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They stitched 25 random amino acids together and then assess the resulting polymer for solubility and foldability. Solubility requirement is self explanatory, c

They stitched 25 random amino acids together and then assess the resulting polymer for solubility and foldability. Solubility requirement is self explanatory, can't have life that is insoluble in water. Foldability is basically how likely for these polymers to entangle and collapse on itself. This is critical because protein folding depends on this process to generate highly compact and dense atomic machineries. They find out stuff that are too soluble can't fold well because they prefer water over other amino acid. And that seems to exert a selection pressure, ending up with a specific set of amino acids that life depends on.

anonymouskimmer 4y ago
I wonder how this selection process varied as proteins started mixing, or even bonding, with lipids and sugars. Probably not that much, though those processes may have allowed the gradual inclusion of the other amino acids.
yyyk 4y ago
>Solubility requirement is self explanatory, can't have life that is insoluble in water. Foldability... is critical because protein folding depends on this process to generate highly compact and dense atomic machineries. That's a teleological fallacy. Evolution doesn't have a destination, therefore you can't assume the evolution criteria from the end result only. Imagine looking at all of life, adding a 'resulting in human life' criteria and therefore completely failing to understand the evolution of avians. If the authors want to argue amino acids 'evolved', they need criteria that make sense for amino acids in early Earth environment and not assume the result.
- galaxytachyon 4y ago
  Not sure what part are you arguing although I get the general gist. Still, to make sure I don't misinterpret you, can you expand a bit on which part of those requirements are teleological fallacy? The context is for life on earth. All life on earth depends on proteins that are (mostly) soluble in water and almost all protein requires folding to be functional. It is a valid hypothesis to say solubility and foldability are necessary criteria. Then they tested it and found based on these criteria, the current set of amino acids is favored over other sets. Look like good science to me.
  - yyyk 4y ago
    >It is a valid hypothesis to say solubility and foldability are necessary criteria. Necessary criteria for life, yes. Is it neccesary for evolution? The article's argument is that amino acids 'evolved'. Evolution needs a selection mechanism, and the article does not explain why evolution would favour solubility and foldability, so the article* doesn't come close to proving evolution happened much less explaining its details. Perhaps some other unexplained chemical process favoured these acids, or it was an accident. It's like looking at current status of biosphere, and concluding that life optimizes for insectoids because insects have the largest biomass. It's just an argument that assumes the result. * Perhaps the article is bad reporting and the reported study had an actual argument for this.
    - galaxytachyon 4y ago
      I see, the actual scientific paper is always a much better source for this stuff than a popsci article. The term "evolution" was used very loosely in the salon article. By your standard it would be more appropriate to call the process "selection". The amino acids never changes or evolved to become anything different, just that some were chosen to become the building blocks of life while others were ignored. The reasons for this selection were likely the two criteria mentioned above and that was backed up by the main study. You will notice I never used "evolution" to describe the process in my posts. I skipped the salon article entirely and only used the link they provided to read the real study so I didn't notice what they said in the salon page. Anyway, it is just some semantic stuff.
      - yyyk 4y ago
        Right, so I read the study instead of the article. Good idea. It's simply that the popsci article claims something that isn't the original study. The article does argue for evolution before life[0], and the study doesn't claim that at all. Either Salon simply misunderstood the study, or spiced it up so that aggregators like HN would pick it up. [0] "So by testing which libraries had the best solubility and structure, the researchers could conclude that proteins were evolving and driving natural selection before even forming living things."

anonymouskimmer 4y ago

I wonder how this selection process varied as proteins started mixing, or even bonding, with lipids and sugars. Probably not that much, though those processes may have allowed the gradual inclusion of the other amino acids.

yyyk 4y ago

>Solubility requirement is self explanatory, can't have life that is insoluble in water. Foldability... is critical because protein folding depends on this process to generate highly compact and dense atomic machineries. That's a teleological fallacy. Evolution doesn't have a destination, therefore you can't assume the evolution criteria from the end result only. Imagine looking at all of life, adding a 'resulting in human life' criteria and therefore completely failing to understand the evolution of avians. If the authors want to argue amino acids 'evolved', they need criteria that make sense for amino acids in early Earth environment and not assume the result.

galaxytachyon 4y ago
Not sure what part are you arguing although I get the general gist. Still, to make sure I don't misinterpret you, can you expand a bit on which part of those requirements are teleological fallacy? The context is for life on earth. All life on earth depends on proteins that are (mostly) soluble in water and almost all protein requires folding to be functional. It is a valid hypothesis to say solubility and foldability are necessary criteria. Then they tested it and found based on these criteria, the current set of amino acids is favored over other sets. Look like good science to me.
- yyyk 4y ago
  >It is a valid hypothesis to say solubility and foldability are necessary criteria. Necessary criteria for life, yes. Is it neccesary for evolution? The article's argument is that amino acids 'evolved'. Evolution needs a selection mechanism, and the article does not explain why evolution would favour solubility and foldability, so the article* doesn't come close to proving evolution happened much less explaining its details. Perhaps some other unexplained chemical process favoured these acids, or it was an accident. It's like looking at current status of biosphere, and concluding that life optimizes for insectoids because insects have the largest biomass. It's just an argument that assumes the result. * Perhaps the article is bad reporting and the reported study had an actual argument for this.
  - galaxytachyon 4y ago
    I see, the actual scientific paper is always a much better source for this stuff than a popsci article. The term "evolution" was used very loosely in the salon article. By your standard it would be more appropriate to call the process "selection". The amino acids never changes or evolved to become anything different, just that some were chosen to become the building blocks of life while others were ignored. The reasons for this selection were likely the two criteria mentioned above and that was backed up by the main study. You will notice I never used "evolution" to describe the process in my posts. I skipped the salon article entirely and only used the link they provided to read the real study so I didn't notice what they said in the salon page. Anyway, it is just some semantic stuff.
    - yyyk 4y ago
      Right, so I read the study instead of the article. Good idea. It's simply that the popsci article claims something that isn't the original study. The article does argue for evolution before life[0], and the study doesn't claim that at all. Either Salon simply misunderstood the study, or spiced it up so that aggregators like HN would pick it up. [0] "So by testing which libraries had the best solubility and structure, the researchers could conclude that proteins were evolving and driving natural selection before even forming living things."