nwr writes:
Back to biology. Behe raises the issue of the flagellum, and says that neo-Darwinism does not explain it. Most of the response that I have seen have been of the form of empirical evidence that the kind of structure Behe says is irreducibly complex actually does arise. Well that's the same kind of question begging. The answer should have been in form of the details as to how the theory shows that this kind of irreducible complexity can arise.
The responses I've seen describe an array of organisms with flagellum-like structures that range from "no flagellum capability at all" all the way up to "a lot of flagellum capability", illustrating that flagella aren't the only structures of this class that are advantageous and that organisms with flagella-like structures that do not behave like flagella are not uncompetitive.
It is quite possible that the genetic innovation required for this cecal valve was already present in the population...
If it wasn't already present in the population then this is an example of evolution producing advantageous random mutations at an impossible rate. It would be very strong evidence that there are very significant processes at work of which we are yet unaware. Seems unlikely.
The article I read about this (
http://www.sciencedaily.com/...ases/2008/04/080417112433.htm) said that the daughter lizard population was genetically identical to the parent population, but if that were really true then the cecal valves would have to be due to environment. One would expect that at a minimum there would be allele frequency differences between parent and daughter populations, so I don't really trust that article. But anyway, one of the scientists is quoted saying, "These structures actually occur in less than 1 percent of all known species of scaled reptiles," so your surmise that the genes for cecal valves were already present in the lizards but unexpressed seems likely.
--Percy
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