As engineers have long recognized, many simple devices do not age. They function reliably until a critical component fails, and the whole thing dies instantly. A windup toy works smoothly until a gear rusts or a spring breaks, and then it doesn’t work at all. But complex systems—power plants, say—have to survive and function despite having thousands of critical components. Engineers therefore design these machines with multiple layers of redundancy: with backup systems, and backup systems for the backup systems. The backups may not be as efficient as the first-line components, but they allow the machine to keep going even as damage accumulates. Gavrilov argues that, within the parameters established by our genes, that’s exactly how human beings appear to work.

An oldie but a goodie from the New Yorker: The Way We Age Now.