4 ms·

Going a step further, the question of how metamorphosis evolved is even more puzzling.

simmerup 3y ago
300 million years and a lot of failed branches
XorNot 3y ago
It's an extreme version of reproductive optimization: a lot of animals have a reproductive strategy of "bank resources, then mate and die". Even things with complex neural systems like octopuses (who despite their intelligence, have no parents because they die after protecting their eggs). So how you get here sort of makes sense in that context: if reproduction is more successful if you delay it to collect resources, then it also follows that discarding any biomass you don't need once you've got enough to ensure the reproduction happens quickly and successfully afterwards would lead to this sort of strategy in extremis. A "prototype" caterpillar doesn't need to be able to fly - it just needs to do something which makes it more mobile and slightly more successful (and well, getting away from where you're born and spreading out is a good way to ensure the gene line isn't killed off entirely by one lucky predator).
- BuyMyBitcoins 3y ago
  I don’t want to sound like a creationist, but the process of metamorphosis itself seems so incredibly complicated that I struggle to imagine how the process could have evolved incrementally. Clearly, it did, so there must be an answer. It’s fascinating to ponder.
  - TerrifiedMouse 3y ago
    My guess is that it started simple. Early caterpillars probably didn't metamorph into something so drastically different. Even earlier ones probably barely had something that resembles metamorphosis.
    - XorNot 3y ago
      They likely didn't metamorph at all - it would've started as "since you're just going to moving as fast as you can so you can find a mate, burning through fat stores faster is good...also thinking about it, you're not going to miss that mouth you're not using anymore either?" There would've been some sort of weight/reproductive efficiency trade off going on (and it would've been heavily environment dependent).
    - throw310822 3y ago
      I might be wrong, but why should the caterpillar be the first to evolve? We don't have issues with the idea of an embryo developing into a winged animal, e.g. an egg into a bird. Then it's not that hard to imagine that eggs, in certain favourable conditions, could evolve the ability to absorb nutrients from the environment before hatching. And that behaviour could be optimised until the egg might become able to move and feed by itself before completing its growth into a bird. And you have some sort of bird-caterpillar.
  - sdwr 3y ago
    Pop science evolution has focused on individual + gene-level selection, which are made out to be so efficient that there's no room for experiments. I bet there's some species-level, distributed, scratch-pad-style R&D going on. Maybe sexual selection is rigged to favor novelty, and incremental progress is cached somehow.
  - jareklupinski 3y ago
    after enough trials and time, there's nothing else that _could_ have happened: every caterpillar that didn't become a butterfly didn't reproduce to tell us about its story all we can see today is the successful outcome of trillions of dice rolls we can't even perceive > The mortality rate of caterpillars is staggering. Some experts believe it hovers around 99% for many species. They are nature’s hotdogs and seemingly everyone wants a bite. Birds and other insects are especially voracious predators. https://www.dispatch.com/story/lifestyle/2020/10/04/curve-lined-owlet-caterpillar-rare-find-adams-county/5869499002/ https://www.dispatch.com/story/lifestyle/2020/10/04/curve-li... facing those kinds of odds, you have to get creative...
  - carapace 3y ago
    The "trick" is that intelligence is ambient in living tissue (it's concentrated in ganglion and brain but all cellular tissue thinks.) In other words, there is an intelligent designer because it evolved from life (not the other way 'round.) See the work of Michael Levin and co, and what Wolfram has discovered about how common computation is in natural systems, and it becomes pretty obvious that there's no intrinsic "that's too clever" limit to what evolution can do. https://en.wikipedia.org/wiki/Michael_Levin_(biologist) https://en.wikipedia.org/wiki/Michael_Levin_(biologist) https://en.wikipedia.org/wiki/A_New_Kind_of_Science#Principle_of_computational_equivalence https://en.wikipedia.org/wiki/A_New_Kind_of_Science#Principl... Wolfram's something of an megalomaniac, but he's not wrong about the "principle of computational equivalence": > Based on his experimental results, Wolfram developed the principle of computational equivalence (PCE): the principle states that systems found in the natural world can perform computations up to a maximal ("universal") level of computational power.
  - DontchaKnowit 3y ago
    I really think the fear of being labeled a creationist has pushed scientists to be afraid to address real problems (or holes) with the theory of evolution. The "random mutation begets eveolution" idea cannot address the problem of irreducible complexity. It just doesnt make any sense. But no one wants to acknowledge this for fear of being called a fundamentalist christian wingnut.
    - XorNot 3y ago
      An argument from incredulity is not an argument (and is equivalent to saying "because I am ignorant of how it works, it must not be true").
      - DontchaKnowit 3y ago
        It is not an argument from incredulity. Darwinian evolution proposes that mutations in a single organism propogate throughout a species over time via procreation, and that deleterious mutations do not propogate (or propogate less efficiently). Advantageous mutations propogate more efficiently. This is not a sufficient explanation of the evolution of highly complex structures or processes. There are myriad examples of structures which are only useful in their entirety, and in part are deleterious or highly damaging to the fitness of an organism. If no explanation for how these complex structures can be achieved in 1 single generation, then evolution by itself fails as an explanatory tool.
        XorNot 3y ago
        No example of a structure only useful in its entirety has ever been forwarded in such an argument successfully. I note here you offer no examples. Name any one, and I can link you to the well argued and numerous rebuttals (pro-tip: the eye is literally the worst possible example).
        DontchaKnowit 3y ago
        I mean, my example here is what this thread is about: caterpillar metamorphosis, but I spent some time reading up on it an it seems as though the consensus at this point is that it evolved out of a partial-metamorphosis process. But it did not seem fully explained to me, and in the last 20 years there have been legitimate scientists (See : Donald Williamson) which proposed non-natural selection processes in order to explain it, though this has been mostly refuted. And really, I think you have just sort of illustrated my point which is : when you bring up irreducible complexity - Because that argument has been used so much by the creationists - People get vitriolic in their defense of natural selection. Natural selection is OBVIOUSLY correct on its face. It is not possible to refute. But as far as I can tell, it is still an open question as to whether or not random mutation is the ONLY means by which the genome of a species can change over time. In my view, it seems highly unlikely that random mutation is the only factor, and irreducible complexity is an argument in favor of some other process by which genomes change e.g. response to environmental factors, gene hybridization, etc. it is not an argument in favor of "intelligent design" which is the default assumption and why the argument is not taken seriously in any case.
  - throw310822 3y ago
    Doesn't seem that complicated if you think of the final stage as the first to evolve. After all, all multicellular beings build their bodies from scratch passing through a number of intermediate stages. The surprising thing (for us) is that the intermediate stages can present themselves as viable organisms capable of living and feeding autonomously. In other words, there is nothing preventing an embryo from optimising one of its growth stages into a individual capable of feeding by itself before completing its transformation into its final shape.
  - huytersd 3y ago
    It’s similar in way to the development of an embryo with a mass of cells and massive chemical and electrical organization. Seems like metamorphosis is just that process except the initial cells come from the caterpillar. One organism going through two different embryo development processes over its lifetime to generate two very different end results. It’s even crazier that some butterflies don’t even have any mouthparts or a way to feed. They are just meant to get far away and reproduce.
pcrh 3y ago
It's even more mysterious once you realize that metamorphosis is a later evolutionary development. Early insects hatched out as miniature adults and molted as they grew, as do arachnids and crustaceans today. So to evolve a larval stage they had to evolve a whole separate new organism from the ancestral one, so to speak.

300 million years and a lot of failed branches

It's an extreme version of reproductive optimization: a lot of animals have a reproductive strategy of "bank resources, then mate and die". Even things with complex neural systems like octopuses (who despite their intelligence, have no parents because they die after protecting their eggs). So how you get here sort of makes sense in that context: if reproduction is more successful if you delay it to collect resources, then it also follows that discarding any biomass you don't need once you've got enough to ensure the reproduction happens quickly and successfully afterwards would lead to this sort of strategy in extremis. A "prototype" caterpillar doesn't need to be able to fly - it just needs to do something which makes it more mobile and slightly more successful (and well, getting away from where you're born and spreading out is a good way to ensure the gene line isn't killed off entirely by one lucky predator).

BuyMyBitcoins 3y ago
I don’t want to sound like a creationist, but the process of metamorphosis itself seems so incredibly complicated that I struggle to imagine how the process could have evolved incrementally. Clearly, it did, so there must be an answer. It’s fascinating to ponder.
- TerrifiedMouse 3y ago
  My guess is that it started simple. Early caterpillars probably didn't metamorph into something so drastically different. Even earlier ones probably barely had something that resembles metamorphosis.
  - XorNot 3y ago
    They likely didn't metamorph at all - it would've started as "since you're just going to moving as fast as you can so you can find a mate, burning through fat stores faster is good...also thinking about it, you're not going to miss that mouth you're not using anymore either?" There would've been some sort of weight/reproductive efficiency trade off going on (and it would've been heavily environment dependent).
  - throw310822 3y ago
    I might be wrong, but why should the caterpillar be the first to evolve? We don't have issues with the idea of an embryo developing into a winged animal, e.g. an egg into a bird. Then it's not that hard to imagine that eggs, in certain favourable conditions, could evolve the ability to absorb nutrients from the environment before hatching. And that behaviour could be optimised until the egg might become able to move and feed by itself before completing its growth into a bird. And you have some sort of bird-caterpillar.
- sdwr 3y ago
  Pop science evolution has focused on individual + gene-level selection, which are made out to be so efficient that there's no room for experiments. I bet there's some species-level, distributed, scratch-pad-style R&D going on. Maybe sexual selection is rigged to favor novelty, and incremental progress is cached somehow.
- jareklupinski 3y ago
  after enough trials and time, there's nothing else that _could_ have happened: every caterpillar that didn't become a butterfly didn't reproduce to tell us about its story all we can see today is the successful outcome of trillions of dice rolls we can't even perceive > The mortality rate of caterpillars is staggering. Some experts believe it hovers around 99% for many species. They are nature’s hotdogs and seemingly everyone wants a bite. Birds and other insects are especially voracious predators. https://www.dispatch.com/story/lifestyle/2020/10/04/curve-lined-owlet-caterpillar-rare-find-adams-county/5869499002/ https://www.dispatch.com/story/lifestyle/2020/10/04/curve-li... facing those kinds of odds, you have to get creative...
- carapace 3y ago
  The "trick" is that intelligence is ambient in living tissue (it's concentrated in ganglion and brain but all cellular tissue thinks.) In other words, there is an intelligent designer because it evolved from life (not the other way 'round.) See the work of Michael Levin and co, and what Wolfram has discovered about how common computation is in natural systems, and it becomes pretty obvious that there's no intrinsic "that's too clever" limit to what evolution can do. https://en.wikipedia.org/wiki/Michael_Levin_(biologist) https://en.wikipedia.org/wiki/Michael_Levin_(biologist) https://en.wikipedia.org/wiki/A_New_Kind_of_Science#Principle_of_computational_equivalence https://en.wikipedia.org/wiki/A_New_Kind_of_Science#Principl... Wolfram's something of an megalomaniac, but he's not wrong about the "principle of computational equivalence": > Based on his experimental results, Wolfram developed the principle of computational equivalence (PCE): the principle states that systems found in the natural world can perform computations up to a maximal ("universal") level of computational power.
- DontchaKnowit 3y ago
  I really think the fear of being labeled a creationist has pushed scientists to be afraid to address real problems (or holes) with the theory of evolution. The "random mutation begets eveolution" idea cannot address the problem of irreducible complexity. It just doesnt make any sense. But no one wants to acknowledge this for fear of being called a fundamentalist christian wingnut.
  - XorNot 3y ago
    An argument from incredulity is not an argument (and is equivalent to saying "because I am ignorant of how it works, it must not be true").
    - DontchaKnowit 3y ago
      It is not an argument from incredulity. Darwinian evolution proposes that mutations in a single organism propogate throughout a species over time via procreation, and that deleterious mutations do not propogate (or propogate less efficiently). Advantageous mutations propogate more efficiently. This is not a sufficient explanation of the evolution of highly complex structures or processes. There are myriad examples of structures which are only useful in their entirety, and in part are deleterious or highly damaging to the fitness of an organism. If no explanation for how these complex structures can be achieved in 1 single generation, then evolution by itself fails as an explanatory tool.
      - XorNot 3y ago
        No example of a structure only useful in its entirety has ever been forwarded in such an argument successfully. I note here you offer no examples. Name any one, and I can link you to the well argued and numerous rebuttals (pro-tip: the eye is literally the worst possible example).
        DontchaKnowit 3y ago
        I mean, my example here is what this thread is about: caterpillar metamorphosis, but I spent some time reading up on it an it seems as though the consensus at this point is that it evolved out of a partial-metamorphosis process. But it did not seem fully explained to me, and in the last 20 years there have been legitimate scientists (See : Donald Williamson) which proposed non-natural selection processes in order to explain it, though this has been mostly refuted. And really, I think you have just sort of illustrated my point which is : when you bring up irreducible complexity - Because that argument has been used so much by the creationists - People get vitriolic in their defense of natural selection. Natural selection is OBVIOUSLY correct on its face. It is not possible to refute. But as far as I can tell, it is still an open question as to whether or not random mutation is the ONLY means by which the genome of a species can change over time. In my view, it seems highly unlikely that random mutation is the only factor, and irreducible complexity is an argument in favor of some other process by which genomes change e.g. response to environmental factors, gene hybridization, etc. it is not an argument in favor of "intelligent design" which is the default assumption and why the argument is not taken seriously in any case.
- throw310822 3y ago
  Doesn't seem that complicated if you think of the final stage as the first to evolve. After all, all multicellular beings build their bodies from scratch passing through a number of intermediate stages. The surprising thing (for us) is that the intermediate stages can present themselves as viable organisms capable of living and feeding autonomously. In other words, there is nothing preventing an embryo from optimising one of its growth stages into a individual capable of feeding by itself before completing its transformation into its final shape.
- huytersd 3y ago
  It’s similar in way to the development of an embryo with a mass of cells and massive chemical and electrical organization. Seems like metamorphosis is just that process except the initial cells come from the caterpillar. One organism going through two different embryo development processes over its lifetime to generate two very different end results. It’s even crazier that some butterflies don’t even have any mouthparts or a way to feed. They are just meant to get far away and reproduce.

pcrh 3y ago

It's even more mysterious once you realize that metamorphosis is a later evolutionary development. Early insects hatched out as miniature adults and molted as they grew, as do arachnids and crustaceans today. So to evolve a larval stage they had to evolve a whole separate new organism from the ancestral one, so to speak.