A couple notes:
Downs is unlike the other defects you mentioned in that it severely impairs the patient while the various extra-sex-chromosome disorders vary from sterility through minor impairment to what basically amounts to behavioral differences.
Downs is unusual, though, in that most extra chromosomes make the fetus nonviable. As far as trisomy disorders go in general, Downs is unusually benign.
Plants are better known for increasing their -ploidy (number of sets of chromosomes) than the count of an individual chromosome. A triploid human, with three copies of every chromosome, would be hopelessly nonviable. Plants are different. Really different.
That said, my experiments in silico say that what matters most is the pressure from the utility function, more so than the rate of mutation.
So if some organism is in an environment where only a few mutations help, then evolution progresses slowly; and when most possible changes are improvements, then evolution progresses faster.
Both environments can happen even without any dynamic change to the rate of mutations themselves.
- Life reproduces; between imperfections in reproduction and environmental mutagenic factors, there is a certain amount of random mutations;
- The churn happens. Organisms compete for resources; winners reproduce, losers starve. Environment throws curveballs - spills, seasons, volcanos, radiation, oxygen, and a million different things. A lot of organisms are killed, some survive and reproduce. Now, mutations can make organisms better or worse at surviving the challenges. This is the asymmetry you're looking for, the driver of evolution. Helpful mutations propagate, unhelpful mutations die. Where "helpful" means, of course, "helpful locally, at a given moment".
Rinse and repeat. The randomness isn't the driver - it's just jitter preventing evolution from getting stuck in a local minimum. The life cycle of birth and death is what drives evolution, specifically because it depends on both how the organism is built, and on the environment.
There's a knack to optimizing the mutation rate. If you mutate too much, 99.9999% of offspring can't develop and in the end there's too little reproduction. If you don't mutate enough, you don't evolve. Evolution has already optimized this hyperparameter.
This suggests you have not tried writing a simulated evolution based optimiser.
They're quite easy to write, the hard part is what you mean by a "fitness function" (which doesn't matter for nature, it just is whatever it is).
Such algorithms are also more than fast enough — remember that for the first 3 billion years we only had single-celled life, and that can reproduce in 20 minutes, so we had potentially 79 trillion generations (edit because "78.84 trillion" would be overselling the precision) before the first multicellular life. You get good results faster than that.
The number of base pairs is also just a misleading statistic. For example: each of XXX, XXY, XYY, and Downs are found in around 0.1 of human births, each of which gets an extra copy of a chromosome. These specific changes may not be too good for us, but this kind of sudden massive increase is also found in some plants without negative repercussions.
> However, bioelectric might be a much much more straightforward and fast way of driving evolution instead of randomly mutating DNA.
I have no reason to expect bioelectric processes described in this article to be able to direct useful effects on the genome, for the same reasons I think it unlikely your own brain could by sheer willpower turn you into a werewolf.
Wrong layer of abstraction.