16 INTRODUCTION
Asia widespread poverty, want, and depression have been substituted for comparative competence, prosperity, and contentment. Disorder, wars, and migrations have arisen. Race has been caused to mix with race under new physical conditions, which have given rise to new habits and character. The impulse toward change and migration received in the vast arid regions of Central Asia has spread outward, and involved all Europe in the confusion of the Dark Ages. And more than this, the changes of climate which affected Central Asia were not confined to that region, apparently, but extended over a large part of the inhabited earth. Everywhere they were the most potent of geographic influences, working sometimes for progress and sometimes for destruction. Such in brief is the broad conclusion to which we are led by a study of Central Asia as an example of the influence of geography upon history. Before accepting it, it behooves us to examine with the closest scrutiny all the evidence in relation to climatic changes which may have been so momentous in the world's history.