We have lost sight of the belief systems and social agreements that animated and organized human groups in the lush and mysterious environment that gave rise to homo sapiens more than 100,000 years ago. Today, most of us are facing increasing estrangement from a natural world that is vanishing both in visible reality and in our memory. There are grounds for our unease. The increasing potential for social strife; shortages of food, water, and energy; loss of biodiversity; and catastrophic climate change tells us that civilization as we know it is unsustainable. In his quest for ideas on the sustainability of our human ecology, the author examines the prospects up to the year 2060 under the envelope of two mutually exclusive scenarios, referred to as “drifts.” One drift is what the author calls the Siege of Troy, in which the gap between the “haves” and the “havenots” becomes socially intolerable; and the other drift is Chimæra, in which attempts at making wealth and health available to everyone will accelerate global warming and the depletion of the biosphere.