Aging is Neither a Failure nor an Achievement of Natural Selection
Juan Carlos Aledo,
Jose Maria Blanco.
In contraposition to the view of aging as a stochastic time-dependent accumulation
of damage, phenoptotic theories of aging postulate that senescence may provide
supra-individual advantages, and therefore it might have been promoted by natural
selection. We reason that although programmed aging theories are subjectively
appealing because they convey a cure for aging, they also raise a number of objections
that need to be dealt with, before we may be entitled to contemplate aging as an adaptive function evolved through natural
selection. As an alternative view, we present metabolism as an endless source of by-products and errors causing cellular
damage. Although this damage accumulation event is a spontaneous entropy-driven process, its kinetics can be genetically
and environmentally modulated, giving place to the wide range of lifespans we observe. Mild forms of damage may be
accumulating during a long enough period of time to allow reproduction before the fatal failure happens. Hence, aging
would be a stochastic process out of the reach of natural selection. However, those genetic pathways influencing the rate
of aging and consequently determining longevity may be targets of natural selection and may contribute to shaping the optimal
strategy according to the ecological context. In this sense, short- and long-lived organisms represent two extreme
strategies that, in terms of biological fitness, can perform equally well, each within its own niche.
Keywords: Aging, entropy, longevity, lifespan, metabolism, natural selection.
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