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The example of convergence between fish and dolphins, birds and insects, the infamous "why does everything evolve into crabs" study and so on should tell us tha

The example of convergence between fish and dolphins, birds and insects, the infamous "why does everything evolve into crabs" study and so on should tell us that while we should be open for radically different forms of life, the most likely outcomes will look like something we've seen here on Earth. I'm personally expecting something like 80% humanoids and 20% exotic forms. Maybe I'm primed incorrectly by cheesy soap operas and sci-fi TV shows, but I think they're not far off (even if for unrelated reasons like SFX/VFX budget and character empathy).

rendall 5y ago
... on planets. That have a precise similarity to Earth. Sure, I can provisionally accept that.
dogorman 5y ago
> convergence between fish and dolphins The convergence between dolphins and ichthyosaurs is even more remarkable. Ichthyosaurs were marine reptiles; air breathing tetrapods that, like dolphins, had ancestors that walked on land but eventually returned to the sea to kick fish ass. https://en.wikipedia.org/wiki/Ichthyosaur#/media/File:Ichthyosaur_vs_dolphin.svg https://en.wikipedia.org/wiki/Ichthyosaur#/media/File:Ichthy...
- ncmncm 5y ago
  Bony fish evolved in rivers, and eventually returned to the sea to kick... what? Analogies fail. Those fish are overwhelmingly more closely related to horses than to sharks.
mike_hock 5y ago
Sure, organisms that already share a massive amount of commonalities can diverge and then converge again. What about the branches that happened early on? We essentially have only two lineages of macroscopic organisms that are actually fundamentally different: Plants and animals. I would expect any kind of macroscopic extraterrestrial life to be at least as distinct from Terran plant and animal life as they are from each other.
- yourenotsmart 5y ago
  DNA is extremely flexible, there's no macroscopic form or shape it can't take, as various insects camouflaging themselves as sticks and leaves and what not shows. So the idea we'll see some vastly different concepts with different starting blocks is possibly unfounded. Alien life might be very different at low level depending on their environment, but in terms of macroshapes, things like the formation of a head with eyes and mouth, upper and lower limbs, bilateral symmetry and so on will repeat over and over. We'll see (in another life probably).
  - spywaregorilla 5y ago
    > DNA is extremely flexible, there's no macroscopic form or shape it can't take, as various insects camouflaging themselves as sticks and leaves and what not shows. That feels like a really bold claim given the evidence.
    - ncmncm 5y ago
      Let me know when you spot an animal that drives around on wheels.
      - dtech 5y ago
        Physically you could have wheeled animals, but wheels just won't evolve. They are perfect for somewhat smooth surfaces where you want to travel in a somewhat straight line. Organisms just cannot confine themselves to that and survive. Unless we find a planet composed entirely of solid smooth rock we won't find wheeled animals.
        jhgb 5y ago
        How would wheels get fed with nutrition? Would they have tiny mouths?
        mod 5y ago
        Gears have evolved, though, which is equally cool IMO.
spywaregorilla 5y ago
Given how rare humanoid shape is on Earth, it doesn't seem especially sure that humanoids will be dominant among even intelligent life.
- dtech 5y ago
  Arms+hands and a head with a similar face though. A head is pretty universal because eyes are so important and a feeding hole near your sensory organs is a massive advantage. Having hands seems almost a pre-requisite to become truly intelligent and tool-using.
  - titzer 5y ago
    Octopi have all the things you mentioned (except hands). Their eyes are even better than human eyes. No one would describe them as "humanoid".
    - godelski 5y ago
      Also consider an octopi's environment. That environment is not well suited for being able to build lots of things. How do you get to the bronze age underwater? How about even earlier. Land based creatures have pretty similar forms. Snake like, bipedal, quadru/multiped, and flying/winged creatures. Snakes don't have arms and so aren't going to have fine motor control. Winged creatures are going to have a hard time dealing with heavy objects (they have hollow bones to fly and wings are incredibly fragile and I don't see nature creating super materials, plastics, or metal structural systems for animals). Quadrupeds probably aren't going to develop arms like centaurs (more likely legs become arms). So if we want a creature that can have fine motor control, live in an environment that can easily create metals, not be extremely fragile, and is able to devote a significant amount of its energy intake to its brain, you're probably going to come up with something ape like (bipedal). There are other forms here, but we can see that there are some pretty good hints that we learn just from mechanics and aren't so much dependent on specifics of Earth or humans.
      - ClumsyPilot 5y ago

rendall 5y ago

... on planets. That have a precise similarity to Earth. Sure, I can provisionally accept that.

dogorman 5y ago

> convergence between fish and dolphins The convergence between dolphins and ichthyosaurs is even more remarkable. Ichthyosaurs were marine reptiles; air breathing tetrapods that, like dolphins, had ancestors that walked on land but eventually returned to the sea to kick fish ass. https://en.wikipedia.org/wiki/Ichthyosaur#/media/File:Ichthyosaur_vs_dolphin.svg https://en.wikipedia.org/wiki/Ichthyosaur#/media/File:Ichthy...

ncmncm 5y ago
Bony fish evolved in rivers, and eventually returned to the sea to kick... what? Analogies fail. Those fish are overwhelmingly more closely related to horses than to sharks.

mike_hock 5y ago

Sure, organisms that already share a massive amount of commonalities can diverge and then converge again. What about the branches that happened early on? We essentially have only two lineages of macroscopic organisms that are actually fundamentally different: Plants and animals. I would expect any kind of macroscopic extraterrestrial life to be at least as distinct from Terran plant and animal life as they are from each other.

yourenotsmart 5y ago
DNA is extremely flexible, there's no macroscopic form or shape it can't take, as various insects camouflaging themselves as sticks and leaves and what not shows. So the idea we'll see some vastly different concepts with different starting blocks is possibly unfounded. Alien life might be very different at low level depending on their environment, but in terms of macroshapes, things like the formation of a head with eyes and mouth, upper and lower limbs, bilateral symmetry and so on will repeat over and over. We'll see (in another life probably).
- spywaregorilla 5y ago
  > DNA is extremely flexible, there's no macroscopic form or shape it can't take, as various insects camouflaging themselves as sticks and leaves and what not shows. That feels like a really bold claim given the evidence.
  - ncmncm 5y ago
    Let me know when you spot an animal that drives around on wheels.
    - dtech 5y ago
      Physically you could have wheeled animals, but wheels just won't evolve. They are perfect for somewhat smooth surfaces where you want to travel in a somewhat straight line. Organisms just cannot confine themselves to that and survive. Unless we find a planet composed entirely of solid smooth rock we won't find wheeled animals.
      - jhgb 5y ago
        How would wheels get fed with nutrition? Would they have tiny mouths?
      - mod 5y ago
        Gears have evolved, though, which is equally cool IMO.

spywaregorilla 5y ago

Given how rare humanoid shape is on Earth, it doesn't seem especially sure that humanoids will be dominant among even intelligent life.

dtech 5y ago
Arms+hands and a head with a similar face though. A head is pretty universal because eyes are so important and a feeding hole near your sensory organs is a massive advantage. Having hands seems almost a pre-requisite to become truly intelligent and tool-using.
- titzer 5y ago
  Octopi have all the things you mentioned (except hands). Their eyes are even better than human eyes. No one would describe them as "humanoid".
  - godelski 5y ago
    Also consider an octopi's environment. That environment is not well suited for being able to build lots of things. How do you get to the bronze age underwater? How about even earlier. Land based creatures have pretty similar forms. Snake like, bipedal, quadru/multiped, and flying/winged creatures. Snakes don't have arms and so aren't going to have fine motor control. Winged creatures are going to have a hard time dealing with heavy objects (they have hollow bones to fly and wings are incredibly fragile and I don't see nature creating super materials, plastics, or metal structural systems for animals). Quadrupeds probably aren't going to develop arms like centaurs (more likely legs become arms). So if we want a creature that can have fine motor control, live in an environment that can easily create metals, not be extremely fragile, and is able to devote a significant amount of its energy intake to its brain, you're probably going to come up with something ape like (bipedal). There are other forms here, but we can see that there are some pretty good hints that we learn just from mechanics and aren't so much dependent on specifics of Earth or humans.
    - ClumsyPilot 5y ago