Why aging is caused mostly by degredation and is only modulated differentially by physiological factors
I give him dap for standing up for his view but I'll bethttp://www.blogger.com/img/blank.gif my hands (my most important body parts) he's wrong. Aging must be due mostly to a cumulative degenerative process. The simple answer comes from analyzing something I am sure Michael hasn't factored into his analysis and that is the relative difference in the number of translation and transcription events (ie places where mutations can happen) that exists between a fly and a human being. When you are as short lived as a fly, with a short cycle of cell recycling it becomes easy to have physiological effects dominate the longevity of an individual if well controlled (the results Michael got by controlling diet) but over the longer term the organism still is subject to mutations that slowly build up and lead to the whole house of cards coming down. Humans churn a significantly larger number of cells over their vastly longer life time and diet modification has a smaller impact on the much broader effects of system mutations arising across the much larger set of tissues, it takes longer for those degenerative effects to lead to catastrophic failure (death) but even with controls in diet and exercise the gains that are achieved are a small fraction of the total life cycle of the average human (as we can see from many studies that have revealed the results of exercise and diet on life length) it helps but not that much, the systemic degradation from acquired mutations just dominates the process. Be those mutations ones that are resident in telomeres being shortened, or induced by reduced efficiency of mitochondrial energy production or build up of proteins in the brain and other critical organs...eventually they win system wide and kill the organism.
I think that as a modulating factor his idea does make sense, that a base line for the aging population is determined by non physiological factors...but then those give way in the super long term to the slow mutation factors...the induced mistakes, the build up of cruft, the influence of radiation...eventually it catches up and the whole system comes tumbling down. We know the chemistry of interaction is only probabilistically true...thus it is guaranteed that mistakes will happen, some of them will go on repaired and those will lead to events that effect the fitness of the individual...be it methylation of a key gene or some other effect that leads to the slow degradation of the individual.
A great analog for what is going on between these ideas can be had from recalling the relationship between classical newtonian mechanics and relativistic mechanics. In the regime of speeds << c newton is quite adequate...providing numbers accurate to several decimal points, enabling us to confidently use these (wrong) equations to send probes to the far hurtling moons of Jupiter, to land with exquisite accuracy. Yet...for higher speeds, Newton's mechanics fails spectacularly...in the particle accelerators relativistic adjustments are requires to ensure accurate results. Just as it was a subtle transition at a very high rate of speeds that revealed the dilation effects that modulate momentum, length and time in relative, so to are the steady effects of ever present mutation factors in different organisms going to differentially present based on their relative rates of cell turn over and cell mass over their observed average life times.
Here is a hypothesis....that anemone (or the fruitfly for that matter) if scaled to our mass equivalent would start visibly showing it's aging ways over a not too long time scale...also, by being under water they are protected from a major source of mutations that are muted with an exponential law with depth into the seas...conferring a protection by eliminating a major source of slow mutations that we are subject to continuously here at the surface, the sun.
"The result illustrate the rapid attenuation
of solar UV radiation underwater
even in the clear oceanic water of the
Maldive islands. "