The problem is that there are a variety of completely different genetic activities that are lumped into evolution. You mentioned creation of a totally new gene. This is typically quite slow. When a child inherits genes from its parents, it is not an simple inheritance. If the mother has two gene # 5s, say 5a and 5b, the child does not just inherit one or the other. These genes can cross and the child inherit part of 5a and part of 5b. Sometimes transcription errors occur and the child inherits a gene 5 that is too big or too small, or even some genes installed backwards. This "evolution" is quicker than the new gene evolution. Then there is the timing. If you look at dawn horse, eohippus I believe, and compare it to modern horses, most of the changes are due to timing changes. The gene does not have to be changed. Only the amount of time that the gene is active changes. This is a very fast change. Even in your lifetime, a gene can change its timing and cause cancer. These timing changes can be very small and very fast. This type of change is like your dimmer switch example. For Example, the 17 year cicadas can mutate into 13 year cicadas, probably by a timing change. The two groups would not interbreed except rarely because they hatch in different years.
Remember, that some animals remain very constant over millions of years. Gators and Crocs are a good example. Their type is so well adapted to their niche, that most changes are weeded out. When an environmental disaster occurs and many niches are now empty, then, many changes that would have been weeded out now survive. During these times, evolution seems to go into overdrive as other animals fill the empty niches. This is why the timing changes are so important.
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