Cold, Heat & Hormesis

There is an old idea, older than medicine, that what does not kill you can make you stronger. For most of human history this was lived rather than studied. We were cold and then we were warm. We were hungry and then we were fed. We carried, climbed, fasted, sweated, shivered, and survived — and the surviving made us. Then, in the span of three or four generations, we engineered nearly all of that away. We built a world of thermostats and lifts and refrigerators kept perpetually full, and we called it progress. It is progress, of a kind. But something in us has gone soft in the bargain, and the body that was forged by adversity now quietly deg…