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Author Topic:   An ID hypothesis: Front-loaded Evolution
PaulK
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Message 12 of 216 (653243)
02-19-2012 2:16 PM
Reply to: Message 1 by Genomicus
02-19-2012 5:43 AM


The obvious problem with front-loading
Unless preserved by selection the genome can be changed by mutation at a relatively rapid rate. Any "front-loaded" information that isn't actually in use is unlikely to be preserved unchanged for long enough to become useful.

This message is a reply to:
 Message 1 by Genomicus, posted 02-19-2012 5:43 AM Genomicus has replied

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PaulK
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Posts: 17171
Joined: 01-10-2003
Member Rating: 2.5


Message 68 of 216 (653471)
02-21-2012 2:47 PM
Reply to: Message 67 by Dr Adequate
02-21-2012 2:15 PM


Re: Some Objections
quote:

One usual case made against front-loading is that while a gene was waiting to become useful, it would be turned into nonsense by genetic drift. I note with pleasure that you have proposed that these genes would be doing something else useful until they were converted to different genes by some pre-programmed process.

There's another issue here, too. Selection will keep the genes adequate at performing their function in the life that currently exists. It will not protect them from changes which are neutral with regard to that function. "Front-loaded" information is still hard to protect even in this scenario.


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PaulK
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Posts: 17171
Joined: 01-10-2003
Member Rating: 2.5


Message 118 of 216 (653740)
02-24-2012 2:20 AM
Reply to: Message 107 by Genomicus
02-23-2012 10:27 PM


Re: General Response to Objections
quote:

I’d like to point out that the argument “I can’t imagine how the eye could have been front-loaded, therefore it could not have been” isn’t really all that valid.

It was valid enough that Darwin thought it to be worth answering. The usual problem is that creationists quote the argument but ignore the response, giving a deeply misleading impression of what Darwin was saying.

I think that recognising the problems with front-loading, even if they are expressed a little vaguely is an important part of this discussion.

quote:

It’s also important to understand something here: front-loading does not necessarily entail directly front-loading something like the eye. Front-loading is “stacking the deck” (to borrow from Mike Gene) such that the evolution of certain features becomes much more plausible. For example, if we design rhodopsin in a bacterial genome, we could predict that when eyes evolve, rhodopsin will be used.

Now this is where we see problems with your arguments.

Does designing rhodopsin into the first life significantly increase the chance of eyes evolving ? Nothing you say really addresses this point. You say it does, but it really isn't clear why you think that.

Can we really say that rhodopsin specifically would be used ? It's available for co-option, sure, but is it the only possibility ? How likely is it to be the only possibility or even the most available option when eyes do evolve ? We do need to be careful to avoid thinking that the way things work now is the only possible way, especially in the context of this discussion since it would bias the argument in favour of front-loading.

According to Wikipedia (not the best source, I know but usually OK on science and more accessible to the lay public) bacterial rhodopsins may have an evolutionary relationship with visual rhodopsins, but they may not. Doesn't this make it a rather poor example of possible "front-loading" ?


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 Message 107 by Genomicus, posted 02-23-2012 10:27 PM Genomicus has replied

Replies to this message:
 Message 131 by Genomicus, posted 02-24-2012 4:55 AM PaulK has replied

  
PaulK
Member
Posts: 17171
Joined: 01-10-2003
Member Rating: 2.5


Message 138 of 216 (653769)
02-24-2012 5:16 AM
Reply to: Message 131 by Genomicus
02-24-2012 4:55 AM


Re: General Response to Objections
quote:

See my response to Dr Adequate, above.

I can't see a relevant response.

quote:

Rhodopsin would be available for co-option, but would it be the only possibility? Possibly the blind watchmaker would "generate" a protein that would then be co-opted into a vision-related function. But this would be an extra step: the blind watchmaker would have to duplicate an existing gene, modify it such that its function is compatible with a vision system, and then it'd be co-opted. These extra steps make it less likely for the eye to evolve in the absence of front-loading.

I think we have to eliminate the argument that it is easier for a hypothetical designer to produce a working single-called organism than it is for evolution. That really isn't the point under discussion.

The real issue is whether building in a rhodopsin homolog makes it significantly more likely for eyes to evolve when compared with an alternative organism produced solely by evolution. Remembering that we can't rely on any part of the gene surviving other than those parts essential for function it isn't at all clear that front-loading offers much help. You NEED a strong overlap between the function and usefulness for vision for the argument to work, but you also need this overlap to be specific to rhodopsin. If the overlap is a direct consequence of function - a point that you haven't addressed - then alternatives to rhodopsin would likely have the same usefulness, and there would be no need for any more evolution in that case, either.

quote:

From Wikipedia:
"Bacteriorhodopsin belongs to a family of bacterial proteins related to vertebrate rhodopsins, the pigments that sense light in the retina." (Emphasis added)

Wikipedia disagreeing with itself would support my point of uncertainty, so this quote doesn't really help (even if it does mean an evolutionary relationship which isn't explicitly stated).


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