Aging is basically the build-up of error: error at the genetic level, error at the cellular level. Cells normally repair themselves; that's why you heal when you get a cut. But even the mechanism of repair eventually falls apart.

Quote

“Aging is basically the build-up of error: error at the genetic level, error at the cellular level. Cells normally repair themselves; that's why you heal when you get a cut. But even the mechanism of repair eventually falls apart.”