For the last 200 years, humans have grown taller, stronger and healthier. This progress has been fastest in the countries that gave rise to the Industrial Revolution, yet it has spread throughout the world, sparking a transformation that economists Robert Fogel and Dora Costa call techno-physio evolution, “a synergism between technological and physiological improvements that is biological, but not genetic, rapid, culturally transmitted, and not necessarily stable.”After thousands of years of ignorance and stagnation, a kind of miracle happened that radically transformed humanity’s relationship to the wider world. This explosion of wealth has been periodically interrupted by war and famine, yet it has never been fully undone. And though it has involved serious downsides, the prospect of returning to a primeval state strikes most of us as insane. Modern life can be exhausting and even demeaning. It is, however, preferable to spending most of one’s waking moments foraging and hunting in a desperate struggle for survival.