This frontal lobe—the last part of the human brain to evolve, the slowest to mature, and the first to deteriorate in old age—is a time machine that allows each of us to vacate the present and experience the future before it happens. No other animal has a frontal lobe quite like ours, which is why we are the only animal that thinks about the future as we do. But if the story of the frontal lobe tells us how people conjure their imaginary tomorrows, it doesn’t tell us why.
