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If we arrived at another planet that could sustain life as we know it and had already evolved its own native systems of life, with diverse biomes, it is not necessarily the case that it evolved in a way that is compatible with our own. Likely, it would have levels of complexity similar to ours (virus-analogues, bacteria-analogues, and so on up to more complex life forms), but it is doubtful that it would evolutionarily "stumble upon" DNA compatible with our own. Right?

Would we be able to digest plant and animal-analogues if they still contained the same base elements but were not constructed around the same dna-based origination?

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  • $\begingroup$ They will absolutely certainly contain the same base elements. They will most likely not be made of exactly the same molecules; for example, there is nothing special of the two dozen or so aminoacids used by terrestrial life. This means that our enzymes won't work on them. (1) Start with Hypothetical types of biochemistry and a solid foundation in chemistry. (2) "Digest" as in eat them raw or only slightly processed, almost certainly no; use them as feedstock for our bioengineered fungi, most likely yes. $\endgroup$
    – AlexP
    Commented Mar 14, 2018 at 14:38
  • $\begingroup$ I would suggesting breaking this question down into two separate ones. Also I think that we have at least one question similar to the second one. $\endgroup$
    – The Square-Cube Law
    Commented Mar 14, 2018 at 15:03
  • $\begingroup$ Welcome to WorldBuilding.SE Kevin! Please note that we have a "one question per question" policy. For now I am voting to temporarily put this on hold until you edit it to comply with our guidelines for questions. You can learn more about the site by taking the tour and visiting the help center. For your first question you may want to add the tag worldbuilding-resources and for your second question you may be interested in I'm stranded on an alien planet. How can I tell what's good to eat? Have fun on the site! $\endgroup$
    – Secespitus
    Commented Mar 14, 2018 at 15:25
  • $\begingroup$ AlexP: Your second point is more to what I am asking. The fungi would be an intermediary that could recombine the base elements into forms like amino acids that we could eat. Thanks for that idea! $\endgroup$
    – Kevin Hulburt
    Commented Mar 15, 2018 at 15:11
  • $\begingroup$ "it is doubtful that it would evolutionarily "stumble upon" DNA compatible with our own. Right?" is at least partially covered by my question Why would life on a different planet use DNA? "Would we be able to digest plant and animal-analogues" is almost certainly a duplicate of my question Would humans be able to derive nutrition from foodstuffs found on alien planets? $\endgroup$
    – user
    Commented Mar 15, 2018 at 15:16

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  1. This article goes into a few types of molecules that can carry genes but aren't DNA/RNA.

  2. Digestion doesn't really intersect with the possession of DNA. We don't eat the DNA, we eat the base nutrients (nucleotides) that thing provides. That being said, what we eat can affect our DNA indirectly. If it's radioactive, we can absorb that radiation. If it has a crapload of sugar in it, the end result can be an insulin disorder, some of which are actually heritable in something close to a Lamarckian sense.

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  • $\begingroup$ But aren't all nucleotides built on the fundamental rules of DNA? If an organism evolved based on a different rule set, we wouldn't get the amino acids we are unable to produce: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Right? $\endgroup$
    – Kevin Hulburt
    Commented Mar 15, 2018 at 15:16
  • $\begingroup$ You asked if it can be digested, not if we could survive solely on non-DNA'd substances. Those amino acids being formed without a 'compiler' would be a monkey-and-typewriter situation. $\endgroup$
    – Carduus
    Commented Mar 15, 2018 at 15:32

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