The Humble Olm and the Free Radical Theory of Aging
You might recall that the olm (Proteus anguinus) is a type of small salamander that lives as long as we do. Here researchers point out that olm life span is inconvenient for some theories of aging: "Recent work on a small European cave salamander (Proteus anguinus) has revealed that it has exceptional longevity, yet it appears to have unexceptional defences against oxidative damage. This paper comes at the end of a string of other studies that are calling into question the free-radical damage theory of ageing. This theory rose to prominence in the 1990s as the dominant theory for why we age and die. Despite substantial correlative evidence to support it, studies in the last five years have raised doubts over its importance. In particular, these include studies of mice with the major antioxidant genes knocked out (both singly and in combination), which show the expected elevation in oxidative damage but no impact on lifespan. Combined, these findings raise fundamental questions over whether the free-radical damage theory remains useful for understanding the ageing process, and variation in lifespan and life histories." Yet there are still the studies demonstrating extended life span through targeting antioxidants to mitochondria, which imply that at least so far as those cellular structures are concerned, oxidative damage is very important. It may be that the olm, like naked mole rats, has mitochondria that are highly resistant to damage in comparison to other species.
All of this should tell you that aging is clearly linked to mitochondrial dysfunction. The reason why anti-oxidants do not extend life by much is because they do not do anything to increase the body's self-repair capability. They only mop up free-radicals.