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Simon
SFN Regular
USA
1992 Posts |
Posted - 11/26/2008 : 10:25:56 [Permalink]
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Yeah; the occurrence of genetic mutations themselves is random.
However, its prevalence is high enough that after a number of generations, every possible mutations will have occurred.
So, if there is a 'single best mutation', it will happen sooner or later. Then, natural selection being deterministic, it will be selected upon.
That means that, on simple traits, any population in similar condition will evolve through the same paths.
The only difference is that in certain population, the mutation will occur sooner (it's called jackpot mutations) and in other later.
The rate of mutation itself, interestingly and logically enough, also is a selectable character. Which means that logically, for any given environment, there is a value that would gives an 'optimal fitness' between evolutionary innovation and translation errors.
Such a value was found for all groups of prokaryotic biology (bacteria, virus, bacteriophage...) that all display a similar mutation rate despite their huge differences.
Anyway, for more complex traits, that require multiple mutations, like in the case of Lenski's experiment, it probably works under similar conditions.
The real trick is when there is multiple, roughly equally valid, paths to fitness.
Then true randomness dominates. |
Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.
Carl Sagan - 1996 |
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filthy
SFN Die Hard
USA
14408 Posts |
 Posted - 11/26/2008 : 11:40:03 [Permalink]
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Speaking of Lenski, did he ever give in to the idiotic demands of the scientifically unqualified, theocratic twit, Andy Schlafly of Conservapedia? At last report he, Lenski, had basicly told him, Schlafly, to go piss in his hat. I haven't heard anything beyond that.
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist! 
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BigPapaSmurf
SFN Die Hard
3192 Posts |
Posted - 11/26/2008 : 12:17:34 [Permalink]
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Originally posted by Simon
Yeah; the occurrence of genetic mutations themselves is random.
However, its prevalence is high enough that after a number of generations, every possible mutations will have occurred.
So, if there is a 'single best mutation', it will happen sooner or later. Then, natural selection being deterministic, it will be selected upon.
That means that, on simple traits, any population in similar condition will evolve through the same paths.
The only difference is that in certain population, the mutation will occur sooner (it's called jackpot mutations) and in other later.
The rate of mutation itself, interestingly and logically enough, also is a selectable character. Which means that logically, for any given environment, there is a value that would gives an 'optimal fitness' between evolutionary innovation and translation errors.
Such a value was found for all groups of prokaryotic biology (bacteria, virus, bacteriophage...) that all display a similar mutation rate despite their huge differences.
Anyway, for more complex traits, that require multiple mutations, like in the case of Lenski's experiment, it probably works under similar conditions.
The real trick is when there is multiple, roughly equally valid, paths to fitness.
Then true randomness dominates.
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You may be able to get every possible mutation, if you have a fixed length for the chains and infinite time. So as they are limited by time and breeding rates for the duration of organism Xs species-lifespan all possible mutations will not occur. Even if the 'single best mutation within the local environment' occurs there are a mryiad of reasons why it might not stick. It may conflict with other mutations, food supplies/diet or breeding rituals for example. Also if an optimal mutation occurs and does 'stick', the inevitable change of envionmental conditions could make it useless or detrimental, also it may mutate away from this quasi-perfection in the long run even if conditions remain relatively stable. |
"...things I have neither seen nor experienced nor heard tell of from anybody else; things, what is more, that do not in fact exist and could not ever exist at all. So my readers must not believe a word I say." -Lucian on his book True History
"...They accept such things on faith alone, without any evidence. So if a fraudulent and cunning person who knows how to take advantage of a situation comes among them, he can make himself rich in a short time." -Lucian critical of early Christians c.166 AD From his book, De Morte Peregrini |
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Bathypelagic weirdness
