[Baron Munchausen]

Originally posted by dogscoff:

quote:

---

Do you think the aliens warnings against eating anything not native to earth would be absolute? Seems to me that organic matter is organic matter, is it not?

Someone stop me if my science is off here, but here's how I understand it:

Most of the things we eat are pretty complex- proteins, fats, sugars and vitamins- and they are all produced by plants or animals. For them to exist on another planet, therefore, that planet must have evolved its own plants and animals that produce those same molecules: Parallel evolution might well come up with something similar or identical to Earthly forms, but just as none of us seriously expect to find humanoid aliens with easily recognisable body parts and features, I think we're unlikely to find anything with identical or near-identical bio-chemistry.

I guess we'll never be sure until we get to another planet and find out, but I think it's likely that stuff evolved on another world would be inedible to us.

On the other hand, the bio-chemistry is almost certain to have *some* similarites: Oxygen is almost certainly going to be part of the equation, because no other element is at once stable and volatile enough to contain and then release the energies needed for life. Hydrogen is another likely contender because (A) there's bloody loads of it and (B) it comes packaged up with the oxygen in the form of water. Carbon is likely to be there as well, because not many other atoms can form themselves into such complex molecules. That gives you all the necessary ingredients for carbohydrates (edible sugars). Granted, there are probably a zillion ways those three elements could combine, but I guess it's reasonable that our survivors might find something that could be boiled down into edible carbohydrates.

Finally, there are some simple nutrients we ingest that are available in non-organic forms and therefore would be easy to find on another planet: iron, zinc, magnesium (calcium?) could probably be sourced locally- daresay you could dissolve them into drinking water, if your local friendly mountain stream hadn't already done the job for you.

Anyway, for plot purposes it's quite an interesting question. Anyone with some actual knowledge rather than my pop-science want to chip in?

---

No 'professional' expertise here, but from what I know you are on the right track. Though the basic elements involved are simple, there are a gazillion possible different proteins that can be formed from those very simple elements. Our digestive systems are designed to break down certain types of fats and proteins and there are quite a few things even right here on earth that we cannot digest. It takes another specific protein, an enzyme, to break down a given protein into a simple usable form. If your system cannot make the right protein, no digestion is going to happen. There is no known reason that life on another planet would even use the same amino acids (simplest proteins) let alone compatible finished proteins. Maybe 'food' from an alien eco-system wouldn't automatically kill you, but it would almost certainly not provide any nutrition beyond a few basic minerals as already noted. Then again, some of the most deadly poisons known are also proteins made by exotic plants and animals right here on earth.

What I find more interesting is how would our immune system handle microbes from another planet? Bacteria and fungi are much more 'flexible' than more complex organisms in what they can digest, and humans might just be 'compatible' enough to be digestable by the local microflora. If your immune system cannot combat or doesn't even recognize the invaders, you might start to break down like a corpse while still alive. And then of course, we have the reverse question... would the earth-life bring some disease that this alien eco-system could not cope with and wipe it out?

Next we have to worry about 'macro' problems like gravity, adapting to the new climate, the day/night cycle (it might be 8 hours or 80 hours... ), and whether the sunlight is compatible with the earth plants. Not enough light in the right wavelengths, little or no plant growth. Too much ultraviolet - damaged plants and lots of skin cancer in humans. And not only days and nights, but how long are the 'seasons'? Might be a few months like earth, or might be a few years. How do you stock up food for a years-long 'winter' with plants evolved for only a few months per season?

You can presume that these 'nice' aliens would have found a world fairly close to earth in major characteristics but they cannot have had time to think of all of the details like light wavelengths.