Memory serves the purpose of remembrance. To forget is to erase your past existence. By not forgetting will you remember the past. Only then will you be able to face it and evolve. The mind stores memories of past actions and decisions which are the clues to future evolution. People evolve through memories they have gone through and remembered.
To evolve is to know your mistakes and change them. To not forget about mistakes is evolution in itself as people will be able to prevent them. However, history keeps repeating the same mistakes for thousands of years because people keep on forgetting. We tend to forget what occurred and are unable to evolve because of it. To remember is to evolve.