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Evolution is really good at getting to local optimas (solutions where there are no small changes that can lead to improvement) but really bad at finding global

Evolution is really good at getting to local optimas (solutions where there are no small changes that can lead to improvement) but really bad at finding global optimas (the absolute optimal system possible.) http://lesswrong.com/lw/kt/evolutions_are_stupid_but_work_anyway/ http://lesswrong.com/lw/kt/evolutions_are_stupid_but_work_an... >Humans can do things that evolutions probably can't do period over the expected lifetime of the universe. As the eminent biologist Cynthia Kenyon once put it at a dinner I had the honor of attending, "One grad student can do things in an hour that evolution could not do in a billion years." According to biologists' best current knowledge, evolutions have invented a fully rotating wheel on a grand total of three occasions.

tomlock 12y ago
The wheel isn't that great a transport mechanism when there aren't any roads! Additionally, machine learning models can get stuck in local optimas, too! I'm not very well versed in machine learning so I apologise if I get this wrong, but one solution to this I think is to randomly change the starting variables. This kind of thing does happen in nature, but it often doesn't work. Sometimes it does and that is when you get things like haploid versus diploid versions of the same plant. This is really insensitive, but when you see a person with chromosomal abnormalities or genetic defects, that's a random reset that has (probably) taken us out of our (maybe local) optima. Who knows though, maybe one of those leaps will take us to a global optima. The reason we aren't still on a planet of bacteria is that we did leap out of those local optima successfully. It just took a long time.
- Houshalter 12y ago
  >The wheel isn't that great a transport mechanism when there aren't any roads! Wheels are used in all kinds of machinery. Gears are basically wheels. >The reason we aren't still on a planet of bacteria is that we did leap out of those local optima successfully. It just took a long time. Bacteria still very much own the planet. >This is really insensitive, but when you see a person with chromosomal abnormalities or genetic defects, that's a random reset that has (probably) taken us out of our (maybe local) optima. Who knows though, maybe one of those leaps will take us to a global optima. No because the existing gene pool still exists. You need to completely start from scratch to have a chance to get out of local optima, not just have really big mutations.
  - nazgul17 12y ago
    As far as I understand, you do not need to completely start from scratch to get out of local optima: one individual is enough (at least in asexual reproduction) to drive a population shift. That is how bacteria develop immunities. I think that for sexual reproduction, leaps cannot be as big, but they can certainly happen and one individual with a mutation is enough. This brings me to mind an article I read recently about a study that found that all danish people with blue eyes share a common ancestor. It's not exactly the same thing, but I would argue that, if having blue eyes was an evolutionary advantage, we would all have blue eyes; and that started with a single mutated individual.
    - Houshalter 12y ago
      The point of a random restart is that you completely eliminate any bias and hopefully end up in an entirely different section of the search space (and it's far from a solution to local minima, it's just better than nothing.) If you just give a random organism a really big mutation, they still retain 99% of their genes and will tend towards the same solution space. They will almost certainly be outcompeted by the non-mutated members of the population. And even in bacteria, they will eventually trade genetics through horizontal gene transfer. Anyway the premise was that evolution is essentially magic and has reached the optimal solution for every task. This is just false. It's merely reached good local maximas where it can't easily improve through small changes. Human engineers are far better, evolution merely had a big head start.

tomlock 12y ago

The wheel isn't that great a transport mechanism when there aren't any roads! Additionally, machine learning models can get stuck in local optimas, too! I'm not very well versed in machine learning so I apologise if I get this wrong, but one solution to this I think is to randomly change the starting variables. This kind of thing does happen in nature, but it often doesn't work. Sometimes it does and that is when you get things like haploid versus diploid versions of the same plant. This is really insensitive, but when you see a person with chromosomal abnormalities or genetic defects, that's a random reset that has (probably) taken us out of our (maybe local) optima. Who knows though, maybe one of those leaps will take us to a global optima. The reason we aren't still on a planet of bacteria is that we did leap out of those local optima successfully. It just took a long time.

Houshalter 12y ago
>The wheel isn't that great a transport mechanism when there aren't any roads! Wheels are used in all kinds of machinery. Gears are basically wheels. >The reason we aren't still on a planet of bacteria is that we did leap out of those local optima successfully. It just took a long time. Bacteria still very much own the planet. >This is really insensitive, but when you see a person with chromosomal abnormalities or genetic defects, that's a random reset that has (probably) taken us out of our (maybe local) optima. Who knows though, maybe one of those leaps will take us to a global optima. No because the existing gene pool still exists. You need to completely start from scratch to have a chance to get out of local optima, not just have really big mutations.
- nazgul17 12y ago
  As far as I understand, you do not need to completely start from scratch to get out of local optima: one individual is enough (at least in asexual reproduction) to drive a population shift. That is how bacteria develop immunities. I think that for sexual reproduction, leaps cannot be as big, but they can certainly happen and one individual with a mutation is enough. This brings me to mind an article I read recently about a study that found that all danish people with blue eyes share a common ancestor. It's not exactly the same thing, but I would argue that, if having blue eyes was an evolutionary advantage, we would all have blue eyes; and that started with a single mutated individual.
  - Houshalter 12y ago
    The point of a random restart is that you completely eliminate any bias and hopefully end up in an entirely different section of the search space (and it's far from a solution to local minima, it's just better than nothing.) If you just give a random organism a really big mutation, they still retain 99% of their genes and will tend towards the same solution space. They will almost certainly be outcompeted by the non-mutated members of the population. And even in bacteria, they will eventually trade genetics through horizontal gene transfer. Anyway the premise was that evolution is essentially magic and has reached the optimal solution for every task. This is just false. It's merely reached good local maximas where it can't easily improve through small changes. Human engineers are far better, evolution merely had a big head start.