Comparison between two paradigms about aging
Independent researcher, Naples, Italy
According to the current prevailing interpretations, the age-related fitness decline shown by many species in natural conditions, commonly defined as "aging", is an effect of:
1) the age-related decline of natural selection (mutation accumulation hypothesis);
2) a balance between possible advantages at a younger age and the disadvantages of fitness decline (antagonistic pleiotropy hypothesis);
3) limited "resources" - not better defined - which are used preferentially for reproduction and not for soma maintenance (disposable soma hypothesis).
This interpretation ("first paradigm") is challenged by a different paradigm ("second paradigm") that explains aging as an adaptive phenomenon and, in shorts, maintains:
1) Age-related decline of natural selection cannot explain age-related fitness decline;
2) There is no evidence for antagonistic pleiotropic genes or for limited "resources" causing age-related fitness decline;
3) The first paradigm predicts a direct relation between environmental mortality and the proportion of deaths caused by aging. The second paradigm predicts the opposite. Observational data falsify the prediction of the first paradigm and confirm that of the second.
4) The limitations in cell turnover determined by telomere-telomerase system are a plausible mechanism underlying senescence. This is hardly explainable by the first paradigm. On the contrary, this is compatible with the second paradigm and, in fact, the adaptive hypothesis predicts and requires the existence of specific mechanisms causing the fitness decline.
5) For the first paradigm aging is only a common term for many age-related different diseases: aging as a distinct entity does not exist and, in principle, cannot be mastered. On the contrary, for the second paradigm, all manifestations of aging have common mechanisms: aging is a distinct entity and, in principle, can be mastered.
The coexistence of the two paradigms or the formulation of intermediate hypotheses appears impossible. Therefore, a choice based on scientific data is indispensable.
Homo Sapiens Liberatus Workshop, Moscow State University, May 2010