Metabolic Reserve as the Hourglass of Life
In a zoo, a mouse and a naked mole rat can live side by side. Both are about the size of a palm, yet the mouse will grow old in three years, while the mole rat lives to thirty. The difference is not in how fast they chew or run, but in how quickly their cells burn through the safety margin stored in their mitochondria.
Mitochondria work like an hourglass.