McClintock recognized that genetic change is a cellular process, subject to regulation, and is not dependent on stochastic accidents. The idea of internally-generated, biologically regulated mutation has profound impacts for thinking about the process of evolution. Darwin himself acknowledged this point in later editions of Origin of Species, where he wrote about natural "sports" or "...variations which seem to us in our ignorance to arise spontaneously. It appears that I formerly underrated the frequency and value of these latter forms of variation, as leading to permanent modifications of structure independently of natural selection." (6th edition, Chapter XV, p. 395).
To see the real-world evolutionary importance of built-in biological mechanisms of genetic change, we have only to consider the post-WWII emergence of multiple antibiotic resistance in bacteria. This phenomenon represents the largest and best-documented evolutionary experiment in the molecular biology era. Interestingly, when antibiotic use began, we had a robust theory of how resistance would evolve by modification of existing cell components so that they were no longer antibiotic-sensitive. This theory was confirmed by laboratory experiments. Nonetheless, when the basis of naturally evolving multiple antibiotic resistance was determined, the experimentally-confirmed theory was wrong. Resistance resulted from the presence of new biochemical activities in the bacteria, encoded by new transmissible genetic systems that could accumulate additional DNA encoding these resistance activities (35).
"To see the real-world evolutionary importance of built-in biological mechanisms of genetic change, we have only to consider the post-WWII emergence of multiple antibiotic resistance in bacteria."
Makes you wonder how earlier life thrived with no knowledge and no ability to kill bacteria, yet man can lose millions of people with just one flu virus. And man has the ability to at least partially cure himself. Dinosaurs went millions of years, and had no intelligent ability to heal, and yet survived until wiped out by an outside source. It is almost like man is causing bacteria to "hurry" and find new pathways of survival. Which may actually lead to his demise.