It is an entropy issue... If your study leads you to discover a means to reverse entropy, you will have the key to, among other things, perpetual motion, things that wind up instead of run down, lifespans of Biblical length...
But until then, the second law of thermodynamics is intact..
Precisely!
The reversal of entropy is a trivial matter in simple systems. Consider a cuckoo clock: In the short scale of time, the clock is winding down, losing its energy in a high to low flow of entropy.
Then you come along and raise the weights again, restoring its energy. It's now ready for another bout of ticking and talking. But then we have to change our scale of what it means to recharge its components into this longer time span. For long-lived biological organisms, this is what happens. Each function that has an entropic tendency to decline will have an energy pump to recharge it, and other systems that recharge the recharging systems.
Left to its own devices, Mother Nature develops intricate interweaving mechanisms of mutual and ever-more-everlasting systems. Stable environments tend to acquire organisms perfectly adapted to them.
We don't have time to wait for Mother Nature to do this for us. If we want to extend the life-span of species Homo, we will have to take matters into our own nano-technological hands.
But the first step in that is understanding the structures, rules, and devices available to us in our quest. A patient and pious gardener, Gregor Mendel, started us on a journey to infinity, and beyond, (as has been aptly stated).