The “Gap” theory of aging is based on two general postulates:

A “gap” between the self-maintenance and self-restoration processes, while the self-restoration process does not fit the needs of self-maintenance.
This “gap” evolved in evolution as a side effect of several evaluational developments increasing the level of the self-maintenance process and delay in the increasing level of self- restoration process (“unfinished evolution”) or alternatively, the “gap” was designed as part of creation.

More about “Gap” theory in the book:

Order Book from University of Toronto Book Store:  http://uoftbookstore.com/