Imagine living in a world where we humans don’t age gradually: we do so in one leap every birthday. After being fed at your mother’s breast for a year, your first birthday brings a rapid doubling in size, the ability to move around on four (perhaps even two) legs, babbling a few words, wide open eyes that see everything clearly … all in a flash. The second birthday sees you suddenly walking and running unaided and making conversation. And so the process goes until a ripe old age. An ideal situation? I don’t think so.