On a memorable day in human history, February 12, 1809, two babies were born an ocean apart: Abraham Lincoln in a one-room Kentucky log cabin, Charles Darwin on an English country estate. It was a time of backward-seeming notions, when almost everyone still accepted the biblical account of creation as the literal truth and authoritarianism as the most natural and viable social order. But by the time both men died, the world had changed: ordinary people understood that life on earth was a story of continuous evolution, and the Civil War had proved that a democracy could fight for principles and endure. And with these signal insights much else had changed besides. Together, Darwin and Lincoln had become midwives to the spirit of a new world, a new kind of hope and faith.