For any intelligent species there are certain evolutionary necessities in order to develop technology. For example in order to be dextrous enough to use the tools needed to develop technology opposable digits for grasping at a distance from the fulcrum for dexterity are hugely beneficial such as the human hand and arm. That is not to say that the hand must have 4 fingers and a thumb and there must be 2 arms. As someone mentioned earlier having 4 "arms" would work just as well or having 6 fingers and 2 thumbs that work independently could be an improvement as you could operate 2 devices with one hand allowing you to be more efficient. While studies have demonstrated the cognitive abilities of birds the difficulty from a technological development is being able to use those tools with the precision required. There are certain evolutionary limitations when it comes to size also. The idea of an insectiod species is compelling but the physical limitations would make it unlikely for the species to grow much bigger than insects on earth. The exoskeleton would have to be so thick that the weight would prevent the creature from being able to move. As far as intelligence is concerned its not the size of the brain pre se but more the size of the brain relative to the rest of the body and how much energy is diverted to brain function. I agree that small animals are just as likely to be intelligent as large ones. The problem then arises with interstellar travel. Small creatures like a rodent would develop small interstellar craft with small propulsion systems which would produce much less thrust making interstellar travel much more difficult than it is for us so there would have to be a minimum size they would have to be. I guess what I'm getting at is that any creature capable of interstellar travel would necessarily have a number of similarities to humans. They would be of a similar size with longish limbs and opposable digits and would have to walk upright in order to be able to efficiently use the tools required to develop technology (you can't stand and use tools with the same limb). They would have quite large brains relative to their size and have some form of complex communication in order to develop the social structures required to effectively develop and use the technology. But all this doesn't mean they have to have two arms two legs and a head. They might have 4 arms and 4 legs. Their brain might be located in the midriff behind a ribcage for protection and they might communicate using high frequency sound that humans can't hear similar to whales or dolphins. The other alternative is to forget tying to make them realistic and just go nuts!!
I seem to recall (no cite) that this isn't thought to be possible. Supposedly, the eyes need to be located very close to the brain to minimize reaction time to (dangerous) visual stimuli. If you have the brain in the trunk, the eyes don't have enough mobility to look around, and if they're on stalks, the extra distance increases the reaction time to the point where the critter ends up screwed. I suppose you could work around it spider-style, but I'm sure there are reasons why none of the "higher" animals have >2 or compound eyes. But yeah, do go nuts, rubber foreheads are boring.
who says their eyes arent in their midrif too ( may be a single eye where humans have a belly button ) Incidentally the reason higher animals don't have compound eyes is that compound eyes have a limited range and difficulty in shifting focus quickly, so they don't suit our evolved niche (also compound eyes in insects evolved after our evolutionary paths diverged that said theres no reason why a space alien can't have compound eyes that do shift focus and have great range because , hand waves, plausible science stuff
Eyes evolved to be near the mouth so that we could see what we were eating, it's likely that all life in the galaxy that can see will have evolved the same way. The mouth can not be in the middle because of our biletaral body plan. We have two ends, sensory organs will always move to one side because it's easier to move in one direction. 600 million years ago, protoanimals were fractal based, symmetry allowed our first sessile creatures to move. Fun fact: compound eyes and our eyes are convergent evolution, they did not evolve apart from a common ancestor. Eyes have evolved separately about a dozen times. They've all been located close to the mouth and the brain developed close to that. The fact the feature has evolved so many times the exact same way provides a better sample size than with other features.
theres no reason that alien evolution has to be the same, because the environment in which they evolve is different, and evolution is adaptive to environmental factors so for example an alien evolving in low G would have lower bone mass , one evolved to low light environments would have a lot of roddcells in the eye and hardly any cones, one evolved to an evironment with a lot of windblown debris might have a nictating membrane to clean its eyes and so forth
Who said they need to have eyes. They could have a different sensory organ - sonar or radar. There are multiple ways of picking up electromagnetic signals and having eyes is not a necessity for this. Maybe they are sensitive to x-rays and this is how they "see"
Do you have bats in your belfry? Everyone knows aliens have really big eyes, really big, and they are either gray or green - those are the Irish ones of course.
I would still call those sensor organs "eyes." x-ray vision wold also not be likely, for one, stars don't really give off my x-ray. They create a ton of it in the core, but it gets absorbed quickly. It's also very damaging for molecular bonds.
Tell that to Helen Keller. Would you allow a symbiotic creature that acts as eyes for the host? Look ma, no eyes - but I've got these really nice spiders clamped on my face!
