EVOLUATIONARY BASIS OF AGEING
Ageing is a result of internal or external assaults that damage cells or organs so they can no longer function properly.
Ageing has a biological time table or internal biological clock
Waste accumulation theory
Mitochondrial damage theory
The human lifespan simply reflects the level of free radical damage that accumulates in cells when enough damage accumulates, cells cannot survive properly any more and they just simply give up.
Genetic mutations occur and accumulate with increasing age, causing cells to deteriorate and malfunction RNA molecule is highly susceptible to oxidative stress
It is well known that mitochondrial DNA is much more oxidized with age than nuclear DNA reactive oxygen species are continuously generated in the mitochondrial electron transport chain.
The immune system is programmed to decline over time which leads to an increased vulnerability to infections, disease and thus aging and death. It is well documented that the effectiveness of the immune system peaks at puberty and gradually declines there after with advance in age. eg. as one grows older antibodies lose their effectiveness.
· Once an organism has produced viable offspring its body is no longer needed. It then ages and dies.
· Certain genes may be useful in early life but detrimental in later life.
· Late acting genes have not been removed because they act after reproduction.
· Programmed theories maintain that ageing occurs due to intrinsic timing mechanisms and signals. eg. Genetic timers.
· Stochastic theories maintain that ageing occurs as the result of chance or accidental events. eg. free radical damage.