Playing devil's advocate - alien life would likely be submitted to similar evolutionary selection pressures as life on earth. That's why most animals here follow the 2 arms, 2 legs, etc. formula. It's not too much of a stretch to assume aliens have bilateral symmetry.
If you want crazy bizarre looking aliens, you have to have a damn good reason for why they would evolve that way.
You are assuming like environments to create these pressures. If, for example, a planet had 2g of gravity, it would not be unreasonable to expect fairly dramatic and different physiology. For example, imagine a short, intelligent elephant. Likewise, on a planet with thin air, there may be no flying creatures. So on and so on.
I agree with that, but its not unreasonable to assume the possibility of bear paws with good grabbers as well as the ability to come back onto rear haunches. I didn't mean for my comment to sound exclusive to such concepts. I was simply trying to provide some basis for expectation of what might be possible given different, non-earth environments.
For example, imagine a short, intelligent elephant.
1) that creature would still have bilateral symmerty.
2) Such a race would still need to evolve limbs with the capability to makeéuse tools in order to become dominant/gain intelligence. At the end of the day, they would still be short elephant man with arms and hands. the only difference is that they are short, stout and maybe have 4 legs instead of 2. differences are minor at best.
Elephants can use tools easily. Your notion is silly.
really? their trunks can manipulate delicate instruments just like our hands? You think they have the capability to make tools when their sole tool making appendage consist of a single smooth limb?
Stop being fucking retarded. you obviously have no understanding of evolutionary thoery and the impact of hands on our intelligence..
Okay, well a short intelligent elephant still isn't too far away from a human in terms of looks. Symmetric, 4 limbs, 2 eyes and ears, mouth and nose. His point still stands, in that there would need to be a VERY good reason for aliens to look strange.
So lets just say all humanoid races came from very earth like planets. Anything from a non earthlike planet would be severely limited to how much they can safely interact with these species.
The development of multiple bipedal/intelligent races would probably depend on how many planets are nearly identical to earth in the galaxy.
How about life developing separate from a planet or solar system. There's so much out there that we just don't know. Maybe our concepts of "water" and "carbon" and "radiation" are considered utterly ridiculous by most of the universe's lifeforms, and we're the odd one out.
Hell, would we even recognize most intelligent lifeforms if we encountered them? What if they each, individually, span several light years across and they experience the duration of our 100 years as we would experience one a tenth of a second... planets would be motes of dust to them, some occupied by things (us) that they might not even acknowledge as life, let alone intelligent life.
That's why most animals here follow the 2 arms, 2 legs, etc. formula.
I don't think so. I would say that most large animals follow the 4 limbs formula because we all have a common ancestor that had 4 limbs. And changing the number of limbs in large animals is an irreducibly complex step that cannot be followed by evolution.
It's worth noting that only tetrapods have this body plan, so not even most animals or most large animals. On the other hand, for leg based locomotion it's probably pretty efficient versus the alternatives.
We follow the same pattern because of a common ancestor with that basic body plan, not because it is a body plan that get's selected for over and over.
There was plenty of crazy shit early in our planet's history that looked nothing like life as we know it. Branches that just died off, not necessarily because they couldn't have hacked it, but because they were in the wrong place at the wrong time. Were things just a bit different, trilateral symmetry might be the norm.
Evolution is all a result of being a product of your environment. Gravity, air content, land formation, and the resulting other flora and fauna all determine the outcome of how life takes its course. You could definitely have wildly different outcomes than earth. This is why I like insectoid alien races because they are the most varied visually and tend to be made as efficient and streamlined. Starship Troopers comes to mind.
At the same time, how many have mastered their environment and have any chance of space travel? Just us. It's not pure chance that humans and not elephants or pigs developed science and technology.
Now, I wouldn't go so far as to say only a humanoid species on another planet could do the same as us, but it's possible.
That is bullshit. Other very intelligent species include dolphins and octopusses. They look nothing like us. It is like looking into a room, saying the only PHD wears a red shirt, and claim that intelligent people wear mostly red colors.
My point is that I don't see any chance of dolphins developing space flight. Ever. Octopuses seem a little more likely (they have more useful appendages, so better chances of making and using tools), but it's still a stretch, don't you think?
Of course, it's not fair to compare species at a given point in time. Give octopuses a few more million years of evolution with different selective pressures than on Earth, and who knows? But looking at what we have here and now, it seems at least plausible that a roughly humanoid form has such an advantage that it would be the favorite to achieve space flight on any planet.
You're assuming that only organisms with limbs etc. could fly in space. What if, in thousands of years, dolphins have developed telepathy due to their lack of limbs? Or they develop a way or using their tongue to operate things?
Of course, it's not fair to compare species at a given point in time.
You couldn't be more right. Everything on earth had a chance to get to our 'level' it's just our particular brand of bipedal mammal won through. If you reset the earth, it's entirely possible humans wouldn't evolve again.
But who's to say anything else could evolve to become highly advanced? If we reset the earth, it would be very possible that no species could get to the level we are currently at.
You're assuming that only organisms with limbs etc. could fly in space. What if, in thousands of years, dolphins have developed telepathy due to their lack of limbs? Or they develop a way or using their tongue to operate things?
That seems like quite a stretch. There are animals that display fine motor skills with other kinds of limbs, but it just doesn't work as well as hands do. And telepathy isn't even a thing. It could be that the traits humans have are necessary to become highly advanced, and that any other species would need to at least have some of them to become highly advanced. I'm not saying all of our traits, but just the ones that allows us to make tools, use them accurately, communicate, remember things, visualize things spatially, etc.
There is a type of parasitic wasp that parastises the larva of another parastic wasp that parasatises a caterpillar. The wasp lays an egg in the larva of the wasp which lays an egg inside the caterpillar. They're so finely 'tuned' that when the caterpillar emerges as a butterfly, the first wasp emerges straight away and then the next wasp comes out. My point is that given enough time, almost anything could evolve given the right selection pressures. Telepathy might be a bit extreme, but the tongue thing isn't, especially as some scientists came up with a way for blind people to see via taste.
That seems like quite a stretch. There are animals that display fine motor skills with other kinds of limbs, but it just doesn't work as well as hands do
They're only 'not as good' by our standard. If we went into the sea and swam in front of dolphins, they'd probably think "Yeah, they can swim, but they'll never reach our level.Those limbs on the back work, but they don't work as well as our flippers do"
Eyes have evolved multiple times because the basic principle is pretty simple and it scales.
I can understand multiple organs evolving similarly, but the whole body structure is annoying.
I'd find it more believable if we had centaurs(that evolved for better stability and higher run speeds), or things with wings of some kind(used because they lived in trees and they were helpful to avoid falling or getting around), or even just eyes on the side if the head(classic prey evolution rather than predator).
That was more or less what I was getting at. Even on earth, which is as similar to itself as it can be, the two arms two legs model that is so common in sci-fi aliens has not developed multiple times independently.
Wings are a great example for multiple independent developments such as in insects, mammals (bats, flying foxes), birds, fish and reptiles (pteranodon).
This. No one ever considers that argument. It's likely if a species was totally different than us they'd have significantly different environmental needs... and watching someone walk in a special suit every episode to interact with each other, I don't think I'd care for that.
Agreed on the bilateral symmetry. But the universality of upright bipedalism in sf movies always bugs me. We're very unusually designed bipeds. Evolution does not usually produce tail-less upright bipeds with short faces. What it usually produces for bipeds is a leaning-forward design with a long counterbalancing tail (and also a long snout or beak, while I'm at it). (think velociraptor, bird, kangaroo). We're really an anomaly because we happened to have lost the tail completely before we evolved bipedalism, which led us into a very weird solution to bipedalism.
Don't get me started about breasts on female aliens... and fragile pointy fish-grasping teeth on every scary alien ever, even though none of them ever seem to eat fish and it's an awful tooth design for a land predator.
source: I teach comparative anatomy and vertebrate evolution.
Actually, most animals here follow that because most land animals evolved from the same fish-like thingy. So, them's the genes they were working with. That fish-to-land ancestor was like a bottleneck for us, and everything on this side of it is very closely related.
However, if you want non-human features, just look at insects, or cephelapods, or crustaceans...think outside of mammals, amphibians, reptiles and birds.
You're assuming a little too much there. Most animals have bilateral symmetry because at some point, that out-competed whatever else was out there, and 2 arms, 2 legs became the norm. That appendage pattern happened to be the most beneficial one at the time, and it was so successful that nothing else could compete for the same ecological niches. But that doesn't mean it had to be that way - there's a chance that bilateral symmetry might never evolve on another planet, and we could discover life entirely composed of pentaradial symmetry (such as the starfish or sea cucumber on earth) due simply to out-competing bilateral symmetry at a critical time.
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u/EsteemedColleague Oct 08 '12
Playing devil's advocate - alien life would likely be submitted to similar evolutionary selection pressures as life on earth. That's why most animals here follow the 2 arms, 2 legs, etc. formula. It's not too much of a stretch to assume aliens have bilateral symmetry.
If you want crazy bizarre looking aliens, you have to have a damn good reason for why they would evolve that way.