Wednesday, October 10, 2007

All that Darwinism can do?

...the E. coli work has pointed in the same general direction. The lab bacteria performed much like the wild pathogens: A host of incoherent changes have slightly altered pre-existing systems. Nothing fundamentally new has been produced. No new protein-protein interactions, no new molecular machines. As with thalassemia in humans, some large evolutionary advantages have been conferred by breaking things. Several populations of bacteria lost their ability to repair DNA. One of the most beneficial mutations, seen repeatedly in separate cultures, was the bacterium’s loss of the ability to make a sugar called ribose, which is a component of RNA. Another was a change in a regulatory gene called spoT, which affected en masse how fifty-nine other genes work, either increasing or decreasing their activity. One likely explanation for the net good effect of this very blunt mutation is that it turned off the energetically costly genes that make the bacterial flagellum, saving the cell some energy. Breaking some genes and turning others off, however, won’t make much of anything. After a while, beneficial changes from the experiment petered out. The fact that malaria, with a billion fold more chances, gave a pattern very similar to the more modest studies on E. coli strongly suggests that that’s all Darwinism can do.
(The Edge of Evolution: The Search for the Limits of Darwinism
by Michael J. Behe :142)

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