What processes cause aging?

I found both the oxidative and browning theories to be very thought provoking.  I became especially interested in the idea of oxidation and how breathing and metabolism was essential blamed for our aging and therefore death.  I find it ironic that we die without oxygen or food, although we die with it as well.  I suppose this could be related to water as well.  Not enough: you die from dehydration, too much: you die from drowning.  Although the difference in this situation is the quantity.  If you consume 'the right' amount of water throughout your life time you continue living whereas if you consume 'the right' amount of oxygen or food you are still in the process of dying because of it.

I also thought the idea of comparing the organism's size and life expectancy was intriguing.  I had always understood that there is a balance between progeny size and complexity.  For example bugs lay many eggs at a time, they aren't too complex(compared to humans), and they reach reproductive maturity relatively quickly.  With humans a single birth is considered normal, humans are fairly complex, and it takes a long time for human babies to reach maturity.  While this concept had previously been explained to me as a mechanism to maintain a relatively stable population size, I hadn't thought of it as the amount of time an organism could ward of the effects of oxidization and metabolism.