Re. the origin of stuff in our food - there is no synthetic organic chemistry (that is, starting with water, CO2 and energy) relevant to the production and processing of food. IOW, all our nutrition is based on other organisms. Even most of today's organic chemistry that has nothing to do with foods (i. e. plastics, rubbers...) starts with the remnants of living organisms: Petrol oil.
Re. the pallatability of alien life forms: Of course, any one of them could happen to be toxic - no big deal, we know that from our own biosphere. Then they could ALL be toxic if they happened to for example use amino acids in their proteins that are toxic to terran organisms (take indospicin, for example). Another possibility is that they might not be toxic, but non-nutritious. Some of their fat or sugar chemistry might employ chemicals bounds for whose breakup we have no matching enzymes. That is known on Earth, too - cellulose is nothing but polymeric glucose, yet humans cant't digest it.
IIRC, Buzz Aldrin and his coauthor John Barnes turned this into a plot device in "Encounter with Tiber": The ETs visiting Earth find they cannot use the products of our biosphere for food because something in the amino acid composition doesn't match. Therefore, the Tiberians abandon their plans of colonising Earth.
Last edited by Arneb; 2012-Mar-11 at 04:41 PM. Reason: One typo, two clarifications
To restate what I said in the other thread: I think it's extremely unlikely. It's not just protein chirality; why should all proteins even with the right chirality be edible? How many different proteins could be made with say, the exact same molecular formula as hemoglobin or insulin? How many isomers of common carbohydrates? I don't think the body would "recognize" these at all, and would (at best) flush them out.
Second, it is probably no accident that all the 20 amino acids of the terran genetic code are relatively simple ones and fall into a few easily identifiable classes. I don't think ETs would consist of 20 totally different aa's, so some kind of nutritional value is at least conceivable. However, the possibility of showstoppers existing in the ET biochemistry are probably endless.
So we should probably invent a way to make our food from CO2, H2O, trace elements, and electricity, if we ever want to go to the stars. Yummy. But it should beat seeing your entire hydroponic culture fall prey to one nasty fungus...
For colonization you ultimately want to transplant your own compatible biosphere... and for longer term space travel carry enough of it with you.
Are you talking about sustainable space colony?!
STARGAZING: All I see are the lights of a billion places I'll never go. Howard Tayler
I'm a cynical optimist. I think the only way out is through, but once we get through it'll be better. Very different, but better. Howard Tayler
It is not the strongest of the species that survive, nor the most intelligent, but the one most responsive to change. Charles Darwin
"It is the duty of the writers to seduce me into suspending my disbelief!" Paul Beardsley
In my op, the only way to get around the problem is to bring our own food--that is, our own agriculture--with us. Yes, this unfortunately entails introducing species that may, over evolutionary timescales, completely overwhelm and alter an alien planet's biosphere; I think this grim choice will eventually confront any spacefaring descendants of ours.
It is a tragedy to "destroy" another planet's biosphere, but perhaps we can live in a contained environment? Even "habitable planets" may not be absolutelyOriginally Posted by Romanus
The closer to "human-friendly" an alien planet's biosphere, the more likely that there will be things there that can kill us: not so much predators, but parasites, environmental toxins, prions, diseases....
Don't colonize planets with preexisting biospheres. It makes more sense to just manufacture habitats in space--no gravity well to climb out of, and the other sub-optimal properties of planets.
Stop being biological. Then the only food one needs is energy, say in the form of electricity. Got light, hot and cold, or hydrogen? Good to go. They could live in hard vacuum, if they so desire. Or even less hospitable environments.
I recall a far future sci-fi story where more than 30 or 40 light years from Earth and you ran out of sources of cholesterol, edible sodium chloride (and caffiene!) as other races built on different schemes dominanted.
Allergies come to mind.
Metabolic clogging of important pathways.
Odd sugars that cleave into toxic substances. (A common garden plant has sugars that are specifically taken up by the heart muscles of mammals. Then once the part the cell wants is cleaved off, the left over is a molecule of hydrogen cyanide. (Nice trick, huh?)
Even humans showing up on Earth from somewhere else would have to learn what they could eat and what they couldn't.
Well, yeah, except for fruit, no plant part wants to be eaten, and in the case of capsicum peppers, not everything that wants to be eaten wants to be eaten by mammals.
Of course, being humans, we cheat. We took a plant that can very toxic and found a way to process it into a staple.
Assuming very large similarities between them and us, we just might find a way to make some of the alien plants and animals, assuming they have such categorizations, edible.
I'm not sure how cooking would be harder than genetically engineering humans to a specialized roll.
SkepticJ is really into developing the non-biological version of human.
It skeeves me out a little their* enthusiasm. I personally don't think for the foreseeable future it would be any improvement.
*as a gender neutral pronoun.
Leech out the poison by soaking and replacing the water several times, boil until it breaks down into a non-toxic form, leave to rot in the frozen permafrost until it's, technically, edible, humans have a long experience with making the toxic edible.
Leech out the poison by soaking and replacing the water several times, boil until it breaks down into a non-toxic form, leave to rot in the frozen permafrost until it's, technically, edible, humans have a long experience with making the toxic edible through the art and science of cookery.
Unless Europa has native life, or some chemosynthetic bacteria are munching on rocks, or whatever, in the crust of Mars, or some other locale within our Oort cloud, then it could be centuries, even thousands of years, before we encounter alien life in person. I can't reasonably conceive that humans would have interstellar travel capability without also having advanced robotic technology; it's more inconceivable to me than that humans would make it to Mars on vacuum tube computers.
I'll belabor this no further in this thread.
I suspect that, because of chirality, at least half of all alien biochemistry will be indigestible to us; in fact I would expect the majority of biospheres will be largely inedible, no matter how much you cook the organisms concerned. Most compounds that don't kill us would be only useful as roughage, (unless some sort of genetic engineering is employed). Radical engineering might allow us to digest alien compounds directly, or engineered gut flora might do the job. Probably it would be a bit of both. By the time we encounter any alien proteins we will probably have relatively advanced biotechnology that would make this possible, or we may have passed entirely beyond the biological phase.
Thank you for this realistic comment!Originally Posted by SkepticJ
There are some creatures and plants on this planet you wouldn't want to eat. Some are poisonous. And it may turn out that some sweet looking fruit hanging from an alien tree might want to eat you back! Ouch!
Of course, alien fruit will have strategies to be eaten by the right thing, like capsicum in hot peppers, but want to be eaten all the same.
Also they are much, much more efficient at turning sunlight into chemical energy, I doubt anything we would call a plant would be that kind of a threat.