Around 12,800 years ago, North America suffered a massive cataclysm of cometary bombardment, alternately burning and freezing much of the continent. Not much survived. But what of what came before? In his latest book, Before America, Graham Hancock provides a journalistic account of the latest research into the pre-Columbian history of the Americas - North and South. Hancock catalogues the academic back-and-forths, the controversies and intellectual battles, and the widening acceptance that...