When you think about what intelligent aliens might really be like, what sorts of forms go through your head? Mine are often tripedal, hexapedal, octopedal or have an even greater number of limbs. Most have light and strong exoskeletons(made from silky or carbon composites), but some use muscular hydrostatic limbs with sticky pads, suckers or tongue-like growths on them to get around and manipulate objects. Endoskeletons are in my thoughts as well, but they're not made of the same material as our's are and they evolved from animals(or however the life would be classified, they could be fungus or plant-like as well) very unlike the fish we came from. Four or more eyes are the norm, two on the sides of their head, carapace, whatever they have, the other two are on the front, what we'd call the front anyway, for binocular vision. They're usually omnivores or carnivores.

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When I was a kid, if someone brandished a shrink gun he'd get a little bit of respect!-Myron Reducto, Harvey Birdman

Geez, not quite sure how to answer this one.

The problem with playing the "guessing game" of alien life is not just that we don't know how alien life could evolve, and where, but also that our imagination, no matter how incredible it might seem sometimes, is also rather limited to what we have here on Earth. We imagine aliens as taking the form of insects, lizards, humans, etc. We imagine eyes and limbs and everything; all of those things (and more) that you see here on Terra Firma; or just a slight variation of what you see here.

For the most part, I think that if an alien being is "beyond imagination of all humans", then that's that; no matter what I do, I can't imagine it.

However, just for fun:

I imagine a starfish! Almost literally; a starfish that floats through space and can "crack open" shelled creatures (usually asteroids) for substance... but doesn't mind the odd spacecraft here and there. Oh, and they're gigantic. Why? Because I can!

Puppeteers' home planet (before they exterminated everything remotely dangerous to themselves): All vertebrates are descended from an ancestor with Y-shaped notochord and Y-shaped digestive tract. All animals have two heads, two mouths, two eyes (one eye to a head), one stomach with two entrances and one brain in the base of the Y. Land forms have three legs, aquatic forms have three fins. Flying forms have two wings and one leg to sit on.

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It may be a funny way of speculating intelligent creatures with a lot of limbs, and a generally very complicated "design"(You may find a better word ).
One can also think about what may be likely.
Is it just by chance that terrestrian lifeforms, especially all bigger and "higher" - as far as i know, in fact has a very simple overall bodyplan?
´Did that really happened by accident?
Perhaps one may think terrestrian lifeforms during 4-5 billion years evolved in a rather "erratic" way, escaping all the real good and effective sollutions. (like, say, 1000 heads, centipeds, facet eyes, like on flies, dosens of wings and legs and arms, not to speak of all the mouths, and sense organs, that surely would make us all work much better). Alternatively one could imagine for once, that there might be reasons that organisms are as they are- here -and that some economy "streamlinedness" might be the most effective and fitting (what about to versus say, 100 sexes?)

To a certain extent, I think the answer is yes. The reason why animals like giant octopusses have taken over the land isn't because that many limbs doesn't work, when they plainly do. It also isn't because they're not smart, which they are. It's because they lack skeletons of the type that would let them do very well on land. They have a muscular hydrostatic form, but such things aren't strong enough using only normal biological muscles to get around well on land. Arthropods once did rule the world, before vertebrates existed. There were once centipede-like animals about two meters long. Relatives of scorpions about a meter long. You don't see truely giant arthropods on land anymore for several reasons. Vertebrates work better at the size range that arthropods once had, arthropods, at least of the forms that have evolved on earth, can't grow as large as vertebrates can due to the square cube law. Their legs can't keep being scaled up and still work. The limit for arthropods on land is about a meter in height, after that they're too heavy for their own legs. Yet another hold back for arthropods is how they breath. When those giant arthropods that I mentioned lived, Earth's atmosphere had much more oxygen than now. Such animals, if created artificially now, might very well die with our oxygen levels. The reason we have four limbs is because the fish we came from did. If on another world vertebrates evolved to have a different number of limbs than their ancestors could have more. Six limbs, maybe even eight, might evolve. If it had a vertabrate physiology then it could scale up like we reptiles, birds and mammals have.

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If we don't play god, who will?-James Watson
I never think of the future, it comes soon enough.-Albert Einstein
The large print giveth and the small print taketh away.-Tom Waits
Any sufficiently advanced technology is indistinguishable from a yo-yo.-Enoch Root, The Confusion
When I was a kid, if someone brandished a shrink gun he'd get a little bit of respect!-Myron Reducto, Harvey Birdman

So in this case I might actually be the more sceptic(!)
I once had a good time reading StevenJ. Gould, but find it hard to believe, that the dominaing bigger animals are so relatively simple buildt, just by chance. That there are not some principles of "economy" at work.
Perhaps, though this may sound far out (but it could be it is not), one could compare with engineering. Is it not so, that many machines, and other artifacts, once were had a much more "complex" appearance, and has "evolved" toward something more "streamlined". Like cars, like planes, and probably a lot of other things. Of course there may be some "accidental" or "historical" factors too, but I doubt they are the only ones (is there not only some basic chemistry in life? -amino acids and genetic material. If it not exactly the same chemistry other places, there may be some similar principles of simplicity? Cells and cell-division?)
And remember: The strongest argument that we are not alone is that it seems improbable, given the size of the universe, and if we accept the fact that life here has worked for so long. But I can hardly see that this argument can be extended to extremely different designs. We cannot rule out that they simply don´t work.

I honestly think that evolution works on the terms of "If it works, why get rid of it?"

For instance, with the human body; if we did share the same ancestor as the chimp, then our evolution most likely was slight. Lost fur, gained straightness, etc. Baby steps, but after a while, even baby steps makes progress. However, at no point does "fifty heads" ever become a viable option in that case.

I like centaurs. They'd be a nice alien. And chances are that if we ever got into a war with them, we'd do better because we could take more acceleration. At least, I think so.

How about pneumatic life-forms, like intelligent airbags. I wonder if they might evolve on a planet with a dense, but habitable, atmosphere.

I also wonder if it might be possible to construct an alien that looks like an arthropod, but has managed to get around the limits of terrestrial types. Maybe it would only evolve on a low G planet. Or maybe it would be some sort of hybrid by combining elements of endoskeletons and better respiratory systems.

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Centaurs aren't that great, really. Too much of a bend required in the spine. Also, not much capability with turning the torso; you can barely turn it, if at all. So what's the point, really? If the only real advantage is the arms, then why bother with the top part? It just seems so... silly and unrealistic to me.

As a tool-user centaur may be inferior to a humanoid, but if it started out as an unintelligent hexapod, the only realistic tool-using end result would be a centaur. And there is nothing unrealistic about hexapod body plan -- most Earth animals are hexapods. They are called insects. Pure chance insects never evolved lungs -- if they had, they (well, their descendants) would be the dominant life form today.

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Depends. When I see how "Centaurs" are drawn, they generally look very... encumbered by their own physiology.

I'm not sure on the whole insects thing. *Shrugs* But I'm pretty sure insects have a different physiology than how centaurs are depicted.

I remember someone once saying that nature never evolved the wheel, or more accurately, an axle. I actually devised a biological structure for making an axle-wheeled animal using a disconnected bone structure. I'm not sure what the point would be, not a lot of terrain for its use, but maybe a sea or airborn creature might make use of it.

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And if there is it is likely some limits to our fertile imagination.
Another thing is: Can we say something about what´s realistic or likely?
Compare again with artifacts: There´s very, very many times more ways one might imagine them, than there is practical designs (and even a lot fewer of these will attrackt investors and become real products. I at least can imagine things done very different, as perhaps You too?)

Some features of our own design might be found to be common among alien intelligent creatures. Bilateral symmetry is common to most animals but not plants, so perhaps intelligent animal-like creatures will often be bilaterally symmetric. Such a creature will probably tend to have a front end and a rear end, with manipulatory appendages near the mouth, and sensors at the front end of some sort. But a radially symmetrical creature with a centrally placed mouth is not entirely impossible, perhaps only if the environmental conditions are very different to Earth. On a planet with a very thick atmosphere all movements will be slowed down, and a starfish-like bodyplan might compete well against a more streamlined bilaterally symmetrical quadruped plan.

But perhaps plant-like creatures or slime molds/fungi equivalents might sometimes also develop intelligence, in my opinion; exactly why such non motile organisms might require processing is another matter, but I think it is possible that some set of circumstances might allow this to happen.

Large brains or nervous systems capable of will be a necessity for complex thought, so larger animals will be able to support larger processing substrates. So a large animal will need sturdy means of locomotion; on an earth-like planet, strong legs with skeletal structures for support. Mostly this will be an internal skeleton of some sort- plausible external skeletons are too heavy for a large creature. This does not rule out a hybrid between an internal and an external skeleton; some armoured dinosaurs had extensive bony parts in their outermost layers, and such an outer shell could also perform support functions
. A large animal could be bipedal like a human, or bipedal like a dinosaur, using a cantilever like main support system. The development of an articulated spine, by the way, is a bonus, but need not be a universal feature. Even without a spine or backbone a creature large enough to carry a large brain could be tripedal, or quadripedal, with secondary limbs at the front end, or have even more legs; I suspect that more legs will be required on planets with gravity somewhat higher than Earth's. Similarly bipedal locomotion might be more advantageous on low gravity planets, although I have heard that the best form of locomotion on low grav worlds is hopping, so a skinny kangaroo-like bodyplan might be best.

It is possible that a head-like structure is a common feature of bilaterally symmetrical land animals; this will be more common in creatures with a backbone analogue.

But perhaps a large neural network could be built up between many smaller creatures, using temporary (or perhaps permanent) information-carrying connections between individual members of a colony or swarm. Such a hive mind is a staple of science fiction, but it might occur somewhere. Colonial sponges with shared nervous systems, hives of insects or flocks of birds or dinosaurs communicating by chemicals, sound or electromagnetic signals spring to mind.
I recommend reading 'Starmaker' by Olaf Stapleton, where he deals with hive mind creatures in some detail; he also suggested bipedal creatures which have evolved from five pointed starfish-like creatures, or from centaurs (where the rear legs have merged with the front), and interestingly, intelligent ships that sail the seas using wind power.

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i think they will look like us, but with bumps on their foreheads.
we will know they are friendly if they wear loose fittng, earth-tone colored clothes and are generally calm and cool about things.
we will know they are unfriendly if they wear darkly colored, tightly fitting or angular clothing, and get really worked up over little things.


everything i know about aliens, i learned from Star Trek.

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The bend in the centauroid's spine would be awkward, but so is our upright stance. In fact, if I hadn't seen two-legged animals (and if I were not two-legged myself), I would not think it possible for such an animal to walk without falling over.

The centauroid would have emerged from an entire class of six-legged animals, just like we emerged from an entire class of four-legged animals, by freeing the front pair of legs, turning them into arms. In both cases, there is a price to be paid.

If I had to guess, I think that among intelligent species the humanoid form will be quite common with the centauroid form coming in a close second. Centauroids will tend to live on slightly more massive worlds than humanoids.
And on some massive worlds with dense atmospheres the angeloid form will be found (two legs, two arms, two wings).

I also expect (intelligent or non-intelligent) beings to exist, whose bodies are in effect giant wheels, rolling over vast plains. Whether wheel-like appendages can evolve seems more doubtful; much could go wrong with them, which might mean that they would always be selected against.

I'm not sure that a centauroid form would develop in heavier gravity fields. I would think that the awkward bend in the spine would be detrimental with a heavier load and that the four legs would not necessarily counter it.

On the other hand, there may be an increased likelihood of large winged animals (angeloid?) on higher gravity worlds for two reasons. Denser atmospheres would increase lift coefficients. Denser oxygen atmospheres would allow for higher metabolism for the larger creatures for flight. Although it may be debateable if they are actually flying or just gliding/soaring. Who wouldn't like to own a Pegasus? an Angeloid might evolve as needing 4 legs to climb to the top of a tall tree and jump off, instead of flapping up against gravity. I'd also be interested a large sentient sixlegged and winged creature like a flying centaur (hexangeloid?) Maybe in the future we could GM such creatures for our own amusment.

As for large arthropoids, I wonder if we replaced the moltable chitin-based exoskeleton with a continuously growing bone-based exoskeleton, like a tortoise but articulable. It might not be an actual exoskeleton since it might be covered with a skin or dermis of some sort.

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I like to imagine a methane sack with an internal skeleton and thick leathery skin. Some of the skin on its fore side is sensitive to light and heat radiation, but can't distinguish color very well. The organism has six tentacles and end with a tough nail like spine that can spear prey and enemies. The spines also have a slight hole in them for ingestion and excretion, and finger like objects can extend to interact with technology.

Then there are other possible hominid species with six appendages, an evolution from prehistoric fish that required four fins and a powerful flipper to maneuver through heavy gravity environments.

The centaur is not the only possible bodyplan for a non-biped with manipulatory appendages. Elephants have a trunk which extends forward from the head region. I can imagine a tetrapod or hexapod with multiple appendages extending forward level with, or even below, the shoulder.
Here is a similar species I drew for Stephen Inniss;
http://www.orionsarm.com/xenos/Jade_Chime_Singers.html
apologies, but pencil artwork is not my best medium...

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To me, Aliens look like Mila Jovovich... they ALL look exactly like her... *drools*

No...I see everything for tribble-like fuzzballs to arachnid-like creatures to humanoid to super-advance machine...

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That's just silly. Now I'm not saying that bipedal aliens won't exist, but to say they'd be humanoid is über-chauvinistic.

__________________
If we don't play god, who will?-James Watson
I never think of the future, it comes soon enough.-Albert Einstein
The large print giveth and the small print taketh away.-Tom Waits
Any sufficiently advanced technology is indistinguishable from a yo-yo.-Enoch Root, The Confusion
When I was a kid, if someone brandished a shrink gun he'd get a little bit of respect!-Myron Reducto, Harvey Birdman

SkepticJ --

Do you really look like your avatar?

And before you ask, no I am not Creature From The Black Lagoon. Even if I do spend as much time as I can underwater.

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If SkepticJ looks like Mila Jovovich as Lelu Dallas... man... I'm so finding them!

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Very true. Of course, without something like telepathy or Fine Manipulators, the opposable thumb seems most likely for tool-using aliens. Without tools, there's somewhat of a damper on what you can, potentially, do.

But, of course, you could easily have hands to use with a different body type. Plus, you could always get an alien species that can "mold" itself into any shape it really needs to accomplish a goal.

Nope, not even the same gender, or age. I just think it's a fun photo, so I use it. Someday I'll switch it.

You SCUBA dive, eh?

__________________
If we don't play god, who will?-James Watson
I never think of the future, it comes soon enough.-Albert Einstein
The large print giveth and the small print taketh away.-Tom Waits
Any sufficiently advanced technology is indistinguishable from a yo-yo.-Enoch Root, The Confusion
When I was a kid, if someone brandished a shrink gun he'd get a little bit of respect!-Myron Reducto, Harvey Birdman

And nothing says their hands need be like ours. I mentioned the tentacle-like arms with tongue-like growths all over them. They'd make our hands seem like oven mitts in comparison. Also, even if their hands are somewhat like ours, why not multiple opposable thumbs? Say they have seven fingers on each hand, two of them are thumbs. Perhaps their fingers are covered in small, tongue-like, muscular hydrostatic growths? Perhaps their hands are covered in tube-feet that have sticky tips. Picking up individual sand grains, or whatever, and moving them where they want them wouldn't be a problem. I really should design out on paper, computer, wherever, some alien appendages.

__________________
If we don't play god, who will?-James Watson
I never think of the future, it comes soon enough.-Albert Einstein
The large print giveth and the small print taketh away.-Tom Waits
Any sufficiently advanced technology is indistinguishable from a yo-yo.-Enoch Root, The Confusion
When I was a kid, if someone brandished a shrink gun he'd get a little bit of respect!-Myron Reducto, Harvey Birdman

Sounds cool. These all would fall under Fine Manipulators. So would Thumbs. Hence, my statement was mis-stated. Oh well.

There are a lot of possibilities for "Fine Manipulators" that are physical. But that's relatively easy to come up with. Try for some theories on having Fine Manipulators that are NOT physical! There's a fun challenge.

BTW, Psionics will fall under Magic for this one, and will be deemed "cheating". Psionics are mostly "theoretical", if even that.

What do you mean by nonphysical fine manipulators? If it exists, isn't it physical by definition?

Hmm. A collection of vacuum/blower tubules that allows the creature to move objects through air pressure changes? Electromagnetic manipulators on a world rich in iron and ferromagnetic materials? Creatures with giant, adjustable biological speaker-horns that they can use to vibrate objects around sonically?

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In that case, then, something that's not solid, I.E., a hand, a tentacle, any appendage, your mouth, your rear end, toes, teeth, tongue, etc.

Those sound pretty cool, though the last one seems hard to really "condense" in predictable ways... and might have very very bad side effects...

The number of environments on earth is quite astounding. I think when we find life elsewhere it will remind us of something we've had here. Imagine if Trilobites became the sentients?

The OP question was about intelligent aliens, right? (scrolls up to make sure...)
So let's think about the things that we have. Upright posture frees up half our limbs from locomotion. Forward facing vision allows for detailed view of things within our grasp. Prolonged dependence on parental care gives time for language and culture transfer.

On earth we have rats and kangaroos that meet some of those criteria. Perhaps the neighbors, when we meet them, will look like kangaroos.

I doubt intelligent lifeforms could develop that look like some of the weird things on startrek and stuff. Saw an episode last night with the "horta," a "silicon based life form." Looked like a humanoid under a packing blanket.


Part of what we have available is a "generalist" body plan, rather than being highly tuned for specific environments. That seems like a pretty powerful tool that any potentially sentient species is going to need to make the step from "animal" to "person."

I could see a vertebrate species developing more than two limb girdles. Nothing on earth meets the plan, but I don't see why it couldn't happen during skeletal evolution on another world. That would make a forward pair of limbs available as manipulators leaving a centauroid hindlimb system.

The manipulator thinking is interesting, but again I think we could look around at things on earth for answers. The entire vertebrate line has fingers and toes to start with, and evolved specialized structures for feeding and locomotion like whales and cats. Non-vertebrates that have non-mouthpart manipulators are fewer and less adaptable. Crab claws are pretty good, octopus tentacles are good, feathers and beaks and cilia are rather limited.

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