Why on earth do we grow old?

Why do we age? What do we even mean by 'aging'? Do we die of an old age or not exactly? Are there any ways to slow down this inevitable process? Well, there must be some. You must have noticed by now that people age at different rates. That its sometimes difficult to guess a person's age. They might get grey hair at the age of 50, or the opposite may happen. They might still have this shiny and dark hair, be muscular, energetic and healthy.
The pace of aging can be altered by numerous strategies - some of them will appear in this brief book.