Life span in a species is an evolved trait: if longer lives provide a competitive advantage over shorter-lived peers, then a species will tend to become longer lived over time. We humans are long-lived for our size in comparison to other mammals, and the current thinking on that is that it may have to do with our intelligence and social nature - there is a selection effect based on advantages to survival provided by the presence of post-reproductive elders in a collaborative environment.
Salmon provide another example of the impact of evolution on aging, with their unusual aging process driven by levels of predation. The environment in which a species lives has a strong effect on life span. Here is an open access paper that considers another collection of fish species in which life spans evolved to adapt to differing mortality rates caused by environmental factors:
Early evolutionary theories of aging predict that populations which experience low extrinsic mortality evolve a retarded onset of senescence. [Here], we study annual fish of the genus Nothobranchius whose maximum lifespan is dictated by the duration of the water bodies they inhabit. Different populations of annual fish do not experience different strengths of extrinsic mortality throughout their life span, but are subject to differential timing (and predictability) of a sudden habitat cessation. In this respect, our study allows testing how aging evolves in natural environments when populations vary in the prospect of survival, but condition-dependent survival has a limited effect. We use 10 Nothobranchius populations from seasonal pools that differ in their duration to test how this parameter affects longevity and aging in two independent clades of these annual fishes.We found that replicated populations from a dry region showed markedly shorter captive lifespan than populations from a humid region. Shorter lifespan correlated with accelerated accumulation of lipofuscin (an established age marker) in both clades. Analysis of wild individuals confirmed that fish from drier habitats accumulate lipofuscin faster also under natural conditions. This indicates faster physiological deterioration in shorter-lived populations. [The] characterization of pairs of closely related species with different longevities should provide a powerful paradigm for the identification of genetic variations responsible for evolution of senescence in natural populations.
Link: http://dx.doi.org/10...1471-2148-13-77
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