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Alternative Lifeforms

XNA DNA life humans aliens ET alternative life Titan Early Earth Silicon Lifeform

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Yuli Ban

Yuli Ban

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This piece from Listverse got my mind going.

10 Hypothetical Forms Of Life

In the search for extraterrestrial intelligence, some have been accused of harboring a sense of “carbon chauvinism,” expecting other life-forms in the universe to be made of the same biochemical building blocks as we are and tailoring our searches accordingly. Here are 10 examples of biological and nonbiological systems that stretch the definition of “life.”

I've long heard of the hypothesis that there were multiple geneses on Earth. The reason why we don't see evidence of alternate forms of DNA (i.e. XNA)? DNA-based life simply outproduced XNA-based life on the surface. 
It's possible that Earth's situation means that DNA-life was the best method of life evolving. We have a cool, temperate climate with lots of salty water, just enough solar radiation, and a close and very large tidally-locked satellite. For DNA-life, that (or a variant of it) is the best possible circumstance. Thus, DNA-life molds the planet to more totally allow it to survive over the course of billions of years. Sure, paramecia aren't going to construct moons, but they can release gases that alter the very chemistry of the planet. Cyanobacteria did this billions of years ago, turning our sterile and inhospitable world into the oxygenated zoo it is now.
But XNA may require something much different. If XNA took root on Earth, it'd inevitably become something more like DNA because our environment favors DNA-based life. If it can't adapt, it all goes extinct. Move XNA to Titan, however, and everything changes. XNA actually thrives on Titan.
Why might XNA not have evolved into something intelligent on Titan?
1) We don't know it hasn't. We've only gone there once, and we've only gone to a single part of Titan. It would be as if an alien probe landed in the Atacama desert. It's possible that, underground, a very alien form of intelligent life has evolved, something similar to a fusion of animalia and fungi.
2) Energy. The reason why evolution happens is because life seeks more energy efficient means of reproduction. If you're not receiving enough energy in the first place, you won't have enough energy to reproduce. Titan receives very little solar energy. XNA would need to be ultra-highly efficient to survive, unless it utilized a way to combust methane on a microscopic scale in order to reproduce. Which is unlikely, because chemistry doesn't work that way. And that's on a universal level (hence why we have Laws of Physics but no Laws of Life).

In order for intelligence to rise, you need some way of creating neural networks. Even fungi that have developed a sort of intelligence do so through creating a form of fungal neural network. If the material you're working with can't act as a neural network for some reason (energy isn't flowing well, for example), then you're not developing life.
So let's keep discussing this, "alternative lifeforms."

And remember my friend, future events such as these will affect you in the future.




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Another funny aspect of the chemistry of life is chirality; you can have two molecules with the exact same formula, and exact same connectivity between molecules, yet they're still different. These "enantiomers" are exactly the same, except for one small inconvenience; they are mirror images. Say you have a carbon; it can form four bonds in the shape a tetrahedral pyramid, with each bond 109.5o away from the other. If you move around the geometric position of any molecule bonded to a chiral carbon, you can get a mirror image. These two compounds, mirror images, will be optically active; one will spin polarized light to the left, the other one to the right. Left is levorotatory, right is dextrorotatory.


Take any chiral amino acid (let's say Arginine), and you can have L-arginine or D-arginine; turns out, life on Earth is left-handed. In fact, since we can't use D-molecules as building blocks, all chiral naturally occurring amino acids that we use are L-isomers. For some reason, left-handed organic molecules beat out right-handed ones in the formation of life. You can still eat right handed molecules, but you can't really break them down or use them for other processes in the body.


We haven't really had a clue as to why left-handed life won out, but this article describes the discovery of the same left-handed bias in meteorites that fell to Earth, which adds weight to the panspermia argument. But for all we know, life could just as well exist in its right-handed form somewhere out there.




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I think the most likely alternative lifeforms will come from technology evolving to self awareness.  There are many advantages to genetic information transfer, but there are also many things that can inhibit the prolonged evolution of these types of lifeforms.  A good example would be high levels of radiation.  Technology based lifeforms would have a much higher chance of propagating. 




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I'd known about most of these, but having the chance to revisit some of the ideas now is fun.


iChells actually have me wondering if it might be a viable mechanism for off the shelf implantable organ replacements and prosthetics. Not being biological cells in the traditional sense would they be able to bypass the immune systems reaction to foriegn cells, while allowing the structure and function to mimic human biology? (I had a similar idea years ago about 'xna', that we might create something too different for immune systems to see as something to attack, but also as a potential means of creating life forms like yeast the excrete pharmacuetical grade componds)


the plasma lifeforms strike me as just the new form of the argument in highschool biology we had about how consumption and reproduction couldn't be the only defining characteristics of life because fire (and crystals) did those things as well. I remember writing a silly story of a person who discovered that fire was in fact a life form and began communicating with it, struggling with the fact that it lived so much more rapidly than organic life.


Life on titan actually plays a couple roles in some novels I've been outlining about humanities future. Although in this case it was generated on purpose by us...


come to think of it I think that's the same series where I have a silicon based alien race that creates machines that look an awful lot like organic life and when it first encounters us, thinks we are 'robots' whose masters died out long ago.


The gravity (and nuclear forces) and plasma lifeforms might make decent sci-fi short stories. I especially life the idea of 'space whales' that feed around blackholes as if they were reefs. bUt life forms living on the surface of neutron stars would be interesting, how would one such civilisation explore past their own 'planet' if leaving the surface disrupted the fundamental forces that make their living possible. and how would we be able to interact with them if going to their world would destroy us.


Gaia, schmaia. I was working on a manga involving this concept a decade ago, based on an idea I had a decade before that at least. It's not really a new form of life so much as recognizing a symbiosis of varried lifeforms in an ecosystem and comparing them to the varied cells in a body creating a greater whole.


The meme one just kinda annoys me. Memes don't have motive or thought, they are the sort of psuedo life that virus' are.

(see )


and van newman probes have to be created first, they don't rise spontaneously, so you still kind of have to have one of the other groups create one first.

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Yuli Ban

Yuli Ban

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Here's a thought experiment: we often talk about how the genesis of life on other planets. We say that perhaps life began/arrived on Mars or Venus billions of years ago and escaped underground as conditions deteriorated.


What if the same happened on Earth, and there's actually an entirely different kind of life living miles beneath our feet? On the surface and deep underground, there are three domains of life. Go further down, and there's an entirely new classification even more fundamental than the domains. 


This would be due to the sheer environmental differences that exist further down into Earth. Pressures and temperatures are so extreme, in fact, that the material found around this point would resemble a non-Newtonian liquid. There's absolutely no light, and the oxygen that can be found is at a much, much higher concentration than on the surface, a level that might even be toxic to surface life. 


Extremophiles that manage to survive would be left to evolve in conditions even more inhospitable than the surface of Venus. And that's just on Earth. 

And remember my friend, future events such as these will affect you in the future.

Also tagged with one or more of these keywords: XNA, DNA, life, humans, aliens, ET, alternative life, Titan, Early Earth, Silicon Lifeform

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