From: bivalve (email@example.com)
Date: Mon May 12 2003 - 15:12:45 EDT
Addressing several specific points from various messages...
One basic issue is what exactly is the question. Claims that ID in the interventionist sense is proven, highly probable, likely, unlikely but worth pursuing, improbable, impossible to address, wrong, widely misused, or inherently flawed all have different criteria and levels of proof necessary to be credible. I think to some degree we are talking past each other in this regard.
I see the general search for intervention-style design within physical creation as theologically and scientifically unlikely to be productive, but neither impossible nor worthless to pursue.
The current ID movement seems theologically and scientifically ill-defined, and often too quick to assert proof for their ideas or difficulty for conventional evolutionary explanations. I am also concerned with the failure to clearly identify ID as an idea (as opposed to THE idea) about how God has worked in creation.
>(Irreducibly complex, in my definition, means: "requiring several coordinated changes to make any improvement")<
I appreciate the definition; it is necessary for a meaningful discussion of irreducible complexity. However, it does raise some further questions:
How do you define improvement? How coordinated must the changes be? How many? What counts as separate changes?
Note that, in evolving an entirely new function, the probability of a significantly negative mutation (defined in regard to said new function) is very low. The function is already absent, so the only way a mutation is going to have much impact is if something that were close to developing the new function received a severe setback. Even when a function first begins to emerge, the number of potential mutations conferring a substantial improvement is high. As a function becomes better developed, the proportion of possible substantial improvements decreases. However, numerous minor improvements, minor decreases in functionality, and neutral variations remain as possibilities. The number of potential positive mutations is still fairly high, but the number of substantial positive mutations has become low. Major negative mutations remain a possibility, but they also promote high risk of elimination from the gene pool. Strongly positive mutations will tend to spread quickly !
in a population; strongly negative ones will tend to disappear quickly.
A couple of factors that confound probability calculations are the presence of multiple adequate solutions and the requirement of mere adequacy, not absolute optimization. The level of competition is an important factor. For commercial engineering, competition is likely to be intense, and the problem relatively narrowly defined. In this case, a very specific maximum is desirable. In biological systems, the level of competition is variable, and the complexity of the demands faced by an organism make total focus on optimizing a particular function likely to prove costly in another function.
>The problem is that any mutation is just as likely to be UN-done as it is to occur, while it is waiting for all the others to occur. Imagine that you were collecting coupon cards (like you used to get in packets of tea or cigarettes). But suppose you had the rule that if you got a duplicate of one you already had, that you had to destroy both of them & wait for another one. Then it's relatively straightforward to show that the expected time you have to wait to get the whole collection rises exponentially with the size of the collection.<
However, in biological systems, getting a duplicate usually means you can start a new collection. The high level of parallelism also means there are plenty of backup copies.
>One can just as easily imagine that all combinatorial interactions of gene products generates important barriers to system function as one can imagine that all the combinatorial interactions are favorable and produce further functionality. There may be a billion fold increase of interactions that are completely destructive with respect to function compared with those that increase function in biology.<
This argument seems valid to me if it is taken no further than “not proven in either direction.” However, the fact that organisms exist shows that there are productive combinatorial interactions of gene products. Likewise, excess DNA only seems to be a problem if it gets to the point of taking too long to copy. The level of genetic regulatory ability plays a factor in determining how much additional DNA sequence is potentially functionally useful (not counting being raw material for further evolution). Thus, I do not think it is very likely that negative interactions are especially common relative to positive ones, though neutral (and thus not remarkably fruitful) interactions may be a major chunk of the possibilities.
>I suppose that doesn't answer the question as to how sexual reproduction itself evolved, which itself is an enormously complex process. I guess you have to explain how that complexity emerged without crossover.<
Two things to note:
Sex (defined as exchange of genetic information) is not necessarily linked to reproduction. Bacteria can readily take up DNA from their environment, and several strains have specific abilities to transfer a copy of their DNA to another individual. Thus, the DNA gets shuffled around, but reproduction itself is simply clonal cell division.
Secondly, sexual reproduction can occur relatively simply. Many one-celled organisms can fuse and then split apart again, allowing for DNA mixing during the time of fusion. Increasingly sophisticated patterns can be found in more complex organisms. A good example is seen in the volvocine series, a group of green algae including Volvox, which show progressive development of multicellularity and specialization of cells.
Dr. David Campbell
University of Alabama
Biodiversity & Systematics
Dept. Biological Sciences
Tuscaloosa, AL 35487-0345 USA
That is Uncle Joe, taken in the masonic regalia of a Grand Exalted Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at Droitgate Spa
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