Rock Doc

My word processor is set up to deal with the errors I make when writing. The programmers who wrote the computer program knew I’d screw things up, so they built in corrective functions like spellcheck and the ability to simply backspace to delete typos. Those of us old enough to remember manual typewriters still sometimes marvel at the ease with which corrections in documents can now be made.

Mother Nature also has a built-in corrective function, one at work in organisms as simple as yeast and as complex as people.

“Each human cell experiences 10,000 to 100,000 injuries or lesions in its DNA pe...