Chapter XII. The Shifting Centers of Civilization. 251 Chapter XIII. The Climatic Hypothesis of Civilization 271 Appendix 297 Index 317 the widest audience of Civilization and Climate, has accepted the book on the reasonableness of its...
moreChapter XII. The Shifting Centers of Civilization. 251 Chapter XIII. The Climatic Hypothesis of Civilization 271 Appendix 297 Index 317 the widest audience of Civilization and Climate, has accepted the book on the reasonableness of its main hypothesis, and with an open mind as to future proof or disproof. Geologists, archaeologists, and those geographers who have had a geological training are the types of scientists who have found the hypothesis most convincing. This is because this volume employs methods of reasoning and lines of evidence such as are commonly used in geology, archaeology, and geography. The thesis is that certain climatic conditions are especially favorable to human progress, and that the greatest progress usually takes place in regions where those conditions are most closely approached. One of the main steps leading to this conclusion was the theory of pulsator y climatic changes first set forth in The Pulse of Asia. The evidence of such changes consists chiefly of ancient lakes and streams, old roads in deserts, dead vegetation, abandoned fields and irrigation systems, and especially ruins and other traces of man, which are really human fossils. Such evidence appeals to geologists, archaeologists, and geologically trained geographers. Anthropologists, economists, and historians, on the other hand, have been slow to believe that climatic changes have had much influence upon human history. They accept, indeed, the geologists' conclusion that previous to recorded history great climatic changes drove man this way and that, destroyed ancient types of culture, and either wiped whole races out of existence, or profoundly modified them, physically, mentally, xiv INTRODUCTION TO SECOND EDITION and socially. They apparently have no difficulty in accepting the geological evidence that among primitive men, as among plants and animals, climate has been one of the most powerful factors in determining the distribution and vigor of different types. But when it comes to the period of written history many historians, and some anthropologists and economists, no longer trust the geological methods of reasoning. Their opinions are more or less unconsciously molded by two conditions which do not apply to earlier times. First, there is a widespread idea that climatic uniformity is the normal condition ; second, the anthropologist, economist, and historian are in the habit of basing their conclusions either upon exact measurements and statistics, or upon written records. As to the assumed uniformity of climate, meteorologists do indeed find that so far as records are yet available, which means for scarcely a century, there are no certain indications of progressive climatic changes. But there is overwhelming evidence of pulsations which increase in magnitude and duration as the records become longer. In the same way the geological record continually discloses new evidence of climatic pulsations. Where one glacial period consisting of a single epoch was generally recognized half a century ago, at least six are now recognized. These date from all parts of geological time, and some have several epochs and subepochs. Moreover, the studies of Barrell, De Geer, Sayles, and many others are rapidly showing that during practically the whole of the earth's known history smaller climatic variations have occurred. Thus pulsations of climate are now almost universally regarded as characteristic of the vast periods covered by geology as well as of the short period covered by exact climatic records. The presumption is that similar pulsations of intermediate magnitude have been characteristic of the intervening historical period. This presumption is confirmed not only by the author's own work but by that of his critics. A good instance of this is other phases of the subject, is set forth in a new book entitled Climatic Changes: Their Nature and Causes, which appears ruins, vegetation, and so forth, it also fits a vast body of other facts as to human health, energy, progress, and civilization, which were not thought of when the hypothesis was framed. Since the first edition of this book was published there has V. INTRODUCTION TO SECOND EDITION and Pittsburgh. The way in which the variations depend upon climate is shown at length in the body of this book. Putting the matter in another way, the curves illustrate the fact that man's energy fluctuates from season to season and year to year in response to the weather. The two lower curves in Figure D show the fluctuations in health, that is, the inverted death rates, in Connecticut and Pennsylvania. Their general agreement with the curves of work is obvious, as is the way in which the worst health lags a little after the lowest efficiency because it takes some time for bad conditions of weather to result in death. The only reasonable interpretation of the four curves seems to be that chronologically, as well as geographically, climate is a determining factor. It has a great influence upon health, health influences energy, and energy has much to do with efficiency and progress. Other factors indeed enter into the matter, but it is doubtful whether any other variable factor is at once so widespread and so constantly effective as climate. A notable example of the effect of climate on health has recently been discovered by a Committee on the Atmosphere and Man appointed by the National Research Council of the United States. The appalling ravages of the influenza epidemic in 1918 have led many students to inquire why the severity of the disease varied so much from place to place. Pearl, Winslow, and others have compared the deaths from influenza and pneumonia during the epidemic with various environmental conditions such as the size of cities, the percentage of foreign-born, longitude, latitude, and the distance from Boston, where the epidemic began. They have also compared the epidemic with other conditions of health, such as the normal death rates from various diseases. By means of the precise and recently developed method of correlation coefficients, they have eliminated the effect of all except an}?^one of these factors. The only environmental factor that seems to have an effect is latitude, and that is barely large enough to be significant. Among the 11 to 20 days after +0.164 drO.116 21 to 30 days after +0.284 ±0.109 31 to 40 days after +0.606 ±0.075 to 50 days after +0.359 ±0.104 For the non-mathematical reader it may be more illuminating to divide the thirty-two cities, and four others for which the data are not quite so complete, into four equal groups on the basis of their average temperature during the thirty days preceding the local outbreak of influenza in 1918. On this basis we get the following preliminary results : xxviii INTRODUCTION TO SECOND EDITION Average tempera-Approximate ture for 30 days population before outbreak of in epidemic 1920 Nine warmest cities ... 71.4°F
