We age because the world changes: http://www.fightaging.org/archives/2011/03/we-age-because-the-world-changes.php http://www.fightaging.org/archives/2011/03/we

We age because the world changes: http://www.fightaging.org/archives/2011/03/we-age-because-the-world-changes.php http://www.fightaging.org/archives/2011/03/we-age-because-th... But the degree to which aging is programmed - versus simply an unhappy stochastic decay due to diminishing selection pressures in later life - is a big and ongoing debate. Some species clearly have a lot of programming going on. For example, salmon age at a rate determined by the laziness of bears near to their particular rivers: http://www.fightaging.org/archives/2007/12/bear-consumption-and-the-appearance-of-of-programmed-aging.php http://www.fightaging.org/archives/2007/12/bear-consumption-... But there are equally good counter examples for many more species that suggest the situation is that evolution sets up to win the short race, front-loading as much as it can for early success, and then the selection pressure drops off after you had your shot at reproductive success. All that front-loading produces unpleasant later consequences as things fall apart - you're not set up for the long term. The adaptive immune system is a good example of this - it's a system that could never run as evolved for an indefinite period of time. It's always going to crash and burn at some point, and that's somewhat a consequence of how it's evolved to run extremely effectively right out of the gate in early life: http://www.fightaging.org/archives/2006/12/when-and-how-does-the-decay-of-your-immune-system.php http://www.fightaging.org/archives/2006/12/when-and-how-does... For more reading on this topic, you might look into antagonistic pleiotropy - the premature optimization of the evolved world: http://en.wikipedia.org/wiki/Antagonistic_pleiotropy_hypothesis http://en.wikipedia.org/wiki/Antagonistic_pleiotropy_hypothe...