Collapse_ How Societies Choose to Fail or Succeed - Jared Diamond [12]
A rigorous, comprehensive, and quantitative application of this method was possible for the problem of deforestation-induced collapses on Pacific islands. Prehistoric Pacific peoples deforested their islands to varying degrees, ranging from only slight to complete deforestation, and with societal outcomes ranging from long-term persistence to complete collapses that left everybody dead. For 81 Pacific islands my colleague Barry Rolett and I graded the extent of deforestation on a numerical scale, and we also graded values of nine input variables (such as rainfall, isolation, and restoration of soil fertility) postulated to influence deforestation. By a statistical analysis we were able to calculate the relative strengths with which each input variable predisposed the outcome to deforestation. Another comparative experiment was possible in the North Atlantic, where medieval Vikings from Norway colonized six islands or land masses differing in suitability for agriculture, ease of trade contact with Norway, and other input variables, and also differing in outcome (from quick abandonment, to everybody dead after 500 years, to still thriving after 1,200 years). Still other comparisons are possible between societies from different parts of the world.
All of these comparisons rest on detailed information about individual societies, patiently accumulated by archaeologists, historians, and other scholars. At the end of this 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 detailed 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 belittle 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),