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This question already has an answer here:

Allow me to pose yet another hypothetical.

Your spaceship has crash-landed on an earth-like planet. The air is breathable. The gravity is a bearable 1.2 g. The planet is teeming with fauna and flora. There are confirmed bodies of water: Lakes, rivers, etc. The fauna is not hostile to you. The flora seems familiar to what you've seen back home.

Your emergency food supplies will last you and your crew 6 months. There are no seeds or plants on-board your ship, but one of your passengers is a botanist.

My primary question is: Given a time-frame of 6 months, would a terrestrial botanist, with no skills in "xenobotany", be able to analyze alien flora/fauna for edibility?

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marked as duplicate by Mołot, Frostfyre, Ash, RonJohn, Ryan_L Sep 30 '18 at 15:38

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • $\begingroup$ worldbuilding.stackexchange.com/questions/47787/… $\endgroup$ – Brizzy Sep 30 '18 at 9:08
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    $\begingroup$ Three words: essential amino acids. Humans cannot survive unless fed histidine, isoleucine, leucine, lysine, methionine/cysteine (at least one of them), phenylalanine/tyrosine (at least one of them), threonine, tryptophan and valine. If the humans intend to have babies, they must also be fed arginine, cysteine, glycine, glutamine, and proline. The stranded humans would be better off spending the available time trying to engineer some sort of bacteria to eat local organic substances and synthesize those amino acids. $\endgroup$ – AlexP Sep 30 '18 at 12:20
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The first question to ask is how long do you expect before rescue. If it's six months or less, then don't bother to sample the local food, it isn't worth it.

If you're sure rescue will come within 7 months then still don't bother. Everybody goes a bit hungry for 7 months and then you get rescued.

Within a year? Maybe you can survive on half rations for a year, if you don't need to do a lot of strenuous work. It's worth the attempt.

If you don't expect rescue in time, then you have a problem. Did the life here evolve separately and it looks similar by coincidence? Then you probably have very little chance. Suppose for a moment that there is basicly only one way that things evolve, and all the biochemistry is basicly the same. Then there's still the matter of chirality. Many chemicals have a left-hand and a right-hand form. Very likely each different one could be either form, although maybe some combinations don't work for life. Call it two possibilities for sugars, two possibilities for amino acids, and two for nucleic acids, that gives you 8 different forms before we consider anything else.

If they are the wrong form you can't use them. Some of them could seriously get in your way. At the very best you might find a way to take the food and convert half of each necessary ingredient to the other kind, and then you can use half of it and hope the other half doesn't cause too much trouble. It probably won't be easy to get that far. And that's the very best case.

You do far better if somebody in the past 20 million years spread your kind of life to various places including this planet. Then the fundamental biochemistry will be the same, and what's different is just what's evolved different since it got here.

Then your problem is not much harder than people going to a new continent, like the English in Australia. Except that there won't be any aboriginals to tell you what's edible.

It would help a lot if sombody brought along a bunch of lab rats. Or a truly sophisticated biochemistry lab. Failing that, get some plants and some volunteers.

Give each volunteer a plant sample. They taste it. If it doesn't taste too bad, they hold it in their mouths for a few minutes and notice anything that's there to notice -- uncontrollable salivation, a numb feeling, pain, etc. They spit it out and carefully rinse their mouths with water. Next day, if they didn't suffer, try chewing and swallowing a little tiny bit. Over about a week, you get a sense whether each volunteer's sample has actively poisoned them. Of course there could be slow poisons, and for those you just have to hope. Try to avoid the things that taste worst. Your senses have evolved to detect some terran poisons and they might be useful here too. And if you can't tell what will poison you slowly, you might as well avoid the potential poisons that taste the worst.

If everything you find appears to be poisonous, you might try the old way to eat it anyway. Chop it up and boil it in plenty of water. Throw away the water and boil it again with new water. After 4 or 5 rinses, water soluble poisons will be much less. The remaining solids may have a lot of food value. Or maybe not. If you don't have anything better then it's worth a try.

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What you need is a chemist (preferably a food chemist) whith a giant, fully stacked laboratory.

Then the crew should start taking samples of organisms that are available in vast numbers. If one of them proves to be edible, the crew can at least survive by eating nothing else until they find another edible organism.

The chmist should start checking for poisons in all the organisms first. Only if he doesn't find anything that kills his crew, he should start analyzing the nutrients in those organisms. With the right chemicals and equipment available, he can even synthezise enzymes to make certain foods better digestible or brak down poisons.

A biologist might help deciding which organisms to sample first. Here on Earth, plants and fungi are always dangerous, because most of them developed some chemical defence against natural enemies and you never know which are poisenous for humans. Fruits might have less poison in them if the plant relies on animals spreading its seeds, but that is assuming that the alien organisms react to chemicals the same way as Earth organisms do.

Animals that typically run to either hunt or flee are a better bet. Their behavior lets us assume that they cannot defend against predators with poison.

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    $\begingroup$ "What you need is a chemist (preferably a food chemist) whith a giant, fully stacked laboratory." This is the obvious and only correct answer to "would a terrestrial botanist ... be able to analyze alien flora/fauna for edibility?" $\endgroup$ – RonJohn Sep 30 '18 at 15:09
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I think you're talking about convergent evolution. Given that this alien ecosystem was built around the presence of liquid water, it would be safe to assume that local life evolved along the same lines as life on Earth. Misidentification is bound to occur, especially as alien plant structures that are perceived to be analogous to their Earth counterparts may have subtle or radical differences in properties. For example, a cat's whiskers serve the same purpose as an insect's antennae, yet differ greatly in structure. I suggest a botanochemist skilled at identifying various chemicals would fare better than a generic botanist. The cassava plant, for instance, has a significantly higher cyanide content than the similar-looking potato. Knowing the chemical, rather than physical, differences between unknown flora could spell life or death for those who eat them. Hope this helps

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    $\begingroup$ OP is not asking about convergent evolution. Is asking if something looking like an apple on planet Bogus can be eaten or is poisonous. $\endgroup$ – L.Dutch Sep 30 '18 at 10:58
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    $\begingroup$ @L.Dutch "something looking like an apple" and not related to an apple is convergent revolution. On the other hand, OP is asking about analyzing things, not about how they came to be. $\endgroup$ – Mołot Sep 30 '18 at 11:04
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    $\begingroup$ This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review $\endgroup$ – Mołot Sep 30 '18 at 11:04
  • $\begingroup$ @Mołot this seems a reasonable answer to me. $\endgroup$ – RonJohn Sep 30 '18 at 15:07

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