Originally Posted By: Damocles
Why do people get old and die?

There is a simple reason: evolutionarily it did not matter if they die at older age.

The reason is not so simple: A species with no aging, in combination with other factors such as being not too low in the food chain, had a huge evolutionary advantage. It could grow much more rapidly. In fact it is absolutely not clear why evolution has not developed immortality of most higher species.

A plausible theory is that a non-aging species would not be able to evolutionary evolve further, and thus are stuck in a primitive state and in evolutionary niches.