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  Topic: Co-option/change of function, Citations of this in the literature< Next Oldest | Next Newest >  
niiicholas



Posts: 319
Joined: May 2002

(Permalink) Posted: Mar. 29 2003,17:43   

A recent post of mine that I rather like:

(follows some discussion of eye evolution)


Topic: Distinguishing Mechanisms of Co-option, started by John Bracht

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John writes,

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This is the question I am trying to get at in this thread: how do we know that Darwinian co-option events really occurred by a non-intelligent mechanism? My experience is that there is no "test" that Darwinian thinkers apply to co-option events; rather they simply look at protein similarities and use that as "evidence" for their view. My point is that a design-driven co-option event would look exactly the same from our vantage point and hence the Darwinian comparison-of-similarity approach doesn't really test different mechanisms that might have been responsible for a given system.


This is the problem with the "vague designer" hypothesis -- an uncharacterized designer could, for all we know, do things however the heck he wants.  The "vague designer" hypothesis can "explain" not only observations supporting standard evolutionary biology but also any other set of observations.

Darwin had a similar problem: once he had convinced someone that the special creation "poof" model was untenable, a common response was to retreat to a vaguer position such as "the plan of Creation" or whatnot.  There are some great Darwin quotes somewhere on just how scientifically useless such statements are, unfortunately I can only find one at the moment:

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It is so easy to hide our ignorance under such expressions as the “plan of creation,” “unity of design,” &c., and to think that we give an explanation when we only restate a fact. (OoS)


To get a little more specific, consider one major difference between human intelligent design and "design" as seen in biology.  Human designs -- such as transistors, computers, radios, plastics, GPS systems, etc., etc., -- get invented in one place and then transplanted wholesale into a multiude of other "lineages" -- cars, boats, planes, rockets, etc.  In biology, on the other hand, the transmittance of designs through lineages appears to be strictly limited to that allowed by known processes of heredity, namely:

1) Lineal descent (parents to children, species to descendent species).  This is the major one.

2) or, sometimes, lateral gene transfer (although this seems to be limited to fairly simple systems that can fit on plasmids and subject to a number of other constraints, e.g. rare in things like metazoans with protected germline cells).

In other words, in human design you see an invention originate and then get basically simultaneously integrated across a wide range of "lineages".  In biological design the invention sits in whatever lineage it originated in (small groups of genes on mobile genetic elements being the exception, with a known and observed natural mechanism).

The fact that putative instances of cooption (the "same" structure being used for different functions) appear to follow the above pattern to a tee seems to me to be a perfect example of John's request regarding:

Quote
how do we know that Darwinian co-option events really occurred by a non-intelligent mechanism?


There is no reason for us to expect a designer to constrain design-transmittance to the processes of heredity; and yet we see such constraints, as we would expect based on common descent (= the continous operation of everday heredity).

However, a typical response that I've seen is to invoke front-loading, or "maybe the designer constrained himself to work within lineages for some reason", or "the designer might work in mysterious ways", or some other backup defense in order to save design from the falsification given in the above argument.  And this gets us back to Darwin's point about how vague designer-talk is scientifically vacuous and actually does no explaining at all.

In summary, you need at least a somewhat specific model of the designer (this does *not* require foreknowledge, just like any proposed hypothesis does not require foreknowledge) in order to have something with scientific tractability.  If ID stays in the "vague" category -- then it will never rise above the level of other such vague ideas ("an immaterial innate force causes design").

yersinia

PS: Another similar test is that:

1) Evolved cooptions will always have the "purpose" of increasing the reproduction of the genes of the organism carrying the new adaptation, but

2) There is no reason to expect such from IDed cooptions, indeed in human designs the designs are always meant to serve the purposes of the designer.

This is also, IMO, a good test, but again the IDist can escape by post-hoc appeals to a designer that mimics evolution for some reason.  In doing so they escape the frying pan of falsification but fall into the fire of scientific vacuousness.
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Edited by niiicholas on Mar. 29 2003,17:49

  
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