We die because certain parts in our body fail to work properly and our genes and cells start degrading.
Are we programmed to die?
Our chromosomes have a telomere region inside them. It protects the end of the chromosome from deterioration. This Telomere contains our genetic information. Cells multiply from one another, they get divided and when this happens the information contained in the telomere gets cut or sliced with each cell division. They keep getting trimmed and after a certain amount of time, years of growing up, this information in a cell is lost. Thus cells get old and stop functioning one by one.
Effects of Aging on the Body
Not only cells, each body part starts getting old with age. The heart begins to wear out after a couple of beats, joints start to creak, skin begins to flake, the brain shrinks with age, the spine curves, eyes and ears start to wear out and bones begin to crumble. All this effects out total health and humans can catch serious problems and diseases. But these days with an increase in scientific technology the lifespan of humans can be seen to age at a slow pace. Scientists believe that humans will also be able to live up till 140 years of age!