Latest / Daniel and Kelly’s Extraordinary Universe / Listener Questions #44 - How fast can animals go, and how fast can animals grow? (featuring Dr. John Hutchinson)

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Listener Questions #44 - How fast can animals go, and how fast can animals grow? (featuring Dr. John Hutchinson) · Daniel and Kelly’s Extraordinary Universe

0:07
Speaker 1: If humans ran as many body lengths per second as
0:10
Speaker 1: a mite, we generate a sonic boom. What are the
0:14
Speaker 1: factors that determine how fast a critter can go zoom?
0:18
Speaker 2: Creatures in movies grow too fast. Grelins and aliens just
0:22
Speaker 2: aren't plausible. But let's do a thought experiment. Could you
0:26
Speaker 2: design a creature to grow as fast as possible?
0:30
Speaker 1: Do smaller animals have shorter lives because of the curve
0:33
Speaker 1: of space and time? And if they lived long enough,
0:36
Speaker 1: would Daniel and Kelly ever get good with rhyme?
0:40
Speaker 2: No?
0:41
Speaker 1: No from salt.
0:44
Speaker 2: But whatever questions keep you up at night, Daniel and
0:47
Speaker 2: Kelly's answers will make it all right.
0:49
Speaker 1: Welcome to Listener Questions, episode forty four, featuring doctor John Hutchinson.
1:07
Speaker 3: Hi.
1:07
Speaker 2: I'm Daniel. I'm a particle physicist who likes to think
1:10
Speaker 2: about aliens, and I'm still growing in all the wrong directions.
1:15
Speaker 1: Same. Hi, I'm Kelly Winersmith. I study parasites and space,
1:19
Speaker 1: and I've never been fast. No one has ever said,
1:23
Speaker 1: will Kelly break a speed record? The answer is no.
1:27
Speaker 2: I'm also not very fast, and my wife she's fit.
1:30
Speaker 2: But these of us are speed demons. However, we somehow
1:34
Speaker 2: birthed a child who is very athletic and is now
1:37
Speaker 2: like running in college, and I don't know what happened.
1:41
Speaker 2: Cosmic ray mutations swap at the hospital.
1:44
Speaker 1: Sometime biology is really complicated, and life tells us that.
1:50
Speaker 2: Exactly will your kid be like you? It depends?
1:53
Speaker 1: It depends, And you hope not for their sake. For
1:58
Speaker 1: their sake, I.
2:00
Speaker 2: Hope they get all the best of you and all
2:01
Speaker 2: the best of your partner.
2:03
Speaker 1: That's right.
2:03
Speaker 2: And today we're going to be marrying our knowledge with
2:07
Speaker 2: the knowledge of doctor John Hutchinson, who knows a lot
2:09
Speaker 2: more about evolutionary biomechanics than we do.
2:12
Speaker 1: So let's waste no time and get John back on
2:15
Speaker 1: the show. Doctor John Hutchinson is a professor of evolutionary
2:19
Speaker 1: biomechanics and a Fellow of the Royal Society. His research
2:22
Speaker 1: straddles the fields of evolutionary biology and biomechanics, with an
2:26
Speaker 1: emphasis on how very large animals stand and move and
2:29
Speaker 1: how locomotion evolved in different groups of land vertebrates. And
2:33
Speaker 1: at the end of this episode, you're no doubt going
2:35
Speaker 1: to be thinking how can I get more of John?
2:37
Speaker 1: And the answer is you can listen to our April
2:40
Speaker 1: twenty ninth, twenty twenty five episode where the title was
2:43
Speaker 1: was the Tyrannosaurus Rex Fast or Slow. Because this is
2:46
Speaker 1: John's second time on the show, and so you can
2:49
Speaker 1: go back and enjoy that episode.
2:50
Speaker 3: Welcome back, John, Thank you, great to be back.
2:53
Speaker 1: We're excited to have you. We had a ton of
2:54
Speaker 1: fun last time.
2:56
Speaker 2: Your expertise spans our audience's interest because we're talking about biology,
3:01
Speaker 2: since these are critters, but we're talking about the physics
3:03
Speaker 2: that makes them move fast or slow. So you're like
3:06
Speaker 2: the perfect guest for the podcast.
3:08
Speaker 3: Oh, I can't claim to be a physicist, but I
3:11
Speaker 3: understand what I need to understand for understanding a bit
3:14
Speaker 3: of biology. That's good.
3:16
Speaker 1: Well, then let's just jump right in. So our first
3:18
Speaker 1: question of the day is from Matt McCain. He's one
3:21
Speaker 1: of our Discord moderators. He asked this question, yay, Mat,
3:24
Speaker 1: yeay Matt. And he asked this question like a million
3:27
Speaker 1: years ago. And every time I pulled up a paper,
3:29
Speaker 1: there were loads of equations, and it was in physics
3:32
Speaker 1: related journals, and so I kept putting aside and quitting
3:35
Speaker 1: on it, and then eventually I realized, why don't I dress.
3:39
Speaker 4: John, Hey, Daniel and Kelly, your friendly neighborhood moderator Matt
3:43
Speaker 4: here I recently went down a rabbit hole of how
3:46
Speaker 4: fast certain critters move, and then that led to a
3:49
Speaker 4: cascade of questions. So I heard about the tiger beetle
3:52
Speaker 4: moving so fast they can temporarily go blind, like their
3:56
Speaker 4: eyes can't take in enough photons to form an image
3:58
Speaker 4: while they're cruising along. So that's kind of weird due
4:02
Speaker 4: to their tiny size, though bugs can't really scale up,
4:05
Speaker 4: but if we did, I was wondering if we could
4:07
Speaker 4: compare and figure out what the fastest animal is relative
4:10
Speaker 4: to size. I'm not sure if that even is scalable,
4:13
Speaker 4: and we often hear trivia about birds and other critters
4:16
Speaker 4: being some of the fastest in the world, and then
4:18
Speaker 4: that led to me finding out they sometimes measure speed
4:20
Speaker 4: in body lengths per second. Currently, the almost unpronounceable Partersotomus
4:26
Speaker 4: might is the raining champ at about three hundred and
4:29
Speaker 4: two body links per second, which would be like a
4:32
Speaker 4: human equivalent running at over thirteen hundred miles per hour.
4:36
Speaker 4: That's kind of fast. Coming in at mock one point
4:39
Speaker 4: seven sonic boom. Human territory help me out, John, Yeah.
4:44
Speaker 3: Well, if I could tackle the tiger beetle first, because
4:48
Speaker 3: I think that's an interesting case.
4:50
Speaker 1: Great.
4:50
Speaker 3: What I think the scientific understanding is that they don't
4:54
Speaker 3: go blind if they go too fast, not quite, They're
5:00
Speaker 3: to chase down prey. Depends on the contrast of the
5:04
Speaker 3: prey to the environment. So if it's like the best case,
5:07
Speaker 3: like a black insect on a white background, then they
5:10
Speaker 3: can see it better. And as they go faster and faster,
5:13
Speaker 3: their contrast blurs. Their visual contrast blurs, so they have
5:19
Speaker 3: to stop periodically if the contrast is poor versus how
5:22
Speaker 3: quickly they're going.
5:24
Speaker 2: Why does their contrast blur? Is this something to do
5:27
Speaker 2: with the response of the proteins how quickly they can
5:29
Speaker 2: recover this?
5:30
Speaker 3: This is a visual limit that their nervous system can
5:34
Speaker 3: only process and adjust to the visual information based on
5:39
Speaker 3: the contrast. If it's coming through it in good enough
5:42
Speaker 3: quality at good enough of a rate.
5:45
Speaker 2: But why does the relative velocity of the object change that,
5:49
Speaker 2: like if it's moving across your field. I guess it's
5:51
Speaker 2: a question of like how quickly the neurons can update.
5:55
Speaker 3: Yeah, so I mean if you can imagine a really
5:59
Speaker 3: quick movement or or really slow camera, there will be
6:03
Speaker 3: blur with that, so you can't really adequately visualize that,
6:07
Speaker 3: and so your nervous system's perception of where the object
6:11
Speaker 3: actually is in space will be increasingly imprecise visually based
6:15
Speaker 3: on how fast the object is.
6:18
Speaker 2: Let me just make sure I understand. So you're saying,
6:21
Speaker 2: if we think about the eye as a camera, it's
6:23
Speaker 2: got a shutter speed, and just like something that's zooming
6:26
Speaker 2: through your field faster than the update speed, then the
6:30
Speaker 2: shutter speed is going to create an image that's smeared
6:33
Speaker 2: across your field because the eye is accumulating data over
6:37
Speaker 2: that time period and so it ends up smeared. Is
6:40
Speaker 2: that a fair analogy.
6:42
Speaker 3: That's my understanding of it. And I don't know exactly
6:45
Speaker 3: how the tiger beetles visualize objects, but my understanding is
6:50
Speaker 3: that it's really a matter of the contrast of the
6:54
Speaker 3: object that is a big, big factor, and their prey contrast.
6:58
Speaker 3: How dark the prey is relative to the environment and
7:01
Speaker 3: so forth will vary a lot depending on the prey
7:04
Speaker 3: and the environment.
7:05
Speaker 1: So do they tend to go after really like snazzy,
7:08
Speaker 1: brightly colored, flashy prey then to try to make it
7:11
Speaker 1: easier to see them.
7:12
Speaker 3: That I don't know, and there might be really counterintuitive
7:17
Speaker 3: issues like I don't know exactly how tiger beetles see.
7:21
Speaker 3: Do they have any spectra of the light spectrum that
7:25
Speaker 3: they see differently from us, like ultraviolet or whatever, I
7:29
Speaker 3: don't know, Or do their prey respond to light differently visually? Yeah, oh,
7:35
Speaker 3: I'm know entomologists. I can't can't answer that question.
7:39
Speaker 1: I'm going to go on a flashy food diet. I
7:41
Speaker 1: only eat food that is highly contrasting and blings a
7:44
Speaker 1: lot relative to the environment.
7:46
Speaker 2: I only eat slow food, things that sit on my
7:48
Speaker 2: plate and have a very low velocity relative to me.
7:50
Speaker 3: Okay, I'm all more ol factory.
7:54
Speaker 2: I think the slow food movement means something else.
7:56
Speaker 1: But I think all factories probably way to go. You
8:00
Speaker 1: might enjoy your food more more than the rest of us.
8:04
Speaker 2: I like eating at the old factory spaghetti factory.
8:08
Speaker 1: Okay, we've got a bit caught up on the vision thing.
8:13
Speaker 1: I have a friend who studies tiger beetles, and he
8:15
Speaker 1: tells me that they're the fastest animals on the planet,
8:19
Speaker 1: and he's right about most things. But your face suggests
8:23
Speaker 1: to me that maybe this isn't one of them.
8:25
Speaker 3: Well, they're pretty damn fast, and the person asking the
8:30
Speaker 3: question is correct. For their size, they're pretty crazy fast.
8:34
Speaker 3: And that's true of a lot of small things. If
8:36
Speaker 3: you normalize, if you divide speed by by body length,
8:40
Speaker 3: small animals are always going to be fast unless they're
8:42
Speaker 3: really slow small animals, like a tick or something like that.
8:46
Speaker 1: So does that suggest that's not the best way to
8:49
Speaker 1: measure it then, because it's a biases towards small animals.
8:52
Speaker 3: Well, I think it reveals something about the fundamental nature
8:55
Speaker 3: of speed that speed limits on animals are are very
9:01
Speaker 3: different depending on the size. There's fundamentally different physical laws
9:06
Speaker 3: if you will that influence how small animals are limited
9:10
Speaker 3: in their speed versus how large animals are limited in
9:13
Speaker 3: their speed.
9:14
Speaker 1: How will do we understand those laws? Is that like
9:16
Speaker 1: something that's easily articulated.
9:18
Speaker 3: Yes, pretty well, we understand pretty well. The overall gestalt
9:24
Speaker 3: of what limits animal speed, So smaller animals, the smaller
9:29
Speaker 3: that animals are, the more that the power of their muscles,
9:35
Speaker 3: So how much force the muscle can produce and how
9:38
Speaker 3: quickly they can produce it, that becomes really limiting on
9:42
Speaker 3: speeds They have to have really quick muscle there's a
9:45
Speaker 3: big contrast with that and big animals where it's not
9:49
Speaker 3: so much the power, like the rate of doing energy
9:54
Speaker 3: or work with the muscles. That doesn't matter so much
9:57
Speaker 3: as just the amount of force that themuscles can generate
10:01
Speaker 3: and the amount of distance those muscles can move the
10:04
Speaker 3: body over, which is force. Time's distance is work. That's
10:08
Speaker 3: the energy of the animals. So rate is not so
10:12
Speaker 3: important for big animals in limiting speed. They don't have
10:16
Speaker 3: to produce force very quickly. They have to produce a
10:19
Speaker 3: lot of force basically, So gravity ultimately limits big animals
10:24
Speaker 3: more than smaller animals. And that's why, for example, it's
10:28
Speaker 3: very well known like ants can carry many, many times
10:30
Speaker 3: their body weight, and that's because gravity just doesn't limit
10:34
Speaker 3: them so much at all. Their strength to weight ratio,
10:37
Speaker 3: which is a fundamental aspect of biology, is extremely high.
10:41
Speaker 3: And that's true of pretty much all organisms. That the
10:45
Speaker 3: smaller they are, the stronger they are relative to their weight.
10:49
Speaker 2: And is that just because of geometry, and that the
10:51
Speaker 2: strength depends on the cross sectional area of your bones
10:54
Speaker 2: and your muscles, and that grows by like length squared,
10:58
Speaker 2: whereas your weight depends on your volume, which grows like
11:01
Speaker 2: length cubed exactly.
11:03
Speaker 3: That's the square cube laws. So that governs a huge
11:07
Speaker 3: amount of biology that we can understand how size influences
11:12
Speaker 3: organismal biology by understanding how things like length and area
11:17
Speaker 3: scale with body weight and how other things change with
11:20
Speaker 3: body weight.
11:21
Speaker 2: And so if we were like on Mars with lower gravity,
11:25
Speaker 2: we might expect like bigger ants.
11:27
Speaker 3: Oh so limits on size, Yes, yes, that is true,
11:32
Speaker 3: although would depend on other factors like oxygen.
11:36
Speaker 2: Right, of course, I wasn't suggesting there literally are huge
11:39
Speaker 2: ants on Mars, so I would love that. I guess
11:42
Speaker 2: I was just more thinking about like alien environments with
11:46
Speaker 2: different gravity, but there would be a different range of
11:49
Speaker 2: what you call small or large creatures.
11:51
Speaker 3: It sounds like, oh yeah, I mean that's a given. Definitely, definitely,
11:55
Speaker 3: at least the potential for that, depending on how long
11:58
Speaker 3: those organisms had been there over evolutionary time.
12:01
Speaker 1: So if you had two animals that were the same
12:07
Speaker 1: kind of the same shape but definitely the same like
12:10
Speaker 1: mass or height. Like, so two animals that kind of
12:13
Speaker 1: looked like deer, but one was much faster than the other,
12:17
Speaker 1: what would be the thing that was different? Would it
12:21
Speaker 1: be the kinds of muscles they have, or the way
12:22
Speaker 1: they attached to their bones. I didn't completely get that
12:25
Speaker 1: in my head.
12:26
Speaker 3: Probably the biggest difference would be how muscular they were
12:30
Speaker 3: a relative to their size. So they were they really
12:33
Speaker 3: really like Usain Bolt, really really jacked, or were they
12:38
Speaker 3: built more like a marathon runner. Pick your favorite marathon runner.
12:42
Speaker 3: I can't think of one at the moment.
12:44
Speaker 1: Okay, So big animals need to have more muscles. And
12:47
Speaker 1: if you have two animals that are like tiger beetle
12:50
Speaker 1: size and one is faster than the other, the difference
12:53
Speaker 1: would be the efficiency of their muscle.
12:56
Speaker 3: Was that right? Well, it might be how quick their
12:58
Speaker 3: muscle could contract or something like that, something that influences
13:01
Speaker 3: their ability to generate a lot of force quickly.
13:06
Speaker 1: Okay, And what's the fastest animal you've studied?
13:10
Speaker 3: So, I mean, I've studied cheetahs, but not really studying
13:14
Speaker 3: them at their top speed. Other people in our lab have.
13:18
Speaker 1: That's actually a great segue into another question, which is
13:21
Speaker 1: if you're trying to measure maximum speed, how can you
13:25
Speaker 1: be sure you're measuring maximum speed? Like, how do you
13:28
Speaker 1: get an animal to go as fast as it can
13:31
Speaker 1: so that you can make these kinds of measurements in
13:32
Speaker 1: the lab, because that sounds kind of complicated.
13:34
Speaker 3: Yeah, that's always the fundamental challenge, and that's why model organisms,
13:40
Speaker 3: organisms that we can really understand well, like well, humans
13:44
Speaker 3: are a great model organism because they can tell us
13:47
Speaker 3: what's going on. We can tell them what to do
13:48
Speaker 3: and they'll do it, so we can we can get
13:50
Speaker 3: a good measurement of human maximal speed and so that's
13:54
Speaker 3: around eleven twelve meters per second for the best sprinters.
13:59
Speaker 3: But other things have to be cooperative. So you can
14:03
Speaker 3: get a dog on a treadmill, a horse on a
14:06
Speaker 3: treadmill or something like that and get them to run
14:09
Speaker 3: as quickly as they can, either on a treadmill or
14:11
Speaker 3: a race course, and there you can be pretty confident
14:14
Speaker 3: that because they're trained to race, to go as fast
14:17
Speaker 3: as they can more or less, then they're going to
14:20
Speaker 3: give you their maximal speed. But if you're studying an elephant,
14:24
Speaker 3: as I did, you may not get them to go
14:28
Speaker 3: very fast. Motivations are big issue. So I studied elephants
14:32
Speaker 3: in zoos starting off and found that they were pretty
14:34
Speaker 3: slow in zoos, unsurprisingly, because it's hard to motivate them.
14:38
Speaker 3: They don't have a lot of space. So for so
14:40
Speaker 3: I went to Thailand. I studied elephants there that are
14:43
Speaker 3: used in races periodically, and they were way faster than
14:49
Speaker 3: like a western zoo elephants on average.
14:52
Speaker 2: So what motivates an elephant? How do they make the
14:54
Speaker 2: elephant run?
14:56
Speaker 3: It varies, so sometimes cheering for them, sometimes having them
15:00
Speaker 3: chase another elephant or run to a friendly elephant. They're
15:05
Speaker 3: smart animals. You have to kind of work around them
15:08
Speaker 3: and their personality and figure out what will motivate them.
15:11
Speaker 2: Elephants respond to cheering like peer pressure will encourage an elephant,
15:15
Speaker 2: that's the moment.
15:15
Speaker 3: Yeah, they're super smart, super smart social animals. So, and
15:20
Speaker 3: they're bonded with their trainers in Thailand because they grow
15:24
Speaker 3: up together. Literally, the humans, the mahoots as they're called,
15:28
Speaker 3: and the elephants spend their lifetimes growing up together, developing bonds.
15:33
Speaker 3: And that's why they were able to motivate their elephants
15:36
Speaker 3: very well. So by studying lots of elephants over and
15:40
Speaker 3: over and over again, getting them to walk and run
15:42
Speaker 3: at different speeds, we're able to again and again and
15:44
Speaker 3: again get pretty much the same speed out of all
15:47
Speaker 3: the elephants, and that was the fastest ever reliably recorded.
15:51
Speaker 2: Assuming that elephants don't have some secret top gear that
15:54
Speaker 2: they're just not interested in sharing with us humans.
15:58
Speaker 3: Yeah, so then you have to kind of go by
16:00
Speaker 3: extraordinary claims, require extraordinary evidence, and so we need some
16:04
Speaker 3: sort of evidence of that secret gear. Yeah, that's that's
16:08
Speaker 3: special pleading in science or and philosophy of society can't
16:11
Speaker 3: do that. You can't just say, oh, they're just holding back.
16:15
Speaker 3: They could do themar You need some sort of reason
16:19
Speaker 3: for that. But it's definitely true many animals do hold back.
16:23
Speaker 3: So and many estimates of speed that are out there
16:26
Speaker 3: in the scientific literature are wild guesses at best because
16:31
Speaker 3: of the unreliable nature of estimating animal speed. If you
16:35
Speaker 3: just watch an animal moving out in nature, you could
16:39
Speaker 3: easily be off by fifty one hundred percent in your
16:42
Speaker 3: estimate of the speed of the animal because we're not
16:45
Speaker 3: great at estimating speeds.
16:47
Speaker 2: What about scenarios like horses versus buffalo Right there, the
16:52
Speaker 2: buffalo are clearly motivated by survival, especially if there's somebody
16:55
Speaker 2: on horseback shooting at them, and the horses are motivated
16:59
Speaker 2: by the rider who's faster. In that scenario, buffalo or
17:02
Speaker 2: a horse.
17:03
Speaker 3: They're going to be pretty close because their size is
17:05
Speaker 3: pretty similar. They're pretty similar in terms of musculature. But
17:09
Speaker 3: the horse has a slight edge there based on length
17:12
Speaker 3: of the legs and lightness of the feet and so forth.
17:16
Speaker 3: They are a bit more adapted for running quickly. But bison, buffalo,
17:20
Speaker 3: so forth, they can run fast. I mean they're also
17:24
Speaker 3: ungulates to hooked mammals, which in general have very lightweight,
17:29
Speaker 3: long lens that they're able to move quickly and therefore
17:33
Speaker 3: run quickly and efficiently.
17:35
Speaker 2: I don't think of a bison as fast because I
17:37
Speaker 2: think of them in the cow category and they just
17:39
Speaker 2: never really imagine the cow going anywhere quickly. But I've
17:43
Speaker 2: seen buffalo run because they have them at Fermilab. You know,
17:46
Speaker 2: we only need the underground, and so they have a
17:48
Speaker 2: herd of buffalo and yeah, they can move.
17:51
Speaker 3: Yeah. Yeah. It's the cow bias that I think is
17:54
Speaker 3: making us think of less familiar animals as slow. Yeah.
18:00
Speaker 1: So what do we think is the fastest animal? And
18:03
Speaker 1: how confident can we be given how bogus some of
18:06
Speaker 1: these estimates are that we actually know what animal is
18:09
Speaker 1: the fastest?
18:10
Speaker 3: Oh, well, the cheetah on land, and that's the key
18:13
Speaker 3: thing to qualify on land, the cheata is the fastest.
18:16
Speaker 3: There's no question about the prongo or antelope come close.
18:20
Speaker 3: But cheetahs have been reliably measured at around sixty five
18:24
Speaker 3: miles an hour.
18:24
Speaker 1: Yeah, that's pretty impressive, but.
18:26
Speaker 2: That's in the metric of like speed relative to the ground,
18:28
Speaker 2: not in body lengths per second.
18:30
Speaker 3: Yeah, absolute speed is That's what I'm going based on. Yeah.
18:35
Speaker 3: But then yeah, things like the might that the question
18:38
Speaker 3: asker mentioned. Yeah, I mean, if you go down to
18:42
Speaker 3: really tiny size, then body lengths per second is going
18:46
Speaker 3: to give you a faster speed relative to body length
18:50
Speaker 3: for smaller things.
18:52
Speaker 2: And why is the might so fast? Like, why is
18:54
Speaker 2: it so mighty?
18:57
Speaker 3: I think that might be the wrong question. That maybe
18:59
Speaker 3: the matter. It may not matter how fast the might is.
19:03
Speaker 3: I mean where the mites need to go. They're not
19:05
Speaker 3: yet going long distance. They're not what motivates the might
19:08
Speaker 3: avoiding predators that are chasing them in a pursuit kind
19:13
Speaker 3: of situation. They're pretty in general. I mean I can't
19:17
Speaker 3: speak for all mts, but in general, nights are animals
19:22
Speaker 3: that are in hiding a lot of the time and
19:25
Speaker 3: They're not going to be running around like a buffalo
19:28
Speaker 3: is on a on a grassland. Their environment is completely different,
19:32
Speaker 3: much more cluttered. So they're just going from place to
19:36
Speaker 3: place short distances. And that's true of a lot of
19:38
Speaker 3: small animals that if you watch them, they don't move
19:41
Speaker 3: long distances for long periods of time. They use intermittent locomotion.
19:46
Speaker 3: And that's the case of the tiger beel. To circle
19:48
Speaker 3: back to that is that because of their visual blur,
19:51
Speaker 3: they have to stop periodically stop running to re calibrate
19:57
Speaker 3: where the prey is by just reducing that velocity based blur.
20:03
Speaker 3: And so that's the that's their solutions. They slow down
20:05
Speaker 3: or even stop, and lots of small animals do that
20:08
Speaker 3: is slow down, stop, check out the environment, and then
20:12
Speaker 3: pick off a gun if they if they're moving quickly.
20:15
Speaker 1: All right, well, I think it's time to circle back
20:18
Speaker 1: to Matt and see what he has to say about
20:20
Speaker 1: this answer.
20:21
Speaker 4: Oh wow, you guys really brought out the big guns
20:24
Speaker 4: for my question. Thank you Kelly Daniel and doctor John
20:27
Speaker 4: Hutchinson for answering the questions that have been terrorizing my brain.
20:31
Speaker 4: I really was though hoping the tiger beetle gain like
20:34
Speaker 4: some dark sunglasses and like a walking stick when zooming around. Unfortunately, though,
20:39
Speaker 4: as I was leaning, there's really no scaling for a
20:41
Speaker 4: true comparison. And if I think too hard about it, now,
20:44
Speaker 4: a giant tiger beetle sporting some dark sunglasses stopping removing
20:48
Speaker 4: said sunglasses like the dude on CSI to look around
20:51
Speaker 4: for prey sounds kind of terrifying to me. I appreciate
20:54
Speaker 4: all the time and effort you all took to do
20:56
Speaker 4: this deep dive for me, and I'm gonna give a
20:58
Speaker 4: quick plug to come and join and the fun sciencey
21:00
Speaker 4: discussions in our discord. This community is truly amazing. We
21:03
Speaker 4: could always use more pet pictures. Thanks for everyone for
21:06
Speaker 4: being spiffy and awesome see in the discord.
21:08
Speaker 1: All right, that was awesome or was there anything else
21:10
Speaker 1: you wanted to say on that one?
21:11
Speaker 3: John, Well, I'll give a personal interest about speed, and
21:16
Speaker 3: that's if you've ever encountered a Huntsman spider like out
21:19
Speaker 3: in East Asia, Australia so forth, you will be pretty
21:26
Speaker 3: startled by how quickly they can move out phill. These
21:29
Speaker 3: are usually pretty sizable spiders. They're pretty freaky looking. If
21:34
Speaker 3: you have any sort of a rack and aphobia. They
21:37
Speaker 3: got it all. They got the big fang's, long legs,
21:39
Speaker 3: flat bodies, often kind of hairy looking, and they can
21:42
Speaker 3: move blindingly fast. So I went into a hotel in Taiwan,
21:47
Speaker 3: and right away when I checked in, opened a closet
21:49
Speaker 3: and out came a huntsman spider sprinting across my room. Ah,
21:54
Speaker 3: and I couldn't find it, but I had to go
21:55
Speaker 3: out for dinner very shortly thereafterwards, so I had to
21:58
Speaker 3: leave it in my room. I'm not cool with sleeping
22:01
Speaker 3: with spiders. I'm just not down with that. So luckily
22:04
Speaker 3: we made our piece when I got back to the
22:06
Speaker 3: room after dinner, and I was able to sleep without
22:09
Speaker 3: worrying that there was a huntsman spider there. But yeah,
22:12
Speaker 3: they can go three point six meters per second. There's
22:15
Speaker 3: the fastest brown huntsman spider. You know, that's a moderate
22:19
Speaker 3: speed jog for us for a pretty small animal. The
22:22
Speaker 3: brown huntsman Heteropoda servina is the genus and species, so
22:27
Speaker 3: if you're interested in those, they are the fastest reliably
22:30
Speaker 3: recorded spider.
22:32
Speaker 1: I didn't want to know that. I will now live
22:35
Speaker 1: in fear. And then are they venomous?
22:38
Speaker 3: Mildly. They'll hurt a bit if they bite you, but no,
22:41
Speaker 3: they eat bugs and geckos and so forth that their
22:46
Speaker 3: venom is more suited to.
22:48
Speaker 1: They eat geckos. And so when you said we made
22:50
Speaker 1: our piece, does that mean he's now resting in peace?
22:53
Speaker 1: Or how did you make peace with the huntsmen?
22:56
Speaker 3: Oh? Boy, I don't want to go into the details.
22:58
Speaker 1: Yeah, all right, moving on, and we're back, and now
23:21
Speaker 1: we're answering a question from Aaron. Here is Aaron's question
23:24
Speaker 1: about the limits to how fast an organism can grow.
23:28
Speaker 5: Hey, Daniel and Kelly, I'm always frustrated in movies when
23:31
Speaker 5: creatures grow too fast, like gremlins or the aliens in
23:35
Speaker 5: the Alien movie franchise. They're the size of a puppy
23:38
Speaker 5: and then hours later they're the size of a full
23:41
Speaker 5: grown person. Seems biologically impossible. I've got no problem suspending disbelief,
23:47
Speaker 5: but this does make me wonder what organisms grow the fastest.
23:51
Speaker 5: What are the biological, chemical, or whatever limits that define
23:54
Speaker 5: and limit the speed of growth. Seems like from an
23:57
Speaker 5: evolutionary perspective, growing super fast would be advantageous. Do a fox,
24:02
Speaker 5: great white shark, and human being all basically grow at
24:05
Speaker 5: the same speed. And if you were designing an alien
24:07
Speaker 5: creature to grow as fast as possible, what tweaks at
24:10
Speaker 5: the cellular level would you make to promote the fastest
24:13
Speaker 5: possible growth and what would the trade offs be? Also,
24:18
Speaker 5: do plants share similar growth limits to animals? I know
24:21
Speaker 5: kudzu can grow pretty fast.
24:24
Speaker 2: Thanks a lot, Thank you Aaron for including aliens.
24:29
Speaker 1: All right, where do you want to start with that one? John?
24:32
Speaker 3: So with the aliens, I think the quick answer there
24:35
Speaker 3: is that they've still got to abide by some of
24:38
Speaker 3: the fundamental principles of whatever physiology they have, but their
24:42
Speaker 3: physiology could vary, perhaps dramatically from what we have. I mean,
24:48
Speaker 3: there were only left to speculate. But there's also the
24:52
Speaker 3: fundamental principles of size and growth probably generally hold even
24:58
Speaker 3: in alien organism. That growth rate tends to be slower
25:04
Speaker 3: in bigger things overall. And yeah, like when I watch
25:09
Speaker 3: the movie Alien Romulus, I hope this isn't a spoiler,
25:12
Speaker 3: but there's at least one xenomorph, one alien there that
25:16
Speaker 3: seems to grow in the space of the two hours
25:19
Speaker 3: of the movie from a little thing like a little
25:23
Speaker 3: fetus sized thing to something bigger than a human. So yeah,
25:28
Speaker 3: I mean that caused a bit of credibility issues for me,
25:31
Speaker 3: but hey, it's movie logic and it's alien biology, so
25:35
Speaker 3: I mean can give it a benefit of the doubt there.
25:38
Speaker 2: So you say the fundamental rule is that bigger things
25:41
Speaker 2: grow more slowly. That must be a relative thing, Like
25:44
Speaker 2: an elephant adds a smaller percentage of its body weight
25:47
Speaker 2: every day or week as it's growing than a smaller
25:51
Speaker 2: creature does. Why is that? What's the rule that underlies that?
25:55
Speaker 3: Yeah, so that's due to the underlying physiology. Metabolic race
26:00
Speaker 3: is the key thing there. That smaller animals have higher
26:04
Speaker 3: metabolic rates, so yeah, and that's even true of people,
26:10
Speaker 3: Like when we're young, we have pretty high metabolic rates,
26:13
Speaker 3: and metaball rates slows down as we get older, and
26:16
Speaker 3: that relates to our growth rate. So there's a correlation
26:19
Speaker 3: between how quickly you burn energy and how quickly you grow.
26:23
Speaker 2: Is that what metabolic rate means? You're converting inputs into energy.
26:28
Speaker 3: How you use your internal energy to generate something else,
26:36
Speaker 3: to transform your internal energy like ATP molecules into something
26:42
Speaker 3: being done to your benefit like growth.
26:46
Speaker 2: And why do bigger animals have a slower metabolic rate
26:49
Speaker 2: or is that not known?
26:51
Speaker 1: It's a bummer either way.
26:54
Speaker 3: Bigger animals grow more or have slower metabolic rates because
26:59
Speaker 3: again the square cube law that because a growth rate
27:04
Speaker 3: depends on area to volume scaling, bigger animals have less
27:10
Speaker 3: area relative to their volume, so they can't use energy
27:14
Speaker 3: as quickly as a smaller animal can. And yeah, smaller animals,
27:17
Speaker 3: because they have more area relative to their volume, are
27:21
Speaker 3: shedding heat more quickly or gaining heat more quickly from
27:25
Speaker 3: their environment.
27:26
Speaker 2: So that seems like an argument that would work for
27:29
Speaker 2: like warm blooded animals that spend energy to stay warm.
27:32
Speaker 2: What about like a snake or a lizard or something.
27:35
Speaker 2: I know that they're using energy to the environment, but
27:38
Speaker 2: they're not burning energy to stay warm.
27:39
Speaker 3: Right, All organisms burn energy to stay warm if they're alive.
27:43
Speaker 3: If they're dead, then then maybe not. But yeah, because
27:50
Speaker 3: metabolism is fundamentally a wasteful process. It's not one hundred
27:54
Speaker 3: percent efficient. You don't convert your metabolic energy into whatever
27:59
Speaker 3: you want to do with it at one hundred percent efficiency.
28:01
Speaker 3: There's always heat shed. We have to remember heat and
28:05
Speaker 3: heat and biology is just waste, a waste product of
28:08
Speaker 3: what's going on. So there's actually a lot of waste,
28:11
Speaker 3: a lot of heat. Like muscle tends to be only
28:14
Speaker 3: thirty percent efficient. The rest goes away as heat. And
28:19
Speaker 3: so even small animals, if they're just sitting there, they're
28:22
Speaker 3: burning energy quite a lot of energy just sitting there,
28:25
Speaker 3: and not just to stay alive, but to remain warm,
28:28
Speaker 3: keep their organs at the right temperature during their physiology.
28:32
Speaker 3: But yes, it's true that smaller animals tend to be ectothermic,
28:37
Speaker 3: that is, rely more on their external environment to keep
28:41
Speaker 3: them warm or be quote unquote cold blooded, whereas larger
28:45
Speaker 3: animals tend to be endothermic, produce their own body heat more,
28:49
Speaker 3: rely more on that maintain a more constant body temperature,
28:53
Speaker 3: whereas ectothermic animals tend to vary their body temperature more
28:58
Speaker 3: because of their environment. And those two things endo ectothermy
29:02
Speaker 3: are sort of a continuum.
29:05
Speaker 1: But it's complicated biology, It's complicated.
29:09
Speaker 3: Yeah, the ambient temperature does have a big effect on
29:12
Speaker 3: metabolic rate and on growth, especially in ectothermic or cold
29:18
Speaker 3: blooded organisms. They rely on the environmental temperature to regulate
29:23
Speaker 3: their metabolic rate and therefore it will influence their growth rate.
29:27
Speaker 2: Thanks for correcting my naive ninth grade biology knowledge makes
29:32
Speaker 2: perfect sense that even if cold blooded animals are not
29:36
Speaker 2: trying to regulate their temperature, of course their metabolism is
29:39
Speaker 2: subject to the laws of thermodynamics, which means there's waste
29:42
Speaker 2: and it produces heat. That makes a lot of sense.
29:44
Speaker 3: Please please correct my physics. Please correct my physics at
29:48
Speaker 3: any time.
29:50
Speaker 2: And so this connects back the original question because this
29:52
Speaker 2: was how we were understanding why bigger animals have a
29:56
Speaker 2: smaller growth rate per mass. It's because have a slower
30:00
Speaker 2: metabolism because they have more volume mean surface area.
30:06
Speaker 3: Is that the right connection, Yeah, but it also ties
30:09
Speaker 3: into some really interesting other things that are tied into
30:13
Speaker 3: metabolic rate. And metabolic rate also depends on having the
30:17
Speaker 3: right resources. You need to be able to get enough
30:19
Speaker 3: food and so forth. That's very important. But fundamentally, if
30:23
Speaker 3: we go down to the cellular level, like the person asked,
30:27
Speaker 3: the rate of cell division is a fundamental limit on
30:31
Speaker 3: growth rate. You have to be able to do mitosis
30:34
Speaker 3: split your cells quickly enough to grow, and that depends
30:40
Speaker 3: on the metabolic rate in part, but it also depends
30:44
Speaker 3: on stuff that's going on inside the cell and various
30:48
Speaker 3: molecular processes of the nucleus. And a fundamental thing, a
30:52
Speaker 3: really cool thing that limits growth rate is DNA repair.
30:57
Speaker 3: If you think about it, if you're growing your cells
30:59
Speaker 3: really really quickly, you'll potentially accumulate more and more errors
31:04
Speaker 3: as you're splitting your cells over and over again. And
31:08
Speaker 3: if that error accumulates over and over again without getting fixed,
31:12
Speaker 3: then you'll get potentially either malformation of the organism or
31:17
Speaker 3: in a worst case, cancer, because cancer really is an
31:21
Speaker 3: overactive growth rate. It's uncontrolled cell division basically, so growth rate,
31:27
Speaker 3: if it's too excessive, could even be cancerous or at
31:31
Speaker 3: least lead to malformation. And that depends on the various
31:35
Speaker 3: repair mechanisms in cells, DNA repair program, cell death, other
31:41
Speaker 3: things that are there to correct for error. Error in
31:45
Speaker 3: cells is a very big problem, both in the actual
31:48
Speaker 3: longevity of the cells, but also in an evolutionary context.
31:51
Speaker 3: There's surely huge selection on repair mechanisms for cells to
31:58
Speaker 3: make sure they don't go and just produce lots of
32:02
Speaker 3: errors and malformations or cancer or whatnot.
32:05
Speaker 1: So we might all be growing much faster if we
32:08
Speaker 1: could perfectly replicate and we didn't have to worry about
32:11
Speaker 1: getting cancer.
32:12
Speaker 3: That's right, if we can control that repair mechanism, that
32:15
Speaker 3: could do some wonderful things for a growth rate and
32:18
Speaker 3: other things like lifespan.
32:20
Speaker 1: It could be twice as big.
32:22
Speaker 2: Would you want that?
32:24
Speaker 1: I'm just kidding. I don't really want to be twice
32:26
Speaker 1: as big. I'm plenty big.
32:27
Speaker 2: But it sounds like when you're watching alien xenomorph romulus
32:31
Speaker 2: or whatever, your real biology constraint is like, hey, that
32:36
Speaker 2: alien should have a lot of cancer given how fast
32:38
Speaker 2: it grows.
32:39
Speaker 3: Oh, unless it has some super alien correction mechanism, so
32:46
Speaker 3: who knows. It could be using silicon as it's rather
32:49
Speaker 3: than carbon as it's fundamental molecules, so then it could treat.
32:53
Speaker 2: That would be a great twist if we could use
32:55
Speaker 2: alien xenomorphs as a way to find a cancer cure. Right, Like,
32:58
Speaker 2: we have to have some cool bike chemical technology in them.
33:01
Speaker 3: Write it up. There's your movie script.
33:03
Speaker 1: Right there, Netflix, call me, that's right.
33:08
Speaker 3: Other things that become important to growth rate are also
33:12
Speaker 3: parental care. That animals that are cared for more by
33:15
Speaker 3: their parents can potentially grow more quickly, especially if they're
33:19
Speaker 3: being provided by their parents with lots of high nutrient
33:23
Speaker 3: food stuffs, but also reproductive rate will influence growth rate
33:27
Speaker 3: that if you need to get to adulthood quickly so
33:30
Speaker 3: that you can reproduce yourself and your population quickly, then
33:34
Speaker 3: growth rate will need to be adequate. Although that there's
33:38
Speaker 3: a trade off with the next thing that we'll talk about,
33:40
Speaker 3: which is lifespan. So growth rate, metabolic rate, reproductive rate,
33:46
Speaker 3: locomotive speed, all these things are intertwined in interesting ways.
33:51
Speaker 1: It depends. Okay, so you can't replicate too quickly because
33:54
Speaker 1: you may get cancer if you start growing your bones?
33:58
Speaker 1: Are your muscles too fat? Is there ever a trade
34:01
Speaker 1: off with like the quality of what you're producing, Like
34:04
Speaker 1: if you make bone really quickly or muscle really quickly,
34:07
Speaker 1: is it more likely to tear or to break?
34:08
Speaker 3: Oh? Definitely. Yeah. So bone is a wonderful example that
34:12
Speaker 3: bone takes time to mature. You have to produce like
34:15
Speaker 3: our in our leg bones, we have to produce a
34:17
Speaker 3: cartilage model first with living cells, and then gradually those
34:22
Speaker 3: cells are replaced by mineral that gets laid down by
34:26
Speaker 3: other cells. And so it takes time to produce the
34:29
Speaker 3: mineral of our bone that forms the supportive network that
34:34
Speaker 3: cartilage gradually goes away. And when we go from a
34:37
Speaker 3: pretty squishy, flexible, but living structure made of cartilage to
34:42
Speaker 3: a structure that's mostly made of non living but very strong, stiff,
34:46
Speaker 3: supportive mineral. So yeah, you couldn't lay down a bone
34:51
Speaker 3: very very quickly as a mineral substance. You need that
34:55
Speaker 3: time to construct the cartilage.
34:58
Speaker 2: It's like cheese. You can like a really soft, fresh cheese,
35:01
Speaker 2: but you want like a nice hard parbisan like that
35:04
Speaker 2: takes years in a an Italian cave, doesn't it.
35:09
Speaker 3: Patience pays off. Another thing that's important is different rates
35:14
Speaker 3: of growth of organs. So organs will grow at different
35:19
Speaker 3: rates depending on what they are and what they need
35:22
Speaker 3: to be in the adult organism, and different molecules govern
35:26
Speaker 3: the rate of growth. So like liver growth is regulated
35:31
Speaker 3: by bile acid flux. So the bile that you know,
35:35
Speaker 3: the liver is very well known for using helps regulate
35:40
Speaker 3: how quickly the liver grows. And every different organ there
35:43
Speaker 3: are different things that regulate it, and the size of
35:46
Speaker 3: the organ at different points in the life cycle will
35:49
Speaker 3: be relatively different depending on how quickly it's growing.
35:54
Speaker 1: I'm always amazed that the liver grows back at all,
35:56
Speaker 1: and that they can do like surgeries where you get
35:58
Speaker 1: a little bit of somebody's liver. I'd always assume that
36:00
Speaker 1: the liver was like a thing that was made and
36:03
Speaker 1: then would not grow anymore. But bodies are amazing.
36:06
Speaker 3: They sure are. Yeah, And by tweaking those growth rates
36:10
Speaker 3: of organs, you can get really interesting changes of organisms.
36:14
Speaker 3: So you can get bigger hands or longer limbs or
36:18
Speaker 3: whatever by tweaking differential growth of body parts.
36:21
Speaker 1: Do we know if any of these rules that we've
36:23
Speaker 1: talked about apply to plants as well or is that
36:26
Speaker 1: just like a totally different game.
36:28
Speaker 3: Oh yeah, a lot of those rules would apply it
36:31
Speaker 3: to plants as well, definitely, like the DNA repair stuff,
36:34
Speaker 3: metabolic rate, all that stuff. I guess the one thing
36:37
Speaker 3: that wouldn't apply is how fast plants can run, because yeah,
36:42
Speaker 3: they do things.
36:42
Speaker 2: Differently, basically still zero. It also applies to dairy products,
36:48
Speaker 2: right If you take, for example, yogurt and you put
36:51
Speaker 2: it in milk, it makes more yogurt just the same
36:53
Speaker 2: way the liver grows. Here, I'm really leaning on my
36:56
Speaker 2: ninth grade biology.
36:57
Speaker 1: Are you hungry today?
36:58
Speaker 3: Also, tumbleweeds might argue with you in terms of the
37:03
Speaker 3: plant locomotion thing, but they're cheating Yeah, they're.
37:08
Speaker 1: Cheating, are tumble I thought tumbleweeds were just like dead
37:14
Speaker 1: plants that sort of accumulated and then blew across the
37:18
Speaker 1: desert or whatever. Are they alive still.
37:20
Speaker 3: I'm sure there's something alive in there, like their seeds.
37:23
Speaker 3: But I was joking. I mean, I just when you
37:27
Speaker 3: mentioned plants and movement, immediately an image of tumbleweeds jumped
37:33
Speaker 3: into my mind. And yeah, I mean there are plants
37:36
Speaker 3: that move, but just slowly.
37:39
Speaker 1: You could like literally tell me almost anything about plants,
37:42
Speaker 1: and as long as you had a straight face, I
37:44
Speaker 1: would believe it, because plants can do so many things
37:47
Speaker 1: that blow my mind. Like, you know, we had an
37:50
Speaker 1: episode a while back about a plant that like, if
37:52
Speaker 1: you know, if a branch touches the ground again, it
37:55
Speaker 1: will root, and then if you cut it, it will
37:57
Speaker 1: produce a new tree. And I'm like, no, no, no, no,
37:59
Speaker 1: that's not how animals work. They can't be how anything works.
38:01
Speaker 1: And anyway, I'm very animal centric. Plants. Plants seem to
38:05
Speaker 1: break all the rules that seem seem logical to me.
38:08
Speaker 3: Yeah. I try to remain humble as a train zoologist,
38:11
Speaker 3: reminding myself that fungi and plants and other non animals
38:15
Speaker 3: can do very cool stuff that we shouldn't let our
38:18
Speaker 3: animal bias leave us ignorant of.
38:20
Speaker 1: Yeah, I'm way less excited about hugging fungi and plants,
38:24
Speaker 1: but yeah, they still do some fascinating things. I've got
38:27
Speaker 1: one last question about sharks. So you mentioned that when
38:30
Speaker 1: we're building bone, that takes a long time, but sharks
38:34
Speaker 1: are mostly cartilage instead of bone, So can sharks grow
38:38
Speaker 1: much faster than the rest of us.
38:40
Speaker 3: I don't know that that's true that sharks can be
38:44
Speaker 3: grow faster. I do know of some studies looking into
38:50
Speaker 3: sharks not having as much cancer. Yeah, at least some sharks.
38:54
Speaker 3: And there's like recently in the news over the past
38:58
Speaker 3: decade or so, there's been a lot of interest in
39:01
Speaker 3: these greenland sharks that can get pretty big. These are
39:06
Speaker 3: sharks that range into kind of arctic waters. They can
39:09
Speaker 3: get quite big. But also it's been realized they can
39:13
Speaker 3: perhaps live as long as five hundred years or something
39:16
Speaker 3: like that. Wow, And presumably they're growing very slowly during
39:21
Speaker 3: that time. But also it seems like they and I
39:27
Speaker 3: think if I remember correctly, and other sharks just don't
39:30
Speaker 3: get a lot of cancer.
39:31
Speaker 1: I feel like that would be hard to confirm because
39:35
Speaker 1: we just I mean, we don't watch sharks for that long.
39:38
Speaker 1: But I guess we've dissected and eaten a lot of sharks,
39:40
Speaker 1: so we probably would have seen plenty of cancer if
39:43
Speaker 1: they got a lot of cancer. Yeah, I thought you
39:45
Speaker 1: were going to tell me that I was wrong about
39:47
Speaker 1: sharks being made mostly of cartilage, and I was going
39:50
Speaker 1: to be super nearest, but then you said that, no,
39:52
Speaker 1: they don't grow that fast. So anyway, big relief for
39:55
Speaker 1: me here.
39:55
Speaker 3: But also, sharks have calcified cartilage that forms a lot
39:59
Speaker 3: of their stiff supportive network, so they do lay down mineral,
40:04
Speaker 3: but still it's a lot more living material than in
40:08
Speaker 3: a typical bony fish.
40:09
Speaker 2: Okay, five hundred yeers is a lot older than the
40:13
Speaker 2: oldest parmesan I'm aware of, So in the shark versus
40:16
Speaker 2: parmesan competition, it sounds like sharks are winning. For those
40:19
Speaker 2: keeping score at home, we.
40:21
Speaker 3: Need to crack open some ceramics and Pompeii and see
40:24
Speaker 3: if there's like any any cheese still in there.
40:29
Speaker 2: And on the cheese topic, I will say that cheese
40:32
Speaker 2: are very fast. You ever seen the cheese roll in
40:34
Speaker 2: Scotland where they roll a cheese down the hill and
40:36
Speaker 2: people roll down trying to chase it. Nobody ever catches
40:39
Speaker 2: that cheese.
40:40
Speaker 3: Yeah, you win again, gravity.
40:44
Speaker 2: Unfortunately, I just want to make sure we're asking John
40:49
Speaker 2: questions he hasn't prepared for.
40:50
Speaker 3: That's great, great, I've never witnessed the rolling cheese. I
40:55
Speaker 3: think I've seen cartoons of it. Maybe it was in
40:56
Speaker 3: the Simpsons or something like that. I don't know.
40:58
Speaker 1: Yeah, a cultural touch point for sure. Yes, all right, Aaron,
41:04
Speaker 1: what did you have to say?
41:05
Speaker 5: Hey, Daniel and Kelly, thanks for answering my question about growth.
41:08
Speaker 5: I tried not to take it personally when your guests
41:11
Speaker 5: claim that quote metabolism is a fundamentally wasteful process. As
41:16
Speaker 5: my kids say, stop body shaming. Also, a little digging
41:20
Speaker 5: on my own uncovered a somewhat unbelievable fact that a
41:23
Speaker 5: blue whale calf can add up to two hundred pounds
41:27
Speaker 5: of body weight, which is about the equivalent of one's
41:30
Speaker 5: enomorph per day. Let's just hope that DNA repair process
41:35
Speaker 5: is keeping up.
41:36
Speaker 3: Thanks again, Erin.
41:57
Speaker 1: All right, this last question has a little bit of
42:00
Speaker 1: than for everyone, a little bit of biology, a little
42:02
Speaker 1: bit of physics, So Daniel will step in here too.
42:04
Speaker 1: So Rosalin wanted to know.
42:07
Speaker 6: I was thinking about the relationship between space and time,
42:12
Speaker 6: and I was wondering if there's a correlation between all
42:17
Speaker 6: of that and the experience and time scale of creatures. So, like,
42:25
Speaker 6: do smaller animals have shorter lives because they experience time
42:28
Speaker 6: at a faster pace than those of us who are bigger, taller,
42:31
Speaker 6: and we're little away from the impact of space time
42:34
Speaker 6: curvature or are they just similar but not at all
42:39
Speaker 6: related to each other.
42:41
Speaker 1: Thanks, So we're going to have part of this question
42:44
Speaker 1: go to Daniel, and then part of this question. I
42:46
Speaker 1: would love to know more about how size impacts lifespan.
42:50
Speaker 1: So first of all, Daniel, is spacetime curvature impacting the
42:55
Speaker 1: lifespan of organisms?
42:57
Speaker 2: Absolutely it is, but probably not in a way that
43:01
Speaker 2: we can really measure. You know, space time curvature is
43:05
Speaker 2: how space responds to mass, and when there's a lot
43:09
Speaker 2: of mass or energy density around, clocks tick more slowly.
43:12
Speaker 2: So clocks in the surface of the Earth tick slower
43:15
Speaker 2: than clocks out in space. Clocks near a black hole
43:18
Speaker 2: tick very very slowly. So the fact that we're all
43:21
Speaker 2: here on Earth means that are biological clocks tick more slowly,
43:26
Speaker 2: and that's also true for the whole universe. Parts of
43:29
Speaker 2: the universe that are far from black holes would have
43:32
Speaker 2: clocks that tick more times since the Big Bang than
43:36
Speaker 2: clocks that are near black holes. And so in that sense,
43:39
Speaker 2: even the universe you can't say has a single age.
43:42
Speaker 2: It depends on where you are in space. So if
43:45
Speaker 2: you have a creature and it has a lot of mass,
43:48
Speaker 2: it's a blue whale, there's going to be a little
43:49
Speaker 2: bit more energy density there, which means it's clocks will
43:52
Speaker 2: tick more slowly. Is that measurable Almost certainly not, because
43:57
Speaker 2: the amount of mass necessary to make clocks tick more
44:01
Speaker 2: slowly is really large. Even clocks on the surface of
44:04
Speaker 2: the Earth, because of the Earth's enorm is mass, tick
44:08
Speaker 2: just barely more slowly than clocks in orbit. So even
44:12
Speaker 2: a blue whale is not going to measurably affect clocks.
44:15
Speaker 2: But technically it does happen.
44:17
Speaker 1: So you're saying it experiences more time because its clock
44:21
Speaker 1: is ticking more slowly, and therefore it lives longer. Is
44:24
Speaker 1: that these when you kept saying clocks tick more slowly,
44:28
Speaker 1: I keep thinking, do you mean like their heart beats
44:30
Speaker 1: more slowly. But no, you mean like the amount of
44:32
Speaker 1: time it's experiencing.
44:33
Speaker 2: I mean it's clock beats more slowly from somebody from
44:36
Speaker 2: the outside. So we see it living in slow motion,
44:40
Speaker 2: so it's younger, right than we would be, and it
44:43
Speaker 2: sees our clocks moving at high speed, so it sees
44:46
Speaker 2: the rest of the universe as like operating on fast forward,
44:51
Speaker 2: So it lives longer according to our clocks because it's
44:54
Speaker 2: living in slow motion. Does that make sense?
44:57
Speaker 1: Yes, but at such a negligible differ, friends, Yeah, because
45:02
Speaker 1: blue whales are huge, but small relative to the size
45:05
Speaker 1: of the universe or something, right, that's.
45:06
Speaker 2: Right, But if you have aliens who have masses of
45:09
Speaker 2: a star or something, then this could be a real factor.
45:13
Speaker 3: That's what I was going to go to, because everything
45:15
Speaker 3: matters in a xenomorph universe, a frame or reference. We
45:19
Speaker 3: always have to take our biology to that. So, yeah,
45:22
Speaker 3: a star sized organism would perceive our time as very
45:27
Speaker 3: different from the time it was living in and we
45:30
Speaker 3: need more science fiction about that.
45:33
Speaker 2: We definitely do.
45:34
Speaker 1: Yeah. So are you saying then that an alien that
45:38
Speaker 1: was so big it was the size of the sun
45:40
Speaker 1: would experience time more slowly and thus live longer than
45:44
Speaker 1: the rest of us.
45:46
Speaker 2: Yes, it would see us die off more quickly because
45:49
Speaker 2: our clocks tick faster than its clocks.
45:52
Speaker 3: Wow. Yeah, yeah. So there was that Star Trek movie
45:55
Speaker 3: where they where they met like some sort of huge
45:59
Speaker 3: thing that was or I thought it was God. Remember
46:02
Speaker 3: which movie that was, Like it was a Final Frontier
46:05
Speaker 3: or something. Oh, anyway, they blew up God, so it
46:08
Speaker 3: was all fine in the end.
46:12
Speaker 1: I thought Star Trek was supposed to be like the
46:14
Speaker 1: nice version of the sci fi worlds where they were
46:17
Speaker 1: like nice to other creatures.
46:19
Speaker 3: I think it was a naughty god, or thought it
46:20
Speaker 3: was a god and it was naughty, so it had
46:23
Speaker 3: to get proton torpedoed or whatever they did to it.
46:26
Speaker 1: Got it, got what was coming to him. Yeah, all right,
46:28
Speaker 1: Well I really like the biology answers because the physics
46:31
Speaker 1: answers kind of break my brain. But they're amazing. But
46:34
Speaker 1: let's get a different perspective. So, how does size impact
46:38
Speaker 1: lifespan when the framing is biology, John.
46:42
Speaker 3: I think there it's simpler, which is nice because biology
46:46
Speaker 3: is often so messy. Oh maybe it's not simpler, but
46:49
Speaker 3: it's simple. There's a direct relationship between size and lifespan
46:54
Speaker 3: in organisms. Generally speaking, bigger things live longer, and growth
46:59
Speaker 3: rate is involved there, metabolic rate is involved there, all
47:03
Speaker 3: this stuff that we talked about earlier. So bigger things
47:07
Speaker 3: take longer to become big, but still they can get
47:10
Speaker 3: bigger as long as they have enough resources to do so.
47:14
Speaker 3: And that's basically it. That we don't see a lot
47:17
Speaker 3: of small things at all that live very long. If
47:20
Speaker 3: you think about a mouse, it's lucky to live maybe
47:24
Speaker 3: a year. I don't know if kids have ant farms anymore.
47:27
Speaker 1: Do they I don't see them flying off the shelves
47:30
Speaker 1: at science museums, but I still see them sold at
47:34
Speaker 1: science museums.
47:35
Speaker 3: I really, I really have deep hope that kids still
47:38
Speaker 3: like ant farms, and maybe like them more than YouTube
47:43
Speaker 3: or TikTok. But anyway, I mean, if you have an
47:46
Speaker 3: ant farm, you'll notice that ants die pretty quickly, and
47:50
Speaker 3: other small things die quickly, and if we go down
47:52
Speaker 3: to the bacteria level or they're dropping dead like crazy.
47:56
Speaker 3: So there's a very strong relationship between si in lifespan
48:01
Speaker 3: across biology.
48:02
Speaker 2: And I remember hearing this sort of simplistic explanation that
48:06
Speaker 2: it was again about metabolism, that larger animals have a
48:09
Speaker 2: slower metabolism and a slower heart rate, and that mice
48:13
Speaker 2: and elephants live the same number of heart beats, but
48:16
Speaker 2: that mice just have their hearts beating faster and so
48:20
Speaker 2: fewer ticks on the clock. Is that true or is
48:23
Speaker 2: my biology're wrong?
48:24
Speaker 3: I think the heart rate thing is very very very
48:27
Speaker 3: coarsely true, and that would only apply to organisms that
48:31
Speaker 3: have hearts, But I mean that applies to a lot
48:33
Speaker 3: of animals. But yeah, I mean growth rate, metabolic rate,
48:38
Speaker 3: all that stuff is tied into lifespan pretty tightly. But
48:42
Speaker 3: a neat thing that ties into this kind of concept
48:46
Speaker 3: of biological time is that small organisms are vulnerable, so
48:52
Speaker 3: they tend to have high metabolic rates so they can
48:55
Speaker 3: get to a size where they're able to do all
48:58
Speaker 3: their adult stuff quickly enough. And that's that relationship of
49:02
Speaker 3: size and vulnerability and metabolic rate has evolved. There's selection
49:07
Speaker 3: for small things to have high metabolic rates and grow quickly,
49:11
Speaker 3: and also there's selection for lifespan to be short, because
49:16
Speaker 3: if lifespan is shorter, then organisms can reproduce themselves more quickly.
49:21
Speaker 3: The greater your size is, it's probably likely that your
49:24
Speaker 3: reproductive rate is going to be slower, otherwise the Earth
49:28
Speaker 3: would be covered in whales. So there is again this
49:37
Speaker 3: correlation between growth rate, reproductive rate, metabolic rate, and then
49:42
Speaker 3: size and lifespan. These things are all tied together and
49:44
Speaker 3: then over deep time, over evolution, there are trade offs
49:48
Speaker 3: that things that are big go extinct more often and
49:53
Speaker 3: speciate create new species less often. So as long as
49:58
Speaker 3: the environment is pretty stable, big things do okay. There
50:02
Speaker 3: tends to be an increase in the number of big
50:05
Speaker 3: bodied adult species over time, But as soon as the
50:09
Speaker 3: environment changes, kaboom, they go extinct. And that's why we
50:13
Speaker 3: see these mass extinction pulses is because of especially rapid
50:18
Speaker 3: environmental change is something that big organisms cannot adapt to.
50:23
Speaker 3: They go extinct more quickly, they speciate more slowly, and
50:27
Speaker 3: therefore there are less big things in a rapidly changing environment,
50:33
Speaker 3: and mass extinctions tend to hit the bigger things harder.
50:37
Speaker 2: What a cool experiment we could do to test that,
50:39
Speaker 2: which is like land on a bunch of exoplanets and
50:42
Speaker 2: understand the relative stability of those ecosystems and see if
50:46
Speaker 2: the ones with more stable ecosystems really do have more
50:50
Speaker 2: big land animals. That would be crazy.
50:52
Speaker 3: Unfortunately, to bring us back to reality, we're doing that
50:55
Speaker 3: experiment right now with climate change in a way that's
50:58
Speaker 3: never happened before. Even the asteroid that hit Earth, it
51:03
Speaker 3: did its share of devastation sixty six million years ago,
51:06
Speaker 3: wiping out the Mesozoic dinosaurs and many other things. There
51:10
Speaker 3: was clear size selection going on, but some of the
51:14
Speaker 3: extinction patterns happened over thousands of years, whereas right now
51:18
Speaker 3: the stuff we're doing over the scale of decades is
51:21
Speaker 3: pretty unprecedented in terms of extinction, and we're having a
51:25
Speaker 3: huge bias toward getting rid of big things because of
51:29
Speaker 3: loss of habitat and hunting and so on and so forth.
51:33
Speaker 3: That always hits the big things quicker. And that's followed
51:37
Speaker 3: on from an ice age just you know, ten thousand
51:40
Speaker 3: years ago that again wiped out a lot of the megafauna.
51:44
Speaker 3: So yeah, that's our experiment.
51:47
Speaker 2: It's hard for ecosystems to respond. And the timescale of
51:49
Speaker 2: like a parmesan rather than like geological timescales.
51:53
Speaker 3: Yes, yes, again, bringing back to the cheese frame of reference.
51:59
Speaker 3: Excit right, we got the xenomore frame of reference and
52:01
Speaker 3: the Cheese frame of reference and that's all you need
52:04
Speaker 3: for our podcast.
52:05
Speaker 1: That's great. We got the two important frames of reference.
52:08
Speaker 2: And I have the mental image of an ocean stocked
52:11
Speaker 2: filled with whales, overflowing with whales, all of them eating
52:15
Speaker 2: a wheel of parmesan.
52:16
Speaker 3: Okay, I thought you'd bring the cheese in there. That's great.
52:20
Speaker 2: I'm nothing if not predictable.
52:25
Speaker 1: Before we go to Rosalind, do you want to tell
52:28
Speaker 1: us what you've been up to and give us a
52:30
Speaker 1: quick update on the cool stuff you've been doing since
52:32
Speaker 1: we last chatted.
52:34
Speaker 3: What have I been doing. I've been studying crocodiles a lot,
52:38
Speaker 3: both living ones and extinct ones. How they move, how
52:42
Speaker 3: their movement has evolved. That's a big focus of mine
52:45
Speaker 3: lately with various postdoctoral researchers and PhD students and master
52:51
Speaker 3: students and undergrads. So that's been a lot of fun
52:53
Speaker 3: trying to unravel the history of crocodiles and how they
52:57
Speaker 3: move in more detail, because they start off as wonderful, small,
53:02
Speaker 3: kind of cat sized, quick animals and then evolved into
53:06
Speaker 3: the diversity of different forms that ultimately got wiped out
53:10
Speaker 3: by that mass extinction at the end of the Cretaceous
53:13
Speaker 3: leaving just the crocodiles and alligators that we're familiar with.
53:17
Speaker 3: So there was a great diversity of crocodiles back in
53:19
Speaker 3: the Mesozoic that we can't really appreciate from a modern
53:24
Speaker 3: perspective of the twenty five twenty eight species of all
53:28
Speaker 3: fairly similar crocodilians, whereas about two hundred and thirty million
53:32
Speaker 3: years ago there were these really amazing more mammal like crocodiles,
53:36
Speaker 3: and then later things like whale like crocodiles, and yeah,
53:40
Speaker 3: crazy kinds of ecologies and body plans and locomotive styles
53:45
Speaker 3: of crocodiles over there over their heyday. So that's I'm
53:49
Speaker 3: doing a lot about that. That's keeping me very busy.
53:54
Speaker 1: Cool. You know, crocodiles also have very fascinating parasites which
53:57
Speaker 1: you can, you know, keep your eyes open for. Haley
54:01
Speaker 1: Dutton recently described a new parasite from the eye of
54:05
Speaker 1: a crocodile, and she named it. She got to name
54:08
Speaker 1: the whole genus and she named it later gator, which
54:10
Speaker 1: I thought was fun and rolls off the tongue. So anyway,
54:14
Speaker 1: keep your eyes open for fun parasites, including parasites on
54:17
Speaker 1: their eyes.
54:18
Speaker 3: That's why they have crocodile tears. It's all the parasites.
54:23
Speaker 1: Yeah, perhaps, do you make sure that their like mouths
54:26
Speaker 1: are held shut in some way before you are measuring them?
54:31
Speaker 5: Or oh?
54:31
Speaker 3: Yeah. So when I work with live crocodiles, which I've
54:35
Speaker 3: done a fair amount for health and safety reasons, you
54:38
Speaker 3: do have to worry about the bitey end and the tail.
54:42
Speaker 3: The tail end too, because the tail's also a weapon,
54:45
Speaker 3: but the bidy end's worse and Luckily, wild crocodile jaw
54:51
Speaker 3: closing muscles are very strong. If you ever look at
54:53
Speaker 3: the back of the head of a crocodile, it looks
54:56
Speaker 3: like they have fatty jowls, especially if the crocodile is
54:59
Speaker 3: lying down. That's not fat, that's not jowls. That's jaw
55:02
Speaker 3: closing muscle. Wow, it's real meaty muscle. And so they
55:07
Speaker 3: have the greatest bite for us of organisms in absolute terms.
55:11
Speaker 3: They can bite extremely hard, but their jaw opening muscles
55:15
Speaker 3: are weak. So if you close a crocodile's mouth, it's
55:19
Speaker 3: not so good at opening the mouth again, So what
55:23
Speaker 3: we do is close the crocodile's mouth by restraining it
55:26
Speaker 3: and then put electrical tape around the mouth. And that's
55:30
Speaker 3: enough to secure the snout shut so it can't bite anyone.
55:34
Speaker 3: They still have teeth that stick out, so the jaws
55:38
Speaker 3: still have sharp bets on the end that you have
55:40
Speaker 3: to watch for. But still that's a lot, a lot
55:42
Speaker 3: better than getting bitten by one, because even a small
55:44
Speaker 3: crocodile can really hurt you.
55:47
Speaker 1: All Right, Well, that's intense, and hopefully you'll come back
55:50
Speaker 1: on the show in the future and tell us more
55:51
Speaker 1: about what you've learned about crocodiles.
55:53
Speaker 3: I'd love to Awesome.
55:55
Speaker 1: We're gonna send this answer to Rosalind and see what
55:57
Speaker 1: she had to say.
55:59
Speaker 6: Daniel Kelly, thanks for answering my question. It makes a
56:01
Speaker 6: lot of sense. It has more to do with biology
56:03
Speaker 6: than space and time. I was up very late that
56:06
Speaker 6: night reading a lot of ancient philosophers and they had
56:09
Speaker 6: some really big ideas about the universe and nature, and
56:12
Speaker 6: it just kind of got me into thinking. Thanks for
56:15
Speaker 6: bringing it back a little bit closer to home. Biology
56:17
Speaker 6: makes sense. I appreciate you.
56:25
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