"As an engineer, you should be capable of understanding the difference between DNA and a book. The kind of changes that evolution selects are incremental. Think in terms of incrementing or decrementing a parameter, rather than changing the spelling of a word."
As an engineer, I know that every engineering design has parameters, but not all designs have the same parameters, and you can't convert any design to any other design by simply varying the parameters. You can't take a Ford car design and simply adjust the parameters to get a Toyota. And you certainly can't take a toaster design and adjust the parameters to get an F-18 or the Brooklyn Bridge.
Adjusting the parameters is analogous to micro-evolution. Changing the design is analogous to macro-evolution.