forgetting, death, and extinction

Forgetting is part of learning on each level of  (some versions of) the Asa H hierarchy. (And similarly for other examples of machine learning.)  Death is forgetting at the level of the whole individual. (Further up the hierarchy if you will.)  Extinction is forgetting at the level of the whole species. So death and extinction are not bad.  (Though they may come too soon in some cases.)  How quickly forgetting should occur depends in part upon the size of the memory that is available and speed of memory access.