ABSTRACT
Ageing is almost a right, imposed on 'nearly' all living creatures. The process of ageing is inherently complex and our poor understanding of how ageing occurs has produced a vast array of theories. The evolutionary theory of ageing is in essence based on the Darwinian law of natural selection and views ageing as the result of declining fitness, which is detrimental. Antagonistic pleiotropy proposes the existence of genes with dual antagonistic effects at the opposite ends of the spectrum of age. The somatic mutation theory postulates gradual accumulation of somatic mutations arising through genome instability during a single generation. Network theory of ageing acknowledges the contributions of the various mechanisms and suggests that they should be considered together to explain the process of ageing. Longevity is different from ageing. Based on the current theories of ageing, an important requirement for longevity is the need to combat stress. Most of the mutations that prolong life do so through strengthening stress resistance.
