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Author Topic:   Symphony by accident
slevesque
Member (Idle past 4670 days)
Posts: 1456
Joined: 05-14-2009


Message 5 of 23 (605671)
02-21-2011 2:44 PM
Reply to: Message 1 by nwr
02-21-2011 11:13 AM


But then, isn't the majority of mutations fixed through genetic drift ? (ie randomly)
If I'm not mistaken the number of mutations fixed by selection is quite small compared to genetic drift.

This message is a reply to:
 Message 1 by nwr, posted 02-21-2011 11:13 AM nwr has replied

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 Message 6 by New Cat's Eye, posted 02-21-2011 2:58 PM slevesque has not replied
 Message 7 by nwr, posted 02-21-2011 2:58 PM slevesque has replied
 Message 8 by Percy, posted 02-21-2011 3:06 PM slevesque has replied
 Message 9 by Dr Adequate, posted 02-21-2011 3:09 PM slevesque has not replied

  
slevesque
Member (Idle past 4670 days)
Posts: 1456
Joined: 05-14-2009


Message 10 of 23 (605679)
02-21-2011 3:14 PM
Reply to: Message 7 by nwr
02-21-2011 2:58 PM


My example of music was admittedly an extreme case, intended for emphasis. But the point is that you have randomness that is fed into a filter. In our normal way of talking, we don't use "accident" when there is a directional filter.
Yes, but the force of the filter must be proportionally as strong as the quantity of randomness flooding in.
Someone would still be justified to call it accidental if the filter only gives it a weak direction.

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 Message 7 by nwr, posted 02-21-2011 2:58 PM nwr has replied

Replies to this message:
 Message 13 by Dr Adequate, posted 02-21-2011 3:28 PM slevesque has replied
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slevesque
Member (Idle past 4670 days)
Posts: 1456
Joined: 05-14-2009


Message 12 of 23 (605686)
02-21-2011 3:22 PM
Reply to: Message 8 by Percy
02-21-2011 3:06 PM


It seems unlikely to me that there exists a way to count actual fixated mutations and classify them as to whether it was due to selection or drift, so I don't think we could know either way whether what you're claiming is true. Maybe one of the biologists will chime in.
Population genetics gives us a maximum on fixation by selection, since selection involves killing/inhibiting reproduction of individuals. So it can only select for so much in a given generation, all the rest is hope to genetic drift.
We do know that advantageous alleles will be driven toward fixation more rapidly than neutral alleles, but as fixation approaches the effects of drift become more prominent and can actually interfere with fixation. Apparently, in sexual populations recessive advantageous alleles can actually have a better chance of fixation than dominate advantageous alleles simply because of the effects of drift. See Natural Selection, Genetic Drift, and Gene Flow Do Not Act in Isolation in Natural Populations.
And if genetic drift has such on a strong effect on the fixation of mutations, wouldn't one be justified to question if such an amount of randomness can still account for the evolution of complex structures ?

This message is a reply to:
 Message 8 by Percy, posted 02-21-2011 3:06 PM Percy has replied

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 Message 16 by Percy, posted 02-21-2011 3:54 PM slevesque has replied
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slevesque
Member (Idle past 4670 days)
Posts: 1456
Joined: 05-14-2009


Message 14 of 23 (605693)
02-21-2011 3:47 PM
Reply to: Message 13 by Dr Adequate
02-21-2011 3:28 PM


Well, again, the topic was the eye, and whether Richard Dawkins thinks it happened "by accident". Clearly he thinks that the filter of selection is strong enough to produce the eye; consequently, he does not think that the eye is accidental.
I hear you, but your changing the goalpost. My remark was concerning Nwr's OP, which in turn was in reply to Bolder-dash's statement that evolution as a whole is a random process.

This message is a reply to:
 Message 13 by Dr Adequate, posted 02-21-2011 3:28 PM Dr Adequate has replied

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slevesque
Member (Idle past 4670 days)
Posts: 1456
Joined: 05-14-2009


Message 19 of 23 (605703)
02-21-2011 4:14 PM
Reply to: Message 16 by Percy
02-21-2011 3:54 PM


I think you must be operating under the impression that advantageous mutations that do not reach fixation are somehow lost, which is definitely not the case. It also appears possible that you think fixation is some kind of holy grail for alleles, and that alleles that do not attain fixation do not have a significant impact on a population, also definitely not the case.
No, but when discussing evolution, fixation is quite important. After all, we compare the fixed mutations between species to extrapolate common ancestors.
In the long run, only the fixed mutations will have a permanent impact. Temporary impacts from mutations that come and go through drift isn't relevant.
A population, or sub-population, evolves through fixation.

This message is a reply to:
 Message 16 by Percy, posted 02-21-2011 3:54 PM Percy has replied

Replies to this message:
 Message 20 by Percy, posted 02-21-2011 8:36 PM slevesque has not replied

  
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