Not to mention unimaginative writers!

And lousy cartoonists like myself. It's hard enough to conciously draw manga. So that's why I drew a girl with blue hair, green skin, a patern like a circut-board on her forhead and no ears. But it was a more sympathetic protanganist than a squid or the like.

__________________
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis
Rovers forever! - ToSeek
"Carl Sagan sent a message to ET,
Neil Armstrong walked in the Sea of Tranquility
Steve Squyers built Spirit and Opportunity
Dan Haylen upchucked in zero gravity." -Brent Simon, The Space Camp Song

One of Stephen Baxter's books has a rather sympathetic protanganist who is a squid. And not an alien either -- ordinary Loligo squid, with artificially boosted intelligence.

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Fiction has to be plausible. Reality is under no such constraint.

Oh .. so you're in your human disguise.

I just remember the movie MIB II , where Serleena disguise herself as a lingerie model ....

I thought she was ugly.

Better than how she ended up later, now she's like Skeletor in a dress.

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"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
Illuminati's Razor-The most complicatedly evil answer is usually the most correct answer. - Fazor
"Every book is a children's book if the kid can read." - Mitch Hedberg
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort

Don't worry, I copied myself off a news corespondent from a 26 year old broadcast. But yes, Earth female.

__________________
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis
Rovers forever! - ToSeek
"Carl Sagan sent a message to ET,
Neil Armstrong walked in the Sea of Tranquility
Steve Squyers built Spirit and Opportunity
Dan Haylen upchucked in zero gravity." -Brent Simon, The Space Camp Song

I would have copied Christy Brinkley

This shows a theme I've noticed in a bunch of the answers here: people are talking about the other (non-humanoid) forms that life can take, but not what other forms it can take and still be "people", interacting with human characters and inventing technology and discussing philosophy. That's more restrictive than just life forms in general, and it seemed to be implied that that was the subject, both in the original post and in some of the responses. So that's what I'll be addressing here...

And a head does seem to be pretty much required. Critters that are going to develop that kind of intelligence must be critters that move around on their own instead of drifting or being stuck in place, and take in information about their surroundings and respond to it. And bilateral symmetry with cephalization has been independently developed repeatedly (chordates, arthropods, mollusks, multiple groups of worms, echinoderms' ancestor, some extinct groups) as the way to make an animal that moves around and responds to sensory information; the only kind of animal that has abandoned that form (echinoderms) is also not nearly as mobile or responsive to its environment as the ones that have retained it, which is not a suitable lifestyle for later development of science and technology. It's not just randomness or coincidence; it's form following function.

Also, given bilateral symmetry and cephalization, it makes sense for the eyes to be above the mouth because of what their jobs are and the fact that there's a solid surface below and fluid above, which is why we can recognize even insects and squid and such as having "faces" (eyes above, mouth below).

Because part of cephalization is not just gathering sensory organs and nerve clusters up front, but also putting the mouth up front and the anus in the back so stuff flows through the tract in only one direction. That's the way that it's easiest to put food in, choose which stuff to put in and which stuff not to, and drop wastes out. Again, this isn't just theory; it's already been done independently by multiple separate lineages without consulting each other.

There's nothing wrong with the esophagus going between the lungs. Your reference to choking makes me think your actual problem is with the throat, where the digestive and respiratory systems intersect. But that's not a problem with the mouth or the rest of the digestive tract; it's a problem with the lungs. The digestive system was there first. The lungs came along later, but even that arrangement was a matter of cause and effect, which makes it likely to repeat on another planet anyway when large animals start breathing air. If a species is going to start capturing air in a big open space in its body but doesn't have lungs yet, it needs to have an open space available with access to the outside, and the digestive tract is the only established part which fits the description. It's a classic case of evolution using what's there in the first place (and then modifying and specializing it some more later on).

Because the sensors come first and the nerves join into a node for the data to all be processed together instead of separately, and then when a brain develops later, it's not a separate new planned creation from nothing; it's just the node where the sensory nerves meet, grown bigger. So it's just another case of modification from what's already in place.

You seem to mean that any other number could have worked just as well. But ask yourself this: there are so many other limb arrangements, why aren't any of the others the ones that were so successful in large sizes on land? Life that wasn't bigger than a few ounces wouldn't have enough nerve cells to engage in complex thoughts, and life that was stuck in water would have no good construction/toolmaking materials available and not much available oxygen, so if we're talking about "civilized" critters that can be characters in stories like humans can, they need to be bigger than bugs and out of the water.

When you come out of the water and onto land, and then once again when you get bigger than a few ounces, you become more exposed to gravity. And, to make a long babble short, the general tendency is for the most successful groups under much exposure to gravity to have fewer legs (but bigger ones) and compact bodies that more legs couldn't really fit on anyway (unless they were so tiny they compromised mobility), while numerous smaller legs are more appropriate when gravity's not much of a factor. And if you're on land and big enough to hold much of a technology-inventing brain, then gravity is a factor even on a low-gravity planet, because you crossed that threshold when you got heavier than a bug.

More limbs would have weighed them down if they tried to fly with that burden. It's useless dead weight. And where would they attach? The torso would need to be bigger to fit more, but there's no point in having a bigger torso. You could get the wings out of the way by putting them above like the way dragons are usually drawn, but then you're acknowledging that anything over 4 legs get in each others' ways and proposing limbs mounted in a position where legs never would be because legs on top are useless, so what kind of limb were the wings derived from?

True, but they didn't build and fly spaceships, or even carry supplies over long distances on foot or throw spears or sit/lie down while working with their "hands". A vertical spine and wide platform shoulders moved out to the sides instead of in front are much better for stability, load-bearing capacity, range of arm motion, leverage, and even usability while relaxing instead of standing/moving.

What tentacles and trunks and tails don't do is hold up much weight out of the water. Solid, sturdy, jointed limbs are a necessity for the animal's primary support and mobility in that context unless you talk about snakes, but snakes don't have hands. Jointless additions like trunks are just optional after that, but not very common, and not mounted in a good position for structural support when handling large amounts of weight compared to body weight. (Elephants's trunks can pick up a much smaller fraction of their own weight than our arms can, and can't move it with as much range, speed, or precision.) This does allow for civilized aliens with jointed legs for support & mobility and tentacles or such to do the manipulating, or which move around like snakes but have tentacles near the head or tip of the tail for manipulating. But that would be the exception, not the rule; most animals have no use for specialized manipulators, so any given lineage wouldn't have them for most of its evolutionary history, so by the time manipulators did eventually become important for a species that's eventually going to technologize, it wouldn't have tentacles available to use for that because it's already been getting around on solid jointed legs for a long time.

So the most likely civilized alien life form, even if not the most likely alien life form in general without the "civilized" qualification, happens to be a bipedal, two-armed body with a head on top bearing what we would recognize as a face in the front. (And this is true even if they managed to evolve a respiratory system that wasn't derived from the digestive system.)

A head that's distince from the rest of the body? That's not how mollusks and crabs do it, and they have manipulators which could conceivably lead to technological life.

Maybe, maybe not. It takes a lot more intelligence to navigate a "drifting" balloon than a powered airplane. One of my speculations is plant-like creatures which use tidal currents to travel between "sunbathing" spots during the day and nutrient rich spots during the night. Tidal currents are regular enough to be useful but complex enough that intelligence is required to use them well.

Hold on there! There's no reason to assume these were independently developed. From what we understand about the evolution and genetics of limbs, it's actually more plausible that it was developed only once and we've just been reusing the same base code ever since then.

That's not clear at all. Starfish and brittle stars are quite mobile and responsive to their environments, and they have limbs and manipulators that could be suitable for tool manipulation.

Many squids live in the open ocean where threats can come from any direction. They have eyes to the "sides" of their bodies for full coverage.

There is in fact no a priori reason to assume alien life will commonly have solid surface below and fluid above. If alien life most commonly dwells in so-called ice giants (aka neptunes), then the overwhelming bulk of the biosphere is in a deep, deep 3d water/ammonia/mineral ocean.

Again, it looks more like this was evolved once, and creatures since then have been living with its limitations. In fact, many creatures turn this model upside-down--putting the mouth on the bottom and the anus at the top. Most crabs twist things around so the mouth is on the bottom and the eyes are up on stalks. The eyes are needed more for detecting threats and mates than for sorting through food.

Umm...book lungs. Nowhere near the digestive tract, and nothing to do with it.

Land crabs do pretty well, and can be pretty big. This is all the more remarkable because crustacean respiration of air isn't as efficient as arthropod respiration (but hey, the advantage goes the other way in the oceans and considering the biosphere sizes, the crustaceans got the better half of the deal).

The reason for the limited limb arrangements in vertibrates is because we're all descended from a common tetrapod ancestor. Four limbs, a head, and a tail is all we get to work with.

Bigger than bugs, perhaps. But arthropod style life can be HUGE with higher concentrations of oxygen and/or lower gravity and/or more efficient respiration.

Out of the water? That's not obvious at all. Life doesn't need oxygen, so that's not an obvious requirement either.

The most successful groups under much exposure to gravity are various plant groups. The most successful land animals are arthropods. If you play around with your categories enough and combine enough criteria together...then yes, you can contrive some category where tetrapods are the best.

But the success of the tetrapods hasn't even put a dent into the utter dominance of the arthropods on land. The only thing which really put the hurt on them was reduced oxygen levels. For whatever reasons, arthropods haven't been able to evolve respiration that's as efficient as tetrapods, and as a result large arthropods died out. Really, large tetrapods wouldn't have had a chance either except for our fortuitous development of efficient respiration. We've got an edge in respiratory efficiency that makes up for our lower reproduction rate in large creatures.

It seems that respiration is one of the more "difficult" things to evolve and/or improve. Entire orders of animals are pretty much stuck with what they get. That's why arthropods can't get much of a foothold in the oceans and crustaceans can't get much of a foothold on land.

Back when Earth had more oxygen, there were large flying insects. They did fine with all the extra legs.

Being able to sit/lie down while working is a dubious "advantage". It puts you in a far more vulnerable position if a predator shows up.

It's not at all obvious that dinosaurs didn't carry stuff over long distances. Their closest modern relatives, birds, carry stuff long distances to build nests. Many dinosaurs may have done the same.

It's also not obvious that they didn't throw stuff. Some birds use crude tools, and some open up clams by "throwing" them against rocks. We simply don't know enough about dinosaurs to rule out the possibility that they used crude tools.

Prehensile tails are often capable of supporting the full weight of a monkey. There's no reason tentacles and trunks and tails can't support lots of weight. Of course, in this context tails sort of "cheat". In a sense they're jointed appendages, just with lots of joints. In the same sense, a snake could be considered a jointed being.

But is it really cheating? Regardless of the fact that there's a bony spine providing support, the musculature and control is essentially similar to tentacles and trunks. The difference? The presense of tough supporting material. This support doesn't need to be in the form of large rigid bones, and it doesn't even need to be in the form of a "spine" of many segments. It can be lots of little hard bits, like in the body of a starfish or the mantle of a squid.

Mainly because we're all descended from a common tetrapod ancestor.

I don't know how much distance you mean, and I never specified, so you're not contradicting me here. A head is just one end of the front-back axis, and the heads of the critters you mentioned fit that description. (A squid's or octopus's tentacles/arms are a part of its head; they're like flexible jaws.)

...which is what makes the balloon not actually drifting. Drifting means not using your own propulsion to affect your direction or speed of travel. It takes no energy and no intelligence, and it isn't "navigating". It's what pollen does, for example. The balloon analogy is wrong.

It isn't an assumption. It's from the evidence, and it's been well established for a long time among those who know their zoology and comparative anatomy and such. The fact that separate ancestors of these separate groups developed these traits they now have in common separately isn't even a matter of any doubt, debate, or dispute. It's just how it is.

Not compared to what bilateral symmetry allows.

Not completely; their eyes are still a bit closer to the top and the distance between them is less over the top than it is under the bottom. The original condition for the whole mollusk clade is with eyes on top, which is how other mollusks still are.

No. You got at least two biological facts wrong here: the single development of something that is known to have developed independently more than once, and the crab thing because there's nothing upside-down about their heads, which are completely normal; I've heard of no crustaceans that orient themselves upside down and would be curious about examples, but it wouldn't matter anyway because the existence of secondary torsion in things like snails doesn't affect the real anatomical point here. But you also got my own statement wrong in two different ways while you were quoting it. I did not say "bottom" and "top" in reference to the ends of the digestive tract, so it's not even an issue, and crabs having their eyes above the mouth is exactly what I said is normal so you were agreeing with me on that one but presenting it as a contradiction.

They're also unsuitable to animals large enough to have anything like our brains, and thus irrelevant in the given context, which is about animals big enough to have something like our brains. (And even they were derived from something else--legs--so they'd only illustrate my point about evolution taking whatever it can get instead of being planned out, even if they were relevant!)

Compared to what? I don't know what crab is the biggest to live on land, but the biggest crab of all (Japanese spider crab) only has a 15" body (hardly more than twice the size of human brain alone) and lives on the bottom of the sea. As a group, crabs have fewer legs than other crustaceans that live exclusively in the water, and they and the few other crustaceans on land remain far less successful than arthropods with fewer legs (arachnids and insects).

Crustaceans ARE arthropods! You really shouldn't do this without a decent understanding of zoology.

That is not in dispute, so it's irrelevant and couldn't really have served any purpose but attempted distraction. The issue isn't why we have how many we have; it's why animals with the different numbers they have are found where they are and not found where they aren't. And success under exposure to gravity is pretty clearly inversely related to limb count.

I didn't present them as requirements for life. That's another irrelevancy that couldn't have been anything but a distraction attempt. We're not talking about just "life". We're talking about a specific category of life: the ones that could develop civilization and technology. It's much narrower.

That's the whole point; we're already talking about such a category because that's the subject. Any other kind of life is not the subject. It's not a matter of me sneakily trying to manipulate the outcome by fiddling around with anything; it's just what the subject is here! Bringing up anything else is just trying to drag us OFF of the subject.

Crustaceans are arthropods. And if you meant insects and arachnids, then where do you think they came from? And why do you think their number of legs got so reduced, or why do you think the groups that already had the low leg counts ended up so dominant on land and so absent from water?

Not at all. It allows you to get more work done by making use of your resting time.

That might be relevant, if we were talking about whether or not animals should ever rest at all, which we aren't.

In tiny amounts, because weight is the enemy of flight, which makes birds irrelevant here because flying is not one of the parameters we're talking about. With the dinosaurs, the problem with carrying was still weight (along with lack of opposable digits), but for a different reason: the arms were forward of the feet instead of straight above them, so an increase in the load would have moved the center of gravity and thrown the animal off balance. That's why they had such short arms and lightly-built heads; they needed to save weight in the front in order to remain balanced on their feet... not that it matters anyway, because even if dinosaurs had developed technology, it wouldn't go against my point that a biped with two arms and a head on top is the most likely form of a civilized alien...

As I said, the position and orientation of their arms is all wrong for it, as is the arms' very limited range of movement. It's basic anatomical dynamics. Watch someone trying to throw something heavy far and fast, like a javelin, football, baseball, or Olympic discus, and you'll see that there's just no way for a dinosaur to move like that... not that it matters anyway, because even if dinosaurs had developed technology, it wouldn't go against my point that a biped with two arms and a head on top is the most likely form of a civilized alien...

Hanging from a tree is nothing like standing up on the ground, in terms of physical requirements. Hanging can be done with a pliable support like a rope; standing up requires a rigid one.

In the anthroplogy corps, you are taught not to copy any individual who appears in signals exceeding 79 p'ilk. In other words, nobody famous, or you will be mobbed and research will be difficult.

__________________
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis
Rovers forever! - ToSeek
"Carl Sagan sent a message to ET,
Neil Armstrong walked in the Sea of Tranquility
Steve Squyers built Spirit and Opportunity
Dan Haylen upchucked in zero gravity." -Brent Simon, The Space Camp Song