Mutation versus Recipes already in the cookbook
Folks who argue against evolution typically argue against evolution is it was understood 50-100 years ago because the evolution some of us grew up with was wrong... and thus much easier to argue against.
Before we knew much about genetics it was assumed that extreme variation had to come from mutation. And mutation is a terrible source of favorable developments! ("Hopeful monsters"
What we did not appreciate was the incredible variety latent in a creature's DNA.
For instance, some people have twelve fingers that work just fine.
From one perspective, that is pretty much impossible. How the hell could each extra finger have blood vessels and nerves and bones and be recognized by the brain... the odds of that are... impossible. Imagine a workman mis-reading a number on a blueprint and adding an extra floor to a skyscraper, and magically all the wiring, bathrooms, windows... everything falls into place for that extra floor. The elevator even grows a new button for that floor! Impossible.
Unless DNA is not a blueprint at all, but rather something more like a recipe. Which it is.
There are a zillion developmental sub-routines for growing things like fingers. It is a bottom-up process. And it is not random for an extra finger to have all those blood vessels and such. Once a finger is "ordered" a zillion things happen and a whole 'nother human hand comes into being with extra ligaments in place to move the extra fingers, connected to bones mysteriously different to accommodate the extra ligaments, and so on.
That fully functioning 6-fingered hand is there, in your DNA. And it can "breed true." There was an isolated town in Italy that was famous for being mostly 6-fingered.
And the brain is aware of the extra finger because the brain doesn't start out with a plan for working ten fingers. It has a more general set of developmental routines for working fingers in general. Cut off a baby's thumb and it will quickly stop developing hand movements that depend on a thumb. Add an extra thumb and it will quickly start using two thumbs in ways that are efficient. The brain doesn't work with blueprints, but processes.
Yes, it is amazing that we can have twelve fingers, or ten or eight, and have them all work. But such is the immense diversity implicit in our genes.
We don't use most of it. No creature uses most of whatever it is their current genes make possible.
But the range of change possible from every possible combination of everybody's gene within a species is HUGE. Once critters have sex, combining different individual DNA into a new combination that never existed before, the potential goes wild.
Mutation plays a role, but a much, much, much smaller role than people once assumed to be the case.
The process is not like a monkey at a typewriter trying to type Hamlet. It is like a monkey at a computer with twelve kind of auto-finish and spell check and a process for stopping the thing whenever there is an error and starting over with a non-erroneous copy.
The difference between (infinity x infinity) versus (less than 26 x how ever many letters there are in Hamlet)
One clue to the incredible variety latent in a gene-pool was of great interest to Darwin—dog breeding.
A Saint Bernard and a Chihuahua are the same species. And that can be accomplished in only 100s of years.
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