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Why evolution could never solve aging?
Maybe aging is an essential mechanism to clear out the old and make way for the new like cells within a body?
Maybe every form of life is already close to the upper limit of life expectancy?
Maybe aging is in the nature of carbon based life and metabolism?
Maybe we genetically sacrifice our longevity to survive the stresses of competition.
Emerging Questions:
Is it that our metabolic processes are over-compensated for dominance in their sexual prime which prove detrimental for longevity?
Is it that genes leading to different lifespans are mixed indefinitely in nature that it was never possible to select for it?
Isn't an organism with a longer span of mating at an advantage?
My hypothesis:
In the absence of change in ones environment, or competitive stresses an organism would eventually adapt itself to survive longer.
If every organism is a product of evolution then there must of course be underlying mechanisms within itself to aid such an adaptive process.
Under the influence of adaptive pressure, it would encourage mutation or variations in order create successful variations and also increase the number of life-cycles and so reducing the lifespan.
Under the influence of competitive stress, the dominance would lead to reproductive success and not the span of mating during ones lifespan.
In the absence of change in ones environment leading to adaptive pressure, or competitive stresses from rivals to prove dominance. Species would evolve longer lifespans.
Just a Theory though! But it would predict that
Lifespans of living fossils which have undergone little change in time should be greater than their relatives which have recently evolved.
Life having evolved on geographically isolated places far from intense competitive pressures should have greater lifespans.
Living things higher up in the food-chain or with few natural enemies should have greater lifespans.
Life span in pair bonding species should be higher than tournament species.
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George Marshall II
At any rate, evolution and aging have, in my view, very little to do with the other. Natural selection no longer comes into play after child-bearing age. As much as I hate to personify it, evolution doesn't really care about old people. According to natural selection and the survival of a species it doesn't matter in the least if you survive after rearing your offspring.
It's against a population's best interest to prolong life past a certain point, most especially if child-bearing years are lengthened. The vast and overwhelming majority of animals on this planet will make offspring if age and health allow. The scenario that's painted by older creatures being able to continue to give birth is one of, eventually, a nearly infinite spring of life into a world of very finite resources, and eventually that little experiment would lead towards a stripping of natural resources, hunger, crowding, etc.
Aging and eventual death keeps the genetic pool fresh and ensures a homeostatic planet with balanced resources. Prolonged life or immortality eventually means an overburdened planet.
Anuraag Reddy
Paul Lillebo
The initial question of why debilitating aging occurs is still interesting. We know that during our lifetimes mutations occur in our DNA, both through copying errors whenever our cells divide, and through the ionizing effects from various sources of radiation. Preventing such mutations completely would have been metabolically costly and might not have been possible for complex organisms. As it is, there are many redundancies in our bodies that minimize the effect of mutations for many years, and these are certainly the result of evolution operating to give us the long length of life that we have. An interesting study is of "aging" in simpler systems like bacteria, which are very resistant to debilitating mutations, yet are highly adaptable to changing conditions. A puzzling paradox.
Brett Evill
That an organism's child-bearing age usually does end is manifest, and so universal in our experience that it seems natural. But that it does is an aspect, or perhaps a phase, of aging, the phenomenon we seek to explain.
George Marshall II
The simple fact is that the key to successful life on this planet is adaptability. Without the ability to adapt to changing conditions, an organism will eventually fall prey to the tumultuous environment that we all live in. If an organism doesn't eventually stop giving birth, then it continues to pass its own unchanging genetic structure on through the world, and evolution slows down immeasurably and becomes stunted.
Aging and eventual death are a part of this world, and they are the mechanisms that allow for growth in the species overall.
Brett Evill
Your second argument (like that of several explanations above) is that if there were no aging a catastrophe would eventually occur (or would have occurred), specifically, that if organisms did not age and die then evolution would slow down and life would fail to adapt. That's not a workable explanation, because evolution doesn't have any foresight. To explain why a biological phenomenon evolved you need to describe the mechanism by which organisms that had the causative mutation flourished and proliferated in competition with the rival alleles. Preventing a catastrophe in the future is not a way to survive and reproduce in the present.
To explain the evolution of senesence you have to explain a mechanism by which mutations that cause senescence proliferated when they were new and rare. Making room for a new generation is not such a mechanism, because most of the benefits to fall to the more numerous offspring of non-aging rivals. That isn't a competitive benefit to the mutants. Preventing a catastrophe to either the species, the ecosystem, or life itself isn't an explanation either, in the first place because saving the world, the region, or the species is not a competitive advantage to the mutants of their rivals, and in the second place because there is no mechanism for a possible catastrophe in the future to either prevent specific mutations or to save the lives and increase the progeny of specific mutants or to suppress their rivals in the present, Evolution does not provide protection against extinction, which is clear when you consider that most species that ever evolved have gone extinct.
Anuraag Reddy
I side with you, as evolution doesn't have a foresight, nothing evolves for the good of the species, it is individual fitness that matters and there must be a reason for the development of senescence and its efficacy as a trait.
Males can continue to mate until death, the child bearing/rearing hypothesis only applies to human females.
Oscar Fleury
Hey, which species are you talking about? Our own or all the others -- or are you putting all in the same basket?
As far as our species is concerned, do you mean that its perennity is granted by the sole production of offspring, as with animals? How about inventions, technology, science, infrastructures -- all those "children" born out of the human brain?
It seems to me you're in great need of some enlightenment -- which you might find in my reply to Christopher Henningsen in this discussion.
Comment on Brett Evil's reply to your comment:
Both of you (and most of the commentors in this discussion) are talking about limited child-bearing age as if natural selection had led to prevent the transmission of genes coding for exceptional longevity -- whereas in actual fact evolution has preserved the option of selecting these genes by not limiting the age of male fertility (as far as I know, for us humans)!