DNA and the mechanisms of aging have been selectively engineered to maximize population growth and the saturation of an ecosystem by any and all species.
We are born, grow, procreate, raise offspring and die.
DNA depends on this cycle. If there were no natural selection of dominant (maximum ecosystem exploitation) species, then at some point, such a non-optimized species would most likely experience a calamitous shock, unable to adapt, move or cope, the result would be extinction.
Natural selection expects you to die. In fact, extending our age well past the viable range of procreation and raising offspring is counter-productive — as far as DNA is concerned. Old, you’re just a waste of resources.
We were designed (not really, but the end result might be thought of in this way) to die by age 50. By twenty-five, you would have produced offspring and would now be in the throes of raising them. By fifty, your done. In most cultures, by fifty, you’re already a grandparent having already passed on any wisdom to your children and potentially your grandchildren.
It’s like Logan’s Run but Carousel happens at 50. Your little red jewel glows until 49.364 and then — wink — out it goes. DNA is pretty much Logan’s run, but without the big bang at the end marking your “Ascension.”
Oh, sure, some will argue that elders impart existential experience and advocacy for the species. But this is just bollocks. The fact remains that throughout human existence this fifty-year maximum (on average) was pretty much the standard. Only in the last few hundred years have we breached this lifespan threshold.
And sure, there have been long-lived sages of old who wrote stuff down on tablets, scrolls, papyrus and whatnot. Information that has been tumbling along, building like a snowball to provide us the incredible advances we enjoy today.
But DNA does care about that stuff. It’s Eat-Pray-Love, but for all organisms.
Eat. Grow. Fuck. Die. That’s DNA for ya.