All of these mistakes are harmful (frequently fatal) to those born with these permanent errors to their DNA. We are all carrying around part of this damaged information, like a book containing thousands of misspelled words and grammatical errors.
These errors are passed down by parents to their children. If every new generation has an increase in the number of genetic mistakes, there must have been fewer mistakes in the past. The farther back we go, the more perfect our DNA code must have been.
So as time goes on, more and more errors will accumulate within the human genome, indicating that humans could not have existed for millions of years, as there would be far more “spelling mistakes” (genetic diseases).
(Source: Dr. John C. Sanford – Genetic Entropy and the Mystery of the Genome 3rd edition)