The image of lost civilizations is compelling: cities buried by drifting sands or tangled
jungle, ruin and desolation where once there were people and abundance. Surely few
persons can read such descriptions and not sense awe and mystery. Invariably we arc
spellbound, and want to know more. Who were these people and, particularly, what
happened to them? How could flourishing civilizations have existed in what are now
such devastated circumstances? Did the people degrade their environment, did the
climate change, or did civil conflict lead to collapse? Did foreign invaders put these
cities to an end? Or is there some mysterious, internal dynamic to the rise and fall of
civilizations? Some of us are so fascinated by these questions that we devote our lives
to studying them. Most people encounter the dilemma of fallen empires and devas-
tated cities in casual reading, or in a school course. The image is troublesome to all,
not only for the vast human endeavors that have mysteriously failed, but also for the
enduring implication of these failures.