In The University of New Mexico's library, I was reading a book on the Anasazi, the Ancient Ones who populated Chaco Canyon, and disappeared sometime in the 13th Century, when a young woman appeared. The braid of her gleaming black hair fell behind a light-blue sari. Her lovely brown feet were bare. I asked her why. "I sweat a lot," she replied. "In winter?" "Yes. I always sweat."

Many anthropologists believe that the Anasazi left because of a long drought; but when she walked away, her moist feet traced a river tumbling through the sheer-walled canyons of the upper Ganges, clear down to the muddy banks of the Rio Grande.