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So there's two high-confidence bets we can make about alien life: (1) They will probably share huge swaths of the basic chemistry and machinery: proteins, suga

So there's two high-confidence bets we can make about alien life: (1) They will probably share huge swaths of the basic chemistry and machinery: proteins, sugars, starches, fats, and even more surprising things like cell walls and digestive acid and (something like) DNA. The building blocks of life are basic chemistry, and are some combination of "the simplest possible molecule that can do a thing" and "things that arise naturally from inorganic processes". (2) There will almost certainly be 0% overlap in terrestrial and alien DNA, even assuming aliens use DNA and use the same four amino acids to encode their DNA and even assuming they have identical proteins and cellular structures. This is because the encoding from DNA to proteins is more-or-less arbitrary, and determined by both the exact cellular machinery used to turn DNA into proteins and by our genetic history. Even in our own cellular machinery, different DNA sequences can code for the same protein, so you can encode any individual protein in a bajillion different ways. The only real reason for to different organisms to share any common DNA sequences is because they both derive from a common ancestor. If our DNA and alien DNA overlap in any meaningful way, even with the tiniest of percent, it's basically conclusive proof of exogenesis of some sort. So basically, it is very likely we'll be able to eat aliens (probably no more or less likely than how likely it is you can eat any particular plant or animal on Earth, to be honest), and almost impossible that we could ever hybridize alien and terrestrial plants and animals.

openasocket 8y ago
I think it goes further than that, that alien and native lifeforms will probably be toxic to one another. All life on this planet evolved in tandem, and have some of the same basic compounds for life, so there are few toxic interactions between life forms, excluding those evolved for defense (and even then there are exceptions, plenty of plants contain. And even then there are plenty of exceptions. But lifeforms from a completely different evolutionary line may use completely different proteins for basic functions. Even using the same proteins but of the opposite chirality could result in toxic reactions. I think that even if we found alien life that evolved and developed on a planet much like ours, and used the same amino acids, metabolic processes, and cellular structures, the odds are high that contact with them would result in toxic interactions.
- saalweachter 8y ago
  You've got to weigh "we didn't evolve to specifically eat it" against "it didn't specifically evolve to prevent us from eating it". I'm not sure we'll get an answer to which is a bigger factor unless we find some xenobiology and take a bite. A lot of digestion is pretty elementary, and built upon our stomachs' acid bath -- proteins go in and are unwound and broken down. Most foods that cause problems later down the line contain a protein that both (a) is resistant to the stomach acid, and doesn't break down before hitting the intestines and (b) causes a problem when it hits the intestines. Barring that - or incorporating elemental poisons like arsenic at levels we can't cope with - I'd personally bet that if you charred a random alien critter over a fire and wolfed it down, it's not crazy that your stomach acids would break down anything that survived the fire and would otherwise harm you, and you'd be able to extract a reasonable mix of sugars, fats and proteins from what you'd ate. It's not impossible that an entire planet would have some proteins common to all of their lifeforms that both (a) didn't break down easily when cooked or digested and (b) were incredibly lethal to terrestrial life, but there's no ab initio reason to think they would or wouldn't, one way or the other.
  - openasocket 8y ago
    The stomach isn't a perfect barrier, there's always something that gets through. If it didn't we wouldn't be able to take drugs orally. Our bodies have an entire subsystem devoted to processing compounds that made it through the main digestive system into the blood stream. The liver is dedicated to metabolizing these substances, in a process literally called "xenobiotic metabolism". Sure, the odds of a particular compound found in some alien lifeform having a toxic interaction with our bodies is small, but I consider the odds of one of the hundreds of thousands of different types of compounds in that lifeform having a toxic interaction is on the higher side. Oh, and to be clear, by toxic interaction I don't necessarily mean a poison, per se. It could also have a carcinogenic effect, or if the compound is common enough in the creature and undigestable through the stomach and intestines it could overload the liver, etc.
    - saalweachter 8y ago
unparagoned 8y ago
I wonder if some of the early core functionality such as replication, splitting, energy generation, etc. only has a few simple and effective possibilities? Are there any really simple RNA/protein patters that almost just have to occur from a statistical/mechanical view?
outworlder 8y ago
> They will probably share huge swaths of the basic chemistry and machinery: proteins, > So basically, it is very likely we'll be able to eat aliens Their proteins may be folded in the opposite direction though. That would make things difficult.
- saalweachter 8y ago
  Do you mean from a digestive standpoint or are you thinking prion diseases?

openasocket 8y ago

I think it goes further than that, that alien and native lifeforms will probably be toxic to one another. All life on this planet evolved in tandem, and have some of the same basic compounds for life, so there are few toxic interactions between life forms, excluding those evolved for defense (and even then there are exceptions, plenty of plants contain. And even then there are plenty of exceptions. But lifeforms from a completely different evolutionary line may use completely different proteins for basic functions. Even using the same proteins but of the opposite chirality could result in toxic reactions. I think that even if we found alien life that evolved and developed on a planet much like ours, and used the same amino acids, metabolic processes, and cellular structures, the odds are high that contact with them would result in toxic interactions.

saalweachter 8y ago
You've got to weigh "we didn't evolve to specifically eat it" against "it didn't specifically evolve to prevent us from eating it". I'm not sure we'll get an answer to which is a bigger factor unless we find some xenobiology and take a bite. A lot of digestion is pretty elementary, and built upon our stomachs' acid bath -- proteins go in and are unwound and broken down. Most foods that cause problems later down the line contain a protein that both (a) is resistant to the stomach acid, and doesn't break down before hitting the intestines and (b) causes a problem when it hits the intestines. Barring that - or incorporating elemental poisons like arsenic at levels we can't cope with - I'd personally bet that if you charred a random alien critter over a fire and wolfed it down, it's not crazy that your stomach acids would break down anything that survived the fire and would otherwise harm you, and you'd be able to extract a reasonable mix of sugars, fats and proteins from what you'd ate. It's not impossible that an entire planet would have some proteins common to all of their lifeforms that both (a) didn't break down easily when cooked or digested and (b) were incredibly lethal to terrestrial life, but there's no ab initio reason to think they would or wouldn't, one way or the other.
- openasocket 8y ago
  The stomach isn't a perfect barrier, there's always something that gets through. If it didn't we wouldn't be able to take drugs orally. Our bodies have an entire subsystem devoted to processing compounds that made it through the main digestive system into the blood stream. The liver is dedicated to metabolizing these substances, in a process literally called "xenobiotic metabolism". Sure, the odds of a particular compound found in some alien lifeform having a toxic interaction with our bodies is small, but I consider the odds of one of the hundreds of thousands of different types of compounds in that lifeform having a toxic interaction is on the higher side. Oh, and to be clear, by toxic interaction I don't necessarily mean a poison, per se. It could also have a carcinogenic effect, or if the compound is common enough in the creature and undigestable through the stomach and intestines it could overload the liver, etc.
  - saalweachter 8y ago

unparagoned 8y ago

I wonder if some of the early core functionality such as replication, splitting, energy generation, etc. only has a few simple and effective possibilities? Are there any really simple RNA/protein patters that almost just have to occur from a statistical/mechanical view?

outworlder 8y ago

> They will probably share huge swaths of the basic chemistry and machinery: proteins, > So basically, it is very likely we'll be able to eat aliens Their proteins may be folded in the opposite direction though. That would make things difficult.

saalweachter 8y ago
Do you mean from a digestive standpoint or are you thinking prion diseases?