Behe asserts that new functions only arise through “purposeful design” of new genetic information, a claim that cannot be tested. By contrast, modern evolutionary theory provides a coherent set of processes—mutation, recombination, drift, and selection—that can be observed in the laboratory and modeled mathematically and are consistent with the fossil record and comparative genomics."
This is interesting because it illustrates a typical disingenuous response to anything that even hints at ID.
There is a
very close analogy between the genome and a book. Anyone who feels uncomfortable with scientific arguments will feel far more at home using this analogy. DNA is made up of 4 different chemicals, usually referred to by their first letters - C,G,T,A. These are analogous to letters in a book, but the analogy can be made closer because when DNA codes for a protein, those letters are taken 3 at a time, and some triples code for the same amino acid (basic protein component). A language composed of 20 letters (the number of different amino acid residues found in proteins) sounds pretty familiar, so we can apply some common sense.
Just like a book, the letters are grouped into sentences - say individual proteins.
Think of this book as a construction manual for an organism - say a human.
Now let's consider how the set of processes look in terms of the book analogy.
Mutation - this consists of randomly changing a letter in the book, or randomly deleting a portion of the book, or
randomly moving a portion of the book to another location. We aren't talking about whole chapters or even sentences, but a
randomly chosen block of letters!
Recombination - this is what sex is all about (if you don't use a contraceptive) - the two partners have very similar, but not identical books, and these are
randomly mingled to produce another book. This can produce offspring that combine certain good or bad features of the parents. Clearly natural selection can operate at that point because some offspring will do well in life while others may be burdened by disease. BTW not all organisms reproduce sexually.
Drift - this mechanism consists of
randomly changing letters in parts of the book that aren't important at the moment - perhaps the acknowledgements page, or bits of the book that describe bodily mechanisms that you may not need in modern life.
There is also a mechanism, whose name escapes me, whereby a random bit of text (DNA) is transferred from one organism to another, typically by a virus.
Selection - means what it says. Someone built out of a good book will (at least on average) outperform someone built from a faulty book.
Sexual selection - basically a variant of selection - ugly males or females don't reproduce as effectively as handsome ones.
OK, now remember that when Darwin came out with his theory, nobody knew anything about DNA, and genes were conceived of as rather simple 'objects'. When Darwin's theory is applied to the real mechanism, the problems are fairly obvious.
1) Mutations are almost always destructive. Picking a letter in a book at random and changing it, will almost invariably damage it, not enhance it. Above all this is because you would need a whole block of changes focussed on just one sentence to change the meaning of the sentence, as opposed to making it illegible - but these are coming randomly by hypothesis.
2) Other ways of mutating text (DNA) are also at heart random, so they aren't really any better. For example, genetic drift may happen, but what possible reason is there to expect the result to be useful?
Behe's argument, in book form, is that there is a way in which you might take a manual and improve it by a random change. For example, if people had to live through a famine, having super efficient legs for running might not be helpful. Damaging a sentence which meant that people had less powerful muscles but needed less food intake would help them to survive, and if the famine lasted long enough this mutation might spread. However, long term that makes it hard for humans to escape predators. The problem is, you can randomly damage a book, but the chance of damaging it again in such a way that it can restore function is vanishingly small.
Suppose you took a real manual (say for a car) and spewed out variants changed by any of those mechanisms. Would you really expect that you could pick out an improved manual and do the whole process again and again so as to evolve the car into an delux sports version?
Bart - I really hope you will plough your way through that so we can have a more meaningful discussion. Others here - feel free to suggest corrections, bearing in mind that I am not a biologist, and even my chemistry is stale by now.
David