going to get jellyfish

otherwise right i don't know yeah i imagine they can swim i don't know what lobsters do i don't think i've ever seen a lobster or conceived of a lobster not in a fish tank i think i feel the same way but i think they just walk on the ground yeah but they got a little tail they can what if they swim elegantly through the water they can't swim lobster swimming is super cool and weird it's not it's like because they go backward so it's fairly kind of counterintuitive the hell how have i worked here for 10 years and i don't know that lobsters can swim they look very silly yeah they do go backward okay this is your next tiktok hank just show them backward they're so cool i'm so delighted okay so lobsters can swim that means baby lobsters can swim can swim for sure

they can probably catch up with a jellyfish they look faster than a jellyfish they have more presence of mind than a jellyfish too i think so they there he is let's go get him yeah and the pika one i know that animals feed their young to seed their gut microbiome so like koalas do they feed them like their own poop that's it right i think so yeah that sounds right to me too to like give them some of the digestive bacteria specifically that they need but i don't know why pica would yeah i don't know i guess yak bacteria probably super powered and the pica bacteria they're just like oh my tummy's my tummy's too little tummy i got to my young but maybe why wouldn't they just have this the bacteria if they ate the yak poop too like yeah

that's true little sherlock holmes logic for you we We've Sherlocked our way to lobsters, and I think it's lobsters, and I'm going to say it before. I'm going to lock in the lobsters, too. I think we're right. You're both locking in on lobsters? Yeah. Well, we're starting out with a sweep. You've both got it. Look at that teamwork.

We're so smart. Lobster larvae, which are super cute. So there's a lobster called Phyllosoma. Probably as good as I'm going to do. They're only a few centimeters long and they float around in the ocean. And they also will attach themselves to jellyfish. So they are much smaller than a jellyfish, but they'll latch on. And the jellyfish help them get around, find a different place to be.

They also are a convenient meal. So they like to eat their tentacles specifically. And scientists at Hiroshima University wondered how the lobster larva were able to eat those tentacles without dying from all that venom, as parts of the gut should be vulnerable to those stingers. And the lobster larva died if they were directly injected with the venom. So the scientists knew it wasn't that they were just immune to it. There had to be some kind of mechanism keeping them from getting stung. So they fed them a diet exclusively made up of sea nettle jellyfish and studied the poop. And they found that the fecal pellets were wrapped in a semi-permeable membrane that

allowed nutrients to pass through, but prevented the stingers from getting out. I just saw a picture of a baby lobster that made me tear up. So look up some pictures of baby lobsters. They're really cute. Look at baby poses on top of a 17 pound lobster for photo shoot. How do you feel about that? Wait, is this real? Yeah.

Which is cuter? The baby lobster. This one's gruesome. I guess this lobster is about to be boiled, probably. All right. So congrats to you both. There were nuggets of truth in the other ones. It is true that animals will eat each other's poop for microbiome reasons.

Baby elephants and hippos eat the feces of their moms. But the plateau pika does eat yak poop. This behavior, however, is not restricted to the young. It just appears to be a survival strategy during the winter and might explain why the pika likes to live in the same areas as the yak, even though they compete for the same food. So it's it is a it's like a meal. They're like cute little dung beetles. Yak doesn't want it anymore i'll eat that i don't need that yeah absolutely um and army worm caterpillars uh do use their poop

uh but to trick plants army worm caterpillars like to eat corn plants but corn plants don't like getting eaten and they have some defenses against that uh including a chemical that repels the caterpillars however the corn plants can't multitask very well when it comes to attacks. So armyworm caterpillars divert the plant's attention by pooping. The caterpillar's poop contains a protein that makes the plant think

that it's being attacked by a fungus. And that causes the plant to defend against the possible fungal infection, leaving it wide open for caterpillar worm attack. That's crazy. Sneak attack. They tricked Korn. Poor Korn.

He's trying his best. Korn never did anything to anybody. I was like, please don't eat me. And then they were like, I'm going to shit on you instead. And eat you. All right.

We're going to take a break and then we'll be back for the fact off. Welcome back, everybody. It's time for the Fact Off. Our panelists have brought science facts to present to me in an attempt to blow my mind. And after they have presented their facts, I will judge them and award Hank Bucks any way I see fit. To decide who goes first, I have a trivia question. In 2005, the Ig Nobel Prize in Fluid Dynamics was given to a team of researchers who published a paper in the journal Polar Biology titled, Pressures Produced When Penguins Poo, Calculations on Avian Defecation.

The Ig Nobel described their work as, quote, using basic principles of physics to calculate the pressure that builds up inside a penguin. a penguin. The scientists studied chinstrap and adele penguins calculating that a fully grown penguin generated about 60 kilopascals to push out materials with a similar viscosity to olive oil. That's a fun thought. They calculated

that number using three main parameters. One was, as they themselves described it, the shape, aperture, and height above the ground of the orificium venti, which I think is the hole. The second was the density

and viscosity of the material. And the third was the distance the poop travels before hitting the ground. How far did they estimate the poop traveled before hitting the ground? I know, we just did a sci-show about this. Yeah, we talked about these penguins that shoot their poop away from their nests.

Five, six feet. I'm like almost six feet. I'm going to say 15 feet. Two series. Two and a half. Three. Yeah, two and a half to three series. That's really far.

The answer is 40 centimeters. so that one goes to sam sometimes it's a wild answer so far away and then there he guesses a wild answer for those wondering about the aperture from which the poop was fired the maximum diameter was eight millimeters so that was some fun research who do you want to go first sam oh i guess i'll go first diarrhea one of the clearest ways your body lets you know that something ain't right and that extends from you being sad and sweaty on your toilet after eating something that doesn't agree with you, all the way to entire communities suffering from diseases like cholera that impact the gastrointestinal system. But diarrhea is also a pretty personal affair, and people tend to keep it to themselves, which can

make it really difficult to tell when more people than usual are getting diarrhea, which can make it hard to notice quickly when there are outbreaks of diseases like cholera. But a team of scientists are hard at work on a solution to that problem. And part of that solution involves making artificial intelligence listen to a lot of people taking a shit. That's probably the best way to do it, right?

That's gotta be the best way to do it. Because otherwise it's just like knocking on people's doors and being like, I'd like you to share your poop details with me how's it been lately that can't be the solution perfectly normal that's what I would always say no matter what

so this team based out of Georgia Tech had initially set out to research if the sounds of farts and urination can be used to identify whether a patient had cancer so the line of thinking is that when people fart and pee, they do so out of tubes that are generally pretty uniform across all of humanity. So if it sounds weird when you fart and pee, you might have an abnormality in your rectum or urethra, which could make the shape of it different and point to a larger problem

like cancer. But they also came to the conclusion during this research that listening to the sounds of pooping and peeing tended to be just as effective as looking at video and more reliable than self-reporting, not to mention less unpleasant for everybody involved. So they also figured out that peeing, farting, solid pooping, and diarrhea all sound very different. Different enough that they could train an AI. What we have discovered, I wanted to read that line in the paper. different enough that they can train in AI.

What we have discovered, I wanted to read that line in the paper. What we have discovered is that peeing, pooping, farting, and diarrhea all sound very different. Yeah, yeah, I know. If you're the first person writing it in a paper, then you're the one who discovered it, you know? It's a new game. Pee, poop, fart, or diarrhea.

You listen to it, and then you click. I can't believe that a computer could tell the difference between peeing and farting two very different noises so the sounds are different enough that they could train an ai to listen to bathroom sounds and identify what was going on in there i assume that they figured an ai would be quicker and more efficient than a human but i also have to believe on some level that they were just sick of listening to pooping noises. So the researchers pulled as many and this is a weird sentence, publicly available video and audio clips of people going to the bathroom as they could find.

Wonder what APIs they used where they found all that good video data p and poop well okay so they fed all they started feeding all those videos to an algorithm and once the program had all that information it was introduced to a very special machine called the synthetic human acoustic reproduction testing machine, a.k.a. the Shart. So, the Shart... Oh, my God! Sarah, you're screwed!

You've got nothing! I thought mine was pretty good, but Sam just keeps hitting it one after another. So, the Shart is a series of tubes and soda bottles assembled for one purpose, to replicate the sound of humans pooping and peeing in all kinds of different ways. It can poop, it can pee, it can diarrhea. And when the AI listened to it do all these things, it could identify the type of excretion event that the shark was replicating with 98% accuracy.

So using this near-perfect poop-identifying artificial intelligence, the team hopes to build simple devices that can be installed in public toilets in communities at risk of cholera outbreaks to help them identify the outbreaks early. And now,

in honor of this fact, I've prepared a game called What the Shit, where we'll listen to pooping sounds and decide if they're diarrhea or not. No, I'm just kidding.

We're not going to. Okay. Oh, God. I believed you. We're very old bathrooms, so we can use them in the video. I've been prepping for this for a while. This is great. It's like, the thing is, this is great.

It's like a totally good thing to do. I don't know about the necessity of building the shart. That seems like. That seemed weird to me, too. I don't know about the necessity of building the shart. That seems like... That seemed weird to me too. I don't know why they wanted to do that. It seems like a lot of work to get diarrhea noises when those are available. I almost feel a little disappointed that it can only tell the difference between a poop

and a diarrhea 98% of the time. They've never had farts or diarrhea, so they don't even know what it's like. Sometimes I feel like the people don't even know what it's like and sometimes i feel like the people don't even know it's probably like a mysterious one that like switches between that's true i guess sometimes that's a good point you're like that's what i was doing down there wow is that what you mean yeah okay yes without so much personal inflection in there but exactly that sam where i was like I don't know what just happened.

And then you turn around and you're like, well. You're like, oh. That's a different texture than I expected. That's a good point. Sari, what do you have for me? Okay. Well, there are a couple anecdotes floating around in popular culture about a human fashioning a tool out of their frozen poop as a solution in a cold, desperate situation. I have recently heard about one of these.

Yeah, I can find a good fact too. It's no chart, but I'm pretty good at this podcast. So maybe the fact you heard was there's a Danish author who explored the Arctic and claimed to forge some type of chisel to free himself from a makeshift snow shelter that got frozen in an ice storm or avalanche. And there's a story about an Inuit man's grandfather who, in a winter storm, made a knife out of his poop, killed and skinned a dog to make a sled that could be harnessed to another dog and then traveled away. make a sled that could be harnessed to another dog and then traveled away. And to be fair, Wade Davis, who is the anthropologist who first recorded the Inuit man story, has said that it could have been a, quote, classic case of local people having some fun with a visiting tourist slash anthropologist. But as with many fun or weird anecdotes, the story has taken on a life

of its own. So much so that in October 2019, a team of experimental archaeologists published a paper in which they tried to create and test their own frozen poop knife. They regularly try to reproduce other human-made tools and tech, so why not this one? Sure. So the lead researcher, Matin I. Aaron, ate an Arctic-like diet that was high in proteins and fatty acids for eight days and started collecting and freezing his own poop around day four. He and his team formed knives using molds or shaping them by hand, storing the poop knives at negative 20 degrees Celsius, sharpening the edges with a metal file and then blast chilling them in negative 50 degrees Celsius dry ice right before the experiment.

And to test whether these poop knives could cut refrigerated meat, they tried them out on various cuts of pork, pig hide, muscle, and tendons. I will quote the paper directly for the results because this one's also a great read. Instead of slicing through it, the knife edge simply melted upon

contact leaving streaks of fecal matter ah that's not better it's good uh and so they acknowledge that this is a silly study but generally conclude that we should be dubious or think carefully about poop knife anecdotes or any sort of pop science things but that's not the end of the story wade davis that anthropologist that i mentioned at the beginning interestingly enough posted anecdotes or any sort of pop science things. But that's not the end of the story. Wade Davis, that anthropologist that I mentioned at the beginning, interestingly enough, posted a response article also in October 2019. And in my opinion, respectfully questioned why this research team went as far as to create poop knives in negative 20 and negative 50 degrees Celsius conditions, but didn't test the anecdote on

dog hide muscle and tendon per the story because it's very different from pig and so in the grand scheme of things you can apply a pair of experimental science to anything but there are a ton of considerations even when you're making knives from your own poop yeah i mean hey dogs can donate their bodies to science right you? You just ask. And they have one of those little pads where they put their foot down and they say, yes, mama, science, my dead body, science, yes. Poop. Knife. Poop. Knife.

Knife. Bye-bye. Bye-bye. bye-bye so that's uh and and probably the same situation with using like the poop chisel to get out of a i mean maybe not it seems like it's anything hard like it seems like the problem is that the poop knife was melting so you need to make sure things aren't too too warm and that wouldn't be the case for chiseling out of a of a ice shelter so maybe that's real yeah we don't know until you make a poop knife and then go to the frigid arctic and then try it out there so lots of experimentation still to be done if you want to experiment on

your poop and if you do we're on twitter at scishowents. We just hit 10,000 followers. Now, I think that Sam has to come out as a winner there. There was just too much. There was too much. And also, I hope that it results in better public health for our world. Now it's time to ask the science couch. We've got a listener question for our couch of finely honed scientific minds. Iliant J. Pinchay on YouTube asks, why do lots of people get diarrhea or extra stinky poops while on their period?

I know that this is a thing, and that is as far as my knowledge goes. Usually I can bullshit something, but, you know, hormones. As a certified guy with a wife i do know as well this is true that's as far as i can go yeah oh well as a person with a uterus i can also guarantee it's bad folks everything about periods are bad i hate them um so hormones is correct and i can just specify the types of hormones so that everyone can know about this thing especially people without wives or uteruses i've never heard of this before and now get to know the the horrors of period poops. So menstrual cycles are regulated by hormone levels that change throughout them. And basically, the general cycle is that you build up uterine lining, you ovulate, which is you release an egg, your body's all prepped to be pregnant if you want it.

And then if there's no fertilization of that egg then your body's like well screw that i'm gonna get rid of it all uh and there are hormones that control all different parts of this cycle um and different predictable phases everyone's is a little bit different it's also not something that's super rigorously studied because scientists are scared of uteruses or something like that. I don't know. Deemed them less important to study. And so there are two main things that can happen to your poop across this cycle. The first thing is that after ovulation, you get increased amounts of progesterone and estrogen.

And these hormones, in addition to like prepping your body to be pregnant, if that's a thing, it also has been linked to increased constipation during the menstrual cycles luteal phase. So right before your period, as you're building up to the premenstrual time, you're getting really constipated because of hormone contributions to it. When it comes time to shed the uterine lining, there is a group of lipids. So those are like the fatty acid compounds that act kind of like hormones. So they're not quite hormones, but they signal to cells. They're called prostaglandins. And your body makes them for lots of different things, like sites of healing if you get scratched and scraped inflammation. But it also, when it comes to menstrual stuff,

it helps signal to the smooth muscle around your vaginal canal and uterus to start contracting to shed all that built-up skin. And so the prostaglandins trigger smooth muscle contractions in the downstairs area. And there's also smooth muscle contractions in the downstairs area and there's also smooth muscle around your uh large intestine intestines in general which is close by which is nearby it's like close enough by this is wild yeah and so when when you got stuff signaling in that general abdomen area to eject your uterine lining you also get signaling to eject whatever is in your bowels at the same time the stinkiness it's a

mystery people say that it might have to do with a variation of your diet changes. So the hormone cycles of period may mean that you eat different things than you normally would right beforehand because you get cravings. But that is the part that I think is most mysterious. I could not find any literature on fart or poop smells with periods yeah and so that's not taking lining up for that one but we could get an ai on you gotta get a good we gotta get the ai not just listening but also smelling smelling i think there's there's actually not a lot i mean i this is a very common sort of line of questioning for you know children and everyone else that does not overlap a lot with the line of questioning that science scientists tend to do uh so there's just not a

lot that we know about fart smell which seems like a real miss it's one step away from all this like microbiome research that everyone's into right now it seems seems like it would be useful. Yeah, what is the composition to gotta get an AI nose in there. Yeah, you gotta get those health influencers talking about fart smells and how important they are. And then the research will begin. So if you want to ask the science couch your question, follow us on Twitter at SciShow Tangents

where we'll tweet out the topics for upcoming episodes every week. Or you can join the SciShow Tangents Patreon and ask us on our Discord. Thank you to Brian Henricks on YouTube, Ariel the biologist on Discord, and everybody else who asked us your questions for this episode. If you like this show and you want to help us out, it's very easy to do that. First, you can go to patreon.com slash SciShow Tangents. You can become a patron and get access to things like our newsletter, bonus episodes,

which are very fun and always a little bit weirder than regular Tangents. Special thanks to patrons John Pollock and Les Aker. Second, you can leave us a review wherever you listen. That's super helpful and it helps us know what you like about the show. And finally, if you want to show your love for SciShow Tangents,

just tell people about us. Thank you for joining us. I've been Hank Green. I've been Sari Reilly. And I've been Sam Schultz. SciShow Tangents is created by all of us and produced by Sam Schultz. Our associate producer is Faith Schmidt. Our editor is Seth Glicksman.

Our story editor is Alex Billow. Our social media organizer is Julia Buzz Bazaio. Our editorial assistant is Debuki Chakrabarty. Our sound design is by Joseph Tuna-Medish. Our executive producers are Caitlin Hoffmeister and me, Hank Green. And we couldn't make any of this, of course, without our patrons on Patreon. Thank you. And remember, the mind is not a vessel to be filled, but a fire to be lighted. But one more thing.

The northern curly-tailed lizard eats almost anything, from insects and smaller reptiles to french fries and cheese scraps. So they're known to have some pretty gnarly poops. But when a University of Florida PhD student performed a CT scan on a lizard with a really big tummy, they were in for a record-breaking surprise. They found a fecal bolus, aka a big poop, that comprised 80% of its body mass but wasn't being digested, leaving the lizard to starve with its other organs atrophying. The poop was made of congealed pizza grease, sand, insects, and an annelite lizard all clumped together in a mass that couldn't fit out of its cloaca.

So unfortunately, the story doesn't have a happy ending. They euthanized this lizard to put it out of its constipation-induced suffering. They couldn't cut it out of him? I don't know that we have a good system for stitching a lizard back up. Or for surgery on a lizard. Get him in the ER right now. Help him out. Stat!