What would aliens look like?

[the tree]

I was recently having a discussion with my friends about what the dominant species on another planet would look like. Not being biologists, we didn't have much to go on but here is some of what we figured:

 

They'd be mamals or reptiles, or at least not insects

• If you scale up a spider to the size of a big dog, the pneumatic legs (I think that's what they are) just wouldn't hold it up.
  
• Insects don't live nearly as long as mamals and reptiles it'd be harder for them to develop language, let alone learning specific skills.
  
• It's easier to move in air, so assuming land is avaliable: fish aren't too likely.
  

They be either bipeds or quadropeds, and they'd have arms

• An odd number of limbs would be silly.
  
• Assuming it has muscular legs (see above), more than four would be wasteful.
  
• Free limbs, with hands on would be needed to manipluate the enviroment and get an advantage over pretty much every other species.
  

They'd have heads that poke out of the top like ours

• It'd make sense for eyes and ears to be on top so as to get the most use out of them.
  
• The brain would be quite near the eyes, because optic nerves are big and could be vunerable.
  
• The brain should probably be away from the rest of the body so that it doesn't overheat, then again it needs to be protected.
  

They'd have skin but there's no way of guessing what it'd be like

• Every animal on the planet seems to have some type of coating
  
• Every species has something really different depending on it's specific enviroment, so you'd have to actualy know about the enviroment to say.
  

Of course this is terribly generalised and really unscientific. It's really just speculating.

 

Please contribute your own ideas.

[rakuenso]

oy another one of those other life form topics..

 

All of your hypotheses are based on the assumption that they follow the central dogma of molecular biology. What you are describing is what we would look like had these aliens originated from Earth. Why do I say this? Because your classifications of speciation and development corresponds with the homeoboxes that already strongly control development of organs.

 

They really wouldn't be aliens in your case they would more or less be migrators from the planet earth.

[the tree]

All of your hypotheses are based on the assumption that they follow the central dogma of molecular biology.

Well assuming that an alien is a life form from another enviroment, then yes of course.

What you are describing is what we would look like had these aliens originated from Earth. Why do I say this? Because your classifications of speciation and development corresponds with the homeoboxes that already strongly control development of organs.

Not really' date=' I was more assuming that they had evolved on a planted that is pretty similar to earth. Wouldn't life naturaly wind up fitting into the "specifications" that life fits into here as those seem to work?

They really wouldn't be aliens in your case they would more or less be migrators from the planet earth.

The decendants of an emigrant are still aliens but I don't see where your getting this assumption from.

[Mokele]

They'd be mamals or reptiles, or at least not insects

 

Well, first and foremost, no alien would fit within earth taxonomy. They might be vaguely reptile-like or mammal-like or whatever, but they wouldn't truly be any of those groups.

 

It's easier to move in air, so assuming land is avaliable: fish aren't too likely.

 

Wrong, actually. While there is less drag in air, that's only really a factor for animals that fly. Even fast-moving runners like cheetahs are much more limited by pace and muscle contraction speed than drag. Plus, water supports animals, so they don't have to waste energy holding themselves up. It's also easier to generate thrust by pushing against water than against air.

 

In fact, I seem to recall that the net cost of transport (calories consumed per unit distance covered) for swimming is less than for walking.

 

An odd number of limbs would be silly.

 

Note that echnioderms (starfish, crinoids, urchins, etc) were a dominant phyllum back in the Ordivician.

 

Assuming it has muscular legs (see above), more than four would be wasteful.

 

Incects seem to be doing well. Just because it's that way on earth does not mean it *must* be that way.

 

Also, what do you consider a monkey's prehensile tail? To me, that's a post-hoc modification of an existing structure into a 5th limb.

 

Not really, I was more assuming that they had evolved on a planted that is pretty similar to earth. Wouldn't life naturaly wind up fitting into the "specifications" that life fits into here as those seem to work?

 

Nope. A lot of evolution is randomness. There's no solid physiological or evolutionary reason that, for instance, vertebrates could not have evolved with six limbs. Or more. It's just coincidence that it happened the way it did.

 

Mokele

[Paramecium]

Well, this is simple how they look like, cause if you assume that dinosaurs evolved to the intelligent "humanoid froms" and then leave our planet, and now they are coming back (as UFO) so we can see them and according to the descriptions (from witnesses) these aliens really look like humanoid dinosaurs (green men).

[Firedragon52]

I bet they would be reptiles. Hell, Reptiles used to rule this planet once already.

[Firedragon52]

 

They be either bipeds or quadropeds' date=' and they'd have arms[/b']

 

 

 

• An odd number of limbs would be silly.
  

Oh yeah!

 

...obviously someone hasn't read/seen War of the Worlds

[cool_b74]

hello to everybody,

why do you think that aliens have to be like us .they are not like us . they are far more superior than us .they are in a form that humans cannot imagine in their wildest dreams . whichever serial . programmes people make for the television that has stories concerned with space and other civilizations , what happens - another civilization is going to attack our civilization on this earth when u see the people from the other civilization in the film what u see is they are like us , eyes , nose , mouth and ear at the same place like humans or it will be like some creature on the earth but it can talk . everything will be different , form of communication will be different, mode of transport will be different, they may be a form of life for whom gravity may not mean anything. whenever we think of aliens (a life-form that we have not seen , just thinking could be somewhere there in the outerspace ) we think based on earthly context. there are many things to be discussed . i want to know how you respond to my reply.

[Paramecium]

There may be pretty much life forms in the universe and not every must be necesseralli inteligentous. If we go to the molecular level they can be construct from other elements than me, the body have not be made from many cells, the basic macromolecules have not be DNA, lipids, sugars, proteins. I think these are basic questions for biologists, if thay want identify foreign life forms, the external appaerance is only result and it is not so crucial.

[rakuenso]

Not really, I was more assuming that they had evolved on a planted that is pretty similar to earth. Wouldn't life naturaly wind up fitting into the "specifications" that life fits into here as those seem to work?

 

Because the odds of evolving a similar homeobox out of random mutations that is so structurally organized and preserved is almost nil.

 

The decendants of an emigrant are still aliens but I don't see where your getting this assumption from.

 

Lets put it this way:

 

If they have limbs or organs, then they need to have homeoboxes

If they have homeoboxes they are derived from earth species

If they are from earth then they are not aliens rather than migrators

 

Thats like saying if I went to the moon, started a colony, and my descendents came back 10000 years later, would I still be an alien even though there would be clear simiarities within our genomes?