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Think of evolution as an optimization algorithm that finds organisms for ecological niches. The monophyletic grouping approach tells you something about the pa

by svara 5y ago

Think of evolution as an optimization algorithm that finds organisms for ecological niches. The monophyletic grouping approach tells you something about the path through solution space taken by the algorithm. The paraphyletic approach instead focuses on properties of the solutions. I think it's fine to think of those as equally valid.

thaumasiotes 5y ago
> I think it's fine to think of those as equally valid. Only for extremely limited purposes. Both approaches are about properties of the organism as it currently exists. The paraphyletic approach will let you know about similarity in maybe three dimensions of a ten-thousand-dimensional space. The monophyletic approach captures the other 9,997.
- svara 5y ago
  > Both approaches are about properties of the organism as it currently exists. Not really, no. The monophyletic approach does that only indirectly. Think of marsupial/mammal convergence. Is it really wrong to think of marsupial mice and mammalian mice as a somehow similar kind of thing? Or consider secondary unicellularity. Losing multicellularity is as drastic a change as can be, and it makes no sense to try to understand the ecology of a unicellular organism by grouping it with its multicellular ancestors. Living things are not the way they are just because of their evolutionary history, but also because of the ecological niche that evolution optimized them for. When similar niches are filled by organisms that are not closely related, that often leads to similar solutions, which is interesting in its own right.
  - thaumasiotes 5y ago
    > Think of marsupial/mammal convergence. You are aware that marsupials are mammals?
  - ashtonbaker 5y ago
    > Think of marsupial/mammal convergence. Is it really wrong to think of marsupial mice and mammalian mice as a somehow similar kind of thing? It seems to me that most of the similarity can be explained by their shared phylogenetic history. Before the K-T extinction, that ecological niche was probably occupied by a very different small animal, and its occupation of that niche may have even been quite stable. So, occupation of a particular niche by an organism doesn't really imply optimization over the space of possible organisms, but rather over the space of relatively cheap modifications to existing body plans. Think of it this way - say Australia had never been connected to the rest of the continents, so no organism with a common ancestor with mammals could exist there. How similar would the organisms filling the niche of marsupial mice be then? Probably some strategic similarities like burrowing etc, but probably enough to pass as a pseudo-mammal.
    - thaumasiotes 5y ago
      > Think of it this way - say Australia had never been connected to the rest of the continents, so no organism with a common ancestor with mammals could exist there. This was more or less true of New Zealand until the 13th century. The only indigenous mammals were bats.
HelloNurse 5y ago
Not for the same purposes: you are comparing the biological equivalents of history and engineering.

by svara 5y ago

thaumasiotes 5y ago

> I think it's fine to think of those as equally valid. Only for extremely limited purposes. Both approaches are about properties of the organism as it currently exists. The paraphyletic approach will let you know about similarity in maybe three dimensions of a ten-thousand-dimensional space. The monophyletic approach captures the other 9,997.

svara 5y ago
> Both approaches are about properties of the organism as it currently exists. Not really, no. The monophyletic approach does that only indirectly. Think of marsupial/mammal convergence. Is it really wrong to think of marsupial mice and mammalian mice as a somehow similar kind of thing? Or consider secondary unicellularity. Losing multicellularity is as drastic a change as can be, and it makes no sense to try to understand the ecology of a unicellular organism by grouping it with its multicellular ancestors. Living things are not the way they are just because of their evolutionary history, but also because of the ecological niche that evolution optimized them for. When similar niches are filled by organisms that are not closely related, that often leads to similar solutions, which is interesting in its own right.
- thaumasiotes 5y ago
  > Think of marsupial/mammal convergence. You are aware that marsupials are mammals?
- ashtonbaker 5y ago
  > Think of marsupial/mammal convergence. Is it really wrong to think of marsupial mice and mammalian mice as a somehow similar kind of thing? It seems to me that most of the similarity can be explained by their shared phylogenetic history. Before the K-T extinction, that ecological niche was probably occupied by a very different small animal, and its occupation of that niche may have even been quite stable. So, occupation of a particular niche by an organism doesn't really imply optimization over the space of possible organisms, but rather over the space of relatively cheap modifications to existing body plans. Think of it this way - say Australia had never been connected to the rest of the continents, so no organism with a common ancestor with mammals could exist there. How similar would the organisms filling the niche of marsupial mice be then? Probably some strategic similarities like burrowing etc, but probably enough to pass as a pseudo-mammal.
  - thaumasiotes 5y ago
    > Think of it this way - say Australia had never been connected to the rest of the continents, so no organism with a common ancestor with mammals could exist there. This was more or less true of New Zealand until the 13th century. The only indigenous mammals were bats.

HelloNurse 5y ago

Not for the same purposes: you are comparing the biological equivalents of history and engineering.