book I provide references to the many excellent books and papers on the ancient Maya and Anasazi, the modern Rwandans and Chinese, and the other past and present societies that I compare. Those individual studies constitute the indispensable database for my book. But there are additional conclusions that can be drawn from comparisons among those many societies, and that could not have been drawn from de tailed study of just a single society. For example, to understand the famous Maya collapse requires not only accurate knowledge of Maya history and the Maya environment; we can place the Maya in a broader context and gain further insights by comparing them with other societies that did or didn't collapse, and that resembled the Maya in some respects and differed from them in other respects. Those further insights require the comparative method.
I have belabored this necessity for both good individual studies and good comparisons, because scholars practicing one approach too often be little the contributions of the other approach. Specialists in the history of one society tend to dismiss comparisons as superficial, while those who compare tend to dismiss studies of single societies as hopelessly myopic and of limited value for understanding other societies. But we need both types of studies if we are to acquire reliable knowledge. In particular, it would be dangerous to generalize from one society, or even just to be confident about interpreting a single collapse. Only from the weight of evidence provided by a comparative study of many societies with different outcomes can one hope to reach convincing conclusions.
So that readers will have some advance idea where they are heading, here is how this book is organized. Its plan resembles a boa constrictor that has swallowed two very large sheep. That is, my discussions of the modern world and also of the past both consist of a disproportionately long account of one society, plus briefer accounts of four other societies.
We shall begin with the first large sheep. Part One comprises a single lengthy chapter (Chapter 1), on the environmental problems of southwest ern Montana, where Huls Farm and the ranches of my friends the Hirschys I to whom this book is dedicated) are located. Montana has the advantage of
being a modern First World society whose environmental and population problems are real but still relatively mild compared to those of most of the rest of the First World. Above all, I know many Montanans well, so that I can connect the policies of Montana society to the often-conflicting moti vations of individual people. From that familiar perspective of Montana, we can more easily imagine what was happening in the remote past societies that initially strike us as exotic, and where we can only guess what moti vated individual people.
Part Two begins with four briefer chapters on past societies that did collapse, arranged in a sequence of increasing complexity according to my five-point framework. Most of the past societies that I shall discuss in detail were small and peripherally located, and some were geographically bounded, or socially isolated, or in fragile environments. Lest the reader thereby be misled into concluding that they are poor models for familiar big modern societies, I should explain that I selected them for close consideration precisely because processes unfolded faster and reached more extreme out comes in such small societies, making them especially clear illustrations. It is not the case that large central societies trading with neighbors and located in robust environments didn't collapse in the past and can't collapse today. One of the past societies that I do discuss in detail, the Maya, had a popula tion of many millions or tens of millions, was located within one of the two most advanced cultural areas of the New World before European arrival (Mesoamerica), and traded with and was decisively influenced by other ad vanced societies in that area. I