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Conversely, after the millions of years of evolution, it's not unreasonable to think that creating a more efficient Rubisco could have happened spontaneously in

Conversely, after the millions of years of evolution, it's not unreasonable to think that creating a more efficient Rubisco could have happened spontaneously in nature by mutation. Our logic suggests this would almost certainly provide some benefit; and yet, nearly all Rubisco enzymes show roughly the same level of efficiency. To me, this implies some other limiting factor that we don't understand.

ben_w 7y ago
There’s lots of stuff we don’t understand, but our ignorance isn’t necessarily the reason evolution didn’t do it. I expect us to find out why evolution didn’t do it by doing it to the plant genome ourselves — and that either it requires too many simultaneous changes for evolution, and/or it turns the plant into something irresistible to insects or fungi.
- lm28469 7y ago
  I'm sure there are many many more scenarios than the ones you listed. We're talking about editing the very thing that permitted life on earth, not renaming YourVarName to your_var_name across a codebase ...
samatman 7y ago
Highly multivariate random walks are excellent at finding local optima, and poor at descending from those hills to find a higher one. If something requires, say, five individually-deleterious mutations, each of low probability, it's quite plausible that these will never align in a single organism.
- sdenton4 7y ago
  A localized entity responsible for the inefficiency doesn't sound like a local minimum, though. It sound like a place where you should (eventually through mutation) find the more efficient path. There may be a more esoteric explanation... Imagine higher efficiency has a price : plant lives a shorter life, and reproduces less. Then you want to fine tune for the right amount of efficiency in your environment. Then it's advantageous to have a single efficiency lever, instead of a dozen systems to fine tune jointly... Just a guess - I know nothing about bio. :)
  - samatman 7y ago
    That is approximately why C4 photosynthesis hasn't swept the field and replaced C3 entirely: it's an advantage in high-light, dry conditions, whereas in wet, dark conditions, the more efficient use of ATP in C3 fixation provides a comparative advantage. FWIW I'm quite bullish on the type of research in the Fine Article; humans have the ability to provide choice conditions to our crops, and so we can maximize yield without (much) concern for the tradeoffs experienced in the state of nature. I'd predict, for example, that we'll have a C4 rice crop out of the lab and in the field in ten years or less.

ben_w 7y ago

There’s lots of stuff we don’t understand, but our ignorance isn’t necessarily the reason evolution didn’t do it. I expect us to find out why evolution didn’t do it by doing it to the plant genome ourselves — and that either it requires too many simultaneous changes for evolution, and/or it turns the plant into something irresistible to insects or fungi.

lm28469 7y ago
I'm sure there are many many more scenarios than the ones you listed. We're talking about editing the very thing that permitted life on earth, not renaming YourVarName to your_var_name across a codebase ...

samatman 7y ago

Highly multivariate random walks are excellent at finding local optima, and poor at descending from those hills to find a higher one. If something requires, say, five individually-deleterious mutations, each of low probability, it's quite plausible that these will never align in a single organism.

sdenton4 7y ago
A localized entity responsible for the inefficiency doesn't sound like a local minimum, though. It sound like a place where you should (eventually through mutation) find the more efficient path. There may be a more esoteric explanation... Imagine higher efficiency has a price : plant lives a shorter life, and reproduces less. Then you want to fine tune for the right amount of efficiency in your environment. Then it's advantageous to have a single efficiency lever, instead of a dozen systems to fine tune jointly... Just a guess - I know nothing about bio. :)
- samatman 7y ago
  That is approximately why C4 photosynthesis hasn't swept the field and replaced C3 entirely: it's an advantage in high-light, dry conditions, whereas in wet, dark conditions, the more efficient use of ATP in C3 fixation provides a comparative advantage. FWIW I'm quite bullish on the type of research in the Fine Article; humans have the ability to provide choice conditions to our crops, and so we can maximize yield without (much) concern for the tradeoffs experienced in the state of nature. I'd predict, for example, that we'll have a C4 rice crop out of the lab and in the field in ten years or less.