>If you just cut off half of a flagellum, you still have ALL the proteins required. But if you eliminate a gene specifying a given type of protein either of the rotor, or of the stator, or of the drive shaft, or of the flagellum, or of the hook linking them, or maybe any one of a few others, you won't have anything moving AT ALL. This may not be deadly to the bacterium (if it is in a nutrient broth), but it COMPLETELY eliminates the flagellum function. If, e.g., a crucial rotor protein is missing, a new "prospective" rotor protein certainly cannot be selected for (by some flagellar motion!) as long as it doesn't provide the missing function AT LEAST MINIMALLY. How did this minimal activity arise? To believe that it evolved from some other, similar sequence is a useless "just-so story". Do we have to prove that this evolution could NOT happen? Or do we have to show that it COULD? I don't know whether Behe would argue like this, nor how Dembski would estimate a probability for!
the flagellum case. But wouldn't the inference of irreducible complexity be the most reasonable one, given what we know at present?
>I agree with you that we cannot prove it. But at least we should admit that we cannot (yet?) conceive of any possible darwinian evolutionary path for the flagellum - and for 1001 other functions.
>For THEOLOGICAL reasons, on the other hand, I believe that we will never be able to scientifically prove intelligent design - which would necessarily imply the existence of a personal, intelligent, transcendent Designer - and lack of freedom for a faith decision on our part.
If the flagellum is useless without a given protein, the intermediate is nonetheless viable, albeit we do not yet know any reason for the intermediate to come into existence except for very low probability random events. Given what I know of our knowledge of biochemical systems, I do not think it is safe to draw any conclusions about the most reasonable explanation, except to note that some complex systems do have good evolutionary explanations (the halves of the Krebs cycle both being independently functional in some bacteria, for example).
Different theological considerations make me doubtful about expecting intellignet design. It is not the pattern of running creation that has been observed historically, and I do not see any theological reason to expect a different approach in the past. The Biblical use of miracles is for authentication of the claim of new revelation or of authority. The first cells needed neither.
Dr. David Campbell
Saint Mary's College of Maryland
18952 E. Fisher Road
St. Mary's City, MD 20686-3001 USA
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"Mollusks murmured 'Morning!'. And salmon chanted 'Evening!'."-Frank Muir, Oh My Word!
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