why do most organisms age while some specices have seemingly eluded evolution?
There are some interesting theories on this. Which ones have eluded evolution?
First, let me explain my views on death and ageing.
An organism is likely to die through some cause (disease, accident, being eaten or killed, starvation etc), but is unlikely to live forever when these things are present. It's like walking through a minefield - you might get a long way, but you can't keep going forever.
In fact, the pressure is to ignore how much food you need for the long walk in the future, and focus on avoid the mines now.
In the same way, there is pressure against repairing (at least perfectly. A cursory defence is useful) the cells against mutations and chemical damage. Why use energy to repair yourself to keep healthy and reproducing for 400 years, when that energy could be better used avoiding death from illness at 3, avoiding starvation at 14, having a healthy baby at 19?
To use energy for fixing those things would be useless if something else will kill you. So there is no way that the organisms with the capacity for longer lifespans will out-reproduce those who ignore it, under circumstances with accidental death and slow degeneration of age.
So, back to the question on why do some organisms age while others don't. It could be that those organisms are simple enough so that the maintenance of that organism is easy enough that it is achievable without too great a sacrifice. After all, it is easy to keep my desk clean from dust (being a simple structure), but the entire house, with all the complicated devices and fine areas to clean would be very hard to clean indeed, even with extra people at my disposal. So, the simple body plan of a hydrazoan would be easy to repair against mutations, but the complicated mammalian body would be far harder, even with the extra energy available (which would be better spent on other things).
ABE: It may also be that the smaller bodies are more vulnerable. With a body of say 300 cells, one cell that goes haywire is actually a large threat so energy should be used to prevent cancer. In a body of trillions of cells, the bigger threats come not from one haywire cell inside, but a trillion angry cells outside (predator) or billion cells inside (disease).
Edited by Doddy, : Added extra stuff
"Der Mensch kann was er will; er kann aber nicht wollen was er will." (Man can do what he wills but he cannot will what he wills.) - Arthur Schopenhauer
"Science can destroy religion by ignoring it as well as by disproving its tenets. No one ever demonstrated, so far as I am aware, the non-existence of Zeus or Thor - but they have few followers now." - Arthur C. Clarke
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