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I don't understand how that would limit evolution. Bigger bodies can evolve together with bigger hearts, as already witnessed with the very whales being researc

I don't understand how that would limit evolution. Bigger bodies can evolve together with bigger hearts, as already witnessed with the very whales being researched.

JumpCrisscross 7mo ago
> don't understand how that would limit evolution Cardiac tissue is a surface. Blood is a volume. I think they’re saying blue whale hearts are near the largest current biology can evolve. Which is interesting because it suggests if we could e.g. engineer whales with carbon-fiber hearts or whatever, they’d evolve to grow even bigger.
- observationist 7mo ago
  Blackheart the whale, lurking the oceans, ever devouring and growing. I think you've got a good Lovecraft/Pirates of the Carribean/Black Mirror mashup premise here.
- fluoridation 7mo ago
  Cardiac tissue is also a volume. It can be thicker or thinner as the animal requires.
  - adrian_b 7mo ago
    Yes, but the force of a muscle does not increase with volume, but only with its section. So a bigger heart would need to have thicker walls in comparison with its internal volume, which would increase disproportionately the volume of the heart walls, so for bigger and bigger hearts the useful internal volume that is filled with blood would be a smaller and smaller fraction of the total heart volume. The lower efficiency of a bigger heart would require a higher contraction frequency to compensate, but the bigger a heart is the smaller is its maximum contraction frequency, due to the small speed of the propagation of an excitation through muscle cells and nervous cells.
    - fluoridation 7mo ago
      >The lower efficiency of a bigger heart would require a higher contraction frequency to compensate If that's the case, then how come rats have a higher heart rate than humans, who have a higher heart rate than whales? Do whales have hearts with thinner walls than humans, while rats have big lumps of muscle with teeny tiny chambers?
    - JumpCrisscross 7mo ago
      > the force of a muscle does not increase with volume It does. But it must still impart that force through a surface to a volume. And at a certain point, you hit the mechanical limits of that surface’s ability to hold itself together.
- boxed 7mo ago
  Or just a lot of smaller hearts.
observationist 7mo ago
The volume of blood that needs to be pumped increases e̶x̶p̶o̶n̶e̶n̶t̶i̶a̶l̶l̶y̶ cubically with size, meaning the cells have to do more work, or there have to be more of them. The size of the heart has to match the volume of blood being pumped - if they evolved to be larger, the heart might have to be so big that it creates pathology in other areas, or has to pump so hard it damages tissue, or creates forces so great that veins or arteries collapse or burst. It's probably not as dramatic an issue as that. It could also be sensory - past a certain size, in order to be sensitive enough to detect damage and deal with normal conditions, it would have to be irritated all the time, or numb to potential hazards. There are all sorts of second and third order consequences limiting how various vital systems can interplay, so more than likely, it's a combination of a whole bunch of things that subtly limit the overall size to where it's at, and any further increase degrades its abilities to survive. They're just so huge. Their brains are 4 times larger than a human's brain, but we share a whole lot of structure, from the cellular level to the macro, with two lobes, some shared sulcal features (same folding pattern) which indicates that we likely share enough connectomic structure for the ways in which our brains operate to produce similar conscious experiences. Someday, in the distant future, we should be able to use BCI to feel exactly what it's like to be a blue whale (and vice versa.) Their brains have similar cortical structure, but even though the brains are about 7 times larger, their cortical surface area is only 2-3 times that of a human. It really puts into context how bizarrely massive our brains are for our relatively tiny size. For contrast, titanosaur hearts would have been around 500 lbs and up to 6 feet in diameter, and their brains were about the size of a big walnut. These land animals were up to 40m long and 100 tons. Anyway - physics of tissue and frailties of being made of meat are what keep the whales from getting much bigger.
- frotaur 7mo ago
  Nitpick, but the volume increases cubically (it scales with volume), not exponentially.
  - observationist 7mo ago
    Thank you, I'll correct that. I was thinking inverse square law, then instead of asking an AI like a good nerd, I just winged it.
kadoban 7mo ago
> Bigger bodies can evolve together with bigger hearts, as already witnessed with the very whales being researched. Hm? Aren't blue whales the biggest animals to ever have lived that we know of?
- adrian_b 7mo ago
  Yes. There are many extinct animals that had sizes comparable with sperm whales, including some dinosaurs, but none of them had sizes comparable with blue whales. The reason for this is simple, few animals have developed a method of feeding like that of the baleen whales, by filtrating huge amounts of sea water, which can provide enough food for such a huge body. Other animals that have developed similar feeding methods, like 4 groups of species of sharks or rays, including the whale shark, have also become much bigger than their relatives.
robotnikman 7mo ago
Or if not bigger hearts, what about multiple hearts?
meroes 7mo ago
Just evolve better blood! /s
Sharlin 7mo ago
As usual when it comes to scaling of mechanical things including organisms, it’s a matter of the square–cube law. https://en.wikipedia.org/wiki/Square%E2%80%93cube_law https://en.wikipedia.org/wiki/Square%E2%80%93cube_law

I don't understand how that would limit evolution. Bigger bodies can evolve together with bigger hearts, as already witnessed with the very whales being researched.

JumpCrisscross 7mo ago

> don't understand how that would limit evolution Cardiac tissue is a surface. Blood is a volume. I think they’re saying blue whale hearts are near the largest current biology can evolve. Which is interesting because it suggests if we could e.g. engineer whales with carbon-fiber hearts or whatever, they’d evolve to grow even bigger.

observationist 7mo ago
Blackheart the whale, lurking the oceans, ever devouring and growing. I think you've got a good Lovecraft/Pirates of the Carribean/Black Mirror mashup premise here.
fluoridation 7mo ago
Cardiac tissue is also a volume. It can be thicker or thinner as the animal requires.
- adrian_b 7mo ago
  Yes, but the force of a muscle does not increase with volume, but only with its section. So a bigger heart would need to have thicker walls in comparison with its internal volume, which would increase disproportionately the volume of the heart walls, so for bigger and bigger hearts the useful internal volume that is filled with blood would be a smaller and smaller fraction of the total heart volume. The lower efficiency of a bigger heart would require a higher contraction frequency to compensate, but the bigger a heart is the smaller is its maximum contraction frequency, due to the small speed of the propagation of an excitation through muscle cells and nervous cells.
  - fluoridation 7mo ago
    >The lower efficiency of a bigger heart would require a higher contraction frequency to compensate If that's the case, then how come rats have a higher heart rate than humans, who have a higher heart rate than whales? Do whales have hearts with thinner walls than humans, while rats have big lumps of muscle with teeny tiny chambers?
  - JumpCrisscross 7mo ago
    > the force of a muscle does not increase with volume It does. But it must still impart that force through a surface to a volume. And at a certain point, you hit the mechanical limits of that surface’s ability to hold itself together.
boxed 7mo ago
Or just a lot of smaller hearts.

observationist 7mo ago

The volume of blood that needs to be pumped increases e̶x̶p̶o̶n̶e̶n̶t̶i̶a̶l̶l̶y̶ cubically with size, meaning the cells have to do more work, or there have to be more of them. The size of the heart has to match the volume of blood being pumped - if they evolved to be larger, the heart might have to be so big that it creates pathology in other areas, or has to pump so hard it damages tissue, or creates forces so great that veins or arteries collapse or burst. It's probably not as dramatic an issue as that. It could also be sensory - past a certain size, in order to be sensitive enough to detect damage and deal with normal conditions, it would have to be irritated all the time, or numb to potential hazards. There are all sorts of second and third order consequences limiting how various vital systems can interplay, so more than likely, it's a combination of a whole bunch of things that subtly limit the overall size to where it's at, and any further increase degrades its abilities to survive. They're just so huge. Their brains are 4 times larger than a human's brain, but we share a whole lot of structure, from the cellular level to the macro, with two lobes, some shared sulcal features (same folding pattern) which indicates that we likely share enough connectomic structure for the ways in which our brains operate to produce similar conscious experiences. Someday, in the distant future, we should be able to use BCI to feel exactly what it's like to be a blue whale (and vice versa.) Their brains have similar cortical structure, but even though the brains are about 7 times larger, their cortical surface area is only 2-3 times that of a human. It really puts into context how bizarrely massive our brains are for our relatively tiny size. For contrast, titanosaur hearts would have been around 500 lbs and up to 6 feet in diameter, and their brains were about the size of a big walnut. These land animals were up to 40m long and 100 tons. Anyway - physics of tissue and frailties of being made of meat are what keep the whales from getting much bigger.

frotaur 7mo ago
Nitpick, but the volume increases cubically (it scales with volume), not exponentially.
- observationist 7mo ago
  Thank you, I'll correct that. I was thinking inverse square law, then instead of asking an AI like a good nerd, I just winged it.

kadoban 7mo ago

> Bigger bodies can evolve together with bigger hearts, as already witnessed with the very whales being researched. Hm? Aren't blue whales the biggest animals to ever have lived that we know of?

adrian_b 7mo ago
Yes. There are many extinct animals that had sizes comparable with sperm whales, including some dinosaurs, but none of them had sizes comparable with blue whales. The reason for this is simple, few animals have developed a method of feeding like that of the baleen whales, by filtrating huge amounts of sea water, which can provide enough food for such a huge body. Other animals that have developed similar feeding methods, like 4 groups of species of sharks or rays, including the whale shark, have also become much bigger than their relatives.

robotnikman 7mo ago

Or if not bigger hearts, what about multiple hearts?

meroes 7mo ago

Just evolve better blood! /s

Sharlin 7mo ago

As usual when it comes to scaling of mechanical things including organisms, it’s a matter of the square–cube law. https://en.wikipedia.org/wiki/Square%E2%80%93cube_law https://en.wikipedia.org/wiki/Square%E2%80%93cube_law