Pod Insights Daniel and Kelly's Extraordinary Universe Listener Questions #44 - How fast can animals go, and how fast can animals grow? (featuring Dr. John Hutchinson) About this episode Dr. John Hutchinson is back to help Kelly and Daniel answer listener questions about how fast animals can grow, how fast animals can go, and whether animal size impacts average lifespans. Also, cheese.
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Transcript 11,079 words · 7 speakers
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2:22 Kelly Weinersmith? If humans ran as many body lengths per second as a mite, we'd generate a sonic boom. What are the factors that determine how fast a critter can go zoom?
2:33 Daniel Whiteson? Creatures in movies grow too fast. Gremlins and aliens just aren't plausible. But let's do a thought experiment. Could you design a creature to grow as fast as possible?
2:45 Kelly Weinersmith? Do smaller animals have shorter lives because of the curve of space and time? And if they lived long enough, would Daniel and Kelly ever get good with rhyme?
2:55 Daniel Whiteson? No.
2:56 Kelly Weinersmith? No. Problem solved.
2:59 Daniel Whiteson? But whatever questions keep you up at night, Daniel and Kelly's answers will make it all right.
3:04 Kelly Weinersmith? Welcome to Listener Questions, episode 44, featuring Dr. John Hutchinson.
3:22 Daniel Whiteson? Hi, I'm Daniel. I'm a particle physicist who likes to think about aliens, and I'm still growing in all the wrong directions.
3:30 Kelly Weinersmith? Same. Hi, I'm Kelly Wiener-Smith. I study parasites and space, and I've never been fast. No, no one has ever said, will Kelly break a speed record? The answer is no.
3:42 Daniel Whiteson? I'm also not very fast, and my wife, she's fit. But neither of us are speed demons. However, we somehow birthed a child who is very athletic and is now like running in college. And I don't know what happened. Cosmic ray mutations, swap at the hospital, something.
4:00 Kelly Weinersmith? Biology is really complicated, and life tells us that.
4:05 Daniel Whiteson? Exactly. Will your kid be like you? It depends.
4:08 Kelly Weinersmith? It depends, and you hope not. For their sake, for their sake.
4:15 Daniel Whiteson? You hope they get all the best of you and all the best of your partner.
4:18 Kelly Weinersmith? That's right.
4:18 Daniel Whiteson? And today, we're going to be marrying our knowledge with the knowledge of Dr. John Hutchinson, who knows a lot more about evolutionary biomechanics than we do.
4:27 Kelly Weinersmith? So let's waste no time and get John back on the show. Dr. John Hutchinson is a professor of evolutionary biomechanics and a fellow of the Royal Society. His research straddles the fields of evolutionary biology and biomechanics with an emphasis on how very large animals stand and move and how locomotion evolved in different groups of land vertebrates. And at the end of this episode, you're no doubt going to be thinking, how can I get more of John? And the answer is you can listen to our April 29, 2025 episode where the title was, Was the Tyrannosaurus Rex Fast or Slow? Because this is John's second time on the show, and so you can go back and enjoy that episode. Welcome back, John. Thank you. Great to be back. We're excited to have you. We had a ton of fun last time.
5:11 Daniel Whiteson? Your expertise spans our audience's interest because we're talking about biology, since these are critters, but we're talking about the physics that makes them move fast or slow. So you're like the perfect guest for the podcast.
5:24 Kelly Weinersmith? I can't claim to be a physicist, but I understand what I need to understand for understanding a bit of biology. That's good. Well, then let's just jump right in. So our first question of the day is from Matt McCain. He's one of our Discord moderators. He asked this question.
5:39 Daniel Whiteson? Yay, Matt.
5:40 Kelly Weinersmith? Yay, Matt. And he asked this question like a million years ago. And every time I pulled up a paper, there were loads of equations and it was in physics related journals. And so I kept putting it aside and quitting on it. And then eventually I realized, why don't I just ask John?
5:55 Speaker 04 Hey, Daniel and Kelly, your friendly neighborhood moderator, Matt here. I recently went down a rabbit hole of how fast certain critters move, and then that led to a cascade of questions. So. I heard about the tiger beetle moving so fast they can temporarily go blind, like their eyes can't take in enough photons to form an image while they're cruising along. So that's kind of weird. Due to their tiny size, though, bugs can't really scale up. But if we did, I was wondering if we could compare and figure out what the fastest animal is relative to size. I'm not sure if that even is scalable. And we often hear trivia about birds and other critters being some of the fastest in the world. And then that led to me finding out they sometimes measure speed in body lengths per second.
6:38 Speaker 04 Currently, the almost unpronounceable Parotarsotomus mite is the reigning champ at about 302 body lengths per second, which would be like a human equivalent running at over 1,300 miles per hour. That's kind of fast, coming in at Mach 1.7, sonic boom human territory. Help me out.
6:58 Kelly Weinersmith? John, go.
7:00 Speaker 02 Well, if I could tackle the tiger beetle first, because I think that's an interesting case.
7:05 Kelly Weinersmith? Great.
7:05 Speaker 02 What I think the scientific understanding is that they don't go blind if they go too fast. Not quite. Their ability to chase down prey depends on the contrast of the prey to the environment. So if it's like, the best case, like a black insect on a white background, then they can see it better. And as they go faster and faster, their contrast blurs, their visual contrast blurs. So they have to stop periodically if the contrast is poor versus how quickly they're going.
7:39 Daniel Whiteson? Why does their contrast blur? Is this something to do with like the response of the proteins, how quickly they can recover?
7:46 Speaker 02 This is a visual limit that their nervous system can only process and adjust to the visual information based on the contrast if it's coming through in good enough quality and at a good enough of a rate.
8:00 Daniel Whiteson? But why does the relative velocity of the object change that? Like if it's moving across your field, I guess it's a question of like how quickly the neurons can update?
8:10 Speaker 02 Yeah, so maybe if you can imagine a really quick movement or a really slow camera, there will be blur with that. So you can't really adequately visualize that. And so you're. Nervous system's perception of where the object actually is in space will be increasingly imprecise visually based on how fast the object is.
8:34 Daniel Whiteson? Let me just make sure I understand. So you're saying,
8:35 Speaker 02 Yeah.
8:36 Daniel Whiteson? if we think about the eye as a camera, it's got a shutter speed.
8:39 Speaker 02 Yeah.
8:40 Daniel Whiteson? And just like something that's zooming through your field faster than the update speed than the shutter speed is going to create an image that's smeared across your field because the eye is accumulating data over that time period. And so it ends up smeared. Is that a fair analogy?
8:57 Speaker 02 That's my understanding of it. And I don't know exactly how the tiger beetles visualize objects, but my understanding is that it's a really a matter of the contrast of the object that that is a big, big factor.
9:11 Daniel Whiteson? Interesting.
9:12 Speaker 02 And their prey contrast, how dark the prey is relative to the environment and so forth will vary a lot depending on the prey and the environment.
9:20 Kelly Weinersmith? So do they tend to go after really like snazzy, brightly colored, flashy prey then to try to make it easier to see them?
9:27 Speaker 02 That I don't know. And there might be really counterintuitive issues like I don't know exactly how tiger beetles see. Do they have any spectra of the of the light spectrum that they see differently from us, like ultraviolet or whatever? I don't know. Or do their prey respond to light differently visually? Yeah.
9:49 Kelly Weinersmith? Oh.
9:50 Speaker 02 I'm no entomologist, so I can't can't answer that question.
9:54 Kelly Weinersmith? I'm gonna go on a flashy food diet. I only eat food that is highly contrasting and blings a lot relative to the environment.
10:01 Daniel Whiteson? I only eat slow food, things that sit on my plate and have a very low velocity relative to me.
10:05 Kelly Weinersmith? Okay.
10:06 Speaker 02 I'm all more olfactory.
10:09 Daniel Whiteson? I think the slow food movement means something else, but.
10:13 Kelly Weinersmith? Yeah, I think olfactory is probably the way to go. You might enjoy your food more, more than the rest of us.
10:20 Daniel Whiteson? I like eating at the olfactory spaghetti factory.
10:23 Kelly Weinersmith? Okay.
10:25 Kelly Weinersmith? We've got a bit caught up on the vision thing. I have a friend who studies tiger beetles, and he tells me that they're the fastest animals on the planet. And he's right about most things. But your face suggests to me that maybe this isn't one of them.
10:41 Speaker 02 Well, they're pretty damn fast. And the person asking the question is is correct for their. Size, they're they're pretty crazy fast. And that's true of a lot of small things. If you normalize, if you divide speed by by body length, small animals are always going to be fast, unless they're really slow, small animals like a tick or something like that.
11:01 Kelly Weinersmith? So does does that suggest that's not the best way to measure it then? Because it's a it biases towards small animals?
11:07 Speaker 02 Well, I think it reveals something about the fundamental nature of speed, that speed limits on animals are very different depending on the size. There's fundamentally different physical laws, if you will, that influence how small animals are limited in their speed versus how large animals are limited in their speed.
11:29 Kelly Weinersmith? How well do we understand those laws? Is that like something that's easily articulated?
11:33 Speaker 02 Yes, pretty well. We understand pretty well the the overall gestalt of what limits animal speed. So smaller animals, the smaller that animals are, the more that the power of their muscles, so how much force the muscle can produce and how quickly they can produce it, that becomes really limiting on speeds. They have to have really quick muscle. There's a big contrast with that and big animals, where it's not so much the power, like the rate of doing energy or work with the muscles. That doesn't matter so much as just the amount of force that the muscles can generate
12:16 Speaker 02 and the amount of distance those muscles can move the body over, which is force times distance is work. That's the energy of the animals. So so rate is not so important for big animals in limiting speed. They don't have to produce force very quickly. They have to produce a lot of force, basically. So gravity ultimately limits big animals more than small animals. And that's why, for example, it's very well known, like ants can carry many, many times their body weight. And that's because gravity just doesn't limit them so much at all. Their their strength to weight ratio, which is a fundamental aspect of biology, is extremely high. And that's true of pretty much all organisms,
13:00 Speaker 02 that the smaller they are, the stronger they are relative to. Their their weight.
13:04 Daniel Whiteson? And is that just because of geometry and that the strength depends on the cross sectional area of your bones and your muscles? And that grows by like length squared, whereas your weight depends on your volume, which grows like length cubed?
13:17 Speaker 02 Exactly, that's the square cubed law. So that governs a huge amount of biology that we can understand how size influences organismal biology by understanding how things like length and area scale with body weight and how other things change with body weight.
13:36 Daniel Whiteson? And so if we were like on Mars with lower gravity, we might expect like bigger ants?
13:42 Speaker 02 Oh, so limits on size. Yes, yes, that is true. Although it would depend on other factors like oxygen.
13:51 Daniel Whiteson? Right, of course, I wasn't suggesting there literally are huge ants on Mars, though I would love that. I guess I was just more thinking about like alien environments with different gravity, there would be a different range of what you call small or large creatures, it sounds like.
14:07 Speaker 02 Oh, yeah, I mean, that's a given, definitely, definitely. At least the potential for that, depending on how long those organisms have been there over evolutionary time.
14:16 Kelly Weinersmith? So if you had two animals that were the same, kind of the same shape, but definitely the same like mass or height, like so two animals that kind of looked like deer, but one was much faster than the other, what would be the thing that was different? Would it be the kinds of muscles they have or the way they attach to their bones? I didn't completely get that in my head.
14:41 Speaker 02 Probably the biggest difference would be how muscular they were relative to their size. So were they, were they really, really like Usain Bolt, really, really jacked? Or were they built more like a marathon runner? Pick your favorite marathon runner, I can't think of one at the moment.
14:59 Kelly Weinersmith? Okay, so big animals need to have more muscles. And if you have two animals that are like tiger beetle size and one is faster than the other, the difference would be the efficiency of their muscle? Was that right?
15:12 Speaker 02 Well, it might be how quick their muscle could contract or something like that, something that influences their ability to generate a lot of force quickly.
15:21 Kelly Weinersmith? Okay. And what's the fastest animal you've studied?
15:25 Speaker 02 So, I mean, I've studied cheetahs, but not really studying them at their top speed. Other people in our lab have.
15:33 Kelly Weinersmith? That's actually a great segue into another question, which is if you're trying to measure maximum speed, how can you be sure you're measuring maximum speed? Like, how do you get an animal to go as fast as it can so that you can make these kinds of measurements in the lab? Because that sounds kind of complicated.
15:50 Speaker 02 Yeah, that's always the fundamental challenge. And that's why model organisms, organisms that we can really understand well, like, well, humans are a great model organism because they can tell us what's going on. We can tell them what to do and they'll do it. So we can, we can get a good measurement of human maximal speed. And so that's around, you know, 11, 12 meters per second for the best sprinters. But other things have to be cooperative. So you can get a dog on a treadmill, horse on a treadmill, something like that, and get them to run as quickly as they can, either on a treadmill or a race course. And there you can be pretty confident that because they're trained to race, to go as fast as
16:32 Speaker 02 they can, more or less, then they're going to give you their, their maximal speed. But if you're studying an elephant, as I did, you may not get them to go very fast. Motivation's a big issue. So I studied elephants in zoos, starting off, and found that they were pretty slow in zoos, unsurprisingly, because it's hard to motivate them. They don't have a lot of space, so forth. So I went to Thailand. I studied elephants there that are used in races periodically. And they were way faster than like a Western zoo elephants on average.
17:07 Daniel Whiteson? So what motivates an elephant? How do they make the elephant run?
17:11 Speaker 02 It varies. So sometimes cheering for them, sometimes having them chase another elephant or run to a friendly elephant. They're smart animals. You have to kind of work around them and their personality and figure out what will motivate them.
17:26 Daniel Whiteson? Elephants respond to cheering, like peer pressure will encourage an elephant? That's amazing.
17:31 Speaker 02 Oh, yeah. They're, they're super smart, super smart, social animals. So. And they're bonded with their trainers in Thailand because they grow up together. Literally, the humans, the mahouts, as they're called, and the elephants spend their lifetimes growing up together, developing bonds. And that's why they were able to motivate their elephants very well. So by studying lots of elephants over and over and over again, getting them to walk and run at different speeds, we're able to, again and again and again, get pretty much the same speed out of all the elephants. And that was the fastest ever reliably recorded.
18:06 Daniel Whiteson? Assuming that elephants don't have some secret top gear that they're just not interested in sharing with us humans.
18:12 Speaker 02 Yeah, so then you have to kind of go by extraordinary claims require extraordinary evidence. And so we need some sort of evidence of that secret gear. Yeah, that's that's special pleading in science or in philosophy of science. You can't do that. You can't just say, oh, they're just holding back. They could do more. You need some, you know, some sort of reason for that. But it's definitely true. Many animals do hold back. So, and many estimates of speed that are out there in the scientific literature are wild guesses at best because of the unreliable nature of estimating animal speed. If you just watch an animal moving out in nature, you could easily be off by 50, 100%
18:57 Speaker 02 in your estimate of the speed of the animal because we're not great at estimating speeds.
19:02 Daniel Whiteson? What about scenarios like horses versus buffalo? Right there, the buffalo are clearly motivated by survival, especially if there's somebody on horseback shooting at them. And the horses are motivated by the rider. Who's faster in that scenario, buffalo or a horse?
19:18 Speaker 02 They're gonna be pretty close because their size is pretty similar. They're pretty similar in terms of musculature, but the horse has a slight edge there based on length of the legs and lightness of the feet and so forth. They are a bit more adapted for running quickly. But bison, buffalo, so forth, they can run fast. I mean, they're also ungulates, so hoofed mammals, which in general have very lightweight long limbs that they're able to move quickly and therefore run quickly. inefficiently.
19:50 Daniel Whiteson? I don't think of a bison as fast because I think of them in the cow category and I just never really imagined a cow going anywhere quickly. But I've seen buffalo run because they have them at Fermilab. You know, we only need the underground and so they have a herd of buffalo. And yeah, they can move.
20:06 Speaker 02 Yeah, yeah, it's the cow bias that I think is making us think of
20:12 Speaker 02 less familiar animals as slow. Yeah.
20:15 Kelly Weinersmith? So what do we think is the fastest animal? And how confident can we be given how bogus some of these estimates are that we actually know what animal is the fastest?
20:25 Speaker 02 Oh, well, the cheetah on land and that's the key thing to qualify on land. The cheetah is the fastest. There's no question about that. Pronghorn antelope come close, but cheetahs have been reliably measured at around 65 miles an hour.
20:40 Kelly Weinersmith? Yeah, that's pretty impressive.
20:41 Daniel Whiteson? But that's in the metric of like speed relative to the ground, not in body lengths per second.
20:46 Speaker 02 Absolute speed is that's what I'm going based on. Yeah. But then, yeah, things like the might that the question asker mentioned. Yeah, I mean, if you go down to really tiny size, then body lengths per second is going to give you a faster speed relative to body length for smaller things.
21:07 Daniel Whiteson? And why is the might so fast? Like, why is it so mighty?
21:12 Speaker 02 I think that might be the wrong question that maybe it doesn't matter. It may not matter how fast the might is. I mean, where do mites need to go? They're not like going long distance. They're not.
21:23 Daniel Whiteson? What motivates the might?
21:24 Speaker 02 Avoiding predators that are chasing them in a in a pursuit kind of situation. They're pretty, in general, I mean, I can't speak for all mites, but in general, mites are animals that are in hiding a lot of the time and they're not going to be running around like a buffalo is on a on a grassland. Their environment is completely different, much more cluttered. So they're just going from place to place, short distances. And that's true of a lot of small animals that if you watch them, they don't move long distances for long periods of time. They use intermittent locomotion and that's the case of the tiger beetle to circle back to that is that because of their visual blur, they have to stop periodically, stop running
22:09 Speaker 02 to recalibrate where the prey is by just reducing that velocity based blur. And so that's their, that's their solution is they slow down or even stop. And lots of small animals do that is slow down, stop, check out the environment and then take off again if they're, if they're moving quickly.
22:30 Kelly Weinersmith? All right. Well, I think it's time to circle back to Matt and see what he has to say about this answer.
22:36 Speaker 04 Oh, wow. You guys really brought out the big guns for my question. Thank you, Kelly, Daniel and Dr. John Hutchinson for answering the questions that have been terrorizing my brain. I really was though, hoping the tiger beetle gained like some dark sunglasses and like a walking stick when zooming around. Unfortunately though, as I was leaning, there's really no scaling for a true comparison. And if I think too hard about it now, a giant tiger beetle sporting some dark sunglasses, stopping, removing said sunglasses like the dude on CSI to look around for prey, sounds kind of terrifying to me. I appreciate all the time and effort you all took to do this deep dive for me. And I'm going to give a quick plug to come and join in the fun, sciencey discussions in our Discord. This community is truly amazing. We could always use more pet pictures. Thanks for everyone
23:21 Speaker 04 for being spiffy and awesome. See you in the Discord.
23:24 Kelly Weinersmith? All right. That was awesome. Or was there anything else you wanted to say on that one, John?
23:27 Speaker 02 Well, I'll give a personal interest about speed. And that's if you've ever encountered a huntsman spider, like out in East Asia, Australia, so forth, you will be pretty startled by how quickly they can move. So these are usually pretty sizable spiders. They're, they're pretty freaky looking. If you, if you have any sort of arachnophobia, they got it all. They got the big fangs, long legs, flat bodies, often kind of hairy looking. And they can move blindingly fast. So I went into a hotel in Taiwan and right away when I checked in, opened a closet. And out came a huntsman spider sprinting across my room.
24:08 Kelly Weinersmith? Ah.
24:09 Speaker 02 And I couldn't find it, but I had to go out for dinner very shortly thereafter. So I had to leave it in my room. I'm, I'm not cool with sleeping with spiders. I'm just not down with that. So luckily we made our peace when I got back to the room after dinner and I was able to sleep without worrying that there was a huntsman spider there. But yeah, they can go 3.6 meters per second is the fastest brown huntsman spider. You know, that's a moderate speed jog for us, for a pretty small animal. The brown huntsman, Heteropoda cervina is the genus and species. So if you're interested in those, they are the fastest reliably recorded spider.
24:47 Kelly Weinersmith? I didn't want to know that. I will now live in fear and they're, are they venomous?
24:53 Speaker 02 Mildly, um, they'll hurt a bit if they bite you, but no, they, they eat, uh, bugs and geckos and so forth, but their, their, uh, venom is more suited to.
25:03 Kelly Weinersmith? They eat geckos. And so when you said we made our peace, does that mean he's now resting in peace? Or how did you make peace with the huntsman?
25:11 Speaker 02 Oh boy, I don't want to go into the details. Yeah.
25:14 Kelly Weinersmith? All right, moving on.
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28:25 Kelly Weinersmith? And we're back. And now we're answering a question from Aaron. Here is Aaron's question about the limits to how fast an organism can grow. Hey, Daniel and Kelly. I'm always frustrated in movies when creatures grow too fast, like gremlins or the aliens in the Alien movie franchise. They're the size of a puppy, and then hours later, they're the size of a full grown person. Seems biologically impossible. I've got no problem suspending disbelief. But this does make me wonder, what organisms grow the fastest? What are the biological, chemical, or whatever limits that define and limit the speed of growth? Seems like from an evolutionary perspective, growing superfast would be advantageous.
29:06 Kelly Weinersmith? Do a fox, great white shark, and human being all basically grow at the same speed? And if you were designing an alien creature to grow as fast as possible, what tweaks at the cellular level would you make to promote the fastest possible growth? And what would the trade offs be? Also, do plants share similar growth limits to animals? I know kudzu can grow pretty fast. Thanks a lot.
29:31 Daniel Whiteson? Thank you, Aaron, for including aliens.
29:33 Kelly Weinersmith? All right. Where do you want to start with that one, John?
29:37 Speaker 02 So with the aliens, I think the quick answer there is that they've still got to abide by the, some of the fundamental principles of whatever physiology they have. But their physiology could vary, perhaps dramatically, from what we have. I mean, there, we're only left to speculate. But there's also the fundamental principles of size and growth probably generally hold, even in alien organisms, that growth rate tends to be slower in bigger things overall. And yeah, like, when I watched the movie Alien Romulus, I hope this isn't a spoiler,
30:17 Speaker 02 but there's at least one xenomorph, one alien there, that that seems to grow in the space of the two hours of the movie, from a little thing, like a little fetus-sized thing, to a, something bigger than a human. So, yeah, I mean, that caused a bit of credibility issues for me, but hey, it's movie logic, and it's alien biology, so, I mean, can give it a benefit of the doubt there.
30:43 Daniel Whiteson? So you say the fundamental rule is that bigger things grow more slowly. That must be a relative
30:49 Speaker 02 Yep.
30:49 Daniel Whiteson? thing, like an elephant adds a smaller percentage of its body weight every day or week as it's growing than a smaller creature does. Why is that? What's the rule that underlies that?
30:59 Speaker 02 Yeah, so that's due to the underlying physiology. Metabolic rate is the key thing there, that smaller animals have higher metabolic rates. So, yeah, and that's even true. Of people like when we're young, we have pretty high metabolic rates and metabolic rate slows down as we get older and that relates to our growth rate. So there's a correlation between how quickly you burn energy and how quickly you grow.
31:29 Daniel Whiteson? Is that what metabolic rate means? You're converting inputs into energy?
31:33 Speaker 02 How you use your internal energy to generate something else to transform your internal energy like ATP molecules into something being done to your benefit like growth.
31:52 Daniel Whiteson? And why do bigger animals have a slower metabolic rate? Or is that not known?
31:56 Kelly Weinersmith? It's a bummer either way.
32:00 Speaker 02 Bigger animals grow more or have slower metabolic rates because again of the square cube law that because a growth rate depends on area to volume scaling bigger animals have less area relative to their volume. So they can't use energy as quickly as a smaller animal can. And yeah, smaller animals, because they have more area relative to their volume, are shedding heat more quickly or gaining heat more quickly from their environment.
32:32 Daniel Whiteson? So that seems like an argument that would work for like warm blooded animals that spend energy to stay warm. What about like a snake or a lizard or something? I know that they're losing energy to the environment, but they're not burning energy to stay warm. Right?
32:45 Speaker 02 All organisms burn energy to stay warm if they're alive. If they're dead, then then maybe not. But, but, but yeah, because metabolism is fundamentally a wasteful process. It's not 100% efficient. You don't convert your metabolic energy into whatever you want to do with it at 100% efficiency. There's always heat shed. We have to remember heat and heat in biology is just waste, a waste product of what's going on. So there's actually a lot of waste, a lot of heat, like muscle tends to
33:19 Kelly Weinersmith? Be only thirty percent efficient, the rest goes away as heat. And so even small animals, if they're just sitting there, they're burning energy, quite a lot of energy, just sitting there and not just to stay alive, but to remain warm, keep their organs at the right temperature during their physiology. But yes, it's true that smaller animals tend to be ectothermic. That is rely more on their external environment to keep them warm or be quote unquote cold blooded. Whereas larger animals tend to be endothermic, produce their own body heat more, rely more on that, maintain a more constant body temperature.
33:58 Kelly Weinersmith? Whereas ectothermic animals tend to vary their body temperature more because of their environment. And those two things, endo ectothermy are sort of a continuum, but but it's complicated. Biology, it's complicated. Yeah, the ambient temperature does have a big effect on metabolic rate and on growth, especially in ectothermic or cold blooded organisms. They rely on on the environmental temperature to regulate their metabolic rate and therefore it will influence their their growth rate.
34:33 Daniel Whiteson? Thanks for correcting my naive ninth grade biology knowledge. Makes perfect sense that even if cold blooded animals are not trying to regulate their temperature, of course, their metabolism is subject to the laws of thermodynamics, which means there's waste and it produces heat. That makes a lot of sense.
34:50 Kelly Weinersmith? Please, please correct my physics. Please correct my physics at any time.
34:55 Daniel Whiteson? And so this connects back to the original question because this was how we were understanding why bigger animals have a smaller growth rate per mass. It's because they have a slower metabolism because they have more volume than surface area. Is that the right connection?
35:13 Kelly Weinersmith? Yeah, but it also ties into some really interesting other things that are tied into metabolic rate. And metabolic rate also depends on having the right resources. You need to be able to get enough food and so forth. That's very important. But fundamentally, if we go down to the cellular level, like the the person asked, the rate of cell division is a fundamental limit on growth rate. You have to be able to do mitosis, split your cells quickly enough to grow. And that depends on the metabolic rate in part.
35:48 Speaker 02 But it also depends on stuff that's going on inside the cell than various molecular processes of the nucleus. And a fundamental thing, a really cool thing that limits growth rate is DNA repair. If you think about it, if you're growing your cells really, really quickly, you'll potentially accumulate more and more errors as you're splitting your cells over and over again. And if that error accumulates over and over again without getting fixed, then you'll get potentially either malformation of the organism, or in a worst case, cancer, because cancer really is overactive growth rate. It's uncontrolled cell division, basically.
36:31 Speaker 02 So growth rate, if it's too excessive, could even be cancerous, or at least lead to malformation. And that depends on the various repair mechanisms in cells, DNA repair, programmed cell death, other things that are there to correct for error. Error in in cells is a very big problem, both in the actual longevity of the cells, but also in an evolutionary context, there's surely huge selection on repair mechanisms for cells to make sure they don't go haywire and just produce lots of errors and malformations or cancer or whatnot.
37:10 Kelly Weinersmith? So we might all be growing much faster if we could perfectly replicate and we didn't have to worry about getting cancer?
37:17 Speaker 02 That's right. If we can control that repair mechanism, that could do some wonderful things for growth rate and other things like lifespan.
37:25 Kelly Weinersmith? I could be twice as big.
37:27 Daniel Whiteson? Why would you want that?
37:30 Kelly Weinersmith? I'm just kidding. I don't really want to be twice as big. I'm plenty big, but.
37:33 Daniel Whiteson? But it sounds like when you're watching Alien Xenomorph, Romulus, or whatever, your real biology constraint is like, hey, that alien should have a lot of cancer, given how fast it grows.
37:44 Kelly Weinersmith? Oh.
37:45 Speaker 02 Unless it has some super alien correction mechanism. So who knows? It could be using silicon as. It's rather than carbon is its fundamental molecule. So then it could it could cheat.
37:59 Daniel Whiteson? That would be a great twist if we could use alien xenomorphs as a way to find a cancer cure. Right? Like, what if they have some cool biochemical technology in them?
38:06 Speaker 02 Write it up. There's your movie script right there.
38:10 Daniel Whiteson? Netflix, call me.
38:12 Kelly Weinersmith? That's right.
38:13 Speaker 02 Other things that become important to growth rate are also parental care that animals that are cared for more by their parents can potentially grow more quickly, especially if they're being provided by their parents with lots of high nutrient foodstuffs, but also reproductive rate will influence growth rate that if you need to get to adulthood quickly so that you can reproduce yourself and your population quickly, then growth rate will need to be adequate, although that there's a trade off with the next thing that we'll talk about, which is lifespan. So growth rate, metabolic rate, reproductive rate, locomotor speed, all these things are intertwined in interesting ways.
38:56 Kelly Weinersmith? It depends. Okay, so you can't replicate too quickly because you might get cancer. If you start growing your bones or your muscles too fast, is there ever a trade off with like the quality of what you're producing? Like if you make bone really quickly or muscle really quickly, is it more likely to tear or to break?
39:14 Speaker 02 Oh, definitely. Yeah. So bone is a wonderful example that bone takes time to mature. You have to produce like in our in our leg bones, we have to produce a cartilage model first with living cells. And then gradually those cells are replaced by mineral that gets laid down by other cells. And so it takes time to produce the mineral of our bone that that forms the supportive network. That cartilage gradually goes away. And when we go from a pretty squishy, flexible, but living structure made of cartilage. To a structure that's mostly made of nonliving, but very strong, stiff, supportive mineral.
39:54 Speaker 02 So yeah, you couldn't lay down a bone very, very quickly as, as a mineral substance. You need that time to construct the cartilage.
40:03 Daniel Whiteson? It's like cheese. You can make like a really soft, fresh cheese, but you want like a nice, hard Parmesan, like that takes years in an Italian cave, doesn't it?
40:14 Speaker 02 Patience pays off. Another thing that's important is, uh, different rates of growth of organs. So organs will, will grow at different rates depending on what they are and what they need to be in the adult organism. And different molecules govern the rate of growth. So like liver growth is regulated by bile acid flux. Uh, so the bile that, you know, the liver is very well known for, for using helps regulate, uh, how quickly the liver grows. And in every, every different organ, there are different things that, that regulate it. And the size of the organ at different points in, in the life cycle will be relatively different depending on how quickly it's growing.
40:59 Kelly Weinersmith? I'm always amazed that the liver grows back at all and that they can do like surgeries where you get a little bit of somebody's liver. I had always assumed that the liver was like a thing that was made and then would not grow anymore. But bodies are amazing.
41:12 Speaker 02 They sure are. Yeah. And by tweaking those growth rates of organs, you can get really interesting changes of organisms. So you can get bigger hands or longer limbs or whatever by tweaking differential growth of body parts.
41:26 Kelly Weinersmith? Do we know if any of these rules that we've talked about apply to plants as well? Or is that just like a totally different game?
41:33 Speaker 02 Oh yeah. A lot of those rules would, uh, apply to plants as well. Definitely like the DNA repair stuff, metabolic rate, all that stuff. Stuff. I guess the one thing that wouldn't apply is is how fast plants can run because yeah, they do things differently.
41:50 Daniel Whiteson? Basically, still zero. It also applies to dairy products, right? If you take, for example, yogurt and you put it in milk, it makes more yogurt, just the same way the liver grows. Here, I'm really leaning on my ninth grade biology.
42:03 Kelly Weinersmith? Are you hungry today also?
42:06 Speaker 02 Tumbleweeds might argue with you in terms of the the plant locomotion thing, but but they're cheating. Yeah, they're cheating.
42:15 Kelly Weinersmith? Are tumble? I thought tumbleweeds were just like dead plants that sort of accumulated and then blew across the the desert or whatever. Are they alive still?
42:26 Speaker 02 I'm sure there's something alive in there, like their seeds, but I was I was joking. I mean, just when you mentioned plants and and movement, I immediately an image of tumbleweeds jumped into my mind and yeah, I mean, there are plants that move, but just slowly.
42:44 Kelly Weinersmith? You could like literally tell me almost anything about plants. And as long as you had a straight face, I would believe it. Because plants can do so many things that blow my mind. Like, you know, we were, we had a an episode a while back about a plant that like if, you know, if a branch touches the ground again, it will root. And then if you cut it, it will produce a new tree. And I'm like, no, no, no, no, that's not how animals work. That can't be how anything works. And anyway, I'm very animal centric. Plants, uh, plants seem to break all the rules that seem seem logical to me.
43:13 Speaker 02 Yeah, I try to remain humble as a trained zoologist, reminding myself that fungi and plants and other non animals can do very cool stuff that we shouldn't let our animal bias leave us ignorant of.
43:26 Kelly Weinersmith? Yeah, I'm way less excited about hugging fungi and plants, but yeah, they still do some fascinating things. I've got one last question about sharks. So you mentioned that when we're building bone, that takes a long time, but sharks are mostly cartilage instead of bone. So can sharks grow much faster than the rest of us?
43:45 Speaker 02 I don't know that that's true, that sharks can grow faster. I do know of some studies looking into sharks not having as much cancer. At least some sharks and there's. Like recently in the news over the past decade or so, there's been a lot of interest in in these Greenland sharks that can get pretty big. These are sharks that range into kind of Arctic waters. They can get quite big, but also it's been realized they can perhaps live as long as 500 years or something like that.
44:22 Kelly Weinersmith? Wow.
44:22 Speaker 02 And presumably they're growing very slowly during that time. But also it seems like they they and I think if I remember correctly and and other sharks just don't get a lot of cancer.
44:36 Kelly Weinersmith? I feel like that would be hard to confirm because we just, I mean, we don't watch sharks for that long, but I guess we've dissected and eaten a lot of sharks. So we probably would have seen plenty of cancer if they got a lot of cancer.
44:49 Speaker 02 Yeah.
44:50 Kelly Weinersmith? I thought you were going to tell me that I was wrong about sharks being made mostly of cartilage and I was going to be super embarrassed, but then you said that, no, they don't grow that fast. So anyway, big relief for me here.
45:00 Speaker 02 But also sharks have calcified cartilage that forms a lot of their stiff supportive network. So they do lay down mineral.
45:08 Kelly Weinersmith? Oh.
45:09 Speaker 02 But still, it's it's a lot more living material than than in a typical bony fish.
45:15 Kelly Weinersmith? Okay.
45:16 Daniel Whiteson? 500 years is a lot older than the oldest Parmesan I'm aware of. So in the shark versus Parmesan competition, it sounds like sharks are winning for those keeping score at home.
45:26 Speaker 02 We need to crack open some ceramics in Pompeii and see if there's like any, any cheese still in there.
45:35 Daniel Whiteson? And on the cheese topic, I will say the cheese are very fast. You ever seen the cheese roll in Scotland where they roll a cheese down the hill and then people roll down trying to chase it? Nobody ever catches that cheese.
45:46 Speaker 02 Yeah, yeah. You went again, gravity, unfortunately.
45:52 Daniel Whiteson? I just want to make sure we're asking John questions he hasn't prepared for.
45:56 Kelly Weinersmith? That's, that's great. That's great.
45:58 Speaker 02 I've never witnessed the rolling cheese. I think I've seen cartoons of it. Maybe it was in the.
46:02 Kelly Weinersmith? Simpsons or something like that. I don't know.
46:06 Kelly Weinersmith? A cultural touch point for sure. Yes. All right. Aaron, what did you have to say? Hey, Daniel and Kelly. Thanks for answering my question about growth. I tried not to take it personally when your guest claimed that, quote, metabolism is a fundamentally wasteful process. As my kids say, stop body shaming. Also, a little digging on my own uncovered a somewhat unbelievable fact that a blue whale calf can add up to 200 pounds of body weight, which is about the equivalent of one xenomorph per day. Let's just hope that DNA repair process is keeping up. Thanks again, Aaron.
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49:51 Kelly Weinersmith? All right, this last question has a little bit of something for everyone, a little bit of biology, a little bit of physics. So Daniel will step in here, too. So Rosalyn wanted to know. I was thinking about the relationship between space and time. And I was wondering if there's a correlation.
50:10 Speaker 05 Between all of that and the experience in time scale of creatures. So like, do smaller animals have shorter lives because they experience time at a faster pace than those of us who are bigger, taller, and further away from the impact of spacetime curvature? Or are they just similar but not at all related to each other? Thanks.
50:36 Kelly Weinersmith? So we're gonna have part of this question go to Daniel and then part of this question, I would love to know more about how size impacts lifespan. So first of all, Daniel, is spacetime curvature impacting the lifespan of organisms?
50:51 Daniel Whiteson? Absolutely it is.
50:52 Kelly Weinersmith? What?
50:53 Daniel Whiteson? But probably not in a way that we can really measure.
50:56 Kelly Weinersmith? Oh.
50:56 Daniel Whiteson? You know, spacetime curvature is how space responds to mass. And when there's a lot of mass or energy density around, clocks tick more slowly. So clocks in the surface of the earth tick slower than clocks out in space. Clocks near a black hole tick very, very slowly. So the fact that we're all here on earth means that our biological clocks tick more slowly. And that's also true for the whole universe. Parts of the universe that are far from black holes would have clocks that tick more times since the big bang than clocks that are near black holes. And so in that sense, even the universe, you can't say has a single age. It depends on where you are in space.
51:39 Daniel Whiteson? So if you have a creature and it has a lot of mass, it's a blue whale, there's gonna be a little bit more energy density there, which means its clocks will tick more slowly. Is that measurable? Almost certainly not, because the amount of mass necessary to make clocks tick more slowly is really large. Even clocks on the surface of the earth, because of the earth's enormous mass, take just barely more slowly than clocks in orbit. So even a blue whale is not gonna measurably affect clocks, but technically it does happen.
52:11 Kelly Weinersmith? So you're saying it experiences more time because its clock is ticking more slowly and therefore it lives longer? Is that the? Because when you kept saying clocks tick more slowly, I keep thinking, do you mean like their heart beats more slowly? But no, you mean like the amount of time it's experiencing.
52:27 Daniel Whiteson? I mean, its clock beats more slowly from somebody from the outside. So we see it living in slow motion. So it's younger, right, than we would be. And it sees our clocks moving at high speed. So it sees the rest of the universe as like operating on fast forward. So it lives longer according to our clocks because it's living in slow motion. Does that make sense?
52:50 Kelly Weinersmith? Yes, but at such a negligible difference.
52:54 Daniel Whiteson? Yeah.
52:55 Kelly Weinersmith? Because blue whales are huge but small relative to the size of the universe or something, right?
53:00 Daniel Whiteson? That's right. But if you have aliens who have masses of a star or something, then this could be a real factor.
53:07 Speaker 02 That's what I was gonna go to because everything matters in a xenomorph universe frame of reference. We always have to take our biology to that. So yeah, a star sized organism would would perceive our time as very different from the time it was living in. And we need more science fiction about that.
53:26 Daniel Whiteson? We definitely do.
53:28 Kelly Weinersmith? Yeah. So are you saying then that an alien that was so big it was the size of the sun would experience time more slowly and thus live longer than the rest of us?
53:39 Daniel Whiteson? Yes, it would see us die off more quickly because our clocks tick faster than its clocks.
53:46 Kelly Weinersmith? Wow.
53:46 Daniel Whiteson? Yeah.
53:46 Speaker 02 Yeah. So there's that Star Trek movie where they where they met like some sort of huge thing that was God or thought it was God. Remember which movie that was like it was Final Frontier or something like that? Oh, anyway, they blew up God. So it was all fine in the end.
54:06 Kelly Weinersmith? I thought Star Trek was supposed to be the like the nice version of the sci fi worlds, the one where they weren't like nice to other creatures.
54:12 Speaker 02 I think it was a naughty God or thought it was a God and it was naughty. So it had to get proton torpedoed or whatever they did to it.
54:20 Kelly Weinersmith? Got it. Got what was coming to him.
54:21 Speaker 02 Yeah.
54:22 Kelly Weinersmith? All right. Well, I really like the biology answers because the physics answers kind of break my brain, but they're amazing. But let's get a different perspective. So how does size impact lifespan? When the framing is biology, John?
54:36 Speaker 02 I think there it's simpler, which is nice because biology is often so messy. Oh, maybe it's not simpler, but it's simple. There's a direct relationship between size and lifespan in organisms. Generally speaking, bigger things live longer and growth rate is involved there. Metabolic rate is involved there, all this stuff that we talked about earlier. So bigger things take longer to become big, but still they can get bigger as long as they have enough resources to do so. And that's basically it, that we don't see a lot of small things at all that live very long. If you think about a mouse, it's lucky to live maybe a year. I don't know if kids have ant farms anymore, do they?
55:22 Kelly Weinersmith? I don't see them flying off the shelves at science museums, but I still, I still see them sold at science museums.
55:29 Speaker 02 I really, I really have deep hope that, that kids still like ant farms and maybe like them more than YouTube or TikTok. But, but anyway, I mean, if you have an ant farm, you'll, you'll notice that ants die pretty quickly. And, and other small things die quickly. And if we go down to the bacteria level, they're dropping dead like crazy. So there's a very strong relationship between size and lifespan across biology.
55:56 Daniel Whiteson? And I remember hearing this sort of simplistic explanation that it was again about metabolism.
56:02 Speaker 02 Yeah.
56:02 Daniel Whiteson? That larger animals have a slower metabolism and a slower heart rate.
56:06 Speaker 02 Yeah.
56:06 Daniel Whiteson? And that like mice and elephants live the same number of heartbeats, but that mice just have their hearts beating faster. And so fewer ticks on the clock. Is that true? Or my, is my biology wrong?
56:18 Speaker 02 I think the heart rate thing is very, very, very coarsely true. And that would only apply to organisms that have hearts, but I mean, that applies to. A lot of animals. But yeah, I mean, growth rate, metabolic rate, all that stuff is tied into lifespan pretty tightly. But a neat thing that ties into this kind of concept of biological time is that small organisms are vulnerable. So they tend to have high metabolic rates. So they can get to a size where they're able to do all their adult stuff quickly enough. And that's that relationship of size and vulnerability and metabolic rate has evolved.
56:59 Speaker 02 There's selection for small things to have high metabolic rates and grow quickly. And also there's selection for lifespan to be short. Because if lifespan is shorter, then organisms can reproduce themselves more quickly. The greater your size is, it's probably likely that your reproductive rate is going to be slower. Otherwise, the earth would be covered in whales.
57:28 Speaker 02 So there is again, this this correlation between growth rate, reproductive rate, metabolic rate.
57:34 Daniel Whiteson? Yeah.
57:35 Speaker 02 And then size and lifespan, these things are all tied together. And then over deep time, over evolution, there are trade offs that things that are big go extinct more often. And speciate create new species less often. So as long as the environment is pretty stable, big things do okay. There tends to be an increase in the number of big bodied adult species over time. But as soon as the environment changes, kaboom, they go extinct. And that's why we see these mass extinction pulses is because of especially rapid environmental change. Is something that big organisms cannot adapt to. They go extinct more quickly, they speciate more slowly.
58:20 Speaker 02 And therefore there are less big things in a rapidly changing environment. And mass extinctions tend to to hit the bigger things harder.
58:30 Daniel Whiteson? What a cool experiment we could do to test that, which is like land on a bunch of exoplanets. And understand the relative stability of those ecosystems and see if the ones with more stable ecosystems really do have more big land animals. That would be crazy.
58:46 Speaker 02 Unfortunately, to bring us back to reality, we're doing that experiment right now with. Climate change in a way that's never happened before. Even the asteroid that hit Earth. It did its share of devastation 66 million years ago, wiping out the Mesozoic dinosaurs and many other things. There was clear size selection going on, but some of the extinction patterns happened over thousands of years. Whereas right now, the stuff we're doing over the scale of decades is is pretty unprecedented in terms of extinction and we're having a huge bias toward getting rid of of big things because of loss of habitat and hunting and so on and so forth. That always hits the big things quicker.
59:30 Speaker 02 And that's followed on from an ice age just, you know, 10,000 years ago that again wiped out a lot of the megafauna. So, yeah, that's our experiment.
59:41 Daniel Whiteson? It's hard for ecosystems to respond in the time scale of like a Parmesan rather than like geological time scales.
59:47 Speaker 02 Yes, yes. Again, bringing it back to the cheese frame of reference.
59:53 Speaker 02 We got the xenomorph frame of reference and the cheese frame of reference and that's all you need for a podcast.
59:59 Kelly Weinersmith? That's right. We got the two important frames of reference.
1:00:02 Daniel Whiteson? And I have the mental image of an ocean stocked filled with whales, overflowing with whales, all of them eating a wheel of Parmesan.
1:00:10 Speaker 02 Okay, I thought you'd bring the cheese in there. That's great.
1:00:14 Daniel Whiteson? I'm nothing if not predictable.
1:00:19 Kelly Weinersmith? Before we go to Rosalyn, do you want to tell us what you've been up to and give us a quick update on the cool stuff you've been doing since we last chatted?
1:00:28 Speaker 02 What have I been doing? I've been studying crocodiles a lot, both living ones and extinct ones. How they move, how their movement has evolved. That's a big focus of mine lately. With various postdoctoral researchers and PhD students and master's students and undergrads. So that's been a lot of fun trying to unravel the history of crocodiles and how they move in more detail because they started off as wonderful, small, kind of cat sized, quick animals and then evolved into the Diversity of different forms that ultimately got wiped out by that mass extinction at the end of the Cretaceous, leaving just the crocodiles and alligators that we're familiar with.
1:01:11 Speaker 02 So there was a great diversity of crocodiles back in the Mesozoic that we can't really appreciate from a modern perspective of the 25, 28 species of all fairly similar crocodilians. Whereas back 230 million years ago, there are these really amazing, more mammal-like crocodiles, and then later, things like whale-like crocodiles and, yeah, crazy, crazy kinds of ecologies and body plans and locomotor styles of crocodiles over their, over their heyday. So that's, I'm doing a lot about that. That's keeping me very busy.
1:01:47 Kelly Weinersmith? Cool. You know, crocodiles also have very fascinating parasites, which you can, you know, keep your eyes open for. Haley Dutton recently described a new parasite from the eye of a crocodile, and she named it, she got to name the whole genus, and she named it later gator, which I thought was, was fun and rolls off the tongue. So anyway, keep your eyes open for fun parasites, including parasites on their eyes.
1:02:11 Speaker 02 That's why they have crocodile tears. It's all the parasites.
1:02:16 Kelly Weinersmith? Yeah, perhaps. Do you make sure that their, like, mouths are held shut in some way before you are measuring them, or?
1:02:25 Speaker 02 Oh, yeah. So when I work with live crocodiles, which I've done a fair amount for health and safety reasons, you do have to worry about the bitey end and the, and the tail. The tail end too, because the tail's also a weapon. But the bitey end's worse. And luckily, while crocodile jaw closing muscles are very strong, if you ever look at the back of the head of a crocodile, it looks like they have fatty jowls, especially if the crocodile is lying down. That's not fat. That's not jowls. That's jaw closing muscle.
1:02:57 Kelly Weinersmith? Wow.
1:02:58 Speaker 02 It's, it's real meaty muscle. And so they have the greatest bite force of organisms in absolute terms. They can bite extremely hard, but their jaw opening muscles are weak. So if you close a crocodile's mouth, it's not so good at opening the mouth again. So what we do is close the crocodile's mouth by restraining it and then put electrical tape around the mouth, and that's Enough to secure the the snout shut so it can't bite anyone. They still have teeth that stick out, so um the jaws still have sharp bits on the end that you have to watch for, but still, that's a lot, a lot better than getting bitten by one, because even a small crocodile can really hurt you.
1:03:41 Kelly Weinersmith? All right, well, that's intense, and hopefully you'll come back on the show in the future and tell us more about what you've learned about crocodiles.
1:03:47 Speaker 02 I'd love to.
1:03:48 Kelly Weinersmith? Awesome. We're gonna send this answer to Rosalyn and see what she had to say.
1:03:52 Speaker 05 Hi, Daniel and Kelly. Thanks for answering my question. It makes a lot of sense. It has more to do with biology than space and time. I was up very late that night reading a lot of ancient philosophers, and they had some really big ideas about the universe and nature, and it just kind of got me into thinking. Thanks for bringing it back a little bit closer to home. Biology makes sense. I appreciate you.
1:04:19 Daniel Whiteson? Thanks, everybody, for listening. Please go and do us a favor and rate the show on whatever podcast app you're using. It really helps people find us.
1:04:27 Kelly Weinersmith? Daniel and Kelly's extraordinary universe is edited by the amazing Matt Kesselman.
1:04:32 Daniel Whiteson? He really is a wizard. You can also find us online on Blue Sky, Instagram, and X, D and K Universe. Come engage with us.
1:04:42 Kelly Weinersmith? You can email us at questions at danielandkelly.org. We really do want to hear from you.
1:04:47 Daniel Whiteson? And you can find our website, www.danielandkelly.org, where you'll also find an invitation to join our Discord, where everybody comes and talks about the amazing universe.
1:04:59 Kelly Weinersmith? And we also have the most amazing moderators. This is an iHeart Podcast. Thanks for joining us.
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1:06:44 Speaker 04 How do you know that Claude won't become manipulative?
1:06:49 Speaker 05 This is a constant worry.
1:06:51 Speaker 02 And you can actually catch the model thinking, I think X is actually true, but I'm going to tell the user Y.
1:06:57 Speaker 04 I'm Walter Isaacson. On my new podcast, The Builders, I'm going inside the minds of the people shaping our future. Listen to The Builders starting October 13th on the iHeart Radio app, Apple Podcasts, or wherever you get your podcasts.
1:07:14 Speaker 04 This is an iHeart Podcast. Guaranteed human.
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