M ore than a decade ago , the economist Erik Brynjolfsson made a prediction: AI would change everything. Humans began using tools millions of years ago. They cultivated grain and domesticated animals, and then developed written languages, iron tools, the printing press, gunpowder. Progress was slow and local until the mid-1700s, when modern society roared into being alongside machines and engines. Invention built on invention. Then, in recent decades, the pace of human progress slowed again.