Somatic injuries should also consider in development of aging changes. In this aspect, Kirkwood predicted that: “aging is a result of accumulation of ‘faults’ at cellular and molecular level because of the limitation of maintenance and repair; the underlying driving force is damage. The genetic control of longevity comes through the regulation of the essential maintenance and repair processes that slow the build–up of faults” (Kirkwood, 2005). We summarize this prediction as “damage (fault)-accumulation theory”. This theory mainly relays on the importance of damage and repair/maintenance system in aging. However, since some terms are not specified, the conclusion of this theory is confusing. The term of “fault” in this assertion can be understood as a kind of “intrinsic damage”.
However, it is under speculation whether this “intrinsic damage” is referred to a change of a molecule/cell before repair or a change after repair. For example, in scar formation of skin burn injury, the wound of skin by burning is the primary damage before repair, and the scar is the change of skin after repair. These two changes of skin before repair and after repair are obviously different; thus they should be distinguished. The term of “faults” in this context is more possibly referred to primary damage before repair, since “they accumulate because of the limitation of repair/maintenance”. An unanswered question in this theory is: which kind of “faults” can be left unrepaired. In our view, if the faults are a kind of primary damage, they cannot remain unrepaired in a living organism. Primary damage is in fact a defect of a living structure such as molecule, cell, or tissue.
If the defect is not closed in time, the structure will lose its structural integrity and functionality, and the whole organism will fail rapidly. In another word, unrepaired faults will lead to a rapid death rather than aging of an organism. Hence, the concept of accumulation of “faults” is misleading, and the main idea of this theory is still in enigma for real time application.