1491_ New Revelations of the Americas Before Columbus - Charles C. Mann [151]
Nowadays Cahokia Creek, which flows from the north, and Canteen Creek, which flows from the east, join together at a point about a quarter mile northeast of Monks Mound. On its way to the Mississippi, the combined river then wanders, quite conveniently, within two hundred yards of the central plaza. Originally, though, the smaller Canteen Creek alone occupied that channel. Cahokia Creek drained into a lake to the northwest, then went straight to the Mississippi, bypassing Cahokia altogether. Sometime between 1100 and 1200 A.D., according to Woods’s as-yet unpublished research, Cahokia Creek split in two. One fork continued as before, but the second, larger fork dumped into Canteen Creek. The combined river provided much more water to the city—it was about seventy feet wide. And it also let woodcutters upstream send logs almost to Monks Mound. A natural inference, to Woods’s way of thinking, is that the city, in a major public works project, “intentionally diverted” Cahokia Creek.
In summer, heavy rains lash the Mississippi Valley. With the tree cover stripped from the uplands, rainfall would have sluiced faster and heavier into the creeks, increasing the chance of floods and mudslides. Because the now-combined Cahokia and Canteen Creeks carried much more water than had Canteen Creek alone, washouts would have spread more widely across the American Bottom than would have been the case if the rivers had been left alone. Beginning in about 1200 A.D., according to Woods, Cahokia’s maize fields repeatedly flooded, destroying the harvests.
The city’s problems were not unique. Cahokia’s rise coincided with the spread of maize throughout the eastern half of the United States. The Indians who adopted it were setting aside millennia of tradition in favor of a new technology. In the past, they had shaped the landscape mainly with fire; the ax came out only for garden plots of marshelder and little barley. As maize swept in, Indians burned and cleared thousands of acres of land, mainly in river valleys. As in Cahokia, floods and mudslides rewarded them. (How do archaeologists know this? They know it from sudden increases in river sedimentation coupled with the near disappearance of pollen from bottomland trees in those sediments.) Between about 1100 and 1300 A.D., cataclysms afflicted Indian settlements from the Hudson Valley to Florida.
Apparently the majority learned from mistakes; after this time, archaeologists don’t see this kind of widespread erosion, though they do see lots and lots of maize. A traveler in 1669 reported that six square miles of maize typically encircled Haudenosaunee villages. This estimate was very roughly corroborated two decades later by the Marquis de Denonville, governor of New France, who destroyed the annual harvest of four adjacent Haudenosaunee villages to deter future attacks. Denonville reported that he had burned 1.2 million bushels of maize—42,000 tons. Today, as I mentioned in Chapter 6, Oaxacan farmers typically plant roughly 1.25–2.5 acres to harvest a ton of landrace maize. If that relation held true in upstate New York—a big, but not ridiculous assumption—arithmetic suggests that the four villages, closely packed together, were surrounded by between eight and sixteen square miles of maize fields.
Between these fields was the forest, which Indians were subjecting to parallel changes. Sometime in the first millennium A.D., the Indians who had burned undergrowth to facilitate grazing began systematically replanting large belts of woodland, transforming them into orchards for fruit and mast (the general name for hickory nuts, beechnuts, acorns, butternuts, hazelnuts, pecans, walnuts, and chestnuts). Chestnut was especially popular—not the imported European chestnut roasted on Manhattan street corners in the