What Are The Reasons Behind Ageing?

There are three theories that scientists have come up with, that explain the process of ageing and why it takes place.  
The first theory concerns the loss of cells as a result of surcease in cell growth.  Moreover there are other irreplaceable parts of the body, the loss of which results in the process of ageing.  Firstly brain cells die in wide numbers and don't grow back which results in the decline of brain functioning, which is a definite sign of ageing.

A second theory was that of mutations and changes happening throughout the body.  A human body does not function at a later stage as smoothly as it originally does at a younger age.  Errors are conducted in many bodily functions, which is further aided by natural radiation.  

The third explanation for ageing is the unwanted accumulation of some chemicals in the body.  It was believed that only cell division could cause some vital substances to get replaced.  Since cell division stops, this could lead to a lack of desired substances and the excess of some unwanted ones.

The organic process of growing older and showing the effects of increasing age can be termed as ageing. In other words, ageing can be defined as the eventual and ultimate failure of maintenance.

It also became obvious that so many different maintenance mechanisms exist, and that these depend on very many genes and a substantial and considerable investment in metabolic resources. Many individual theories of ageing spin around the failure of a specified maintenance system, but as there are many of these; it is expected that most of the vital theories have some level of truth.

A broad explanation and interpretation of the different degenerative changes during senescence must therefore be adopted, with the major conclusion that ageing is multi causal. It is also obvious that the evolved design of many components of complex animals is mismatched and incompatible with indefinite survival. We can consequently conclude that this evolved design is essentially related to the fact of ageing. This in turn means that an ageing cannot be reversed and inverted, though it may be modulated, as, for instance, by calorie restriction.

In protected environments, many animals can reach their maximum life spans, and it is now very obvious and clear that their senescence, ageing, and the death have multiple causes.