How to think about the scale of human history: "Arthur M. Schlesinger, Jr., one the United States' great historians, is less than two lifetimes removed from a world where the United States did not exist. Through Mr. Schlesinger, you're no more than three away yourself. That's how short the history of our nation really is. Not impressed? It's only two more life spans to William Shakespeare. Two more beyond that, and the only Europeans to see America are those who sailed from Greenland. You're ten lifetimes from the occupation of Damietta during the fifth crusade. Twenty from the founding of Great Zimbabwe and the Visigoth sack of Rome. Make it forty, and Theseus, king of Athens, is held captive on Crete by King Minos, the Olmecs are building the first cities in Mexico, and the New Kingdom collapses in Egypt."
