Ayurveda consists of Ashtanga where in Jara Chikitsa is one among it. Rejuvination therapy is also explained by modern science which deals with jara itself. Since nobody knows exactly why we age, there is no dearth of theories on the subject. Most of the theories fall in one out of two broad groups.
Those which consider aging to be the cumulative result of random cell damage which goes on through out life, and those which consider aging to be the inevitable result of our genetic programme. The two groups of theories are not mutually exclusive. Possibly aging is primarily a genetically determined process, the rate of which can be modulated by environmental factors with a potential for damaging or protecting cells. Although the process of aging may be primarily genetic, scientists are more interested in the factors which can damage or protect cells because understanding these factors may give us the means of atleast retarding the process. Now we shall
examine briefly the better known theories of aging.