Why we get old?

Someone ask: Why we get old?

Caveman say body like campfire that need constant tending. Tiny damage come from heat of living, sun, poison, bad cuts, and just normal use. Body can fix much of it, like tribe mending spear, but not forever. Some repair gets sloppy. Cells wear out, proteins tangle, DNA gets small scar marks, and cleanup crew gets slower. Parts that make energy also make smoke, and smoke hurts more over time. Evolution care most about helping body survive long enough to make babies, not keeping shell fresh forever, so repair system good, but not perfect. Science tribe still argue about one main cause, but all path point to same thing: repair loses race with damage. Cave wisdom: old age is not one broken bone, but many small cracks adding up.