What would aliens look like?

What would aliens look like?

Would they look like to the forms of life of our Earth because of evolutive convergence or not?

it actually occured to me recently, if RNA can form spontaneously (RNA comes before DNA cause you could have a RNA ribasome system for proto life), then probably something similar to anything thats ever lived here. That being said, you could have different amino acids or even other "building blocks" depending on what enzyme catalytic sites become prominent

>RNA comes before DNA
elaborate on this

>That being said, you could have different amino acids or even other "building blocks" depending on what enzyme catalytic sites become prominent

dont you think billions of years of evolution has shown otherwise? wouldn't natural selection follow a similar path anywhere life can form because it's a process similar to entropy?

RNA was the first information carrying molecule. If you disregard shut like prions

bump

source? there is speculation that RNA-based organisms might have existed before those of DNA, but to say otherwise without evidence is against the central dogma of molecular biology.

i think you are trolling

It's more reasonable to assume that it was, since RNA on its own can act as an enzyme, as well as having information storage capabilities, whilst DNA can only store information (although it is more stable).

there is evidence that RNA has both self-synthesis and translational processes, including potential enzymatic activity as a catalyst

there is absolutely 0 evidence that RNA has ever come before DNA.

>evolutionary convergence
Well, the specifics of our birth are after all, specific to our environment.
Less gravity or more gravity might significantly change pathways to evolution. With high enough gravity, birds might never come about.

Just because evolution occurs through random mutations does not mean that evolution has ``tried everything''. Some possibly beneficial mutations may have been nipped in the bud because the animal also had negative mutations. Extinction events can also cut evolution short.

While they might ``look like'' something that came from Earth, due to having skin, fur, and eyes, these common traits are simple at best.

In no way did I say that there was evidence. I just said it was more reasonable. It's just the simple application of Occam's Razor, given abiogenesis holds true.

probably completely different, though if a planet was very close to Earth (I mean in every condition), you'd likely see some comparable traits.

Well, if these aliens evolved on gas planets they might look like enormous hot air balloons. Even burgers cannot reach that size so in that case I'd say they don't look like humans.

Also they could evolve in free space in which case shape has little meaning, ref. Black Cloud, the science fiction story.

The you have planet born life which has to be in the Goldilocks zone:
- too hot and no chemicals will be stable enough to form life (Venus)
- too hot and chemical reactions would cease

Then you have planet types
- wet rock planets like Earth
- dry rock planets like Mars where life may have formed
- water world which might be OK for Kevin Costner but life might be water bound. Important advantage is that volume is larger than ground area in terms of useful living space and also provides good shielding against radiation blasts (Europa might fit the bill)
- gas planets (Jupiter and Saturn) with no solid ground and life would be free flying non-humanoid what would need to survive enormous amounts of radiation, possibly also pressure
- ice planets (Uranus and Neptune) are cold and life might not have started. Chemistry would be very slow

For planets like Earth and Mars I think life would be humanoid. Two arms, two legs, two eyes, two ears, two lungs, two kidneys etc. provide safety in redundancy. Not too big to avoid thermal overload but not too small to have a brain.

>Even burgers cannot reach that size
kek out of nowhere

I think that the relative abundance of certain materials or conditions could create different amino acids.

>carbon based because silicon is meme
>appendages for tool making
>living on land because you need fire
>probably warm blooded because lizards are dumb

i guess i dont know enough about chemistry then because the amino acids dont differ in composition all that much so;

i dont think our amino acids are the result of an abundance or lack of materials or conditions but rather an optimal solution to any biological process.

billion of years of evolution leaving a trail of organisms all mutating and evolving on their own yet we dont have animalia using other "building blocks".

extremophiles are the an example i can provide, if these bacteria live in extreme environments that other life on earth could not exist in, why havent they evolved to use something different? i think its because what we have today is the lowest common denominator of successful life

Warm blooded lizards or dinosaur-type creatures are possible. So yes, human or Cardassian.

But there is another of these threads already, they come up occasionally, and nobody is ever able to suggest a feasible alien which evolves to become intelligent enough to use tools, fire, and develop technology, which isn't humanoid. I posted similar in the other thread:

Given the Goldilocks zone criteria, evolution once out of water and moving towards creating technology is pretty much limited to:

>vertebrate (protection, locomotion, strength, mechanical efficiency)
>endoskeleton (weight, breathing mechanics)
>four legs (mechanical/calorific efficiency of larger organisms); then becomes:
>bipedal (use of hands)
>opposable thumbs
>binocular vision
>binaural hearing
>special senses arranged on the highest part of the body i.e. the head (for efficiency, and protection within the skull.)

Change any one of those qualities and you have something which will be inferior to its competition and will be selected against.

So being a bipedal humanoid seems inevitable if life on your planet is going to evolve to the level of using tools and technology. I am open to be proved wrong, and would actually love to be, because I can't envisage any techno-savvy creature which isn't humanoid.

The three smartest animals are dolphins, elephants and chimpanzees (after humans, of course). So clearly intelligence can manifest itself in a variety of morphologies.

you said "RNA comes before DNA". as far as we are aware, it does not. you also said "RNA was the first information carrying molecule"

you are making claims which require evidence

My guess would be "no." But anybody else's guess is as good as mine. We have no data.

Speculation without data is fun, and all, but it is not really anything to do with science.

>RNA comes before DNA


correct me if I am wrong, and I may be, but is not RNA made by DNA interacting with various enzymes an' shit?

In any case, even if a RNA/DNA system was the only way to get to life, why would we assume that this would lead to similar looking organisms?

Do you even bother to read the posts a few posts above, or just shitpost without having the courtesy to look what's already been said?

>why would we assume that this would lead to similar looking organisms?

Read this.

>What would aliens look like?
>Would they look like to the forms of life of our Earth because of evolutive convergence or not?

Half the life forms on Earth look like fucking aliens. Look at that deep water shit, or a platypus, or an ostrich, or a scorpion... life on Earth is unbelievably varied. You could design basically anything and probably find a correlation in the sea. Out of the sea, physiology starts to set a few more parameters; invertebrate/vertebrate, warm/cold blooded, endo/exo skeleton, limbs/wings, etc. Lower down the evolutionary tree the variety is immense, and the potential for variety on an alien world with similar life-supporting conditions to Earth would be equally high, i.e. equally varied. So whereas an alien biologist might look at an Earth angler fish and say, fuuuu dat crayzee fish got a fishing rod and light on its head, on their planet the angler might be an octopus with a collection of tiny tentacles which mimic a shoal of fish.

The point here is, life evolves to flourish in ecological niches, yes evolution does show convergence, but the scope for variety lower down the evolutionary tree is still immense.

Further up the evolutionary tree, physiology starts to set its parameters more stringently and the only real options for higher intelligent lifeforms which manipulate their environment (fire, tools, technology) are humanoid.