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#11
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Re: Selling Evolution
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Or, stated another way: Randomness is an illusion, but Tom’s ignorance is painfully real. |
#12
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Re: Selling Evolution
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What I really meant by "random" is that mutations occur without regard for their effect upon the adaptive design of organisms (with a few exceptions that prove the rule, but I won't go into them). In other words, mutational processes that inherently benefit organisms don't exist, and most mutations decrease an organism's ability to produce offspring. You could also think of mutation as a process that continually pushes populations toward higher entropy . . . without a complementary process that reduced entropy locally, mutation would result in lower and lower organismal fitness until the population crashed to extinction. This is one of the primary concerns with respect to very small, endangered species, in which selection cannot act strongly enough to combat mutational meltdown. Natural selection is the complementary process that siphons and preserves order from a pool of mutational disorder . . . organisms that are best adapted to their environments preferentially contribute to subsequent generations, while less effectively-adapted organisms fail to contirbute or contribute less heritable information to subsequent generations (as you may intuit, the difference between the conitrbutions of more-fit and less-fit organisms is directly related to the strength of selection, as described by the mathematics of evolutionary genetics). Deleterious mutations are thus expunged from the population . . . to what extent this occurs depends upon the strength of selection, population size, mutation rate, reproductive mechanism of the species in question (sexual, asexual, etc.) and, in some contexts, immigration/emmigration rates. The details of why certain organisms and traits are more or less "fit" are highly context-dependent; e.g. a lizard that specializes upon swimming and consuming seaweed can do very well in a marine tidal habitat, but the same lizard is pretty screwed in a desert. So, to re-iterate my meaning: mutations may in principle be governed by deterministic laws, but they don't preferentially benefit organisms or rain down according to a grand design. Rather, mutation is the process that drives populations toward the thermodynamic equivalent of entropy, and natural selection is the process that ultimately resists localized entropy (while allowing universal entropy to increase by the release of metabolic heat, etc.) Last edited by Carey N; August 1st, 2006 at 12:04 PM.. |
#13
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Re: Selling Evolution
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Anyhoo, it seems that we agree that mutation isn’t necessarily intrinsically “random,†but rather, currently, it seems to be unpredictable, at least by us humans based on our current knowledge. Roger Penrose (in his Emperor’s New Mind), who convincingly argues that human mathematical insight is non-algorithmic, and also doesn’t see how algorithms for mathematical judgment could evolve, writes: "To my way of thinking, there is still something mysterious about evolution, with its apparent 'groping' towards some future purpose. Things at least seem to organize themselves somewhat better than they 'ought' to, just on the basis of blind-chance evolution and natural selection." (p.416). (And others have said similar things.) |
#14
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Re: Selling Evolution
Thanks for the positive feedback. I'm afraid this one's going to be a bit more long-winded. Bear with me.
Some comments on your comments: Quote:
This is why I said that, in practice, mutations are not predictable - at least, not by humans. Perhaps I'm incorrect on that matter, but I'm willing to bet that a formal analysis would yield the same qualitative conclusion. Could Someone else predict all mutations? I guess so, but He'd have to be beyond the material realm of this universe, beyond the rules of physics . . . beyond human commentary. Such an entity's existence would not be subject to rational argument. Quote:
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My correction for Penrose is this: evolution doesn't grope towards any kind of purpose other than increased capacity to populate the biota with copies of oneself. It may appear that evolution has been ascending a ladder of progress*, if one takes a highly anthropocentric view of the big picture, but consider that single-celled oarganisms are still the most abundant (in numbers and biomass), by a long shot, on earth. The only thing evolution does is pull a few pockets of order out of a large pool of mutational disorder (the reason why I can say mutational disorder is that mutations are effectively random with respect to their effects upon the adaptive design of organisms, as discussed in my last post). What else could be expected of a dumb algorithm? The amazing thing is the sheer complexity of organisms that have arisen from this process, which itself lacks any foresight. So . . . I think there is quite a lot of mystery awaiting resolution in evolutionary biology, but none of that mystery (to me) suggests, hints, leans toward, or in any way implies the existence of a grand design. ------------------------------------------------------------------------------------- * What does "progress" even mean in this context? If it means greater complexity, then humans are certainly a step forward. But defining progress in that way is really a human-induced artificiality. For evolution, progress is just the continuation of existence, in any self-reproducing form (bacteria, insects, plants, humans, whatever). |
#15
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Re: Selling Evolution
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Which leaves us pretty much where we were back in the June 17 2006 post, Re: Implications of Somatic Behavior Choice, where you said: Quote:
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Last edited by Fred H.; August 1st, 2006 at 12:18 PM.. |
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Re: Selling Evolution
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#17
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Re: Selling Evolution
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Last edited by Carey N; August 2nd, 2006 at 08:18 AM.. |
#18
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Re: Selling Evolution
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http://www.behavior.net/bolforums/sh...90&postcount=4 — Quote:
So I don’t think it sounds like Penrose is necessarily saying, as you opine, that he "can't possibly believe that natural selection, lacking any foresight, produced biological complexity." Rather I think he’s saying exactly what he said: "To my way of thinking, there is still something mysterious about evolution, with its apparent 'groping' towards some future purpose. Things at least seem to organize themselves somewhat better than they 'ought' to, just on the basis of blind-chance evolution and natural selection." And I’d add that while Penrose indicates that he himself is a strong believer in “natural selection,†I suspect that he, like me, may also see “natural selection,†whether it be a top down or bottom up selection, as ultimately little more than a circular account that really doesn’t explain or predict all that much. Last edited by Fred H.; August 2nd, 2006 at 10:05 AM.. |
#19
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Re: Selling Evolution
Watching this one form the sidelines I see that Fred states that selection proceeds:
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The theory of evolution is the scientific description of a process, a mechanism, whereby species can change over time to adapt to their environment - which is also changing randomly (unpredictably at the level of the organism). A mechanism, whether natural or man-made can have many elements working together to provide a function. That one element of the mechanism uses the quality of randomness to provide a source of information that is used by other elements of the process - does not make the process random. This seems to me similar to a random number generator in a computer game - such as when dealing the deck in free cell. Depending on the deal sometimes the player may win, sometimes they lose. Much like mutations sometimes enhance fitness and sometimes reduce fitness. Since an organism has no way of knowing ahead of time which ones will do better, or just how their environment might change around them, the effective randomness of mutations allows whatever possible designs that come up - to be tried out in the game of life - in the existing unpredictable environment. Since environments themselves are effectively random at the level of the organism (volcanoes, hurricanes, CO2 concentrations, migration of predators, disease organisms, etc.) what better way could be devised for species to adapt than for each generation to be able to select the best possibilities from a random set. The result is that species evolve in a very non-random way - always in a way to optimize their survival in their existing environment. The randomness of mutations provides a crucial type of information that allows non-random evolution to proceed - to track a randomly changing environment. I don't offer this as a better explanation than Carey's. More to see if I've got it right so please tell me if I don't. BTW Carey, I really appreciated your explanation of evolution in terms of thermodynamics. I've never seen that done so clearly. Margaret |
#20
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Re: Selling Evolution
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(I’m so glad MM is on your side.) |
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