Wednesday, November 07, 2007

Very Few Get The Argument

Because they don't want to get it. But this guy does:


Just two comments:

1) Although you are right that a strict sequence comparison between actual parasite and the parasite as it was at the moment of the introduction of chloroquine is not possible, because the sequencing of the genome has only been completed now, still there is probably no evidence that any significant phenotypic difference has been observed to emerge in the parasite during those years.

2) But that is really not the point. The point is that, after the introduction of chloroquine, the main selective pressure in the so called “fitness landscape” has become the drug. So, we have a model where a very strong environmental challenge has emerged, which is exactly what is supposed to be a very strong motivation to evolution in a darwinian scenario. So, the point is not if the parasite in those years has started to evolve some occult difference, but rather why it has not evolved any complex and non trivial adaptation to chloroquine, in the presence of such a strong selective force, and with so many reproductive cycles available. Why not a “cloroquinase”, or some equivalent mechanism, for instance? Why not a complex new pathway, let’s say 3 or 4 proteins in cascade whose purpose could be to metabolize the drug, or to couple it to some molecule to make it ineffective. Why not new cellular functions which may allow the parasite’s survival in the presence of choroquine? Why not a deeply renovated parasite, much more dangerous and resistant than its ancestor?

There are many possible ways to adapt, exactly as darwinian theory postulates, in the presence of a very strong environmental selective pressure. According to the theory, that’s why new species arise, new body plans are formed, new brains and functions arise, and often in less reproductive cycles than the parasite has experienced in the few years fron the introduction of the drug.

So, Behe’s argument stays perfectly valid: why can’t we see any creative evolution in the parasite, when all the necessary ingredients are there? Why only few trivial single point mutations?

The answer is simple: because that’s all random variation can accomplish, in absence of a design implementation.

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