A mouse and a naked mole rat are about the same size, yet a mouse lives three years and a naked mole rat lives thirty. The secret lies in how fast their cells burn through the reserve of strength hidden inside their mitochondria.
Mitochondria are the power plants of the cell. Think of them as an hourglass: the grains of sand are damage to their DNA, and the supply of sand is the power reserve. As long as there is reserve left, the cell keeps working. Once the grains fill the glass, aging begins.
Scientists compared data from hundreds of species and found three rules. The bigger the animal, the larger its reserve. The tougher the mitochondrial DNA, the less often it breaks. And every extra degree of heat speeds up the buildup of defects. These three numbers explain why some species live longer than others.
It used to be unclear why different organs age at the same time. Now it makes sense: all cells share the same source of trouble, the mitochondria. If we learn to repair their DNA or slow the accumulation of damage, we could extend life. But for now, that is only a theory.
The naked mole-rat lives up to 30 years, even though its size matches that of a mouse, which lives 3 years. The secret lies in its low body temperature (about 32°C) and high GC% in mitochondrial DNA, which slows the accumulation of damage.
In H. G. Wells's The Time Machine, the Eloi and the Morlocks represent species with different lifespans, echoing the idea of tuning metabolic reserve through evolution.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.