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OK, it's on.
Other Worlds
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Rook
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Cognisant
cackling in the trenches
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All fish are fish, and all birds are birds.
Most things that live in the sea and swim have a vaguely fish like shape and body plan, be it a mammal (dolphins and seals), a bird (penguins), a reptile (ichthyosaurs) or even an aquatic insect. I.e. mouth in front, streamlined body, fins for propulsion and orientation.
A water beetle is wildly different to a dolphin, just as bats, bees and pterodactyls are different to birds, but the same general logic applies to their body plan, nature is never weird for the sake of being weird there's always a reason for it and the solution used is generally the simplest available.
So I contend that aliens are likely to be (in general) surprisingly recognizable, there will be crab like things because crab like things have evolved independently several times on earth. Likewise there will be rat and wolf like things because there are variations on the same theme in other ecosystems, basically where the same niche exists the selective pressures that formed a certain species in one ecosystem will likely create a similar creature in another ecosystem because it's the same kind of selective pressure.
Now this is not to say everything will be sensible to us, there's creatures on Earth that are truly bizarre and I have no doubt that an alien world with the same conditions as Earth could produce equally bizarre things unlike we've ever seen before and a life bearing world with conditions unlike Earth's could do even better, but there's still only so much novelty to go around.
Eventually the optimization of life through natural selection will tend towards optimal solutions and there can only be so many truly optimal solutions.
If we ever find intelligent tool using aliens I'd be very surprised if they didn't have some kind of hand, or at least some way to manipulate their environment without specialized tools. Indeed it's entirely likely that we won't be the most gifted in this regard, our fingers lack the flexibility of tentacles that can stretch and curl, and the precision of claws and pincers, nor do we have any kind of inbuilt hammer, saw or scissors.
Then again nothing evolves without necessity, a crustacean like thing with a swiss-army-knife array of different appendages and manipulators would need to have come from a very particular environment to have evolved with such specificity, so I suspect generalists like ourselves will be more likely.
Most things that live in the sea and swim have a vaguely fish like shape and body plan, be it a mammal (dolphins and seals), a bird (penguins), a reptile (ichthyosaurs) or even an aquatic insect. I.e. mouth in front, streamlined body, fins for propulsion and orientation.
A water beetle is wildly different to a dolphin, just as bats, bees and pterodactyls are different to birds, but the same general logic applies to their body plan, nature is never weird for the sake of being weird there's always a reason for it and the solution used is generally the simplest available.
So I contend that aliens are likely to be (in general) surprisingly recognizable, there will be crab like things because crab like things have evolved independently several times on earth. Likewise there will be rat and wolf like things because there are variations on the same theme in other ecosystems, basically where the same niche exists the selective pressures that formed a certain species in one ecosystem will likely create a similar creature in another ecosystem because it's the same kind of selective pressure.
Now this is not to say everything will be sensible to us, there's creatures on Earth that are truly bizarre and I have no doubt that an alien world with the same conditions as Earth could produce equally bizarre things unlike we've ever seen before and a life bearing world with conditions unlike Earth's could do even better, but there's still only so much novelty to go around.
Eventually the optimization of life through natural selection will tend towards optimal solutions and there can only be so many truly optimal solutions.
If we ever find intelligent tool using aliens I'd be very surprised if they didn't have some kind of hand, or at least some way to manipulate their environment without specialized tools. Indeed it's entirely likely that we won't be the most gifted in this regard, our fingers lack the flexibility of tentacles that can stretch and curl, and the precision of claws and pincers, nor do we have any kind of inbuilt hammer, saw or scissors.
Then again nothing evolves without necessity, a crustacean like thing with a swiss-army-knife array of different appendages and manipulators would need to have come from a very particular environment to have evolved with such specificity, so I suspect generalists like ourselves will be more likely.
Rook
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Rook
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Thurlor
Nutter
@Cognisant
I'm not sure how common bilateral symmetry will be amongst alien life. Sure, most life on earth is bilaterally symmetrical but from my understanding that is only due to a mass extinction event and luck of the draw. The optimal solution for aero/hydro-dynamics may be very different for a lineage of life that isn't bilaterally symmetrical.
If we ever find crystalline life (or other such oddities) I would be surprised if it ever evolved crab like analogues.
I'm not sure how common bilateral symmetry will be amongst alien life. Sure, most life on earth is bilaterally symmetrical but from my understanding that is only due to a mass extinction event and luck of the draw. The optimal solution for aero/hydro-dynamics may be very different for a lineage of life that isn't bilaterally symmetrical.
If we ever find crystalline life (or other such oddities) I would be surprised if it ever evolved crab like analogues.
Rook
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Cognisant
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There certainly could be worlds where non-bilateral life is dominant but I think they'll be the exception, the caloric cost of growing several redundant limbs is extremely high, this puts radially symmetrical life at a severe disadvantage.
Crystalline life will be constrained by its chemistry, only able to thrive in ecosystems where nothing else can, like anaerobic bacteria being unable to compete with aerobic bacteria because their metabolisms are just so much faster.
Exoskeletons don't scale up well so you're probably not going to see hard bodied human sized aliens, unless they're aquatic or from a low gravity world.
Our lack of scales or fur is quite bizarre, almost everything in nature has some kind of protective/insulating covering, unless its aquatic or an amphibian, as such I doubt we'll be winning many interstellar beauty contests.
Crystalline life will be constrained by its chemistry, only able to thrive in ecosystems where nothing else can, like anaerobic bacteria being unable to compete with aerobic bacteria because their metabolisms are just so much faster.
Exoskeletons don't scale up well so you're probably not going to see hard bodied human sized aliens, unless they're aquatic or from a low gravity world.
Our lack of scales or fur is quite bizarre, almost everything in nature has some kind of protective/insulating covering, unless its aquatic or an amphibian, as such I doubt we'll be winning many interstellar beauty contests.
scorpiomover
The little professor
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Humans have fur. It's just very tiny, so small, that you wouldn't notice it without a magnifying glass. It's vestigial.
Amphibians are small vertebrates that need water, or a moist environment, to survive. Humans need to shower regularly.
I don't think most men care, so long as they're dating a supermodel.