SciShow Tangents - Agriculture

Episode Date: April 23, 2019

A bunch of things are considered agricultural science, from planting crops and raising sheep for wool to food safety and developing fertilizers. This week, we’re skimming the surface of agriculture, with a little detour into animals that sort of farm too. What accidental evolutionary pressures turned weeds into popular crops? Why are seed vaults so important to humanity? And what made Big Mike  basically go extinct, and are we worried about it happening with other crops? (Big Mike is a banana, by the way.)Want to know more about our topics? Check out these links:[Truth or Fail]https://india.mongabay.com/2018/10/farmer-termites-bury-invaders-alive-to-protect-fungus-farms/https://link.springer.com/article/10.1007%2Fs10886-017-0902-4https://link.springer.com/article/10.1007/s00040-010-0092-3https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0156847[Fact Off]Vavilovian mimicry:https://www.cambridge.org/core/journals/weed-science/article/vavilovian-mimicry-nikolai-vavilov-and-his-littleknown-impact-on-weed-science/1B0263622E208DA4548BF0BCB918F255https://link.springer.com/article/10.1007/BF02858881http://labs.eeb.utoronto.ca/barrett/pdf/schb_54.pdfhttps://onlinelibrary.wiley.com/doi/full/10.1111/j.1752-4571.2010.00140.xLeningrad seed vault:[Ask the Science Couch]Bananas:https://www.theguardian.com/commentisfree/2016/oct/25/banana-farming-danger-cavendish-crop-geneticshttps://www.theguardian.com/global-development/2018/jun/18/scientists-scramble-to-stop-bananas-being-killed-offhttp://blogs.discovermagazine.com/crux/2017/12/27/banana-fungus-panama-disease/#.XIgdQFNKhxwhttps://www.apsnet.org/about/newsroom/releases/Pages/03Banana.aspxhttps://fusariumwilt.org/index.php/en/about-fusarium-wilt/https://www.bbc.com/news/science-environment-44712034[Butt One More Thing]Night soil: https://www.npr.org/sections/thesalt/2013/05/07/182010827/is-it-safe-to-use-compost-made-from-treated-human-waste

Hello and welcome to SciShow Tangents, the lightly competitive knowledge showcase starring some of the geniuses that make the YouTube series SciShow happen. This week joining me as always are Stephen Jay. Hey-o. What's your tagline? I'll give you three sheep for one brick. Sam Schultz is also here. Yep.

Did you forget my name? Everything's fine. Oh, no. What's your tagline? It's a cage, Miss Miracle. And we've also got Sari Riley joining us. Hello. What's going on?

Oh, boy. I have such strong shoveling muscles. I don't know if this is seasonal or not. It doesn't matter. It's worth talking about no matter when this comes out

that it snowed so much this evening. It has snowed a lot. We have had an unusual amount of snow and an unusually cold winter. But it gets you in good shape. My biceps don't get sore

when I shovel anymore. It's great. Wow, you've been doing it for that long. Yeah, wow. This you in good shape. My biceps don't get sore when I shovel anymore. It's great. Wow. You've been doing it for that long. Yeah. Wow. This winter has been forever. So strong. So sad. What's your tagline? That. So strong, so sad. That's a great one. And I am Hank Green. It is a pleasure to be here. My tagline, platypus pants. This week and every week on SciShow Tangents, we get together to try to one-up ummies and delight each other with science facts. We're playing for glory, but we're also keeping score and awarding Hank bucks so you can know who the winner is. What's the point of doing anything if there's no winners?

We do everything we can to stay on topic here at Tangents, but judging by the name of the podcast, which is Tangents, we will not be great at that. So if the rest of the team deems a tangent unworthy, we'll force you to give up one of your Hank bucks. Now, as always, we're going to introduce

this week's topic with the traditional science poem from Stefan. The practice of farming cropped up all over the planet, allowing humans to build large settlements that they would inhabit.

And the population grew as we planted plants from across the gamut, grains, olives, apples, even pomegranate. Now we have to feed 7 billion humans, but for now we can manage. Though when it comes to the environment, the process sure can cause some damage. But we used to use mercury as a pesticide, and that can't be organic. Well, whether it's through gmos or other agriculture tech i think will rise to the challenge hopefully yeah not your best work not your palms for sure but

i think you get a hank fuck nonetheless they're so good and so scary yes uh pomegranates and also we may be destroying the planet by trying to live here. The topic is agriculture, which is something that we've been doing for a while now. I've heard 10,000 years for our sort of agricultural horizon, and it has certainly allowed us to do a great many things while still being able to eat sandwiches, which are great. I love them. But I am curious, Sari, if you can define our topic. Because it is a little bit wibbly. It's super broad.

Agriculture is so many things. Generally, it seems to be the things that humans do to the environment for plants or animals or other things that we consume or use resources from in some way so like so agriculture isn't just food like it's important to remember that like fabric is agriculture and like building materials wood is agriculture and paper is agriculture that actually did not occur to me the entire time i was researching this topic. Yeah. Fibers and everything like that. Yeah. Technically agriculture. But also, like, what about the microorganisms that help us make beer?

Those guys are kind of agricultured. Yeah. Like our fermenters. Yeast. Yeah. Is that agriculture? Maybe. That's livestock.

That's agriculture. Livestock is agriculture. It is? Yeah. I didn't know that. Livestock is agriculture. I should have looked up a definition of what agriculture is. Yeah.

And then falling under the umbrella of agricultural science is all the policy that's come up around it. So like food safety is all agricultural science. Right. And all the regulations that we have in place for farmers and other people who are consuming the food that gets produced. And before that was regulations, it was also like just shared knowledge. So like the shared knowledge we had around this stuff is also itself agriculture. Like the ideas we have about how to make food, how to keep plants happy, how to keep animals happy, and how to do it in a way that keeps the environment healthy and also doesn't hurt

us is all agriculture. Yeah. The tools we how to do it in a way that keeps the environment healthy and also doesn't hurt us is all agriculture yeah the tools we use to do it the tools we use to store everything i don't know like there's that big seed vault in norway yep small board yeah there's a few of them i was reading about them for some reason yeah where you i don't know contingency plans in case we cause a global catastrophe everyone happens and how do we maintain agriculture if that uh is the case everything's agriculture i mean kind of yeah it's a lot because it's it's all stuff that we rely on like it's oh yeah it's the relationship between humans and the planet and the resources we take and the resources that we're intentionally cultivating. Like all of humanity's greatest achievements, it's very inspiring and terrifying. I always like defining the things that are easy, like that I know what they are, is always way more illuminating than defining the things I don't know what they are.

Because I'm like, oh, geez. Oh, gosh. Yeah. A shovel. Is that agriculture? Does that count? So now that we're all defined up, Sari, it is your time to choose your fail. Where you got three science facts that we are going to attempt to tease out the true one among the two lies. If we can do that, we'll get a Hank Buck. But if you fool us, you get the Hank Buck. I'm curious to hear your three agriculture facts. So I have written down here,

agriculture can be so many things that I got intimidated and went away from humans to look at animals that sort of farm. Okay. went away from humans to look at animals that sort of farm okay it's called cultivation mutualism to try not to anthropomorphize even though a lot of the headlines say look at this animal that's growing and the first agriculture was done by ants yeah i saw that article too yeah but scientists like to call it cultivation mutualism so like one one organism is cultivating another so which of these relationships is real number one there are pangolins that basically farm ant colonies part of their stomach is muscular with keratinous spines and pebbles that can grind up food kind of of like a bird's gizzard. So they swallow certain plants and vomit up sweet nectar mush near ant colonies

before they dig them up and eat a bunch, and that counteracts the worker losses. Wow, so they're helping keep the ant's hill alive by puking up sugary plants on them. Yeah, which is ant food. Little for you, little for me. Yeah, like I'm going to eat some of you, but here's some food so that you can rebuild and I can come back

and eat more of you later. Number two, there are termites that grow fungus gardens on top of their poop inside their mounds. They can sniff out parasitic fungal weeds,

essentially, in their gardens and bury them in saliva dirt balls to destroy them and protect their good fungus and this relationship has been going on for so long that we don't think this kind of fungus grows outside termite mounds anymore oh i love that um we're number three there are lemmings that cultivate lichen which is an organism that's fungus plus algae when they find a big enough patch of lichen in the tundra environment they clear away snow and build a tunnel system nearby this helps the

lichen survive the winter by photosynthesizing because that's how they generate energy and then plus bacteria on the lemmings or in their saliva we're not sure where produce a chemical that protects against parasitic kinds of algae taking over in the lichen. Oh, that one sounded so real because of that last part where you're like, we think, and you don't know you think in a true-to-life tale. That's way too specific. So, got number one,

pangolins farm ant colonies puking up the sweetness for them. Come on, come on, get down with the sweetness. Termites grow fungus gardens on their poop and sniff out parasitic weeds. And lemmings that cultivate lichen and prevent algae parasites. I want it to be the termite one

because it's adorable that those mushrooms don't grow anywhere else. So I'm picking that one. That sounds pretty real. The thing about that one is that I feel like insects are more likely

to have evolved these things because they have had longer to do it almost. And like more stability in their environments. Because termites have been around a real long time. Yeah.

Lemmings don't know what the heck's going on. Yeah, they're brand new. Yeah. Okay. Well, it seems like Sam already heard you. I just wanted to read that one.

I'm going with my heart. The pangolins, they can't digest the plant material. Or they can't extract nutrients from it. Yeah. Okay. And they don't have teeth. And so their gizzard area works for multiple reasons. It works for grinding plants, but it also helps them grind up ants and, like, the exoskeletons of insects.

Do people have gizzards? No. Do mammals have gizzards? Apparently, a pangolin does. Pangolins are mammals. Okay. Or maybe it doesn't. Yeah.

I mean, I think that they do, because I think that they have to grind up the ants, because they definitely don't have teeth. I'm also leaning toward termites. Ooh. It's probably wrong. It's dangerous. I don't want to be tricked. I'm going to go with the pangolins. Okay.

You're going to go with the pangolins? Because it's like you do a little bit of work, then you puke it up for the ants. And they're like, all right, we'll let you eat some of us. I like it. It's a very good fact. I would go with the lemmings. Because it seems really real. But I feel like we always spread it out. And that's real, but I feel like we always spread it out and that's cheating.

And I don't want to spread it out, so I'm going to go with termites. It was termites. Answer! Oh, sorry. So, for the pangolins one, they do have a muscular weird stomach that has keratin spines and helps them grind up ants but no stones in there they do have stones in there too but they don't god they don't farm at all they don't have any sort of mutualistic relationship with the ants they eat they just like go dig them up you know like i don't need to take care of you yeah you'll be fine yeah so is it a gizzard or is it just a stomach that acts like a gizzard i think it's's like a chunk of their stomach that acts like a gizzard.

I couldn't find a diagram of their anatomy, but it sounded like it was a specific chamber in their digestive tract that was not quite there. Very cool. Lemons are mostly made up completely. Oh. Something about like the... completely. There is, leaf cutter ants carry a bacteria on their bodies that produces anti, I don't know, the article said antibiotics, but they said it protects against fungal parasites. So that's like a misnomer, bad naming, not an antibiotic, but they have some sort of antifungal agent. And so I knew that that existed, but I made up the lemmings thing.

They do eat lichen. That's it. But the termites is the real one. They farm fungus on their poop. Yeah. And the fungus only lives that one place, we think. Yes. It's called, I couldn't find a pronunciation, but termitomyces.

Oh. So it's named after its relationship with termites. Yeah. Basically. And it's named after its relationship yeah basically um and it's an obligate mutualism so this fungus grows perfectly in like the humid temperatures and the the certain carbon dioxide content within termite mounds scientists aren't entirely sure whether they are cultivating the fungus because what they ultimately want is to eat the fungus. So like that is the food source. And so the thing that they eat to poop to grow it is just, I don't know, a side effect.

It just happens to be whatever it is. Or if the fungus is specifically like the only way it can extract nutrients from the food that it eats are like a second round of nutrient extraction so they eat food once poop it out and then to sap every last bit of nutrition from that food right they have now developed this relationship with the fungus it's like external gut bacteria yeah except that they're fungus yep exactly and what's interesting is that because the termite mounds are so warm and poopy and great for fungus, there is another genus, I think, called Pseudozylaria fungus that is essentially like a weed in their gardens. And it grows faster and could easily take over the Termitomyces fungus. and could easily take over the termitomyces fungus but this one kind of like fungus farming termite has learned to sniff it out and they bury it in dirt they like form these dirt balls and are like

no and then like smother it essentially to kill off this bad fungus and when these researchers studied it in the lab it seems like it affects the growth of both because i don't know termites aren't careful like a human gardener and we can't anthropomorphize them and so they're just kind of like smothering everything in that general region but their crop fungus still flourishes while the other one dies and reacts badly to this so it's just like a very cute small garden yeah that they know how to protect and that they are are curating in some way to grow the food i like the phrase warm poopy and great for fungus termite mound airbnb ad

yeah and it's been going on for like tens of millions of years. I think we found fossilized fungus gardens from 25 million years ago. Next up, we have the fact-off. But first,

a word from our sponsors. All right. We have returned Hank Buck totals. It is a four-way tie. Oh, thanks. Everybody's got one. But Sam and I have a chance to become a winner here. Or a tie. Or a tie.

It's up to you two and the Fact Off, in which Sam and I have brought science facts to present to Stefan and Sari in an attempt to blow their minds. And you guys get to award your Hank Buck to the fact that you like the most. And the person who's going to go first is the person who most recently ate a food any food yeah agriculturally produced um i mean i ate lunch around lunchtime i had some nuts at one oh i think you ate before me probably yeah you had a later lunch i had a noon noon lunch. Oh, that I ate after you. Well, you know.

What do words mean, I say? So I should go first, because I had nuts. Yeah, you always make me go first. Agriculturally produced nuts. At one. So here is my fact, everyone. We all know that mimicry is a thing that happens uh in evolution um and mimicry basically the sort of quintessential example is there uh is an animal that's dangerous

or poisonous and you want to try and look like that animal even if you yourself aren't dangerous or poisonous because predators will avoid you if you look like that dangerous slash poisonous animal. So that's like the form of mimicry that we're most familiar with. But there are many other types of mimicry. There's one called Vavilovian mimicry. I'm going to say it again. Vavilovian mimicry is probably how it's pronounced. It's also called crop mimicry. I'm going to say it again. Vavilovian mimicry is probably how it's pronounced. It's also called crop mimicry.

And this is when a non-crop plant, a weed, in this situation, so a plant that farmers don't want to grow, evolves to look or act like a crop plant so that they don't get weeded out or that they

like, so that farmers don't pull it up when they are weeding because it's like, is that wheat or is it something else? I can't tell. I'm just going to leave it. Or they end up being selected by the machines that are pulling up the crops. And so the seeds are the exact same size. And so they get pulled out and then planted in next year's crop because the seeds look exactly the same. So this is crop mimicry. It's happened a bunch of times. And this is cool on its own. But there are also several plants that you have heard of that evolved this way, starting off as weed plants that were not useful to humans because, like, maybe their seeds dropped off too early and we couldn't collect them easily. Or they didn't seed at all at the right time.

Or their seeds were too small to be useful. But by mimicking wheat, two different plants, rye and oats, managed to not just look like wheat but to be the thing that we ended up planting they managed to sneak their way into becoming our agricultural crops what the heck that's so cool it's super cool vavilov and it's uh named after a vivilov who was a soviet crop scientist who i think was really bad at his job. Oh, excuse me. You're going to learn a lot more about him in a minute. Really?

That's very weird. And they faked it till they made it. They faked it till they made it. That's so beautiful. Yeah. That's the only acceptable use of that phrase now. To be applied to rye and oats. Right. One of the big things that both rye and oats did is they strengthened their connection with the stalk so that the seeds didn't fall off. Because when you're harvesting wheat, you don't want to pick up a bunch of wheat seeds off the ground. You want to grab the wheat head and then like strip off all the chaff and be like, boom, all of the seeds were in one place for me. So they strengthened that connection, and both of them did that.

Rye did a separate thing where rye actually was a perennial, so it didn't seed at the time when we wanted it to seed, whereas wheat is an annual, it would grow once, drop its seeds, grow again, drop its seeds. And rye actually had to evolve to become an annual so that it would seed every year in order to become a useful crop for us. And that was part of its Vavilovian mimicry was changing the way it seeded so that it would be picked up by our farmers and replanted. Is that like a mutation that happens to plants like perennials accidentally become yeah so it was a rare mutation that some uh rye crops would seed at the end of every season and that ended up being what we

selected for or what like what we selected for but not intentionally yeah what ended up happening is both with rye and oats so they're not better than wheat but they grow in places wheat won't grow. So we ended up being like, okay, well, we're going to still plant wheat because it actually gets more like food per acre. But in like higher mountains where there's rockier soils or there's not as much water, rye will grow there. And so we can grow on land where we didn't used to be able to grow. Makes a hell of a bread, too. Wow. I cannot believe I didn't know this about these greens.

This is like. Yeah, I'm into it. Wow. Yeah. All right, Sam. Hey, how'd you say that guy's name? Vavilov. Vavilov.

That's not how I would have said it. But you're probably more right than me. At the top of the show, we talked about seed seed vaults which are basically like banks that collect seeds and seal them up just in case like a plant goes extinct or the world is destroyed

in a nuclear cataclysm or something. And the people who do that usually who work in these seed vaults usually take it very seriously

and they only open it under certain circumstances but the employees of the world's very first global seed bank went the extra mile. So in the 1930s Russian biologist Nikolai Vavilov started storing seed samples he had collected from all around the world

in a lab near St. Petersburg, which at the time was called Leningrad. His self-proclaimed mission was to protect the future from hunger and starvation. So then jump forward to 1941. Vavilov was thrown in jail for criticizing a guy that Stalin thought was really good at growing crops. Oh, right. So Vavilov was the good guy. Yeah, there was another guy who was not good. Or Vavilov or whatever.

Yeah. And Vavilov was like, you're not right. And then Stalin was like, get in jail. And he starved to death in jail. A lot of people were starving to death in Russia at that time of history. But his seed bank continued. And by 1941, it had like 400,000 samples of seeds. But also in 1941, there was World War II happening.

And the German and Finnish armies were blockading and bombing Leningrad at the time. So the government removed a bunch of art and culturally important things from the city, but they didn't bother to move the seed bank. So a bunch of the researchers decided to stay, put the seeds in boxes, brought them into the basement, and guarded them. So they did 24-hour guard rotations.

They would kill rats with pointy sticks. They would keep fires going for the seeds that needed higher temperatures. They snuck out plant seeds that were going to rot and planted them just as like a last-ditch effort to keep them going. And they would hire people to smuggle seeds out of town. And then as the months wore on and the seeds kept going, they ran out of food and they had to work in teams so that one of them wouldn't go like, I'm just going to eat all these seeds. Yeah, because the seeds are food. They're like wheat seeds.

So they kept each other from eating the seeds. Oh my god. The siege ended after 28 months, so in 1944, and nine of the people died from starvation, but they protected the seeds for the most part. And one of them was quoted as saying, saving those seeds for future generations and helping the world recover after war

was more important than a single person's comfort. Or life. Yeah. Also, comfort. They must have agreed. Starving to death is not a matter of comfort, but it is beautiful. They did it, though. John did an Anthropocene Reviewed episode on the seed vaults of Leningrad, and it made me cry a lot. Well, no.

I have to listen to it. Did they end up using the seeds afterwards? I think some of them still exist. I didn't quite trace what happened to all of them, but I know some of them were seized by the Nazis. The seeds were somehow. I don't know exactly what the thing about that was, but I think they shipped other samples off.

And I think they found, they had them smuggled out to somewhere in the mountains. And I think they found that cache of seeds too. So I think some of them are still around. I'm pretty sure they must be. These are both such good facts. Like both like very life changing facts. But also like the fact that we ended up talking about the same Russian agriculture guy.

Yeah. Not, we did not communicate about this beforehand. I wonder why he must, I wonder why it was named after him. Because I think he discovered it.

Oh, okay. I think he's the dude who came up with it. So here's the weird thing. I can't remember the other guy's name. So this Russian who believed that,

like, in order to make a crop, like, resistant to cold weather, you had to put it in cold weather and it would get stronger that was how it worked yeah the that idea was to stalin like very russian like this is how we become strong is by going through adversity and then vavilov was out there being like no there's like genetics and this is how it works.

But that idea had already started being promoted in Western Europe. And they were like, that is the tool of the bourgeoisie capitalists and you should go to jail and die. Yeah, it was Trofim Lysenko and he was the head of the Russian Institute of Genetics until 1965. Oh, and he did a real bad job. Yeah, are you talking about, like, Sankoism? I read about this, too. And it's bonkers. It's like, it's worse than pseudoscience.

Yeah, well, and he convinced Stalin every day that this was a real thing. And also, lots of people died just because like they did agriculture bad because they were following this wrong version of agriculture and it was like you guys could have had more food yeah and there was like the promise of an agricultural future to like okay if it's bad now then just like through generations of doing agriculture like this we're gonna have the strongest and best plants and so much food but of course that's not going to happen all those germans are going to have bad food yeah they aren't using lysenkoism they have lazy plants they're coddling their crops yeah all right you guys are going to have to give your points to someone i don't want to okay can i split it

you're gonna i don't think that's how it works. I'm throwing it in the garbage. No. Okay. I'm going to give mine to Hank. I'm sorry, Sam. They were both good. That's fine. It's really freaking cool.

I just had no idea that these grains came out through the sand. It makes perfect sense that it would happen. Yes. But I also did not know about it. I'll give mine to Sam to restore balance to the universe. That brings us to Ask the Science Couch. At Dragonlance447 asks, are bananas still in danger because of their homogeneity

or are people working on increasing their diversity? Yeah, so bananas are basically all clones of each other. And we once had a different kind of banana that went extinct because a fungus got really good at killing it. And there is concern that that will happen to the current banana, which is a great fruit that I love very much. There's other varieties of banana? There are other varieties of banana,

yes. But we eat only one kind. Like, any average American eats the same kind of banana. Yeah. But, Sari, you looked this up, actually. I was just guessing. I mean, you know, you got good banana knowledge good banana gut knowledge um that's all right the the bananas that we have now are called cavendish bananas those are the ones that are propagated and they are all how british that word is it's the cavendish it's like it's not the Cavendish. It's not from, like, Manchester. Like, what's happening?

Well, the previous banana that has gone extinct nearly, if not completely, is the Gros Michel. The Gros Michel. Which is very French. Which also is not where bananas are from. Yeah. They are also not from Cannes. All the articles that I read that referenced it also called it Big Mike, which seems like a very American way to say it. Like, I don't want to say Gros Michel.

I want to say Big Mike. I'm eating a Big Mike today. Can somebody get me a Big Mike? Oh, boy. Give me a brewski and a Big Mike. I like it. Oh boy. Give me a brewski and a big mic.

I like it. They are a monoculture and there have been a lot of articles, especially in the last 10 years, warning us that the next banana apocalypse is nigh. And from what I can tell, not enough agricultural scientists are behind that like they're clearly big threats and there are two main diseases that are affecting cavendish banana crops one of them is panama disease which is what wiped out the grow mish the grow michelle the grow michelle yes the grow michelle panama disease wiped that out it's a called Fusarium oxysporum, and there are different strains of it. So the strain that wiped out the previous banana, we thought Cavendish bananas. Just say Big Mike.

That's what I can do. Yeah, that's why. I'm an American who can't say anything besides Big Mike. Yeah, that's why I'm an American who can't say anything besides Big Mike. So the fungus that wiped out Big Mike is... No, no, it's going to take me seriously as a scientist. Was a strain that didn't affect Cavendish bananas. And so we were like, we found the banana that's resistant to this. And we thought we had solved the problem and we were scot-free.

But now other strains have popped up that can attack this monoculture. And specifically, it's like a wilting disease. So it blocks up the vessels that allow for the flow of water and nutrients. And that's why plants wilt and die. And that's why plants wilt and die. The other main concern is called black leaf streak disease or black sigatoka, which is caused by a fungus called Mycospherula figiensis, which affects the leaves and it like rots them and makes them have holes, which ruins the photosynthesis of the plants. And so both of these diseases have popped up and caused, I think, local devastation within Cavendish crops, but nothing that would make us think

that we'll go completely extinct because we're ready with fungicides. We don't have a great one-size-fits-all solution for this. Mostly it's like we are reacting to these problems as they pop up, and I think there are some scientists that are trying to genetically modify bananas to introduce genes that give them resistance. That seems like the ultimate solution. Like if we are going to keep having Cavendish bananas, it will be because of genetic modification. One of the things that you end up with is like

areas of soil that is infected with one or both of these fungi. And then you can't plant bananas there anymore. Like you just can't effectively apply fungicide to all of the soil. And then the idea of introducing diversity doesn't work because that's not how bananas work. If you crossbred a cavendish with another banana crop, it would be a completely useless banana. Bananas are like apples in that every honeycrisp apple you've ever had is a clone of every other honeycrisp apple. But the vast majority of apple trees come up with crap apples. Okay, so how did we let the grow, Michel? We weren't ready with this?

Yeah, it happened very fast, and it was in the soil. So the only reason Cavendish can grow is because it's resistant to the strain that killed the Gros Michel. Do you know when that was? I think it was the 60s, maybe, when we stopped having big mics. I want to read an article where they were just like, there isn't this kind of banana anymore. They do still grow some places. If you're in South America, you can find Gros Michel bananas. They just can't do them at mass scale.

Is that the issue with the other varieties of banana also? Is that it's harder to make them? Well, we have designed our entire banana infrastructure around the Cavendish. Like, the tree-to-table chain is on the side. And it is an efficient process to get a banana. Like, it's amazing. Like, at no point in the year is my grocery store not full of bananas, and that is true for everyone in America. Yeah.

Like, how is that possible? It's the most popular product at Walmart. They sell more bananas than anything else? Yeah. Because you can buy a bunch at a time. Okay, I can buy a bunch of toilet paper at a time, too. Yeah, but, like, how many rolls of toilet paper do you go through in a week?

Yeah, toilet paper doesn't rot. And the banana peel sort of doubles as toilet paper. Yeah, boom. Wow. Yeah, it's like a moisturized wipe. Yeah. Oh no.

If you want to ask the Science Couch, follow us on Twitter at SciShowTangents where we'll tweet out the topics for upcoming episodes every week. All right. So we have our final scores now.

Sari, you got one. Stefan, you got one. Sam and I tied! Thanks, Vavulove. If you like this show and you want to help us out, it's really easy to do that. You can leave us a review on iTunes or wherever you can leave reviews. That's helpful for us to know what you like about the show. You can also tweet us your favorite moment from this episode. And finally,

if you want to show your love, just tell people about us. Thank you for joining us this week. I have been Hank Green. I've been Stefan Chin. I've been Sam Schultz. I've been Sari Reilly. I mixed it up on them. SciShow Tangents is co-produced by Complexly and

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And remember, the mind is not a vessel to be filled, but a fire to be lighted. But one more thing. People have been using their own poop to fertilize fields for a long time. But I guess saying that your field is fertilized by human poop is probably not like good marketing so they the name for human-based fertilizer colloquially kind of is night soil and some people think that that comes from the way that it was collected where in the middle of the night people would go out and they'd find septic like pits of poop and outhouses and stuff and they'd steal the poop out of it put it on a wagon and bring it to the next town and sell the poop as fertilizer it's like grave robin but poop robin yeah