In A.D. 10, Roman engineer Julius Sextus Frontinus said, “Inventions have long since reached their limit, and I see no hope for further developments.” We smile and shake our heads now, but for a thousand years, Frontinus looked like a pretty smart guy. Leap ahead a millennium, and it’s a different story. People have opened the throttle on the engines of ingenuity. How did humankind manage so many giant leaps?