The programmed vs. non-programmed aging theory argument has existed since publication of Darwin's On the Origin of Species in 1859. Prior to Darwin there was no reason to suspect that life span had an origin that was different from that of any other organism characteristic that differed widely between species. Whatever caused a rat to have beady eyes and a long tail presumably also caused it to have a particular life span, which, like eyes and tail differed between species. Organisms were designed to have particular tails, eyes, and life spans.
The conflict between the observed enormous species-to-species variation in life span and Darwin's survival of the fittest concept was noticed immediately after publication of Origin. According to Darwin, all organisms were fighting to live longer and reproduce more and evolving design characteristics that helped them to live longer and reproduce more. In effect, evolutionary force was toward evolving immortality. Each increment of additional life span conveyed more opportunity to reproduce and propagate the possessor's design. Therefore each increment conveyed evolutionary benefit. Critics asked, if this was indeed true, why didn't organisms evolve longer and longer life spans and eventually become immortal and capable of living and reproducing indefinitely? If there was some fundamental limitation on life span or reproduction that could not be overcome by the evolution process, why didn't all organisms (at least similar ones) have the same life span?
Darwin responded that there must be some hidden benefit to a limited life span that compensated for its otherwise adverse nature. Organisms evolved a limited life span because doing so conveyed an offsetting benefit. This idea is central to most scientific theories of aging that attempt to explain the gross differences in life spans between different species.
Darwin could not explain how a limited life span benefited members of any particular species or why that benefit outweighed the disadvantage of a shorter life span. His argument is therefore circular: My theory says there must be some hidden compensating benefit so therefore there must be one. The theory is being used to predict the observation as opposed to observations resulting in a theory. Note that this same “explanation” could be used to “explain” any instance of an apparently adverse organism design characteristic.
At the time this was a reasonable position. There were perhaps thousands of life span observations that appeared to conflict with survival of the fittest. At the same time there were millions of observations of plant and animal design characteristics that clearly conformed to Darwin’s ideas in that they obviously aided the organism in surviving or reproducing. Darwin made and documented many of these observations himself. Darwin therefore had a reasonable expectation that eventually compensating benefits would be discovered for the small minority of apparently non-conforming observations.
Of course, what was a reasonable position in 1859 is not so reasonable today. By now, 150 years later, certainly we should have been able to definitively identify the compensating effects. And yet, in many cases, only Darwin’s hope for eventual discovery remains. In addition, other apparent conflicts with the survival of the fittest concept have surfaced. As happens so often in science, what once appeared to be so simple now appears to be more complicated.
Since 1962, two distinct schools of scientific thought have developed regarding the nature of evolutionary benefit. Traditionalists believe that evolved design characteristics must benefit the ability of individual organisms to survive longer (and therefore reproduce more) or simply to reproduce more, essentially Darwin's concept.
Believers in one of the newer alternative evolutionary mechanics theories believe that, in addition to individual benefit, an evolved design characteristic can benefit group survival or benefit the evolution process and that such benefits can offset individual disadvantage. The alternative theories, essentially adjustments to traditional theory, were developed in efforts to explain observed discrepancies with traditional mechanics other than life span.
A third group takes no position regarding which theory is correct but concedes that our certainty in the absolute truth of traditional evolutionary mechanics theory has declined because of multiple unresolved issues.
Although this may well seem like an obscure and highly academic argument that, after all, only affects a tiny fraction of bioscience observations, it essentially dictates theories of biological aging, which in turn have potentially major implications for the future of medicine. Believers in traditional evolutionary mechanics are logically forced to believe in non-programmed aging and ignore any contrary evidence. The others are led by empirical evidence toward programmed theories of aging.
Non-programmed theories of aging originated during an era when traditional evolutionary mechanics was a "given." Modern programmed theories of aging originated after the subsequent development of the alternative evolutionary mechanics theories. See Aging Theory Historical Timeline.
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