Possible Alien Life

[Boerseun]

I've watched a couple of "Alien"-type movies recently, and it occurred to me how the popular image of an alien has dictated how we envision aliens to look like.

So, I was thinking that using our common sense we could hypothesise about what they would actually look like, ignoring everything Hollywood came up with (mostly because Tormod said we need something new and fun to talk about! )

So - firstly, I should state what I believe:

1) We have incredibly weird animals and plants on this planet.
2) Animals and plants evolve to fill niches. The specific demands of these niches dictate what the animal/plant would look like.
3) I think life would come up with roughly similar solutions for similar problems on similar planets.
4) I think that given two possible solutions for a specific problem, life would tend to go with the least complex, most energy-efficient solution.

So - I'm sure there's a lot more to add to the above, but let's begin:

[Boerseun]

To begin with, I'd say two eyes is probably the norm. It's the simplest and easiest way to achieve stereoscopic vision. To illustrate, just think of all the unrelated animals (insects, reptiles, mammals etc.) who've adopted this solution.

I'd also say that a head is a fairly common feature, with the eyes attached to the mobile head so that the animal can see around itself without actually having to turn the body. And the brain should be close to the eyes to speed up reflexes. As is the solution on Earth!

It seems as if we're a pretty common lot on Earth!

Any more ideas?

[pie]

It's a good bet that if there were any advanced civilizations in our universe, they would have had to evolve in a similar way as we are doing.

I suspect that there may be oceans on these life Bering planets with sharks in the oceans, and Jurassic forms of life. - One reason is that the sharks we have on planet earth are very efficient on body design. - Once a species adapts to its environment, evolution stops.

In the case of the sharks, these animals stopped evolving before the dinosaurs walked on the earth.

So, it may be a good guess that if there were advance civilizations in our universe, there home planets would have oceans with sharks that look similar to ours. - Beyond that, life must take a similar path as on earth.

I often thought that advanced civilizations might be more like a "star wars" space bar where all sorts of animals evolved into higher thinking beings.

[Boerseun]

Sure - but I'm talking more about life in general.

There's a couple of evolutionary dead-ends found on Earth, that might have been taken further on an alien planet because the environment would demand it. I think one thing that would definitely be inevitable would be the 'predator/prey' type scenario, like we see in the jungles on Earth. The reason for this, of course, is that an animal (say, a grazer) is a handy concentration of available energy for any other animal that woul want to become a carnivore.
So, in that respect, it seems as if Earth also took a relatively common or inevitable approach!

[HydrogenBond]

The evolution of the life on earth was influenced by the environment, which was changing and evolving over time. Alien life would probably contain DNA since the laws of physics and chemistry should be the same everywhere. But a different environ and different changing environ would change the natural selection process. If the sun of the alien world was always much hotter and the oxygen and ozone always lower, the humanoids at the top of this alien evolutionary chain may have tough skin like a reptile. Being cold blooded may also be better to keep the body cool during the hot days. They may be better able to conserve water and have learn to hybernate during the hottest months of the year, etc., . The keyboards on their laptops may also be metallic due to their spiney claws.

[UncleAl]

1) Oxidative metabolism with pumped gas flow. If you want to kick butt you need the power output. Gills, lungs on the outside, are fragile plumbing. Water does not carry enough oxygen/volume.

2) Endoskeleton. Exoskeletons (insects, arachnids) don't host much intelligence and don't allow much size. Absence of skeletons (octopus) host good intelligence but requires a dense support medium. No fire, folks, and no technology therefrom.

3) Sensory cluster up front and forward. It doesn't do you much good to know you are going to die after it happens. At least one near-field high spatial resolution sense and one far-field distance sense. It's gonna have eyes, sound, and chemical sensors. Stereolocation is important to survival. Some of the sensors will be at least paired.

4) Coarse and fine manipulation of the near-field environment. Something manipulable sticks out the center or on both sides, and it terminates in specialized anatomy. Ya gotta get a grip if you wish to evolve intelligence.

5) Symmetry. Evolution may diddle with that, but considerations of balance during locomotion argue for it overall. Ya gotta flee and pursue if you hope to survive as a species.

6) Accomodations for local gravity and lifestyle therein.

7) Odd chemistries? I think not. We are star tar. Life will pretty much run like stuff we have here. Fine points of metabolism will be altered.

Intelligent alien life will not look especially alien compared to the variety of local products. Customization may be interesting, espcailly if they invest in vigorous gene-gineering of their species. They may smell and sound severely alien - or be good to eat. I'd worry about reciprocal indulgences of that last possiblity.

[pgrmdave]

I think that how they look would be largely determined by their environment. Consider what would have evolved differently if earth had a different mass, and had twice, or half the gravity that it has. If there was much less gravity, then it would be less necessary to have as much muscle to move, and more mass could be dedicated to other activities - thought, metabolism, disease fighting. In a lower oxygen environment, things would live longer but, assuming they still need oxygen, they would need to develop a way to either efficient use or gather the oxygen. In a higher oxygen environment, things would die quicker, but may not need such specialized organs as lungs and gills to obtain oxygen, instead absorbing it directly into the body.

[pie]

Hyderogenbond - You stated: "Alien life would probably contain DNA since the laws of physics and chemistry should be the same everywhere." - Yes, and the size of the home planet should dictate the surface gravity and ocean pressures on the planet. - So as you suggested that an alien world that was hotter with the oxygen and ozone lower, may select for humanoids with reptile skin and sleeping in the day.

I don't know if this type of world could exist. If it were hotter, the oceans may evaporate on an earth-sized planet such as Venus. If on the other hand the alien planet was larger than earth the surface pressures would be greater, so smaller animals might evolve.

Again, these higher pressures would not allow brain expansion on these larger planets, and would be unlikely to develop advanced civilizations.

I suspect that if there are any advanced civilizations in our universe, there home planet is similar size to earth, either being a littler larger, or smaller, but not much difference.

The oceans would have sharks similar to ours with some of sea sloath evolution similar to human. - It might be a scary thought to think our earth is common to all like in the universe with jurassic worlds being the norm.

[HydrogenBond]

The discovery of life deep in the oceans at tremendous pressure or bateria near hot mineral springs shows how adaptive life can be. Animals live high in the mountains, in the deserts, in the artic. These all show that a variety of environments can support life. It may come down to an optimum environ for fastest evolution. The earth seems to have served the purpose.

The need for liquid water is probably one of the basic criteria. More water moderates the surface temperature, while more pressure allows for more water. There is probably critical gravity that keeps the water from going to space even with high surface temp. if gravity gets too high life may remained in the water where one can feel weighless.

[Tormod]

And don't forget that for an extremely long period of time, our planet was ruled by dinosaurs - much, much longer than humanoids have been around, and a lot earlier, too.