Programmed versus non-programmed evolution of aging. What is the evidence?

The evolutionary meaning and basic molecular mechanisms involved in the determination of longevity remain an unresolved problem. Currently, different theories are on offer in response to these biological traits and to explain the enormous range of longevities observed in the animal kingdom. These theories may be grouped into those that defend non-programmed aging (non-PA) and those that propose the existence of programmed aging (PA). In the present article we examine many observational and experimental data from both the field and from the laboratory and sound reasoning accumulated in recent decades both compatible and not with PA and non-PA evolutionary theories of aging. These analyses are briefly summarized and discussed. Our conclusion is that most of the data favour programmed aging with a possible contribution of non-PA antagonist pleiotropy in various cases.