They occur on an average ofperhaps once every 10 million duplications of a DNA molecule. That's fairly rare. But of course when you multiply this by the total number of base pairs in the human body you get a lot of mutations each duplication. But here is the problem. Since an allele resides at the same location on the genome, the odds that any alteration will occur at say a 1000 base pair is 1 in 10,000.
Some alleles require multiple substitutions.
I don't think this is enough time to produce the kind of variability we see. I cited last night. I noticed that your didn't mention the chromosome number problem. That seems to me to require even more time for just the right fusion or fission of a chromosome to occcur or the offspring will die.