The Evolution of Colour Vision & Tetrachromacy

Can you hide your skeleton from a dog? Would you want to know the day you’ll die? Has evolution ever come close to producing a real fire breather? Michael and Hannah test a T-shirt with a secret only humans can see, leading them into the strange world of colour vision, from colourblindness and tetrachromacy, to the remarkable eyes of the mantis shrimp. They also ask whether DNA could become the ultimate hard drive, visit a data storage mountain in Pittsburgh and discover just how little space all of humanity’s writing might take up. Send your questions to [email protected] or find us at r/TheRestIsScience. ------------------- For more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit ⁠⁠https://cancerresearchuk.org/restisscience⁠⁠ Cancer Research UK is a registered charity in England and Wales (1089464), Scotland (SC041666), the Isle of Man (1103) and Jersey (247). A company limited by guarantee. Registered company in England and Wales (4325234) and the Isle of Man (5713F). Registered address: 2 Redman Place, London, E20 1JQ. ------------------- Find The Rest Is Science all over the internet by ⁠⁠clicking here.⁠⁠ ------------------- Video Producer: Adam Thornton + Oli Oakley + Jack Meek Animator: Sam Benson Video & Social: Bex Tyrrell Assistant Producer: Lucy Lipscombe Producer: Simona Rata Senior Producer: Lauren Armstrong-Carter Chief Digital Officer: Samuel Oakley Exec Producer: Neil Fearn Learn more about your ad choices. Visit podcastchoices.com/adchoices

• 0:00Speaker 00

  Welcome to Rest is Science. This is Field Notes.

• 0:03Speaker 01

  Oh, hi, Field Notes. I'm Michael.

• 0:05Speaker 00

  Oh, yeah. I mean, that bit's important.

• 0:08Speaker 01

  That's just classic Michael Hannah banter. Well, I'm here to talk about color vision, okay? Specifically, color vision in other animals. I spoke about this a while ago, but now it is real and it is on my body and it's protecting my bones. I'll show you.

• 0:29Speaker 00

  It's unfortunate. The editor's probably going to cut the bit where you, your top came up with your hoodie and we saw an almost nude Michael.

• 0:39Speaker 01

  Was that in frame?

• 0:40Speaker 00

  No, you're fine. You're safe. Don't worry.

• 0:43Speaker 01

  Did you not know that about me? In order to take my shirt off, I have to get completely nude first?

• 0:49Speaker 00

  I did think when the pants came off, I thought it was too much, but you know, you do you.

• 0:53Speaker 01

  It's just, it's just easier for me.

• 1:01Speaker 00

  This episode is brought to you by Cancer Research UK.

• 1:04Speaker 01

  Our bodies are incredible machines, worrying away, making more and more DNA to build the proteins that keep us alive.

• 1:12Speaker 00

  In fact, in the last minute, your body has made over 200 million new cells and enough DNA to stretch to the moon and back.

• 1:20Speaker 01

  To the moon and back. That's so much DNA that if you compared it to the size of the cell it fits into, that would be like squeezing the London Underground into a suitcase.

• 1:30Speaker 00

  By the age of 50, you have copied almost six trillion miles of DNA. But every time that your body copies DNA, it risks making mistakes. And over time, those mistakes can accumulate and that collection of errors can lead to cancer.

• 1:45Speaker 01

  But incredibly, Cancer Research UK scientists can spot these errors. And by finding them, they've helped double UK cancer survival over the last 50 years and are driving even more discoveries that could tackle over 200 types of cancer.

• 2:00Speaker 00

  For more information about Cancer Research UK, their research and breakthroughs, and how you can support them, visit cancerresearchuk.org/restiscience.

• 2:10Speaker 02

  Observe the North American dad. 50s, great polo collection. He enters his vehicle information on Carvana. An offer appears in minutes. Remarkable. He squints, reads it again, smiles and says, dang, that's a good offer. The highest form of approval. No haggling, no hassle, no one called him boss. He's still on the couch. Astonishing. Sell your car today on carvana.com. Pickup fees may apply.

• 2:42Speaker 03

  This episode is brought to you by Michelob Ultra. Good times mean competitions between you and your friends, like seeing who can throw some pigskin the farthest or rush the field the fastest. Winner gets an ultra because it's not just a superior light beer. It's also giving fans superior access to their favorite sporting events. Superior is worth playing for. Visit michelobultra.com/superioraccess to enter. Enjoy responsibly. Copyright 2026 Anheuser-Busch InBev Michelob Ultra Beer, St. Louis, Missouri.

• 3:18Speaker 01

  Anyway, this is the shirt and the shirt, you'll notice right away in white letters, it says, no bones in here. And the shirt itself is a kind of orangish red color. And so humans can read this, you know, no bones in here part, but so can dogs. Dog vision is different. Dog vision is just dichromatic. They only see two, two base colors, blue and yellow. All right. So they can see, you know, brightness and darkness, but they also can only see combos of blue and yellow. That's how the world is to them. And reds and greens look the same. They just kind of look perhaps like browns.

• 4:01Speaker 01

  We don't know what it is like to be a dog, but we do know that dogs cannot be trained to recognize the green and the red thing, or a green thing on a red thing. And so in green letters on this red shirt, we have written JK, I'm full of bones, actually. So only humans can see that actually I have a skeleton inside me. As far as dogs know, I don't have any bones in here.

• 4:30Speaker 00

  Yeah, I think this is an ingenious plan, Michael. I think, I think you've thought everything through. I think you have worked it all out. I can only see one tiny flaw.

• 4:39Speaker 01

  Yeah.

• 4:40Speaker 00

  Not sure dogs can read, but beyond that, great.

• 4:44Speaker 01

  Some of our, some of our testers brought that up. They said, well, I wore the shirt and I walked around bragging about my skeleton. And sure enough, no dogs tried to steal my bones. But it might not be because of the shirt, Michael. It might be because dogs can't read.

• 4:59Speaker 00

  You need a control group.

• 5:00Speaker 01

  And I think honestly, science will never know what really happened.

• 5:05Speaker 00

  Sure.

• 5:05Speaker 01

  But I'd rather be safe than sorry. We call this the dog safety shirt. It's part of this season's color vision box. We've got the, the color blindness tests all over it with different numbers. That's eight. If you can't read the eight on top of the box, then you might have color blindness of this type, or you might be a dog, in which case, paws off my bones, Fido. Now, I think, I think I may have mentioned the idea for this shirt already on the podcast, but now it is real and it's on my body, protecting my bones. There's more though, that I haven't shown and it's that we also made a whole sticker set. These are stickers that dogs cannot enjoy.

• 5:48Speaker 01

  So there are stickers of things that dogs would otherwise love, like cats, bones, fire hydrants, poop, squirrels, tennis balls. This, my, my daughter's already been playing with the stickers and she put a diamond ring sticker on top of this one and I can't get it off. But this is a dog sniffing another dog's butt.

• 6:07Speaker 00

  Great.

• 6:08Speaker 01

  But the colors that have been chosen so that to a dog, this heart shaped sticker, for example, that's red with a green bone on it is just going to look like a brown heart. They won't be able to see the detail of the bone written on it.

• 6:21Speaker 00

  Ah, sucker.

• 6:24Speaker 01

  As I show this off, it feels like we're just teasing dogs. But I think really we're teaching about the variety of visual experience amongst life forms on earth, which is a beautiful thing.

• 6:35Speaker 00

  Because there are other animals like the, is it the mantis shrimp? Which has, if, if humans have on average, three cones, dogs have two. The mantis shrimp has something like 19, if I remember rightly.

• 6:47Speaker 01

  Yeah.

• 6:48Speaker 00

  Like, we don't even know what it sees. It's like, the idea is that it's seeing perhaps some things that look translucent to us. It's managing to be able to distinguish between that and the sort of the water background that it's, that it's against. But I mean, the rainbow would be an entirely different experience if you're a mantis shrimp.

• 7:10Speaker 01

  I know.

• 7:11Speaker 00

  You come across the idea of a tetrachromat, by the way.

• 7:14Speaker 01

  Well, yes, there are humans who have, well, they have different color vision. They can see more colors than most people.

• 7:21Speaker 00

  Yeah. So, because it's all comes down to the X chromosome, which is where most of your cones are, certainly your red and green cones are, which is why being color blind is so much more common in men than it is in women.

• 7:35Speaker 01

  Right.

• 7:35Speaker 00

  In women, it's about one in every 200 women is colorblind. In men, it's more like 12% or something. But yeah, the reason is, is that if you end up with a defective X chromosome, effectively that, that your cones aren't working properly. In women, you get two rolls of the dice. You have two X chromosomes. If one isn't working, you have the other one. It's fine. But in men, you only get one shock because the Y chromosome doesn't have the right information on it.

• 8:00Speaker 01

  One strike and you're colorblind.

• 8:02Speaker 00

  One strike and you're colorblind. But because it is on the X chromosome, there is this idea that actually some women get two X chromosomes that are substantially different, that they end up with a fourth, effectively a fourth cone, tetrachromat.

• 8:17Speaker 01

  Now, I've heard about this, but what does that mean for their vision? What do they see that I don't?

• 8:22Speaker 00

  Well, so there's only been a really, really, really small number of women who have like been sort of identified and tested in a scientific way. But there are some, some people, some estimates say that actually maybe around 20% of women have this, but don't know that they have it. I mean, you can go your whole life being colorblind and not know that you are.

• 8:42Speaker 01

  Yeah.

• 8:42Speaker 00

  Right? Because you, this, it goes back to quality. You don't know how your experience relates to somebody else's. But if you are a woman who ends up arguing with other people about the color of things quite a lot, then it's possible that you're a tetrachromat. I think the idea is that you can distinguish between colors much more.

• 9:00Speaker 01

  Yes.

• 9:00Speaker 00

  Easily. So whereas you and I might be able to see a million colors, a tetrachromat might be able to see up to 100 million. So they can detect extremely subtle changes that you otherwise wouldn't be able to see. But we don't know really. It may be that they have entirely different colors altogether. There was, there was one woman who was a tetrachromat, sort of confirmed tetrachromat. And she said that when she walks along a pebbly beach. She doesn't understand how everyone just says, oh, it's all really grey. She didn't understand it because she was like, what are you talking about? This is like being at a jeweler's shop window. That you can see this like sparkling array of like myriad colours just shining back at you. What is everyone talking about? It's just really grey.

• 9:42Speaker 01

  Wow.

• 9:43Speaker 00

  Maybe in there, there is a pebble that says, hey, humans, suckers. And it's just put there by the mantis shrimp.

• 9:51Speaker 01

  Yeah, you trichromats will never appreciate me, the pebble. Uh, I, I love that. Just, it's such a good reminder that like, we see such a small portion of the world. And there's so much more there that other species see that even other individuals, humans can see.

• 10:08Speaker 00

  It's like the universe through a keyhole, you know?

• 10:10Speaker 01

  Exactly, exactly. Um, now here's, here's an ambiguous thing that we made. This is a coin. It's like a challenge coin sized coin. It's made of metal and you can flip this to never lose a coin toss. The way it works is that it says heads on one side and tails on the other. And it says, also says tails on the other side and heads on the other. It's an ambigram. So if I hold it like this, you can read the word heads and the editors can maybe outline the word heads there. But if I turn it upside down, you're still looking at the same side, but now it says tails.

• 10:47Speaker 00

  Nice.

• 10:48Speaker 01

  So you can flip this coin. The other person can call it in the air. You catch it and then you just show it to them, one side up or the other, to have it be heads or tails. So that you can always win or always lose. You know, it's up to you. You are in control. So I love this, a little bit of word art there. And then you see the coins around the edge. It's like different frames in the animation of a spinning coin. That's a zoetrope illusion. And so when you spin this coin, it's got a little divot in the middle. So you can spin it like a top.

• 11:19Speaker 00

  It looks like the coin is moving.

• 11:21Speaker 01

  But this coin can spin on its face like that, like a spinning top. And if you spin it and you look at it through your phone's, uh, camera, it can align with the frame rate. And the coins along the edge become an animated spinning coin. So this is a coin that spins a coin.

• 11:41Speaker 00

  I like that a lot. It's like the origin of cinema.

• 11:44Speaker 01

  But those, those are some of the, uh, the little inventions that we've got here.

• 11:49Speaker 00

  Here's what I want to know, right? When you come up with all these inventions, where does it start? Are you just like, like the, the idea of doing a shirt for colourblind dogs? Where do you, what, where's that come from?

• 12:02Speaker 01

  Well, we always wanted to do something around colour vision, like the, the, the whole, the whole box is always this team effort. And people will have an idea and then we all piggyback off of it and add to it. And so I think for this shirt, it began with, we want to do something with colour vision, maybe make goggles that allow you to see the world as a dog would, for example. And we still might do that. I'd love to make a book, actually, that comes with pages that you can look through to see the world as a cat, as a dog, as. We couldn't really do a mantis shrimp because you'd have to add colours. But maybe we'll figure out a way to do that. And then somehow it turned into a shirt that, oh, you know what?

• 12:45Speaker 01

  We had the idea to do a shirt that only your phone could see. Because you know, phones also see more colours than humans do. This is a great experiment to do at home. Just open up your camera app and point it at the front of a TV remote control and start pushing buttons. To the human eye, the light on the remote will just look blank. But through your camera, you'll see like a bluish light flickering because the camera receives the infrared radiation. And then it converts it into a colour humans can see on the screen. So you can see lights that you couldn't otherwise see through your phone. We wanted to make a shirt that worked in the same way, where until someone took a photo of it, they couldn't see what was on the shirt.

• 13:29Speaker 01

  And we couldn't actually get it to work with the, the like shirt printing technology that exists today. So we said, how about instead of phones, we focus on like an animal? How about dogs? They famously have limited colour vision compared to a human. And then I was the one who said, all right, here's the deal. It's going to be about bones. It's going to be about keeping you safe from a dog that wants your bones.

• 13:55Speaker 00

  I want to be in one of those meetings one day. Okay. I want to just be a far on the wall and enjoy it.

• 13:59Speaker 01

  You should come by, we just had one this morning. We're talking about, here's something that I, I'll have to send you a set. We're making a bunch of charms. They can be like keychains or just like charms for a charm bracelet that are based on SI standard units.

• 14:14Speaker 00

  Amazing.

• 14:15Speaker 01

  So we're giving you a pendulum that has a period of exactly like a tenth of a second. We're giving you a little, a little vial that contains exactly one kilocalorie of sugar. So you know what that looks like. It, a, a 10 gram weight and a, a square with a smaller square cut inside of it. That is exactly a square inch and a square centimetre. So you'll always have those to reference. And the plan is to do the full line of, of, of scientific unit charms. So we'll also have a light that produces either one lumen or how, you know, some, some.

• 14:53Speaker 00

  Exact measurement, yeah.

• 14:54Speaker 01

  Standard amount and what else is there? There's, oh, we'll give you an ohm resistor, um, keychain.

• 15:01Speaker 00

  I like this a lot. Will it also look good, Michael? Cause if it will, I'll wear it.

• 15:05Speaker 01

  They're made of steel, so they're, they're hard wearing and they, they're, they're stainless. So they're going to look beautiful. I think it's all really well designed. I'd show you photos, but that's all, um, confidential.

• 15:17Speaker 00

  But then you'd have to kill us. Then you'd have to kill us. Okay. Should we go to a break? Let's go to a break and when we come back, we'll be answering some of your questions.

• 15:25Speaker 01

  Perfect. See you then.

• 15:39Speaker 01

  This episode is brought to you by Cancer Research UK.

• 15:42Speaker 00

  Dentist appointments, MOTs, routine checkups help us to spot faults early before we need a root canal or breakdown at the side of the road. And cancer screening is the same idea.

• 15:53Speaker 01

  It's about aiming to spot cancer early before symptoms show and when treatment works best. The UK's breast, bowel and cervical cancer screening programs developed with Cancer Research UK save thousands of lives every year.

• 16:06Speaker 00

  Today, Cancer Research UK is backing innovations that could transform the future of screening. Picture a smart bra that could one day detect breast changes as it's worn, making screening more accessible.

• 16:19Speaker 01

  And AI trained on a database of over 10 million mammograms that helps doctors spot early signs of cancer.

• 16:26Speaker 00

  Research like this saves and improves lives.

• 16:28Speaker 01

  For more information about Cancer Research UK, their research and breakthroughs and how you can support them, visit cancerresearchuk.org/restisscience.

• 16:41Speaker 03

  This episode is brought to you by Michelob Ultra. Good times mean competitions between you and your friends, like seeing who can throw some pigskin the farthest or rush the field the fastest. Winner gets an ultra because it's not just a superior light beer. It's also giving fans superior access to their favourite sporting events. Superior is worth playing for. Visit michelobultra.com/superioraccess to enter. Enjoy responsibly. Copyright 2026 Anheuser Busch InBev Michelob Ultra Beer, St Louis, Missouri.

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• 17:47Speaker 01

  Okay, we are back to get into some of your questions. Remember, you can always submit your own by emailing them to us at [email protected]. Who knows? We might answer it right here on the show.

• 18:00Speaker 00

  We certainly might. You know what? While you were talking, I realised on the camera, my skin colour on my arm is exactly the same as the top that I'm wearing.

• 18:08Speaker 01

  It just looks like you're naked and sunburned.

• 18:10Speaker 00

  Naked and sunburn simultaneously.

• 18:12Speaker 01

  Very oddly, just on the shoulders.

• 18:14Speaker 00

  Exactly. Just this is a really glittery sunburn on this particular occasion. I need to note it, need to put on some fake tone if I'm wearing this top. You know how silly people are? If you don't say anything, they don't do anything. But if you say, guys, can you subscribe to our channel? Suddenly there's a massive influx of subscribers.

• 18:32Speaker 01

  Yeah. But that's because we are influencers, Hannah. If we tell people to subscribe, they do it, just like lemmings. Though lemmings don't actually exhibit lemming behaviour.

• 18:42Speaker 00

  No, that's true. They were driven, driven off the cliff by Disney producers, weren't they?

• 18:46Speaker 01

  Yeah. Anyway, the point is you should subscribe.

• 18:50Speaker 00

  Yeah, we hate saying that. We hate it because it's such a cliche, but unfortunately it works. So until every last one of you has done your duty and clicked that like and subscribe button, we will continue forcing that narrative down your throats.

• 19:05Speaker 01

  Just a brief object that has nothing to do with science at all. It is purely a plug for my best friend's book. So this, this woman, her name's Anna McCauley. She was my best friend through school. She was like the smartest kid in the school, so I felt very jealous and competitive with her. But we became very close friends. She was the best man at my wedding and she's written a book. And the book is a perfect marriage of like UK and America, just like us. It's called Abby Offsides. It's about an American who moves to England, starts working for a football team in Liverpool.

• 19:47Speaker 01

  And one of the characters in this book is based on me.

• 19:51Speaker 00

  Oh, but you're not saying which?

• 19:54Speaker 01

  What bigger honour could there be? I will say this. First of all, it's really, it's really a whole mind trip to read a book where you know there's a character based on you. It's, it changes the whole experience.

• 20:07Speaker 00

  Wait, is it, is it the dashingly good looking romantic lead?

• 20:11Speaker 01

  No, it isn't. However, she did write the character to be a much better friend to the main character in this book than I have ever been to her. It just, it actually almost made me feel bad. I'm like, oh gee. Also, the character that I'm based on has hair, like thick curly hair. And I'm like, okay.

• 20:30Speaker 00

  I mean, so do you if you do a hand, a handstand?

• 20:33Speaker 01

  That's true. Look at that upside down. I am a hair suit man.

• 20:39Speaker 01

  Anyway, Abbey Offside's not available here in New Zealand until October. So luckily I've got my advanced readers' copy. I read this, you know, a year ago.

• 20:47Speaker 00

  Okay, first question, let's get back to it, shall we?

• 20:49Speaker 01

  Okay, this comes from Dan Pelveco, who asks, I was curious to know if there is any way that we could use DNA and RNA to encode data like a hard drive? Is there anyone working on this?

• 21:03Speaker 00

  They're not just working on it, Dan. There, there's this whole race going on about it. So at the moment, I'm filming this series and one entire episode of the series is going to be about exactly this, exactly this question. So maybe what I should do is give you an update after we've gone off to film it. But yeah, this is like, we're at this point where semiconductors are reaching the kind of limits of Moore's law. It's unbelievably expensive to sort of transcribe data through this digital process, but it also just takes up physically a hell of a lot of space. So this time next week, I'm going to be in a mountain in Pittsburgh, which is, has been converted into a sort of safe data storage facility.

• 21:47Speaker 00

  The idea that, you know, if there's attacks or like fires or whatever it might be out, out there in the world, inside the mountain, the data will be safe and kind of can, can stay there for a really long time. But nothing has got anything on DNA, you know? Like, we've dug up woolly mammoths from the, from the permafrost in Siberia and they're, and managed to extract DNA from them that's been there for, you know, hundreds of thousands of years since before humans even existed. So this is like the only data source that we know for sure can be frozen in time and still be completely robust, you know, hundreds of thousands of years later. So there, there are people who are doing exactly this.

• 22:28Speaker 01

  Can I, can I ask a question?

• 22:29Speaker 00

  Please, go ahead.

• 22:30Speaker 01

  Okay, so when you and Dan talk about encoding information in or as DNA or RNA, what does that mean? Does that mean using their actual amino acids to, to store data using the, the?

• 22:46Speaker 00

  Yeah, A, T, G and C. Yeah, exactly.

• 22:49Speaker 01

  Okay, so, so, and that's what makes it DNA? Because obviously, if you encoded the text of Moby Dick, it wouldn't be DNA in the sense of like, oh, this is instructions for a, a living organism. It would, it would be using the language of DNA to form a long molecule that could be uh, read to give us back Moby Dick.

• 23:13Speaker 00

  Exactly right. So you couldn't sort of pop it into a cell or pop it into an egg and then suddenly Moby Dick be born.

• 23:21Speaker 01

  But you could pop it into a special reader.

• 23:24Speaker 00

  You could pop it into a special reader.

• 23:26Speaker 01

  Like, like an electronic computerized reader that would then be like, oh, I've analyzed this DNA molecule and here's, call me Ishmael, blah, blah, blah, blah, blah, blah.

• 23:34Speaker 00

  Exactly right. And if you think about it, this is one of the big advantages of it, apart from the fact that we know that it's sort of, that it's stable over incredibly long periods of time. We also, in, in DNA, you have four bases, right? A, T, C and G, whereas in binary, you've only got two, zero, one.

• 23:53Speaker 01

  Right.

• 23:54Speaker 00

  So it's also incredibly articulate, basically. You can, you can, it's extremely, extremely capable at compressing data really, really, really efficiently. And you are also, you're down at the size of molecules, right? So like one bit becomes miniscule.

• 24:10Speaker 01

  Even physically, it's very compressed because you're writing with molecules, large molecules, you know, but still molecules. And I know DNA can be lost pretty easily, but it's, it's, it's stable. Like you said, we can pull them out of woolly mammoths, but it, I guess it'd be more stable than like, okay, let's etch some little markings on a little wafer and hope it doesn't get scratched.

• 24:35Speaker 00

  Right.

• 24:35Speaker 01

  These molecules kind of preserve themselves by their own intermolecular forces.

• 24:41Speaker 00

  Quite literally, that, you're exactly right. I mean, if you think about, so I know we've spoken about this before, but the Human Genome Project, which was trying to take human DNA and then transcribe it into a string of those letters, A, T, C, G and so on. The Human Genome Project, I went to go and see it the other day as part of this, this program that I'm filming, at the Sangha Institute, they have it printed out as a series of books. I cannot tell you, like, it is absurd when you see just human DNA written out. It is, I, I like, I think it's 112 books and these books are meaty tombs. And you think, you think, oh, tome, sorry. I never get that word right.

• 25:23Speaker 01

  A meaty tomb? That sounds like a good movie.

• 25:28Speaker 00

  But you open them up expecting the writing to at least be big and it's not, it's miniscule. We are talking many, many, many, many, many thousands of pages across many hundreds of books, right? These, it's insane. And all of this is squished in and is copied in every single one of your cells, which are just, I mean, it's so tiny, right? Like, it's so articulate, DNA. There's this one estimate that basically if you took everything that humans have ever created and then you tried to re-encode it using DNA instead of, instead of sort of traditional methods, then they would basically fit in the back of two vans, the backs of two vans.

• 26:08Speaker 01

  Wow.

• 26:09Speaker 00

  Everything that's ever been written by humans. I mean, you go to like, you go to a, a data mountain, like the one in Pittsburgh, you put it in DNA and it's basically just like a little fridge, you know, like a little tiny little, little fridge, like you need nothing, it's almost nothing.

• 26:24Speaker 01

  Would this be smaller than electronic storage as it exists today? Like, how much physical space does a bit take up on a hard drive?

• 26:36Speaker 00

  Do you know what? I don't know.

• 26:37Speaker 01

  Yeah, I don't know either.

• 26:39Speaker 00

  Cause the problem is that one bit, I mean, the bits, you have to have like transistors, right? So like, even though transistors are small, we're still talking many orders of magnitude larger than DNA.

• 26:49Speaker 01

  Yeah. If I had an entire encyclopedia encoded into a strand of DNA, that DNA could be put into a little envelope kind of thing and I could inject it into my body and I could have the Encyclopedia Britannica in my body as a virus.

• 27:10Speaker 00

  You, you could. I mean, you would, you would really hope that there wasn't some sort of weird fluke that actually Ebola, it actually just so happens to be the exact same strand of Ebola.

• 27:22Speaker 01

  As my life story.

• 27:24Speaker 00

  As to my story was Moby Dick, right? You know, what a fluke that would be, that when you translate Moby Dick into amino acids, it just reads like Ebola. That would be bad. Anyway, the way that people do this, yeah. So, so the only problem about this is if you're accessing the data, so one of the real advantages of electronic storage is that you can read it and write it extremely quickly, right? And even when you have it, once you have it written, reading it again is, is really quick. Whereas if you're storing something as biological material, you're going to need to pass it back through a sort of electronic process in order to read it. So one of the ways that, that people do this is they go for like, quite a retro approach.

• 28:06Speaker 00

  They basically put it on a cassette tape, which I really like, this sort of like, you know, play out the DNA on this long strand and then have this tape sort of winding around. So that it then can be read through a machine really easily. They sort of coat it with this kind of crystal armor so that, just to stop the DNA bonds from, from breaking down. But yeah, there are, I mean, this is like, there's a big rush in this at the moment. This is, if you want data that will exist forever, then this is the way to go. Okay, next question. We've got one here from Simon Garner. He says, I was recently thinking about free will and decided if scientists discovered definitive evidence that it wasn't real, I wouldn't want to know.

• 28:51Speaker 00

  That made me want to ask you, as two people who've dedicated their lives to the acquiring and relaying of information, is there anything you wouldn't want to know? Even if we had the scientific knowledge and it was accessible to you, is there anything you would ask to not be told?

• 29:07Speaker 01

  Man, I find it really hard to answer. If, if we proved that everything was determined and everything could, given enough, you know, calculating could be predicted, it still wouldn't feel that way. I mean, we evolved to feel like causal agents. And so you could probably just never convince everybody that like, they had no free will or no choice in, in, in their decisions. But if I could, you know, know anything, what would I not want to know? It was hard. I, for me, I'd say probably I don't want to know the inner thoughts of everyone that knows me.

• 29:52Speaker 00

  Don't, don't you feel that it's been like being on the internet, sort of version of that, though?

• 29:57Speaker 01

  Yeah, we already have, we already have a version of that that does enough. But in terms of future events, I don't know. I feel like it would, it would be really hard to believe that if someone told me, okay, you're going to die in this way on this date. That I would, I would feel like, yeah, but I could avoid that now. And yet, in this thought experiment, determinism is the case. We don't have free will, and I couldn't escape it.

• 30:27Speaker 01

  That would be a real trip to find out, like, no, this is gonna happen in this way, no matter what you do. It'd be hard to accept.

• 30:35Speaker 00

  I'm the same, I'm the same as you. I think anything bad in the future, I'm okay with not knowing. I'm a, I don't wanna know when, when I'm gonna die. I don't wanna know when my family are gonna die. I don't wanna know if there's an apocalypse around the corner. I don't wanna know. I'm okay with it. I'd rather not know.

• 30:54Speaker 00

  I mean, I think the only reason why knowledge would be comforting would be if you, if the knowledge itself allowed you to change things.

• 31:04Speaker 01

  Yeah, in which case, we could already do that. Like, a, a person could pretend to be a mystic psychic and tell you what's going to happen in order to encourage you to act differently than you are now.

• 31:16Speaker 00

  But you're right, we already do know this, right? Don't smoke, don't drink too much, go for exercise. But we already know the thing, be kind to people, enjoy every day. Like, we already know all of the things.

• 31:27Speaker 01

  We already know that, but we don't really live like we know it. I think we may have mentioned this before, but it's a real trip to keep in mind that we have so many movies about time travel and going back in time to change the way things are. But we rarely in our lives sit and think about, like, whoa, I am already a time traveler. Meaning, right now will be the past at some point. And so the decisions I make now will radically alter the future. I already have the power to change what's going to happen. I'm gonna take advantage of it. Greg Egan wrote a short story called The Hundred Light Year Diary.

• 32:09Speaker 01

  That is about the discovery of a galaxy where I think time runs the other way. And they're able to align some telescopes in such a way that they can see the future.

• 32:22Speaker 00

  Right.

• 32:22Speaker 01

  Uh, I have, I'll have to reread this story to see how they do it. It's, it's incredibly hard sci-fi, really amazing. But then what happens is people wind up receiving, um, through these telescopes, diaries from their future selves. And their future selves will write about what happened each day. And the future selves have to make these decisions about how many details do I tell them? Like, you're going to be in a car accident. I'm gonna leave out how much it hurts. But I will let you know that it will happen. And then people live their whole lives knowing that, oh, yeah, tomorrow is the day that I'm gonna be in this car accident. And they all, the psychology behind how people live

• 33:00Speaker 01

  in a society where they already know the main landmarks of their life is really, it's, I mean, I almost don't have much to say about it because I need to just kind of lay in bed and think about it more. But it was a real incredible read because it worked. It worked.

• 33:16Speaker 00

  It's so interesting. What made me think about that as you were talking is that idea of talking to people about what lays ahead in their future and leaving out the most painful details deliberately. Because I actually think that we do that to each other.

• 33:31Speaker 01

  Yeah.

• 33:31Speaker 00

  You know, I was thinking here about, um, with childbirth, for example. I mean, people say, you know, childbirth's painful, blah, blah, blah, blah, blah. But I think that, um, I sort of don't want to say it out loud, but I think, I, I think that something happens when, when couples have their first baby. And almost every single time, that couple is like, something definitely went wrong because that was so bad. Like, that was so bad. And it's sort of only when you're on the other side of it, you're like, no, it really, it really, really is that bad. We just didn't tell you. Like, we just didn't tell you. Or maybe you just didn't hear. Maybe you just didn't hear.

• 34:14Speaker 00

  Or I think also having young children is a similar thing, you know? I think if anybody really told you how much sleep you lose, I think people sort of, they kind of dance around it a little bit, but then don't actually say it, you know?

• 34:28Speaker 01

  Yeah, well, right. I mean, it's, it's hard to make it clear. Like, oh, you're gonna, you're not gonna sleep much. It's gonna be stressful in brand new ways. It's, it's hard to really conceive of what that means. But at the same time, there is growth that comes from that. Like, I have learned things about myself and my childhood that I never would have learned or thought of if I had not been a parent. I think I've said this before, but having a kid is like a big psychedelic experience. It can go really wrong, but it can also go really right. And you can really, like, reach a higher plane. It's up to you. It's all about the set and setting.

• 35:10Speaker 00

  Yeah, I think that's true. I think it's not just about new birth, so I think it's also about death. I think that, I think that people maybe deliberately, or maybe because it's just too painful, hold back on some of the details of what it's like to be close to somebody as they're dying, you know, what it's really like. And I think that partly it's because maybe other people aren't ready to hear it. But I, but I also wonder whether it's a bit like your Egan idea of like, actually, you just don't need to know. You just don't need to know. You don't need to know unless you have to, unless, unless you're unfortunate enough to go through it.

• 35:44Speaker 01

  I wonder if it's also just really hard to articulate some of these really difficult things. Like, we just don't have the ability to communicate the kinds of pain. It's not that we're shielding other people from it. We just can't even ourselves really grasp what was so difficult and why. So we just say, ah, yeah, it was bad, but like, it's okay.

• 36:11Speaker 00

  Or maybe it's also that actually the people listening are not in a position to really hear it.

• 36:18Speaker 01

  Right.

• 36:18Speaker 00

  Like, to really understand it. So, for example, I did this program. Did this program recently, and I spoke to a person who'd previously been on the program. And they said, it's really, really fun, but it's also really, really hard. And I was like, yeah, yeah. And then I went on. And then I spoke to her afterwards and I was like, you didn't tell me it was really hard. She was like, I did.

• 36:46Speaker 01

  She did.

• 36:47Speaker 00

  I did. I just didn't, I just didn't hear it.

• 36:51Speaker 01

  Yeah, the ways we take and give advice and what we hear and don't hear in it, and, and say and don't say in it, I think is, would be a really rich place to investigate. Because you're right, advice never really prepares you completely for anything. And then afterwards, you are incapable of producing the advice that you should. Like, it just kind of has to be experienced, so many things.

• 37:18Speaker 00

  Yeah. Like, you do transition. You change. You are time traveler yourself, right? You, you become a different person as you have these different experiences.

• 37:26Speaker 01

  Yeah.

• 37:27Speaker 00

  That one got very deep, didn't it? Anyway, so shall we, shall we move on?

• 37:33Speaker 01

  Yeah, all right. Look, Olive Ridley asked this question. I've been having a think about dragons. Could it ever be biologically possible for an animal to anatomically produce fire? I think bombardier beetles are on the right track.

• 37:49Speaker 00

  Okay, so bombardier beetles, right? I've been watching videos of them today. I hadn't actually come across them before. But like, they're incredible, these things. So other animals will try and eat them. And then they quickly learn because what they do is, uh, when they're sort of attacked or they're disturbed, they, they turn around and then they have essentially an internal chemical explosion in their abdomen. And then they expel this jet of boiling, like, acid, um, towards their attackers. I've seen a, a couple of videos of a mongoose getting this, uh, this stuff sprayed in its eyes. It, the mongoose did not, did not appear happy.

• 38:28Speaker 01

  And it's actually boiling hot?

• 38:30Speaker 00

  Yes, it's like superheated.

• 38:32Speaker 01

  So the, the heat comes from the chemical reaction. Obviously, the animal isn't, doesn't have a little oven inside of it.

• 38:38Speaker 00

  No, exactly. Um, what it's, uh, it's, it's hydroquinone and hydrogen peroxide, right? Which is this, and those who are actually quite common as a defensive, um, agent amongst insects. But what they're doing is because they are, uh, combining, they're like, they're creating this chemical at the exact moment of use. They're kind of mixing these two chemical precursors in this protective chamber in their hindquarters. And then as they combine, they can get, it sort of gives us this intense heat and they expel it exactly that moment. And they've got this little passageway, basically, between the two internal chambers that opens and closes when they want to, like, spurt it outwards.

• 39:17Speaker 00

  So, okay, that's like, that's pretty good, but it's not actually ignited. It's, it's pretty good, but it's, it's not actually on fire. There is this paleontologist called Philip J. Center, who's trying to work out what are the different options for fire-breathing creatures? And, and why haven't we got one? And there's like a few different ways that you could do it. One is that if you, I mean, methane is already produced by a number of animals, us included, cows also notably. You know, cattle and sheep in particular, they, they, they belch, you know, dozens of little methane burps every hour. So all you've got to do is ignite it.

• 39:58Speaker 01

  But igniting the methane is the question.

• 40:01Speaker 00

  Which wouldn't even be that hard. There are animals that produce electricity, you know, that would be, getting the spark wouldn't be hard.

• 40:07Speaker 01

  True.

• 40:08Speaker 00

  The problem is that the methane cloud would probably envelop the animal's own head. So that, not so good. Also, by the way, there is actually some evidence of this genuinely happening in humans. Where someone belches while they're, they've got a cigarette, and then they burn themselves.

• 40:28Speaker 01

  Really? So, so there's enough methane in the belch that the cigarette lights it?

• 40:34Speaker 00

  I think in particular, there's something going on already with the, which is allowing them to produce a more flammable burp. So, and that's, you know, burping is not, it's just not gonna work. It's not gonna work, right? These, you're gonna, you're gonna burn yourself first. Oh, there's also the idea that you could create a gas cloud. So rather than just like burping, you could sort of create a little cloud, uh, like a nostril.

• 40:58Speaker 00

  There are, uh, these chemicals called polyphoric molecules which do burst into flame as soon as they come into contact with air. So that might work. Uh, but again. Unfortunately, it just detonates too close, even if it comes out of a very narrow hole, like a nostril, right? It detonates right next to the tube opening. So we're just like,

• 41:18Speaker 01

  Yeah.

• 41:18Speaker 00

  Burn your nostril if you're a dragon. And then the, then there's also hypergolic pairs, which is where you get two chemicals that ignite spontaneously on contact. This is like very close to what the Bombardier Beetle is doing. But unfortunately, these things, I mean, the, the, the temperatures are incredibly high. And, you know, it creates this like scalding liquid rather than a flame. So there's no spark, there's no ignition. Sort of, you know, it doesn't really, it doesn't really work. So unfortunately, every fire mechanism that's been proposed doesn't, doesn't really work in a real animal because you can't do it without cooking your own face.

• 41:58Speaker 01

  Right, I mean, there, there are hypergolic mixtures that will ignite, but I'm sure they're like super toxic to a living thing.

• 42:05Speaker 00

  Hmm.

• 42:05Speaker 01

  You're right, I think the Bombardier Beetle is there, but the methane thing sounds like the best bet. If you could, the problem is creating enough methane to get like a nice flame and you'd have to shoot it out at a lot of, at a high pressure.

• 42:19Speaker 00

  Right, definitely.

• 42:20Speaker 01

  The animal would have to evolve to have like compressed liquid methane in its body that it could then expel.

• 42:27Speaker 00

  Yeah.

• 42:28Speaker 01

  And, and then it would have to do like an electric eel little spark thing to ignite it.

• 42:34Speaker 00

  It's not beyond the realms of possibility. I mean, if it produced the same amount of methane as a cow, but just happened to be the size of a beetle, that would work.

• 42:42Speaker 01

  Okay.

• 42:43Speaker 00

  There's enough, there's enough pressure there.

• 42:45Speaker 01

  Maybe it's not enough of a deterrent. Like it'd be better to just evolve fast legs to run away from a threat.

• 42:54Speaker 00

  Or wings, or wings.

• 42:55Speaker 01

  Than to breathe fire at it.

• 42:57Speaker 00

  Wow, it's a shame.

• 42:58Speaker 01

  I, I would almost think that fire breathing would be more advantageous to a creature for other like practical reasons, not attack and defense, but just to create warmth. Like humans had to have opposable thumbs and the ability to get flint and, and create fire and then feed the fire and collect what's needed for its fuel.

• 43:21Speaker 00

  The problem with fire is it doesn't really discriminate, does it? You know, once it's out there, it's sort of, you're sort of, it's, it's a bit like when there's people who suggest that smallpox could be released by a, a bad actor in order to gain some sort of military advantage. Like, yes, sure, but smallpox doesn't, smallpox doesn't discriminate between you and your enemies, you know?

• 43:43Speaker 01

  Right.

• 43:44Speaker 00

  And fire doesn't either. And I think that unless these dragons are also fireproof, I agree that it's, it's, it's not a good defense mechanism.

• 43:53Speaker 01

  It's too dangerous.

• 43:55Speaker 00

  To burn down your own home to scare away a burglar.

• 43:58Speaker 01

  Cause I was just imagining if, if some like dinosaur had evolved the ability to start a fire and then they could have started cooking their food and consuming more calories and their brains got bigger and like they became the intelligent species on our planet. Problem is, it'd be a big risk, you know? A dinosaur gets stampeded and it explodes. Whereas the way humans controlled fire protected us from that risk. We weren't walking flammable creatures. We had to

• 44:32Speaker 00

  No.

• 44:33Speaker 01

  Decide deliberately, we're going to do a fire here. And that's maybe a better way to do it.

• 44:39Speaker 00

  I think overall it probably is. So yeah, sorry about that. Yeah, apologies, Olive. No fire breathing dragons for us this time. Okay, I think that brings us to the end. As ever, please do send us in your questions to [email protected]. You can also leave us comments under this video or go to our subreddit, which I only recently found out about, r/the rest is science. We read all of the things that you send us. And if you're lucky enough, if your question is good enough, if we think you're kind of cool enough, then maybe we'll answer it here.

• 45:13Speaker 01

  Yeah, see you over there. I mean, I hope so. Side note, I can't use my Reddit account anymore because I set it up using my old Google email address when I worked at Google. I no longer have access to that. And now Reddit is saying, I have to like change the password, but I can't get any of their emails. So Michael Stevens on Reddit is just like, I, I can't do anything. So, president of Reddit, if you listen to the podcast, I'd appreciate that, but I, I'll, I'll make a new account if I have to, because I want to see you guys over there on our subreddit. And yeah, email in your questions if you prefer. We love hearing from you and until next time, see you later.

• 45:51Speaker 00

  Bye bye.

• 46:04Speaker 06

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