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Don't basically all genetic algorithms rely on "random chance," or some simulation of random chance, to simulate a mutation rate? And haven't biologists, in re

by tps5 10y ago

Don't basically all genetic algorithms rely on "random chance," or some simulation of random chance, to simulate a mutation rate? And haven't biologists, in recent years, emphasized the degree to which evolution relies on mutations and genetic drift? That was my understanding of the way the field has been going, anyway. Saying that evolution as a whole is just "random chance" seems reductionist, but randomness does appear to be involved.

gipp 10y ago
Certainly randomness is _involved_, but it is randomness governed by a decidedly non-random fitness function. Without fitness there is no evolution. The problem arises because when biologists, statisticians etc say "random process," they mean something very specific that can actually contain many different kinds of mathematical structure, but your average layman hears that term to mean "¯\_(ツ)_/¯"
semi-extrinsic 10y ago
Consider throwing 20 dice. It is certainly a random process. And we know the odds for throwing 20 sixes is about one to 30 000 trillion, so you'd have to keep throwing dice for about as long as the Earth has existed to get that result. But if you start throwing the dice and you keep all the sixes you get along the way, Yahtzee-style, we expect you'll have 20 sixes in about 25-30 throws. In the latter case, external selection has turned an incredibly implausible result into a certainty.
- tps5 10y ago
  I don't agree with this analogy though. Who's to say if life evolved on earth all over again, we'd end up in the exact same place? Sure, some of the same adaptations would re-emerge. But some might not. And there might be extraneous mutations that had no effect on fitness at all but drastically changed the appearance of some subset of species. If we assume true randomness is involved then we assume evolution itself is going to deliver non-deterministic results, don't we? To put it in terms of genetic algorithms, we could run through N generations M different times and get different results each time. To me that makes it seem like saying "randomness is an important aspect of evolution" isn't so far from the mark.
  - gipp 10y ago
    We absolutely wouldn't end up in the same place, simply because the state space of possible organisms and environments is astronomically larger than the space of possible dice rolls (his metaphor isn't perfect and I'm already straining it here). But we would be almost guaranteed to end up with organisms that have similar levels of complexity. Again, randomness is an important part of evolution, but there are also necessary deterministic aspects of it that make the "blind watchmaker" type arguments that started this discussion irrelevant.
    - PetoU 10y ago
      according to https://en.m.wikipedia.org/wiki/Evolution_of_biological_complexity https://en.m.wikipedia.org/wiki/Evolution_of_biological_comp... Complexity argument is not valid. It's debatable at least. AFAIK it's part of the bigger discussion whether evolution has direction.
    - sirclueless 10y ago
      The basic argument made by the "random chance" commenter was not that evolution is a random process, but that it favors organisms with complex and interdependent gene expression, because this increases the rate at which random mutations cause differentiation.
- kirse 10y ago
  But if you start throwing the dice and you keep all the sixes you get along the way, Yahtzee-style, we expect you'll have 20 sixes in about 25-30 throws. But this scenario has the implicit assumption of a deterministic outcome (all 6s), and also that after each throw, the outcome of chance is being analyzed according to a set of rules, which are being applied such that keeping/discarding dice is done to produce a deterministic outcome. Even if you deny that there is traditional "intelligence" in the process such as a dice thrower, the scenario still fails to answer why there is even a set of rules for evaluating these independent dice throws in the first place, where these rules came from, and why those rules seemingly guide events of completely random chance in a pre-determined direction at all (all 6s).
  - 0xcde4c3db 10y ago
    The choice of a predetermined goal and an unchanging, deterministic selection function are just simplifying assumptions to make the analogy easier. Neither of those things is required for evolutionary processes to occur.
    - kirse 10y ago
      Neither of those things is required for evolutionary processes to occur. "Evolution works like a Yahtzee dice game minus all the Yahtzee rules"... How does that make sense? "Chess works like checkers except you remove all the checkers rules and just play chess"
      - 0xcde4c3db 10y ago
        The key points are: 1) the process is iterative, not a single "roll" that has to turn out right 2) each generation is a modification of the previous one, not a completely new "roll" 3) some states more likely to progress to the next generation than others We occur in an environment where these conditions are satisfied. Why that is the case is a question well beyond the scope of evolutionary theory.

by tps5 10y ago

gipp 10y ago

Certainly randomness is _involved_, but it is randomness governed by a decidedly non-random fitness function. Without fitness there is no evolution. The problem arises because when biologists, statisticians etc say "random process," they mean something very specific that can actually contain many different kinds of mathematical structure, but your average layman hears that term to mean "¯\_(ツ)_/¯"

semi-extrinsic 10y ago

Consider throwing 20 dice. It is certainly a random process. And we know the odds for throwing 20 sixes is about one to 30 000 trillion, so you'd have to keep throwing dice for about as long as the Earth has existed to get that result. But if you start throwing the dice and you keep all the sixes you get along the way, Yahtzee-style, we expect you'll have 20 sixes in about 25-30 throws. In the latter case, external selection has turned an incredibly implausible result into a certainty.

tps5 10y ago
I don't agree with this analogy though. Who's to say if life evolved on earth all over again, we'd end up in the exact same place? Sure, some of the same adaptations would re-emerge. But some might not. And there might be extraneous mutations that had no effect on fitness at all but drastically changed the appearance of some subset of species. If we assume true randomness is involved then we assume evolution itself is going to deliver non-deterministic results, don't we? To put it in terms of genetic algorithms, we could run through N generations M different times and get different results each time. To me that makes it seem like saying "randomness is an important aspect of evolution" isn't so far from the mark.
- gipp 10y ago
  We absolutely wouldn't end up in the same place, simply because the state space of possible organisms and environments is astronomically larger than the space of possible dice rolls (his metaphor isn't perfect and I'm already straining it here). But we would be almost guaranteed to end up with organisms that have similar levels of complexity. Again, randomness is an important part of evolution, but there are also necessary deterministic aspects of it that make the "blind watchmaker" type arguments that started this discussion irrelevant.
  - PetoU 10y ago
    according to https://en.m.wikipedia.org/wiki/Evolution_of_biological_complexity https://en.m.wikipedia.org/wiki/Evolution_of_biological_comp... Complexity argument is not valid. It's debatable at least. AFAIK it's part of the bigger discussion whether evolution has direction.
  - sirclueless 10y ago
    The basic argument made by the "random chance" commenter was not that evolution is a random process, but that it favors organisms with complex and interdependent gene expression, because this increases the rate at which random mutations cause differentiation.
kirse 10y ago
But if you start throwing the dice and you keep all the sixes you get along the way, Yahtzee-style, we expect you'll have 20 sixes in about 25-30 throws. But this scenario has the implicit assumption of a deterministic outcome (all 6s), and also that after each throw, the outcome of chance is being analyzed according to a set of rules, which are being applied such that keeping/discarding dice is done to produce a deterministic outcome. Even if you deny that there is traditional "intelligence" in the process such as a dice thrower, the scenario still fails to answer why there is even a set of rules for evaluating these independent dice throws in the first place, where these rules came from, and why those rules seemingly guide events of completely random chance in a pre-determined direction at all (all 6s).
- 0xcde4c3db 10y ago
  The choice of a predetermined goal and an unchanging, deterministic selection function are just simplifying assumptions to make the analogy easier. Neither of those things is required for evolutionary processes to occur.
  - kirse 10y ago
    Neither of those things is required for evolutionary processes to occur. "Evolution works like a Yahtzee dice game minus all the Yahtzee rules"... How does that make sense? "Chess works like checkers except you remove all the checkers rules and just play chess"
    - 0xcde4c3db 10y ago
      The key points are: 1) the process is iterative, not a single "roll" that has to turn out right 2) each generation is a modification of the previous one, not a completely new "roll" 3) some states more likely to progress to the next generation than others We occur in an environment where these conditions are satisfied. Why that is the case is a question well beyond the scope of evolutionary theory.