Some of Podrock’s tongue-in-cheek comments regarding the exploitation of alien life forms as a food source (see earlier thread on Ceres’ bright spots) raise some interesting questions. Would extraterrestrial organisms be edible? Would we have to worry about them eating us?

I’ve always felt that neither of us would have to worry about being eaten by the other because our biochemistries would be incompatible.
Even if we were both carbon-based, oxygen-breathing, water-dependent creatures, (the only configuration we can conceive of that would allow the existence of sufficiently complex organic molecules and chemical reactions) a totally independent evolution would suggest that our proteins would be very different. Other biologies based on silicon and other elements have been suggested, but as far as I know, only carbon is chemically able to easily form complex molecules in water solution at moderate temperatures. But even so, an independently evolved carbon life form would still be very different from us at the molecular level.

Alien animals or plants would be poisonous to us, or at least, undigestible, and vice-versa. They are probably sufficiently similar to us to cause severe allergic reactions as our immune systems encountered alien protein and mobilized against it. But I really don’t know enough chemistry to know for sure.

I realize our digestive enzymes are designed to break down our food into innocuous components that can be easily assimilated and metabolized, but would they be able to handle alien flesh and plants? Even here on earth, where all life is related, descended from one single ancestor, there are many other creatures that we find poisonous, undigestible, or allergenic. Great white sharks thrive on seals, fish and surfers, but they can’t eat redwood trees. Our ability to use fire to prepare food has greatly expanded our ability as a species to consume otherwise undigestible plant and animal tissue. And I’m sure we could use technology to process alien flesh so we could eat it. But any technology capable of that could surely synthesize food from materials easily found in space–methane, water, ammonia and minerals. We wouldn’t need to eat the local wildlife.

Any comments?