When you think of automation, you probably think of the assembly line, a dramatic dance of robot arms with nary a human laborer in sight. But that’s child’s play. The grandest, most disruptive automation revolution has played out in agriculture. First with horses and plows, and eventually with burly combines—technologies that have made farming exponentially cheaper and more productive. Just consider that in 1790, farmers made up 90 percent of the US workforce. In 2012, it was 1.5 percent, yet America still eats.