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It's partly a matter of scale. Larger changes become exponentially (that one's for you, borodog) more difficult to achieve that miniscule changes, especially when multiple concurrent changes in structure or function are required.
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There is to much here that is based on poor assumptions.
1. Large changes can come from the accumlation of small changes. Much as i cannot run a amrathon in one step that does not prevent me from taking many steps to reach that destination.
2. More difficult =! impossible.
Flax genome undergoes rapid change. From the paper
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In one plant species, Linum usitatissimum (flax) rapid changes in the genome occur that are associated with the environment in which the plant is growing, and these nuclear DNA variants can be stably or unstably inherited. In addition, the magnitude of the variation that occurs in flax has enabled the phenomenon to be identified.
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Large scale, non fatal genomic changes are certainly possible within pants and bacteria.
3. Miltiple concurrent changes are not always required. Because a mutation can be nutral, or its disadvantages are not negative enough to immediately remove the new allel from the population there is the possiblity for a building block effect even if one mutation alone provides an immediate disadvantage.
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Also, in your example, all that changed was the frequency of already existing alleles. You'll need a more insightful example than that to convince anyone.
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My example was merely to refute NotReady's statement that Borodog's list of requirements for evolution is incomplete - this one here
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I don't think your premises establish this. You would need another one, somthing like - Some genetic differences produce advantageous survival characteristics in the phenotype.
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Differences in the phenotype do NOT have to be advantageous as long as there is not a 1:1 relationship. Thats all, merely a technical point.
Edit: i meant to say Differences in the phenotype do not have to be advantageous as long is there is not a 1:1 relationship in reproduction (ie each generation is 1 parent to one offspring).