Why do we die?

There is a belief that death is the natural consequence of life. It is an easy conclusion to make: All living things die. No. There is nothing about being alive that necessitates death. The definition of life seems fuzzy, but let's look at the aspects that we humans are familiar with:

Interact with environment: eating, moving, breathing, seeing.
Self-maintenance: all the internal processes that keeps you alive.
Change: thinking, learning, forgetting, maturing, adapting.

None of these functions require us to die!

It is reproduction that necessitates death. If an organism reproduces but is not programmed to die, not only will it exponentially fill up the environment to take all available resources (in fact, mortal living things do this too), but it will do so while forcing newer, younger organisms to die from starvation. A reproducing organism that does not die will be taking resources away from its own children. This behavior goes against the drive of evolution - the organism will compete against its own offspring for survival, limiting the amount and frequency of genetic variation. It might work in an extraordinarily stable environment. However, if the organism has to adapt to frequent and drastic environmental changes, it would need to change. Unfortunately for life on Earth, there is no way for a species to change and adapt except by genetic variation. Until now.

Death (I'm not talking about death from accidents, diseases, or other artificial means) is an evolutionary trait, and may be one of the oldest. We can make it obsolete.