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> implies that we and the alien bacteria had a common ancestor My intuition suggests that wouldn't be necessary. For example, if I saw a snowflake like structu

> implies that we and the alien bacteria had a common ancestor My intuition suggests that wouldn't be necessary. For example, if I saw a snowflake like structure on another planet I wouldn't be surprised since that kind of structure is a result of the physical properties of the elements involved. It could be the case DNA is very similar in that respect, a mathematical necessity given the properties of hydro-carbons. I suspect the science on that issue isn't settled.

perl4ever 7y ago
I'm thinking someone may have proved by construction that DNA isn't the only possible code. Didn't someone make "artificial" DNA by substituting something chemically for some of it?
- reggieband 7y ago
  That sounds slightly different than what I mean. You appear to be saying: "It is possible something DNA-like could be constructed from different materials in different codes and it would still be viable". I was saying: "It is possible hydrogen, carbon, oxygen, etc. will form into DNA as long as suitable conditions exist and this is common enough occurrence that multiple sources of DNA independently developed across the galaxy/universe". I only say this to assert that the appearance of DNA from a source other than Earth should not necessarily imply a common ancestor.
  - kevinpet 7y ago
    Maybe so, but it would be surprising if it settled on the same instruction set https://en.wikipedia.org/wiki/DNA_codon_table https://en.wikipedia.org/wiki/DNA_codon_table
- suby 7y ago
  Not sure if this is what you're referring to, but we have created DNA with additional "letters" which don't appear in nature. https://www.livescience.com/64829-hachimoji-dna.html https://www.livescience.com/64829-hachimoji-dna.html
anyfoo 7y ago
Not a biologist, but my impression is that the concepts involved in DNA/RNA, and especially the machinery around it, are so complicated and have so many degrees of freedom, that snowflakes, which are rather simple crystallizations of only water, may not be an apt comparison. Maybe it's closer to, say, someone having just learned the basics of analogue electronic circuits (but nothing beyond that), going into a basement, and coming out with a fully formed IBM-compatible PC with USB ports. Again, not my field, and I'm happy to be taught otherwise on that one.
- insickness 7y ago
  If you're saying that DNA is too complex to have evolved on earth, where else would it evolve? Panspermia just puts the origin of life in another location in the universe. It doesn't answer any questions about how that complexity would evolve.
  - throwaway2048 7y ago
    Thats not what is being said, hes saying that if life evolved twice, it would be almost certainly completely different and "incompatable" at a molecular level. Consider the design of processor architectures and operating systems, similar design goals but typically one cant run code from the other.
- marcosdumay 7y ago
  The RNA to protein encoding specifically is completely free and arbitrary.

perl4ever 7y ago

I'm thinking someone may have proved by construction that DNA isn't the only possible code. Didn't someone make "artificial" DNA by substituting something chemically for some of it?

reggieband 7y ago
That sounds slightly different than what I mean. You appear to be saying: "It is possible something DNA-like could be constructed from different materials in different codes and it would still be viable". I was saying: "It is possible hydrogen, carbon, oxygen, etc. will form into DNA as long as suitable conditions exist and this is common enough occurrence that multiple sources of DNA independently developed across the galaxy/universe". I only say this to assert that the appearance of DNA from a source other than Earth should not necessarily imply a common ancestor.
- kevinpet 7y ago
  Maybe so, but it would be surprising if it settled on the same instruction set https://en.wikipedia.org/wiki/DNA_codon_table https://en.wikipedia.org/wiki/DNA_codon_table
suby 7y ago
Not sure if this is what you're referring to, but we have created DNA with additional "letters" which don't appear in nature. https://www.livescience.com/64829-hachimoji-dna.html https://www.livescience.com/64829-hachimoji-dna.html

anyfoo 7y ago

Not a biologist, but my impression is that the concepts involved in DNA/RNA, and especially the machinery around it, are so complicated and have so many degrees of freedom, that snowflakes, which are rather simple crystallizations of only water, may not be an apt comparison. Maybe it's closer to, say, someone having just learned the basics of analogue electronic circuits (but nothing beyond that), going into a basement, and coming out with a fully formed IBM-compatible PC with USB ports. Again, not my field, and I'm happy to be taught otherwise on that one.

insickness 7y ago
If you're saying that DNA is too complex to have evolved on earth, where else would it evolve? Panspermia just puts the origin of life in another location in the universe. It doesn't answer any questions about how that complexity would evolve.
- throwaway2048 7y ago
  Thats not what is being said, hes saying that if life evolved twice, it would be almost certainly completely different and "incompatable" at a molecular level. Consider the design of processor architectures and operating systems, similar design goals but typically one cant run code from the other.
marcosdumay 7y ago
The RNA to protein encoding specifically is completely free and arbitrary.