Breakfast is the most important meal of the day—an aphorism first uttered by, of all people, Franz Kafka—but our ancestors were slow to get the wake-up call. Our Neolithic kin ground grains for a sort of porridge, and Roman soldiers started the day with another porridge called pulmentus. But for much of recorded history, only children and the weak ate three square meals a day. Adults were expected to get by on a midday dinner and a light supper.