Convergent Evolution - Reasonable conclusion? or convenient excuse?

I don't. Let's help your picturing.Think of the times when you're trying to listen to something specific, but there's all kinds of background noise. The more background noise messages entering your brain, the harder it is to concentrate on what's important at the time.For every mammal, because of the specific way it operates in its environment, there will be an optimum position on the hearing frequency levels that's best for them, and also an optimum breadth of their range. An increase in the breadth of the range will only be selected for if the advantages of hearing the extra sounds outweighs the "background noise" disadvantages.Extending the breadth into higher frequencies could be an advantage for night flying hunters and swimming hunters in certain circumstances, but would be interference to those individuals of our own ancestors who mutated the characteristic, so it would have faced negative selection, rather than positive.If I'm not right about this, all mammals would have much broader hearing ranges than we actually do. Instead, natural selection has focused on the priorities of different creatures in different circumstances, and hearing is specialised, rather than just bringing in maximum noise to the brain, and giving us unnecessary headaches.

True. It doesn't model evolution at all. Each individual mutates randomly on one seventh of its genome in only 6 possible ways, and there's no selection, so no conservation. Run it on until there are a million individuals, and it would hit some individuals with the exact same genomes as the original 15 depicted, and other chance genetic "twins".Also, relationship to an ancestor more than seven generations back will probably be undetectable.Sooner or later, you get an organism AAAAAAA that bears no resemblance to ancestors ten generations back, but is a replica of the original!Using all 26 letters of the alphabet would seem to work much better, but organisms would still eventually change out of recognition to their ancestors if there was no conservative selection of traits going on.

Does anyone remember about 2 years ago when creationist/I.D.ist Randman spent an entire thread arguing that there wasn't enough convergent evolution for "Darwinism"?That argument went along the lines of "if it's possible for invertebrates to evolve into vertebrates once long ago, then they should've done it again by now".We should get Randman and Bob together so they can come up with a grand unified creationist theory of why naturalistic evolution didn't happen. "There is both too much and too little convergence for "Darwinism" to be right, doubly proving it wrong".