1491 is not so much the story of a year, as of what that year stands for: the long-debated (and often-dismissed) question of what human civilization in the Americas was like before the Europeans crashed the party. The history books most Americans were (and still are) raised on describe the continents before Columbus as a vast, underused territory, sparsely populated by primitives whose cultures would inevitably bow before the advanced technologies of the Europeans. For decades, though, among the archaeologists, anthropologists, paleolinguists, and others whose discoveries Charles C. Mann brings together in 1491, different stories have been emerging. Among the revelations: the first Americans may not have come over the Bering land bridge around 12,000 B.C. but by boat along the Pacific coast 10 or even 20 thousand years earlier; the Americas were a far more urban, more populated, and more technologically advanced region than generally assumed; and the Indians, rather than living in static harmony with nature, radically engineered the landscape across the continents, to the point that even "timeless" natural features like the Amazon rainforest can be seen as products of human intervention. Mann is well aware that much of the history he relates is necessarily speculative, the product of pot-shard interpretation and precise scientific measurements that often end up being radically revised in later decades. But the most compelling of his eye-opening revisionist