What do you guys think extraterrestrial life might look like? Rather than just spinning your imagination, try thinking about actual conditions which might exist on another planet and how that might shape an alien organism. Include this thought process in your description and attempt to justify your speculation with sound biology to the best of your ability.

Well, first off, it all depends on the environment. They wouldn't need to be humanoid, that's just a nice delusion, but they would need some way of manipulating their surroundings. It really all depends on the species from which they evolved.

I suggest that someone thinks up the planet, and we can speculate on what life would look like on it given its temperature, atmosphere, geography, etc.

Well i think that extraterrestrial life would be so radically different from that on earth, that if we were to see it we wouldn't recognise it as a creature. I think this because we are used to seeing the kind of things that evolved to survive on earth, however on a different planet life would have to evolve to cope with totally different conditions.

I also think it could be a good idea to do a brainstorm with Metal Meltdown's idea, think of a planet and it's conditions, then build up lifeforms from that.

I don't understand your proposal, Metal: if life happened again on earth, it would happen as it has happened, right?
Edit: Metal edited his post - it previously proposed imagining how life would turn out if it happened on earth, or something like that.

I was going to post this in OP but decided not to, mostly so it wouldn't hold unfair weight. Now that someone else has posted, however, I might as well.
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I think that extraterrestrial life will not be as exotic as some people think. Although we can imagine silicone-based life and sentient clouds of energy, the fact that life on earth emerged only a billion years after the planet formed makes life as we know it seem statistically a very probably occurrence. That is to say, ETs would probably be carbon based and mostly water, just like us. Other than that there might be a whole world of differences (literally), but the basic building blocks would be familiar. Since life most likely can't form on dry land, I think it might also be hypothesized that alien life will consume oxygen in some form. It is unlikely that life could evolve and inhabit a body of liquid which is as largely comprised of an element as reactive and useful as oxygen for long without developing the ability to use it.

As far as appearance goes, I remember Neil Degrasse once stating that we should not assume that intelligent life forms will have faces, mostly based off the fact that most organisms here on earth don't have faces. I disagree. If something's intelligent, it's going to be mobile. Intelligence is only useful if you can use it to adjust your behavior; if you can't move, you don't have behavior to adjust. So intelligent alien life would have to have the ability to move at a speed visible to the naked eye (no at the speed at which leaves rotate, for example). If they're moving, we can also probably assume that they're eating. This is because A) photosynthesis is generally believed to be way too weak to power a moving organism and B) if they didn't have to find their own food, it's hard to imagine why they would need to develop intelligence. One might make the claim that intelligence could develop as means of defense from predators, but this just doesn't seem that likely. So they need to move and eat - but how do they know where to move and what to eat? They must have some sort of sense: smell, sight, sonar, whatever, they just need at least one way of perceiving the world around them. So we have a direction the organism is going, conceivably some sort of hole into which food goes, and a few doodads for sensing its surroundings. What's the best location for all these things? I don't know what the rest of this creature looks like, but clearly all of these features need to be in the same place. Sensing is important to knowing where to go, of course, so the best place to put an ear or eye or whisker is of course in the front, or the direction the organism is moving in. It's also important for eating, for obvious reasons, so the mouth-hole should be around the same area. So we have a hole and some sensing thingies - what does that give us? A face! Kinda.

I think there was one proto-species that developed well before all others and went around seeding planets with bits of their DNA so that we'll all look somewhat similar to them

star trek

I think the most-fun way of thinking up an alien is taking anything on earth and making it the dominant species.

So let's say... Redwoods suddenly become the top of the food chain. They can lift roots up and move around, they can stomp on other creatures, and the great firestorm of 2012 was ineffective. Trees need a way of detecting opponents (2+ eyes for depth perception) but can obtain all it's energy from photosynthesis, so no need for organs and such.

Now let's say they build some spaceships and flew around

whee

It's a very clever way of saving a shit-ton on costume design, that's for sure.

Stargate SG1 pulled of a similar plot device which explained not only why everyone from other planets look just like us, but also why they speak languages which a young, handsome archeologist can understand.

Talking of Xenobiology:
http://www.waynebarlowe.com/expedition_pages/index_expedition.htm


I think there is an actual theory for this, i forget but i think it's called the "Mother Theory" or something. It suggests that all life is similar because of DNA spreading to other planets on 'seeds'.

Tl:dr version: life somewhere else would be very similar to that on earth.
I for one disagree. We assume that only developments such as those we see here could ever exist. But there are other ways of eating (see plants), other ways of hearing (sensing the vibrations in the ground, maybe?), other ways of seeing (echolocation, for one), other ways of smelling (well, at least that's what I think snakes are doing with their tongues, I can't remember for sure right now). Sharks can sense electrical impulses through organs in their snouts. And before someone points out that what I did there is self-contradicting, I'm just pointing out that there are utterly alien means of doing things on our very planet, let alone out in space.

There are some basic biology points that will apply to any species.

- To have depth perception you need at least 2 visual inputs (they can be of any spectrum - thermal imaging for dark planets/caves, vibration sensors like we have in our blind fish, magnetic sensors like in birds, or even just really good ears like bats). Any more than 2 adds clarity but at huge cost, so it's gotta be damn worth it. let's call this a spatial relationship organ (not to be confused with communication)
- Feeling the vibration of a bass speaker in your bones is the must fundamental form of hearing (and is why deaf people can dance at concerts). The only environment that would produce alien life without sensory organs for vibration (aka sound) is that of a vacuum, or where (unlikely) so much vibration occurs naturally that it drowns out the natural sensations.
- I don't believe in telepathy, but I do believe that communication is a requisite for an advancing society. Visual communication is incredibly limiting and audible communication is incredibly cheap (biologically/evolutionarily speaking). We can assume that most lifeform will communicate audibly (the pitch/range of the comms can and will adjust depending on atmospheric density)
- Audible output, if applicable (see above) requires physical vibration. Cheapest method is non-damaging bellows system (like us) but can also be bone vibration (crickets). Since directing audiowaves is incredibly difficult, even with an array of "speakers", more than one is evolutionarily expensive and unlikely.
- Most suns push out radiation in the form of photons in a certain band range - our eyes are adjusted to see well in our daylight conditions, but our daylight conditions are fairly "normal". Sure some aliens may grow up seeing XRays and MicroWaves, but it is biologically inefficient to specialize in such a way unless your sun is built like that.
- Being unilateral makes you walk in circles or restricts your motion to certain planes. Bilateralism allows you to traverse easily and freely in most directions. The more legs you add, the more inefficient the design becomes - but you gain some sort of advantage (quadrupeds have better speed; more legs means more friction means walking on walls). This applies to avians (no solid ground on a planet) and aquatics (viscous material traversion) so I'm not limiting my scope to "walking".
- Any species that is excellent at utilizing tools is going to have an extra set of "legs" (insofar as humans are quadropeds) thus decreasing their efficiency further
- Birds can faintly visualize magnetic fields for navigation, but body-orientation is a requirement for any advanced species (so they don't just keep falling over). An internal organ that can sense upright-ed-ness is going to be a gyroscopic sensor of some sort, similar to the inner ear. Fully conceivable that the stomach might double up for something like this. Applies to any species where gravity is a function.
- Gravity is the biggest factor in skeletal types, but it scales up. If there is a planet with half gravity, insects can easily grow twice as big with exoskeletons, but likewise internal skeletons like our own can also get twice as big. Exoskeleton's strength-to-weight ratio starts getting screwy at larger sizes, and it is fully conceivable that any population of exoskeleton-bearing creatures can be an excellent food source for a larger, internal-skeleton species... unless the exoskeleton also protects against atmospherics as a prerequisite for existance.
- Digestive tract and respiration can be extremely exotic depending on the atmosphere and available food sources. I won't even guess at these.
- But everything needs fresh chemicals and such to various parts of the body, so there will be a "pump" of some sort. Our primitive microbes use temperature differences to diffuse liquids around the body, but it is a guarantee that every creature will have a 'heart' of some sort (metaphorically or literally)
- Close-range extra-sensory devices are usually biologically cheap and practical (smells alert us to poisons, etc.) but not exactly required. Sharks electrical-field sensing fits here too (extremely short range and only useful in water). Humans also have really sensitive thermal sensors - it's how you know someone is just about to touch you even when blindfolded.
- Electrical-field communication (telepathy?) and sensing requires exponential sensitivity on both input and output vs. range, which means it's incredibly expensive and probably won't occur much.

Therefore it is a safe bet (but not guaranteed) that alien life (that can achieve space travel):

- Is bilateral (biologically cheap and effective way to produce the following)
- Is bipedal (two tool utilizers, two legs)
- two spacial relationship inputs (eyesight/sonar mapping/etc)
- two communication inputs (can be bone-vibration-sensors like a dolphin skull, doesn't have to be ears)
- one communication output (depends on atmosphere)
- has gyroscopic stabilization
- will have cardiovascular system
- odds are in favour of internal skeleton but there is a non-insignificant chance of exoskeletal.
- may or may not have a super fine close-range sensory organ

Using those guidelines, go nuts with your imaginations! Replace carbon with silicon and all the above can remain true.

Any "advanced" life (cloud of synapses floating around? energy-based?) will be an evolved form of life FROM a species as described above; I don't believe it's possible to coalesce in and of itself.

Other things may be sentient (plants, puddles, energy based life) but aren't very useful when it comes to handling tools.

Star Trek is littered with examples of collectively cohesive species -- even Borg counts, though artificial. You know, those planet-spanning puddles or crystalline structures? I think it'd be really interesting for a city-sized puddle of microbes all getting together and building a spaceship or something. That's neat to think about, but is evolutionarily unlikely - any creature in such quantity is bound to produce a predator that'll thrive on it.

I think you missed what I was trying to get at. When I said that alien life would be similar to earth life, I only meant in very basic ways: carbon based, mostly water, oxygen loving, and with a face. I never said ETs would see and hear and smell as we do - in fact I'm pretty sure I explicitely said that it doesn't matter how they sense for the point I was trying to make. All I was claiming was that however they understand the world, the organs with which they do so will be in the front, along with some sort of mouth, to create something face-looking. You mentioned that there are other ways of "eating" and mentioned plants. You're wrong, actually: plants don't eat. They're autotrophs, and it's pretty widely accepted that autotrophs of signifigant size aren't mobile.


To Weasel, good points, but I disagree a bit on a few things.

First of all, you should have specified from the beginning that you were talking about intelligent life specifically - that thew me off quite a lot.

Although audible communication is a pretty straightforward thing, to take an approach from you, if we imagined the humbolt squid evolving high intelligence in a setting which selected for the ability to communicate better, I don't think they would take this route. Rather, they would refine the method of communication which they already use, which involves flashing patterns of bright colors along their bodies. This is already considered a relatively complex form of communications and I don't think it's unreasonable to speculate that it could be on par with talking if they evolved better "skin resolution".

On sight - why not sonar?

When you say that respiration is exotic, do you mean what an organism breathes, or how?

In your final list you claim that said alien will have two legs and two tool utilizers. Did you mean to say "at least", or are you sticking with that? Even then, an organism could have one water jet and two arms for tools/manuevering. Also possible is just two hands to walk around on - the alien can just sit on its ass if it needed to use a tool.

If anything, I think the Creatures will be somewhat similar to Alien Planet which is a excellent program by the way. And if you cant find a bit of the program click the following linkl. http://www.youtube.com/watch?v=_ZeYYyotOTk It is a interesting program about alien life.

I've heard of that, and it looks interesting, The link in my earlier post was the original artists website.

Anyway, most of the creatures on Darwin IV use Echolocation and Sonar, but there used to be creatures with eyes. I don't know why they lost them, it looks like there's a lot of visible light.

Man, I loved that thing. There was also another one with a similar setting, just without the two man-made drones. And it takes place on a different planet in each episode. Can't remember for the life of me what it was called, though.

Could it be Snaiad? Because holy crap it looks awesome, there's pictures of their anatomy and everything!

Feel free to share, please.