The new new world

"It's hard to say what they were," Christoph Heiermann, a spokesman for the Archaeological Heritage Service and State Museum for Prehistory in Dresden, told Salon. "They were central locations for the people, certainly. Maybe they were market squares, and served for some kind of rites, but we don't know that. We don't even know who the people were. We have no written sources from that time. There must have been some central organization that was able to organize people to do that, but we don't know if they had a chief or a king or some sort of parliament."

Networks of massive man-made mounds were also one of the defining characteristics of a city-state called Cahokia, not far from present-day St. Louis. Cahokia was advanced enough in the period from 950 to 1250 A.D. to have at least 15,000 inhabitants ("comparable in size to London," Mann notes) and to build massive mound structures, including one called Monks Mound. "Its core is a slab of clay about 900 feet long, 650 feet wide, and more than 20 feet tall," Mann writes.

Further excavation and analysis may provide more answers about Cahokia and the many other historical riddles Mann explores, or it may not; uncertainty pervades all research in this general area, and Mann is wise enough not to run from the doubt. Instead, he weaves it through his portraits of groundbreaking researchers and theorists to turn their stories into mini-mysteries. That is, he makes you wait before you see how the volume of evidence stacks up, and often takes you first through alternative theories that turn out not to have had legs. This works because Mann has a knack for explaining complex ideas in crisp, clear language; he almost never lapses into the kind of geek-having-fun speak that can sometimes make science writing cloying.

Mann is especially good on the subject of Native American agriculture. In 2003, in a piece that was chosen for an annual collection of the best science writing, he presented the startling notion that the Amazon rain forest has for so long been so thoroughly -- and so skillfully -- manipulated by Amazonian Indians that it probably makes sense just to go ahead and call it a work of art. He covers that territory here as a well, making a persuasive case that our predecessors in the Americas used fire in far more creative ways than has been understood up to now. Soil scientists marvel at the existence of a very rich, dark soil in the Amazon called terra preta de Indio. This, it turns out, is largely man-made. The fruit trees that are so plentiful in the Amazon? Planted by man. According to a recent study cited by Mann, the Indians living in the lower Amazon were growing more than 138 crops as far back as 4,000 years ago. One Spanish expedition into the Amazon in the 1540s came across a settlement so large and developed, its homes and well-tended gardens lined the river for more than a hundred miles and hundreds of thousands of people showed up to greet the visiting foreigners.

The most remarkable accomplishment in the Americas may be the development of maize, which has since spread throughout the world. Mann details a dispute between different factions arguing over just how maize came into existence, but both sides agree that this development began more than 6,000 years ago in southern Mexico, probably in the highlands. Mann cites Nina Fedoroff, a geneticist at Pennsylvania State University, who wrote in 2003 that maize was "arguably man's first, and perhaps his greatest, feat of genetic engineering."

So corn, that great symbol of the American heartland, turns out to be an ingenious triumph of man over nature. What about the great herds of bison that European settlers found swarming over the Great Plains? Surely these had been there going back many millennia? Actually, no. Mann makes a persuasive case that North American Indians not only created the large grasslands that provided the bison's ideal habitat -- which foolish visiting Europeans assumed had been created naturally -- but they also kept the bison population regulated. It was only when the Indian population was decimated by wave after wave of epidemic in the years after the dirty, disease-ridden Europeans showed up that the bison herds propagated wildly. "Hernando De Soto's expedition staggered through the Southeast for four years in the early sixteenth century and saw hordes of people but apparently didn't see a single bison," Mann writes. "When Indians died, the shaggy creatures vastly extended both their range and numbers ... The massive, thundering herds were pathological, something that the land had not seen before and was unlikely to see again."

Next Page: America in 1542: "A beehive of people"

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