The mutations are like little nudges to throw you off the local maximum. And there's junk DNA where mutations can accumulate over time without being subject to

The mutations are like little nudges to throw you off the local maximum. And there's junk DNA where mutations can accumulate over time without being subject to selection before getting enabled at random to see if they give you an advantage. I think both the amount of junk DNA and the mutation rate are themselves subject to evolution for the best trade-off.