It turns out that inheritance has surprisingly little influence on longevity. James Vaupel, of the Max Planck Institute for Demographic Research, in Rostock, Germany, notes that only 3 percent of how long you’ll live, compared with the average, is explained by your parents’ longevity; by contrast, up to 90 percent of how tall you are is explained by your parents’ height. Even genetically identical twins vary widely in life span: the typical gap is more than fifteen years. If our genes explain less than we imagined, the classical wear-and-tear model may explain more than we knew.

One wants to know whether, in the end, her troubles were physical or psychological. But it is a question as impossible to answer as whether a blush is physical or mental — or, for that matter, whether a person is. Everyone is both, inseparable even by a surgeon’s blade.

Death is the enemy. But the enemy has superior forces. Eventually, it wins.